A C S0103 Perioperative Considerations For Anesthesia


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A C S0103 Perioperative Considerations For Anesthesia

  1. 1. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 1 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA Steven B. Backman, MDCM, PhD, FRCPC, Richard M. Bondy, MDCM, Alain Deschamps, MD, PhD, Anne Moore, MD, and Thomas Schricker, MD, PhD Advancements in modern surgical care are complemented by associated with general or regional anesthesia (see below) alterations in anesthetic management to provide maximum should be discussed in an informative and reassuring manner; patient benefit. During the last two decades, anesthesia prac- a well-conducted preoperative anesthesia interview plays an tice has changed enormously—with the proliferation of airway important role in alleviating anxiety. devices; the routine employment of patient-controlled anal- The medications the patient is taking can have a substantial gesia; the wider popularity of regional anesthesia, including impact on anesthetic management. Generally, patients should thoracic epidural anesthesia and peripheral nerve blocks; the continue to take their regular medication up to the time development of computer-controlled devices for infusing of the operation. It is especially important not to abruptly short-acting drugs; the discovery and use of quickly reversible discontinue medications that may result in withdrawal or inhalational drugs, opiates, and muscle relaxants; the avail- rebound phenomena (e.g., beta blockers, alpha antagonists, ability of online monitoring of central nervous system (CNS) barbiturates, and opioids). With some medications (e.g., oral function; and the increased application of transesophageal hypoglycemics, insulin, and corticosteroids), perioperative echocardiography, to name but a few examples. Our aim dosage adjustments may be necessary [see 8:10 Endocrine in this chapter is to offer surgeons a current perspective on Problems]. Angiotensin-converting enzyme inhibitors have perioperative considerations for anesthesia to facilitate dia- been associated with intraoperative hypotension and may logue between the surgeon and the anesthesiologist and be withheld at the discretion of the anesthesiologist.3 Drugs thereby ensure optimum care for our patients. The primary that should be discontinued preoperatively include mono- focus is on the adult patient: the special issues concerning amine oxidase inhibitors (MAOIs) and oral anticoagulants pediatric anesthesia are beyond the scope of our review. In [see Table 1]. Many surgical patients are taking antiplatelet drugs. addition, the ensuing discussion is necessarily selective; more Careful consideration should be given to the withdrawal of comprehensive discussions may be found elsewhere.1,2 these agents in the perioperative period [see Table 1] because of the possibility that discontinuance may lead to an acute Perioperative Patient Management coronary syndrome. Patients with recently placed coronary artery drug-eluting stents (< 1 year) may be at particular risk, Preoperative medical evaluation is an essential component so elective surgery should be postponed.4 If surgery is neces- of preoperative assessment for anesthesia. Of particular sary, and patients are deemed to be at increased risk for importance to the anesthesiologist is any history of personal medication-related bleeding during surgery, the longer-acting or family problems with anesthesia. Information should be agents (e.g., aspirin, clopidogrel, and ticlopidine) can be sought concerning difficulty with airway management or replaced with nonsteroidal antiinflammatory drugs (NSAIDs) intubation, drug allergy, delayed awakening, significant post- that have shorter half-lives. Typically, these shorter-acting operative nausea and vomiting (PONV), unexpected hospital drugs are given for 10 days, stopped on the day of surgery, or intensive care unit (ICU) admission, and post–dural punc- and then restarted 6 hours after operation. Platelet transfu- ture headache (PDPH). Previous anesthetic records may be sion can be considered if there is a very high potential for requested. significant bleeding.5 The airway must be carefully examined to identify patients The increasing use of herbal and alternative medicines has at risk for difficult ventilation or intubation [see Special led to significant morbidity and mortality as a consequence Scenarios, Difficult Airway, below], with particular attention of unexpected interactions with traditional drugs. Because paid to teeth, caps, crowns, dentures, and bridges. Patients many patients fail to mention such agents as part of their must be informed about the risk of trauma associated with medication regimen during the preoperative assessment, it is intubation and airway management. Anesthetic options [see advisable to question all patients directly about their use. Choice of Anesthesia, below] should be discussed, including Particular attention should be given to Chinese herbal teas, the likelihood of postoperative ventilation and admission to which include organic compounds and toxic contaminants the hospital or ICU. When relevant, the possibility of blood that may produce renal fibrosis or failure, cholestasis, hepati- product administration should be raised [see 1:4 Bleeding and tis, and thrombocytopenia. Specific recommendations exist Transfusion], and the patient’s acceptance or refusal of trans- for the discontinuance of many of these agents [see Table 1]. fusion should be carefully documented. Postoperative pain Prophylactic administration of perioperative beta blockers management [see 1:6 Postoperative Pain] should be addressed, in patients with or at risk for atherosclerotic disease under- particularly when a major procedure is planned. The risks going noncardiac surgery is controversial and merits specific DOI 10.2310/7800.S01C03 11/08
  2. 2. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 2 Table 1 Recommendations for Preoperative Discontinuance of Drugs and Medicine68–81 Type of Agent Pharmacologic Effects Adverse Effects Discontinuance Recommendations Drug MAOIs Isocarboxazid Irreversible inhibition of Potentiation of sympathomimetic Elective surgery: discontinue at least Phenelzine monoamine oxidase amines, possible hypertensive crisis 2 wk in advance; consider potential Pargyline with the resultant May prolong and intensify effects of for suicidal tendency—mental Tranylcypromine increase in serotonin, other CNS depressants health specialist should be involved Selegiline norepinephrine, Severe idiopathic hyperpyrexic Emergency surgery: avoid meperidine; epinephrine, dopamine, reaction with meperidine and consider regional anesthesia and octamine possibly other narcotics neurotransmitters Potential catastrophic interaction with tricyclic antidepressants, characterized by high fever and excessive cerebral excitation and hypertension Oral Warfarin Inhibition of vitamin K– Bleeding Elective surgery: discontinue 5–7 days anticoagu- dependent clotting in advance; replace with heparin if lants factors II, VII, IX, X necessary Aspirin and Inhibition of May increase intraoperative and Primary hemostasis normalizes in NSAIDs thromboxane A2 postoperative bleeding but not 48 hr in healthy persons; platelet Aspirin 80% of platelets must be transfusion requirement activity fully recovered in 8–10 days Fenoprofen inhibited for therapeutic Perioperative hemorrhagic complica- Patients on long-term aspirin therapy Ibuprofen effect tions increase with increasing for coronary or cerebrovascular Sodium Susceptibility to aspirin half-life of drug pathology should not discontinue meclofenamate varies between patients drug in perioperative period unless Tolmetin hemorrhagic complications of Indomethacin procedure outweigh risk of acute Ketoprofen thrombotic event Diflunisal Naproxen Sulindac Piroxicam Antiplatelet Thienopyridines Inhibition of platelet Synergistic antithrombotic effect with Discontinue ticlopidine 2 wk in agents Ticlopidine aggregation aspirin advance; discontinue clopidogrel Clopidogrel Inhibition of platelet 7–10 days in advance ADP–induced amplifi- Patients with coronary artery stents cation may receive aspirin plus ticlopidine for prolonged period after angio- plasty; stopping therapy consider- ably increases risk of coronary thrombosis; elective surgery should be delayed for 1–3 mo Antiglycoprotein Competitive inhibition of Literature (mainly from cardiac Discontinue at least 12 hr in advance agents GPIIb/IIIa receptors to surgery) shows increased hemor- Transfuse platelets only if needed to Eptifibatide prevent platelet rhagic risk if surgery undertaken correct clinically significant bleeding Tirofiban aggregation < 12 hr after discontinuance of Abciximab Rapid onset of action abciximab Short half-lives Individual variability in recovery time Often combined with of platelet function aspirin and/or heparin Herbal Chaparral Used as an alternative Hepatotoxicity As soon as possible medicines anticancer agent This herbal agent should be considered as dangerous Coltsfoot Used as an antitussive and Carcinogenic As soon as possible demulcent agent Considered dangerous Comfrey Used as a general healing Hepatotoxicity, liver failure As soon as possible agent Considered dangerous Ephedra/ma Noncatecholamine Dose-dependent increase in HR and Discontinue at least 24 hr in advance huang sympathomimetic agent BP, with potential for serious (Ephedra with a1, b1, and b2 cardiac and CNS complications sinica) activity; both direct and Possible adverse drug reactions: indirect release of MAOIs (life-threatening hyperten- endogenous catechol- sion, hyperpyrexia, coma), oxytocin amines (hypertension), digoxin and volatile anesthetics (dysrhythmias), guanethedine (hypertension, tachycardia) 11/08
  3. 3. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 3 Table 1 Continued Type of Agent Pharmacologic Effects Adverse Effects Discontinuance Recommendations Drug Herbal Echinacea Immunostimulatory effect Hepatotoxicity Discontinue as far in advance as medicines (Echinacea Allergic potential possible in any patient with hepatic purpurea) dysfunction or surgery with possible hepatic blood flow compromise Feverfew May increase bleeding especially in At least 7 days patients already on anticlotting medications Garlic (Allium Irreversible dose- Increased bleeding may potentiate Discontinue at least 7 days in advance sativum) dependent inhibition of other platelet inhibitors platelet aggregation Germander Choleretic, antiseptic Hepatotoxicity As soon as possible properties Used in weight control Considered dangerous Ginkgo (Ginkgo Inhibition of platelet- Increased bleeding Discontinue at least 36 hr in advance biloba) activating factor May potentiate other platelet Modulation of neurotrans- inhibitors mitter receptor activity Ginger (Zingiber Potent inhibitor of Increased bleeding Discontinue at least 36 hr in advance officinale) thromboxane synthase May potentiate effects of other anticoagulants Ginseng (Panax Inhibition of platelet Prolonged PT and PTT Discontinue at least 7 days in advance ginseng) aggregation, possibly Hypoglycemia irreversibly Reduced anticoagulation effect of Antioxidant action warfarin Antihyperglycemic action Possible additive effect with other “Steroid hormone”–like stimulants, with resultant activity hypertension and tachycardia Goldenseal May worsen swelling and/or high BP At least 7 days Kava (Piper Dose-dependent potentia- Potentiation of sedative anesthetics, methysticum) tion of GABA- including barbiturates and inhibitory neurotrans- benzodiazepines mitter with sedative, Possible potentiation of ethanol anxiolytic, and effects antiepileptic effects Licorice Hypertension (Glycyrrhiza Hypokalemia glabra) Edema Contraindicated in chronic liver and renal insufficiency Lobelia Used as an antinausea and Respiratory depression, tachycardia, As soon as possible mild expectorant hypotension, hallucinations, coma, Considered dangerous death Sassafras Stimulant, antispasmodic Carcinogenic As soon as possible Considered dangerous Saw palmetto May interfere with other hormone At least 7 days therapies St. John’s wort Inhibits reuptake of Possible interaction with MAOIs Discontinue on day of surgery; abrupt (Hypericum serotonin, norepine- Evidence for reduced activity of withdrawal in physically dependent perforatum) phrine, and dopamine cyclosporine, warfarin, calcium patients may produce benzodiaz- by neurons Increases channel blockers, lidocaine, epine-like withdrawal syndrome metabolism of some midazolam, alfentanil, and NSAIDs P-450 isoforms Valerian Dose-dependent Possible potentiation of sedative Discontinue at least 24 hr in advance (Valeriana modulation of GABA anesthetics, including barbiturates officinalis) neurotransmitter and and benzodiazepines receptor function Vitamin E May increase bleeding, especially in patients taking anticlotting agents May affect thyroid function in otherwise healthy patients In doses greater than 400 IU per day, further increase in BP may be seen in already hypertensive patients Yohimbe Aphrodisiac, sexual Hypertension, tachycardia, paralysis, As soon as possible stimulant death Considered dangerous ADP = adenosine diphosphate; BP = blood pressure; CNS = central nervous system; GABA = b-aminobutyric acid; GP = glycoprotein; HR = heart rate; MAOIs = monoamine oxidase inhibitors; NSAIDs = nonsteroidal antiinflammatory drugs; PT = prothrombin time; PTT = partial thromboplastin time. 11/08
  4. 4. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 4 consideration. Although a subgroup of patients may benefit Table 3 Fasting Recommendations* to Reduce Risk of from such treatment with respect to decreased cardiac mor- Pulmonary Aspiration83 bidity, overall, an increased risk of death, stroke, and clini- Ingested Material Minimum Fasting Period† (hr) cally significant hypotension and bradycardia has been ‡ reported.6 As such, it is anticipated that guidelines regarding Clear liquids 2 Breast milk 4 the role for beta blockers in the perioperative setting will con- Infant formula 6 tinue to evolve.7 Nonhuman milk§¤ 6 Light meal|| 8 Inpatient versus Outpatient Surgery *These recommendations apply to healthy patients undergoing elective proce- dures; they are not intended for women in labor. Following the guidelines does An ever-increasing number of operations are performed on not guarantee complete gastric emptying. † These fasting periods apply to all ages. an ambulatory basis [see ECP:5 Patient Safety in Surgical Care: ‡ Examples of clear liquids include water, fruit juices without pulp, carbonated A Systems Approach]. Operations considered appropriate for beverages, clear tea, and black coffee. § an ambulatory setting are associated with minimal physiologic Because nonhuman milk is similar to solids in gastric emptying time, the amount ingested must be considered in determining the appropriate fasting trespass, low anesthetic complexity, and uncomplicated period. recovery.8,9 The design of the ambulatory facility may impose || A light meal typically consists of toast and clear liquids. Meals that include limitations on the types of operations or patients that can be fried or fatty foods or meat may prolong gastric emptying time. Both the amount and type of foods ingested must be considered in determining the considered for ambulatory surgery. Such limitations may be appropriate fasting period. secondary to availability of equipment, recovery room nursing expertise and access to consultants, and availability of ICU or hospital beds. Patients who are in class I or class II of the intraoperative and postoperative opioid requirements and American Society of Anesthesiologists (ASA) physical status accelerate patient discharge. Use of a laryngeal mask airway scale are ideally suited for ambulatory surgery; however, a rather than an endotracheal tube is ideal in the outpatient subset of ASA class III patients may be at increased risk for setting because lower doses of induction agent are required prolonged recovery and hospital admission [see Table 2]. to blunt the hypertension and tachycardia associated with its Premedication to produce anxiolysis, sedation, analgesia, insertion; in addition, it is associated with a decreased inci- amnesia, and reduction in PONV and aspiration may be dence of sore throat and does not require muscle paralysis for considered for patients undergoing outpatient procedures, insertion. On the other hand, a laryngeal mask airway may as it may for those undergoing inpatient procedures. Such not protect against aspiration.12,13 premedication should not delay discharge. Fasting guidelines The benefits of regional anesthesia [see Regional Anesthesia [see Table 3] and intraoperative monitoring standards for Techniques, below] may include decreases in the incidence of ambulatory surgery are identical to those for inpatient aspiration, nausea, dizziness, and disorientation. Spinal and procedures [see Patient Monitoring, below]. epidural anesthesia may be associated with headache (dural A number of currently used anesthetics (e.g., propofol, puncture) and backache. Compared with spinal anesthesia, sevoflurane, desflurane), narcotics (e.g., alfentanil, fentanyl, epidural anesthesia takes more time to perform, has a slower sufentanil, and remifentanil), and muscle relaxants (e.g., onset of action, and may not produce as profound a block; succinylcholine, atracurium, mivacurium, and rocuronium) however, the duration of an epidural block can readily be demonstrate rapid recovery profiles. Nitrous oxide also has extended intraoperatively or postoperatively if necessary. desirable pharmacokinetic properties, but it may be associ- Care should be exercised in choosing a local anesthetic for ated with increased PONV. Titration of anesthetics to indices neuraxial blockade: spinal lidocaine may be associated with of CNS activity (e.g., the bispectral index) may result in a transient radicular irritation, and bupivacaine may be decreased drug dosages, faster recovery from anesthesia, associated with prolonged motor block; narcotics may pro- and fewer complications.10,11 Multimodal analgesia (involving duce pruritus, urinary retention, nausea and vomiting, and the use of local anesthetics, ketamine, alpha2-adrenergic ago- respiratory depression. Various dosing regimens, including nists, beta blockers, acetaminophen, or NSAIDs) may reduce minidose spinal techniques, have been proposed as means of minimizing these side effects.14–17 Monitored anesthesia care [see Choice of Anesthesia, below] Table 2 Association between Preexisting Medical achieves minimal CNS depression, so the airway and sponta- Conditions and Adverse Outcomes82 neous ventilation are maintained and the patient is able Medical Associated Adverse Outcome to respond to verbal commands. Meticulous attention to Condition monitoring is required to guard against airway obstruction, Congestive heart 12% prolongation of postoperative stay arterial desaturation, and pulmonary aspiration. failure Hypertension Twofold increase in risk of intraoperative In the recovery room, the anesthetic plan is continued until cardiovascular events discharge. Shorter-acting narcotics and NSAIDs are admin- Asthma Fivefold increase in risk of postoperative istered for pain relief, and any of several agents may be given respiratory events for control of nausea and vomiting. Criteria for discharge Smoking Fourfold increase in risk of postoperative respiratory events from the recovery room have been established [see Table 4]. Obesity Fourfold increase in risk of intraoperative and Recovery of normal muscle strength and sensation (including postoperative respiratory events proprioception of the lower extremity, autonomic function, Reflux Eightfold increase in risk of intubation-related and ability to void) should be demonstrated after spinal or adverse events epidural anesthesia. Delays in discharge are usually the result 11/08
  5. 5. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 5 Table 4 Postanesthetic Discharge Scoring System definitive surgical treatment must not be unduly delayed by (PADSS)84 attempts to “get a line.” Category Score* Explanation Vital signs 2 Within 20% of preoperative value Choice of Anesthesia 1 Within 20 to 40% of preoperative Anesthesia may be classified into three broad categories: value 0 Within 40% of preoperative value (1) general anesthesia, (2) regional anesthesia, and (3) moni- tored anesthesia care. General anesthesia can be defined as a Activity, mental 2 Oriented and steady gait state of insensibility characterized by loss of consciousness, status 1 Oriented or steady gait 0 Neither amnesia, analgesia, and muscle relaxation. This state may be achieved either with a single anesthetic or, in a more balanced Pain, nausea, 2 Minimal fashion, with a combination of several drugs that specifically vomiting 1 Moderate 0 Severe induce hypnosis, analgesia, amnesia, and paralysis. There is, at present, no consensus as to which general Surgical bleeding 2 Minimal anesthetic regimen best preserves organ function. General 1 Moderate 0 Severe anesthesia is employed when contraindications to regional anesthesia are present or when regional anesthesia or moni- Intake/output 2 Oral fluid intake and voiding 1 Oral fluid intake or voiding tored anesthesia care fails to provide adequate intraoperative 0 Neither analgesia. In addition, a few situations specifically mandate general anesthesia and controlled ventilation: the need for *Total possible score is 10; patients scoring g9 are considered fit for discharge home. abdominal muscle paralysis, lung isolation, and hyperventila- tion; the presence of serious cardiorespiratory instability; and the lack of sufficient time to perform regional anesthesia. Alternatives to general anesthesia should be considered for of pain, PONV, hypotension, dizziness, unsteady gait, or lack patients who are susceptible to malignant hyperthermia of an escort.18 (MH), for those in whom intubation is likely to prove difficult or the risk of aspiration is high, and for those with pulmonary Elective versus Emergency Surgery compromise that may worsen after intubation and positive pressure ventilation. Surgical procedures performed on an emergency basis may Regional anesthesia is achieved by interfering with afferent range from relatively low priority (e.g., a previously cancelled or efferent neural signaling at the level either of the spinal case that was originally elective) to highly urgent (e.g., a cord (neuraxial blockade) or of the peripheral nerves. Neur- case of impending airway obstruction). For trauma, specific axial anesthesia (i.e., epidural or spinal administration of evaluation and resuscitation sequences have been established local anesthetics) is commonly employed as the sole anes- to facilitate patient management [see 7:1 Initial Management thetic technique for procedures involving the lower abdomen of Life-Threatening Trauma]. The urgency of the situation and the lower extremities; it also provides effective pain relief dictates how much time can be allotted to preoperative patient after intraperitoneal and intrathoracic procedures. Combin- assessment and optimization. When it is not possible to ing regional and general anesthesia has become increasingly communicate with the patient, information obtained from popular.19 Currently, some physicians are using neuraxial family members and paramedics may be crucial. Information blockade as the sole anesthetic technique for procedures such should be sought concerning allergies, current medications, as thoracotomy and coronary artery bypass grafting, which significant past medical illnesses, nihil per os (NPO) status, are traditionally thought to require general anesthesia and personal or family problems with anesthesia, and recent endotracheal intubation.20 ingestion of alcohol or drugs. Any factor that may complicate Neuraxial blockade has several advantages over general airway management should be noted (e.g., trauma to the anesthesia, including better dynamic pain control, shorter face or the neck, a beard, a short and thick neck, obesity, or duration of paralytic ileus, reduced risk of pulmonary a full stomach). When appropriate, blood samples should be complications, and decreased transfusion requirements; it is obtained as soon as possible for typing and cross-matching, also associated with a decreased incidence of renal failure as well as routine blood chemistry, complete blood count, and myocardial infarction [see 1:6 Postoperative Pain].21–24 and toxin screen. Arrangements for postoperative ICU Contrary to conventional thinking, however, the type of anes- monitoring, if appropriate, should be instituted early. thesia used (general or neuraxial) is not an independent risk Clear communication must be established between the factor for long-term cognitive dysfunction.25 Neuraxial block- surgical team and anesthesia personnel so that an appropriate ade is an essential component of multimodal rehabilitation anesthetic management plan can be formulated and any programs aimed at optimization of perioperative care and specialized equipment required can be mobilized in the oper- acceleration of recovery [see ECP:3 Perioperative Considerations ating room (OR). The induction of anesthesia may coincide for Anesthesia].26,27 with resuscitation. Accordingly, the surgical team must be For short, superficial procedures, a variety of peripheral immediately available to help with difficult intravenous nerve blocks may be considered.28 With procedures on the (IV) access, emergency tracheostomy, and cardiopulmonary upper or lower extremity, an IV regional (Bier) block with resuscitation. Patients in shock may not tolerate standard diluted lidocaine may be useful. Anesthesia of the upper anesthetics, which characteristically blunt sympathetic extremity and shoulder may be achieved with the brachial outflow. The anesthetic dose must be judiciously titrated, and plexus block. Anesthesia of the lower extremity may be 11/08
  6. 6. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 6 achieved by blocking the femoral, obturator, and lateral fem- are advocated by some as measures of hypnosis to guide the oral cutaneous nerves (knee surgery) or the ankle and popli- administration of anesthetics.32,33 However, their effectiveness teal sciatic nerves (foot surgery). Anesthesia of the thorax in preventing intraoperative awareness remains controversial, may be achieved with intercostal or intrapleural nerve blocks. particularly when anesthesia is maintained by inhalational Anesthesia of the abdomen may be achieved with celiac drugs.34 CNS function may also be assessed by measurement plexus and paravertebral blocks. Anesthesia of the head and of cerebral blood flow, using transcranial Doppler, jugular neck may be achieved by blocking the trigeminal, supraor- bulb venous oxygen saturation, and cerebral oximetry bital, supratrochlear, infraorbitral, and mental nerves and the monitoring techniques. Although there is growing clinical cervical plexus. Local infiltration of the operative site may experience with these noninvasive intraoperative neurologic provide intraoperative and postoperative analgesia. monitors, randomized, prospective, and adequately powered Unlike the data on neuraxial blockade, the data on studies to support and guide their use are currently lacking. peripheral nerve blockade neither support nor discourage its use as a substitute for general anesthesia. Generally, however, General Anesthesia Techniques we favor regional techniques when appropriate: such approaches maintain consciousness and spontaneous breath- An ever-expanding armamentarium of drugs is available ing while causing only minimal depression of the CNS and for premedication and for induction and maintenance of the cardiorespiratory systems, and they yield improved pain anesthesia. Selection of one agent over another is influenced control in the immediate postoperative period. by the patient’s baseline condition, procedure, local standard Monitored anesthesia care involves the use of IV drugs of practice, and predicted duration of hospitalization. to reduce anxiety, provide analgesia, and alleviate the dis- premedication comfort of immobilization. This approach may be combined with local infiltration analgesia provided by the surgeon.29 Preoperative medications are given primarily to decrease Monitored anesthesia care requires monitoring of vital signs anxiety, to reduce the incidence of nausea and vomiting, and the presence of an anesthesiologist who is prepared and to prevent aspiration. Other benefits include sedation, to convert to general anesthesia if necessary. Its benefits amnesia, analgesia, drying of oral secretions, and blunting of are substantially similar to those of regional anesthesia. These undesirable autonomic reflexes. benefits are lost when attempts are made to overcome surgi- Sedatives and Analgesics cal pain with excessive doses of sedatives and analgesics. Benzodiazepines produce anxiolysis, sedation, hypnosis, amnesia, and muscle relaxation; they do not produce analge- Patient Monitoring sia. They may be classified as short acting (midazolam), inter- Patient monitoring is central to the practice of anesthesia. mediate acting (lorazepam), or long acting (diazepam). A trained, experienced physician is the only truly indispens- Adverse effects [see Table 5] may be marked in debilitated able monitor; mechanical and electronic monitors, although patients. Their central effects may be antagonized with useful, are, at most, aids to vigilance. Wherever anesthesia is flumazenil. administered, the proper equipment for pulse oximetry, blood Muscarinic antagonists (e.g., scopolamine and atropine) pressure measurement, electrocardiography, and capnogra- were commonly administered at one time; this practice is not phy should be available. At each anesthesia workstation, as popular today. They produce, to varying degrees, sedation, equipment for measuring temperature, a peripheral nerve amnesia, lowered anesthetic requirements, diminished nausea stimulator, a stethoscope, and appropriate lighting must and vomiting, reduced oral secretions, and decreased gastric be immediately available. A spirometer must be available hydrogen ion secretion. They blunt the cardiac parasym- without undue delay. pathetic reflex responses that may occur during certain Additional monitoring may be indicated, depending on the procedures (e.g., ocular surgery, traction on the mesentery, patient’s health, the type of procedure to be performed, and and manipulation of the carotid body). Adverse effects include the characteristics of the practice setting. Cardiovascular monitoring, including measurement of systemic arterial, Table 5 Benzodiazepines: Doses and Duration of Action85 central venous, pulmonary arterial, and wedge pressures; cardiac output; and continuous arterial and mixed venous Dose (for Elimination Benzodiazepine Comments Sedation) Half-Life oximetry, is covered in detail elsewhere [see 8:3 Shock]. Additional information about the cardiovascular system may Midazolam 0.5–1.0 mg, 1.7–2.6 hr Respiratory repeated depression, be obtained by transesophageal echocardiography.30 Practice excessive guidelines for this technique have been developed.31 It may sedation, be particularly useful in patients who are undergoing valve hypotension, repair or who have persistent severe hypotension of unknown bradycardia, anticonvulsant etiology. activity The effects of anesthesia on the CNS may be assessed (withdrawal) by monitoring electroencephalographic (EEG) activity that is Lorazepam 0.25 mg, 11–22 hr See midazolam either spontaneous (raw or processed) or evoked (e.g., repeated Venous somatosensory, auditory, or visual). Commercially available thrombosis devices that employ spectral analysis of spontaneous EEG Diazepam 2.0 mg, 20–50 hr See midazolam activity (e.g., bispectral index) are relatively easy to use and repeated and lorazepam 11/08
  7. 7. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 7 tachycardia, heat intolerance, inhibition of gastrointestinal pharmacologic treatment may be helpful [see Table 7]. H2 (GI) motility and micturition, and mydriasis. receptor antagonists (e.g., cimetidine, ranitidine, and famoti- Opioids are used when analgesia, in addition to sedation dine) and proton pump inhibitors (e.g., omeprazole) reduce and anxiolysis, is required. With morphine and meperidine, gastric acid secretion, thereby raising gastric pH without the time of onset of action and the peak effect are unpredict- affecting gastric volume or emptying time. Nonparticulate able. Synthetic opioids (e.g., fentanyl) have a more rapid antacids (e.g., sodium citrate) neutralize the acidity of gastric onset and a predictable time course, which make them contents. Metoclopramide promotes gastric emptying (by more suitable for premedication immediately before surgery. stimulating propulsive GI motility) and decreases reflux (by Adverse effects [see Table 6] can be reversed with full increasing the tone of the esophagogastric sphincter); it may (naloxone) or partial (nalbuphine) antagonists. also possess antiemetic properties. The alpha2-adrenergic agonists clonidine and dexmedeto- In all patients at risk for aspiration who require general midine are sympatholytic drugs that also exert sedative, anesthesia, a rapid sequence induction is traditionally consid- anxiolytic, and analgesic effects. They reduce intraoperative ered a standard of practice, although this has been recently anesthetic requirements, thus allowing faster recovery, and questioned.37 A rapid sequence induction is achieved through attenuate sympathetic activation secondary to intubation adequate preoxygenation, administration of drugs to produce and surgery, thus improving intraoperative hemodynamic rapid loss of consciousness and paralysis, and exertion of stability. Major drawbacks are hypotension and bradycardia; pressure on the cricoid cartilage (the Sellick maneuver) as rebound hypertensive crises may be precipitated by their loss of consciousness occurs to occlude the esophagus and so discontinuance.35,36 limit reflux of gastric contents into the pharynx. An alterna- tive is the so-called modified rapid sequence induction, which Prevention of Aspiration permits gentle mask ventilation during the application of Aspiration of gastric contents is an extremely serious cricoid pressure (thereby potentially reducing or abolishing complication that is associated with significant morbidity insufflation of gas into the stomach). The advantages of the and mortality. Fasting helps reduce the risk of this complica- modified approach are that there is less risk of hypoxia and tion [see Table 3]. When the likelihood of aspiration is high, more time to treat cardiovascular responses to induction Table 6 Opioids: Doses and Duration of Action86 Agent Relative Dose Time to Duration of Comments Induction Analgesic Peak Action Potency Induction or Maintenance Effect Maintenance Loading Morphine 1 1 mg/kg 0.05–0.2 mg/kg/hr 5–20 min 2–7 hr Respiratory depression, nausea, For perioperative vomiting, pruritus, constipa- analgesia: tion, urinary retention, biliary 0.1 mg/kg IV, spasm, neuroexcitation IM Pseizure, tolerance Cough suppression, relief of dyspnea-induced anxiety (common to all opioids) Histamine release, orthostatic hypotension, prolonged emergence Meperidine 0.1 For perioperative NA 2 hr (oral); 2–4 hr See morphine analgesia: 1 hr Orthostatic hypotension, 0.5–1.5 mg/kg (SC, myocardial depression, dry IV, IM, SC IM) mouth, mild tachycardia, mydriasis, histamine release Attenuates shivering; to be avoided with MAOIs Local anesthetic–like effect Remifentanil 250–300 1 µg/kg 0.25–0.4 µg/kg/min 3–5 min 5–10 min See morphine Awareness, bradycardia, muscle rigidity Ideal for infusion; fast recovery, no postoperative analgesia Alfentanil 7.5–25 50–300 µg/kg 1.25–8.0 µg/kg/min 1–2 min 10–15 min See morphine Awareness, bradycardia, muscle rigidity Fentanyl 75–125 5–30 µg/kg 0.25–0.5 µg/kg/min 5–15 min 30–60 min See morphine and alfentanil Sufentanil 525–625 2–20 µg/kg 0.05–0.1 µg/kg/min 3–5 min 20–45 min See morphine and alfentanil Ideal for prolonged infusion IM = intramuscular; IV = intravenous; MAOI = monoamine oxidase inhibitor; NA = not applicable; SC = subcutaneous. 11/08
  8. 8. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 8 Table 7 Pharmacologic Prevention of Aspiration87,88 Agent Dose Timing of Administration Comments before Operation H2 receptor antagonists 1–3 hr Hypotension, bradycardia, heart block, increased airway Cimetidine 300 mg, PO resistance, CNS dysfunction, reduced hepatic metabolism Ranitidine 50 mg IV of certain drugs Famotidine 20 mg IV Bradycardia Rare CNS dysfunction Sodium citrate 30 mL PO 20–30 min Increased gastric fluid volume Omeprazole 40 mg IV 40 min Possible alteration of GI drug absorption, hepatic metabolism Metoclopramide 10 mg IV 15–30 min Extrapyramidal reactions, agitation, restlessness (large doses); to be avoided with MAOIs, pheochromocytoma, bowel obstruction CNS = central nervous system; GI = gastrointestinal; IV = intravenous; MAOI = monoamine oxidase inhibitor; PO = oral. agents before intubation. Regardless of which technique is hyperreactive airway disease). Inhalation induction is also used, consideration should be given to emptying the stomach popular for ambulatory surgery when paralysis is not required. via an orogastric or nasogastric tube before induction. Sevoflurane is well suited for this application because it is not irritating on inhalation, as are most other volatile agents, and induction it produces rapid loss of consciousness. Sevoflurane has Induction of general anesthesia is achieved by administer- mostly replaced halothane as the agent of choice for inhala- ing drugs to produce unconsciousness. It is one of the most tion induction because it is less likely to cause dysrhythmias crucial and potentially dangerous moments for the patient and is not hepatotoxic. during general anesthesia because of the precipitous depres- sion of the cardiorespiratory systems and airway protective maintenance mechanisms. Various agents can be used for this purpose; the Balanced general anesthesia is produced with a variety of choice depends on the patient’s baseline medical condition drugs to maintain unconsciousness, prevent recall, and pro- and fasting status, the state of the airway, the surgical proce- vide analgesia. Various combinations of volatile and IV agents dure, and the expected length of the hospital stay. The agents may be employed to achieve these goals. The volatile agents most commonly employed for induction are propofol, sodium isoflurane, desflurane, and sevoflurane are commonly used thiopental, ketamine, and etomidate [see Table 8]. The opi- for maintenance [see Table 9]. Nitrous oxide is a strong anal- oids alfentanil, fentanyl, sufentanil, and remifentanil may also gesic and a weak anesthetic agent that possesses favorable be used for this purpose; they are associated with a very stable pharmacokinetic properties (fast onset, fast offset). Because hemodynamic profile during induction and surgery but only of its relatively high blood:gas partition coefficient compared invariably produce unconsciousness [see Table 6]. with nitrogen, nitrous oxide rapidly difuses into and expands Volatile agents [see Table 9] may be employed for induction air-filled cavities. Thus, it should be avoided in situations in of general anesthesia when maintenance of spontaneous ven- which expansion of such cavities is undesirable (e.g., pneu- tilation is of paramount importance (e.g., with a difficult mothorax, air embolism, bowel obstruction, and middle ear airway) or when bronchodilation is required (e.g., with severe surgery). It cannot be used as the sole anesthetic agent unless Table 8 Induction Agents: Doses and Duration of Action85 Agent Induction Time to Duration Comments Dose Peak of Action (mg/kg) Effect (s) (min) Propofol 1.0–2.5 90–100 5–10 Hypotension, apnea, antiemetic (low dose), sexual fantasies and hallucinations, convulsions Pseizures (rare), pain on injection, thrombophlebitis Thiopental 2.5–4.5 60 5–8 Hypotension, apnea, emergence delirium, prolonged somnolence, anaphylactoid reaction, injection pain, hyperalgesia Anticonvulsant effect Contraindicated with porphyria Ketamine 0.5–2 30 10–15 Analgesia; increased BP, HR, CO; lacrimation and salivation; bronchial dilatation; elevated ICP Dreaming, illusions, excitement Preservation of respiration (apnea possible with high doses) Etomidate 0.2–0.6 60 4–10 Minor effects on BP, HR, CO Adrenocortical suppression, injection pain and thrombophlebitis, myoclonus, nausea and vomiting BP = blood pressure; CO = cardiac output; HR = heart rate; ICP = intracranial pressure. 11/08
  9. 9. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 9 Table 9 Volatile Drugs89,90 hydrolysis of remifentanil, its administration may be labor † intensive, necessitating frequent administration of boluses Agent Oil/Gas MAC Blood/Gas Rank Coefficient* (atm) Coefficient‡ Order and constant vigilance. Its short half-life also limits its useful- (FA/FI)§ ness as an analgesic in the postoperative period and may even contribute to acute opioid intolerance. To help circumvent Halothane 224 0.0074 2.5 6 these problems, various dosing regimens have been proposed Enflurane 96.5 0.0168 1.8 5 in which the patient is switched from remifentanil to a Isoflurane 90.8 0.0115 1.4 4 longer-acting narcotic. Desflurane 18.7 0.060 0.45 2 neuromuscular blockade Sevoflurane 47.2 0.0236 0.65 3 The reversible paralysis produced by neuromuscular block- Nitrous 1.4 1.04 0.47 1 ade improves conditions for endotracheal intubation and oxide facilitates surgery. Neuromuscular blocking agents are classi- FA/FI = alveolar concentration of gas/inspired concentration; MAC = mini- fied as either depolarizing (succinylcholine) or nondepolariz- mum alveolar concentration to abolish purposeful movement in response to ing (pancuronium, rocuronium, vecuronium, atracurium, noxious stimulation in 50% of patients. *Lipid solubility correlates closely with anesthetic potency (Meyer-Overton cisatracurium, and mivacurium) and may be further differen- rule). tiated on the basis of chemical structure and duration of † Correlates closely with lipid solubility. action [see Table 10]. The blocking effect of nondepolarizing ‡ Relative affinity of an anesthetic for blood compared to gas at equilibrium. The larger the coefficient, the greater the affinity of the drug for blood and muscle relaxants is enhanced by volatile drugs, hypothermia, hence the greater the quantity of drug contained in the blood. acidosis, certain antibiotics, magnesium sulfate, and local § Rise in alveolar anesthetic concentration toward the inspired concentration is anesthetics and is reduced by phenytoin and carbamazepine. most rapid with the least soluble drugs and slowest with the most soluble. Patients with weakness secondary to neuromuscular disorders (e.g., myasthenia gravis and Eaton-Lambert syndrome) may it is administered in a hyperbaric chamber; it is usually be particularly sensitive to nondepolarizing muscle relax- administered with at least 30% oxygen to prevent hypoxia. ants. Nitrous oxide is commonly used in combination with other volatile agents. Potent volatile agents can trigger malignant emergence hyperthermia in susceptible patients. General anesthesia is terminated by cessation of drug The IV drugs currently used to maintain general anesthesia, administration, reversal of muscle paralysis, and extubation whether partially or entirely, feature a short, context- (or removal of an upper airway device). During this poten- sensitive elimination half-life; thus, pharmacologically signifi- tially dangerous period, close scrutiny of the patient is essen- cant drug accumulation during prolonged infusion is avoided. tial, and all OR personnel must coordinate their efforts to Such agents (including propofol, midazolam, sufentanil, help ensure a smooth and safe emergence from general anes- and remifentanil) are typically administered via computer- thesia. In this phase, patients may demonstrate hemodynamic controlled infusion pumps that use population-based instability, retching and vomiting, respiratory compromise pharmacokinetic data to establish stable plasma (and CNS (including laryngospasm), and, occasionally, uncooperative effector site) concentrations. Because of the extremely rapid or aggressive behavior.38 Table 10 Neuromuscular Blocking Agents: Doses and Duration of Action91 Agent Dose Duration of Metabolism Elimination Comments (mg/kg) Action (min) Succinylcholine 0.7–2.5 5–10 Plasma cholinesterase Renal < 2%, Fasciculations, elevation of serum potassium, chloride hepatic 0% increased ICP, bradycardia, MH trigger; prolonged effect in presence of atypical pseudocholinesterase Pancuronium 0.04–0.1 60–120 Hepatic 10–20% Renal 85%, Muscarinic antagonist (vagolytic), prolonged hepatic 15% paralysis (long-term use) Rocuronium 0.6–1.2 35–75 None Renal < 10%, Minimal histamine release hepatic > 70% Vecuronium 0.08–0.1 45–90 Hepatic 30–40% Renal 40%, Prolonged paralysis (long-term use) hepatic 60% Atracurium 0.3–0.5 30–45 Hoffman elimination, Renal 10–40%, Histamine release; laudanosine metabolite (a nonspecific ester hepatic 0% CNS stimulant) hydrolysis Cisatracurium 0.15–0.2 40–75 Hoffman elimination Renal 16%, Negligible histamine release; laudanosine hepatic 0% metabolite Mivacurium 0.15–0.2 15–20 Plasma cholinesterase Renal < 5%, Histamine release; prolonged effect in presence hepatic 0% of atypical pseudocholinesterase CNS = central nervous system; ICP = intracranial pressure; MH = malignant hyperthermia. 11/08
  10. 10. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 10 Reversal of neuromuscular blockade is achieved by admin- the headrest used in the prone position.41 The relationship istering anticholinesterases such as neostigmine or edropho- between postoperative cognitive dysfunction (POCD) and nium. These drugs should be given in conjunction with a anesthesia per se remains unclear and may occur in patients muscarinic antagonist (atropine or glycopyrrolate) to block who receive general (intravenous or inhalational) or regional their unwanted parasympathomimetic side effects. Neostig- anesthesia. POCD does not seem to be associated with intra- mine is more potent than edrophonium in reversing profound operative hypoxemia, hypotension, or acid-base disturbances. neuromuscular blockade. It is imperative that paralysis be Certain procedures, such as cardiac and orthopedic surgery, sufficiently reversed before extubation to ensure that sponta- have been associated with this disorder, and a common neous respiration is adequate and that the airway can be etiology (air, particulate, or fat microemboli) is implicated. protected. Reversal can be clinically verified by confirming There is a growing appreciation that even with other types of the patient’s ability to lift the head for 5 seconds. Reversal can surgery, POCD can occur, with elderly patients (more than also be assessed by muscle contraction response to electrical 60 years) being at particular risk during the first week after nerve stimulation. the procedure. Presently, there is little evidence that POCD Causes of failure to emerge from anesthesia include persists longer than 6 months.42 residual neuromuscular blockade, a benzodiazepine or opioid overdose, the central anticholinergic syndrome, an intraop- Regional Anesthesia Techniques erative cerebrovascular accident, preexisting pathophysiologic conditions (e.g., CNS disorders, hepatic insufficiency, and Neuraxial (central) anesthesia techniques involve continu- drug or alcohol ingestion), electrolyte abnormalities, acidosis, ous or intermittent injection of drugs into the epidural or hypercarbia, hypoxia, hypothermia, and hypothyroidism. intrathecal space to produce sensory analgesia, motor block- As noted, the effects of narcotics and benzodiazepines can ade, and inhibition of sympathetic outflow. Peripheral nerve be reversed with naloxone and flumazenil, respectively. blockade involves inhibition of conduction in fibers of a single Physostigmine may be given to reverse the reduction in peripheral nerve or plexus (cervical, brachial, or lumbar) in consciousness level produced by general anesthetics. Electro- the periphery. Intravenous regional anesthesia involves IV lyte, glucose, blood urea nitrogen, and creatinine levels should administration of a local anesthetic into a tourniquet-occluded be measured; liver and thyroid function tests should be extremity. Perioperative pain control may be facilitated performed; and arterial blood gas values should be obtained. by administering local anesthetics, either infiltrated into the Patients should be normothermic. Unexplained failure wound or sprayed into the wound cavity. Procedures per- to emerge from general anesthesia warrants immediate formed solely under infiltration may be associated with patient consultation with a neurologist. dissatisfaction caused by intraoperative anxiety and pain.43,44 contraindications Risk and General Anesthesia Strong contraindications to regional (particularly neurax- Determining the risk(s) attributed solely to anesthesia is ial) anesthesia include patient refusal or inability to cooperate difficult because of the confounding variables of patient during the procedure, elevated intracranial pressure, antico- characteristics, concurrent medications, and the surgical agulation, vascular malformation or infection at the needle procedure itself, including context (e.g., elective versus emer- insertion site, severe hemodynamic instability, and sepsis. gency). Prospective, unbiased studies sufficiently powered to Preexisting neurologic disease is a relative contraindication. reveal the frequency of rare events are lacking, and reliance on self-reporting of negative outcomes likely results in an anticoagulation and bleeding risk underestimation of risk. Given these limitations, attempts Although hemorrhagic complications can occur after any have been made to define the risks associated with anesthesia, regional technique, bleeding associated with neuraxial block- based on extensive and critical literature reviews [see ade is the most serious possibility because of its devastating Table 11].39 Perioperative mortality associated with consequences. Spinal hematoma may occur as a result of anesthesia increases with age, ASA status, and emergency vascular trauma from placement of a needle or catheter into procedures. Factors contributing to anesthesia-related the subarachnoid or epidural space. Spinal hematoma may mortality include inadequate assessment, preparation and also occur spontaneously, even in the absence of antiplatelet resuscitation, inappropriate anesthetic technique, inadequate or anticoagulant therapy. The actual incidence of spinal cord perioperative monitoring, lack of supervision, and poor post- injury resulting from hemorrhagic complications is unknown; operative care. Morbidity ranges from major permanent the reported incidence is estimated to be less than 1 in disability to relatively minor events without long-term conse- 150,000 for epidural anesthesia and 1 in 200,000 for spinal quence. Peripheral nerve injury, although rare, may have seri- anesthesia [see Table 12].45 With such low incidences, it is ous disability. The etiology includes direct injury from nee- difficult to determine whether any increased risk can be dles, instruments, suturing, injection of toxic substances, and attributed to anticoagulant use [see Table 13] without data thermal insults. Less obvious but more frequent events involve from millions of patients, which are not currently available. mechanical factors such as nerve compression or stretch. Much of our clinical practice is based on small surveys and Ischemia associated with a low cardiac output state is often expert opinion. implicated.40 Great caution must be used during patient posi- tioning, with careful attention to proper padding. Loss of Antiplatelet Agents vision is a rare but catastrophic event that may be associated There is no universally accepted test that can guide with compression of the eye by a facemask or by padding of antiplatelet therapy. Antiplatelet agents can be divided into 11/08
  11. 11. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 11 Table 11 Predicted Incidence of Complications of Anesthesia39 Mortality and Morbidity Approximate Incidence Rate per 10,000 Remarks Population Total perioperative deaths 1:200 (elective surgery) 50 (within 30 days) 1:40 (emergency surgery) 250 x2 (60–79 yr) x5 (80–89 yr) x7 (> 90 yr) Death related to anesthesia 1:50,000 (anesthesia related) 0.2 1:100,000 (ASA physical status I and II) 0.1 Cardiac arrest 1:10,000–1:20,000 (general anesthesia) 0.5–1.0 Mortality ≈ 1:15,000–1:150,000 1:3,000 (local anesthesia) 3 1:1,500 (spinal: 25% fatal) 7 Myocardial reinfarction 1:20 (0–3 mo after myocardial infarction 500 1:40 (4–6 mo after myocardial infarction) 250 Respiratory complications Aspiration during general 1:3,000 3 x4 in emergencies anesthesia 1:60,000 (death) 0.16 x3 in obstetrics Difficult intubation 1:50 200 Failure to intubate 1:500 20 Obstetrics ≈ 1:250 Failure to intubate and 1:5,000 2 ventilate Postoperative cognitive 1:4 at 1 wk 2,500 Regional anesthesia dysfunction 1:10 at 3 mo 1,000 General anesthesia (> 60 yr) 1:100 permanent 100 Postoperative delirium 1:7 (general surgery) 1,400 x3 >75 yr Up to 1:2 for elderly fractures of neck 5,000 x3 if requiring intensive care or femur Drowsiness 1:2 5,000 Day surgery Dizziness 1:5 2,000 Day surgery Headache 1:5 2,000 Cerebrovascular accident 1:50 if previous stroke 200 46% mortality (CVA) 1:100 general surgery 100 60% mortality if previous CVA (≈ 1:700 in the nonsurgical population) Carotid endarterectomy (CVA 1:15 if symptomatic 700 + death) 1:25 if asymptomatic 400 Disabling CVA + death Awareness With pain 1:3,000 3 2/3 with neuromuscular blockade Without pain 1:300 30 1/3 without neuromuscular blockade Total intravenous 1:500 20 anesthesia 1:10,000 1 Anaphylaxis 1:10,000 1 Deafness “Idiopathic” (general 1:10,000 1 ≈ 1:1,000 cardiac surgery anesthesia) Transient after spinal 1:7 1,500 anesthesia Loss of vision 1:125,000 0.08 1:100 (cardiac surgery) 100 Pain ~1:3 (moderate) 3,000 After major surgery 1:10 (severe) 1,000 Day surgery 1:2 5,000 Postoperative nausea and 1:4 2,500 2/3 nausea and 1/3 vomiting vomiting Female:male 3:1 11/08
  12. 12. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 12 Table 11 Continued Mortality and Morbidity Approximate Incidence Rate per 10,000 Remarks Population Sore throat 1:2 (if tracheal tube) 5,000 1:5 (if laryngeal mask) 2,000 1:10 (if facemask only) 1,000 Dental damage Requiring intervention 1:5,000 2 All dental damage 1:100 100 All oral trauma after tracheal 1:20 500 intubation Peripheral nerve injury 1:300 ulnar neuropathy 30 General anesthesia 1:1,000 (other nerves) 10 Thrombophlebitis 1–2:20 (water-soluble drugs) 500–1,000 1:4 (propylene glycol based) 2,500 Arterial cannulation <1:100 (permanent) < 100 complication Pulmonary artery perforation 1:2,000 5 Arterial puncture (during central venous cannulation) Internal jugular vein 1:35 350 cannulation Subclavian vein cannulation 1:200 50 ASA = American Society of Anesthesiologists. four major classes: (1) aspirin and related cyclooxygenase during a 5-year period. LMWH should be stopped at least 24 inhibitors (NSAIDs); (2) ticlopidine and selective adenosine hours before regional blockade, and the first postoperative diphosphate antagonists; (3) direct thrombin inhibitors (e.g., dose should be given no sooner than 24 hours afterward.47 hirudin); and (4) glycoprotein IIb/IIIa inhibitors. Only with aspirin is there sufficient experience to suggest that it does complications not increase the risk of spinal hematoma when given at clini- Drug Toxicity cal dosages.46 Caution should, however, be exercised when Systemic toxic reactions to local anesthetics primarily aspirin is used in conjunction with other anticoagulants.47 involve the CNS and the cardiovascular system [see Table 14]. Oral Anticoagulants The initial symptoms are light-headedness and dizziness, followed by visual and auditory disturbances. Convulsions Therapeutic anticoagulation with warfarin is a contraindi- and respiratory arrest may ensue and necessitate treatment cation to regional anesthesia.48 If regional anesthesia is and resuscitation. planned, oral warfarin can be replaced with IV heparin (see The use of neuraxial analgesic adjuncts (e.g., opioids, below). clonidine, epinephrine, and neostigmine) decreases the dose Heparin of local anesthetic required, speeds recovery, and improves the quality of analgesia. The side effects of such adjuncts There does not seem to be an increased risk of spinal bleed- include respiratory depression (opiods), urinary retention ing in patients receiving subcutaneous low-dose (5,000 U) (opiods), tachycardia (epinephrine), hypotension (clonidine), unfractionated heparin [see 6:6 Venous Thromboembolism] if and nausea and vomiting (neostigmine, opioids). the interval between administration of the drug and initiation of the procedure is greater than 4 hours.49 Higher doses, Neurologic Complications however, are associated with increased risk. If neuraxial The incidence of neurologic complications ranges from 2 anesthesia or epidural catheter removal is planned, heparin in 10,000 to 12 in 10,000 with epidural anesthesia and from infusion must be discontinued for at least 6 hours, and 0.3 in 10,000 to 70 in 10,000 with spinal anesthesia.49,50 The the partial thromboplastin time should be measured. Recom- most common serious complication is neuropathy, followed mendations for standard heparin cannot be extrapolated to by cranial nerve palsy, epidural abscess, epidural hematoma, low-molecular-weight heparin (LMWH), because the bio- anterior spinal artery syndrome, and cranial subdural hema- logic actions of LMWH are different and the effects cannot toma [see Table 12]. Vigilance and routine neurologic testing be monitored by conventional coagulation measurements. of sensory and motor function are of paramount importance After the release of LMWH for general use in the United for early detection and treatment of these potentially disas- States in 1993, more than 40 spinal hematomas were reported trous complications. 11/08
  13. 13. © 2008 BC Decker Inc ACS Surgery: Principles and Practice 1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR ANESTHESIA — 13 Table 12 Predicted Incidence of Complications of Regional Anesthesia39 Complication Incidence Rate per 10,000 Remarks Population Paraplegia ≈ 1:100,000 0.1 Permanent nerve injury Spinal 1–3:10,000 1–3 Epidural 0.3–10:10,000 0.03–10 Peripheral nerve block ≈ 1:5,000 2 2% brachial plexus neuropraxia lasting > 3 mo Epidural hematoma ≈ 1:150,000 (epidural) 0.07 ≈ 1:1,000,000 (spontaneous) ≈ 1:14,000 (USA) ≈ 1:200,000 (spinal) 0.05 ≈ 1:2,250,000 (Europe) ≈ 1:10,000 (spontaneous) Epidural abscess 1:2,000–1:7,500 0.7–5.0 Transient neural complications 1:1,000–1:10,000 (epidural) 1–10 (epidural) 1:125–1:2,500 (spinal) 4-80 (spinal) Transient radicular irritation Up to 1:3 (heavy lidocaine and 3,000 (spinal) mepivacaine) Cardiac arrest ≈ 1:1,500 (spinal) 5 (spinal) ≈ 1:3,000 (local anesthesia) 3 (local anesthesia) ≈ 1:10,000 (epidural) 1 (epidural) ≈ 1:10,000 (regional blocks) 1 (regional) Post–dural puncture headache ≈ 1:100 100 80% following inadvertent dural tap ≈ 1:10 (day surgery) 1,000 Blood patch 70–100% Immediate success, but headaches recur in 30–50% Backache < 1 hr surgery ≈ 20% 2,000 GA = LA > 4 hr surgery ≈ 50% 5,000 Urinary dysfunction ≈ 1:50 200 Pneumothorax ≈ 1:20 (supraclavicular blocks) 500 Systemic LA toxicity ≈ 1:10,000 (epidural) 1 ≈ 1:1,500 (regional blocks) 7 Cerebral seizures ≈ 1:4,000 (intravenous regional 2.5 Axillary ≈ 1:1,000 anesthesia) ≈ 1:500 (brachial plexus) 20 Supraclavicular ≈ 1:125 Eye blocks Retrobulbar hemorrhage 1:250–1:20,000 0.5–40 Brainstem anesthesia ≈ 1:700 15 Globe perforation ≈ 1:10,000 1 Ptosis—transient after eye ≈ 1:2 at 24 hr 5,000 block ≈ 1:5 at 1 mo 2,000 Diplopia—transient after eye 8–70% 800–7,000 block GA = general anesthesia; LA = local anesthesia. Transient Neurologic Symptoms described after intrathecal use of all local anesthetics but The term transient neurologic symptoms (TNSs) refers to are most commonly noted after administration of lidocaine, backache with pain radiating into the buttocks or the lower in the ambulatory surgical setting, and with the patient in extremities after spinal anesthesia. It occurs in 4 to 33% of the lithotomy position during operation. Discomfort from patients, typically 12 to 36 hours after the resolution of spinal TNSs is self-limited and can be effectively treated with anesthesia, and lasts for 2 to 3 days.51 TNSs have been NSAIDs. 11/08