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From: Henning L. Stokmo <helangen@gmail.com>
Date: 2009/2/12
Subject: Bambury tutorial on preop assessment
To: ucdgrad09@gmail.com

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Fwd: Bambury tutorial on preop assessment Fwd: Bambury tutorial on preop assessment Presentation Transcript

  • Preoperative care Ms. Niamh Bambury 05/02/09
  • Overview
    • Nutrition
    • Fluids and electrolytes
    • Anaesthetic review
    • Preoperative care
    • Analgesic ladder
    • Blood products
    • Antibiotic prophylaxis
    • Classification of wounds
  • Nutrition
    • Essential for
      • Wound healing
      • Immunological shield
      • Maintaining normal functioning of organs
  • The fasting state
    • After 12 hours of fasting the nutrients provided have been utilised.
      • Plasma insulin levels fall
      • Glucagon levels rise
    • Glycogen is stored in the liver, muscle
    • The liver converts glycogen into glucose
    • Muscle glycogen is broken down into lactate, exported to the liver and converted into glucose
  • The fasting state
    • After 24 hours glycogen stores are depleted and gluconeogenesis occurs mostly in the liver
    • Protein is broken into amino acids which undergo gng to form glucose
    • Fat is broken down into
      • Glycerol-glucose
      • Fatty acids-ketone bodies in the liver
  • Requirements in the healthy person
    • CHO and lipids are the mainstay of energy intake
    • 20-25kcal/kg/day
    • Vitamins
      • metabolic co-enzymes
      • co-factors in wound healing
      • antooxidants
  • Requirements in the healthy person
    • Trace elements
      • Eg zinc, copper, iron
      • cofactors for metabolic processes
      • components of body tissues
    • Nitrogen-approx 12g/day- normally provided by protein
  • Changes in calorific needs
    • Postoperatively-35kcal/kg/day
    • Increases 10% per degree increase in temperature
    • Sepsis- 40-45kcal/kg/day
    • Hypercatabolic states (burns, severe pancreatitis)-60kcal/kg
  • Assessing nutritional status
    • Body Weight and anthropometric techniques
    • Clinical
    • Laboratory techniques
  • Body Weight and anthropometric techniques
    • Body weight (loss of 10% of BW in preceding 6 months is an indicator of poor clinical outcome)
    • Triceps skin fold thickness(body fat mass)
    • Mid-arm muscle circumference(muscle mass)
    • Body mass index
      • BW in kg
      • Height in m2
      • Note these values can be inaccurate in the presence of oedema which occurs when there are changes in fluid balance in critically ill patients with fluid retention
  • Clinical assessment
    • Clinical history- weight change, dietary intake
    • Physical examination- muscle wasting, loss of subcutaneous fat, oedema, alopecia
    • Hand grip strength and respiratory function assess functional impairment which is associated with undernourishment.
  • Laboratory techniques
    • Serum albumin can be an indicator of nutritional status
    • However it is affected in the acute phase response and by inflammation
    • (where it falls rapidly and therefore is of little use in assessing nutrition)
    • U&E-Ca, Mg, PO4, Na, K
  • Feeding options
    • Oral
    • Enteral
    • Parenteral
  • Enteral Feeding
    • Requires GIT to be intact.
    • Can be given NG, NJ, PEG, PEJ
    • Indications
      • Dysphagia (esp for solid food)
      • Major trauma/Surgery- when fasting will be prolonged
      • IBD(Short gut syndrome,Crohn’s,Pancreatitis)
      • Distal low output enterocutaneous fistulae
      • Oesophagogastric surgery.
  • Enteral feeding
    • Monitoring of patients on enteral feeding
      • Clinical assessment
      • Daily weights
      • Fluid balance
      • Twice weekly electrolytes and trace elements
  • Enteral Feeding
    • Complications
      • Malposition of the tube itself
      • Aspiration
      • Fistula formation
      • Peritonitis
      • Tube blockage
      • Feed intolerance
      • Hyperglycaemia
      • Enteric infection
  • Parenteral Feeding
    • Definition; the delivery of essential nutritional requirements intravenously usually through a central venous catheter or PICC.
    • Used in intestinal failure where there is an inability of the GIT to absorb nutrients.
  • Parenteral Feeding
    • Indications
      • Proximal intestinal fistulae
      • Massive intestinal resecton especially <100cm of bowel left.
      • Severe pancreatitis
      • Prolonged ileus
  • Parenteral Feeding
    • Contents of TPN
      • >50% CHO
      • 40% fat emulsions
      • 1-2g/kg of fat/day
      • H2O 35ml/kg/day
      • Electrolytes-Na, K, Cl, Ca, Mg, PO4
      • Nitrogen
      • Vitamins ADEK B&C
  • Parenteral Feeding
    • Monitoring patients on TPN
      • Weight
      • U&Es, FBC, LFTs
      • Glucose
      • Temperature and Vitals(signs of sepsis)
      • Daily inspection of line
      • Trace elements
  • Parenteral Feeding
    • Complications
      • Line insertion
        • Sepsis
        • Pneumo/haemothorax
        • Arterial damage/thrombosis
        • Malposition of catheter
        • Cardiac arrythmias
  • Parenteral Feeding
    • Complications cont’d
      • Feed itself
        • Metabolic derangement
          • TPN jaundice
          • Hyper/Hypoglycaemia
        • Electrolyte disturbances
        • Vitamin/Trace element deficiency
  • Anaesthetic review
    • Suitability for surgery
      • Cardiac
      • Respiratory
    • Need for blood products
    • Type of anaesthetic GA versus spinal
    • Post op analgesia required
  • Assessment of cardiac function
    • Non-invasive
      • Chest x-ray
      • ECG
      • Echocardiography
      • Exercise test
    • Invasive
      • Coronary angiography
      • Thallium scanning
    • Assessment of cardiac function
    • Chest x-ray
      • indicated in the presence of cardiorespiratory symptoms or signs
    • Increased cardiac morbidity associated with
      • Cardiomegaly
      • Pulmonary oedema
    • Assessment of cardiac function
    • ECG
      • features of ischaemia or previous infarction(LBBB) may be present
    • Stress test-
      • if there are symptoms of IHD such as chest pain, SOB on exertion
    • 24-hour monitoring is useful in the detection and assessment of arrhythmias
  • Assessment of cardiac function
    • Echocardiography
      • Percutaneous
      • Transoesophageal(TOE)
    • Allows assessment of
      • Muscle mass
      • Ventricular function / ejection fraction
      • End-diastolic and end-systolic volumes
      • Valvular function
      • Segmental defects
  • Assessment of cardiac function
    • Nuclear medicine
      • Myocardial scintigraphy allows assessment of myocardial perfusion
      • Radiolabelled thallium is commonest isotope used
      • Areas of ischaemia or infarction appear as 'cold' spots
  • Assessing respiratory function
    • Lung function tests
      • predict the type and severity of lung disease
      • predict risk of complications and postoperative mortality
    • Arterial blood gases
    • Radiological investigations
      • chest x-ray
      • high-resolution thoracic CT
  • Lung Function Tests
    • Allow assessment of :
    • 1)Lung volumes
    • 2)Airway calibre
    • 3)Gas transfer
  • 1)Lung Volumes
    • Assessed with spirometry
    • Volumes measured include:
      • IC
      • IRV
      • TV
      • VC
      • FRC
      • RV
      • ERV
      • TLC
  • 2) Airway calibre
    • Assessed by Peak flow rates
    • Flow rates measured
      • FVC = Forced vital capacity
      • FEV1 = Forced expiratory volume in one second
    • Absolute values depend on height, weight, age, sex and race
    • FEV1 / FVC ratio is important
  • 2) Airway calibre
    • Lung function can be classified as:
      • Normal
      • Restrictive
      • Obstructive
    • Restrictive lung disease
      • FVC is reduced but FEV1/FVC is normal
    • Obstructive lung disease
      • FVC is normal or reduced and FEV1/FVC is reduced
  • 3)Gas transfer
    • Measured by arterial blood gases (ABG)
    • Also allow assessment of ventilation / perfusion mismatch
    • Important parameters to measure are
      • pH
      • Partial pressure of oxygen
      • Partial pressure of carbon dioxide
    • Pulse oximetry gives an indirect estimate of gas transfer
    • Technique is unreliable in the presence of other medical problems (e.g. anaemia)
  • Assessment of Renal function
    • Glomerular filtration rate is the gold standard test of renal function
      • Can be calculated by measuring creatinine clearance rate
      • Requires 24-hour urine collection
    • Serum creatinine allows a good estimate of renal function
      • may be inaccurate in patients with:
        • Obesity
        • Oedema
        • Pregnancy
        • Ascites
  • Anaesthetic preview
    • Medical co-morbidity increases the risks already associated with anaesthesia and surgery.
    • American Society of Anesthesiologists devised a grading system to accurately predict morbidity and mortality
  • 50 Moribound 5 25 Incapacitating disease which is always life-threatening 4 4.5 Severe systemic disease that limits activity but isn’t incapacitating 3 0.4 Mild systemic disease that does not limit activity 2 0.05 Healthy individual 1 Mortality Definition ASA Grade
  • ASA grading
    • Cardiovascular disease- Angina, Hypertension, Diabetes. Grade 2-3
    • Respiratory disease- COPD, Asthma. Grade 2-3
  • Planning postoperative pain management.
    • Postoperative pain management is essential for a number of reasons
      • Improved mobility
      • Patient comfort
      • Enhanced breathing
      • Prevention of gut immobility
  • Analgesic Ladder
    • Paracetamol
    • NSAIDS
    • Codeine phosphate
    • Morphine
    • Local anaesthesia
  • Analgesic ladder
    • Paracetamol
      • inhibits COX3
      • useful for simple operations
    • NSAIDS
      • used for moderate pain
      • as an adjuvant with opiates in severe pain
      • nonspecific COX inhibition leads to its side effects especially loss of platelet function renal haemostasis and gastric cytoprotection
  • Analgesic ladder
    • Codeine phosphate
      • does not have a significant respiratory effect
      • useful in intracranial surgery
  • Analgesic ladder
    • Stronger analgesics
    • IM morphine
    • PCA
      • IV or via epidural catheter
      • Patient controlled lock out time predetermined
    • Local analgesics
      • continuous epidural anaesthesia with opiates or local anaesthetics
    • Spinal opiates
  • Fluid and electrolytes
    • Managing fluids pre and postoperatively essential
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  • Fluid and electrolyte balance
    • Daily requirements
    • For the ‘average’ 70 Kg man
      • Total body water is 42 L (~60% of body weight)
      • 24L is in the intracellular and 14 L in the extracellular compartments
      • The plasma volume is 3 L
      • The extravascular volume is 11 L
    • Composition of crystalloids
    • Hartmann’s Solution
    • Normal Saline
    • Dextrose Saline
    • Sodium (mmol/l) 131 150 30
    • Chloride (mmol/l) 111 150 30
    • Potassium (mmol/l) 5 Nil Nil
    • Bicarbonate (mmol/l) 29 Nil Nil
    • Calcium (mmol/l) 2 Nil Nil
    • * Clinical history and observations – Pulse, blood pressure, skin turgor
    • * Urine output – oliguria < 0.5 ml/kg/hr
    • * CVP or pulmonary capillary wedge pressure
    • * Response of urine output or CVP to fluid challenge
    • * A fluid challenge should be regarded as a 200-250 ml bolus of colloid
    • * This should be administered as quickly as possible
    • * A response in the CVP or urine output should be seen within minutes
    • * The size and duration of the CVP response rather the actual values recorded is more important
  • Fluid replacement
    • 3 factors to consider
      • Maintenance requirements
      • Abnormal losses
      • Pre-existing deficits in fluids and electrolytes
  • Fluid replacement
    • Maintenance requirements
    • Adults require approx 30-40mls/kg/day
    • Children require considerably more
      • 0-10 kg -100 ml/kg
      • 10-20 kg -1000 ml + 50 ml/kg for each kg > 10
      • >20 kg -1500 ml + 25 ml/kg for each kg > 20
  • Fluid replacement
    • Daily requirements
      • Sodium and potassium requirements are approx 1mmol/kg/day
      • Note that there is always a loss of potassium from faeces and urine so patients with diarrhoea can rapidly become hypokalaemic
  • Insensible losses
    • Faeces approx 100 ml/ day
    • Lungs approx 400 ml/ day
    • Skin approx 600 ml/ day
    • Urine approx 1,500mls/day
  • Fluid replacement
    • Abnormal losses
      • Nasogastric aspirate-rich in Na and K
      • Vomit, diarrhoea
      • Stoma, drains, fistula etc
    • Pre-existing fluid and electrolyte deficit
      • Specific diseases- acute pancreatitis and SBO -massive consumption of electrolytes and fluid
  • Assessing Fluid balance
    • Vital signs-pulse,BP
    • Urine output
    • Dry mucosal surfaces
    • Skin turgor
    • Mental status
    • Capillary return
  • Composition of crystalloids
    • Hartmann’s Solution
      • Sodium 131 mmol/l
      • Chloride 111 mmol/l
      • Potassium 5 mmol/l
    • Normal Saline
      • Sodium 150mmol/l
      • Chloride 150 mmol/l
      • Potassium 0 mmol/l
      • Sodium 131 mmol/l
      • Chloride 111 mmol/l
      • Potassium 5 mmol/l
  • Preoperative blood testing
    • FBC
    • U&E
    • Coag screen
    • Group and Hold
  • Coagulation tests
    • Prothrombin time (PT)
      • extrinsic and common pathways
      • measures factors II, V, VII, X and fibrinogen
      • PT is expressed as International Normalised Ratio (INR)
      • Prolonged in:
        • Warfarin treatment
        • Liver disease
        • Vitamin K deficiency
        • Disseminated intravascular coagulation
  • Coagulation tests
    • Activated partial thromboplastin time (APPT)
      • Tests intrinsic pathways
      • Prolonged in:
        • Heparin treatment
        • Haemophilia and factor deficiencies
        • Liver disease
        • Disseminated intravascular coagulation
        • Massive transfusion
        • Lupus anticoagulant
  • Transfusion Medicine
    • Choose patients who need to have their blood type identified pre-operatively
  • Transfusion Medicine
    • ABO system
      • Consists of three allelles - A, B and O
      • antibodies are found in the serum of those lacking the corresponding antigen.
    • ABO blood group system
      • Blood group O = universal donor
      • Blood group AB = universal recipient
    • Rhesus system
      • Rhesus antibodies are immune antibodies requiring exposure during transfusion or pregnancy
      • 85% population are rhesus positive
  • Transfusion Medicine
    • Cross Matching
      • Patients red cells grouped for ABO and Rhesus antigens
      • Serum tested to confirm patients ABO group
      • Antibody screening to detect red cell antibodies in patient’s serum
      • Tests donor red cells against patients serum
  • Blood products
    • Whole blood
    • Packed red cells
    • Platelet concentrates
    • Human plasma - fresh frozen plasma
    • Human albumin 25%
    • Cryoprecipitate
    • Clotting factors - Factor VIII / IX
    • Immunoglobulins
  • Cryoprecipitate
    • prepared from plasma
    • contains factor 8, and fibrinogen.vWF Factor 13, and ffibronectin.
    • given as ABO compatible
    • Indications for giving cryoprecipitate
      • Haemophilia - Used for emergency back up when factor concentrates are not available.
      • Von Willebrands Disease - As with other forms of haemophilia, factor concentrates are the therapy of choice.
      • low fibrinogen levels as can occur with massive transfusions
      • Bleeding from excessive anticoagulation- FFP preferable
      • Massive haemorrhage
      • DIC
  • Fresh frozen plasma
    • the fluid portion of one unit of human blood
    • Contains components of the coagulation, fibrinolytic and complement systems
    • Indications for use
      • Reversal of warfarin effect
        • deficient in the vit K dependent coagulation factors II, VII, IX, and X, as well as proteins C and S.
        • can be reversed by the administration of vitamin K but immediate reversal with FFP for patients undergoing emergency surgery
      • Massive blood transfusion (>1 blood volume within several hours)
      • FFP is efficacious for treatment of deficiencies of factors II, V, VII, IX, X, and XI when specific component therapy isn’t available
      • Antithrombin 3 deficiency
  • Complications of blood transfusion
    • Early
    • Haemolytic reactions (immediate or delayed)
    • Bacterial infections from contamination
    • Allergic reactions to white cells or platelets
    • Air embolism
    • Hyperkalaemia
    • Clotting abnormalities
    • Late
    • Infection - cytomegalovirus / hepatitis
    • Immune sensitisation
    • Iron overload
  • Disseminated intravascular coagulation
    • Results in
      • activation of clotting cascade
      • Bleeding due to consumption of clotting factors
    • May present with
      • Bruising
      • purpura
      • Oozing (may be noticed during surgery)
    • Caused by
      • Severe infection (meningococcal)
      • metastatic adenocarcinoma
      • shock
      • Burns
      • Transfusion reactions
  • DIC cont’d
    • Investigation
      • Increased APTT and PT
      • Reduced serum fibrinogen levels (<1 mg / ml)
      • Thrombocytopenia
    • Management
      • Treat underlying cause
      • Supportive treatment with fluid and blood products including platelets, cryo and FFP
  • Goals of antibiotic administration
    • Reduce the incidence of surgical site infection
    • Minimise the effect of antibiotics on the host’s normal flora
    • Minimise damage to the Host’s immune system
    • Minimise adverse effects
  • Benefits of antibiotic prophylaxis
    • Reduce morbidity and mortality
    • Reduce length of hospital stay as a result
    • Avoidance of infection in surgical wounds associated with faster return to normal activity
  • Risks of prophylaxis
    • Anaphylactic reaction
    • Antibiotic related diarrhoea
    • Clostridium difficile infection more common in
      • Elderly
      • GI surgery
      • Use of broad spectrum antibiotics in particular 3rd generation cephalosporins
  • Risks of prophylaxis cont’d
    • Antibiotic resistance
      • Due to the amount of patients in a population receiving antibiotics and the length of time they are on them
      • Therefore prophylactic antibiotics should be a single dose unless otherwise indicated
  • Risks of prophylaxis cont’d
    • Multiple resistance
      • NB patients undergoing elective surgery (eg hip replacement, valve replacement, CABG) should undergo screening for carriage of MRSA prior to hospital stay
  • Indications for antibiotic prophylaxis
    • Intracranial surgery
    • Upper GI surgery
      • Oesophageal, stomach and duodenal surgery
    • Hepatobiliary
    • Lower GI
      • esp. colorectal and appendicectomy
  • Antibiotic prophylaxis
    • Not indicated for Clean abdominal operations
      • Hernia repair
      • OGD
      • Mesh repairs
    • Antibiotics should however be considered in High risk patients
  • How do the specific type of antibiotics translate into the need for antibiotics?
  • Predisposal to infection
    • Patient factors
      • Extremes of age
      • Poor nutritional status
      • Obesity
      • Diabetes
      • Co-existing infections
      • Immunosuppressants
  • Predisposal to infection
    • Operative factors
      • Length of operation
      • Shaving/skin prep
      • Sterility of instrument/theatre ventilation
      • Drain insertion
      • Haemostasis
      • Type of operation and adequate antimicrobial coverage
  • Classification of wounds
    • Clean
    • Clean contaminated
    • Contaminated
    • Dirty
  • Classification of wounds
    • Clean
      • No inflammation encountered
      • Viscera not entered
      • No break in aseptic technique
      • Eg hernia repair
  • Classification of wounds
    • Clean contaminated
      • emergency surgery
      • Viscus opened but no spillage of gut content
      • Minor break in aseptic technique
      • right hemicolectomy and cholecystectomy
      • Infection rate usually <10%
  • Classification of wounds
    • Contaminated
      • Wounds left open
      • Penetrating trauma less than 4 hours old
      • Viscus opened with inflammation or spillage of contents
      • Major break in sterile technique
      • appendicectomy and stab wound
      • Infection rate 15-20%
  • Classification of wounds
    • Dirty
      • Presence of pus
      • Intraperitoneal abscess formation or visceral perforation
      • Penetrating trauma more than 4 hours old
      • perforated abdominal viscera
      • Infection rate 40%
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  • Overview