Blood Flow to the Spinal CordAnterior Spinal Artery (1) Anterior 2/3 of spinal cordPosterior Spinal Arteries (2) posterior 1/3 of spinal cordThese 3 arteries depend on a network of collateral vessels to provide adequate blood supply to the spinal cord.
Artery of Adamkiewiczarteria radicularis magna Largest most consistent radicular artery Located in the thoracolumbar region (T5-L3) Supplies blood to the ASA (anterior 2/3 of cord) Responsible for most of the spinal cord blood flow beneath its point of entry If obstructed Anterior Artery Syndrome
Spinal Cord Blood FlowAutoregulation determines the amount of blood flow to the sp cd.Limits: 50-150 mmHg. Outside these limits pressure dependant.Spinal cord blood flow increases when CO2 levels are high and decreases when CO2 levels are low. (similar to cerebral blood flow)Injury to the spinal cord alters both autoregulation and CO2 responsiveness.
Spinal Cord InjuryTrauma Partial or Complete transection of the cordTransections above C 3-5 = Diaphragmatic innervention (ventilator required for survival)Transections above T 1 = QuadraplegiaTransections above L4 = ParaplegiaMost Common C 5-7 & T 12 - L 1 (least protected / most mobile)
Acute Spinal Cord InjurySpinal shock may begin within an hour after injury and last from several minutes to several months, after which reflex activity gradually returns: Flacid paralysis Complete loss of reflex and sensory activity below level of lesion. Loss of vasomotor tone, CV instability, Hypotension, Bradycardia, Venous pooling. Paralytic ileus with distension Hypothermia
ScoliosisLateral curvature of the spine, usually accompanied by rotation.Cobb angle is a method used to measure the curvature.The greater the angle, the greater the progression and severity of complications.
Causes of Scoliosis Neuromuscular Scoliosis - the result of muscle imbalance and lack of trunk control. (i.e. cerebral palsy, muscular dystrophy, or leg length discrepancy) Congenital Scoliosis - the result of asymmetry of the vertebrae secondary to congenital anomalies. (i.e. hemivertebrae, failure of segmentation) Idiopathic Scoliosis - no definite etiology. Diagnosis of exclusion. Most common type accounting for 80-85% of cases
Effects of scoliosis Increased curvature = narrowing of thoracic cage, which leads to abnormal CV and Pulm function. Increased curvature causes increased co-morbidities Restrictive lung disease, dyspnea on exertion, pulmonary hypertension, cor pulmonale and alveolar hypoventilation.
Spinal Cord Injury & SuccinylcholineSuccinylcholine- Induced Hyperkalemia.Safe to administer Succs within first 48 hours after spinal cord injury.Avoid Succs in all spinal cord injuries after 48 hours
Epidural Steroid Injections Methylprednisone 80 mg (smaller amounts in diabetics who may be at increased risk for formation of epidural abscess) is injected into epidural space close to the nerve root. The addition of 3-4 mL of local anesthetic (lidocaine) to the injected solution produces analgesia, confirming proper drug placement
Epidural Steroid Injection (cont.)Few pts get relief from repeated injections if first one was unsuccessful.Relief can last from weeks to months - injections are repeated every 3-4 months.Little risk of serious complications ; Aseptic meningitis and bacterial meningitisAdrenal Suppression may occur but recovers in 1-3 months.
High Dose Steroid Therapy(methylprednisone)Acute Spinal Cord InjurySevere spine disease undergoing major spinal surgery.Recommendation = bolus dose of 30 mg/kg over 15 minutes, then 5.4 mg/kg/hr for 23 hrs, within 8 hours of injury.If therapy is started 8 hours after injury, the duration of the methylprednisone therapy should be continued for 48 hoursPitfalls = Immunosuppression,wound infections & GI bleeds.
Tricyclic Antidepressants• Useful for chronic pain, producing analgesic effect via inhibition of reuptake of serotonin and norepinephrine.• Other benefits include: normalization of sleep patterns, reduction in anxiety and depression.
AnticonvulsantsMay have some efficacy in treatment of chronic pain syndromesChronic anticonvulsants lead to an increased resistance to non-depolarizing neuromuscular relaxants
Management of Spinal Cord InjuriesImmediate management is critical.Improper handling can cause further damage and loss of functioningAlways assume there is a spinal cord injury until it is ruled outImmobilizePrevent flexion, rotation or extension of neckAvoid twisting patient
Management cont’d• Management is aimed at preventing further injury and observing for progression of neuro deficits• Consists of emergency treatment following an A-B-C-D-E sequence.
Airway ManagementFirst priority.Open airway with jaw-thrust maneuver.Use bag-valve-mask device initially, if necessary intubate.High conc. of 02 will prevent bradycardia or asystole for patients exhibiting signs of neurogenic shock.
BreathingLesions above C5 level will cause partial to complete diaphragmatic paralysis (diaphragm is innervated at C3-5 levels).Lesions at C5 and below will allow full diaphragmatic movement, but intercostal muscles (innervated at T1) and abdominal muscles (innervated at T12) are affected.
CirculationCardiac output is affected by external or internal hemorrhage and neurogenic shock.IV fluidsBlood transfusionVasopressors
DisabilityNeurological ExaminationLateral C-Spine X-rayCT scanSearch for other injuries: abdominal, chest, …
Anesthesia Implications forAcute Spinal Cord Transection In-line stabilization of neck. Consider fiberoptic intubation, especially if cervical spine injury is suspected. Prepare for CV instability, position changes, mild blood loss, .. Guard against hypothermia. Succinylcholine may be administered within the first 24 hrs of acute injury Blood flow (maintain perfusion pressure, normal CO2) SSEP, MEP, wake up test
Anesthesia Implications forChronic Spinal Cord TransectionMonitor for autonomic hyperreflexia. Have rapid-acting vasodilators available.Bradycardia / absence of compensatory tachycardia (cardioaccelerators T1-4).Use nondepolarizing muscle relaxants only.Guard against hypothermia.Position carefully (osteoporosis).
Autonomic HyperreflexiaSympathetic system reflex response below the level of a spinal cord transection.At T5 or above.After the resolution of spinal shock.Triggers : stimulation below the level of injury.
Pre-operative EvaluationHistory & examination - type of scoliosis, assoc. problems ( neuromuscular, airway, GIT, MH, latex allergy), resp and cardiacCXR , ECG, Blood testsSpine Xray – severity & locationEchoLung Function Testing (if severe deformity)Lung volumes (>40% reduction ~ post-op complics)Flow volume loopABG
Preoperative preparationClear chest infection .Wake up test explaining.Posibility of post operative mechanical ventilationPremedication: atropine? Heavy sedation should be avoided in severe scoliosis.?
Anesthetic Problems associated withScoliosis SurgeryProblems related to the patient: Respiratory , cardiovascular neuromuscular abnormalities or syndromes.
Problems related to the surgeryProne positionBlood loss and third space loss: solution?Lengthy operationPreservation and monitoring of spinal cord function.Heat loss.??Postoperative visual loss.
MonitoringRoutine monitors: oximeter, ECG, capnography, esophageal stethoscope and core body tempArterial catheter to monitor beat to beat changes.CVPUrinary catheterBlood loss and replacement are monitored.Patient’s position
Induction of anesthesiaTwo large IV linesSuxamethonium. is avoided in paralyzed patients or neuromuscular etiology.Intermediate non depolarizing ms. relaxent like Atracurium or Rcuronium is used for intubation and maintenance of relaxation.
Prone positionMaintain alignment of head / neck, support head in neutral position w/ pillow or head holding device.Avoid hyperextension of arms by tucking them against the body or extending them <90 degrees alongside the head on armboardsCompression stockings to avoid the pooling of blood.Frequently examine eyes, ears, chin, nose, shoulders, breasts, and genitalia for areas of pressure.
Spinal Cord ProtectionMethylprednisoloneReestablish normotension, normooxia and normocarbia to avoid secondary insult.Instruct surgeon to decrease traction on spinal cord.Monitoring of the spinal cord: wake up test, SSEP and MEPs
Post Op Visual Loss -POVLUnkown Cause, may Risk Factors: hypoperfusion +edema Hypotension +stretching of the optic Anemia nerve. GlaucomaLong prone cases Preventative measures: Keep IV fluid to reasonableLarge amounts of IV level fluid. HCT > 27 MAP >70 mmHg Avoid pressure on globe
SPINAL CORD MONITORINGThe Wake Up Test: 2 assisstants Monitors motor function, simple to performProblems - extubation/lines/hardware, air embolism, awareness, false neg.Containdications – paresis, uncoop.Modified for use in small children (withdrawal to tetanic stimulus)
MOTOR EVOKED POTENTIALSMEP is basically an EMG potential recorded over muscles in the hand or foot in response to depolarization of the motor cortex using transcranial stimulus.MEP profoundly affected by anesthetic agents, recordable only during TIVAMEP cannot be recorded in the presence of complete neuromuscular blockade.
Extubation of the patientExtubation may be performed immediatelyExtubation in the ICU
Indications for postoperative mechanical ventilation:VC was < 30% of predicted.Severe gas exchange abnormality (↑PaCO2).Duchenne muscular dystrophy.Severe CP.Patient with congenital heart.Severe face edema.PaO2 on mask ↓70 mmHgRespiratory rate > 35 breath /min.
Post operative carePulmonary care.Fluid management.Pain control. How?Laboratory studies.
Case Study29 ys male pt. 110 kg. 9 days s/p MVA SCI. hx = asthma, donated one kidney.Planned surgery is a C1-3 Cervical fusion. dx: occipitoatlantal instability?
Pre OpMonitorsInductionMaintenanceEmergencePost Op
QuestionAll of the following are potential risk factors for POVL except for 2 of the following.• A. Obesity• B. Long Prone Cases• C. Anemia• D. Pressure on the globe• E. Hypotension• F. Glaucoma• G. Cataracts
Question• Paraplegia is the result of which of the following injuries?• A. Occlusion of the artery of adamkiewicz• B. Spinal cord transection at C7• C. Spinal cord transection at L2• D. A & C are both correct• E. All of the above are correct