1	Anesthesia Board Review – FSA 2007 Michael E. Mahla, MD Professor of Anesthesiology and Neurosurgery
2	Regarding acute T9 Spinal cord injury: Systemic hypotension is common following this injury even in the absence of other injuries Use of succinylcholine for intubation is contraindicated 36 hours after injury Posterior tibial twitch response will be resistant to muscle relaxants 36 hours after injury Autonomic hyperreflexia is unlikely following this injury
3	Acute Spinal Cord Injury Physical and physiologic manifestations depend largely on level of injury and accompanying injuries. Assume for discussion that spinal cord injury is isolated –i.e. no other injuries. Spinal cord injury below T8 will largely be transparent to the anesthesiologist. Injury above T8 will be accompanied by increasing level of hypotension secondary to loss of sympathetic tone. T6-8 innervates the splanchnic capacitance vessels Injury above T2 will be accompanied by increasing respiratory insufficiency. Level above C7 is at significant risk for respiratory failure and severe hypotension.
4	Acute Spinal Cord Injury Spinal shock Occurs immediately with injury Secondary to loss of primarily sympathetic tone. Bradycardia and hypotension BP generally between 70 and 90 systolic. Lower than 70 systolic has another or additional cause. Lasts generally up to 2 weeks with most severe period in first 72 hours. Treat with volume (careful, though) and vasopressor Phenylephrine Dopamine
5	Acute Spinal Cord Injury Immediate therapy If able to treat within 8 hours of injury Methylprednisolone 30mg/kg bolus then 5.5 mg/kg/hr for 24 hours. Controversial still Benefit significant but small Keep blood pressure high normal Stabilize unstable spinal column (operatively) ASAP to prevent further injury.
6	Acute Cervical Cord Injury Signs Flaccid paralysis below level Intercostal muscle failure Diaphragm failure with level @ or above C7 (spinal cord will swell above lesion and will often result in respiratory failure even though original level was C7) Hypotension Bradycardia Bowel and bladder function failure
7	Effect of Hemiplegia on Tof4 Hemiplegia caused by spinal cord injury (uncommon) or CVA Up-regulation of ACh receptors on weak side. Muscle becomes resistant to non-depolarizers because of up-regulated receptors. Following Tof4 on paretic or plegic side will result in significant overdose of muscle relaxant.
8	Autonomic Hyperreflexia Normal autonomic function Loss of supratentorial control Spinal cord below lesion recovers – but is not regulated from above. Normal sympathetic reflexes in response to noxious stimulus greatly exaggerated and generalized. Results in hypertension and bradycardia
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10	In a 62 year old patient with Parkinson’s Disease undergoing elective inguinal hernia repair Anti-Parkinson’s medication should be withheld for 48 hours prior to surgery Use of succinylcholine is contraindicated for intubation Subarachnoid block should not be considered because of likelihood of worsening symptoms perioperatively Caution should be used with anti-emetic drugs perioperatively.
11	Parkinson’s Disease Anesthetic considerations – nearly all related to drugs used to treat Parkinson’s Disease Entacapone (Comtan): Peripheral catechol-o-methyl transferase inhibitor Prevents peripheral breakdown of L-dopa greatly increasing its availability to the CNS So………..what should we NOT give EPHEDRINE Reduce doses of any direct acting agents Phenylephrine is likely the drug of choice – metabolized mainly in the liver – COMT not a significant player
12	Parkinson’s Disease Pharmacotherapy Carbidopa / levodopa – CONTINUE through perioperative period. Failure to do so may result in severe rigidity that may complicate care. May interact with sympathomimetics to produce hypertension and dysrhythmias. Beta blocking agents with vasodilators as needed to treat this problem. May interact with halothane (sensitizes myocardium to catecholamines) Selegiline – MAO (B) inhibitor – be careful with vasopressors
13	Parkinson’s Disease Disease Related Considerations Higher incidence of postoperative delirium Longer hospital stays for given surgical procedure Suggestion of higher mortality for surgery Increased risk for: Aspiration pneumonia Urinary tract infection Bacterial infection of all types
14	Cerebral Blood Flow: Interventions In a CEA, during crossclamping, this maneuver would be expected to increase cerebral blood flow in the face of cerebral ischemia 1. Hypoventilation 2. Hyperventilation to shift blood flow from non-ischemic areas to ischemic areas 3. Thiopental 4. Increase MAP with phenylephrine
15	Hyperventilation Basics
16	Hyperventilation Basics Effects of CO₂ cannot be considered alone. Blood pressure, pO₂, and metabolism have significant effects. We are also rarely dealing with normal brains. Most studies in the literature which influence or direct current practice involve patients with normal brains under physiologic conditions. Hyperventilation will not produce desired (or desirable) effects in patients with abnormal brains or under pathophysiologic conditions.
17	Hyperventilation Basics
18	Hyperventilation Basics
19	Hyperventilation Basics
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21	Vascular resistance SVR = (MAP - CVP) x 80 dynes/sec/cm^-5 CO (l/min) PVR = (MPAP - PCWP) x 80 CO (l/min)
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27	Pacemaker thresholds Rest or sleep: (harder to pace) Stress: ¯ (easier to pace) Glucose: Bicarbonate: NC PaO₂ with ¯ PaO₂ ¯ with PaO₂ PaCO₂ with PaCO₂ ¯ with ¯ PaCO₂ K+ with ¯ K ¯ with K Na+ with 3% NaCl
28	Pacemaker thresholds Isoproterenol ¯ with low dose with high dose Beta-blockers Procainamide if toxic dose Digoxin ? ¯ acutely, clinically NC Glucocorticoid ¯ Mineralocorticoid
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30	pH vs. a-Stat pH-stat is temperature corrected, run at patient’s actual temperature relies on exogenous CO₂ to make PaCO₂ 40 with pH of 7.40 CBF pressure dependent a-stat gases run at 37 degrees regardless of patient’s temperature relies on a-histidine moiety to create physiologic buffer cerebral autoregulation intact
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33	Aortic Stenosis Increase Normal to increased Normal Avoid extremes Sinus Preload Afterload Contractility HR Rhythm
34	Mitral Stenosis Maintain Normal Normal Decrease Usually AF Preload Afterload Contractility HR Rhythm
35	Aortic Regurgitation Maintain Normal to decrease Normal Normal to increase Preload Afterload Contractility HR
36	IHSS (ASH, SAM) Normal Increased Decreased Decreased Sinus Preload Afterload Contractility HR Rhythm
37	Carbon Monoxide
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40	Carbon Monoxide Symptoms
41	In Diabetes Insipidus
42	Treatment of Diabetes Insipidus occurring after head trauma
43	Diabetes Insipidus Inability of kidneys to conserve water Types: Central: lack of ADH Rx: Vasopressin (desmopressin, DDAVP) Nephrogenic: insensitivity to ADH Rx: D/C inciting medication (ie lithium); increase fluid intake; decrease UOP (indomethacin, HCTZ, amiloride)
44	Methemoglobinemia
45	Benzocaine
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47	Increased dead space ventilation may occur during anesthesia due to
48	Dead Space
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