Neuroanesthesia

Question 1

ASA I (all surgery)

Answer 1

*Normal, healthy patient.
*0.08 % mortality within 48h
*0.06% mortality within 7 days

Question 2

ASA II (all surgery)

Answer 2

II - mild systemic disease, no functional limitation
*0.27% mortality within 48h
*0.4% mortality within 7d

Question 3

ASA III (all surgery)

Answer 3

III - severe systemic disease, definitive functional limitation
*1.8% mortality within 48h
*4.3% mortality within 7d

Question 4

ASA IV (all surgery)

Answer 4

IV - severe systemic disease that is a constant threat to life
*7.8% mortality within 48h
*23.4% mortality within 7d

Question 5

ASA V (all surgery)

Answer 5

V - moribund, expected to die within 24h with or without surgery.
*9.4% mortality within 48h
*50.7% mortality within 7d

Question 6

ASA VI (all surgery)

Answer 6

VI- organ donor

Question 7

WHat does the appendix “e” stand for in the ASA classification?

Answer 7

It means that emergency surgery is associated with 3x the risk compared to the given ASA % that are stated for elective surgey.

Question 8

what factors determines CPP?

Answer 8

Cerebral perfusion pressure
- intact ?
- Blood pressure.
- ICP

Question 9

Where should the srterial IV line be calibrated?

Answer 9

By meatus to etter reflect the intracranial BP.

Question 10

How does the jugular venous pressure influence ICP?

Question 11

What is the most potent cerebral vasodilator?

Answer 11

CO2.

Question 12

What does hyperventilation create?

Answer 12

*Decreased CBV
*Decreased CBF

Question 13

What is ETCO2?

Answer 13

End tidal Co2

Question 14

How does ETCO2 correlate to arterial CO2?

Answer 14

Usually ETCO2 is approximately 5mmHg lower than in arterial blood.
The goal is PaCO2 30-35.

Question 15

Why is the PaCO2 extra important in stereotactic surgery?

Answer 15

Due to the possible intracranial shifts when the bloodvolume changes.

Question 16

WHy is hematocrit (Hct) important in neurosurgery?

Answer 16

Due to the O2 binding capacity in relation to the rheology.

Question 17

What is the problem with hypOvolemia in neurosurgical cases?

Answer 17

It may impair blood flow.

Question 18

What has to be thought of in prone position?

Answer 18

Excessive fluids can contribute to facial edema and PION in the worst case.

Question 19

Positioning changes!

Answer 19

During surgery, control of changes in position is necessary. It might be very dangerous to the patient.

Question 20

Postoperative nausea and vomiting must be avoided as much as possible.
Which anesthetic drugs should be avoided?

Question 21

What antiemetica might lower the seizure treshold?

Question 22

Why should inhalation anesthesia be avoided?

Answer 22

They REDUCE central metabolism by suppressing neuronal activity.
That might sound good BUT
They DISTURB CEREBRAL AUTOREGULATION and cause cerebral vasodilation.

Question 23

What is nitrous oxide doing in the brain?

Answer 23

It potently vasodilate. Increase CBF and also a little the cerebral metabolism.
Contributes to postoperative nausea and vomiting N/V.

EXCEPT FOR THAT! It is uterly dangerous in the setting of air embolus or pneumocephalus, where it fills the air space and increase the pressure A LOT.

Question 24

What group of agents are primarily used today?

Answer 24

Halogenated agents like Isoflurane and Sevoflurane.
-all of which suppress EEG activity and provide cerebral protection.

Question 25

What drug is generally used for induction?

Answer 25

Propofol. *unknown action. - but works as a sedative hypnotic. *Short 1/2 life. *no active metabolites.

Question 26

When Propofol is used as TIVA- total intravenous anethesia- What does it do to MAP and ICP?

Answer 26

It causes dose-dependent decrease in mean arterial blood pressure MAP and ICP. * reduces CMRO2 * Reduces CBF and ICP * Short 1/2 life.

Question 27

What barbiturate is usually used in induction?

Answer 27

Sodium thiopenthal. * Rapid onset * Short acting * minimal effect on ICP, CBF and CMRO2

Question 28

What is the mechanism of Ketamine?

Answer 28

* Its an NMDA receptor antagonist * It produces dissociative anesthesia. * Maintains cardiac output.

Question 29

Positives and NEGATIVES with nonsynthetic narcotics - morphine

Answer 29

+ : Increase CSF absorption and minimally reduce cerebral metabolism. - : * Cause dose-dependent respiratory depression ---hypercarbia in the non-ventilated patient. *N/V postop. * Cause histamine release * Can accumulate in renal or hepatic insufficient patient and cause confusion

Question 30

Why is histamine release not good in neuro-patients?

Answer 30

* May cause hypotension * May cause cerebrovascular vasodilation ------CPP problems.-----

Question 31

What is good with synthetic narcotics?

Answer 31

They do not cause histamine release.

Question 32

Name two synthetic narcotics prominently used in neurosetting

Answer 32

* Fentanyl * Remifentanil (ultiva)

Question 33

What is special with ultiva-remifentanyl?

Answer 33

* Reduces CMRO2 * Reduces CBV and ICP * Large doses might be toxic to the limbic system.

Question 34

What is special with Fentanyl?

Answer 34

* Crosses BBB * Reduces CMRO2 * Reduces CBV and ICP * May be given as bolus or infusion

Question 35

What is the action of Benzodiazepines and what are main (neuro) effects?

Answer 35

* GABA agonists * Decrease CMRO2 * Provide anticonvulsant action * Produce amnesia

Question 36

Name two commonly used paralytics

Answer 36

* Succinylcholine * Rocuronium

Question 37

What is the only depolarizing agent used?

Answer 37

Succinylcholine.

Question 38

What side-effects make succinylcholin non-preferable in injuries or children/adolecsens?

Answer 38

Extra risk of Malignant hyperthermia.

Question 39

Which is the only non-depolarizing agent approved for rapid sequence intubation?

Answer 39

Rocuronium.

Question 40

What are anesthetic requirements for intraoperative evoked potential monitoring?

Answer 40

INDUCTION: * Minimize pentothal or use etomidate *! Use TIVA NOT inhalation. + Obs nondepolarizing muscle relaxants have little effect on evoked potentials! + Propofol has mild effect on evoked potentials, *continous infusion should be used, not boluses. * Obs! SSEPs can be affected by hyper or hypothermia and by changes in BP. + Hypocapnia, down to end tidal CO2 21 has no effect on peak latencies + Antiepileptic drugs have NO effect on SSEPs.

Question 41

What is Malignant hyperthermia?

Answer 41

Idiopathic block of Ca 2+ re-entry into SR. Genetic predisposal Body O2 consumption raise by 2-3 times. Fulminant form -muscle ridgidity so intubation is impossible. + if progressing; DIC, pulomnary edema, Rhabdomyolysis, cardiac arrest and death !!!! Frequently associated by use of Succinylcholine!

Question 42

What is the incidence of Malignant hyperthermia?

Answer 42

Peds: 1:15000 Adults: 1:40000

Question 43

Treatment of Malignant hyperthermia?

Answer 43

* Eliminate offending agent * DANTROLENE SODIUM - 2.5mg/kg iv up to 10mg/kg until symtoms subside. * Hyperventialtion w 100% oxygen. * Cooling * Bicarbonate for acidosis Procainamide for arrythmias * Diuresis - volume loadinga nd osmotic diuresis.