Ex 3 - AC for neuro patients

Question 1

Intra-Cranial Pressure (ICP)

Answer 1

The pressure exerted by the fluids and tissues inside on the the fixed compartment of the cranium.

Question 2

What four parts make up the fluids and tissues inside the cranium?

Answer 2

Blood, CSF, tissue or cells (both brain and otherwise), and ECF (i.e. edema)

Question 3

CNS (Cerebral) Metabolic Rate

CMR

Answer 3

This refers to the rate of substrate utilization by the CNS tissue.

Substrates include: O2 and glucose, or any other molecules necessary for brain fxn.

Question 4

CNS (Cerebral) Blood Flow (CBF)

Answer 4

The amount of blood being delivered to the cells and tissues w/in the cranium.

This varies depending on CMR, blood gases, blood viscosity, MAP, and anesthetic drugs

Question 5

Cerebral Perfusion Pressure (CPP)

Answer 5

The intravascular pressure minus the pressure in the surrounding tissues, generally given the following formulas:

CPP = MAP - ICP

The body will attempt to regulate the CPP to maintain appropriate delivery of O2 and other metabolic substrates to the tissues within the cranium

Question 6

What are some signs of ICP?

Answer 6

1. Papilledema (optic nerve swelling)
2. Anisocoria (unequal size of pupil) or dilated and fixed pupils
3. Strabismus (misalignment of the eyes)
4. Depressed mentation
5. Abnormal respiratory pattern
6. Opisthotonus (arching as in tetanus)
7. Bradycardia and hypertension (Cushing’s reflex - late marker of ICP)

Question 7

Is it better to prevent ICP or treat ICP?

Answer 7

Better to prevent

Question 8

What are some measure for prevention of ICP?

Answer 8

1. Maintain low normal PaCO2 (30-35mmHg)
2. Prevent significant hypoxemia
3. Maintain adequate MAP
4. Prevent significant alterations in acid-base status

Question 9

How can you treat ICP?

Answer 9

Mannitol or furosemide

Question 10

Why should you avoid administration of large volume of crystalloids?

Answer 10

75-90% of the crystalloid volume will be extravasated w/in the first hour after administration, and this increase in interstitial and cellular fluid will also be w/in the tissue inside the cranium.

Instead, you should give colloids and/or blood products –> these remain in the vascular for longer periods of time

Question 11

How should the patients head be positioned?

Answer 11

above the heart!

If the head is below the level of the heart this can cause venous congestion.

Question 12

Hyperglycemia in neuro patients

Answer 12

Hyperglycemia is common –> blood glucose should be monitored

Question 13

What role does BP play?

Answer 13

Hypertension –> increased CBF and thus ICP

Hypotension –> decreased CPP

Question 14

What role does hyperthermia play?

Answer 14

Increases CMR

hypothermia may be useful to decrease CMR, but severe hypothermia should be avoided <95 degrees

Question 15

Which drugs decrease both CBF and CMR?

Answer 15

Barbituates, benson, propofol, etomidate, and opioids (to varying degrees)

*respiratory depression w/opioids should be monitored/treated to prevent rises in PaCO2 and rise in CBF

Question 16

What is the effect of a2 agonists on CMR and CBF?

Answer 16

They also decrease both CMR and CBF, but the significant decrease in CO and peripheral vasoconstriction makes them contraindicated in these patients.

Question 17

Ketamine

Answer 17

In clinically useful doses, there are small decreases in CBF but much larger INCREASES in CMR
(increases ICP)

Very small doses are controversial, as they may provide some neuroprotective benefit but at a risk for inc ICP

Question 18

IA - effect on CMR and CBF?

Answer 18

At levels above 1 MAC, CBF will increase –> increase ICP in dose-dependent fashion

*Best to use IA in a balanced anesthetic protocol (so <1MAC doses are used)

Question 19

What about Propofol?

Answer 19

Can be used to maintain anesthesia, either as an adjunct to IA or as part of a balanced total IV anesthetic protocol.

Propofol preserves CBF/CMR coupling, so is a good choice

Question 20

What is the most common imaging modality for spinal cord?

Answer 20

MRI

Followed by:

CT, pyelography, rads, and fluoroscopy

Question 21

Why are patients with spinal pathology often dehydrated?

Even in seemingly acute situations?

Answer 21

They are often very painful and thus don’t eat/drink normally

*malnutrition and electrolyte imbalances are also possible, but less common

Question 22

How would you treat post-myelopgraphy seizures?

Answer 22

Benzodiazepine or propofol

Question 23

What is a major concern of PNS surgery?

Answer 23

PAIN management!

The use of local and/or regional analgesia is appropriate in all cases, and in combo with systemic analgesics such as opioids, a2 agonists, ketamine, lidocaine, and others will help prevent significant post-procedural pain.

Question 24

Which drug prevents wind up?

Answer 24

Ketamine! NMDA antagonist