Neuro Pharmacology

Question 1

Inhaled Anesthetics Impact

Answer 1

↓CMRO2 *except N2O
↑CBF d/t vasodilation
↑ICP

Question 2

IV Anesthetics Impact

Answer 2

↓CMRO2
↓CBF
↓ICP

Opioids +/-

Question 3

Local Anesthetics Impact

Answer 3

↓CMRO2
↓CBF
↓ICP

Question 4

Ketamine Impact

Answer 4

+/- CMRO2
↑CBF
↑ICP

Question 5

Nitrous Oxide

Answer 5

34x more soluble than Nitrogen in the blood

↑CMRO2, CBF, & ICP

Question 6

α1 Agonists

Answer 6

Bolus transiently ↑CBF & cerebral SaO2 (2-5min)

CPP maintenance w/ α1 agonist vasopressors have minimal effect on the brain

Question 7

α2 Agonists

Answer 7

↓CBF up to 25-30%

Results from reduced CMRO2

Question 8

β Agonists

Answer 8

Small doses - minimal effect on CBF
Large doses ↑MAP (i.e. Epi > 0.05mcg/kg/min) + physiological stress = ↑CMRO2 & CBF up to 20%
β1 receptors mediate effects
Response exaggerated w/ blood-brain barrier defect

Question 9

β Antagonist

Answer 9

Minimal or no effect on CMRO2 & CBF

Question 10

ACEi & ARBs

Answer 10

Minimal or no effect on CMRO2 & CBF

Autoregulation maintained

Question 11

Barbiturates

Answer 11

Dose-dependent ↓CBF & CMR until isoelectric EEG
Maximum CBF & cerebral metabolic reductions (nearly 50%) when flat EEG
↓ICP
ROBIN HOOD effect (reverse steal phenomenon)
- CBF redistributed to ischemic areas
↓CMR > CBF
Metabolic supply exceeds metabolic demand
Anticonvulsant except Methohexital

Question 12

Benzodiazepines

Answer 12

Dose-dependent ↓CBF & CMR
↑reduction in CBF & CMR as compared to narcotics
↓reduction in CMR & CBF as compared to barbiturates, Propofol, or Etomidate
Moderate CBF reduction
1° Midazolam
Potential to prolong emergence
Anticonvulsant properties

Question 13

Propofol

Answer 13

Dose-dependent ↓CBF & CMR
↓CBF exceeds metabolic rate
Short elimination half-life
Anticonvulsant
Commonly used as anesthesia maintenance in patients at risk to experience intracranial HTN
Most common neuro-anesthesia induction agent

Question 14

Etomidate

Answer 14

↓CBF, CMR, & ICP
Myoclonus movements on induction
Not 1st choice anticonvulsant but sometimes used to treat seizures
Small doses potential to activate seizure foci in patients w/ epilepsy

Question 15

Ketamine

Answer 15

Dilates cerebral vasculature & ↑CBF ↑ICP
Select activation limbic & reticular areas partially offset by somatosensory & auditory areas depression CMR does not change (controversial)

Less common in neuro-anesthesia d/t dissociative mechanism & difficult emergence
Advantages include stable hemodynamics in trauma

Question 16

NMDA Antagonist

Answer 16

N-methyl-D-aspartate
Glutamate receptor
Functionally dissociates the thalamus from the limbic cortex

Question 17

Thalamus

Answer 17

Relays sensory impulses from the reticular activating system to the cerebral cortex

Question 18

Limbic Cortex

Answer 18

Involved the sensation awareness

Question 19

Ketamine PD

Answer 19

↑HR, BP, & CO
↑secretions
Nystagmus
Hallucinogenic effects mitigated by Midazolam

NMDA antagonism potentially protective against neuronal cell death in brain injury patient

Question 20

Opioids

Answer 20

Minimal effects on CBF, CMR, & ICP (unless ↑PaCO2)

Avoid Morphine d/t poor lipid solubility, slower onset, & long sedative effect duration

Question 21

Cerebral Blood Volume & Cerebral Blood Flow

Answer 21

Cerebral ischemia ↑CBV ↓CBF
MAP = CBF
Cerebral vasoconstriction limits CBV
Initial ↑CBV does NOT ↑ICP d/t compensatory adjustments (venous blood shifts to extracerebral vessels & CSF shifts to spinal compartment)

Question 22

What MAP does cerebral autoregulation maintain intact?

Answer 22

Normal blood pressure

MAP 70-150mmHg