Mod IX: Anesthesia for Intracranial Procedures

Question 1

_{Anesthesia for Craniotomies}

•Premedication

Answer 1

• Versed 1-2mg
• Fentanyl 50-100 mcg

Question 2

_{Anesthesia for Craniotomies - Premedication}

•Versed 1-2mg - •Avoid in

Answer 2

sedate patients or

patients who may become hypercarbic

(the increased CO2 will increase pressures in the brain)

Question 3

_{Anesthesia for Craniotomies - Premedication}

•Fentanyl 50-100 mcg - Again, with caution because

Answer 3

you don’t want the patient to hypoventilate

Question 4

_{Anesthesia for Craniotomies - Premedication}

What is already on anticonvulsant and BP medications?

Answer 4

Continue all anticonvulsant and BP medications

Question 5

_{Anesthesia for Craniotomies - Premedication}

Why would many of the patients be on H2-blockers?

Answer 5

to combat the gastric side effects of steroid therapy

Question 6

_{Anesthesia for Craniotomies}

Monitoring and Vascular Access

Answer 6

2 large bore PIVs

Aline

CVP – based on risk assessment of acquiring a VAE

Question 7

_{Anesthesia for Craniotomies}

Conditions associated with LOW RISK of VAE

Answer 7

Supine, prone, or lateral with minimal head elevation (<15 degrees)

Operation not near major venous sinus

Question 8

_{Anesthesia for Craniotomies}

Conditions associated with INTERMEDIATE RISK of VAE

Answer 8

Moderate head elevation (15-30 degrees)

Mild head elevation, but operating near major venous sinus

Question 9

_{Anesthesia for Craniotomies}

Conditions associated with HIGH RISK of VAE

Answer 9

True sitting position (>45 degrees)

Moderate head elevation and

Tumor invading bone or near a major vessel

Question 10

_{Anesthesia for Craniotomies}

Graphical representation of Supratentorial vs. Infratentorial Tumors

Answer 10

Graphical representation of Supratentorial vs. Infratentorial Tumors

Major Supratentorial brain structure = Cerebrum

Major Infratentorial brain structures = Cerebellum & Brainstem

Question 11

_{Anesthesia for Craniotomies}

What’s the GOAL of induction? How is it acheived?

Answer 11

Keep the patient normotensive

Avoid up swings and dips in the pressure as a result of your intubation

Question 12

_{Anesthesia for Craniotomies - Induction}

Agents:

Answer 12

Propofol 1-2 mg/kg

Fentanyl up to 15 mcg/kg

NDMR

Choose volatile agent

Question 13

_{Anesthesia for Craniotomies - Induction}

Ensure that the DL and intubation is smooth. Prior to DL how should the pt be?

Answer 13

Well anesthetized and paralyzed

Question 14

_{Anesthesia for Craniotomies - Maintenance}

assist with brain relaxation

Answer 14

Infusions

Question 15

_{Anesthesia for Craniotomies - Maintenance}

Common infusions

Answer 15

Methohexital (Brevital) 30-50 mcg/kg/hr ~versus~

Propofol (diprivan) 3-6 mcg/kg/hr

Remifentanyl 0.08 – 2 mcg/kg/min

_{[<strong>Remifentanyl </strong>keeps the pt still and prevent the use of a NDMB especially if neuro monitoring required]}

Question 16

_{Anesthesia for Craniotomies - Maintenance}

Volatile Agent – have to take what into consideration?

Answer 16

Neuromonitoring

Question 17

_{Anesthesia for Craniotomies - Maintenance}

Goal of Fluids management

Answer 17

Keep patient normovolemic

Question 18

_{Anesthesia for Craniotomies}

•Mayfield Head frame Placement effect on BP

Answer 18

Can cause a 20% increase in BP

Question 19

_{Anesthesia for Craniotomies}

•Mayfield Head frame Placement Can cause a 20% increase in BP. How do you prepare for this?

Answer 19

Have a bolus of propofol and/or fentanyl ready to administer prior to placement

Be aware of the onset time of the drug you are administering so that the effect occurs at the appropriate time

Question 20

_{Anesthesia for Craniotomies}

Once the surgeon places the head frame; who is responsible for moving the head while positioning the patient?

Answer 20

The Surgeon

Once the surgeon places the head frame; THEY are responsible for moving the head while positioning the patient

Question 21

_{Anesthesia for Craniotomies}

***If you have a patient in the Mayfield, it is critical that the patient does NOT move while in pins. Why?

Answer 21

A simple cough or buck can cause them to break their neck and cause paralysis.

Question 22

_{Anesthesia for Craniotomies}

When should patient with Mayfield head frame be reversed?

Answer 22

Don’t reverse these patients until head frame removed.

Question 23

_{Anesthesia for Craniotomies}

Some pictures of the Mayfield head frame

Answer 23

Some pictures of the Mayfield head frame

_{<em>https://www.youtube.com/watch?v=pgDSbA107Ow</em>}

Question 24

_{Anesthesia for Craniotomies}

Techniques used to allow for safe opening of the dura and access to the tumor, aka:

Answer 24

Brain Relaxation Techniques

Question 25

_{Anesthesia for Craniotomies}

Brain Relaxation Techniques

Answer 25

• Hyperventilation
• Diuretic Therapy

Question 26

_{Anesthesia for Craniotomies - Brain Relaxation Techniques}

•Hyperventilation

Answer 26

Maintain a PaCO2 of 25 mmHg until dural closure is in site;

then, it is a gradual increase until normocarbia is reached as you approach emergence so the pt can breath again

Question 27

_{Anesthesia for Craniotomies - Brain Relaxation Techniques}

•Diuretic Therapy

Answer 27

Dosing of mannitol and lasix will be proportionate to the severity of the brain swelling and the needs of the surgeon

Mannitol

mannitol 0.5-1 gram/kg

• Administer over 10-15 min
• 1-2 g/kg dose can reduce brain water by approx. 90 ml and lasts up to 3 hrs

_{[Some physicians may ask for an additional dose of Mannitol and/or of Lasix]}

Furosemide

•Furosemide 10-20 mg

Question 28

_{Brain Relaxation Techniques - Diuretic Therapy}

•Ideally, when should you start the diuretic?

Answer 28

1hour prior to incision of the dura

Question 29

_{Brain Relaxation Techniques - Diuretic Therapy}

Mannitol administration

Answer 29

Mannitol 0.5-1 gram/kg

• Administer over 10-15 min
• 1-2 g/kg dose can reduce brain water by approx. 90 ml and lasts up to 3 hrs

Question 30

_{Anesthesia for Craniotomies}

•What if your techniques aren’t giving you a slack brain?

Answer 30

You may still have a “Tight Brain”

Question 31

_{Anesthesia for Craniotomies}

Differential Diagnosis for “Tight Brain”

Answer 31

Hypercapnia / hypoxemia

Venous outflow empedence

^{(D/t Poor head and neck position preventing venous drainage - Head down posture}

^{Inadequate neuromuscular blockade - Light anesthesia)}

Hypertension

Vasodilators

Patient disease

Question 32

_{Anesthesia for Craniotomies}

Emergence is both Critical and difficult - What’s the GOAL of Emergence?

Answer 32

Render the patient neurologically assessable without excessive coughing, straining, or systemic hypertension

Question 33

_{Anesthesia for Craniotomies - Emergence}

When should IV drugs be discontinued?

Answer 33

After the Mayfield head frame is removed

Patient is in the supine position

Discontinue IV drugs when dural closure starts

Return patient to normocarbic state

Continue neuromuscular blockade

Waiting to reverse and neuromuscular blockade until dressings are applied decreases the patient’s ability to cough

Lidocaine 1.5 mg/kg can be administered

Reverse when the dressings are applied

Agent off and flows increased

Treat HTN with beta blocker or hydralazine – keep patient normotensive

Titrate pain medications to respiratory rate; however, you don’t want the patient too sleepy

THIS TASK IS A CAREFUL BALANCE BETWEEN THE PATIENT WAKING COMFORTABLY VERSUS COUGHING AND BUCKING. –BUT, IS DOABLE!

Question 34

_{Anesthesia for Craniotomies - Emergence}

Lidocaine 1.5 mg/kg can be administered, but remember that this may

Answer 34

increase somnolence