Intracranial Hypertension Flashcards
What is intracranial hypertension?
Increases in ICP above the normal 15 mm Hg
Why is intracranial hypertension harmful?
It may impair cerebral perfusion pressure causing ischemia or it could lead to brain herniation.
How would you evaluate the presence and if present, the severity of intracranial hypertension?
First I would try and ascertain if the patient has a disease process that predisposes to intracranial hypertension, then I would look for signs and symptoms of intracranial hypertension like HA, N/V, AMS, HTN, bradycardia, bradypnea. I would also check to see if a CT/MRI where I would look for slit-like ventricles or a > 0.5 cm midline shift. If an ICP monitor were available, I would use that.
What different types of ICP monitors are there?
Intraventricular catheter (gold standard), subarachnoid bolt, epidural transducer, fiberoptic Camino catheters.
Would you insist an ICP monitor be placed preoperatively?
No. If I suspected increased ICP, I would likely begin therapy to lower ICP without direct measurement. If it’s unclear that increased ICP is the cause of the patient’s presentation, I would ask the neurosurgeon to help determine whether ICH were present.
How would you treat intracranial hypertension preoperatively?
- ABCs
- Hyperventilation to a PaCO2 no lower than 25 mm Hg otherwise the vasoconstriction itself could cause ischemia.
- Diuretics
- Elevate head 30 degrees
- Burr hold if severe
- CSF removal (via an epidural if hydrocephalus is not obstructive)
- Steroids if due to brain tumor
- Anti-seizure medications
Where would you place an arterial line transducer in a patient with intracranial hypertension?
Can be placed at level of external auditory canal which approximates the level of the circle of Willis. If not placed there, I would simply subtract 7mm Hg of pressure for ever 10cm the transducer was below that level to calculate the MAP perfusing the brain.
How would you modify your induction technique in the presence of ICH?
My goals are to protect the airway, guard against aspiration, and maintain CPP by avoiding large decreases or increases in BP. Increases in BP could compromise CPP, cause edema, bleeding or herniation). Key points: Preox, awake a-line, hyperventilate via gentle mask ventilation preferably with cricoid, give NDNMB defasciculating dose and lidocaine IV, then use fentanyl + etomidate + isoflurane while keeping BP close to baseline value and proceed to intubate. If I thought the aspiration risk exceeded the cerebral ischemia or herniation risk, I may opt to do an RSI instead. If the patient has a difficult airway/is unconscious/is hypotensive it may be better to intubate without any drugs at all.
Why is fentanyl a good drug to use during induction of a patient with intracranial hypertension?
Fentanyl is a narcotic analgesic that blunts response to intubation and surgery with minimal CV side effects. It’s use is unlikely to exacerbate the increased ICP and will blunt sympathetic response to the stimulation of intubation and surgery.
How would you intubate a combative patient with intracranial hypertension and a non-difficult airway?
As long as the patient is combative his ICP cannot be that high or he’d be unconscious. Hypoxia and hypotension should be ruled out as causes of his combativeness.
If intubation was emergent and airway is good, I’d perform an RSI using either thiopental or etomidate and succinylcholine. Given time, I’d premedicate with fentanyl and lidocaine to blunt the pressor response.
How would you intubate a combative patient with intracranial hypertension and a known or suspected difficult airway?
My priority would be to maintain spontaneous ventilation using gentle sedation and topicalization for an awake fiberoptic intubation.
At the end of a craniotomy, the surgeons cannot close the skull because of a swollen brain. Can you help them?
Assessment first: ABCs - eliminate the possibility that hypoxia, hypercarbia, hypertension, light anesthesia are causing the issue.
If vasodilators like SNP or NTG or high MAC inhaled agents are being used, they may need to be replaced with other, less vasodilating anesthetics.
If bleeding is a possibility, the surgeons need to address that.
Once all these possibilities are excluded, I could remove CSF from a ventriculostomy or lumbar drain, hyperventilate, or administer a barbiturate to further reduce CMRO2 and lower CBF if the BP is not already too low.
Hypotension occurs during removal of CSF from a lumbar drain. What would you do?
Immediately stop the drainage! Rapid drainage of CSF can cause brainstem herniation resulting in hypertension or hypotension, tachycardia or bradycardia. CSF drainage should not exceed 5cc/min. I would consider reinjecting CSF.
How would you extubate a patient with intracranial hypertension?
I may not extubate if the mental status were already impaired preoperatively or there was significant disruption of brain matter, cerebral edema, or significant hypo or hypercapnea were likely. Absent these conditions, the criteria should be no different than that for an otherwise healthy patient.
