Term
| Scenario: A previously ischemic area of the brain is now being reperfused. What's the harm in this? |
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Definition
| The inflammatory response has created a second wave of attack: Phagocytes are now surrounding dead as well as salvageable cells and destroying them. (Destroying some of the penumbra) |
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Term
| You know that areas distal to tumors and malformations are susceptible to ischemia, but what's a very important human intervention that can cause ischemia as well? |
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Definition
| tissue that's being manipulated by retractors |
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Term
| What's the term that fits this definition: vessels in ischemic areas maximally dilate in an attempt to provide ischemic areas maximal blood flow/oxygen? |
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Definition
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Term
| Blood makes up what percentage of cranial volume? CSF? |
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Definition
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Term
| What intracranial compartment is easiest for us to manipulate? |
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Definition
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Term
| List some situations that may decrease venous outflow thus increasing the % of blood in the brain. |
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Definition
- Tight C-collars or ET ties
- High airway pressures (increased intrathoracic pressure)
- Central lines (particularly in people with small vessels)
- head down position
- head rotation
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Term
Give me the dural sinus pressure for each respective position:
prone
supine(flat)
sitting (90 degrees)
sitting (25 degrees)
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Definition
prone and supine: 6 cm H20
sitting (90 degrees): -13 cm H20
sitting (25 degrees): 0 cm H20 |
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Term
| You're taking care of a patient with brain ischemia and an elevated ICP. The ischemic area is maximally dilated; what is this phenomenon called? You're hyperventilating your patient causing _______ in the non-ischemic areas. Blood is still flowing freely and is diverted to the maximally dilated ischemic areas but not so much to the normal tissue; what is this phenomenon called? |
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Definition
luxury perfusion
vasoconstriction
inverse steal or Robinhood Phenomenon |
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Term
| What's the typical PaC02 in a patient who is being hyperventilated according to Gayle's notes? Will I see any increased vasocontriction if I go below 20 torr? |
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Definition
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Term
| You're taking care of some dude with brain ischemia; what phenomena occurs when you crank up your isoflurane dial? |
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Definition
| intracerebral steal: vessels traveling to ischemic areas are maximally dilated so flow is originally diverted to them. Once you crank up the iso, all vessels dilate and flow is "stolen" from the maximally dilated ischemic tissue. |
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Term
| You have been hyperventilating your patient but the neurosurgeon says they don't need it anymore. Ol' girl CRNA comes in to give you a break and turns your vent respiratory rate from 20 to 8. What do you do next? |
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Definition
| Punch her in the gut and tell her, "A rapid return to normocapnia can produce a sudden increase in ICP....You betta wreckinize, biaatch! We goin to normocapnia in slow-motion up in this mug, biaatch!" |
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Term
| What are some things to worry about when you are using mannitol? |
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Definition
Until diuresis occurs there is a temporary increase in ICP and CVP!
o May cause pulmonary edema
o If the BBB is disrupted (intracranial hemorrhage) may cause mannitol to fall out of intravascular space and would lead to brain parenchyma swelling→exacerbating problem
o Think about the patient in renal failure/low GFR and heart failure: slowed diuresis increases the time that mannitol sits in the intravascular space. This leads to dilutional hyponatremia, worsening CHF and pulmonary edema.
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Term
| What's the dose of mannitol to reduce ICP? What's the ultimate goal of mannitol dosing? |
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Definition
| • Dose: 0.25-1.0 grams/kg (subsequent doses may be given until serum osmolality>320 mOsm/L). Gayle says: after dose is repeated, she checks the serum osmolality. |
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Term
| T or F: hemodilution effectively reduces ICP by reducing blood viscosity. |
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Definition
| False: hemodilution (HCT 30%) improves perfusion by reducing blood viscosity. |
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Term
| How does PaO2 affect crebral blood flow? |
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Definition
| It doesn't until it's less than 50 mmHg,then it cause vasodilation. |
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Term
| You want to decrease ICP in your patient but they have pulmonary edema. You're already hyperventilating them and using propofol. What else can you do? |
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Definition
| give them lasix. It's not as good as mannitol but you don't want to use mannitol in patients with pulmonary edema because it just makes it worse. |
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Term
| what's the dose for lasix to reduce ICP? If using mannitol as well? What's the other boneriffic quality of lasix that might help a little to reduce ICP in a "non-venous" way? |
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Definition
• Dose: 0.5-1.0 mg/kg
• Dose w/Mannitol: 0.15-0.3 mg/kg (1/3 of the dose). Watch for severe dehydration, electrolyte disturbances)
It decreases CSF production! |
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Term
| How low should you go with ventriculostomy drain bags? |
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Definition
| 15cm below (tragus I'm assuming) |
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Term
| Are steroids effective at reducing ICP in all elevated ICP situations? |
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Definition
No
Used to reduce edema associated with:
o Tumors
o Trauma (NOTE: Effect does not occur for 24-72 hours)
Methylprednisolone administration within 3-8 hours of spinal cord injury is a standard of care.
o Dose: 30mg/kg load over 1 hour then 5.4mg/kg for next 23 hours.
Data on effectiveness is conflicting and many practitioners don’t like it b/c it is associated with an increase in sepsis, pneumonia, and prolonged hospitalization.
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Term
| How long does vasodilation from volatiles last? |
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Definition
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Term
| What anesthetic agent has the least affect on increasing CBF? |
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Definition
| iso (note: it also reduces CSF) |
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Term
| Do vessels still respond to hyperventilation in presence of volatiles? |
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Definition
| Yes! the vasodilation effects can be offset by hyperventilation. |
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