Applied Physiology Exam 1
Autonomic hyperreflexia management
-General, spinal, epidural, or regional anesthesia may help block stimulation (epidural less effective than spinal) -Vasodilator infusions (nitroprusside, nicardipine, nitroglycerine)
Clinical indications for thiazide diuretics
-HYPERTENSION -heart failure -Nephrolothiasis -Nephrogenic DI
Risk factors of AKI
-High-risk surgeries -Intravascular volume depletion -Sepsis -Shock _Old age -Preexisting renal insufficiency -Crush injuries leading to myoglobinuria -Nephrotoxins
Side effects of carbonic anhydrase inhibitors
-Hyperchloremic metabolic acidosis -Renal stones -Renal potassium wasting -Drowsiness and paresthesias after long doses
Clinical indications for loop diuretics
-Hyperkalemia -Acute renal failure -Anion overdose
Common causes of chronic kidney disease
-Hypertensive nephrosclerosis -Diabetic nephropathy -Chronic glomerulonephritis -Polycystic kidney disease
Pulmonary symptoms of CKD
-Hyperventilation -Pulmonary edema -Pleural effusion
Toxicity of Thiazide Diuretics
-Hypokalemia metabolic alkalosis -Hyperuricemia -Hyperglycemia -Hyperlipidemia -Sulfadrug (allergic) -Hyponatremia
Acute kidney disease parameters
-Oliguric <400 ml/days -There's also non-oliguric which is high output AKI -Creatine increases: >0.3 mg/dL (48 hrs) and 1.5 increase over 7 days -May also occur with multiorgan system failure
Agents that alter water excretion
-Osmotic diuretics -ADH Agonists -ADA Antagonists
What medications to avoid in pts with CKD
-Pancuronium -Vecuronium -Morphine -Codeine -Meperidine
Neurologic symptoms of CKD
-Peripheral neuropathy -Confusion -Seizures -Coma
Treatment for mountain sickness
Carbonic anhydrase inhibitors
What medication works on the proximal tubule
Carbonic anhydrase inhibitors
autonomic hyperreflexia
Massive, uncompensated cardiovascular response to stimulation of the sympathetic nervous system Stimulation of the sensory receptors below the level of the cord lesion
What 2 pressures need to be maintained during neuroanesthesia?
Mean arterial pressure and cerebral perfusion pressure
Where does ADH act?
Medullary Collecting duct of nephron
How does hyperoxia affect CBF?
Minimally decreases it by about 10%
Besides the kidney and the eye, what other organ do carbonic anhydrase inhibitors work on?
The brain- used to treat cerebral edemas because carbonic anhydrase is involved in the formation of CSF by the choroid plexus
Above what MAC impairs autoregulation?
2
Loop diuretics duration
2-3 hours
Mannitol concentration in a bag
20% in 500 mL bag
How much cardiac output do the kidneys receive?
20-25%
Furosemide dose to reduce ICP
20-40 mg
What range does PaCO2 affect cerebral blood flow?
20-80 mmHg
normal bicarb levels
22-30 mEq/L
Mannitol concentration in vial
25% in 50 mL vial
What anesthetic agents avoid renal clearance?
-Cisatracurium, Rocuronium, Fentanyl, Dilaudid
GFR rate for moderate impairment
25-40 mL/min
Thiazide diuretic examples
HCTZ, chlorthalidone, metalozone
Effects of venous air embolism (5)
-Decreased PaO2 -Decreased MAP -Increased pulm. artery pressure (PAP) -Increased Et nitrogen content -Decreased CO2
hallmarks of autonomic hyperreflexia
Hallmarks: hypertension and reflex bradycardia (carotid sinus)
Why should you avoid ketamine in neurocases?
It increases CBF by cerebrovasodilating, CSF volume and ICP.
Why should you avoid nitrous in neurocases?
It increases CBF, ICP, and expands in closed air spaces
Why is ketamine avoided for neurocases?
It increases CMRO2 and CBF
Why should etomidate be avoided in neuropts?
It is associated with seizures and myoclonic activity
What brain shrinking agent is ideal for craniotomy for tumor resection?
Mannitol
What brain-shrinking agents may lead to pulmonary edema in CHF patients?
Mannitol and 3% hypertonic solution
What 2 drugs can you not give for neuroanesthesia and why?
Nitrous oxide and Ketamine because they both increase CBF, CMRO2, and ICP
Do IV anesthetics affect coupling of CMRO2 and blood flow?
No
Do nitrous oxide, barbituates, and opiates interfere with autoregulation?
No
Does nitrous oxide affect coupling of CMRO2 and blood flow?
No
Anesthesia effects on the kidney
-Decreased blood pressure -Decreased RBF -Sympathetic nervous response: renal artery vasoconstriction -ADH released --> decreased urine output
Drugs that decrease brain interstitial fluid
-Dexamethasone -Mannitol -3% Hypertonic Saline -Furosemide
If you had a patient that is normally hypertensive, can you drop the blood pressure as low as a normal patient?
No must remain higher
Per Fick equation, total body oxygen consumption is _______ mL/min and the brain consumes ____% of that.
250 mL of O2/ min and the brain consumes 20% of that
Time to form 1 cc of CSF
3 minutes
When does brain damage occur during a hypoxic crisis?
3-8 min
Per 100g of brain, what is the normal oxygen consumption rate?
3.5 mL of O2/100g brain per minute
normal potassium levels
3.5-5.0 mEq/L
Mannitol onset
30 minutes
Does the brain have oxygen storage?
No so it relies 100% on blood flow for oxygen -3-4 minutes without blood flow will cause damage
Eye opening response (GCS)
4 spontaneously 3 to speech 2 to pain 1 no response
GFR rate for mild impairment
40-60 mL/min (pts usually asymp.)
Verbal Response (GCS)
5 - oriented 4 - confused 3 - inappropriate words 2 - incomprehensible sounds 1 - none
Normal ICP range
5-15
How much does CBF change per change in degree of celsius?
5-7%
What is the average flow rate per minute per 100g of brain?
50 mL
Nitroglycerine comes in
50 mg in 5% dextrose in 250 mL (200 mcg/mL)
Nitroglycerine bolus dose
50-100 mcg
Cerebral blood flow is autoregulated at a MAP between ___________
50-150 mmHG
What is to normal CSF production a day?
500 mL
Mannitol duration
6 hours
Motor response (GCS)
6-obeys commands 5-localizes pain 4-withdraws from pain 3-abnormal flexion 2-abnormal extension 1-none
Cerebral Blood Flow is kept constant over what range of MAP?
60-160 mmHg
How much of bowman's capsule ultra filtrate is reabsorbed by the proximal tubule?
65-75%
Adequate oxygenation for neurocases is when PaO2 is greater than
70 mmHg
Normal glucose levels
70-140 mg/dL
What is the average flow rate of blood to the brain?
750 ml/min
How long does dexamethasone take to reduce brain swelling
8-24 hrs
Normal calcium levels
8.6-10.5 mg/dL
What is the normal range of CPP?
80-100 mmHg
Renal blood flow is autoregulated at MAPS from
80-180 mmHg
Female normal GFR
95 cc/min
normal chloride levels
98-106 mEq/L
Oliguria is defined as
<0.5 cc/kg/hour or less than 400-500 cc in 24 hrs
GFR rate for end stage kidney disease
<10 mL/min
GFR rate for renal failure
<25 mL/min
Can you give steroids to pts with traumatic brain injuries?
No they've been linked to higher mortality rates
Anuria
No urine <50 ccs in 24 hrs
Can you give dextrose to someone with elevated ICP?
No.that will increase the CMRO2 of the brain
Where do you want blood pressure in hemorrhagic strokes?
Normal or slightly lower than normal to reduce bleeding
Does sux increase ICP?
Not if intubating correctly and the patient is paralyzed adequately
Risk Factors of perioperative vision loss
Obese males requiring long surgery, had lots of blood loss, were given lots of crystalloid, and the wilson frame was used on them
Postrenal causes of AKI
Obstruction of urine flow: BPH, stones, tumors
Mneumonic for cranial nerves
Oh Oh Oh To Touch And Feel A Girls Vagina Ah Heaven
Treatment for autonomic hyperreflexia
Treat high blood pressure due to extreme vasoconstriction --> Labetalol
Keep glucose levels under _____ for patients with increased ICP
Under 150
ADH agonists renal action is mediated by
V2 receptor
Where do you want blood pressure in ischemic strokes?
VERY high to attempt to overcome a low flow state with the pressure
What nerve is efferent for carotid baroreceptors?
Vagus
ADH agonist used for central diabetes insipidus
Vasopressin and Desmopressin (DDAVP)
ADH Agonists examples
Vasopressin and desmopressin
What factor that causes a shift to the left on the cerebral autoregulation curve?
Volatile anesthetic agents: this means that there is adequate cerebral autoregulation even at lower blood pressures
GFR equation
Volume of blood filtered into Bowman's capsule/ time
How much CSF is in the brain and the spinal cord at any given time?
around 150ml (25-50ml in spinal column the rest surrounds the brain).
For all carotid endarterectomy procedures, place a
arterial line because wide BP ranges
Dexamethasone follows
blood glucose
Nitroglycerine MOA
causes the release of Nitric oxide from the vasculature which activates guanylate cyclase, increasing cyclic GMP, decreasing calcium release, therefore reducing smooth muscle vasculature tone.
In high concentrations, all volatile inhaled anesthetics impair
cerebral autoregulation
Where is the CSF produced?
choroid plexus in ventricles
Normal CSF flow pathway
choroid plexus-lateral ventricles-3rd ventricle-4th ventricle-subarachnoid space-arachnoid villi
Renin release is stimulated by
decrease in blood pressure
If the patient's head is up, ICP
decreases
Sympathetic stimulation _____ CBF and parasympathetic stimulation ________ CBF
decreases due to vasoconstriction ; increases due to vasodilation
2 common loop diuretics
furosemide and ethacrynic acid (don't see any more)
Intrarenal causes of AKI
glomerular damage from inflammation, toxins, drugs, infection
Cortical collecting tubule principal cells secrete
Aldosterone (which causes sodium reabsorption)
Potassium sparing diuretics MOA
Aldosterone antagonist in the distal convoluted tubule
Why do you want a decrease cerebral metabolic rate coupled with a decrease in cerebral blood flow?
Allows the brain to be less sensitive to ischemia; Provides cerebroprotection
What kind of stroke is caused by a blood clot?
An ischemic one
Are iso and des more pro or anti convulsants?
Anticonvulsants
What MR can you use for neuroanesthesia?
Any but make sure to consider any co-morbidities
What artery supplies blood to supplies blood to the lower cord and where does it start?
Artery of Adamkiewicz; Arises T8-T12
if CPP is <50 mmHg what happens in the brain
ischemia and neurons will start to die
Hyperglycemia is harmful to the injured brain because
it compromises circulation, the blood brain barrier, and promotes inflammation
What kidney is higher?
left kidney because the liver takes up room on the right and pushes the right kidney lower
Lasix is what kind of diuretic?
loop
What is the most efficacious diuretic? Why?
loop diuretics because they are not limited by acidosis and because they target the thick ascending limb of the loop of henle where large amounts of NaCl are reabsorbed. If you inhibit this process, you're gonna pee more out.
When MEP's or motors are being recorded do not use
muscle relaxants
EMG measures
muscle response or electrical activity in response to a nerve's stimulation of the muscle
EEG measures
neuron activity and brain wave activity
Peritubular capillaries favor (filtration/reabsorption)
reabsorption
Osmotic Diuretics
reduce intracranial pressure and intraocular pressure by raising serum osmolality and drawing fluid back into the vascular and extravascular space
Renal function is intimately related to
renal blood flow
Efferent arterioles in the kidney travel alongside
renal tubules
Juxtaglomerular cells contain
renin
Thiazide diuretics may elevate
serum uric acid levels
To ensure good mental status after extubation for neurocases, use
shorter acting agents
What is the major function of the proximal tubule?
sodium reabsorption
Potassium sparing diuretic examples
spironolactone, eplerenone, triamterene, amiloride
What is responsible for vascular tone?
sympathetic innervation
juxtaglomerular apparatus is innervated by
sympathetic nervous system
Loop diuretics activity directly correlates with
their secretion by the proximal tubule
What part of the loop of Henle is impermeable to H20?
thick ascending loop and where electrolyte reabsorption is
Glomerulus capillaries favor (filtration/reabsorption)
tuft of capillaries that favor filtration
Thiazide diuretics compete with the secretion of
uric acid
If there is an increase in MAP then cerebral vaso_____
vasoconstriction
Renin release causes
vasoconstriction and vascular hypertrophy (b1 adrenergic stimulation)
ADH causes
vasoconstriction leading to urine concentration
If there is a decrease in MAP then cerebral vaso___
vasodilation
When do you administer brain shrinking agents?
Before or during intubation. Want to be working before surgery
Component percentages of brain, blood, and cerebrospinal fluid
Brain: 80% Blood: 10% CSF: 10%
How is CSF absorbed into the blood?
By arachnoid villa
Management of chronic spinal cord injuries
-FOCUS ON AUTONOMIC HYPERREFLEXIA (occurs in T8 or higher pts) -NDMR -Avoid sux in pts with spinal cord injury greater than 24 hrs in duration -
CV symptoms of CKD
-Fluid overload -CHF -HTN --> LVH -Atherosclerosis - CAD -Dysrhythmias -Pericadistis
GI symptoms fo CKD
-N/V -Delayed gastric emptying -Anorexia
Nitroglycerine infusion
0.25-.5 mcg/kg/MIN
Kidney Functions (General)
-Excretion of metabolic waste products -Regulation of water and electrolytes balances -Reabsorption of nutrients -Regulation of acid and bases -Regulation of arterial pressure -Secretion, metabolism, and excretion of hormones, drugs, and toxins
Mannitol dose
0.25-0.5 g/kg
normal serum creatinine
0.4-1.5
Factors the affect cerebral blood flow (4)
-Cerebral Perfusion Pressure -Autoregulation -Autonomic innervation -PaCO2
Toxicity of loop diuretics
"OH DANG!" Ototoxicity Hypokalemia Dehydration Allergy (sulfa) Nephritis (interstitial) Gout
Prerenal causes of AKI
*Prerenal = most common cause of AKI* - Factors that reduce systemic circulation, causing a reduction in renal blood flow - The decrease in blood flow leads to decreased glomerular perfusion and filtration of the kidneys - In prerenal oliguria there is no damage to the kidney tissue. The oliguria is caused by a decrease in circulating volume 1. Hypovolemia → hypotension - Dehydration - Hemorrhage - GI losses (diarrhea, vomiting) - Excessive diuresis - Hypoalbuminemia - Burns 2. Decreased CO - Cardiac dysrhythmias - Cardiogenic shock - HF - MI 3. Decreased PVR - Anaphylaxis - Neurologic injury - Septic shock 4. Vascular obstruction - Thrombosis - Embolism - Hepatorenal syndrome
Kidney blood flow
- blood from renal artery (branches of celiac trunk) flows into afferent arterioles which form glomeruli in Bowman's capsule - blood then flows through efferent arteriole to the vasa recta, which surround the nephron, before leaving the kidney through the renal vein
How many grams approximately is the brain?
1500 grams
Toxicity of Potassium-sparing diuretics
- most important: *hyperkalemia* These drugs should *never be given with potassium supplements* - Other *aldosterone antagonists* (eg, angiotensin [ACE] inhibitors and angiotensin receptor blockers [ARBs]), if used at all, should be used with *caution* - *Spironolactone* can cause *endocrine abnormalities* (including gynecomastia and antiandrogenic effects) - Eplerenone has less affinity for gonadal steroid receptors. -Hyperchloremic metabolic acidosis -Acute renal failure
Blood flow to the brain
-80% internal carotid arteries -20% vertebral arteries
Monitoring of CKD
-Avoid BP cuff and IV in arm with arteriovenous fistula -May need arterial line for ABG and electrolyte monitoring
How to prevent perioperative vision loss
-Avoid: exc. blood loss (>800 mL), prolonged surgeries, hypotension, and poor positioning
How to assess patient in pre-op for kidney function
-Blood Urea Nitrogen -Serum creatinine -Glomerular filtration rate (interchangeable with creatine) -Urinalysis (additional test; useful for assessing infection)
Polycythemia -Blood viscosity -CBF
-Blood viscosity: Increase -CBF: decrease
Anemia -Blood viscosity -CBF
-Blood viscosity: decrease -CBF: increase
Hyperthermia: -Brain activity -CMRO2 -CBF
-Brain activity: Increase -CMRO2: Increase -CBF: Increase
Hypothermia: -Brain activity -CMRO2 -CBF
-Brain activity: decrease -CMRO2: decrease -CBF: decrease
Factors that cause cerebral autoregulation to be absent (5)
-Brain trauma -Surgical retraction -high ICP -Brain tumor -Seizures
Management of acute spinal cord injury
-IVF bolus to compensate for vasodilation -Mechanical ventilation -Inotropic support: ephedrine -Drip: -Manual in-line stabilization laryngoscopy -Maintain SCP -No N2O -Bigger dose of roc for RSI -Do not give sux after 24 hrs
Contraindications for carbonic anhydrase inhibitors
-If NH4+ levels are high -Cirrhosis patients
Chronic spinal cord injury symptoms/sequlae
-Impaired alveolar ventilation -CV instability --> autonomic hyperreflexia -Chronic pulmonary and GI infections -Anemia -Altered thermoregulation -Renal failure -Deep vein thrombosis
Endocrine symptoms of CKD
-Insulin resistance -Hyperparathyroidism -Hypertriglyceridemia
Anesthesia plan when SSEPs are being recorded -Gas -Don't use -Use
-Keep gas <1 MAC -Avoid Nitrous oxide, Ketamine, and Etomidate -Use propofol, opioids, and benzos
Spinal shock symptoms
-Loss of temperature regulation and spinal cord reflexes below level of injury -Decreased bp caused by loss of SNS, SVR, and bradycardia
What are the basic tenants of neuroanesthesia? (4)
-Maintain cerebral oxygenation and perfusion -Employ measures to decrease intracranial volume and intracranial pressure -Keep patient relaxed -Keep patient normoglycemic and normothermic
Osmotic diuretics toxicity
-Mannitol rapidly distributed in the extracellular compartment --> extracts water from cells leading to hyponatremia and expansion of extracellular fluid -Can complicate heart failure and lead to pulmonary edema -Diminished renal function = mannitol retained = hyponatremia
Preop concerns of patients with CKD
-Metabolic acidosis -Chronic anemia -Platelet dysfunction -Fluid overload (before dialysis) OR hypovolemia (after dialysis) -Electrolyte disorders
Clinical indications for carbonic anhydrase inhibitors
-Metabolic alkalosis -Glaucoma -Acute mountain sickness -Urinary alkalinization
Typical spinal anesthesia includes: -Preop -Induction -Maintenance -Lines -Analgesia
-Preop: acetaminophen, NSAID, antinoceptive, fentanyl, versed -Induction: Propofol, RSI dose of ROC with video laryngoscopy and manual in-line stabilization -Maintenance: 0.5 MAC of VA and TIVA (may need neuromonitoring -Lines: 2 peripheral IV and a-line -Analgesia: peripheral nerve blocks or spinals or epidurals or combo
AKI management
-Preop: make sure to stop nephrotoxins -In case: -Administer approp. doses -Optimize CO and RBF -Monitor fluid intake and output -Treat acute complications
Clinical indications for potassium sparing diuretics
-Primary or secondary hyperaldosteronism -Help counteract the hyperaldosteronism caused by thiazides or loop diuretics
What can cause low urine output perioperatively?
-Problem with urinary catheter and drainage system -Low blood pressure -Surgery type
Furosemide and ethacrynic acid (loop diuretics) have been show to help with what 2 conditions?
-Pulmonary congestion -Heart failure
Induction for patients with CKD
-RSI -Check pre-op potassium (Sux)
Direct measurements of ICP
-Subdural bolt -Subdural catheter Subdural catheter - Epidural transducer Epidural transducer - Intraparenchymal fiberoptic catheter -Intraparenchymal fiberoptic catheter -Ventriculostomy
Ligaments spinals pass through
-Supraspinous ligament -Interspinous ligament -Ligamentum flavum
Factors that cause a shift to the right on the cerebral autoregulation curve? (2)
-Systemic hypertension -States of sympathetic activation
Clinical indications for osmotic diuretics
-Want water excretion opposed to sodium -Prevent anuria -Reduction of ICP and IOP
For every 1 increase PaCO2 cerebral blood volume increases
0.05 ml/100g/min
Mannitol peak
1-2 hours
For ever 1 mmHg change in PaCO2, CBF changes by
1-2 mL/ 100 g of brain per min
A decrease in hemoglobin causes
1. Increase in CBF 2. Decrease in O2 content 3. Little change in O2 delivery until Hgb drops <7
Normal magnesium levels
1.6-2.6 mEq/L
Treatment for venous air embolism
1.Tell surgeon to flood the field with bone wax or saline 2. Discontinue nitrous oxide use (if applicable) 3. Aspirate central line 4. Avoid any positive pressure maneuvers or PEEP 5. Supportive measures with phenylephrine (pts usually have hypotension and tachy) 6. Place patient in LEFT LATERAL DECUBITUS position and TRENDELENBURG 7. 100% FiO2
Normal Blood Urea Nitrogen (BUN)
10-20 mg/dL
Male normal GFR
120 cc/min
Normal sodium levels
135-145 mEq/L
How much cardiac output does the brain receive?
15-20%
What arrhythmia is associated with blood clots that travel to the brain?
A fib due to a clot in the atrial appendage
With loop diuretics, why don't you see a decrease in calcium like the other electrolytes?
Calcium absorption can be increased in the intestines and calcium is also actively reabsorbed in the distal convoluted tubule
Circle of willis
A structure at the base of the brain that is formed by the joining of the carotid and basilar arteries.
Indirect diagnosis methods of increased ICP and suggestive findings
CT scan or MRI -Midline shift -Obliteration of basal cisterns -Loss of sulci -Ventricular effacement -Edema
Indications for hemodialysis
AEIOU A: Refractory metabolic acidosis (<7.2) E: Refractory hyperkalemia (electrolytes) I: Intoxications O: Volume overload or pulm edema not responding to diuretics U: Uremia: uremic pericarditis, uremic encephalopathy or neuropathy
Cerebral auto-regulation definition
Ability of the cerebral blood vessels to alter their caliber in order to maintain a constant flow in face of variations in blood pressure
How does ischemia affect autoregulation?
Abolishes it
Most common carbonic anhydrase inhibitor
Acetazolamide
Above 1 MAC, CBF _______ and CMRO2 __________
CBF increases as the dose increases and CMRO2 stays the same or decreases
The effects of all anesthetics may be enhanced due to decreased protein binding in what patients?
CKD
Does metabolic acidosis affect the brain?
CO2 crosses the BBB but hydrogen ions
Cerebral perfusion pressure equation and which variable is more important?
CPP= Mean Arterial Pressure (MAP) - Intracranial Pressure (ICP) ((Or Central Venous Pressure: whichever is bigger)) MAP is more important because it is the larger number in the equation
Affect of increased PaCO2 on cerebral blood flow
Causes vasodilation therefore increasing the blood flow. This is why hyperventilation aids in decreasing ICP
Do we want an increase in ICP or decrease?
Decrease
How does hypothermia affect CBF and CMRO2?
Decreases
What drug decrease cerebral autoregulation?
Dexmedetomidine (Precedex)
What part of the nephron contains the juxtaglomerular apparatus?
Distal tubule
What is the gold standard for monitoring in carotid endarterectomy?
EEG
In addition to the infusion, what other drugs should be ready for carotid endarterectomy?
Glycopylorrate and atropine for severe and moderate brady
What VA should be avoided in elevated ICP and seizure pts? Why?
Enflurane because it increases production of CSF and decreases its absorption = Elevated ICP
What potassium-sparing diuretic is more selective so it has fewer side effects?
Eplerenone
How long is hyperventilation useful for decreasing ICP?
For 6-24 hours
Lasix is the trade name for
Furosemide
What drug acts synergistically with Mannitol?
Furosemide
What drug increases renal blood flow?
Furosemide
What brain shrinking agent is better for diabetics?
Furosemide because it follows potassium and does not change glucose levels
Chronic Kidney Disease is defined as
GFR < 60 mL/min for greater than 3 months -Half of renal function may be lost before testes of GFR become abnormal and 75% of nephrons lost before pt is symptomatic
What nerve is afferent for carotid baroreceptors?
Glossopharyngeal
What kind of stroke is caused by a bleed?
Hemorrhagic
Metabolic symptoms of CKD: Hyper and Hypo
Hyper: potassium**, sodium, magnesium, phosphate, metabolic acidosis** Hypo: calcium, sodium
Prolonged use of Loop diuretics can cause:
Hypomagnesmia and hypokalemia
What kind of solution does the distal tubule receive from the loop of henle?
Hypotonic
Hunt-Hess Classification of Subarachnoid Hemorrhage
I - asymptomatic or mild headache, slight nuchal rigidity II - moderate to severe h/a, nuchal rigidity III - mild focal deficit, lethargy or confusion IV - stupor, mild to severe hemiparesis, early decerebrate rigidity V - deep coma, decerebrate rigidity, moribund appearance
Why can't you use mannitol if the BBB is not intact?
If it is not intact mannitol can absorb into brain matter and increase ICP by pulling in more water to the brain tissue.
Monro-Kellie Doctrine
If one component increases, another must decrease to maintain ICP
How does severe hypoxia affect CBF?
Increases
Relationship between creatinine, BUN, and GFR
Inverse relationship between GFR and BUN-Creatinine levels As GFR goes up, creatinine and BUN go down. If your kidneys are functioning at the appropriate rate your BUN and creatinine levels should be low. If they are elevated, your kidneys are not doing their job.
What VA is most useful for neurosurgery and why?
Isoflurane because: -Most potent reduction in CMRO2 -Only agent to produce isoelectric EEG -Decreased production of CSF and increased reabsorption
How is hypothermia useful for ischemic brain injury?
It decreases metabolic and basal oxygen demand and increases vascular resistance through vasoconstriction
Organ with primary cause in high blood pressure
Kidney
What position for venous air embolism treatment?
LEFT LATERAL DECUBITUS position and TRENDELENBURG
Avoid what fluid in CKD pts?
Lactated ringer's if pre-op potassium elevated
Where should blood sugar goals be?
Less than 180 mg/dL
Propofol infusions for SSEP neuromonitoring
Less than 200 mcg/kg/min
What glasglow coma score requires intubation?
Less than 8 intubate
How can surgeons reduce the baroreceptor response during carotid endarterectomy?
Localize carotids with lidocaine
Bradycardia from a spinal cord injury is caused by
Loss of T1-T4 sympathetic innervation to the heart
What MAC for volatile anesthetics for neurocases?
Lower MAC the better 0.5 MAC Do not exceed 1 MAC
Remember to place a bite block when ______ are being recorded and why?
MEP's because no muscle relaxant
The most common osmotic diuretic used to decrease ICP is...
Mannitol
What should your ventilation be at before the dura is opened for neurocases?
Moderate hyperventilation (PaCO2 30-35 mmHG) to help lower ICP Once the dura is open, the ICP is released. If not, hyperventilate to 30 mmHG but not lower. Don't listen to surgeon if they tell you to go lower.
Proconvulsants (2)
N2O and Narcotics
What receptor does nitrous and ketamine act on?
NMDA and both may cause neuronal damage due to its action on glutamate
What drug type competes with loop diuretics and should not be taken at the same time?
NSAIDS
Loop Diuretics inhibit
NaCl reabsorption in the thick ascending limb of the loop of henle
What infusion should be ready for carotid endarterectomy?
Neosynephrine and Nitroglycerine
What treats vasospasms associated with subarachnoid hemorrhage?
Nimodipine
What diuretic can cause metabolic acidosis?
Potassium sparing diuretics
What additional agents for a patient with cirrhosis that is experiencing volume retention and hypokalemia while taking furosemide?
Potassium sparing diuretics along with fursemide (Spironolactone)
Along with sodium, What other electrolytes' homeostasis is the loop of henle involved in?
Potassium, calcium, and magnesium
Cerebral perfusion pressure (CPP) definition
Pressure that carries blood to the brain
What is the IV induction agent of choice for neuro cases? Why?
Propofol because it decreases CBF and CMRO2
Where are thiazide diuretics secreted?
Proximal tubule
Why is it nice to use a volatile anesthetic for neurocases?
Quick wake up because you know exactly when a patient is going to wake up whereas propofol infusion is guesstimating
What is the primary function of the loop of henle?
Recovery of water and sodium from urine
What position are venous air embolism more likely?
Sitting position
Why would you want a neuroanesthetic that has rapid emergence?
So they would be able to do a neuroexam after the procedure
Mneumonic for motor vs. sensory function of cranial nerves
Some Say Marry Money But My Brother Says Big Butts Matter More
Spinals are placed ________ and epidurals are placed _________
Spinal cord nerve roots below L1 ; Epidural space anywhere along spine
Perioperative vision loss is associated with
Spinal surgeries Likely due to hypoperfusion of optic circulation
What muscle relaxant should you avoid for spinal cord injuries?
Sux
What systolic and diastolic pressures should a patient be left at after a stroke?
Systolic: Not higher than 140 mmHg Diastolic: Minimum of 90 mmHg
Chronic hypertension usually shift their curve in what direction and why?
They are used to higher pressures to stay autoregulated so the curve shifts to the right
What drug targets the distal tubule?
Thiazide diuretics because the inhibit NaCl transport in the distal convoluted tubule and enhance Calcium reabsorption
What portion of the loop of henle reabsorbs the water?
Thin ascending limb
Can propofol affect EMG activity?
Yes
Can you use volatile anesthetics for neurocases and why?
Yes in a normal patient but must use them sparingly. Preferably around 0.5 MAC but do not go over 1 MAC because of CMRO2 and CBF uncoupling. In an abnormal patient, stay away from because autoregulation is already messed up (tumor, trauma, hemorrhage, ICP issues, etc.)
Cortical collecting tubule intercalated. cells regulate
acids and bases
hematologic symptoms of CKD
anemia, bleeding, infection, platelet dysfunction
Cushing triad - what is it a sign of?
hypertension, reflex bradycardia, respiratory depression - sign of increased intracranial pressure (constricts arterioles - cerebral hypoperfusion - sympathetic response causes HTN)
If the patient's head is down, ICP
increases
Hypercarbia ______ CBF and Hypocarbia ______ CBF
increases ; decreases
Carbonic Anhydrase Inhibitors MOA
inhibit carbonic anhydrase less bicarbonate reabsorbed more Na lost in tubular lumen carbonic anhydrase also in the eye - involved in production of aqueous humor (treat for glaucoma)
A decrease in CSF volume would tend to decrease
intracranial volume and ICP
