Applied Physiology Exam 1

Clinical indications for thiazide diuretics

-HYPERTENSION -heart failure -Nephrolithiasis by hypercalciuria -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

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

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 by PTH

Treatment for mountain sickness

Carbonic anhydrase inhibitors

What medication works on the proximal tubule

Carbonic anhydrase inhibitors

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%

Above what MAC impairs autoregulation?

2

Loop diuretics duration

2-3 hours

What is the average blood flow for white matter of the brain?

20 mL/ 100 g brain/ min

How much CSF is produced per hour?

20 mL/hr

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

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

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 agents may lead to pulmonary edema in CHF patients?

Mannitol and 3% hypertonic solution

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

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

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

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

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

How many nerves does the spinal cord consist of? What does each segment contain?

31 segmental nerves. Pair of ventral (motor) and dorsal (sensory) nerve roots.

Spinal cord segments

33 vertebrae - 7 cervical - 12 thoracic - 5 lumbar - 5 sacral (fused) - 4 coccygeal (fused

Eye opening response (GCS)

4 spontaneously 3 to speech 2 to pain 1 no response

What percentage of cerebral oxygen consumption is used to maintain cellular integrity?

40%

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

Brain glucose consumption is ____ / 100 g/min

5 mg

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

What percentage of cerebral oxygen consumption is used to generate ATP to support neuronal electrical activity?

60%

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 average blood flow for gray matter of the brain?

80 mL/ 100 g brain/ min

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

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).

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 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

For all carotid endarterectomy procedures, place a

arterial line because wide BP ranges

Dexamethasone follows

blood glucose

What forms the vertebral foramen and what does it consist of?

body, 2 pedicles, 2 laminae form it. Consists of spinal cord, nerves, and epidural space

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.

Where does the gray matter lie in the spinal cord?

center of the spinal cord

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

Cerebral function is dependent on a

continuous supply of glucose

Autonomic hyperreflexia can be initiated by what kind of stimulation?

cutaneous or visceral stimulation below the level of spinal cord transection (bowel or bladder surgery)

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

Gray matter in the spinal cord forms ____

dorsal and ventral horns

Where does the white matter lie in the spinal cord?

externally in the spinal cord

EEG change for CBF between 15-20mL/ 100 g/min

flattening of EEG

EEG change for CPP between 25-50 mmHg

flattening of EEG

autonomic hyperreflexia pathway

full bladder or stimulus from bowel -> afferent stimulus -> massive sympathetic response -> widespread vasoconstriction -> hypertension -> baroreceptors detect hypertensive crisis -> slowed HR -> descending inhibitory signals blocked at spinal cord injury (T6 or above)

2 common loop diuretics

furosemide and ethacrynic acid

Intrarenal causes of AKI

glomerular damage from inflammation, toxins, drugs, infection

Neuronal cells utilize _____ as their primary energy source

glucose

Carbonic Anhydrase Inhibitors MOA

Acts in PCT. Inhibits carbonic anhydrase activity -> decreased H ion production -> block NaHCO3 reabsorption -> alkalized urine

Potassium sparing diuretics MOA

Aldosterone antagonist in the distal convoluted tubule (inhibits Na absorption and K excretion)

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

Hyperglycemia is harmful to the injured brain because

it compromises circulation, the blood brain barrier, and promotes inflammation

During starvation, glucose consumption is replaced with

ketone bodies

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 effective 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.

Spinal cord is continuous with the ____

medulla oblongata

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

Renal function is intimately related to

renal blood flow

Efferent arterioles in the kidney travel alongside

renal tubules

To avoid ischemic optic neuropathy, what is the best positioning to place patients in?

reverse Trendelenburg, eyes w/o pressure, neck neutral

Which regions of the brain are more sensitive to hypoxic injury?

rostral "higher" regions (cortex, hippocampus)

Thiazide diuretics may elevate

serum uric acid levels

To ensure good mental status after extubation for neurocases, use

shorter acting agents

EEG change for CBF below 20-25 mL/ 100 g/min

slowing of EEG

EEG change for CPP below 50 mmHG

slowing of EEG

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

White matter in the spinal cord contains _____

tracts of nerve fibers linking cord with the brain

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)

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

CV symptoms of CKD

-Fluid overload -CHF -HTN --> LVH -Atherosclerosis - CAD -Dysrhythmias -Pericadistis

Autonomic hyperreflexia management

-General, spinal, epidural, or regional anesthesia may help block stimulation (epidural less effective than spinal) -Vasodilator infusions (nitroprusside, nicardipine, nitroglycerine drips)

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

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 -

normal serum creatinine

0.4-1.5

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

What anesthetic agents avoid renal clearance?

-Cisatracurium, Rocuronium, Fentanyl, Dilaudid

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

Most common pathology for intervertebral disc disease/back pain

- nerve root or spinal cord compression from nucleus pulposus protruding through annulus fibrosis

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

Factors the affect cerebral blood flow (4)

-Cerebral Perfusion Pressure -Autoregulation -Autonomic innervation -PaCO2

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

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

GI symptoms fo CKD

-N/V -Delayed gastric emptying -Anorexia

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

Contraindications for carbonic anhydrase inhibitors and why

1. If NH4+ levels are high: alkalized urine decreases NH4+ excretion 2. Cirrhosis patients: hyperammonemia and hepatic encephalopathy

A decrease in hemoglobin causes

1. Increase in CBF 2. Decrease in O2 content 3. Little change in O2 delivery until Hgb drops <7

Anesthetic goals for spine surgery

1. Maintain SCP 2. Multimodal analgesia 3. Adequate neuromonitoring 4. Avoid ischemic optic neuropathy

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

Interruption of cerebral perfusion for ___ leads to unconsciousness

10 seconds

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%

How many grams approximately is the brain?

1500 grams

What arrhythmia is associated with blood clots that travel to the brain?

A fib due to a clot in the atrial appendage

Circle of willis

A structure at the base of the brain that is formed by the joining of the carotid and basilar arteries.

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

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

Affect of increased PaCO2 on cerebral blood flow

Causes vasodilation therefore increasing the blood flow. This is why hyperventilation aids in decreasing ICP

What can spinal cord compression lead to?

Complex sensory, motor, and autonomic symptoms at and below level of insult

What are the cortical and medullary collecting tubules and their functions?

Cortical CT: (1) Principal Cells of DCT (secrete aldosterone which reabsorbs Na) and (2) Intercalated Cells (acid/base regulation: excretes H and secretes bicarb) Medullary CT: Part of collecting duct system in medulla of kidney. Main site for ADH (vasopressin) to regulate urine concentration

Do we want an increase in ICP or decrease?

Decrease

How does hypothermia affect CBF and CMRO2?

Decreases

How does dehydration impact ADH?

Dehydration -> increased ADH (vasopressin) secretion -> luminal membrane permeable to H2O -> H2O drawn out of collecting tubule -> goes through medulla -> CONCENTRATED urine

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

Clinical indications for loop diuretics

Edematous states such as CHF, cirrhosis, nephrotic syndrome, renal insufficiency. Hyperkalemia, anion overload, acute renal failure (this one is controversial)

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

In addition to the infusion, what other drugs should be ready for carotid endarterectomy?

Glycopylorrate and atropine for severe and moderate brady

hallmarks of autonomic hyperreflexia and other side effects

Hallmarks: hypertension and reflex bradycardia (carotid sinus) Other SE include LOC, seizures, arrhythmias. Precipitous increases in systemic BP can result in cerebral, retinal or subarachnoid hemorrhages and increased blood loss

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

Toxicity of loop diuretics

Hypokalemic Metabolic Alkalosis, Ototoxicity (diminished renal function or ototoxic drug use can lead to reversible hearing loss), Hyperuricemia, Hypomagnesemia, Allergy

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

Osmotic Diuretics

Increase UO by decreasing reabsorption of Na and H2O. ADH action is opposed.

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

Why should you avoid ketamine in neurocases?

It increases CBF by cerebrovasodilating, CSF volume and ICP.

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 brain shrinking agent is ideal for craniotomy for tumor resection?

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 should not be taken with loop diuretics? Why?

NSAIDS. They compete for weak acid secretions in proximal tubule. They reduce secretion and activity of loop diuretics

Loop Diuretics inhibit

NaCl reabsorption in the thick ascending limb of the loop of henle. Na reabsorption requires all 4 sites on Na-K-2Cl to be occupied. Loop diuretics compete with Cl for its site to inhibit NaCl reabsorption. In turn, this will increase K, Mg, Ca excretion

What infusion should be ready for carotid endarterectomy?

Neosynephrine and Nitroglycerine

What treats vasospasms associated with subarachnoid hemorrhage?

Nimodipine

What 2 drugs can you not give for neuroanesthesia and why?

Nitrous oxide and Ketamine because they both increase CBF, CMRO2, and ICP

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)

What diuretic can cause metabolic acidosis? How?

Potassium sparing diuretics. They inhibit aldosterone activity which increases Na excretion and K retention. Hyperkalemia can develop which impairs the kidney's ability to reabsorb bicarb leading to metabolic acidosis

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

Why do we avoid succinylcholine after 24 hours of spinal cord injury?

Provoke hyperkalemia during the initial 6 months s/p spinal cord transection

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

Is a rapid or slow emergence preferred to assess spinal cord function?

Rapid emergence

What is the primary function of the loop of henle?

Recovery of water and sodium from urine

Juxtaglomerular cells contain _____. Why is this important and how does it occur?

Renin. This is how blood pressure is regulated. The juxtamedullary apparatus is innervated by the SNS. Low blood pressure -> B1 adrenergic stimulation -> renin release -> afferent pressure change

Equation to maintain spinal cord oxygenation

SCPP = MAP - ISCP (CSF) * analogous to CPP

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 (1-2 days postop)

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

The spinal cord tapers into conus medullaris at ____, then forms _______

T12/L1-L2; cauda equina (horses tail)

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

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? How does this occur?

Thiazide diuretics. Thiazides are secreted in the proximal tubule. They block the NaCl transporter (NCC) and ENHANCE Ca reabsorption (PTH and VD)

What part of the loop of Henle is impermeable to H2O? What is reabsorbed here?

Thick Ascending Loop. Na and Cl reabsorbed in excess of H2O. Ca and Mg reabsorbed as well.

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

_______ and _______ connect the internal carotid and vertebral arteries

anterior and posterior communicating arteries

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

A decrease in CSF volume would tend to decrease

intracranial volume and ICP

EEG change for CBF below 10mL/100g/min

irreversible brain damage

EEG change for CPP below 25 mmHg

irreversible brain damage

if CPP is <50 mmHg what happens in the brain

ischemia and neurons will start to die