Diuretics and Anesthesia Flashcards by John Caroccio

What are the two major pathways of natriuretic peptide (NPs) actions?

Vasodilator effects

2. Renals effects that leads to natriuresis and diuresis.

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What are NP’s direct effects on veins?

Dilate veins (increase venous compliance and decrease CVP)

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What are NP’s effect on cardiac output and how?

Reduce CO by decreasing ventricular preload

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What are NP’s affects on arteries?

Dilate arteries which decreases SVR and systemic arterial pressure

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How does NP affect the kidney?

Increasing glomerular filtration rate which produces natriuresis and diuresis

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What is natriuresis?

Increased sodium excretion

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What is the second renal action of NPs?

They decrease renin and therefore decrease angiotensin II and aldosterone

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T/F: NPs serve as a counter-regulatory system for the RAAS?

True

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What produces Atrial natriuretic peptide?

Atrial myocytes

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What is the stimuli for releasing ANP?

Atrial stretch

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Where is brain natriuretic peptide synthesized?

Ventricles of the brain

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What causes BNP to be released?

Atrial stretch, sympathetic stimulation, angiotensin II

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What are the 3 affects of ANP/BNP on the kidneys?

Decrease Renin
Decrease angiotensin II and aldosterone
Increase GFR

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What are NP’s affects on pulmonary capillary wedge pressure?

Reduced

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Diuretic definition:

A substance that increases the rate of urine volume output

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How do most clinicallty used diuretics act?

By decreasing the rate of Na+ reabsorption from the tubules which causes Na+ output to increase which then results in diuresis

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What are common clinical use for diuretics?

To decrease ECF volume, to treat edema, CHF, or hypertension

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What eventually overrides the effects of diuretics?

Decrease ECF leads to decreased MAP leads to decreased GFR leads to increased Renin and angiotensin II

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Site of action for K+ sparing diuretics?

Collecting duct

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Site of action for Loop diuretics?

Loop of Henle (ascending thick mostly)

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Site of action for thiazides?

Distal convoluted tubules

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Site of action for carbonic anhydrase inhibitors?

Proximal convoluted tubules

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Example of osmotic diuretic?

Mannitol (or urea)

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What is mechanism of action of mannitol?

These substances injected into the bloodstream are filtered and not easily reabsorbed and ultimately they draw fluid into the tubules (increasing urine output)

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Is glucose a diuretic?

Yes and no. For diabetics, glucose can act as a diuretic when spilling over into the urine resulting in increased urine output

3 examples of loop diuretics?

furosemide, bumetanide, ethacrynic acid

What is mechanism of action for loop diuretics?

Inhibit the Na-2Cl-K cotransporter in the TAL of the Henle's Loop.

What is the most commonly used diuretic?

Thiazide diuretics

Example of thiazide diuretic

hydrochlorothiazide (HCTZ)

What is mechanism of action for thiazide diuretics?

These agents inhibit sodium chloride reabsorption in the early distal tubule

Example of Carbonic Anhydrase Inhibitor:

Acetazolamide (diamox)

What is mechanism of cation for carbonic anhydrase inhibitors?

Reduce reabsorption of Na+ in the proximal convoluted tubule by decreasing HCO3

What is the disadvantage of using carbonic anhydrase inhibitors?

It causes acidosis through HCO3 loss in the urine

What is main reason for use of carbonic anhydrase inhibitors?

Glaucoma

What is another name for Potassium-sparing diuretics?

Aldosterone Antagonists

What is an example of a potassium sparing diuretic?

Aldactone

What is mechanism of action for potassium sparing diuretics?

Decrease reabsorption of Na+ and decreases K+ secretion by competing for aldosterone binding sites in the distal segment of the distal tubule;

Aldactone is often used in conjunction with what other diuretics to prevent hypokalemia?

1. Thiazides | 2. Loop diuretics

Example of Na+ channel blockers:

Amiloride and triamterene

What are the two main categories of Renal Failure?

1. Acute Kidney Injury (AKI) | 2. Chronic Kidney Injury (CKD).

T/F: CKD and AKI are both completely reversible with proper therapy?

False; CKD is irreversible

What are the three main categories of Acute Renal Failure?

1. Pre-renal 2. Intra-renal 3. Post-renal

Which ARF is typically caused by toxins, infections, autoimmune diseases. and direct renal injury?

Intra-renal

What are common causes of pre-renal ARF?

Heart failure, hypovolemia (kidney not getting enough blood flow and becomes ischemic).

What are common causes of post-renal ARF?

Stones, urethtral valves, tied off ureter, kinked foley.

At what percent of functioning nephrons are symptomes of Chronic Kidney disease present?

Once functioning nephrons decreases to at least 70% below normal

What is the definition of CKD?

Kidney damage or decreased kidney function that persists for at least 3 months

At what point can relatively normal blood concentration of electrolytes and body fluid volumes be maintained until?

Once functioning nephrons decreases below 20-25% of normal

What are mechanisms of injury leading to Chronic Renal Failure?

1. Injury to renal vasculature 2. Glomerulonephritis 3. Infection 4. Nephrotic syndrome

What is vesicoureteral reflux?

When the bladder wall fails to occlude the ureter during micturation and contaminated urine from the lower urinary tract is propelled retrograde into the kidney

What is nephrotic syndrome?

Condition where large amounts of protein are lost in the urine due to destruction of or loss of negative charge on the capillary basement membrane in the glomerulus

Why does anemia occur in ESRD?

Anemia occurs because of decreased synthesis by the kidney of erythropoietin (which acts to stimulate RBC production in bone marrow).

What is the number one cause of DB and HTN and therefore most important risk factor for ESRD?

Obesity

What are some other effects of renal failure?

1. Abnormal glucose tolerance 2. Platelet and WBC dysfunctiom 3. Hypersecretion of gastric acid increases risk of ulcers 4. Autonomic neuropathy can slow gastric emptying 5. Peripheral neuropathy is common

How does renal failure cause HTN?

Decrease water and sodium excretion promotes HTN

T/F: HTN can only occur if both kidneys have ischemia?

False; one kidney will increase renin and angiotensin II to increase BP

What are the two main ways of hypertension control from renal disease?

1. Increasing GFR | 2. Decreasing tubular reabsorption

What does the rate of movement of solute across the membrane depend on (dialysis)?

1. Concentration gradient 2. Permeability and surface area 3. Length of time

Indications for dialysis?

1. Fluid overload 2. Hyperkalemia 3. Severe acidosis 4. Metabolic encephalopathy 5. Pericarditis 6. Coagulopathy 7. Refractory GI symptoms 8. Drug toxicity

How much does GFR decrease with age?

Decrease by 5% per decade after age 20

Barbiturates and renal function?

Pt more susceptible to these agents probably because of decreased protein binding (more free drug available)

What does poor renal function have on propofol/ketamine/etomidate?

No significant difference

Benzodiazepines with renal failure?

May have additional sensitivity

Dexmedatomidine and renal failure?

Longer-lasting sedative

Opioids with renal failure?

Morphine/demerol/ hydromorphone have an accumulation of metabolites

NMBA to avoid with renal failure?

Pancuronium, pipecuronium, alcuronium, doxacurium, (mild concern with vec/roc and succ with K+>5.0)

Where is dexmedetomidine primarily metabolized?

Liver

What NMBA is drug of choice with renal failure and why?

Cisatracurium as it is degraded by Hoffman elimination

Which two volatile agents should we be cautious with in renal failure?

1. Enflurane | 2. Sevoflurane

Elective surgery: what is the K+ threshold to put off surgery until dialyzed?

>5.5 mEq/L

At Hamot, what is the typical waiting time after dialysis to do elective surgery?

6-8hrs after

Why is controlled ventilation advantageous for renal failure patients?

Will decrease the risk of respiratory acidosis which is not good in the setting of metabolic acidosis

What is mortality rate of post-op renal failure?

50%

What are precautions/treatments to prevent post-op renal failure?

1. Euvolemia 2. Prophylactic mannitol 3. Dopamine renal dosing

What is most common stone composition of kidney stones?

Calcium oxalate

What are pharmacologic treatment for kidney stones?

1. Toradol 2. Opioids 3. Alpha blocker (decrease ureter tone)

Where does tissue damage occur during ESWL?

At the air tissue interface so lung and intestine must be out of the way

When should ESWL shock wave be delivered?

20 ms after the r wave

What are most common causes of gout?

Diet rich in protein, fat, and alcohol