Kidney Liver Endocrine Flashcards
Serum osmolarity
2 [Na+] + (glucose/18) + (BUN/2.8)
Where is ADH produced
Supraoptic and paraventricular nuclei of hypothalamus
RELEASED by posterior pituitary gland
Where is angiotensinogen produced?
Liver
Renin converts angiotensinogen to Angiotensin I in the systemic circulation
Where is ACE produced?
Lung
Converts ang I to ang II
What does AT II do?
Stimulates aldosterone release from the zona glomerulosa in the adrenal glands, also a v potent vasoconstrictor
What’s in the medulla?
Loops of Henle and collecting ducts
What’s in the cortex?
Most of the nephron: glomerulus, Bowmans capsule, proximal and distal tubules
What’s the difference between aldosterone and ADH?
Aldosterone controls extracellular fluid volume: Na+ and H20 are reabsorbed together—> ↑ blood volume but doesn’t change osmolarity —> Na+, H20 reabsorption, K+ excretion
ADH (vasopressin) controls plasma osmolarity: H20 is reabsorbed but Na+ is not
What makes the kidney release EPO? What does EPO do after it’s released?
- inadequate 02 delivery to kidney: anemia, hypovolemia, hypoxia
- stimulates stem cells in bone marrow to produce erythrocytes
What 3 things induce renin release?
- ↓ renal perfusion pressure
- SNS activation (beta 1)
- Tubuloglomerular feedback (↓ Na+ and Cl- in distal tubule)
Compare D1 and D2 receptors
D1: kidney, splanchnic circulation: gs receptor
D2: presynaptic adrenergic nerve terminal: gi receptor
Renal blood flow
650mL/min to each kidney or 20-25% of CO
Afferent → glomerular capillary bed → efferent → peritubular capillary bed
- Of blood delivered to kidney only 20% filtered at glomerulus (180L/day), call this ultrafiltrate
- 99% ultrafiltrate reabsorbed after filtration
GFR
125mL/min
Filtration fraction
20% of renal blood flow (125/650)
Fraction of ultrafiltrate excreted as urine
1%
Best estimation of glomerular filtration rate?
Creatinine clearance (mL/min)
Normal 95-150mL/min
Mild dysfunction: 50-80
Moderate dysfunction: 10-25
Very f’d up: <10mL/min
GFR calculation
(140-age) x (weight in kg) / (serum crt x 72)
For a woman, multiply the answer by 0.85
Coags and renal disease
ESRD can have long bleeding time even with normal platelet, PT, PTT values because uremia impairs platelet function
Treatment = desmopressin (replenishes vWF), can do cryo, but has viral risk
How much renal blood flow is filtered at the glomerulus? Where does the rest go?
RBF = 1000-1250mL/min GFR = 125mL/min or ~20% RBF
So filtration fraction is 20% - means 20% is filtered by the glomerulus and 80% is delivered to peritubular capillaries
MOA of fenoldapam?
Selective Da1 receptor antagonist, ↑ RBF
Low dose 0.1-0.2mcg/kg/min renal vasodilator ↑ RBF, GFR, and facilitates sodium excretion without affecting ABP, may offer renal protection during aortic surgery or CPB
Where do carbonic anydrase diuretics work? Use?
Proximal tubule (net loss of bicarbonate and sodium, net gain of H+ and Cl-)
used for open angle glaucoma, altitude sickness, central sleep apnea syndrome
SE: metabolic acidosis, hypokalemia
Where do osmotic diuretics work?
Sugars that undergo filtration but not reabsorption - proximal tubule is main site and loop of Henle (inhibit water reabsorption)
Where do loop diuretics work and how
- medullary region of the thick portion of ascending loop of Henle
- poison the Na/K/2Cl transporter so a ton of Na remains in distal tubule causing a ton of dilute urine to be excreted
Location of action of thiazide diuretics
Distal tubule (inhibit the Na/Cl transporter there)
Tests of GFR and normal values
BUN 10-20mg/dL
Creatinine 0.7-1.5mg/dL
Creatinine clearance 110-150mL/min
All measure glomerular function
Tests of tubular function
Fractional excretion of Na+ (1-3%)
Urine osmolarity 65-1400mOsm/L
Urine sodium conc 130-260mEq/day
Urine spec gravity 1.003-1.030
Which hormones are produced by the kidneys?
EPO
Calcitriol (1,25[OH]2) = active D3, under control of PTH
Prostaglandins
- PgE2 and PgI2 vasodilate renal arteries
- TxA2 constricts
ANS receptors in kidneys?
A2: diuresis
B1: renin release
Aldosterone: where it’s made, what it does, what triggers release
-Produced in the zone glomerulosa of adrenal gland.
↑ Na/K/ATPase in distal tubules and collecting ducts
→ facilitates Na+ and H20 absorption and K+ excretion
Release triggered by:
- RASS stim
- Hyponatremia
- Hyperkalemia
ADH
PRODUCED by hypothalamus, RELEASED by posterior pituitary
Controls osmolarity
V1 (qi) receptor → potent vasoconstriction
V2 (qs) receptor → ↑ aquaporin-2 channels in collecting ducts
Lab tests for liver synthetic function
PT, INR, albumin
Lab tests for hepatocellular injury
AST, ALT, GST
Lab tests for biliary obstruction
Alk phosphatase and GGTP (GGTP is more specific)
Pure glucocorticoids
Decadron
Betamethasone
Triamcinolone
(Anti inflammatory + metabolic)
Pure mineralocorticoids
Aldosterone (sodium retention, potassium excretion)
TX thyroid storm
Block synthesis (methimazole, carbimazole, PTU, potassium) Block release (radioactive iodine, potassium iodide) Block T4 → T3 conversion (PTU, propranolol) Beta blocker (propranolol, esmolol)
DON’T give aspirin - it helps fever but it can ↑ free fraction T4 and worsen the situation.
When is postoperative hypocalcemia usually evident with inadvertent parathyroid removal
24-48 hrs
Happens sometimes after thyroidectomy
Best steroid for orthostatic hypotension
Fludrocortisone has mineralocorticoid properties 125X cortisol
↑ intravascular volume by promoting salt retention, can help chronic orthostatic hypotension
Absolute CI to ECSWL
Pregnancy Bleeding risk (coagulopathy or anticoagulation)
Compelling indicators of renal injury
↑ serum creatinine 100%
OU <0.5mL/kg/hr x 12 hrs
↓ GFR >50%
Compelling indicators of renal failure
↑ serum creatinine 200% or >4mg/dL
↓ GFR >75%
UO <0.3ml/kg/hr x 24 hrs or anuria x 12 hrs
TX uremic bleeding
Desmopressin is first line
Can also give cryo but ↑ risk viral transmission
↑ bleeding time but other coags normal
Hepatic blood flow
30% CO (about 1500mL)
Supplied by portal vein and hepatic artery
Portal vein=75% flow, 50% 02
Aorta → splanchnic organs → portal vein → liver
Hepatic artery=25%flow, 50%02
Aorta → hepatic artery → liver
Effects of anesthesia on liver blood flow
Induction of GA can → ↓ liver blood flow 30-50%
Synthetic proteins produced by liver
Since the liver produces so many proteins its easier to remember what it DOES NOT produce
- immunoglobulins :(produced by humoral immune system)
- vWF, factor III (tissue factor) : produced by vascular endothelial cells
Factor VIII is made in the liver but it’s made by liver sinusoidal cells and endothelial cells, so it’s NOT made by hepatocytes
All other clotting/lysis factors and plasma proteins are made by hepatocytes
What is bilirubin an indicator of
Hepatic clearance
It’s ↑ in prehepatic, intrahepatic, and cholestatic dysfunction
which IA preserves hepatic blood flow the best
Isoflurane
Etiologies of cirrhosis
ETOH Alpha 1 antitrypsin deficiency Biliary obstruction Chronic hepatitis Hemochromatosis R sided HF Wilson disease (genetic copper accumulation)
MELD, Child-Pugh
MELD: Bilrubin, INR, serum creatinine
Child-Pugh: albumin ascites bilirubin encephalopathy PT
CV manifestations of liver disease
↓ SVR, BP ↑ CO ↑ RAAS, ↑ Blood volume ↑ SV02 Diastolic dysfunction ↑ Vd (due to ↓ osmotic pressure)
Respiratory manifestations of liver disease
Restrictive defect ↓ compliance Respiratory alkalosis Hepatopulmonary syndrome Portopulmonary HTN
TIPS
Shunts blood from portal vein to hepatic vein (outflow vessel)
Hemorrhage is a high risk
Bile -site, storage, release
Made by hepatocytes, stored by gallbladder, released into duodenum through ampulla of Valter
Absorbs DAKE (fat soluble vitamins) Excretory pathway for bilirubin and other products of metabolism Alkalizes duodenum
Etiologies of SIADH
TBI (most common)
Cancer
No cancer lung disease
Carbamazepine
Fluid overloaded dilutional hyponatremia
Etiologies of DI
Pituitary surgery (most common)
TBI
SAH
Polyuria
Give DDAVP or vasopressin, supportive
How does cortisol mitigate the inflammatory cascade
Stabilizes lysosomal membranes and ↓ cytokine release
Drug of choice for Addison’s
Prednisone - it’s an analogue of cortisol. Glucocorticoid : mineralocorticoid is 4: 0.8
Who should get stress dose steroids
Anyone who has gotten 5->20mg prednisone day for >3 weeks
Stress hydrocortisone dosing
Minor surgery (hernia, colonoscopy) 25mg IV Moderate surgery (colon, joint, TAH) 50-75mg, taper over 1-2 days Major surgery (CV, thoracic, liver, whipple) 100-150mg IV taper over 1-2 days
Sulfonylurea oral diabetes drugs
All end in “ide”
Avoid if sulfa allergy, carry risk of hypoglycemia
When does NPH peak
4-12 hrs
2 hr onset
When does regular insulin peak
2-4 hrs
30 min onset
Signs of excess glucocorticoid secretion
Osteoporosis Muscle weakness Weight gain Mood changes Immunosuppression
Signs of excess mineralocorticoid activity
HTN
Hypokalemia
Metabolic alkalosis
Etiologies of hypoalbuminemia
Infection Nephrotic syndrome Malignancy Burn Malnutrition Liver disease