Kidney Flashcards
What is renal blood flow
20% of CO
What are proximal tubular cells susceptible to
Hypotension and hypoxia
Where is erthropoietin produced
Kidneys (px can be anaemic if CKD)
What are the functions of the kidneys
Excretion of electrolytes Clearance of waste products Receptor sites for hormones: ADH, aldosterone, ANP, PTH Gluconeogenesis Production of hormone: renin, vitamin D, erythropoietin, prostaglandins
What are pre-renal causes of AKI
Hypoperfusion - anything that causes shock, cardiac output
Renal artery stenosis
What are renal causes of AKI
Glomerulonephritis
Diabetes
PKD
Toxins - gentamycin, NSAIDs (reduce prostaglandin production, which reduce renal perfusion)
What are post renal causes of AKI
Anything in urinary tract
Takes 2 weeks for damage
Swollen kidney with no urine output is a medical emergency
What are the effects of AKI
Fluid overload
Oedema (pulmonary - breathlessness lying flat, pleural effusion, peripheral, sacral, ascites)
What investigations should be undertaken for AKI
Chest X-Ray
GFR
ECG for heart failure
Weight change
How is hyperkalameia treated
Hyperkalaemia: Treat with calcium gluconate, then insulin (pushes potassium into cells), or calcium resonium for long term treatment. Dialysis.
What are the ECG signs for different hyperkalameia
K 5.5-6.5 - Peaked T waves, prolonged PR segment
K 6.5-8 - Loss of P wave, prolonged QRS complex, ST segment elevation, ectopic beats and escape rhythms
K > 8 - Progressive widening of QRS complex, sine wave, VF, asystole, axis deviations, bundle branch block, fascicular blocks
What are signs of metabolic acidosis
Metabolic acidosis: exacerbates potassium issues Typical ABGs pH > 7.3 pCO2 Low pO2 normal to high HCO3 low
What is uraemia
Retention of metabolic waste products (sulphate, urea, ammonia, creatinine, phosphate)
What are the symptoms of metabolic acidosis
breathless, tachypnoeic, nausea, non-specifically unwell
What are the effects of uraemia
Pericarditis, pleurisy, encephalopathy
How is AKI diagnosed
Serum creatinine (only rises after losing more than 50% of kidney function) >26.5 in less than 48 hours or rises to 1.5 fold from baseline in the preceding 7 days Urine output less than 0.5ml/kg/h for 6 hours
What are life threatening complications of AKI
Life threatening pulmonary oedema Severe metabolic acidosis Severe hyperkalaemia Uraemic pericarditis Uraemic encephalopathy
Where are the insertion sites for dual lumen catheters for RRT
Insertion sites:
Internal jugular vein
Femoral vein
Subclavian vein
What is ideal body water composition
TBW = 60% ideal
40% intracellular
20% extracellular (15 interstitial fluid and 5 intravascular)
What is thirst stimualated by
Increases in plasma osmolality of 1-2% (normally between 280-300)
Decline in plasma volume of 10-15%
Baroreceptor input, angiotensin II
What is ADH and what does it co
Binds to V2 receptors on basolateral membrane of principle membrane along distal convoluted tubules and increases AQP2 expression of luminal membrane
Leads to arteriole vasoconstriction
What is ANP
Primarily released from atria - in response to volume expansion
What is BNP
Released by ventricles - in response to stretch
What do ANP and BNP promote
Dilatation of afferent arterioles and constrict the efferent arterioles (higher pressure in glomerulus and increase GF)
Reduce Na reabsorption in the DCT
Inhibit renin secretion
inhibit renal sympathetic tone
What is hyponatremia
Na<135 mmol
How does hyponatremia occur
Results from intake and subsequent retention of water. Excess of water in relation to Na - impairment in renal water excretion, most often due to an inability to suppress ADH secretion
Depletion of total body Na in excess of concurrent body water losses
What are the 3 classifications of hyponatremia
Hypovolaemia
Euvolaemia (urine Na >30 mmol/L)
Hypervolaemia
What are the causes of hypovalaemic hyponatremia
Extrarenal losses (urine Na<25mmol) Dermal losses GI losses 3rd space loss (pancreatitis0 Renal losses (urine Na>30mmol/L) Diuretic therapy Cerebral salt wasting Primary adrenal insufficiency
What are the causes of euvolaemic hyponatremia
Water intoxication - primary polydipsia, excess IV hypotonic fluids Hypothyroidism Hypopituitarism Pregnancy SIADH
What are the causes of hypervolaemia hyponatremia
Urine Na < 25mmol Congestive cardiac dysfunction Cirrhosis with ascites Nephrotic syndrome Urine Na > 30 mmol/L - chronic kidney disease
What is SIADH
Syndrome of inappropriate antidiuretic hormone secretion is characterized by excessive unsuppressible release of antidiuretic hormone (ADH) either from the posterior pituitary gland, or an abnormal non-pituitary source. Unsuppressed ADH causes an unrelenting increase in solute-free water being returned by the tubules of the kidney to the venous circulation
What is the treatment for hypovolemia hyponatremia
Correct volume depletion e.g. IV 0.9% saline
What is the treatment for euvolemia hyponatremia
Treat underlying cause, fluid restriction
What is the treatment for hypervolemia hyponatremia
Treat underlying cause, fluid restriction (vasopressin receptor antagonist)
What occurs in the brain in hyponatremia
Osmotic gradient between EC and IC fluid within the brain: water moves into cells and raises intracranial pressure due to oedema - neuro symptoms
When is agressive therapy for hyponatremia indicated
Severe symptoms
Acute hyponatremia
Goal - raise serum Na by 4-6 mmol/L over few hours, no more than 8 mmol/L/day
Hypertonic 3%
What is the risk of rapid correction in hyponatremia
Risk of central pontine myelinolysis - damage to oligodendrocytes
What is hyperatremia
Hypernatremia Na > 145mmol/L
From net water loss or hypertonic Na gain
Increase in plasma tonicity pulls water out of cells ,resulting in a decrease in intracellular volume
What is severe hyperatremia
Na > 145 mmol/L
What are the symtpoms of hyperatremia
Thirst, anorexia, weakness, stupor, seizures, coma
What are the two types of hyperatremia
Unreplaced water loss and sodium overload
What is unreplaced water loss hyperatremia caused by
Insensible and sweat losses GI losses Central diabetes insipidus Nephrogenic diabetes insipidus Osmotic diuresis (high glucose) Poor water intake
What is sodium overload hyperatremia caused by
Admin of high salt load
Hyperaldosteronism
What is the treatment of chronic hyperatremia
treat underlying cause, use of hypotonic fluid (5% dextrose), lower Na by maximum of 10 mmol/L day
What is the treatment for acute hyperatremia
Hypotonic fluid, lower Na by 1-2 mmol/L per hour to restore Na levels within 24 hours. Acute increase in plasma Na can lead to irreversible neuro injury
What is hypokalemia
Hypokalaemia K<3.5 mmol/L
K enters the body via oral intake or IV, largely stored in the cells, then excreted in the urine
What the the 3 caues of hypokalaemia
Decreased K intake
Increased K entry into cells
Increased losses - GI/urine
What causes increased K entry into cells
Extracellualr pH rise Increased inslin Elevated b-adrenergic activity Hypothermia Drugs e.g. antipsychotics
What causes increased GI losses of K
Vomiting
Diarrhoea
Laxative abuse
What causes increased urinary losses of K
Diuretics
Priamry mineralocorticoid excess
Renal tubular acidosis
Drugs .e.g Amphotericin B
What are the ECG changes in hypokalaemia
Flat T waves U waves ST depression PR interval prolonged Prolonged QT interval
What is the treatment for hypokalemia
Correct Mg levels
K replacement
If IV maximum 10-20 mmol/hr and cardiac monitoring
What is hyperkalemia
K>5.5
What are the two causes for hyperkalemia
Increased release from cells
Reduced urinary excretion
What are the causes of increased K release from cells
Pseduohyperkalemia Metabolic acidosis Insulin deficiency Increased tissue catabolism Beta blockers Exercise Hyperkaelmic periodic paralysis
What are reduced urinary excretion causes of hyperkalemia
Acute and chronic kidney disease
Reduced aldosterone secretion
Reduced response to aldosterone
What are the symptoms of hyperkalemia
Paraesthesia
Muscle weakness
Arrhythmias
What are the ECG changes of hyperkalemia
any ECG changes are medical emergencies Tall peaked T waves Shortened QT interval PR interval lengthening QRS widen P waves disappear - Sine wave
What is the treatment for hyperkalemia
IV calcium gluconate - antagonise membrane action of high K
IV insulin with glucose - drive K into cells
Remove K from body: consider loop diuretics
Consider haemodialysis
Other therapies to drive K into cells:
Sodium bicarbonate, beta agonists
What are symptoms of hypovolemia
GI losses, thirst, lethargy, postural dizziness, reduced urine volume, confusion
What are examination findings of hypovolemia
pulse is fast and weak, BP postural drop > 20mmHg, loss of skin turgor, sunken eyes, dry mucous membranes
What are symptoms of hypervolemia
breathlessness, peripheral oedema, weight gain, abdominal bloating, confusion
What are examination findings of hypervolemia
Pulse - can be fast, bounding BP can be high, can be low Skin turgor generally maintained Peripheral oedema JVP can be elevated Can have ascites