Renal Pathophys Flashcards
Potassium
Secretion/Excretion
- In kidneys, the majority of filtered K+ is resorbed in the proximal tubular system
- Selective secretion or absorption in the distal tubule determines net K+ (limit of renal K+ excretion 10 mEq/L)
- Excretion affected by circulating Aldosterone, cellular and extracellular K+, tubular urine flow rates, & acid-base disturbances
Misc Info
* 98% of K+ is intracellular
* 95% is excreted in urine; rest is swewat/feces
Potassium
Function
Na+/K+ ATPase
* nerve transmission
* skeletal msk contraction
* cardiac msk function
* renal/fluid ion balance
K+ Channels
* nerve action potentials
Potassium
Tx Hypokalemia (when to use what)
- Orally: preferred; use in normal renal function; do not exceed 40 mEq/hr
- IV: if emergent; do not exceed 10 mEq/hr; repeat as often as necessary; EKG monitor (mandatory if rate >10 mEq/hr); avoid dextrose solutions (will drop K level)
- correct hypokalemia + hypocalcemia together
Chloride
normal levels
98-110 mEq/L
Calcium
normal value + how to correct
- normal: 8.5-10.5 mEq/L
- must correct for albumin when pt is hypoalbuminemic because 40% is bound to albumin
- corrected: serum Ca2+ = measure Ca 2+ + [0.8 x (normal albumin-measured albumin)]
Calcium
function of calcium
- Neural signaling
- Bone mineralization
- Cardiac function
- Skeletal muscle contraction
- Digestive system function
Calcium
factors affecting resorption
PTH or metabolic alkalosis
Calcium
pathophys of calcium
- Stimulates osteoclasts to break down bone – releasing calcium and phosphorus
- Increases reabsorption of calcium by kidneys
- Blocks reabsorption of phosphate by kidneys, leading to urinary phosphate loss.
- Increases conversion of inactive to active 1,25 vitamin D (which then increases calcium absorption from gut)
Hypocalcemia
Trousseau vs Chvostek
- Trousseau: Carpal spasm elicited by inflation of BP cuff to 20 mmHg above systolic pressure for 3 min
- Chvostek: Twitching of circumoral muscles in response to tapping facial nerve anterior to ear
Calcium
how does half or full NS help hypercalcemia
- Enhances urinary calcium excretion
- Saline diuresis lead to hypokalemia, hypomagnesemia, or other electrolyte imbalance
- CAUTION: avoid fluid overload
Magnesium
generally describe
- 2nd most abundant cation of the intracellular fluid
- Mg++ is tightly regulated by the gut, kidney, and bone.
Function
* Activates enzymes
* ATP function in combination with phosphate
* Signal transduction pathways
* Nerve transmission
Phosphorus
generally describe
- Normal 3 to 4.5 mg/dL
- Total body content: 85% in bone, 14% intracellular, and 1% extracellular
- Daily intake is 800 to 1500 mg
- Present in many foods: dairy products, meats, grains
Kidney secretes phosphorus
* Most filtered at the glomerulus
* PTH increases renal phosphate excretion
* Vitamin D enhances intestinal phosphate absorption
Phosphorus
pseudohyperphosphatemia
Pseudohyperphosphatemia may occur in hemolytic specimens or hyperglobulinemic states (ie, multiple myeloma)
functions of the kidney
- Regulation of ionic composition (Sodium, potassium, calcium, chloride, phosphate)
- Regulation of blood pH, osmolarity, and glucose
- Regulation of blood volume (Conserving or eliminating water)
- Regulation of blood pressure (Secreting renin)
- Release of erythropoietin & calcitriol
- Excretion of wastes (Nitrogenous waste products (ammonia, uric acid, urea, creatinine, and amino acids), excess quantities of salts and water
Kidneys General Anatomy/Physio
describe erythropoietin and calcitriol
- Erythropoietin: essential hormone secreted by the kidneys for red blood cell production in the none marrow
- Calcitriol: active form of vitamin D; also known as 1,25-dihydroxycholecalciferol
Kidneys General Anatomy/Physio
internal anatomy of kidney
Renal parenchyma
* Glandular tissue that forms urine
* Divided into 2 sections
Renal cortex
* Superficial layer of the kidney; measures ~1 cm
* Extension of the cortex known as renal columns
Renal medulla
* Inner section consisting of 6-18 conical renal pyramids
Renal pyramid
* Blunt end called the papilla that is nestled in a cup called a minor calyx for urine collection
Kidneys General Anatomy/Physio
nephrons
- Functional unit of the kidney
- ~1.2 million per kidney
- Composed of: Blood vessels, renal corpuscle, and renal tubule
Cortical nephrons
* 70-80% of the nephrons
* Located close to the kidney surface
Juxtamedullary nephrons
* 20-30% of the nephrons
* Located close to the medulla
Kidneys General Anatomy/Physio
major function of the kidney
- Filter blood plasma and separate wastes from the useful chemicals
- Eliminates the wastes in urine while returning the useful chemicals to the bloodstream
Kidneys General Anatomy/Physio
Renal Corpuscle
- Component of each nephron
- Site where blood filtration begins (Passive process by high hydrostatic pressure of the glomerular capillaries)
- Consists of: Glomerulus (cluster of capillaries), Bowman’s capsule, Two-layered capsule that encloses the glomerulus
Blood Flow
* Blood flows into the glomerulus via the afferent arterioles → water and solutes pass through the capillary endothelium, through the basement membrane, and through the epithelium → Bowman’s space → renal tubule
* Remaining blood leaves the glomerulus through efferent arterioles
Kidneys General Anatomy/Physio
Glomerular Filtration Rate (GFR)
- The volume of fluid filtered by the kidneys in a minute
- Measures kidney function
Dependent upon:
* The net filtration pressure (Vasodilation of the afferent arterioles mediated by prostaglandins; Vasoconstriction of the efferent arterioles mediated by angiotensin II)
* Available surface area for filtration
* Filtration membrane permeability
Kidneys General Anatomy/Physio
Renin-Angiotensin-Aldosterone (RAAS) system
- angiotensinogen (liver)
- renin (kidney)- converts-
- angiotensin I
- antiongensin converting enzyme (ACE) - (lungs/kidney) - converts-
- angiotensin II
- systemic effects
plays central role in regulation of renal blood flow
Kidneys General Anatomy/Physio
RAAS end system impacts
- vasoconstricts the glomerular arterioles; greater effect on the efferent arterioles than the afferent arterioles → increased glomerular filtration pressure
- Increased circulating volume from the affects of aldosterone → increased blood pressure and renal perfusion
- stimulates the release of antidiuretic hormone (ADH), which will reabsorb water from the collecting ducts → increased circulating blood volume and renal perfusion
Kidneys General Anatomy/Physio
Renal Tubule
- Duct that leads away from the glomerular capsule
- Each has a unique absorptive properties
Divided into 4 regions:
* Proximal convoluted tubule (PCT)
* Nephron loop
* Distal convoluted tubule (DCT)
* Collecting duct
AKI
epidemiology
- 7% hosp patients
- 2/3 of ICU pts (50-70% mortality if associated w/ sepsis or multi-organ failure)
AKI
pre-renal causes
- Most common type of AKI (70% of community-acquired cases)
Caused by decreased renal perfusion
* Reduced circulating volume (GI losses, blood loss, diuretic use, osmotic diuresis – DKA, insensible loss – burns)
* Reduced cardiac output (heart failure)
* Systemic vasodilation (septic shock)
* Medications
* ACE inhibitors, ARBs, NSAIDs
* Obstruction of the renal artery (thrombosis/embolus, stenosis, or aneurysm)
AKI
NSAID vs ACE/ARB impacts on kidneys
NSAIDs
* Vasodilation of the afferent arterioles mediated by prostaglandins
* NSAIDs block the production of prostaglandins → vasoconstriction and possible AKI
ACE/ARB
* Vasoconstriction of the efferent arterioles mediated by angiotensin II
* ACEi/ARBs block the effects of angiotensin II (vasoconstriction) → vasodilation of the efferent arterioles (renal protective)
* In patients with renal artery stenosis, the introduction of an ACEi/ARBs can lead to a drop in glomerular filtration pressure
AKI
Intrinsic/Intra-renal causes
- Caused by direct damage to the glomeruli and/or tubulointerstitial structures
Acute tubularnecrosis(ATN)
* Damage to the tubular cells
* Caused by a lack of blood flow to the kidneys and nephrotoxic agents
Acute interstitial nephritis
* Inflammatory cell infiltration into the kidney interstitium
* Caused by medications,infections, orautoimmune diseases
Vascular disease
* Atherosclerosis and vasculitis
Glomerular disease
* Glomerulonephritis (presents withhematuria)
* nephrotic syndrome(presents withproteinuria)
AKI
nephrotoxic agents
- aminoglycosides
- vancomycin
- cisplatin
- heavy metals (lead, mercury)
- ethylene glycol (anti-freeze)
- radiocontrast
- lithium
AKI
post-renal causes
- Caused by inadequate drainage of urine distal to the kidneys (obstruction) leading to back pressure on the kidneys and hydronephrosis
- May occur at any point in its course from therenal pelvisto theurethra
Causes of obstruction
* Urinary calculi
* Benign prostatichyperplasia (BPH) or prostate cancer
* Bladder outlet obstruction
* Urethral stricture
* Gynecologic tumors (ovarian cancer, uterinefibroids,cervical cancer)
AKI
effects of AKI on electrolytes & acid-base balance
Hyperkalemia
* Due to decreased renal excretion ofpotassium
* Increases theprobability ofcardiac arrhythmias
Hyperphosphatemia
* Due to decreased renal excretion ofphosphate
Metabolic acidosis
* Inability of thekidneysto excreteacids
* Exacerbateshyperkalemia
* Increases theprobabilityofcardiac arrhythmias
Rhabdo
causes
traumatic, exertional, non-exertional
Traumatic (msk compression)
* Crush injuries
* Victims of prolonged restraint, torture, or physical abuse
* Surgical procedure with prolonged muscle compression
* Acute lower-limb compartment syndrome
* High-voltage electrical injury
Non-Traumatic, Exertional
* marked physical exertion when 1+ risk factors is present: sickle cell trait, physically untrained, hot/humid conditions, impaired heat loss (ex: anti-cholinergic meds, heavy football equiment)
* pathologic hyperkinetic states: grand mal seizures, delirium tremens (severe type of EtOH withdrawal), psychotic agitation, amphetamine OD
Non-Traumatic, Non-Exertional
* Prolonged immobilization
* Alcohol use
* Drug use: Illicit (heroin, cocaine, LSD, methadone) or Prescription (statins, colchicine, daptomycin)
* Toxins: Snake venom, mushroom poisoning, carbon monoxide
* Infections: Viral (influenza A & B, coxsackievirus)
* Inflammatory myopathies (dermatomyositis)
* Electrolyte abnormalities: Hypokalemia or Hypophosphatemia
Rhabdo
pathogenesis
- Muscle injury
- Influx of extracellular sodium and calcium into the myocytes; water follows sodium distorting the integrity of the intracellular space
- ↑ intracellular calcium causes a sustained myofibril contraction → ATP depletion within these cells
- Activation of lipases and proteases → damage of the myocyte cellular membrane
- Release of intracellular components (creatine kinase (CK), myoglobin, potassium, phosphate) that enter the bloodstream
- Myoglobinuria and electrolyte abnormalities cause end-organ complications (AKI most common systemic complication)
Rhabdo
electrolyte balance
Intracellular fluid
* Potassium (K⁺) – main cation
* Magnesium (Mg2⁺)
* Proteins
* Phosphates (HPO₄²-/H₂PO₄-) – main anion
* Electrically balance the intracellular cations along with the negatively chargedproteins
* MP3 (Mg, potassium, protein, phosphate) Inside
Extracellular fluid
* Sodium (Na⁺) – main cation
* Controls ECF volume and water distribution in the body – water follows sodium
* Calcium (Ca²⁺)
* Chloride (Cl-) and Bicarbonate (HCO₃-):Chloride is the most abundant anion in the ECF
* Anions balance the extracellular cations