Hyperphosphatemia and hypophosphatemia Notes
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NOTES NOTES HYPERPHOSPHATEMIA & HYPOPHOSPHATEMIA GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Phosphate imbalances in blood ▫ Hyperphosphatemia: > 4.5mg/dL ▫ Hypophosphatemia: < 2.5mg/dL ▪ Phosphate intake; absorption through gastrointestinal (GI) tract; kidney excretion; transcellular shift; balance between uptake, release by bone tissue DIAGNOSIS LAB RESULTS ▪ Assess blood phosphate levels TREATMENT ▪ See individual disorders SIGNS & SYMPTOMS ▪ Mild: usually asymptomatic ▪ Severe: may be fatal Figure 115.1 Illustration depicting parathyroid hormone preventing reabsorption of phosphate and promoting reabsorption of calcium. 812 OSMOSIS.ORG
Chapter 115 Hyperphosphatemia & Hypophosphatemia HYPERPHOSPHATEMIA osms.it/hyperphosphatemia 1cm/0.39in below zygomatic process) ▫ Trousseau’s sign (blood pressure cuff occludes brachial artery, pressure on nerve leads to muscle spasm, ﬂexing wrist, metacarpophalangeal joints) ▫ Hyperreﬂexia ▫ Tingling around mouth ▫ Seizures ▫ Bone pain PATHOLOGY & CAUSES ▪ High phosphate levels in blood > 4.5mg/dL ▪ 70% of individuals with advanced chronic kidney disease ▫ Individuals with chronic kidney disease, hyperphosphatemia → secondary hyperparathyroidism, renal osteodystrophy → bones thin, weak ▪ Risk of metastatic calciﬁcation (e.g. kidney stones, nephrocalcinosis) CAUSES ▪ Decreased kidney excretion ▫ Decreased glomerular ﬁltration rate in acute/chronic kidney disease ▫ Hypoparathyroidism ▫ Pseudohypoparathyroidism ▫ Vitamin D intoxication: increased phosphate absorption through Gl tract ▪ Increased phosphate intake ▫ Only acute phosphate load (e.g. too much phosphate-based laxative) ▪ Transcellular shift ▫ Massive cell death (e.g. tumor lysis syndrome, rhabdomyolysis, crush injuries, massive hemolysis— intracellular phosphate released into bloodstream) ▫ Acidosis COMPLICATIONS ▪ Metastatic calciﬁcation ▪ Renal calcinosis SIGNS & SYMPTOMS ▪ Mild: asymptomatic ▪ Severe: hypocalcemia ▫ Tetany ▫ Chvostek’s sign (facial muscles twitch after facial nerve lightly ﬁnger tapped DIAGNOSIS LAB RESULTS ▪ ▪ ▪ ▪ ▪ ↑ phosphate ↓ calcium ↑ vitamin D ↓ parathyroid hormone ↑ urinary phosphate excretion OTHER DIAGNOSTICS ▪ History, physical examination TREATMENT MEDICATIONS ▪ Decrease phosphate absorbed from GI tract ▫ Phosphate binders (e.g. aluminium salts, calcium carbonate) ▪ Increase phosphate excretion ▫ Healthy kidneys: forced diuresis, intravenous (IV) saline, loop diuretic (furosemide) → overwhelm proximal convoluted tubule of nephron → unable to effectively reabsorb solutes (e.g. phosphates) ▫ Life-threatening hyperphosphatemia: dialysis OTHER INTERVENTIONS ▪ Decrease phosphate intake; avoid highphosphate foods (e.g. dairy, meat, soda) OSMOSIS.ORG 813
HYPOPHOSPHATEMIA osms.it/hypophosphatemia PATHOLOGY & CAUSES ▪ Low phosphate levels in blood < 2.5mg/dL CAUSES ▪ Increased kidney excretion ▫ Primary hyperparathyroidism ▫ Fanconi syndrome: proximal convoluted tubule loses capacity to reabsorb solutes (e.g. phosphates) ▪ Decreased intake, absorption through GI tract ▫ Low intake dietary phosphate (unusual) ▫ Medications impair absorption (e.g. antacids with aluminum/calcium/ magnesium) ▫ Alcohol use disorder → low dietary phosphate intake, vitamin D deﬁciency ▪ Transcellular shift ▫ Refeeding syndrome in severely malnourished individuals → hypokalemia, cardiac arrhythmias, neurologic problems ▫ Insulin treatment in diabetic ketoacidosis; insulin makes phosphate move from the bloodstream inside the cells ▫ Respiratory alkalosis RISK FACTORS ▪ Alcoholism, diabetes, sepsis COMPLICATIONS ▪ Rhabdomyolysis, kidney damage ▪ Chronic hypophosphatemia ▫ Osteomalacia (adults), rickets (children) 814 OSMOSIS.ORG SIGNS & SYMPTOMS ▪ Mild: asymptomatic ▪ Severe: ▫ Muscle weakness, respiratory/cardiac insufﬁciency ▫ Altered mental status ▫ Seizures DIAGNOSIS LAB RESULTS ▪ ▪ ▪ ▪ ↓ phosphate ↑ calcium ↓ vitamin D ↑ parathyroid hormone OTHER DIAGNOSTICS ▪ History, physical examination TREATMENT MEDICATIONS ▪ Replenish phosphates ▫ Oral administration, diet alone may sufﬁce ▫ IV for life-threatening hypophosphatemia OTHER INTERVENTIONS ▪ Avoid refeeding syndrome by gradually increasing caloric intake, supplements over several days
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