Hypocalcemia General Serum total Calcium < 8.5 or ionized <1.1 Ionized: <0.8 warrants treatment, <0.65 is critically low Corrected serum calcium is calculated by adding 0.8mg/dl x difference below the reference of 4.1 g/dl in albumin Pseudohypocalcemia Total Calcium is reduced due to decreased albumin but ionized calcium is normal Causes Hypoparathyroidism (MCC) Autoimmune Disease Malignant or infectious infiltrate (hemochromatosis or Wilson disease) Thyroidectomy DiGeorge Syndrome CaSR gene defect Thyroid Surgery (hypoparathyroidism), acute pancreatitis, sepsis, tumor lysis syndrome, Acute Alkalosis (increase in albumin binding calcium), Chelation (blood (citrate) transfusion, EDTA, Calcium binding Meds (Foscarnet, Citrate, Fluoroquinolones)) High Volume blood transfusion (citrate) Hepatic or renal failure at greatest risk CRRT, Leukapheresis, Plasmapheresis, Massive Transfusion Ethylene Glycol poisoning Magnesium abnormality (especially hypomagnesemia) Impaired 1,25-VitD production with Hyperphosphatemia from CKD MCC of acquired hypocalcemia Rhabdomyolysis/Tumor Lysis increase binding of phos and calcium Prostate/Breast Cancer Anticonvulsants (Phenytoin, Phenobarbital, Carbamazepine) INH, rifampin, pentamidine, aminoglycosides Loops Bisphosphonates, calcitonin, cisplatin, 5-FU Cinacalcet Symptoms Moderate: Peri-oral tingling, paresthesia, Tetany Hyperreflexia Muscle weakness, cramping, myalgias, fasiculations Chvostek Sign (facial spasm by tapping near the patient’s facial nerve) Trousseau Sign (carpopedal spasm when a sphygomometer is tightened on the arm for more than 3 minutes) Severe: Seizures, laryngospasm, confusion, bradycardia, decompensated HF Prodrome may be absent prior to death Hypotension, Heart block QT prolongation Slower influx means it takes longer for intracellular calcium to reach the threshold to close L-type Ca2+ channels, extending AP duration, extending QT Diagnosis: Remeasure and measure albumin for corrected calcium level < ionized calcium Magnesium and Phosphate Calcidiol (25-Hydroxy VitD) and Calcitriol (1,25-Hydroxy VitD) Low 25-Hydroxy VitD indicated VitD deficiency Low 1,25-Hydroxy VitD indicate renal failure, hypoparathyroidism Lipase CK if K+ and phos are elevated Measure PTH Hypocalcemia + Low/Normal PTH: Hypoparathyroidism Hypocalcemia + Elevated PTH: Renal Failure, VitD deficiency, PTH resistance, intravascular chelation Treatment 1) Symptoms Tetany, carpopedal spams, laryngospasm, long QT, seizures, arrythmias 2) QT prolongation without hypokalemia or hypomagnesemia 3) Severe Hypocalcemia (iCa2+ < 0.8) Don’t treat: Mild-moderate pts who are critically ill Hyperphosphatemia: increases precipitation of calcium phosphate (calciphylaxis) Ethylene glycol poisoning: calcium oxalate in the brain Ca2+ ≥7.5 g/dl: 1) Oral Calcium Carbonate 1-3g q6hr-q12hr > Calcium Citrate > Calcium Gluconate 2) Calcitriol (1,25-Dihydroxyvitamin D) 1000-4000IU per day Ca2+ <7.5 g/dl or severe: 1) IV Calcium Gluconate 2-3g peripheral > Calcium Chloride 1g Central Over 10-20 minutes, may need to repeat (slow via central IV) SE: Nausea, vomiting, hypertension, flushing, chest pain Pancreatitis/still falling: 1g Calcium gluconate over 60 minutes, q1hr prn Monitor for hypercalciuria (limits therapy) Add thiazide Teriparatide 20 nanograms BID rapidly eliminates hypocalcemia in acute post-surgical patients Dialysis vs binders may be preferred if Severe Hyperphosphatemia 100-200mg over 10-20mins (bolus) + slow infusion of 0.5-1 up to 2 mg/kg/hr as 10% calcium gluconate until Ca at 8-9 Chronic: VitD supplementation (50k weekly)