Pediatric emergency medicine trisk 719

findings in patients with neuromuscular instability include Trousseau sign and Chvostek sign A positive Trousseau sign is causing a carpopedal spasm by inflation of a sphygmomanometer above systolic blood pressure for minutes A positive Chvostek sign is contraction of the ipsilateral facial muscle induced by tapping of the facial nerve in front of the ear Of note, Chvostek sign may be present in up to 10% of normal subjects In addition to neuromuscular findings, acute hypocalcemia may result in significant cardiovascular disturbance, including hypotension, congestive heart failure, prolonged QT interval, and dysrhythmias Papilledema may also be present and resolves with correction of hypocalcemia Management Numerous forms of calcium salts are available, and therefore, attention to the salt form is critical when dosing to determine the elemental calcium dose Calcium may be provided by either oral supplementation or IV solution The appropriate choice is guided by pertinent clinical findings In general, IV calcium is indicated if the patient has prolonged QT, significant symptoms (tetany, seizures, carpopedal spasm), or acute decrease in serum corrected calcium to less than or equal to 7.5 mg/dL regardless of symptoms Oral supplementation is more appropriate when symptoms are absent or mild and corrected calcium is greater than or equal to 7.5 mg/dL In patients with asymptomatic chronic hypocalcemia associated with CKD, oral calcium supplementation is preferred with concomitant replacement of 1,25-dihydroxyvitamin D If hypocalcemia is associated with metabolic acidosis, correction of the acidosis will reduce the ionized calcium level Therefore, if metabolic acidosis is not causing clinical compromise, priority should be given to increasing the serum calcium If hypocalcemia is associated with severe hyperphosphatemia, the provision of calcium may result in the precipitation of calcium and phosphate in the tissues, a disorder known as calciphylaxis In patients with associated hypomagnesemia, magnesium supplements should be provided, as persistent hypomagnesemia will hinder the correction of hypocalcemia Prompt treatment of symptomatic or severe acute hypocalcemia should be initiated intravenously with either calcium chloride or calcium gluconate Central access is usually necessary for calcium chloride infusions, although peripheral infusions may be permissible in emergent situations Central access is also preferred for calcium gluconate, though this salt can be infused peripherally via a large vein The use of calcium gluconate is usually favored as it is less likely to result in tissue damage if extravasation occurs As concentrated forms are irritating to veins, calcium salts should be diluted in dextrose and water or saline The final concentration of calcium gluconate should be 50 mg/mL, and calcium chloride should be diluted to 20 mg/mL Calcium should not be prepared or infused with fluids containing phosphate or bicarbonate given the risk of precipitation of insoluble salts The dose for IV bolus of calcium gluconate in the setting of cardiac disturbance is 50 to 100 mg/kg/dose infused over to minutes and for tetany is 100 to 200 mg/kg/dose infused over to 10 minutes Intravenous calcium should not be infused more rapidly given the risk for cardiac arrhythmia, bradycardia, and arrest Cardiac monitoring and serial monitoring of the serum calcium level should be performed Repeat boluses should be provided until the symptoms resolve, and then a slower infusion should be continued For patients with either chronic hypocalcemia or milder degrees of acute hypocalcemia without severe symptoms, oral calcium is preferred Numerous forms of oral calcium salts are available Calcium carbonate is readily available and well tolerated If either hypoparathyroidism or vitamin D deficiency is suspected, vitamin D replacement should be provided to optimize enteral absorption The overall management goal of chronic hypocalcemia is to achieve acceptable serum calcium while avoiding hypercalcemia and excessive hypercalciuria Hypercalcemia Hypercalcemia results when the influx of calcium into the extracellular space exceeds the rate of deposition into bone or renal capacity for excretion This most commonly results from accelerated bone resorption secondary to increased PTH activity, but may also occur due to excessive absorption from the gastrointestinal tract, or decreased renal excretion Excessive exposure to vitamin D will increase intestinal calcium and phosphate absorption and would be associated with a depressed PTH level In addition to exogenous sources of vitamin D, granulomatous disorders may be associated with increased 1,25-dihydroxyvitamin D activity and promote absorptive hypercalcemia Accelerated bone resorption would be anticipated in primary, secondary, and tertiary hyperparathyroidism Jansen syndrome, a genetic disorder of the PTH receptor, renders the receptor constitutively active Children with Jansen syndrome present with hypercalcemia, undetectable levels of PTH, and skeletal changes consistent with hyperparathyroidism Immobilization, particularly in rapidly growing adolescents, may result in significant bone resorption and hypercalcemia Malignancy is a rare cause of hypercalcemia in children Decreased renal excretion occurs in familial hypocalciuric hypercalcemia (FHH), an autosomal dominant disorder FHH is characterized by mild, asymptomatic hypercalcemia, increased tubular reabsorption of calcium, and inappropriately normal PTH Hypercalcemia may also be seen in patients with Williams syndrome, and several metabolic disorders including hypophosphatasia and Bartter syndrome Medications associated with hypercalcemia include thiazide diuretics and lithium The evaluation of hypercalcemia begins with a thorough assessment of symptoms, diet, medications, medical history, and family history Laboratory evaluation should include ionized calcium, electrolytes, phosphorus, magnesium, renal function, serum albumin, and acid–base assessment Review of previous laboratory studies, if available, should be performed Though results will not be available to the ED physicians, PTH level is critical to ultimately determine the underlying cause If the PTH is not elevated, vitamin D metabolites should be obtained Assessment of urine calcium excretion via random urine calcium to creatinine ratio may also be informative Calcium excretion is high in hyperparathyroidism but low in FHH and with thiazide therapy Clinical manifestations Hypercalcemia is associated with a number of signs and symptoms depending on the acuity and severity of the disorder Patients with mildly elevated calcium (less than 11.5 to 12 mg/dL) are often asymptomatic, especially if the elevation is chronic in onset Patients with moderate hypercalcemia (12 to 14 mg/dL) may experience anorexia, irritability, abdominal pain, constipation, and weakness An important renal manifestation of hypercalcemia is polyuria due to an inability to concentrate urine, an acquired form of nephrogenic diabetes insipidus Should polyuria be associated with gastrointestinal symptoms and decreased fluid intake, dehydration will ensue and aggravate the existing hypercalcemia by reducing renal excretion of calcium If hypercalcemia is severe, progressive weakness, confusion, seizures, and coma may develop Management When hypercalcemia is mild, no specific therapy is warranted and efforts should focus on identifying the underlying condition Chronic moderate hypercalcemia (12 to 14 mg/dL) may be well tolerated and not require immediate intervention, though thorough evaluation should be pursued If hypercalcemia is severe (greater than 14 mg/dL) or associated with clinically significant symptoms, prompt intervention is warranted Given the gastrointestinal and renal manifestations associated with hypercalcemia, patients may present with hypovolemia Initial efforts should focus on restoring adequate intravascular volume with isotonic IV fluids, which will increase GFR and increase renal excretion of calcium Agents that inhibit osteoclasts, such as calcitonin and bisphosphonates, may be used to treat hypercalcemia secondary to increased bone resorption Calcitonin has rapid onset of action but resistance develops rapidly; bisphosphonates such as pamidronate and zoledronic acid have delayed onset but long duration of action, so may be useful when combined with calcitonin Loop diuretics such as furosemide are no longer routinely recommended due to risk of hypovolemia and electrolyte imbalance, but may be used judiciously if necessary to prevent fluid overload in patients with renal failure or CHF If the patient is in renal failure or efforts with saline diuresis and first-line agents are not sufficient, renal replacement therapy (RRT) may be necessary Consultation with a pediatric nephrologist or endocrinologist is advised DISORDERS OF ACID–BASE HOMEOSTASIS Goals of Treatment Maintenance of normal acid–base balance involves expiration of carbon dioxide, metabolism of organic acids, and buffering and renal excretion of nonvolatile acids Severe uncompensated acid–base disorders are associated with a variety of cardiovascular, metabolic, neurologic, and respiratory consequences General goals include treatment of the underlying etiology and maintenance of normal pH in order to prevent potentially fatal sequelae CLINICAL PEARLS AND PITFALLS ... agents are not sufficient, renal replacement therapy (RRT) may be necessary Consultation with a pediatric nephrologist or endocrinologist is advised DISORDERS OF ACID–BASE HOMEOSTASIS Goals of