Acute Severe Muscle Cramps or Tetany
Severe muscle cramps with tetany require immediate assessment for life-threatening electrolyte derangements and urgent treatment while diagnostic testing is pending. Acute symptomatic hypocalcaemia is treated as a medical emergency with intravenous calcium gluconate. [1]
Initial Stabilization and Monitoring
- Airway, breathing, and circulation should be assessed. [1]
- Electrocardiographic monitoring should be performed during intravenous calcium replacement. [1]
- Venous access should be obtained for rapid intravenous therapy when tetany is symptomatic. [1]
Diagnostic Evaluation for Reversible Causes
- Serum calcium should be checked using albumin-adjusted calcium for initial decision-making. [1]
- Serum phosphate, magnesium, and electrolytes should be checked. [1]
- Parathyroid hormone should be obtained to support identification of hypoparathyroidism as an etiology. [1]
- Urea and electrolytes should be measured to assess renal function and contributors to electrolyte abnormalities. [1]
Medication Selection Algorithm
The acute neurologic phenotype of tetany should trigger empiric correction of the most common dangerous causes:
- Hypocalcaemia should be treated with intravenous calcium gluconate. [1]
- Hypomagnesaemia should be treated with intravenous magnesium sulfate when symptomatic. [2]
Hypocalcaemia Treatment (Symptomatic Tetany)
- Severe hypocalcaemia should be treated with intravenous calcium gluconate. [1]
- The initial dose should be 10–20 mL of 10% calcium gluconate diluted in 50–100 mL of 5% dextrose, administered intravenously over 10 minutes with ECG monitoring. [1]
- The bolus should be repeated until the patient is asymptomatic. [1]
- After the bolus, calcium gluconate infusion should be used by diluting 100 mL of 10% calcium gluconate (10 vials) in 1 L of normal saline or 5% dextrose and infusing at 50–100 mL/h. [1]
- The infusion rate should be titrated to achieve normocalcaemia and continued until treatment of the underlying cause takes effect. [1]
- Calcium chloride should be reserved as an alternative because it is more irritant to veins and should only be administered via a central line with cardiac monitoring. [1]
Hypomagnesaemia Treatment (Symptomatic Tetany)
- Symptomatic hypomagnesaemia with severe features (including tetany) should be treated with intravenous magnesium. [2]
- Intravenous magnesium should be administered at 0.1–0.2 mmol/kg, up to 0.4 mmol/kg (maximum 8 mmol), with specialist advice and with administration planning based on severity. [2]
- Intravenous magnesium replacement in children should be administered over 2–4 hours to reduce adverse effects and improve cellular uptake, with shorter administration periods possible for severe symptoms. [2]
- The underlying cause should be identified and corrected when possible. [2]
Treatment Initiation Thresholds
- Hypocalcaemia should be treated as severe emergency physiology when serum calcium is <1.9 mmol/L and/or when tetany is symptomatic at any level below the reference range. [1]
- Hypomagnesaemia should be treated with intravenous replacement when symptoms are severe and include tetany. [2]
Common Pitfalls to Avoid
- Large-volume calcium infusions should not be used in patients with end-stage renal failure or patients on dialysis. [1]
- Calcium replacement should not be treated as the only intervention because underlying etiologies (including hypoparathyroidism and magnesium deficiency) should be addressed. [1]
- Calcium infusion should be accompanied by ECG monitoring because hazards include cardiotoxicity. [1]
Targets of Therapy
- Calcium gluconate infusion should be titrated to achieve normocalcaemia. [1]
- Magnesium replacement should aim to achieve normal serum magnesium level. [2]