Table 7.

Clinical manifestations of hypermagnaesemia^a

Serum Mg (mmol/L)	Symptoms
	Neurological	Circulatory–respiratory–gastrointestinal	ECG	Comments
2.1–2.4		Paralytic ileus [110]	Bradycardia [111]	Both single case reports, one Patient suffering from chronic renal insufficiency (creatinine clearance 13 ml/min) [111], iatrogenic [111]
2.5–4.0	Deep tendon reflexes depressed [107, 108, 109], muscle weakness, slurred speech, lethargy [91]	Hypotension, nausea, flushing, decreased uterine tone upon magnesium infusion [109]; gastrointestinal paralysis [110]	Tachycardia, T-wave abnormalities; prolonged QT-time [91]	Target level for treatment of eclampsia is 2.5-4.0 mmol/L. [22, 108, 109, 112, 113]. However, serum Mg values are measured infrequently. Even in patients treated with MgSO4, decisions are based on clinical signs such as depressed deep-tendon reflexes [27]. Case reports [91, 110], renal insufficiency [110]
3.7–4.9	Confusion [114], loss of deep tendon reflexes [109], neuromuscular blockade, quadriparesis [115]	Hypotension [114]		Single case reports [114, 115], renal failure, PD treatment [115], review [109]
5.0–6.95	Lethargy [94, 116], slurred speech, profound muscle weakness [90]	Hypotension [94, 116], increased respiratory rateb [94, 109]; respiratory arrest [95]	Atrial fibrillation [94]; QT prolongation [92, 116] sinus tachycardia, 1st degree AV-block, bradycardia [92]	Single case reports [92, 95, 116], case reports and reviews [90, 94], review [109]
Up to ≤7.65 and 7.3	Paralysis of the limbs [117]	No respiratory arrest, slight decrease of blood pressure [117]	Sinus arrhythmia, slight alterations in ventricular action (T-wave, ST, R abnormalities, prolonged PR interval) [117]	Clinical investigation in two individuals in an experimental setting during magnesium sulphate infusion [117]
>8.9–10.65	‘Coma’ [118, 119], pseudocomatose state, central brain-stem herniation syndrome, non-fatal neuromuscular blockade	Profound hypotension, cardiopulmonary non-fatal arrest [118, 120], cardiovascular collapse at 25 mg/dL (10.3 mmol) [109]	Prolonged QT interval, bradycardia [120]	Case reports [118–121], review [109]
Up to 13. 5 [102]; 16.9 [122]; 17.8 [100]; 21.5 and 22.5 [97]		Respiratory depression, apnoea [97, 100], cardiopulmonary arrest [122]	Non-fatal refractory bradycardia [97]	Case reports, newborns [97, 100], case report, child [122], description of Dead Sea poisoning in 48 patients with different degrees of intoxication, the most dangerous combination occurred when serum calcium concentration was also high [102]

^aThe table demonstrates a certain difficulty to link clinically distinct symptoms to specific serum magnesium levels. However, neurological symptoms, such as depression/loss of deep tendon reflexes, unequivocally occur at serum levels greater than 3.7 to 4.0 mmol/L.

^bSymptom also used for monitoring purposes in eclampsia [109]

AV, atrio-ventricular; Mg, magnesium; MgSO₄, magnesium sulphate; PD, peritoneal dialysis.