The lack of effect of routine magnesium administration on respiratory function in mechanically ventilated patients.
OBJECTIVE
We wished to determine if magnesium infusion would improve respiratory muscle function in long-term ventilated patients even in the absence of hypomagnesemia.


METHODS
Prospective study of mechanically ventilated patients using a double-blind crossover design.


METHODS
A combined medical-surgical ICU of a university teaching hospital.


METHODS
Twenty-one separate admissions to the ICU in 20 patients were studied. Patients who were selected had been intubated and mechanically ventilated for at least 6 days with the admitting diagnosis of respiratory failure.


METHODS
Twelve patients received 6 g MgSO4 intravenous (i.v.) infusion over 16 h on day 1 followed by placebo infusion on day 2. Nine patients received placebo on day 1 followed by MgSO4 (6 g i.v.) on day 2.


RESULTS
We measured vital capacity (VC), maximal inspiratory pressure (Pmax) and maximal expiratory pressure (Pemax) in all patients. There were no significant differences in Pimax (37 +/- 14 vs 42 +/- 20 cm H2O), Pemax (59 +/- 32 vs 61 +/- 38 cm H2O), and VC (850 +/- 460 vs 960 +/- 490 ml) comparing values before and after magnesium infusion. We could not find a subgroup of patients with a marked improvement in Pimax or Pemax.


CONCLUSIONS
In patients requiring mechanical ventilation for respiratory failure, magnesium infusion is not associated with increased respiratory muscle strength. Although a trial of MgSO4 administration may be considered for patients with difficulty weaning from mechanical ventilation, it is unlikely to result in clinical improvement.
Johnson
D
D
Department of Anesthesia, Royal University Hospital, Saskatoon, Saskatchewan, Canada.
Gallagher
C
C
Cavanaugh
M
M
Yip
R
R
Mayers
I
I
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007362:Intensive Care Units; D008274:Magnesium / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy; D015656:Respiratory Mechanics / Q000187:drug effects*
D008274:Magnesium