Fluctuations in serum magnesium levels during total intravenous anaesthesia with propofol.

Forty patients who underwent eye surgery under total intravenous anaesthesia with propofol where investigated in order to determine the fluctuations of serum magnesium levels during anaesthesia. Six blood samples were taken before anaesthesia, after induction, 1 hour later, 2 hours later, after recovery, and 24 hours after surgery. In the same time intervals, systolic and diastolic blood pressure, heart rate and temperature were recorded. The results showed a statistically significant decrease in serum magnesium levels during anaesthesia. No correlations between this decrease and the fluctuations of blood pressure, heart rate or temperature were found. These results indicate that there is a shift of magnesium into the tissue stores due to the state of anaesthesia, possibly by a direct effect of the anaesthetic agents on the cell membrane itself. Further investigation is needed with other techniques and agents employed in general anaesthesia.

Prophylactic effects of intravenous magnesium on hypertensive emergencies after cataract surgery. A new contribution to the pharmacological use of magnesium in anaesthesiology.

The pharmacological effects of magnesium sulphate heptahydrate (MgSO4.7H2O) on hypertensive patients during the perioperative period were used, to control critical rises of blood pressure. This double-blind study included 40 hypertensive elderly patients, who underwent eye surgery under local anaesthesia; they were divided into two groups (A and B) of 20 patients each. An intravenous dose of 4g MgSO4.7H2O was given to group. A, while group B, which was used as a control group, was given to a placebo. All patients were premedicated with 10 mg oral diazepam 1.5 h before the operation. Systolic and diastolic blood pressure, heart rate and ECG were monitored for 1 h. None of the patients who received MgSO4.7H2O showed any ECG disturbances. Systolic and diastolic blood pressure, as well as heart rate, fluctuated outside the critical range, whereas in the control group an increase of blood pressure was noted which was treated with other anti hypertensive drugs. The results indicated that parenteral administration of MgSO4.7H2O in hypertensive patients before surgery stabilized blood pressure fluctuations outside the critical range, without causing the pressure to fall to a level that might risk undesirable side effects during eye surgery under local anaesthesia.