Effect of magnesium sulfate administration on cholinesterase enzyme activity in the sera of patients with severe preeclampsia: is there any lowering effect?

Serum cholinestrase activity was determined using a colorimetric method in 60 females. They were divided into 3 groups, each comprising 20 females. The first group included pregnant females at term with severe preeclampsia. The second group included healthy pregnant females at term. The third group included healthy nonpregnant females. Blood samples were collected from all patients on admission. In the preeclamptic group, second samples were drawn 24 hours after the start of magnesium sulfate therapy. The mean level of serum cholinestrase activities in nonpregnant, preeclamptic and healthy pregnant patients were 2837 +/- 753, 2218 +/- 752 and 1667 +/- 485 units/L respectively. Differences are statistically significant [P < 0.0001]. The enzyme was found to be significantly decreased after the magnesium sulfate administration [1843 +/- 631 units/L] [P < 0.0001]. Our data demonstrated that magnesium has a significant inhibiting effect on serum cholinestrase activity in preeclamptic patients. We conclude that the magnesium inhibiting effect of the already low level of serum cholinestrase activity is responsible for the prolonged duration of action of succinylcholine in preeclamptic patients treated with magnesium sulfate. We believe that both the obstetrician and the anesthesiologist should be aware, alert and cooperative in dealing with these critical cases

Therapeutic serum level of magnesium in patients with severe pre-eclampsia treated with magnesium sulfate

Serum levels of magnesium were determined in 20 healthy nonpregnant females, 20 healthy normotensive pregnant females at term and 20 pregnant females at term with severe preeclampsia. All the preeclamptic patients received a low dosage intramuscular regimen of magnesium sulfate [MgSO[4]] and the serum levels of magnesium were determined again after 24 hours. There was no difference in the baseline values of serum magnesium inthe 3 studied groups. A 6 g loading dose of MgSO[4][3 g I.V. and 3 g I.M.] followed by 3 g/4 hr. I.M. caused maternal serum magnesium concentrations to rise by about 50% from the baseline value of 1.8 mEq/L [2.2 mg/dl] to 2.7 mEq/L [3.3 mg/dl] [P < 0.0001]. Oxytocin used to augment or induce labor in 7 preeclamptic patients had no effect on the serum level of magnesium. The efficiency of our regimen in preventing seizures in cases of severe preeclampsia suggests that the therapeutic level of serum mangesium required to prevent convulsions in preeclampsia may not be as high as previously defined by other investigators. The possibility that a higher dose of MgSO[4], to achieve a higher therapeutic serum level of magnesium, is needed to treat and prevent further seizures in eclampsia is present. Thus, MgSO[4] regimen should be different in the two conditions of similar etiology but with variable severity