Effect of magnesium infusion on bleeding time in healthy male volunteers

The effect of magnesium sulfate on post off-pump coronary artery bypass grafting bleeding

BACKGROUND

Magnesium level alteration may cause coagulation abnormality resulting in bleeding complication after off-pump coronary artery bypass grafting. In this study, we investigated the effect of magnesium on the postoperative coagulation profile and bleeding in OPCAB patients.

METHODS

In a double blind clinical trial, six hundred patients were randomly allocated to two groups: group A (n=150) and group B (n=450). Group A received 50mg/kg of magnesium sulfate (MS) in 100ml 0.9% NaCl solution over 20min before the anesthesia induction. Group B or control group received only 100ml 0.9% NaCl solution at the same time points. OPCAB was performed with standard technique and device. Blood samples were collected 30min before and 6h after the surgery to analyze hemoglobin and blood coagulation tests. Postoperative exploration for bleeding, blood transfusion, and volume of transfusion was recorded. The two groups compared with t-test and χ(2) tests and p-valve <0.05 were considered as significant.

RESULTS

However, postoperative hemoglobin was statistically lower in group A compared with group B, but platelet, PT, and aPTT tests were not statistically different between two groups. The serum MS level, exploration for bleeding, volume of packed cell transfusion, and volume of postoperative bleeding were statistically different between group A vs group B.

CONCLUSION

Preoperative MS use may be associated with the postoperative platelet dysfunction and increased tendency to bleeding. This is an important risk factor for postoperative bleeding in the OPCAB in absence of CPB use.

Effect of magnesium sulphate on bleeding during lumbar discectomy

We assessed the effect of magnesium on the amount of bleeding, coagulation profiles and surgical conditions during lumbar discectomy under general anaesthesia. Forty patients, of ASA physical status 1-2 and aged 18-65 years, undergoing single-level microscopic lumbar discectomy, were randomly assigned to magnesium sulphate (50 mg.kg(-1) in 100 ml saline over 10 min followed by a continuous infusion of 20 mg.kg.h(-1) ) or saline. The mean (SD) estimated blood loss was 190 (95) and 362 (170) ml in the magnesium and saline groups, respectively (mean difference = 172 ml; 95% CI 84-260 ml). The median (IQR [range]) Fromme's scale score for surgical conditions for the magnesium and saline groups were 2 (2-3 [2-3]) and 3 (2-3 [3-4]), respectively (p < 0.05). The bleeding time, haemoglobin, platelet count, prothrombin time, international normalised ratio and fibrinogen levels were similar in the two groups. The activated partial thromboplastin time was prolonged in the magnesium group immediately postoperatively and at 6 h after surgery. After the bolus of magnesium, the heart rate was higher and the mean arterial pressure lower in the magnesium group. The use of magnesium sulphate during lumbar discectomy decreases blood loss, and provides better surgical conditions without marked haemodynamic effects.

Platelet count may predict abnormal bleeding time among pregnant women with hypertension and preeclampsia

BACKGROUND

Anesthesiologists often require laboratory data to estimate the bleeding risk among hypertensive pregnant women prior to administering regional anesthesia. Many rely on the bleeding time (BT) in making this determination. We examined whether the platelet count can adequately predict BT among a group of hypertensive parturients.

METHODS

This retrospective subgroup analysis, taken from a cohort of 2,051 hypertensive pregnant women, comprises 87 individuals who underwent both a BT and platelet count prior to delivery. We calculated the correlation between the platelet count and BT at three platelet cut-off points with respect to prolonged BT of eight minutes or more.

RESULTS

There was a significant negative correlation between platelet count at delivery and BT [r= -0.45, 95% confidence interval (CI) -0.26 to -0.60; P <0.0001]. All three platelet cut-off points had a sensitivity of less than 66% with negative predictive values below 75% for an abnormal BT. A platelet count > or =75 x 109/L [corrected] was specific for the presence of an abnormal BT (specificity 97.8%, 95% CI 91.7-100.0), with a positive predictive value of 95.5% (95% CI 83.1-100.0) and a positive likelihood ratio of 24 (95% CI 3.3-168).

CONCLUSIONS

In a group of hypertensive parturients, the platelet count appears to be very specific for predicting a prolonged BT The platelet count may aid the anesthesiologist in determining the risk of bleeding from regional anesthesia. Given the study's potential for bias future research is needed to validate these findings.