Central nerve block and coagulation: a survey of obstetric anaesthetists

Diagnosis, evaluation, and management of the hypertensive disorders of pregnancy

OBJECTIVE

This guideline summarizes the quality of the evidence to date and provides a reasonable approach to the diagnosis, evaluation and treatment of the hypertensive disorders of pregnancy (HDP).

EVIDENCE

The literature reviewed included the previous Society of Obstetricians and Gynaecologists of Canada (SOGC) HDP guidelines from 2008 and their reference lists, and an update from 2006. Medline, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Registry of Controlled Trials (CCRCT) and Database of Abstracts and Reviews of Effects (DARE) were searched for literature published between January 2006 and March 2012. Articles were restricted to those published in French or English. Recommendations were evaluated using the criteria of the Canadian Task Force on Preventive Health Care and GRADE.

Platelet Counts and Coagulation Tests Prior to Neuraxial Anesthesia in Patients With Preeclampsia

This retrospective, descriptive study aimed to assess hematologic testing practices in 100 patients with preeclampsia undergoing neuraxial blockade (NB). Prior to NB, platelet (PLT) count was performed in 61 (98%) of 62 women in labor and in 37 (97%) of 38 women undergoing cesarean delivery (CD). No patients had a pre-NB PLT count <70 × 109/L. Pre-NB tests for prothrombin time (PT) and activated partial thromboplastin time (APTT) were less common and varied among laboring patients (15 [24%] of 62) and patients prior to CD (18 [47%] of 38). Prior to NB, PT and APTT values were within normal limits in all patients. The time intervals between laboratory testing and NB ranged from <2 to >12 hours. The lack of consistency in pre-NB coagulation testing and the variable time intervals between laboratory tests and NB may be due to a lack of consensus among anesthesiologists for determining “safe” hemostatic conditions for NB placement in patients with preeclampsia.

Complications of regional and general anaesthesia in obstetric practice

Any anaesthetic technique, either regional or general, has potential for complications. Moreover, it has been seen that in obstetric patients, the complications are potentiated due to pregnancy-related changes in physiology and due to various other factors. Increasing trend of caesarean section in the setting of increasing maternal age, obesity and other concomitant diseases will continue to challenge the obstetric anaesthetist in his/her task of providing safe regional and general anaesthesia. This review has highlighted the possible complications of regional and general anaesthesia encountered during the obstetric anaesthesia practice.

Pharmacotherapeutic options for the treatment of preeclampsia

PURPOSE

Pharmacotherapeutic options for the treatment of preeclampsia are reviewed.

SUMMARY

Risk factors for the development of preeclampsia include microvascular diseases, such as diabetes mellitus; vascular and connective tissue disorders; hypertension; antiphospholipid antibody syndrome; and nephropathy. Several pathophysiological factors contribute to the development of the preeclamptic state, including vasospasm onset, coagulation system activation, increased inflammatory response, and ischemia. The specific agents used for the treatment of preeclampsia are dependent on a number of factors including symptom severity, maternal or fetal compromise, the progression to eclampsia, gestational period, and cervical status. The diagnosis of preeclampsia beyond the gestation period of 38 weeks requires delivery. The presence of maternal compromise or eclampsia at gestation greater than 20 weeks also necessitates delivery. In cases of chronic or mild hypertension, oral methyldopa may be administered on an outpatient basis. Intravenous hydralazine is a commonly administered arteriolar vasodilator that is effective for hypertensive emergencies associated with pregnancies. The most common adverse effect of hydralazine administration is unpredictable hypotension. Labetalol decreases heart rate and may be preferred because of a lack of reflex tachycardia, hypotension, or increased intracranial pressure. However, the drug of choice for the prevention and control of maternal seizures in patients with severe preeclampsia or eclampsia during the peripartum period is i.v. magnesium sulfate. Therapeutic serum magnesium levels cause cerebral vasodilation, thereby reversing the ischemia produced by cerebral vasospasm during an eclamptic episode. The results of one study indicated that women receiving magnesium sulfate therapy had a 58% lower risk of eclampsia than placebo.

CONCLUSION

Magnesium sulfate remains the drug of choice for the prevention and treatment of preeclampsia. Alternative antihypertensive agents may provide additional benefit in the management of hypertension for preeclamptic patients.

Hemostatic Function in Healthy Pregnant and Preeclamptic Women: An Assessment Using the Platelet Function Analyzer (PFA-100??) and Thromboelastograph??

BACKGROUND

The PFA-100 is a point-of-care platelet function analyzer which measures the speed of formation of a platelet plug in vitro, expressed as closure time (CT) in seconds. This device could potentially be used to assess primary hemostasis prior to regional anesthesia. In this prospective, observational study we sought to establish 95% reference intervals for PFA-100 and Thromboelastograph (TEG) values for our normal pregnant population, before comparing the PFA and TEG in measuring platelet function in preeclamptic and healthy pregnant women at term, using confidence interval analysis and analysis of variance.

METHODS

Routine hematologic and coagulation tests were performed along with von Willebrand Factor, CT, and TEG measurements. Results are expressed as mean (sd).

RESULTS

Increased severity of preeclampsia was associated with increasing prolongation of CT, even in the presence of normal platelet counts. In severe preeclampsia, the PFA-100 CT (mean (sd): 155 (65) s) exceeded the 95% reference interval of the control group (70-139 s). In contrast, TEG maximum amplitude (MA) in severe preeclampsia (mean (sd): 71 (8) mm) remained within the 95% reference interval for MA in normal pregnancy (64-82 mm).

CONCLUSION

We conclude that impairment of primary hemostatic function with increasing severity of preeclampsia was recorded by the PFA-100 but not the TEG.

Evaluation of the platelet function analyzer (PFA-100®) vs. the thromboelastogram (TEG) in the parturient

BACKGROUND

The platelet function analyzer (PFA-100) is a bedside test of coagulation designed to evaluate platelet function. It measures the time required for whole blood to occlude a membrane impregnated with either epinephrine (EPI) or adenosine 5'diphosphate (ADP). The results are reported as closure time (CT-EPI or CT-ADP) in seconds. The thromboelastogram (TEG) measures whole blood clotting and the maximum amplitude (MA) correlates with platelet count and function. We wished to establish whether there is a correlation between the CT and platelet count, between the CT and MA, and between the MA and platelet count.

METHODS

Platelet count, CT, and MA were measured in blood drawn from 172 healthy term parturients using the PFA-100.

RESULTS

We were unable to detect a significant correlation between the CT-EPI and platelet count (r=-0.1, P=0.21), or the CT-ADP and platelet count (r=-0.02, P=0.83). We also did not find a correlation between the CT-EPI and MA (r=-0.13, P=0.12) or between the CT-ADP and MA (r=-0.11, P=0.19). However, we found a significant correlation between platelet count and MA (r=0.33, P<0.001).

CONCLUSIONS

We conclude that the CT does not correlate with the platelet count or MA in the parturient, but the TEG does. Therefore the TEG may be a better tool to evaluate coagulation in the parturient with thrombocytopenia.