Risk factors for failed conversion of labor epidural analgesia to cesarean delivery anesthesia: a systematic review and meta-analysis of observational trials.

BACKGROUND: This systematic review and meta-analysis evaluates evidence for seven risk factors associated with failed conversion of labor epidural analgesia to cesarean delivery anesthesia. METHODS: Online scientific literature databases were searched using a strategy which identified observational trials, published between January 1979 and May 2011, which evaluated risk factors for failed conversion of epidural analgesia to anesthesia or documented a failure rate resulting in general anesthesia. RESULTS: 1450 trials were screened, and 13 trials were included for review (n=8628). Three factors increase the risk for failed conversion: an increasing number of clinician-administered boluses during labor (OR=3.2, 95% CI 1.8-5.5), greater urgency for cesarean delivery (OR=40.4, 95% CI 8.8-186), and a non-obstetric anesthesiologist providing care (OR=4.6, 95% CI 1.8-11.5). Insufficient evidence is available to support combined spinal-epidural versus standard epidural techniques, duration of epidural analgesia, cervical dilation at the time of epidural placement, and body mass index or weight as risk factors for failed epidural conversion. CONCLUSION: The risk of failed conversion of labor epidural analgesia to anesthesia is increased with an increasing number of boluses administered during labor, an enhanced urgency for cesarean delivery, and care being provided by a non-obstetric anesthesiologist. Further high-quality studies are needed to evaluate the many potential risk factors associated with failed conversion of labor epidural analgesia to anesthesia for cesarean delivery.

What's new in obstetric anesthesia?

The current article covers some of the major themes that emerged in 2009 in the fields of obstetric anesthesiology, obstetrics, and perinatology, with a special emphasis on the implications for the obstetric anesthesiologist.

An observational cohort study of the meniscus test to detect intravascular epidural catheters in pregnant women.

BACKGROUND: The meniscus test is a rapid non-pharmacologic method of confirming epidural catheter placement by observing a normal saline meniscus while physically manipulating the catheter. The aim of this study was to assess whether the meniscus test improves diagnostic accuracy of aspiration to detect intravascular or intrathecal placement of epidural catheters in pregnant women. METHODS: In this prospective observational study, parturients at >or= 36 weeks of gestation were recruited. In the sitting position, participants received a multiorifice epidural catheter for elective cesarean delivery or labor analgesia. After aspiration was confirmed to be negative for blood and cerebrospinal fluid, the meniscus test was performed. Subsequently, a pharmacologic test dose was given with 1.5% lidocaine 3 mL and epinephrine 15 microg. Intravascular placement was diagnosed if the patient experienced an increase in heart rate >or= 20 beats/min within 2 min with or without tinnitus, metallic taste, dizziness, palpitations, headache, or anxiety. RESULTS: The overall intravascular catheter rate was 5.7% (24/419). The rate of intravascular catheter location not detected by aspiration was 0.95% (4/419). Given negative catheter aspiration, the meniscus test demonstrated 25% sensitivity, 87.5% specificity, and 1.9% positive predictive value for intravascular catheter insertion. No intrathecal catheters were observed. CONCLUSIONS: For obstetric patients in the sitting position, the meniscus test does not improve diagnostic accuracy of aspiration for detecting intravascular multiorifice epidural catheter placement.

Internal carotid artery dissection: an unusual cause of postpartum headache.

We report a case of postpartum headache caused by internal carotid artery dissection in a 36-year-old woman following uneventful epidural analgesia for spontaneous labor and vaginal delivery. Cervicocerebral arterial dissection requires rapid diagnosis and anticoagulation to prevent thrombus formation and to avoid secondary cerebral thromboembolism. Fortunately, our patient suffered ischemic symptoms, but no permanent neurologic deficit. Anesthesiologists should consider carotid artery dissection in the differential diagnosis of postpartum headache.

Survey of obstetric providers' views on the anesthetic risks of maternal obesity.

BACKGROUND: Maternal obesity is increasing in prevalence and associated with numerous complications. Surveys document that obstetricians recognize the obstetric and perinatal health risks of maternal obesity. To determine if they recognize the anesthetic risks and discuss them antenatally with obese patients, we surveyed all obstetric providers at a university-affiliated obstetric unit. METHODS: The survey listed complications of obesity and pregnancy sampled from the literature, including eight anesthetic complications, ten prenatal obstetric complications, ten intrapartum or postpartum obstetric complications, five medical complications and five neonatal complications. Respondents reported if and when they routinely discuss each. Reported routine discussion rates were averaged across respondents and complication categories. We postulated that anesthetic aspects would be discussed less frequently than others. RESULTS: Thirty-six of the 55 obstetric providers responded (65.5%). On average, anesthetic complications were discussed during prenatal care 13.5% of the time, less often than prenatal obstetric complications (48.5%, Wilcoxon signed rank test, P<0.0001), intrapartum or postpartum obstetric complications (40.0%, Wilcoxon signed rank test, P<0.0001) and medical complications (35.0%, Wilcoxon signed rank test, P=0.0001). The survey failed to demonstrate a statistically significant difference in the rate of discussion between anesthetic and neonatal complications (13.5% vs. 22.2%, Wilcoxon signed rank test, P=0.05). Twenty-four respondents reported that they did not routinely discuss any of the listed anesthetic complications with their obese patients in the prenatal period. CONCLUSIONS: This preliminary study suggests that antenatal education about the anesthetic implications of obesity may not be part of routine prenatal care for obese pregnant women.