The median local analgesic dose of intrathecal bupivacaine with hydromorphone for labour: a double-blind randomized controlled trial.

PURPOSE: Neuraxial hydromorphone has been reported to provide rapid onset of labour analgesia, effective segmental pain relief, and a longer duration of action than commonly used lipophilic opioids. This study was conducted to test the hypothesis that intrathecal hydromorphone reduces the dose requirement for intrathecal bupivacaine to induce rapid analgesia for women in the first stage of labour. METHODS: In this double-blind randomized controlled sequential allocation trial, 88 labouring parturients received combined spinal-epidural analgesia at 2-6 cm cervical dilation. Participants received intrathecal bupivacaine alone or bupivacaine plus hydromorphone 100 µg with the bupivacaine dose determined using up-down sequential allocation. An effective dose was defined as a visual analogue pain score of ≤10 mm (on a 100-mm pain scale) reported within 20 min of injection. The median effective doses were calculated using the formula of Dixon and Massey and verified using isotonic regression. RESULTS: A decrease was observed in the median local analgesic doses (effective dose [ED50]) estimated according to the formulas of Dixon and Massey, with a between-group difference of -0.45 mg. The precision of the estimate was wide-ranging (95% confidence interval -1.23 to 0.33), so no definitive conclusion can be drawn. CONCLUSION: Further research is needed to determine whether or not intrathecal hydromorphone 100 µg changes the dose of intrathecal bupivacaine required to induce labour analgesia within 20 min. TRIAL REGISTRATION: The trial was conducted in 2007 prior to widespread acceptance of the standard for clinical trial registration.

A survey of obstetric perianesthesia care unit standards.

BACKGROUND: Although obstetric patients are generally healthy, population risk is increasing because of increases in maternal age, obesity, and rates of multifetal pregnancies, and complications may occur in the immediate postoperative period. In this study, we sought to identify the current level of recovery care for obstetric patients in North American academic institutions after either general or major neuraxial anesthesia for cesarean delivery. METHODS: A survey of obstetric anesthesia recovery practices was delivered electronically to 135 obstetric anesthesiology directors of North American academic institutions from June to October, 2007. Surveys were completed electronically and anonymously. RESULTS: The response rate was 54.8% (74 of 135). Respondents reported a median of 2550 deliveries per year (interquartile range [IQR] 2000, 4000), with 30% delivered by cesarean delivery (IQR 25.5%, 32.5%) and 5% of cesarean deliveries performed under general anesthesia (IQR 4%, 8%). Most institutions recovered postcesarean patients in either an obstetric perianesthesia care unit or a labor, delivery, and recovery room. Recovery care was staffed solely by perinatal nurses, rather than dedicated perianesthesia care unit nurses in most institutions. Forty-five percent (28 of 62) of institutions had no specific postanesthesia recovery training for nursing staff providing postcesarean care for patients recovering from neuraxial or general anesthesia. Forty-three percent (29 of 67) of respondents rated the recovery care provided to cesarean delivery patients as lower quality than care given to general surgical patients. Respondents who relied solely on perinatal nurses to provide postanesthesia care were most likely to perceive that postanesthetic care for cesarean delivery was of lower quality than that given to general surgery patients (P = 0.008). CONCLUSIONS: Guidelines put forth by the American Society of Anesthesiologists Task Force on Postanesthetic Care and the American Society of PeriAnesthesia Nurses apply to all postoperative patients regardless of their recovery locations. Results from this survey suggest that the level of care provided for postanesthesia recovery from cesarean delivery in North American academic institutions may not meet these guidelines.

A systematic review of randomized controlled trials that evaluate strategies to avoid epidural vein cannulation during obstetric epidural catheter placement.

BACKGROUND: In this systematic review, we evaluated the evidence for seven strategies which have been proposed to minimize the incidence of epidural vein cannulation during lumbar epidural catheter placement in pregnant women. METHODS: Multiple databases were searched to identify prospective, randomized, controlled trials between December 1966 and October 2007 that evaluated methods to avoid epidural vein cannulation after lumbar epidural catheter placement in pregnant women. Published trials were evaluated using a quality assessment tool, and results were combined to evaluate efficacy to prevent epidural vein cannulation. RESULTS: Of 90 trials screened, 30 trials were included (n = 12,738 subjects). Five strategies reduce the risk of epidural vein cannulation: the lateral as opposed to sitting position (six trials, mean (sd) quality score = 35% [11%], odds ratio (OR) 0.53 [95% confidence interval (CI) 0.32-0.86]), fluid administered through the epidural needle before catheter insertion (8 trials, quality score 48% [18%], OR 0.49 [95% CI 0.25-0.97]), single rather than multiorifice catheter (5 trials, quality score 30% [6%], OR 0.64 [95% CI 0.45-0.91]), a wire-embedded polyurethane compared with polyamide epidural catheter (1 trial, 31%, plus 4 unscored abstracts, OR 0.14 [95% CI 0.06-0.30]) and catheter insertion depth < or =6 cm (2 trials, 47% [11%], OR 0.27 [95% CI 0.10-0.74]). The paramedian as opposed to midline needle approach and smaller epidural needle or catheter gauges do not reduce the risk of epidural vein cannulation. CONCLUSION: The risk of intravascular placement of a lumbar epidural catheter in pregnancy may be reduced with the lateral patient position, fluid predistension, a single orifice catheter, a wire-embedded polyurethane epidural catheter and limiting the depth of catheter insertion to 6 cm or less. In general, low manuscript quality weakens the strength of these conclusions.

Maternal physiologic parameters in relationship to systemic inflammatory response syndrome criteria: a systematic review and meta-analysis.

OBJECTIVE: To establish the normal maternal range in healthy pregnant women for each component of the systemic inflammatory response syndrome (SIRS) criteria and compare these ranges with existing SIRS criteria. DATA SOURCES: PubMed, Embase, and ClinicalTrials.gov databases were searched to identify studies of healthy parturients from the first trimester through 12 weeks postpartum that reported maternal temperature, respiratory rate, PaCO2, heart rate, white blood cell count data, or a combination of these. METHODS OF STUDY SELECTION: Data were extracted from studies providing maternal values for components of SIRS criteria. The mean, standard deviation, and two standard deviations from the mean for all criteria parameters published in the literature were reported. TABULATION, INTEGRATION, AND RESULTS: Eighty-seven studies met inclusion criteria and included 8,834 patients and 15,237 data points: temperature (10 studies and 2,367 patients), respiratory rate (nine studies and 312 patients), PaCO2 (12 studies and 441 patients), heart rate (39 studies and 1,374 patients), and white blood cell count (23 studies and 4,553 patients). Overlap with SIRS criteria occurred in healthy pregnant women during the second trimester, third trimester, and labor for each of the SIRS criteria except temperature. Every mean value for PaCO2 during pregnancy (and up to 48 hours postpartum) was below 32 mm Hg. Two standard deviations above the mean for temperature, respiratory rate, and heart rate were 38.1°C, 25 breaths per minute, and 107 beats per minute, respectively. CONCLUSION: Current SIRS criteria often overlap with normal physiologic parameters during pregnancy and the immediate postpartum period; thus, alternative criteria must be developed to diagnose maternal sepsis.

A series of anesthesia-related maternal deaths in Michigan, 1985-2003.

BACKGROUND: Maternal Mortality Surveillance has been conducted by the State of Michigan since 1950, and anesthesia-related maternal deaths were most recently reviewed for the years 1972-1984. METHODS: Records for pregnancy-associated deaths between 1985 and 2003 were reviewed to identify 25 cases associated with a perioperative arrest or major anesthetic complication. Four obstetric anesthesiologists independently classified these cases, and disagreements were resolved by discussion. Precise definitions of anesthesia-related and anesthesia-contributing maternal death were constructed. Anesthesia-related deaths were reviewed to identify the chain of medical errors or care management problems that contributed to each patient death. RESULTS: Of 855 pregnancy-associated deaths, 8 were anesthesia-related and 7 were anesthesia-contributing. There were no deaths during induction of general anesthesia. Five resulted from hypoventilation or airway obstruction during emergence, extubation, or recovery. Lapses in either postoperative monitoring or anesthesiology supervision seemed to contribute to 5 of the 8 anesthesia-related deaths. Other characteristics common to these cases included obesity (n=6) and African-American race (n=6). CONCLUSIONS: The 8 anesthesia-related and seven anesthesia-contributing maternal deaths in Michigan between 1985 and 2003 illustrate three key points. First, all anesthesia-related deaths from airway obstruction or hypoventilation took place during emergence and recovery, not during the induction of general anesthesia. Second, system errors played a role in the majority of cases. Of concern, lapses in postoperative monitoring and inadequate supervision by an anesthesiologist seemed to contribute to more than half of the deaths. Finally, this report confirms previous work that obesity and African-American race are important risk factors for anesthesia-related maternal mortality.

Effect of epidural epinephrine on the minimum local analgesic concentration of epidural bupivacaine in labor.

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the local anesthetic-sparing efficacy of epidural epinephrine by its effect on the MLAC of bupivacaine. METHODS: In this double-blind, randomized, prospective study, 70 parturients who were at 7 cm or less cervical dilation and who requested epidural analgesia were allocated to one of two groups. After lumbar epidural catheter placement, 20 ml bupivacaine (n = 35) or bupivacaine with epinephrine 1:300,000 (n = 35) was administered. The concentration of bupivacaine was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores, with 10 mm or less within 30 min defined as effective. RESULTS: The MLAC of bupivacaine alone was 0.091% wt/vol (95% confidence interval, 0.081-0.102). The addition of epinephrine 1:300,000 (66.7 microg) resulted in a significant reduction (P < 0.01) in the MLAC of bupivacaine to 0.065% wt/vol (95% confidence interval, 0.047-0.083). The lowest maternal blood pressure was significantly lower in the bupivacaine-epinephrine group (P = 0.03). There were statistically significant reductions in fetal heart rate (P = 0.011) in the bupivacaine-epinephrine group that were not clinically significant. CONCLUSIONS: The addition of epidural epinephrine 1:300,000 (66 microg) resulted in a significant 29% reduction in the MLAC of bupivacaine. Coincident reductions in fetal heart rate and maternal blood pressure were also observed that were not clinically significant.

Relative analgesic potencies of levobupivacaine and ropivacaine for epidural analgesia in labor.

BACKGROUND: The minimum local analgesic concentration has been defined as the median effective local analgesic concentration (EC50) in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to assess the relative analgesic potencies of epidural levobupivacaine and ropivacaine by determination of their respective minimum local analgesic concentrations. METHODS: Parturients at 7 cm of cervical dilation or less who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After lumbar epidural catheter placement, 20 ml of the test solution was given: levobupivacaine (n = 35) or ropivacaine (n = 35). The concentration of local anesthetic was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scale scores, with 10 mm or less within 30 min defined as effective. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. RESULTS: Of 105 women enrolled, 35 were excluded, leaving 70 for analysis. The minimum local analgesic concentration of levobupivacaine was 0.087% wt/vol (95% CI, 0.081-0.094%), and the minimum local analgesic concentration of ropivacaine was 0.089% wt/vol (95% CI, 0.075-0.103%). Levobupivacaine and ropivacaine were of similar potency with a ropivacaine:levobupivacaine potency ratio of 0.98 (95% CI, 0.80-1.20). No difference in motor effects was observed. CONCLUSIONS: This study demonstrated that levobupivacaine and ropivacaine are of similar potency for epidural analgesia in the first stage of labor.