Linda S. Polley

Practice guidelines for obstetric anesthesia: An updated report by the American Society of Anesthesiologists Task Force on obstetric anesthesia

PRACTICE guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints and are not intended to replace local institutional policies. In addition, practice guidelines are not intended as standards or absolute requirements, and their use cannot guarantee any specific outcome. Practice guidelines are subject to revision as warranted by the evolution of medical knowledge, technology, and practice. They provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert opinion, open forum commentary, and clinical feasibility data. This update includes data published since the “Practice Guidelines for Obstetrical Anesthesia” were adopted by the American Society of Anesthesiologists in 1998; it also includes data and recommendations for a wider range of techniques than was previously addressed.

Relative Analgesic Potencies of Ropivacaine and Bupivacaine for Epidural Analgesia in Labor Implications for Therapeutic Indexes

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 assess the relative analgesic potencies of epidural bupivacaine and ropivacaine by determining their respective minimum local analgesic concentrations. Methods Seventy-three parturients at Results The minimum local analgesic concentration of ropivacaine was 0.111% wt/vol (95% confidence interval, 0.100-0.122), and the minimum local analgesic concentration of bupivacaine was 0.067% wt/vol (95% confidence interval, 0.052-0.082). Ropivacaine was significantly less potent than bupivacaine, with a potency ratio of 0.6 (95% confidence interval, 0.49-0.74). No difference in motor effects was observed. Conclusion Ropivacaine was significantly less potent than bupivacaine for epidural analgesia in the first stage of labor.

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.

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.

Dose-dependent reduction of the minimum local analgesic concentration of bupivacaine by sufentanil for epidural analgesia 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 sufentanil by its effect on the MLAC of bupivacaine. Methods In this double-blind, randomized, prospective study, 147 parturients at <or= to 7 cm cervical dilatation who requested epidural analgesia were allocated to one of four study groups. After a lumbar epidural catheter was placed, study participants received 20 ml bupivacaine (n = 38), bupivacaine with sufentanil 0.5 [micro sign]g/ml (n = 38), bupivacaine with sufentanil 1 [micro sing]g/ml (n = 33), or bupivacaine with sufentanil 1.5 [micro sign]g/ml (n = 38). The concentration of bupivacaine was determined by the response of the previous patients using up-down sequential allocation. The analgesic efficacy was assessed using 100-mm visual analog pain scores, with <or= to 10 mm within 30 min defined as effective. Results The MLAC of bupivacaine alone was 0.104% wt/vol (95% CI, 0.090 - 0.117). The addition of sufentanil at doses of 0.5 [micro sign]g/ml, 1 [micro sign]g/ml, and 1.5 [micro sign]g/ml resulted in significant reductions (P < 0.0001) in the MLAC of bupivacaine to 0.048% wt/vol (95% CI, 0.030 - 0.065), 0.021% wt/vol (95% CI, 0 - 0.055), and 0.009% wt/vol (95% CI, 0 - 0.023), respectively. Conclusions This study showed a significant (P < 0.0001) dose-dependent reduction in the MLAC of bupivacaine by sufentanil.

Effect of Intravenous versus Epidural Fentanyl 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 (EC50) in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the relative local anesthetic sparing efficacies of intravenous and epidural fentanyl by comparison of their effects on the MLAC of bupivacaine. Methods In this double-blind, randomized, prospective study, 84 parturients at ≤ 7-cm cervical dilation who requested epidural analgesia were allocated to one of two groups. After lumbar epidural catheter placement, 20 ml bupivacaine (n = 44) or bupivacaine with 3 &mgr;g/ml (60 &mgr;g) fentanyl (n = 40) was administered. The plain bupivacaine group then received 60 &mgr;g intravenous fentanyl. The bupivacaine–fentanyl group received intravenous saline. 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 within 30 min defined as effective. Results The MLAC of bupivacaine–intravenous fentanyl was 0.064% wt/vol (95% confidence interval, 0.049–0.080), and the MLAC of bupivacaine–epidural fentanyl was 0.034% wt/vol (95% confidence interval, 0.017–0.050). Epidural fentanyl significantly increased the analgesic potency of bupivacaine by a factor of 1.88 (95% confidence interval, 1.09–3.67) compared with intravenous fentanyl. The epidural fentanyl group demonstrated significantly higher dermatomal spread (P = 0.0064) and increased pruritus (P = 0.01). Conclusions Epidural fentanyl significantly reduced the MLAC of bupivacaine when compared with intravenous fentanyl for the parturients in this study. The significantly enhanced local anesthetic sparing, dermatomal level, and pruritus with epidural fentanyl suggest a primarily spinal site of action.

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 ≤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.

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 &mgr;g) 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 &mgr;g) 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.

The effect of epidural fentanyl on the minimum local analgesic concentration of epidural chloroprocaine in labor

The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration (EC50) in a 20-mL volume in the first stage of labor. The aim of this study was to determine the local anesthetic sparing efficacy of epidural fentanyl by its effect on the MLAC of chloroprocaine. Fifty-six parturients, not exceeding 7 cm cervical dilation, who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After placing a lumbar epidural catheter, 20 mL of the solution being tested was given: chloroprocaine (n = 28) or chloroprocaine with fentanyl 3 micro g/mL (60 micro g) (n = 28). The concentration of chloroprocaine was determined by the response of the previous patient 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. The MLAC of chloroprocaine was reduced from 0.43% wt/vol to 0.26% wt/vol by fentanyl (P = 0.023). Thus, the addition of epidural fentanyl 3 micro g/mL (60 micro g) resulted in a significant 40% reduction in the MLAC of chloroprocaine in the first stage of labor. (Anesth Analg 1996;83:987-90)

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.