Jose C. A. Carvalho

Ultrasound Using the Transverse Approach to the Lumbar Spine Provides Reliable Landmarks for Labor Epidurals

BACKGROUND: Ultrasound imaging of the spine has recently been proposed to facilitate identification of the epidural space. In this study, we assessed the accuracy and precision of the transverse approach, using a “single-screen” method, to facilitate labor epidurals. METHODS: We enrolled 61 patients requesting labor epidurals. Ultrasound imaging (transverse approach, 2–5 MHz curved array probe) identified the midline, the intervertebral space, and the distance from the skin to the epidural space (ultrasound depth/UD). During the epidural puncture, we recorded the success of the insertion point, and measured the distance to the epidural space to the nearest half-centimeter of the marked Tuohy needle (needle depth/ND). We calculated the agreement between UD and ND by the concordance correlation coefficient and Bland–Altman analysis with 95% limits of agreement. RESULTS: The average maternal age was 33 ± 4.6 yr, body mass index 29.7 ± 4.8, UD 4.66 ± 0.68 cm, and ND 4.65 ± 0.72 cm. The success of the insertion point was 91.8%, with no need to redirect the needle in 73.8% of the patients. The concordance correlation coefficient between UD and ND was 0.881 (95% CI 0.820–0.942). The 95% limits of agreement were −0.666 to 0.687 cm. CONCLUSIONS: We found a good level of success in the ultrasound-determined insertion point, and very good agreement between UD and ND. This suggests that our proposed ultrasound single-screen method, using the transverse approach, can be a reliable guide to facilitate labor epidural insertion.

Oxytocin requirements at elective cesarean delivery: a dose-finding study.

OBJECTIVE: Oxytocin is frequently used by intravenous bolus and infusion to minimize blood loss and prevent postpartum hemorrhage at cesarean delivery. Current dosing regimens are arbitrary whereas large doses may pose a serious risk to the mother. The purpose of this study was to estimate the minimum effective intravenous bolus dose of oxytocin (ED90) required for adequate uterine contraction at elective cesarean in nonlaboring women. METHODS: A randomized, single-blinded study was undertaken in 40 healthy term pregnant women presenting for elective cesarean under spinal anesthesia. Oxytocin was administered by bolus according to a biased coin up-and-down sequential allocation scheme with increments or decrements of 0.5 IU. Uterine contraction was assessed by the obstetrician, who was blinded to the dose of oxytocin, as either satisfactory or unsatisfactory. After achieving sustained uterine contraction, an infusion of 40 mU/min of oxytocin was started. Oxytocin-induced adverse effects and intraoperative complications were recorded and blood loss was estimated. Data were interpreted by parametric analysis based on logistic regression model and nonparametric analyses at 95% confidence intervals (CIs). RESULTS: The ED90 of oxytocin as determined by logistic regression model fitted to the data was estimated to be 0.35 IU (95% CI 0.18–0.52 IU), with nonparametric estimates of 97.1% (95% CI 84.9–99.8%) response rate at 0.5 IU, and 100% (95% CI 92.2–100%) at 1.0 IU. The estimated blood loss was 693 ± 487 mL (mean ± standard deviation). CONCLUSION: The bolus dose of oxytocin used at elective cesarean deliveries in nonlaboring women can be significantly reduced while maintaining effective uterine contraction. Alteration in practice will likely reduce the potential adverse effects of this drug when given in large bolus doses, but may require modification of the techniques to remove the placenta.

Ultrasound Imaging of the Lumbar Spine in the Transverse Plane: The Correlation Between Estimated and Actual Depth to the Epidural Space in Obese Parturients

BACKGROUND: Prepuncture lumbar ultrasound scanning is a reliable tool to facilitate labor epidural needle placement in nonobese parturients. In this study, we assessed prepuncture lumbar ultrasound scanning as a tool for estimating the depth to the epidural space and determining the optimal insertion point in obese parturients. METHODS: We studied 46 obese parturients, with prepregnancy body mass index (BMI) >30 kg/m2, requesting labor epidural analgesia. Ultrasound imaging was done by one of the investigators to identify the midline, the intervertebral space, and the distance from the skin to the epidural space (ultrasound depth, UD) at the level of L3–4. Subsequently, an anesthesiologist blinded to the UD located the epidural space through the predetermined insertion point and marked the actual distance from the skin to the epidural space (needle depth, ND) on the needle with a sterile marker. The agreement between the UD and the ND was calculated using the Pearson correlation coefficient and a paired t-test. Bland-Altman analysis was used to determine the 95% limits of agreement between the UD and the ND. RESULTS: The prepregnancy BMI ranged from 30 to 79 kg/m2, and the BMI at delivery was 33–86 kg/m2. The Pearson correlation coefficient between the UD and the ND was 0.85 (95% confidence interval: 0.75–0.91), and the concordance correlation coefficient was 0.79 (95% confidence interval: 0.71–0.88). The mean (±sd) ND and UD were 6.6 ± 1.0 cm and 6.3 ± 0.8 cm, respectively (difference = 0.3 cm, P = 0.002). The 95% limits of agreement were 1.3 cm to −0.7 cm. Epidural needle placement using the predetermined insertion point was done without reinsertion at a different puncture site in 76.1% of parturients and without redirection in 67.4%. CONCLUSIONS: We found a strong correlation between the ultrasound-estimated distance to the epidural space and the actual measured needle distance in obese parturients. We suggest that prepuncture lumbar ultrasound may be a useful guide to facilitate the placement of epidural needles in obese parturients.

Ultrasound imaging for lumbar punctures and epidural catheterisations: systematic review and meta-analysis

Objective To determine whether ultrasound imaging can reduce the risk of failed lumbar punctures or epidural catheterisations, when compared with standard palpation methods, and whether ultrasound imaging can reduce traumatic procedures, insertion attempts, and needle redirections. Design Systematic review and meta-analysis of randomised controlled trials. Data sources Ovid Medline, Embase, and Cochrane Central Register of Controlled Trials up to May 2012, without restriction by language or publication status. Review methods Randomised trials that compared ultrasound imaging with standard methods (no imaging) in the performance of a lumbar puncture or epidural catheterisation were identified. Results 14 studies with a total of 1334 patients were included (674 patients assigned to the ultrasound group, 660 to the control group). Five studies evaluated lumbar punctures and nine evaluated epidural catheterisations. Six of 624 procedures conducted in the ultrasound group failed; 44 of 610 procedures in the control group failed. Ultrasound imaging reduced the risk of failed procedures (risk ratio 0.21 (95% confidence interval 0.10 to 0.43), P<0.001). Risk reduction was similar when subgroup analysis was performed for lumbar punctures (risk ratio 0.19 (0.07 to 0.56), P=0.002) or epidural catheterisations (0.23 (0.09 to 0.60), P=0.003). Ultrasound imaging also significantly reduced the risk of traumatic procedures (risk ratio 0.27 (0.11 to 0.67), P=0.005), the number of insertion attempts (mean difference −0.44 (−0.64 to −0.24), P<0.001), and the number of needle redirections (mean difference −1.00 (−1.24 to −0.75), P<0.001). Conclusions Ultrasound imaging can reduce the risk of failed or traumatic lumbar punctures and epidural catheterisations, as well as the number of needle insertions and redirections. Ultrasound may be a useful adjunct for these procedures.

Small doses of intrathecal morphine combined with systemic diclofenac for postoperative pain control after cesarean delivery

Postoperative pain control after cesarean delivery under spinal anesthesia is effectively obtained with morphine 0.1-0.3 mg intrathecally, although there may be dose-dependent side effects. We evaluated the quality of analgesia and the incidence of side effects with smaller doses of intrathecal morphine combined with intramuscular (IM) diclofenac. One hundred-twenty pregnant patients were allocated into six groups, which received the following treatments: Groups 1, 3, and 5 received 0.1, 0.05, and 0.025 mg of intrathecal morphine, respectively, plus 75 mg of IM diclofenac every 8 h; Groups 2, 4, and 6 received 0.1, 0.05, and 0.025 mg of intrathecal morphine, respectively, plus IM diclofenac on demand. Spinal anesthesia was performed with 15 mg of 0.5% hyperbaric bupivacaine. Pain scores and side effects were evaluated hourly for the first 24 h. Groups 1 and 2 had lower pain scores than Groups 3, 4, 5, and 6. However, only patients in Groups 2, 4, and 6 requested additional analgesics. Severe pruritus was more frequent in Groups 1 and 2. No patient experienced respiratory depression. We conclude that there is no advantage in using doses larger than 0.025 mg of intrathecal morphine if they are combined with systemic diclofenac. Implications: A multimodal approach to pain control may provide good quality analgesia while reducing drug-related side effects. In this study, a very small dose of intrathecal morphine, in association with intramuscular diclofenac, proved effective for controlling pain after cesarean delivery, with a low incidence of morphine-induced pruritus. (Anesth Analg 1998;86:538-41)

Minimum Oxytocin Dose Requirement After Cesarean Delivery for Labor Arrest

OBJECTIVE: To estimate the minimum effective intravenous dose of oxytocin required for adequate uterine contraction after cesarean delivery for labor arrest. METHODS: A randomized single-blinded study was undertaken in 30 parturients undergoing cesarean deliveries under epidural anesthesia for labor arrest despite intravenous oxytocin augmentation. Oxytocin was administered as a slow intravenous bolus immediately after delivery of the infant, according to a biased coin up-down sequential allocation scheme. After assisted spontaneous delivery of the placenta, the obstetrician, blinded to the oxytocin dose, assessed uterine contraction as either satisfactory or unsatisfactory. Additional boluses of oxytocin were administered as required, followed by a maintenance infusion. Data were interpreted and analyzed by a logistic regression model at 95% confidence intervals. RESULTS: All patients received oxytocin infusions at a mean ± standard deviation of 9.8 ± 6.3 hours before cesarean delivery (maximum infusion dose 10.3 ± 8.2 mU/min). The minimum effective dose of oxytocin required to produce adequate uterine response in 90% of women (ED90) was estimated to be 2.99 IU (95% confidence interval 2.32–3.67). The estimated blood loss was 1,178 ± 716 mL. CONCLUSION: Women requiring cesarean delivery for labor arrest after oxytocin augmentation require approximately 3 IU rapid intravenous infusion of oxytocin to achieve effective uterine contraction after delivery. This dose is 9 times more than previously reported after elective cesarean delivery in nonlaboring women at term, suggesting oxytocin receptor desensitization from exogenous oxytocin administration during labor. Therefore, alternative uterotonic agents, rather than additional oxytocin, may achieve superior uterine contraction and control of blood loss during cesarean delivery for labor arrest. LEVEL OF EVIDENCE: I

Remifentanil patient-controlled analgesia for labour: optimizing drug delivery regimens.

PurposeA pilot study was undertaken to compare the efficacy of two regimens of intravenous patient-controlled analgesia (PCA) with remifentanil for labour analgesia.MethodsTwenty term parturients requesting labour analgesia were randomized to receive one of two regimens of intravenous remifentanil. The initial settings in both groups consisted of an infusion of 0.025 μg·kg-1·min-1, a PCA bolus of 0.25 μg·kg-1 and a lockout interval of two minutes. In Group A, the infusion was increased in a stepwise manner from 0.025 to 0.05, 0.075 and 0.1 μg·kg-1·min-1 as required; the bolus was kept constant at 0.25 μg·kg-1. In Group B, the bolus was increased from 0.25 to 0.5, 0.75 and 1 μg·kg-1 as necessary; the infusion was kept constant at 0.025 μg·kg-1·min-1. Maternal pain, satisfaction and sedation scores, remifentanil requirement, and side effects were recorded.ResultsMean pain and patient satisfaction scores, and cumulative doses of remifentanil were similar in the two groups. The overall incidence of side effects was greater in Group B (P = 0.0007), with drowsiness observed in 100% of patients, as compared to 30% in Group A (P = 0.003). The minimum oxygen saturation levels were 94.3% ± 2.6% and 92.2% ± 3.8% in Groups A and B respectively (P = 0.19).ConclusionsAlthough pain and satisfaction scores were similar in both groups, the regimen used in Group A was associated with fewer side effects compared to the Group B dosing regimen. This pilot study suggests that remifentanil intravenous PCA is efficacious for labour analgesia as a bolus of 0.25 μg·kg-1, with a lockout interval of two minutes and continuous infusion of 0.025-0.1 μg·kg-1·min-1. The potential for respiratory depression mandates close respiratory monitoring. Large-scale trials to evaluate safety issues are warranted.RésuméObjectifUne étude pilote a été entreprise afin de comparer l’efficacité de deux régimes intraveineux d’analgésie contrôlée par le patient (ACP) avec du rémifentanil pour le travail obstétrical.MéthodeVingt parturientes à terme demandant une analgésie pour le travail ont été randomisées à recevoir l’un de deux régimes de rémifentanil intraveineux. Les réglages de base dans les deux groupes consistaient en une perfusion de 0,025 μg·kg-1 ·min-1, un bolus ACP de 0,25 μg·kg-1 et un intervalle d’interdiction de deux minutes. Dans le groupe A, la perfusion a été augmentée par paliers de 0,025 à 0,05, 0,075 et 0,1 μg·kg-1 ·min-1 au besoin; le bolus a été maintenu constant à 0,25 μg·k-1. Dans le groupe B, le bolus a été augmenté de 0,25 à 0,5, 0,75 et 1 μg·kg-1 au besoin; la perfusion a été maintenue constante à 0,025 μg·kg-1·min-1. Les douleurs maternelles, les scores de satisfaction et de sédation, les besoins en rémifentanil et les effets secondaires ont été enregistrés.RésultatLes scores moyens de douleur et de satisfaction des patientes ainsi que les doses cumulatives de rémifentanil ont atteint des résultats similaires dans les deux groupes. L’incidence totale d’effets secondaires était plus élevée dans le groupe B(P = 0,007), avec des cas de somnolence chez 100 % des patientes comparativement à 30 % dans le groupe A (P = 0,003). Le minimum de saturation en oxygène était de 94,3 % ± 2,6% et 92,2 % ± 3,8 % dans les groupes A et B respectivement (P = 0,19).ConclusionBien que les scores de douleur et de satisfaction étaient similaires dans les deux groupes, le régime utilisé par le groupe A a été associé à moins d’effets secondaires que le régime de dosage du groupe B. Cette étude pilote suggère que l’ACP intraveineuse au rémifentanil est efficace pour l’analgésie pour le travail en bolus de 0,25 μg·kg-1, avec un intervalle d’interdiction de deux minutes et une perfusion continue de 0,025 - 0,1 μg·kg-1 ·min-1. Toutefois, un monitorage respiratoire attentif est nécessaire en raison du potentiel de développement de dépressions respiratoires. Des essais à grande échelle pour évaluer les questions d’innocuité sont requis.

The Society for Obstetric Anesthesia and Perinatology Consensus Statement on the Management of Cardiac Arrest in Pregnancy

This consensus statement was commissioned in 2012 by the Board of Directors of the Society for Obstetric Anesthesia and Perinatology to improve maternal resuscitation by providing health care providers critical information (including point-of-care checklists) and operational strategies relevant to maternal cardiac arrest. The recommendations in this statement were designed to address the challenges of an actual event by emphasizing health care provider education, behavioral/communication strategies, latent systems errors, and periodic testing of performance. This statement also expands on, interprets, and discusses controversial aspects of material covered in the American Heart Association 2010 guidelines.

Gabapentin Improves Postcesarean Delivery Pain Management: A Randomized, Placebo-Controlled Trial

BACKGROUND:Gabapentin is effective for preventing and treating acute and chronic postoperative pain; however, it has not been described for use in cesarean delivery. We hypothesized that preoperative gabapentin would reduce postcesarean delivery pain. METHODS:Women undergoing scheduled cesarean delivery were randomized to receive preoperative gabapentin 600 mg, or placebo. Spinal anesthesia was achieved with 0.75% hyperbaric bupivacaine 12 mg, fentanyl 10 &mgr;g, and morphine 100 &mgr;g. Postoperative analgesia was initiated with intraoperative ketorolac and acetaminophen, and continued with postoperative diclofenac, acetaminophen, and morphine. Patients were assessed at 6, 12, 24, and 48 hours after spinal anesthesia for pain at rest and on movement using a visual analog scale (0 to 100 mm), satisfaction, opioid consumption, and side effects. Neonatal interventions, Apgar scores, umbilical artery blood gases, and breastfeeding difficulties were assessed. Chronic pain was assessed 3 months after delivery. Maternal and umbilical vein gabapentin plasma concentrations were measured in a subgroup of patients. Mixed-model analysis was used to compare the primary outcome of visual analog scale pain scores at 24 hours between groups. RESULTS:Forty-six patients were randomized, and 2 were excluded from analysis. The mean (95% confidence interval, CI) pain scores on movement at 24 hours were 21 mm (CI = 13–28) in the gabapentin and 41 mm (CI = 31–50) in the placebo group (P = 0.001). Maternal satisfaction was higher in the gabapentin group. There was no difference in opioid consumption. Severe maternal sedation was more common in the gabapentin group (19% vs. 0%, P = 0.04). There was no difference in neonatal Apgar scores, interventions, or umbilical artery pH. The mean (SD) maternal vein:umbilical vein plasma gabapentin ratio was 0.86 (0.12). The incidence of pain at 3 months was similar in both groups. CONCLUSION:Preoperative gabapentin 600 mg in the setting of multimodal analgesia reduces postcesarean delivery pain and increases maternal satisfaction in comparison with placebo.

Management of cardiac arrest in pregnancy: a systematic review.

OBJECTIVE To describe the consensus on science pertaining to resuscitation of the pregnant patient. DESIGN Systematic review. DATA SOURCES EMBASE, Ovid MEDLINE, Evidence Based Reviews, American Heart Association library and bibliographies of selected articles. REVIEW METHODS The following inclusion criteria were used: pregnancy and cardiac arrest out of hospital, pregnancy and cardiac arrest in hospital, cardiovascular, respiratory, fetal survival, and pharmacology as they relate to cardiac arrest and resuscitation. Non-English papers, case reports and reviews were excluded. Studies were selected through an independent review of titles, abstracts and full article. Two reviewers independently graded the methodological quality of selected articles. RESULTS 1305 articles were identified and 5 were selected for further review. There were no randomized trials and overall the quality of the selected studies was good. Two studies examined chest compressions on a manikin in left lateral tilt from the horizontal and concluded that although feasible with increasing degrees of tilt forcefulness of the chest compressions decreases. The third study observed the transthoracic impedance was not altered during pregnancy. One case series and one retrospective cohort study reviewed perimortem cesarean section. Both reports concluded that perimortem cesarean section is rarely done within the recommended time frame of 5 min after the onset of maternal cardiac arrest. CONCLUSIONS Usual defibrillation dosages are likely appropriate in pregnancy. Perimortem cesarean section is an intervention which is rarely done within 5 min to optimize maternal salvage from cardiac arrest. Chest compressions in left lateral tilt are less forceful compared to the supine position.