Brendan Carvalho

Respiratory Depression After Neuraxial Opioids in the Obstetric Setting

Neuraxial opioids have contributed significantly to improved labor and postcesarean delivery analgesia. In the obstetric population, epidural and intrathecal opioids are associated with a very low risk of clinically significant respiratory depression. Although rare, respiratory depression is a serious risk; patients may die or suffer permanent brain damage as a consequence. This review discusses the mechanism and incidence, as well as the prevention, detection, and management of respiratory depression with morphine, extended-release epidural morphine, and lipophilic opioids in the labor and cesarean delivery setting.

Patient-Controlled Epidural Analgesia for Labor

Patient-controlled epidural analgesia (PCEA) for labor was introduced into clinical practice 20 yr ago. The PCEA technique has been shown to have significant benefits when compared with continuous epidural infusion. We conducted a systematic review using MEDLINE and EMBASE (1988-April 1, 2008) of all randomized, controlled trials in parturients who received PCEA in labor in which one of the following comparisons were made: background infusion versus none; ropivacaine versus bupivacaine; high versus low concentrations of local anesthetics; and new strategies versus standard strategies. The outcomes of interest were maternal analgesia, satisfaction, motor block, and the incidence of unscheduled clinician interventions. A continuous background infusion improved maternal analgesia and reduced unscheduled clinician interventions. Larger bolus doses (more than 5 mL) may provide better analgesia compared with small boluses. Low concentrations of bupivacaine or ropivacaine provide excellent analgesia without significant motor block. Many strategies with PCEA can provide effective labor analgesia. High volume, dilute local anesthetic solutions with a continuous background infusion appear to be the most successful strategy. Research into new delivery strategies, such as mandatory programmed intermittent boluses and computerized feedback dosing, is ongoing.

Single-Dose, Sustained-Release Epidural Morphine in the Management of Postoperative Pain After Elective Cesarean Delivery: Results of a Multicenter Randomized Controlled Study

In this multicenter, randomized, controlled study, we compared the analgesic efficacy and safety profile of a new single-dose extended-release epidural morphine (EREM) formulation (DepoDur™) with that of epidural morphine sulfate for the management of postoperative pain for up to 48 h after elective cesarean delivery. ASA physical status I or II parturients (n = 75) were anesthetized with a combined spinal/epidural technique. Parturients received intrathecal bupivacaine 12–15 mg and fentanyl 10 &mgr;g for spinal anesthesia and a single epidural injection of either 5 mg of standard (conventional preservative-free) morphine or 5, 10, or 15 mg of extended-release morphine after cord clamping for postoperative pain control. Single-dose EREM 10 and 15 mg groups significantly decreased total supplemental opioid medication use and improved functional ability scores for 48 h after surgery compared with those receiving 5 mg of standard morphine. Visual analog scale pain scores at rest and with activity at 24 to 48 h after dosing were significantly better in the 10- and 15-mg single-dose EREM groups versus the standard morphine group. There were no significant differences between the two 5 mg (single-dose EREM and standard morphine) groups. Single-dose EREM was well tolerated, and most adverse events were mild to moderate in severity. Single-dose EREM is a potentially beneficial epidural analgesic for the management of post-cesarean delivery pain and has particular advantages over standard morphine for the period from 24 to 48 h after surgery.

Patient preferences for anesthesia outcomes associated with cesarean delivery

When deciding on neuraxial medication (e.g., spinal opioids) for cesarean delivery (CS) under regional anesthesia, anesthesiologists make treatment decisions that “trade off” relieving pain with the potential for increased risk of side effects. No previous studies have examined obstetric patients’ anesthesia preferences. Researchers administered 100 written surveys to pregnant women attending our institutions’ expectant parent class. We determined patients’ preferences for importance of specific intraoperative and postoperative anesthesia outcomes using priority ranking and relative value scales. We also explored patients’ fears, concerns, and tolerance regarding CS and analgesics. Eighty-two of 100 surveys were returned and analyzed. Pain during and after CS was the greatest concern followed by vomiting, nausea, cramping, pruritus, and shivering. Ranking and relative value scores were closely correlated (R2 = 0.7). Patients would tolerate a visual analog pain score (0–100 mm) of 56 ± 22 before exposing their baby to the potential effects of analgesics they receive. In contrast to previous general surgical population surveys that found nausea and vomiting as primary concerns, we found pain during and after CS as parturients’ most important concern. Common side effects such as pruritus and shivering caused only moderate concern. This information should be used to guide anesthetic choices, e.g., inclusion of spinal opioids given in adequate doses.

Cytokine profile in human skin in response to experimental inflammation, noxious stimulation, and administration of a COX-inhibitor: a microdialysis study.

Abstract Animal studies have documented a critical role for cytokines in cell signaling events underlying inflammation and pain associated with tissue injury. While clinical reports indicate an important role of cytokines in inflammatory pain, methodological limitations have made systematic human studies difficult. This study examined the utility of a human in vivo bioassay combining microdialysis with multiplex immunoassay techniques for measuring cytokine arrays in tissue. The first experiment measured cytokines in interstitial fluid collected from non‐inflamed and experimentally inflamed skin (UVB). The effects of noxious heat on cytokine release were also assessed. The second experiment examined whether anti‐hyperalgesic effects of the COX‐inhibitor ibuprofen were associated with decreased tissue levels of the pro‐inflammatory cytokines IL‐1β and IL‐6. In the first experiment, inflammation significantly increased IL‐1β, IL‐6, IL‐8, IL‐10, G‐CSF, and MIP‐1β. Noxious heat but not experimental inflammation significantly increased IL‐7 and IL‐13. In the second experiment, an oral dose of 400 and 800 mg ibuprofen produced similar anti‐hyperalgesic effects suggesting a ceiling effect. Tissue levels of IL‐1β and IL‐6 were not affected after the 400 mg dose but decreased significantly (44 ± 32% and 38 ± 13%) after the 800 mg dose. These results support the utility of explored method for tracking cytokines in human tissue and suggest that anti‐hyperalgesic and anti‐inflammatory effects of ibuprofen are at least partially dissociated. The data further suggest that high clinical doses of ibuprofen exert anti‐inflammatory effects by down‐regulating tissue cytokine levels. Explored human bioassay is a promising tool for studying the pathology and pharmacology of inflammatory and chronic pain conditions.

Minimum effective bolus dose of oxytocin during elective Caesarean delivery

BACKGROUND The aim of this study was to determine the lowest effective bolus dose of oxytocin to produce adequate uterine tone (UT) during elective Caesarean delivery (CD). METHODS Seventy-five pregnant patients undergoing elective CD under spinal anaesthesia were randomized to receive oxytocin (0.5, 1, 3, 5 units) or placebo. UT was assessed by a blinded obstetrician as either adequate or inadequate, and using a verbal numerical scale score (0-10; 0, no UT; 10, optimal UT) at 2, 3, 6, and 9 min after oxytocin administration. Minimum effective doses of oxytocin were analysed (ED(50) and ED(95)) using logistic regression. Oxytocin-related side-effects (including hypotension) were recorded. RESULTS There were no significant differences in the prevalence of adequate UT among the study groups at 2 min (73%, 100%, 93%, 100%, and 93% for 0, 0.5, 1, 3, and 5 units oxytocin, respectively). The high prevalence of adequate UT after placebo and low-dose oxytocin precluded determination of the ED(50) and ED(95). UT scores were significantly lower in patients receiving 0 unit oxytocin at 2 and 3 min compared with 3 and 5 units oxytocin (P<0.05, respectively). The prevalence of hypotension was significantly higher after 5 units oxytocin vs 0 unit at 1 min (47% vs 7%; P=0.04). CONCLUSIONS The routine use of 5 units oxytocin during elective CD can no longer be recommended, as adequate UT can occur with lower doses of oxytocin (0.5-3 units).

Deficits in the provision of cardiopulmonary resuscitation during simulated obstetric crises.

OBJECTIVE Previous work suggests the potential for suboptimal cardiopulmonary resuscitation (CPR) in the parturient but did not directly assess actual performance. STUDY DESIGN We evaluated 18 videotaped simulations of maternal amniotic fluid embolus and resultant cardiac arrest. A checklist containing 10 current American Heart Association recommendations for advanced cardiac life support (ACLS) in obstetric patients was utilized. We evaluated which tasks were completed correctly and the time required to perform key actions. RESULTS Proper compressions were delivered by our teams 56% of the time and ventilations 50% of the time. Critical interventions such as left uterine displacement and placing a firm back support prior to compressions were frequently neglected (in 44% and 22% of cases, respectively). The mean +/- SD overall composite score for the tasks was 45 +/- 12% (range, 20-60%). The neonatal team was called in a median (interquartile range) of 1:42 (0:44-2:18) minutes:seconds; 15 of 18 (83%) teams called only after the patient was completely unresponsive. Fifty percent of teams did not provide basic information to the neonatal teams as required by neonatal resuscitation provider guidelines. CONCLUSION Multiple deficits were noted in the provision of CPR to parturients during simulated arrests, despite current ACLS certification for all participants. Current requirements for ACLS certification and training for obstetric staff may require revision.

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.

Intraoperative Forced Air-Warming During Cesarean Delivery Under Spinal Anesthesia Does Not Prevent Maternal Hypothermia

BACKGROUND:Prewarming and intraoperative warming with forced air-warming systems prevent perioperative hypothermia and shivering in patients undergoing elective cesarean delivery with epidural anesthesia. We tested the hypothesis that intraoperative lower body forced air-warming prevents hypothermia in patients undergoing elective cesarean delivery with spinal anesthesia. METHODS:Thirty healthy patients undergoing cesarean delivery with spinal anesthesia were randomly assigned to forced air-warming or control groups (identical cover applied with forced air-warming unit switched off). A blinded investigator assessed oral temperature, shivering, and thermal comfort scores at 15-min intervals until discharge from the postanesthetic care unit. Umbilical cord blood gases and Apgar scores were also measured after delivery. RESULTS:The maximum core temperature changes were similar in the two groups (−1.3°C ± 0.4°C vs −1.3°C ± 0.3°C for the forced air-warming group and control group, respectively; P = 0.8). Core hypothermia (≤35.5°C) occurred in 8 of 15 patients receiving forced air-warming and in 10 of 15 unwarmed patients (P = 0.5). The incidence and severity of shivering did not significantly differ between groups. Umbilical cord blood gases and Apgar scores were similar in both groups (P = NS). CONCLUSIONS:We conclude that intraoperative lower body forced air-warming does not prevent intraoperative hypothermia or shivering in women undergoing elective cesarean delivery with spinal anesthesia.

Cardiac Arrest in Pregnancy: A Scientific Statement From the American Heart Association.

This is the first scientific statement from the American Heart Association on maternal resuscitation. This document will provide readers with up-to-date and comprehensive information, guidelines, and recommendations for all aspects of maternal resuscitation. Maternal resuscitation is an acute event that involves many subspecialties and allied health providers; this document will be relevant to all healthcare providers who are involved in resuscitation and specifically maternal resuscitation.