Alexander J. Butwick

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).

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.

Postpartum hemorrhage treated with a massive transfusion protocol at a tertiary obstetric center: A retrospective study

BACKGROUND A massive transfusion protocol may offer major advantages for management of postpartum hemorrhage. The etiology of postpartum hemorrhage, transfusion outcomes and laboratory indices in obstetric cases requiring the massive transfusion protocol were retrospectively evaluated in a tertiary obstetric center. METHODS We reviewed medical records of obstetric patients requiring the massive transfusion protocol over a 31-month period. Demographic, obstetric, transfusion, laboratory data and adverse maternal outcomes were abstracted. RESULTS Massive transfusion protocol activation occurred in 31 patients (0.26% of deliveries): 19 patients (61%) had cesarean delivery, 10 patients (32%) had vaginal delivery, and 2 patients (7%) had dilation and evacuation. Twenty-six patients (84%) were transfused with blood products from the massive transfusion protocol. The protocol was activated within 2h of delivery for 17 patients (58%). Median [IQR] total estimated blood loss value was 2842 [800-8000]mL. Median [IQR] number of units of red blood cells, plasma and platelets from the massive transfusion protocol were: 3 [1.75-7], 3 [1.5-5.5], and 1 [0-2.5] units, respectively. Mean (SD) post-resuscitation hematologic indices were: hemoglobin 10.3 (2.4)g/dL, platelet count 126 (44)×10(9)/L, and fibrinogen 325 (125)mg/dL. The incidence of intensive care admission and peripartum hysterectomy was 61% and 19%, respectively. CONCLUSIONS Our massive transfusion protocol provides early access to red blood cells, plasma and platelets for patients experiencing unanticipated or severe postpartum hemorrhage. Favorable hematologic indices were observed post resuscitation. Future outcomes-based studies are needed to compare massive transfusion protocol and non-protocol based transfusion strategies for the management of hemorrhage.

Non-invasive haemoglobin measurement in patients undergoing elective Caesarean section

BACKGROUND The ability to measure haemoglobin (Hb) real-time and non-invasively offers important clinical value in the assessment of acute changes in maternal Hb during the peripartum period. This study evaluates the Masimo Rainbow SET(®) Radical-7 Pulse CO-Oximeter in a pregnant population undergoing Caesarean section (CS). METHODS Fifty patients undergoing elective CS were enrolled in this prospective, controlled study and followed for 48 h after surgery. Non-invasive Masimo Hb (SpHb) values were compared with laboratory Hb values from venous blood samples drawn at baseline, immediately post-CS, and 24 h post-CS using the Bland-Altman plots. Longitudinal analysis of SpHb changes over time was performed using mixed-effects regression modelling. RESULTS For the comparison between SpHb and laboratory Hb, SpHb displayed a significant positive bias at baseline {1.22 g dl(-1) [95% confidence interval (CI): 0.89-1.54]} and at 24 h post-CS [1.36 g dl(-1) (95% CI: 1.04-1.68)]. The bias immediately post-CS was 0.14 g dl(-1) (95% CI: -0.18 to 0.46). The limits of agreement at baseline, immediately post-CS, and at 24 h post-CS were: -0.9 and 3.33, -2.35 and 2.56, and -0.55 and 3.27 g dl(-1), respectively. The mean decrease in SpHb from baseline to 48 h post-CS was ∼1 g dl(-1). CONCLUSIONS The variability in bias and limits of agreements of the Rainbow SET(®) Radical-7 Pulse CO-Oximeter SpHb may limit its clinical utility for assessing Hb concentration in patients undergoing elective CS. Modifications are needed in the calibration of the device to improve accuracy and precision in an obstetric setting. The study was registered at clinicaltrials.gov (NCT01108471) before participant enrolment: URL=http://clinicaltrials.gov/ct2/show/NCT01108471?term=butwick&rank=1.

Oxytocin for labour and caesarean delivery: implications for the anaesthesiologist

Purpose of review The implications of the obstetric use of oxytocin for obstetric anaesthesia practice are summarised. The review focuses on recent research on the uterotonic effects of oxytocin for prophylaxis and management of uterine atony during caesarean delivery. Recent findings Oxytocin remains the first-line agent in the prevention and management of uterine atony. In-vitro and in-vivo studies show that prior exposure to oxytocin induces uterine muscle oxytocin receptor desensitization. This may influence oxytocin dosing for adequate uterine tone following delivery. Oxytocin has important cardiovascular side-effects (hypotension, tachycardia and myocardial ischaemia). Recent studies suggest that the effective dose of oxytocin for prophylaxis against uterine atony during caesarean delivery is significantly lower than the 5–10 IU historically used by anaesthesiologists. Slow administration of small bolus doses of oxytocin minimises maternal haemodynamic disturbance. Continuous oxytocin infusions are recommended for maintaining uterine tone after bolus administration, although ideal infusion rates are still to be established. The efficacy of the long-acting oxytocin analogue carbetocin requires further investigation. Recommendations are presented for oxytocin dosing during caesarean delivery. Summary Oxytocin remains the first-line uterotonic after vaginal and caesarean delivery. Recent research elucidates the therapeutic range of oxytocin during caesarean delivery, as well as receptor desensitization. Evidenced-based protocols for the prevention and treatment of uterine atony during caesarean delivery are recommended.

The effect of colloid and crystalloid preloading on thromboelastography prior to Cesarean delivery

PurposeFluid preloading with colloids reduces hypotension after spinal anesthesia for Cesarean delivery more effectively than crystalloids. However, the effects of fluid preloading regimens on coagulation in pregnant patients remain unresolved. The aim of this study was to compare the effects on coagulation of fluid preloading with 6% hydroxyethyl starch (HES) and lactated Ringer’s (LR) solution using thromboelastography (TEG) with kaolin-activated whole blood in healthy pregnant patients prior to spinal anesthesia for Cesarean delivery.MethodsAfter obtaining Ethics committee approval, 30 parturients were prospectively randomized prior to spinal anesthesia for elective Cesarean delivery to receive fluid preloading with either 1500 mL LR or 500 mL 6% HES over 30 min. Thromboelastography was performed immediately prior to and after fluid preloading. Standard TEG parameters were analyzed in terms of r time (min), k time (min), α angle (degrees) and maximum amplitude (mm).ResultsGroup HES had statistically significant longer reaction times (r) and clot formation times (k) after fluid loading compared to baseline values (P < 0.05 respectively), although these post-fluid loading TEG parameters remained within a normal reference range. No significant differences in TEG values were seen after preloading within the LR group.ConclusionFluid preloading with 500 mL 6% HES in healthy parturients produced mild coagulation effects, as measured with TEG, prior to spinal anesthesia for Cesarean delivery. No significant effects on coagulation with TEG were observed following preloading with 1500 mL LR.RésuméObjectifLa précharge liquidienne avec un colloïde plutôt qu’avec un cristalloïde réduit plus efficacement l’hypotension associée à la rachianesthésie lors de l’accouchement par césarienne. Toutefois, les effets de l’administration d’une précharge liquidienne sur la coagulation chez les patientes enceintes demeurent inconnus. L’objectif de cette étude était de comparer les effets sur la coagulation d’une précharge liquidienne avec de l’amidon hydroxyéthylé (AHE) 6 % et une solution de lactate Ringer (LR) en utilisant un thromboélastogramme (TEG) avec du sang complet activé au kaolin chez les patientes enceintes saines avant la rachianesthésie pour l’accouchement par césarienne.MéthodesAvec l’approbation du comité d’éthique, 30 parturientes ont été prospectivement randomisées, avant la rachianesthésie pour l’accouchement par césarienne, à recevoir une précharge liquidienne de 1 500 mL LR ou 500 mL AHE 6 % en 30 min. Un thromboélastogramme a été effectué immédiatement avant et après l’administration de la précharge liquidienne. Les paramètres standard du TEG ont été utilisés en fonction du temps r (min), du temps k (min), de l’angle α (degrés) et de l’amplitude maximum (mm).RésultatsLe groupe AHE a présenté des temps de réaction (r) et de formation de caillots (k) statistiquement plus longs après charge liquidienne en comparaison des valeurs de base (P < 0,05 respectivement), bien que ces paramètres de TEG après charge liquidienne soient restés dans une marge de référence normale. Aucune différence significative dans les valeurs du TEG n’a été observée après précharge dans le groupe RL.ConclusionLa précharge liquidienne avec 500 mL de AHE 6 % chez les parturientes en bonne santé a eu des effets légers sur la coagulation selon les mesures prises avec le TEG avant la rachianesthésie pour accouchement par césarienne. Aucun effet significatif sur la coagulation avec TEG n’a été observé suite à une précharge de 1 500 mL LR.

Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor?

OBJECTIVE The purpose of this study was to examine cesarean delivery morbidity and its predictors in the United States. STUDY DESIGN We used 2000-2011 Nationwide Inpatient Sample data to identify cesarean deliveries and records with 12 potential cesarean delivery complications, including placenta accreta. We estimated cesarean delivery morbidity rates and rate changes from 2000-2011, and fitted Poisson regression models to assess the relative incidence of morbidity among repeat vs primary cesarean deliveries and explore its predictors. RESULTS From 2000-2011, 76 in 1000 cesarean deliveries (97 in 1000 primary and 48 in 1000 repeat cesarean deliveries) were accompanied by ≥1 of 12 complications. The unadjusted composite cesarean delivery morbidity rate increased by 3.6% only among women with a primary cesarean delivery (P < .001); the unadjusted rate of placenta accreta increased by 30.8% only among women with a repeat cesarean deliveries (P = .025). The adjusted rate of overall composite cesarean delivery morbidity decreased by 1% annually from 2000-2011 (P < .001). Compared with women with a primary cesarean delivery, those women who underwent a repeat cesarean delivery were one-half as likely (incidence rate ratio, 0.50; 95% CI, 0.49-0.50) to experience a complication, but 2.13 (95% CI, 1.98-2.29) times more likely to have a placenta accreta diagnosis. Both cesarean delivery morbidity and placenta accreta were positively associated with age >30 years, non-Hispanic black race/ethnicity, the presence of a chronic medical condition, and delivery in urban, teaching, or larger hospitals. CONCLUSION Overall, cesarean delivery morbidity declined modestly from 2000-2011, but placenta accreta became an increasingly important contributor to repeat cesarean delivery morbidity. Clinicians should maintain a high index of suspicion for abnormal placentation and make adequate preparations for patients who need cesarean deliveries.

A survey of perioperative and postoperative anesthetic practices for cesarean delivery.

The aim of this survey was to review cesarean delivery anesthetic practices. An online survey was sent to members of the Society of Obstetric Anesthesia and Perinatology (SOAP). The mode of anesthesia, preferred neuraxial local anesthetic and opioid agents, postoperative analgesic regimens, and monitoring modalities were assessed. 384 responses from 1,081 online survey requests were received (response rate = 36%). Spinal anesthesia is most commonly used for elective cesarean delivery (85% respondents), with 90% of these respondents preferring hyperbaric bupivacaine 0.75%. 79% used intrathecal fentanyl and 77% used morphine (median [range] dose 200 mcg [50–400]). 91% use respiratory rate, 61% use sedation scores, and 30% use pulse oximetry to monitor for postoperative respiratory depression after administration of neuraxial opioids. Postoperative analgesic regimens include: nonsteroidal anti-inflammatory agents, acetaminophen, oxycodone, and hydrocodone by 81%, 45%, 25%, and 27% respondents respectively. The majority of respondents use spinal anesthesia and neuraxial opioids for cesarean delivery anesthesia. There is marked variability in practices for monitoring respiratory depression postdelivery and for providing postoperative analgesia. These results may not be indicative of overall practice in the United States due to the select group of anesthesiologists surveyed and the low response rate.

Neuraxial anesthesia in obstetric patients receiving anticoagulant and antithrombotic drugs

Anticoagulation is indicated for a variety of obstetricand medical conditions in women of childbearing age.Recent guidelines from national and international orga-nizations, the Pregnancy and Thrombosis WorkingGroup and the American College of Chest Physicians,have highlighted the importance of anticoagulant ther-apy in the prophylaxis and treatment of venous throm-boembolism in pregnancy, and in pregnant patients withmechanical heart valves.

Postpartum hemorrhage and low fibrinogen levels: the past, present and future

‘‘Change is the law of life. And those who look only to thepast or present are certain to miss the future.’’John F. KennedyAre rates and outcomes after postpartum hemorrhage(PPH)gettinganybetter?Well...thereissomegoodnewsandbadnews.Accordingtorecentmaternalmortalityre-views, the good news is that the proportion of maternaldeaths due to hemorrhage appears to be decreasing:3.4% and 12% of maternal deaths in the UK (2006–2008)