Obstetric Anesthesia

General Anesthesia for Cesarean

This retrospective study spanned a decade but included nearly half a million Cesarean Sections in New York State.

5.7% were classified as GA without a recorded indication. The study found: “The use of potentially avoidable general anesthesia in these patients is associated with an increased risk of anesthesia-related complications, surgical site infection, and venous thromboembolism, but not death or cardiac arrest”. The odds were quite significantly higher.

Risk factors for GA included age less than 19, racial or ethnic minority, Medicaid or Medicare beneficiaries, preexisting or pregnancy-associated conditions, nonelective admission, and admission during weekend, teaching hospital, neonatal level-of-care designation 1 or 3, lower use of neuraxial techniques during labor and vaginal deliveries, higher annual volume of deliveries, and higher proportion of women with a comorbidity index greater than 2.

Neuraxial anesthesia is established as the standard of care in Cesarean anesthesia absent contraindication. Higher labor epidural rates appeared to be the most actionable factor to encourage and increase the odds of neuraxial anesthesia.

Many of the other factors are either known or subject to the limitations of this retrospective study, and may be subject to coding inaccuracy, malfunctioning epidural catheters, or patient request.

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Cholecystectomy during Pregnancy

There has been a general opinion and comfort level with the safety of gall bladder surgery during pregnancy. One of the more reassuring findings in this study is that 90% were done after pregnancy, as the findings are not entirely supportive of existing recommendations.

They found “Women who have their gallbladder removed during pregnancy are more likely to experience longer hospital stays, increased 30-day readmissions, and higher rates of preterm delivery than those who delay the operation until after childbirth”. Pre-eclampsia and hemorrhage rates were also higher, as was open surgery.

It should be noted that they only studied third trimester vs. postpartum and not earlier during pregnancy. It certainly is possible that a subset of patients could benefit from cholecystectomy during pregnancy.

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Peripartum Cardiomyopathy

Of interest to obstetric anesthesiologists, a BMJ current review of this rare but serious dilated cardiomyopathy with systolic dysfunction that presents in late pregnancy or, more commonly, the early postpartum period.

Risk factors include black ancestry, pre-eclampsia, advanced maternal age, and multiple gestation pregnancy. Half recover but many more are left with chronic disease and a minority require mechanical support and/or transplantation.

Features are common to heart failure, and also include arrhythmias and thromboembolism (anticoagulation for which will impact neuraxial anesthesia). General treatment measures are discussed and potential specific treatments, including Bromocriptine for Prolactin inhibition, a postulated mechanism in etiology.

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Carbetocin in Elective Cesarean Section

Maternal postpartum hemorrhage is a common complication and indeed accounts for the highest fraction of global maternal mortality (35%).

Routine uterotonics are recommended after delivery as they significantly reduce hemorrhage. Oxytocin is well known, but SOGC recommended a single 100 μg i.v. bolus dose of carbetocin over 1 min (in lieu of an oxytocin infusion) as the uterotonic agent of choice to prevent PPH after elective caesarean delivery; the rationale is that its duration of action is 4 to 7 times that of Oxytocin. This dose comes from manufacturers recommendations.

This randomized non-inferiority design study tested 20mcg vs. 100mcg Carbetocin in elective Cesarean under Spinal Anesthesia.

Uterine tone at 2mins did not meet criteria but 20mcg was non-inferior to 100mcg at 5 mins in terms of uterine tone and hemorrhage as well as the need for further uterotonics.

The numerical rating score for uterine tone may be operator dependent and subjective but the authors suggest further studies to assess the clinical significance of their findings, as all other side effects were basically similar. The study may be underpowered in terms of numbers.

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Colloid and Crystalloid for Cesarean Spinal

There seems (yet again) little rationale for giving colloids, this time in co-loading fluid for Cesarean Section under spinal anesthesia. This study found that the combination of 500-mL colloid preload and 500-mL crystalloid coload did not reduce the total ephedrine dose or improve other maternal outcomes compared with 1000-mL crystalloid coload, although vena caval diameter changes were noted with ultrasound. Neither were there any significant differences in the incidence of hypotension and severe hypotension, the time to the first ephedrine dose, and neonatal Apgar scores at 1 and 5 minutes.

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High Flow Nasal Oxygen vs. Facemask Preoxygenation

Two studies compare high flow nasal oxygen (HFNO) with facemask preoxygenation, one in obstetrics. Both reach the same conclusion in that HFNO is inferior to standard facemask preoxygenation.

HFNO, or simply a maximally cranked nasal cannula placed under the facemask have both been shown to increase apnea time and desaturation during difficult intubations but as a stand-alone measure are inadequate to optimize oxygenation prior to anesthesia induction.

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Intrathecal Fentanyl for Cesarean Delivery

This study validates the common use of Fentanyl in spinal anesthesia for Cesarean delivery. It reduces the need for intraoperative supplemental analgesia, reduces nausea and vomiting, with longer time for postoperative first analgesia request, and similar benefits were observed when added to Bupivacaine-Morphine spinals.

There was no difference in conversion to GA, hypotension, the onset of sensory block, or the duration of motor block. The only downside was an increase in pruritus.

The study was a systematic review and meta-analysis.

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Labor Neuraxial Analgesia Variation

Labor epidurals should be available for all births on maternal request unless contraindicated. This US study found quite a variation between states in neuraxial labor analgesia – from 37 – 80%.

Higher rates were associated with no prior birth, previous Cesarean, labor augmentation or induction. Factors inversely associated with neuraxial analgesia were older maternal age, nonwhite race and Hispanic ethnicity, no private insurance or no insurance, twelfth grade or less as the highest level of education, and late or no prenatal care, and the odds reduced with non-physician birth attendants and midwives.

Efforts should be made to decipher the meaning of these variations in terms of sociodemographic and economic influences, disparity, vulnerable groups and access to quality obstetric anesthesia care.

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Anesthesiologist Specialization and Use of General Anesthesia for Cesarean Delivery

A single institution study using data extracted from electronic medical records compares generalist vs. specialized anesthesiologists with regard to general anesthesia for Cesarean delivery.

Specialized providers had a 29% less use of general anesthesia (7.3% vs. 12.1%, 4,052 cases reviewed). However weekend or evening on-call deliveries showed no difference. Emergency Cesarean had a 7-fold higher risk of general anesthesia.

The evidence supports the use of training and staffing models for specialized obstetric anesthesiologists, as neuraxial anesthesia is in general the recommended choice. The authors discuss various possible confounding variables like provider or patient factors, institutional and team dynamics, although they attempted to adjust for some. Also there is no maternal or neonatal outcome data.

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Thromboelastometry: new ROTEMsigma

The new generation of ROTEM automates this point of care device for assessing coagulation, relative contributions of clotting factors, fibrinogen, platelets and fibrinolyis. The two technologies of ROTEM and TEG have been studied and early evidence suggests utility in trauma, obstetrics and perhaps in major blood-loss surgeries such as liver or cardiac.

This study found ROTEMsigma exhibited high precision and correlation with previous generation ROTEMdelta devices.

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A review of this point of care coagulation assessment is found here link