Obstetric Anesthesia

Dural puncture epidural versus conventional epidural block

Dural Puncture Block has become an increasingly discussed technique in labor and delivery analgesia, whereby no spinal medication is given but the dural hole is thought to enhance spread and speed of onset.

This review found “a lack of clear evidence on either the benefits or the risks of the DPE technique, such that a recommendation for or against its routine use is premature. Two of the three studies showing a beneficial effect of DPE came from the same institution and replication of the findings by other groups is warranted.”

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Malignant Hyperthermia in Pregnancy

A European group issues guidelines for MH in Pregnancy. As always, neuraxial anesthesia is preferred, and guidelines are otherwise similar to the non-obstetric population.

Of note:

  1. The mother is known or suspected to be MH-susceptible (in this case even the fetus may be MH-susceptible)
  2. The fetus may be MH-susceptible but not the mother (because the father of the child is known or suspected to be MH-susceptible).

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Post Dural Puncture Headache Treatment

A new guideline from the Obstetric Anaesthetists Association underlines how little evidence is really available to guide management of post dural puncture headache. Epidural Blood Patch remains the best treatment but in general is more effective after 48 hours. Some relief occurs in up to 80%, and complete resolution of pain in about a third. It may need repeating. 20mL blood is suggested or less if back pain develops.

There is insufficient evidence on a whole host of suggested treatments – steroids, gabapentinoids, ACTH, caffeine, triptans, theophylline, neostigmine and atropine, acupuncture, various nerve blocks, and epidural crystalloid.

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Neuraxial Anesthesia-Delivery time interval

Traditionally one of the more critically identified time frames after spinal anesthesia for Cesarean is the uterine incision to delivery time, and this is confirmed in this study.

After neuraxial anesthesia, uterine hypoperfusion from hypotension and maternal obesity may compromise the fetus. This study shows a direct correlation between increasing delay before delivery and decreasing umbilical artery pH.

“Efforts to minimize predelivery time following spinal placement could reduce the frequency of unanticipated neonatal acidemia.”

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Phenylephrine vs. Norepinephrine in Cesarean

A growing interest in the use of small bolus Norepinephrine (Noradrenaline) for Cesarean hypotension is based on its presumed lesser tendency to cause bradycardia compared to Phenylephrine.

This small study compared the effects of 100 μg phenylephrine and 5 μg norepinephrine and found no difference in maternal bradycardia. The number of boluses needed was higher in the Phenylephrine group.

“However, in view of the lower umbilical artery pH when using noradrenaline, further research is warranted to study its placental transfer and fetal metabolic effects”.

Hyperoxygenation in Pregnancy

Maternal hyperoxygenation has been used in different scenarios in pregnancy, eg. for fetal congenital heart disease.

This study on third trimester pregnant patients used non-invasive cardiac output monitoring to assess the effects of such hyperoxygenation. They found it is associated with a fall in maternal cardiac index and a rise in systemic vascular resistance without recovery to baseline levels at 10 minutes after cessation of hyperoxygenation. No change in blood pressure occurred, but heart rate decreased.

These hemodynamic changes could counteract any intended increase in oxygen delivery, and the authors call for further re-evaluation of the practice.

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Substance use disorders in pregnancy

The results of a joint workshop provide guidance on all aspects of substance use in pregnancy. Issues discussed in the full free text include screening tests, biologic tests, management of pain in labor and after Cesarean, pain after discharge, and approaches to medication assisted therapy (Methadone and Buprenorphine are standards of care), and organizational issues to optimize care. Discussion around breast feeding and the common neonatal opioid withdrawal syndrome (NOWS) occurs.

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ROTEM®‐guided algorithm in treatment of coagulopathy in obstetric haemorrhage

Point of Care coagulation assessments like ROTEM and TEG have been available for many years but data on outcome has been slower to emerge.

Hemorrhage management using traditional PT and PTT is a blunt instrument and has a slow laboratory turnaround time. Obstetric hemorrhage is different to trauma.

This is an obstetric hemorrhage report on 4 years of observational data from a tertiary care center using an algorithm based on FibTEM A5 assessment of hypofibrinogenemia. It resulted in a reduction in the number of units transfused and volume given, with less circulatory overload.

The authors note that coagulopathy is not observed in all women who suffer obstetric haemorrhage and cannot be predicted solely by blood loss, and also that women with placental abruption exhibited more severe coagulopathy and required higher doses of fibrinogen concentrate than women who bled due to other causes.

The results encourage point of care rather than formulaic blood product use to individualize cosgulopathy treatment.

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Norepinephrine vs. Phenylephrine in Cesarean

Norepinephrine has recently been increasingly studied for prophylaxis against hypotension during Cesarean Section under spinal anesthesia.

Phenylephrine has been shown to ameliorate hypotension and nausea/vomiting when given as a prophylactic infusion following spinal anesthesia.

This study compared the two agents and found Norepinephrine infusion effective and associated with less reactive hypertension and bradycardia. Neonatal outcomes were the same.

Norepinephrine rates were started at 0.05 mcg/Kg/min and Phenylephrine at 0.75 mcg/Kg/min.

This adds to growing evidence for Norepinephrine as an option in this scenario.

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Programmed Intermittent Epidural Bolus

Programmed intermittent epidural bolus (PIEB) has been touted as more effective than continuous or patient controlled epidural analgesia in labor. Studies are limited in this new area, often due to lack of pumps capable of delivering PIEB.

Under the conditions of this study, improved outcomes with programmed intermittent epidural boluses compared to continuous epidural infusion were not found, except for less motor block with programmed intermittent epidural boluses.

“Future studies should assess whether smaller but clinically important differences exist and evaluate different parameters of programmed intermittent epidural boluses to optimize analgesia and outcomes with this mode of analgesia”.

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