Obstetric Anesthesia

Obstetric Epidural and Body Temperature

Epidural anesthesia is conventionally thought of as causing heat loss due to lower limb vasodilation from sympathetic blockade. This may be the case also in elective Cesarean epidurals.

Heat production is increased by both labor and epidurals. In this study in emergency Cesarean Section, after labor epidural top-up there was a progressive rise in temperature and after considering many mechanisms of heat production and hemodynamic mechanisms, the most likely explanation is limitation of cutaneous heat loss via blockade of active cutaneous vasodilation. (Cutaneous vasomotor tone is regulated both by the noradrenergic ‘active vasoconstriction’ pathway and the cholinergic ‘active vasodilation’ pathway).

“It is likely that heat loss limitation was responsible for the rise in mean body temperature before and after epidural top‐up, with heat production and heat loss becoming uncoupled”. Despite this, and not conflicting with this theory, cutaneous blood flow did not increase.

The authors caution that this study specifically dealt with epidural labor analgesia conversion to anesthesia via top-up for emergency Cesarean without major blood loss. However the use of active warming in this population could be questioned, much as prevention of hypothermia has become standard.

The subject is non-trivial as we are reminded: “Epidural hyperthermia (or fever) is a harmful condition which is associated with adverse neonatal neurological outcomes, an increased risk of operative delivery, and an increased risk of maternal and neonatal sepsis evaluation and treatment. Its underlying mechanism remains unclear. An association has been demonstrated with maternal inflammation, but no causal link has been uncovered”

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Post-Dural Puncture Headache

A small study based on chart reviews limits the findings of this study which should be tested in future controlled studies. Nonetheless an interesting approach to postdural puncture headache was performed in the form of a topical sphenopalatine ganglion block and compared to the standard epidural blood patch. This ganglion block is being tested for migraine and other headaches but remains investigational.  (These topical blocks are usually described as simply placing local anesthetic soaked swabs along the floor of the nose until reaching and stopping at the nasopharynx and left there for 10mins or so, more recently with syringes attached to nasal catheter).

These authors found a faster headache resolution at 30 and 60 minutes with sphenopalatine block.

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Cervical Cancer Survival and Minimally Invasive Surgery

Minimally invasive surgery has been promoted as part of enhanced recovery after surgery protocols (ERAS) but a rather surprising finding in early cervical cancer finds that minimally invasive radical hysterectomy was  associated with lower rates of disease-free survival and overall survival than open abdominal radical hysterectomy among women with early-stage cervical cancer.

Confounding, surgical, operator experience factors are among possibilities but further studies are required to explain these findings.

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Cesarean Prophylactic Phenylephrine

It has become common practice to start Phenylephrine infusions after spinal anesthesia for Cesarean to prevent hypotension and accompanying nausea. (Norepinephrine has more recently entered into this area [ link ] ). This study suggests possible unintended consequences in that the Bupivacaine dose for effective spinal anesthesia may be increased by prophylactic Phenylephrine infusion. The ED95 of intrathecal hyperbaric bupivacaine was 14.1 mg (95% CI, 12.3–37.6 mg) with prophylactic phenylephrine infusion and 11.7 mg (95% CI, 9.9–22.8 mg) in the control group.

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Inter-professional Labor Epidural Attitudes

This survey finds differences between nurses, anesthesiologists and obstetricians. Timing of an epidural was influenced by patient desire for an epidural, primigravid patients without membrane rupture, oxytocin infusion initiated, labor epidural in a previous pregnancy, and a difficult airway.

“Different provider groups vary in comfort when managing labor epidural analgesia.

Willingness to advocate for epidural placement may depend on the cervical dilation.

Providers consider patient-specific factors when determining suitability”.

The authors posit that opportunity exists for inter-professional education and collaboration.

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OSA Screening in Pregnant Obese

Pregnant patients 24-35 weeks with BMI > 40 were given Obstructive Sleep Apnea (OSA) screening questionnaires (Berlin, American Society of Anesthesiologists checklist, and STOP-BANG), and the Epworth sleepiness scale. They underwent overnight sleep apnea testing; 24% had OSA.

“Established OSA screening tools performed very poorly to screen for OSA in this cohort. Age, BMI, neck circumference, frequent witnessed apneas and highly likely to fall asleep while driving were most strongly associated with OSA status in this cohort.”

OSA screening tools may need to be refined in this population.

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