Regional 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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Aspirin for Thromboembolism Prophylaxis

“Aspirin alone may be an appropriate alternative to other pharmacologic prophylaxis in preventing VTE for patients undergoing total knee arthroplasty.”

So says this JAMA study but with the limitations of retrospective analysis and the subtleties of non-inferiority design. Nonetheless it adds to the debate and evidence on the use of aspirin alone as a potential strategy (which would also simplify neuraxial anesthesia concerns with anticoagulation).

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Anticoagulants and antiplateles in hip fracture surgery

Delay in hip fracture surgery can increase mortality (link ).

A Scottish Consensus statement on the management of patients on anticoagulants (and antiplatelet agents) presenting for hip fracture surgery incorporates current knowledge and views on when to proceed and how to expedite anticoagulant reversal with Vitamin K and/or Prothrombin Complex Concentrate, as well as antiplatelet agent considerations. Caution may also be needed with neuraxial techniques in such patients.

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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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Dural Sac Extent in Neonatal Caudal Block

An anatomic study in neonates sought to determine how close the dural sac was to the apex of the sacral hiatus, as this may lead to unintended spinal injection. Average distance in males was 10.9mm and 9.6mm in females; it increased with greater neonate length. Range was 4.9 -26.3mm.

“Anesthesiologists should be aware of the short distance between the sacral hiatus and the dural sac when performing caudal blocks, the shortest distance was 4.94 mm. Armed with this knowledge, caudal techniques should be modified to improve the safety and reduce the risk of complications, such as dural puncture.”

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