Cardiovascular Effects of Intrathecal Hyperbaric Prilocaine or Bupivacaine in Surgery Under Spinal Anesthesia

Plain-language summary

Spinal anesthesia remains a mainstay in lower limbs- as in day-case surgeries as well. It consists in injecting a local anesthetic drug into the intrathecal space of a patient's spinal canal. To achieve a suitable sensory and motor block for elective or emergent surgery, the anesthetist must adapt his choice of local anesthetic to the surgery's requirements and the patient's comorbidities, too. Spinal anesthesia is often associated with adverse cardiovascular events, notably hypotension which is a major concern in current anesthetic practice, especially in specific patient populations. Spinal induced hypotension is reported to be commonly related to the sympathetic block level and may be linked to perioperative cardiac and renal complications. Several mechanisms might play a role in the incidence of perioperative hypotension after spinal puncture. A decrease in peripheric systemic vascular resistance from arterial vasodilatation, a reduction of cardiac output due to a decrease in preload from a redistribution of venous blood into lower limbs or even an occurrence or increment of cardiac dysfunction, might compound proper blood flow towards noble organs such as brain, heart and kidneys. Spinal induced hypotension may also be related to a direct reduction of cardiac contractibility by the local anesthetic injection. Compensating mechanisms might be inhibited depending on the level of sympathetic blockade, usually related to the dose of the local anesthetic. Former studies found that intrinsic left ventricular depression might occur during spinal anesthesia as left ventricular volumes per se remain stable. One noticed that diastolic and systolic function (i.e., ventricular outflow tract velocity) decreased significantly after intrathecal levobupivacaine plus fentanyl injection based on transthoracic ultrasound assessment. Other authors use Pro-Brain Natriuretic Peptide to assess myocardial stress induced by surgery and anesthetic management. Other serum markers such as Cortisol, Adreno Cortico-Trope Hormone, Angiotensin are identified to screen and monitor myocardial stress as for instance acute myocardial dysfunction. Hyperbaric prilocaine is an intermediate-acting local anesthetic, whereas bupivacaine may be intermediate- or long-acting depending on the employed dose. Both drugs provide comparable sensory and motor block that meet the anesthesia level requirements in various surgical procedures. In regard to the hemodynamic effects, hypotension has been largely reported following hyperbaric bupivacaine in a dose-dependent way. However, discrepancy exists between the rare studies having investigated prilocaine's effects, probably related to the methodology and the employed doses. Moreover, the hemodynamics effects of these local anesthetics have been barely specifically investigated in a non-cesarean section context. The aim of this study is to compare the cardiovascular effects inflicted by hyperbaric prilocaine and bupivacaine under spinal anesthesia. Cardiovascular response will be assessed by non-invasive hemodynamic monitoring whereas metabolic stress will be evaluated using serum stress markers.

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