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[Concentrations of sevoflurane with and without nitrous oxide to block vasomotor reflexes to incision (MACBVR)]

Toshiyuki Nakahara1, Satoshi Yasumoto, Yuka Jinnouchi

  • 1Department of Anesthesia, Tokushima Municipal Hospital, Tokushima 770-0812.

Masui. the Japanese Journal of Anesthesiology
|February 14, 2002
PubMed

Insights

Adding nitrous oxide (N2O) to sevoflurane anesthesia significantly lowers the minimum alveolar concentration of anesthetic that blocks the skin vasomotor reflex to surgical incision (MACBVR). This combination effectively suppresses adrenergic responses during surgery.

Area of Science:

  • Anesthesiology
  • Pharmacology
  • Surgical Medicine

Background:

  • Sevoflurane is a common inhalation anesthetic.
  • Understanding anesthetic requirements for surgical stimuli is crucial for patient safety.
  • Nitrous oxide is often used as an adjunct anesthetic agent.

Purpose of the Study:

  • To determine the minimum alveolar concentration of sevoflurane that blocks the skin vasomotor reflex to surgical incision (MACBVR).
  • To evaluate the effect of adding 50% nitrous oxide (N2O) to sevoflurane anesthesia on MACBVR.
  • To assess the impact of N2O on hemodynamic responses to surgical incision.

Main Methods:

  • A randomized controlled trial involving 37 patients undergoing laparotomy.
  • Patients were allocated to receive either sevoflurane alone or sevoflurane with 50% N2O.
  • Skin blood flow was measured using a laser Doppler flowmeter to determine MACBVR.
  • Hemodynamic variables including systolic blood pressure (SBP) and heart rate (HR) were monitored.

Main Results:

  • The MACBVR for sevoflurane in oxygen was 3.07%, decreasing to 1.63% with 50% N2O.
  • The MACBVR in terms of total anesthetic Multiple of the Acceptable Concentration (MAC) was 1.75 MAC for sevoflurane alone and 1.43 MAC with N2O.
  • Addition of N2O significantly suppressed changes in SBP and HR at the time of surgical incision (P < 0.01).

Conclusions:

  • Nitrous oxide significantly reduces the sevoflurane MACBVR.
  • N2O is effective in attenuating adrenergic responses to surgical stimuli during sevoflurane anesthesia.
  • The combination of sevoflurane and N2O may allow for lower sevoflurane concentrations while maintaining adequate surgical blockade.

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