Transfer function analysis of the circulation in patients undergoing sevoflurane anesthesia

Area of Science:

• Anesthesiology
• Cardiovascular Physiology
• Respiratory Physiology

Background:

• Understanding cardiorespiratory interactions is crucial for safe anesthesia.
• Sevoflurane is a widely used inhalational anesthetic agent.
• The impact of sevoflurane on autonomic regulation of heart rate, blood pressure, and respiration requires further elucidation.

Purpose of the Study:

• To assess the effects of sevoflurane anesthesia on the interactions between heart rate, blood pressure, and respiration.
• To quantify these interactions using transfer function analysis.

Main Methods:

• Nine patients (ASA 1 or 2) undergoing elective surgery were studied.
• Measurements included instantaneous heart rate (IHR), instantaneous lung volume (ILV), and mean blood pressure (MBP) during conscious state, 1 MAC, and 2 MAC sevoflurane anesthesia.
• Transfer function analysis was performed on five-minute recordings with standardized respiratory rate variations.

Main Results:

• Sevoflurane significantly decreased transfer magnitudes between ILV and IHR, and between MBP and IHR.
• No significant changes were observed in transfer magnitudes or phases between ILV and MBP.
• Coherence decreased at 1 MAC sevoflurane for ILV-IHR and MBP-IHR relationships, but not at 2 MAC.

Conclusions:

• Sevoflurane anesthesia alters cardiorespiratory interactions, particularly affecting the relationship between respiratory and heart rate/blood pressure.
• These alterations may be attributed to the attenuation of autonomic nervous system activity by sevoflurane.