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Autoregulation of human inner ear blood flow during middle ear surgery with propofol or isoflurane anesthesia during
M P Preckel1, C Ferber-Viart, G Leftheriotis
1Service d'Anesthésie Réanimation, Centre Hospitalier Universitaire, Angers, France. Marie-Pierre.Preckel@univ-angers.fr
Unlabelled:
We used controlled hypotension to obtain a bloodless cavity during middle ear surgery under an optical microscope. No previous study has assessed the effect of controlled hypotension on inner ear blood flow (IEF) autoregulation in humans receiving propofol or isoflurane anesthesia. In the present study, the IEF autoregulation was determined using laser Doppler flowmetry in combination with transient evoked otoacoustic emissions (TEOAEs) during controlled hypotension with sodium nitroprusside in 20 patients randomly anesthetized with propofol or isoflurane. A coefficient of IEF autoregulation (Ga) was determined during controlled hypotension, with a Ga value ranging between 0 (no autoregulation) and 1 (perfect autoregulation). During controlled hypotension with propofol, IEF remained stable (1%+/-6%; P > 0.05) but decreased by 25%+/-8% with isoflurane (P < 0.05). The Ga was higher during propofol anesthesia (0.62+/-0.03) than during isoflurane anesthesia (0.22+/-0.03; P < 0.0001). Under propofol anesthesia, there were individual relationships between TEOAE amplitude and change in IEF in four patients. Such a correlation was not observed under isoflurane anesthesia. These results suggest that human IEF is autoregulated in response to decreased systemic pressure. Furthermore, isoflurane has a greater propensity to decrease cochlear autoregulation and function than propofol.
Implications:
The present study shows that inner ear blood flow is autoregulated under propofol, but not isoflurane, anesthesia during controlled hypotension in humans during middle ear surgery. Further studies are needed to explore the postoperative auditory functional consequences of the choice of the anesthetic drug used in middle ear surgery.
Insights
Propofol anesthesia maintained stable inner ear blood flow (IEF) during controlled hypotension in middle ear surgery, unlike isoflurane. This suggests propofol better preserves cochlear autoregulation and function under reduced blood pressure.
Area of Science:
- Otolaryngology
- Anesthesiology
- Physiology
Background:
- Controlled hypotension is used in middle ear surgery to create a bloodless field.
- The impact of propofol versus isoflurane anesthesia on inner ear blood flow (IEF) autoregulation during hypotension is not well-established in humans.
Purpose of the Study:
- To assess the effect of propofol and isoflurane anesthesia on IEF autoregulation during controlled hypotension in patients undergoing middle ear surgery.
Main Methods:
- Laser Doppler flowmetry and transient evoked otoacoustic emissions (TEOAEs) were used to measure IEF autoregulation (Ga) in 20 patients.
- Patients received either propofol or isoflurane anesthesia during induced controlled hypotension with sodium nitroprusside.
Main Results:
- Under propofol, IEF remained stable (1%+/-6%), while isoflurane caused a significant decrease (25%+/-8%).
- The coefficient of IEF autoregulation (Ga) was significantly higher with propofol (0.62+/-0.03) compared to isoflurane (0.22+/-0.03).
- A correlation between TEOAE amplitude and IEF changes was observed with propofol but not isoflurane.
Conclusions:
- Human IEF is autoregulated during controlled hypotension under propofol anesthesia.
- Isoflurane anesthesia impairs cochlear autoregulation and function more than propofol during middle ear surgery.
- Further research is needed to evaluate the long-term auditory outcomes based on anesthetic choice.