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Effects of propofol and inhalational anesthetics on the optic nerve sheath diameter in patients undergoing surgery in the steep Trendelenburg position: a systematic review and meta-analysis.

BACKGROUND
Optic nerve sheath diameter (ONSD) is recognized as a surrogate indicator of intracranial pressure (ICP) during surgery. Due to the requirements of surgery, the adjustment to the steep Trendelenburg position and the establishment of CO2 pneumoperitoneum can lead to an increase in ICP, resulting in an increase in the ONSD. Anesthetic agents have different impacts on cerebral blood volume and ICP. The aim of this study was to evaluate the effects of propofol and inhalational anesthetics on the ONSD based on data from randomized controlled trials (RCTs).


METHODS
The electronic databases of PubMed, EMBASE, Ovid MEDLINE, the Cochrane Library, and other databases were searched systematically using specified keywords from their inception to June 2021. The Chi-square test and I2 test were used to evaluate the heterogeneity across the studies. The weighted mean difference (WMD) with 95% confidence interval (CI) were adopted to analyze continuous data.


RESULTS
A total of 379 patients from 7 studies were involved in this meta-analysis. There were borderline significant differences in the ONSD atT2 between propofol and the control group: T2 (WMD =-0.15, 95% CI: -0.31, -0.00, P=0.005). There were significant differences at T3 (WMD =-0.23,95% CI: -0.42, -0.05, P =0.013) and T4 (WMD  =-0.18, 95% CI: -0.29, -0.07, P =0 .001). After statistical verification, there was no significant difference in the ONSD at T1 between the 2 groups: T1 (WMD =-0.08, 95% CI: -0.26, 0.10, P =0 .368). There were also no significant differences in mean arterial pressure (MAP) (P=0.654, 0.445, 0.698, and 0.562, respectively) and end tidal CO2 (ETCO2) (P=0.081, 0.506, 0.126, and 0.983, respectively) at T1, T2, T3 and T4 between propofol and inhalational anesthetics.


DISCUSSION
The findings in the present study indicated that the ONSD during propofol anesthesia was significantly lower than that during inhalational anesthesia after adopting the Trendelenburg position and CO2 pneumoperitoneum. These analysis results suggest that propofol anesthesia may help to minimize changes in ICP compared to inhalational anesthetics.