Effect of Head-Up Positioning on Bispectral Index and Recovery Profiles in Patients Undergoing Laparoscopic Hysterectomy: A Randomized Controlled Clinical Trial

Document Type : Research/Original Article

Authors

Clinical Research Development Unit, Mehrgan Hospital, Kerman University of Medical Sciences, Kerman, Iran

10.30476/acrr.2026.110576.1283

Abstract

Background: Patient positioning during laparoscopic surgery can affect respiratory, cardiovascular, and
cerebral physiology, thereby influencing processed electroencephalographic measures of anesthetic depth.
This study evaluated the effect of head-up positioning on intraoperative bispectral index (BIS) values and
perioperative recovery outcomes in patients undergoing laparoscopic hysterectomy.
Methods: In this randomized controlled clinical study, 105 adult patients undergoing elective laparoscopic
hysterectomy were randomly assigned to either standard positioning (control, n=47) or approximately 30°
head-up positioning (n=58). Anesthesia was induced with fentanyl, propofol, and atracurium and maintained
with isoflurane at 1.2 MAC. The primary outcome was the mean intraoperative BIS. Secondary outcomes
included measures of emergence, recovery, respiratory function, intra-abdominal pressure, sedation, and
pain. Continuous variables were analyzed using independent-samples t-tests or Mann–Whitney U tests, as
appropriate. ANCOVA was used to assess between-group differences in mean BIS after adjusting for age.
Results: The mean intraoperative BIS was significantly lower in the head-up group compared to the control
group (45.46±6.27 vs. 50.18±4.55; P<0.001). This difference remained significant after adjusting for age
(F(1,101)=17.574, P<0.001; partial η²=0.148), with an adjusted between-group difference of −4.556 BIS units.
The time to reach a BIS of 80 was shorter with head-up positioning (13.2±2.8 vs. 15.4±3.2 minutes; P=0.028).
The duration of anesthesia was longer in the head-up group (67 vs. 55 minutes; P=0.017), whereas surgery
duration was similar between groups (P=0.729). Extubation time, PACU stay, postoperative pain, ETCO₂,
mean airway pressure, and intra-abdominal pressure did not differ significantly between groups. RASS scores
differed significantly (P=0.036).
Conclusion: Head-up positioning was associated with lower intraoperative BIS values during laparoscopic
hysterectomy. However, without direct assessment of cerebral perfusion or oxygenation, these findings cannot
conclusively indicate a greater depth of pharmacological hypnosis. Therefore, changes in BIS following
positional interventions should be interpreted with caution.

Highlights

Mohammad Yousofi (Google Scholar)

Fatemeh Ahmadi (Google Scholar)

Keywords

References

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