Laryngoscopy and endotracheal intubation (LETI) during general anesthesia can elicit significant haemodynamic responses, potentially posing risks to patients with cardiovascular or cerebrovascular conditions. Ensuring adequate depth of anesthesia during these procedures is crucial for maintaining haemodynamic stability. Additionally, commonly used induction agents like Propofol may cause haemodynamic instability. This study aims to assess the effect of Bispectral Index (BIS) targeted induction on haemodynamic responses to LETI during general anesthesia to establish optimal depth of anesthesia and maintain haemodynamic stability.
This prospective comparative study included 110 patients aged 20 to 60, falling under ASA 1 and 2 categories, scheduled for elective surgeries with endotracheal intubation under general anesthesia. Informed consent was obtained from all participants. Patients were divided into two groups: Group 1 (55 patients) targeted a BIS value of 60, and Group 2 (55 patients) targeted a BIS value of 40. Both groups received a BIS-targeted Propofol infusion at 10mg/kg/hr until the desired BIS value was achieved. Haemodynamic parameters (HR, BP, SPO2, and BIS values) were recorded at baseline, upon attaining the targeted BIS value, before intubation, 1 minute, 3 minutes, and 6 minutes after intubation, and the haemodynamic response was assessed.
The study found that the haemodynamic response to LETI at BIS 60 was statistically significant compared to BIS 40 but remained clinically not significant as the variables remained within normal limits. At the deeper level of anesthesia (BIS 40), variations in HR, BP, and BIS values were less pronounced, but delayed cardiovascular depression, mainly persistent decrease in BP, was observed due to the increased requirement of Propofol to achieve a deeper plane of anesthesia. Group 1 (BIS 60) showed a significant change in BIS value immediately after intubation, which subsequently decreased close to the desired BIS range. Group 2 (BIS 40) did not show a significant change in BIS values after LETI. Most patients at BIS 40 became apnoeic and required assisted ventilation, but no episodes of desaturation were observed during the study.
The study concludes that a BIS value of 60 is an adequate depth for laryngoscopy and intubation compared to BIS 40. While haemodynamic variations were more pronounced at BIS 60, they remained clinically not significant. A deeper level of anesthesia achieved with a higher dose of Propofol led to more apnoeic episodes and delayed cardiovascular depression.