Effects of pre-injection of pressors on pressor response and bispectral index of patients receiving lower abdominal surgery under total intravenous anesthesia

Abstract

Surgery in the lower abdomen can cause many adverse reactions in nervous system, metabolic and endocrine systems. Conventional intravenous anesthesia applied for lower abdominal surgery can cause the drop in blood pressure leading to hypoperfusion of vital organs. Hence, an ideal anesthesia state is required to make patients unconscious, unaware and have no postoperative memory during anesthesia. In this study, we investigated the effects of pre-injection of different pressors on the pressor response and bispectral index (BIS) of patients receiving lower abdominal surgery under total intravenous anesthesia. For this, 300 patients undergoing lower abdominal surgery under total intravenous anesthesia were divided into normal saline (Gr. A), ephedrine (Gr. B) and phenylephrine groups (Gr. C) (n=100). Hemodynamics indices were recorded before anesthesia induction (T0) and 1, 3, 5, 7 and 9 min after drug injection (T1-T5, respectively). We observed the following reactions and recorded. BIS values at T0-T5 as well as the time points when the values rose to 65, 75, 85 and 95 and those for respiratory recovery, consciousness recovery and extubation after stopping target-controlled infusion were recorded. Compared with Gr. A, Gr. B had significantly higher systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and cardiac output (CO) at T1-T5 (P <0.05), and Gr. C had higher SBP, DBP, MAP and lower HR (P <0.05). Adverse reactions viz., intraoperative hypotension, hypertension, postoperative bradycardia, tachycardia, nausea and vomiting were also observed. The incidence rates of hypotension and total adverse reactions in groups B and C were significantly lower than those of Gr. A (P <0.05). Group B had significantly higher BIS values at T1-T5 than those of Gr. A (P <0.05). The time when BIS values recovered to 65 and 75 in group B was significantly shorter than that of Gr. A (P <0.05). Pre-injection of ephedrine and phenylephrine to patients undergoing lower abdominal surgery under total intravenous anesthesia elevated the blood pressure and reduced the incidence rate of adverse reactions without affecting the recovery time.