2. Methods
bradycardia, hypothermia, fever, hypertension, blood loss, ±, infection, hypotension, shivering, Hypotension
GROUP B, PRIMARY POSTPARTUM HEMORRHAGE, BLOOD LOSS, ADVERSE EVENT, INFECTION, SECONDARY, HYPERTENSION, PLUMMER
Ethical approval for this study was provided by the Medical Research and Ethics Committee, Universiti Kebangsaan Malaysia Medical Centre, on 30In total, 118 patients were recruited for this study. Inclusion criteria included patients aged 18 to 40 years old, American Society of Anesthesiologists physical status score II, and singleton pregnancy who were scheduled to undergo elective lower segment cesarean section under spinal anesthesia. Exclusion criteria included contraindications to phenylephrine, evidence of fever or infection, hypothermia (<35 °C) preoperatively, body mass index > 40 kg/mUsing a computer-generated table, patients were randomly assigned to 1 of 2 groups, Phenylephrine (Group A) or Control (Group B) with a 1:1 allocation. Patient identifiers were attached to the opened envelopes and secured by a dedicated person, independent of the randomization procedure.All patients fasted for at least 6 hours prior to surgery. They were given gastric acid aspiration prophylaxis prior to the surgery, which consisted of 150 mg oral ranitidine on the night prior to surgery and on the morning of surgery, and 30 mL of 0.3M sodium citrate oral solution on the morning of surgery. Patients and the attending anesthesiologist were blinded to the group to which the patients were allocated. Both phenylephrine (SAMARTH Frenin injection, India) and normal saline were prepared in 20 mL syringes by the investigator, and phenylephrine was diluted to a concentration of 100 mcg/mL. Patients in Phenylephrine Group (Group A) received phenylephrine infusion at rate of 0.5 mcg/kg/minute, which was equivalent to 0.3 mL/kg/hour, whereas Control group (Group B) patients received a saline infusion at a same rate of 0.3 mL/kg/hour. The syringes were labeled based on the same computer-generated randomized numbers, so that the attending anesthesiologist and patient did not know the content of the syringes.Before induction of anesthesia, standard monitors, such as noninvasive systolic and diastolic blood pressure monitoring, continuous electrocardiography, and pulse oximetry, were applied to the patient. Baseline blood pressure, heart rate, oxygen saturation, and core body temperature were measured prior to induction. The ambient temperature of the operating theater was recorded, as measured by a standardized wall thermometer. The baseline core temperature of the patient was measured at the tympanic membrane using an infrared thermometer (Novo Temp TH50Z). Core temperature was measured every 15 minutes intraoperatively. All vital signs were recorded by an attending anesthesiologist who was blinded to the study.A separate intravenous cannula was inserted to administer the study drugs. Co-loading with 500 mL of Hartmann’s solution was initiated in all patients prior to the commencement of spinal anesthesia. The patient was placed in a sitting position for spinal anesthesia. Spinal block was performed at the L3/L4 or L4/L5 levels using a 27-gauge spinal needle by the attending anesthesiologist under aseptic technique. Upon free flow of cerebrospinal fluid, 2 mL of 0.5% hyperbaric bupivacaine mixed with 0.1 mg morphine and fentanyl (15 µg) was administered to the spinal block. The time the spinal block was administered was recorded as “tThe primary outcome of the study was the incidence of shivering and changes in the patient’s core temperature, while the secondary outcomes were changes in hemodynamic parameters such as systolic and diastolic blood pressure and heart rate. All outcomes were assessed by the attending anesthesiologist both intraoperatively (from induction until completion of skin closure) and postoperatively in the recovery room.The intensity of shivering was recorded by the attending anesthesiologist immediately after the spinal block and every 15 minutes during the surgery using the Bedside Shivering Assessment Scale.Adverse events, such as hypotension, hypertension, and bradycardia, were recorded and managed accordingly. Hypotension (defined as systolic blood pressure < 80% of the baseline) was treated with bolus doses of intravenous ephedrine (6 mg titrated to effect). Intravenous ephedrine were the first choice of rescue drugs to avoid bias. If the blood pressure remained low, an intravenous phenylephrine 100 µg bolus was administered, up to a maximum of 300 mcg. If hypertension (defined as systolic blood pressure > 120% of the baseline) occurred, the study drug infusion was terminated. If bradycardia (defined as a heart rate < 40 beats per minute) occurred, the study drug infusion was terminated, and intravenous atropine (0.5 mg) was administered if it was accompanied by hypotension. The dose and time of administration of all the rescue drugs were recorded. Patients were excluded from the study if they received more than 300 µg of phenylephrine bolus, conversion to general anesthesia, primary postpartum hemorrhage with blood loss more than 700 mL, surgical time exceeded 120 minutes, or if the drug infusion was terminated earlier during the surgery.Drug infusion was terminated at the end of skin closure. Surgical time was defined as the time from the start of the surgical incision to completion of skin closure. The patient was transferred to the recovery room after surgery, and a warming blanket covering the entire body was applied. The ambient temperature of the recovery room was recorded. The patient’s core temperature, blood pressure, and heart rate were monitored every 15 minutes until the patient was discharged from the recovery room.The sample size was estimated using the PS Power and Sample Size Calculations program by Dupont and Plummer (2009), based on the incidence of shivering among patients who received phenylephrine (Hilton et alAll data were analyzed using SPSS version 22.0 (IBM Corp, Armonk, NY). Results are presented as mean ± standard deviation, median with interquartile range, or frequency (percentages), where appropriate. An independent 