The study protocol was approved by the institute ethics committee (FMASU R 46/ 2018) before enrollment of patients and a written informed consent was obtained by every patient. This randomized, prospective, double blind, study, adheres to CONSORT guidelines and was conducted at Ain-Shams university hospitals from the 1st of March 2018 till the 31st of August 2018 on 110 ASA I, II, III patients aged 60 years or more and scheduled for lower limb orthopedic surgeries under SA Patients with contraindication to SA (e.g. coagulopathy, thrombocytopenia, allergy to local anesthetic agent) and those on steroids or serotonin related medications (e.g. selective serotonin reuptake inhibitor) were excluded.
Randomization of the patients was performed using a computer-generated random numbers concealed in sealed opaque envelopes and a nurse randomly chose the envelope that determined the group of assignment. Patients were allocated into two equal groups (55 each) with 1:1 ratio according to post spinal hypotension prophylaxis; patients received either DEX 8 mg diluted in 100 ml 0.9% normal saline (NS) IVI over 15 min (D group) or an equal volume of plain NS (Control group) (C group) 2 h preoperatively. Study medications were prepared by the hospital pharmacy and given by anesthetists not involved in any other part of the study. Patients fasted 8 hours and were not intravenously hydrated before the procedure.
On arrival in the operating room, routine monitoring was applied, a venous access was established with a wide-bored cannula and patients were sedated by 1mg of midazolam IV. Infusion of NS solution was commenced not to exceed 400 mL during SA and for 20 minutes thereafter. SA was performed by injecting 3 ml of 0.5% hyperbaric bupivacaine solution (Marcaine® Spinal Heavy 0.5%; Sunny pivacaine, Manufactured by Sunny Pharmaceutical - Cairo - Egypt) at L3-L4 or L4-L5 level using 25gauge Quincke spinal needle.
After completing the subarachnoid injection, patients were positioned supine. Sensory level (by alcohol swab) and motor block (Modified Bromage Score (16)) was assessed every 5 minutes. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP) were recorded before giving the study medications (base line) and then during SA every 5 minutes for 4 readings.
Hypotension was considered if there was 25% decrease below the baseline for MAP and was managed by 300 ml of NS solution with incremental intravenous 5 mg doses of ephedrine. Bradycardia was considered if the heart rate was less than 50 beats/min and was treated with atropine (0.01mg/kg) IV, only data before giving ephedrine and/or atropine were analyzed if they were given. The anesthetists who performed the spinal anesthesia and recorded the hemodynamic changes were unaware of the medications given to patients preoperatively.
The proportion of patients with hypotension at any time during the first 20 min after induction of the SA and before starting the surgical procedure was set as the primary outcome.
The research team considered all 4 measurements of each of 3 blood pressures (SBP, DBP&MAP) as secondary outcomes. The obtained blood pressures values at each study time point were compared to the minimal values recorded within the 20 minutes following the subarachnoid blockade. Surgical procedure, positioning of the patient or application of tourniquet was not allowed during the study period. The pattern of sensory and motor blocks, number of patients who needed atropine and/or ephedrine, Changes in HR among groups and associated side effects (e.g., nausea, vomiting and shivering) were considered as secondary outcomes.
Statistical analysis
Depending on Baig et al.,2017 (17) who found that the hypotension rate in ondansetron and normal saline groups were 7.5% and 28.3% respectively and assuming that the power= 0.80 and α=0.05 and by using PASS 11th release, the minimal sample size for an equal size controlled clinical trial was 50 in each group. We recruited 55 in each group for possible attrition (18).
The collected data were coded, tabulated, and statistically analyzed using IBM SPSS statistics (Statistical Package for Social Sciences) software version 18.0, IBM Corp., Chicago, USA, 2009.
Descriptive statistics were done for quantitative data as minimum& maximum of the range as well as mean (SD) (standard deviation) for quantitative normally distributed data, while it was done for qualitative data as number and percentage.
Inferential analyses were done for quantitative variables using Shapiro-Wilk test for normality testing, independent t-test in cases of two independent groups and paired t-test in cases of paired data. In qualitative data, inferential analyses for independent variables were done using Chi square test for differences between proportions and Fisher’s Exact test for variables with small expected numbers. The level of significance was taken at P value < 0.050 is significant, otherwise is non-significant.