Sedation in hypoalbuminemic geriatric patients under spinal anesthesia in hip surgery

Methods

This study was approved by the ethical and research committee of Okmeydani Training and Research Hospital, and informed written consent was obtained from each subject. This prospective and randomized study was completed in the Department of Anesthesiology and Intensive Care, Okmeydani Training and Research Hospital, Istanbul, Turkey, between February 2013 and December 2014. Sixty hypoalbuminemic patients, undergoing elective hip surgery under spinal anesthesia, and in the geriatric age group with albumin levels below 3 g/dl were included in this study. The standard effect size of the study was determined as 0.83, with 80% power, and 5% error so the sample groups were calculated to require at least 26 individuals. According to calculations, the groups required at least 26 individuals, and taking into account losses during the study period, the decision was arrived at to include 30 individuals in each group. Before the operation, patients had routine systemic examinations completed, laboratory values were investigated, and patients joined the study groups. Patients with contraindications for spinal anesthesia (sepsis, bacteremia, regional skin infection, hypovolemia, coagulopathy, therapeutic anticoagulation, increased intracranial pressure, patient refusal of procedure), those with allergies to local anesthetics, and those with albumin levels above 3 g/dl were excluded from the study group. The patients were randomized using a closed envelope method into one of the 2 groups; midazolam (Dormicum,^® Roche, Istanbul, Turkey) (Group I: n=30), and propofol (Propofol 1%, Fresenius,^® Fresenius Kabi Medicine, Istanbul, Turkey) (Group II n=30). All methods were explained one day in advance and all cases provided written consent. They were not provided with solid food for at least 8 hours, and fluids for at least 4 hours before the operation. No case was given premedication. A vein was opened with a 20 G intravenous cannula, and before block prehydration was provided with 10 ml/kg 0.9% NaCl infusion for 30 minutes. The age, height, weight, and preoperative albumin values of the patients were noted. For monitoring, a Datex-Ohmeda S/5 Avance (General Electric Inc, Madison, WI, USA) monitor was used. Systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation values (SpO₂), respiration rate (RR), and Wilson’s 5-stage sedation scores (1 - fully awake and oriented; 2 - drowsy; 3 - eyes closed but arousable to command; 4 - eyes closed but arousable to mild physical stimulation, and 5 - eyes closed but unarousable to mild physical stimulation)11 were recorded at the following times: initial values; after regional anesthesia; after bolus; start of surgery; 15th minute after the start of surgery; after the final suture; and on exit from the operating room (OR). In addition, the hemodynamic and respiratory parameters were observed during the whole operation time. Spinal block administration was completed in sitting position after skin cleansing with povidone iodine by entering the intrathecal interval at the L3-4, or L4-5 level with a 22 G spinal needle. As all patients were more than 50 years old, and post puncture headache is observed mostly in younger patients, a 22 G spinal needle was used. Hyperbaric bupivacaine (Marcaine^®Spinal heavy, 0.5%, 4 mL ampule, AstraZeneca UK Ltd, Luton, Bedfordshire, UK) was administered into the spinal interval at the following rates; for cases 155-165 cm tall 12.5 mg; for cases 165-175 cm tall 13.5 mg; and for cases 175-190 cm tall 15 mg. After confirming the sensorial block had reached T 10 with a pin-prick test in the 10th minute, Group I was given 0.05 mg/kg bolus midazolam. Then infusion of midazolam was initiated with a dose of 0.02 mg/kg/hr, which was increased to a dose of 0.1 mg/kg/hr according to bispectral index (BIS) values. In Group II, 1 mg/kg bolus propofol was administered within 10 minutes. Then, 1 mg/kg/hr continuous infusion of propofol was started, and the dose was increased to 3 mg/kg/hr according to BIS values. To maintain BIS of 65-80%, infusion doses were raised or lowered by 50% in 5-minute intervals. A Braun McGaw infusion pump (Braun McGaw AG, Melsungen, Germany) was used for infusion. Sedation was continued until the first skin sutures in both groups. Perioperative side effects were assessed as hypotension, bradycardia, desaturation, and nausea-vomiting. The MAP falling below 70 mm Hg, or by more than 20% of the initial pressure was accepted as hypotension, HR falling below 50 beats/minute was bradycardia, and SpO₂ falling below 90%, or RR <10/minute was accepted as respiratory depression. To regulate hypotension, colloid and crystalloid replacement, and if necessary ephedrine hydrochloride (5-25 mg IV) were administered. For bradycardia, atropine sulfate (0.5-1 mg IV) was used. It was planned that in cases with respiratory depression observed who did not respond to tactile and verbal stimuli, controlled respiration with a mask should be started. In situations of nausea or vomiting, 10 mg IV metoclopramide was given. For both groups, 2 one/min O₂ was administered preoperatively and postoperatively through a mask. The recovery duration was accepted as the duration from the end of infusion to when the patient was fully awake, that is BIS >90, and Wilson’s 5-stage sedation score of 1. To assess the patient’s satisfaction with the anesthesia method used, in the 30th minute postoperatively while the effect of the spinal block continued, they were requested to use a 6 point scale (0 - very bad; 1 - bad; 2 - mild; 3 - good; 4 - very good; 5 - excellent). To assess surgeon’s satisfaction, the same scale was used. The patient and surgeon were blinded to the sedative drug used during this study by the anesthetists who assessed the outcomes.

Descriptive statistics of the data are given as mean, standard deviation, median, minimum, maximum, frequency, and percentage. The distribution of variables was measured with the Kolmogorov Smirnov test. Quantitative data were analyzed with the Mann-Whitney U test. Recurrent measurements were analyzed with the Wilcoxon test. For analysis of quantitative data, the chi square test was used, while the Fischer test was used when conditions for the chi-square test were not met. Statistical analysis was performed by Statistical Package for Social Sciences version 22 (IBM Corp, Armonk, NY, USA). Statistical significance was set at p<0.05.