Comparison of the Effects of Fluid Preload (Crystalloid versus Colloid) Which Is Performed for Prevention of Spinal Anesthesia-induced Hypotension on Time to Reach Peak Sensory Block Level and Cerebrospinal Fluid Movement in Patients Scheduled to Undergo an Elective Transurethral Resection of a Bladder Tumor under Isobaric Spinal Anesthesia

Clinical study for isobaric spinal anesthesia: Sixty-three patients (American Society of Anesthesiology (ASA) physical status I and II; aged 70 yr or younger; males and females) scheduled to undergo an elective transurethral resection of a bladder tumor under spinal anesthesia were enrolled in this study. The patients were allocated randomly into one of two groups using a stratified sealed envelope method; lactated Ringer's solution (crystalloid) group or electrolytes-containing hextend (colloid) group. Upon arrival at the waiting area of the operating room approximately 20 minutes prior to initiation of spinal anesthesia, an anesthesiologist who participated in neither isobaric spinal anesthesia nor in determining the sensory block level, intravenously administered either 15 mL/kg of lactated Ringer’s solution or 5 mL/kg of electrolytes-containing hextend (Hospira, Inc., Lake Forest, IL, USA) to the patients over a 10 to 15 min period and then removed the solution from the patient' intravenous route for group-blindness. Subsequently, the patients were transferred to the operating room. Routine monitoring by electrocardiogram (ECG), non-invasive arterial blood pressure, and pulse oximetry were performed and the baseline measurements were recorded. Another group-blinded anesthesiologist performed the spinal anesthesia with the patient in the right lateral decubitus position. In all patients, a midline approach was used at the mid-lumbar level (Tuffier’s line) with a 25-gauge Whitacre spinal needle (BD Whitacre needle, BD Medical System, NJ, USA). A 0.5% isobaric tetracaine solution was prepared by dissolving 20 mg of crystalline tetracaine hydrochloride (Pantocainesterile, Daehan Med Co, Seoul, Korea) into 4 ml of the cerebrospinal fluid (CSF) withdrawn through a Whitacre spinal needle. Tetracaine 12mg (2.4 mL of the dissolved solution) was administered slowly into the intrathecal space over a 30 s period. The patient was placed in the horizontal supine position for 5 min and then in the lithotomy position. The sensory block levels were determined by a midline pinprick at 5 min intervals for the first 30 min and then at 15 min intervals until 90 min after the intrathecal injection of 0.5% isobaric tetracaine. Routine monitoring was recorded every 5 minutes. Ephedrine 5 mg was injected if hypotension (defined as a > 30% decrease in the mean arterial blood pressure from baseline measurement) occurred, and 0.5 mg of atropine was injected in the case of bradycardia (heart rate < 50/min). Volunteer study for Magnetic resonance (MR) imaging; Twenty-three healthy male volunteers (age range, 21-26 years), who were free from neurological disease and spinal deformity with no history of medication, were enrolled in this study. All quantitative assessments of the CSF movement by cardiac gated, phase-contrast cine high resolution MR imaging were performed between 6:00 PM and 8:00 PM because the rate of CSF production in healthy adults is affected by the circadian rhythm. Each volunteer underwent two sequential MR imaging studies at 1 week intervals. The first MR imaging study involved intravenous administration of lactated Ringer's solution. The initial MR images were taken for the baseline MR images obtained from volunteer at baseline. Subsequently 15 mL/kg of lactated Ringer’s solution was intravenously administered over a 10 to 15 min period and MR images were taken 30 and 60 min after the baseline MR images had been taken. One week after the crystalloid study, the same volunteers underwent a colloid study receiving 5 mL/kg of electrolytes-containing hetastarch (Hextend, Hospira, Inc., Lake Forest, IL) intravenously over 10 to 15 minutes. The MR imagings were obtained at the baseline, at 30 and 60 min later.