Intravenous Dexmedetomidine Infusion In Adult Patients Undergoing Open Nephrolithotomy

Patients and Methods: After approval of the ethical committee in Beni suef University (FMBUS REC,Egypt) the study was registered at ANZCTR clinical trial registry ,(registration number ACTRN12614000389606),a written informed consents were obtained from 50 patients ASA I and II males and females aged 20-60 years old, scheduled for elective open nephrolithotomy under general anesthesia from March 2014 to September 2014. Patients were excluded if they were ASA more than II , had a known cardiac arrhythmias, significant liver disease defined as (serum alanine aminotransferase and serum aspartate aminotransferase >2.5 times normal),significant renal disease defined as (serum creatinine>1.5 mg/dl or creatinine clearance <40 ml/min),pregnant patient, significant coagulopathy defined as (INR >1.5),use of antiplatlets or anticoagulants, anemic patients with Hb% less than 10 gm/dl. In the operating room, two intravenous cannula was inserted , monitors were connected including Electrocardiogram, pulse oximetry, non-invasive arterial blood pressure at 5 minutes intervals and BIS monitor strip (BIS Sensor; Aspect Medical Systems, USA, Toll free 1-888-BIS Index) The study drugs were prepared by a senior anesthesia resident unaware of the study protocol Patients were randomly allocated using a closed envelop technique into two groups (n= 25 each). Group D: received in a separate cannula a bolus dose of dexmedetomidine (Precedex, Abbot Laboratories Inc., Abbot Park, IL, USA) 1 micogram/kg over 10 min before induction of anesthesia then iv infusion of 0.1 -0.5 micogram/kg/h guided by the hemodynamics. Group P: received a bolus dose of 10 ml ringer lactate solution before induction of anesthesia then continuous infusion till the end of the operation. Preoxgenation for 3- 5 minute with 100% oxygen by facemask, then induction of anesthesia in all patients was with the use of i.v. fentanyl 2 micogram / kg, propofol 2 mg/ kg, , atracurium (0.5mg/kg) and ventilated manually with sevoflorane 2 volume % ,oxygen 100% via a face mask then oral cuffed endotracheal tube was inserted when the BIS value reached (40-60) which indicate optimal hypnotic state , anesthesia was maintained with oxygen 100%, sevoflurane (according to the depth of anesthesia guided by BIS to be between 40%-60%),muscle relaxation was maintained by additional doses of atracurium, guided by peripheral nerve stimulator ( Life-Tech EZstimII), mechanical ventilation with maintenance of end tidal carbon dioxide 36-40mmHg,all patients received 15mg/kg Pefalgan and 2 micogram /kg fentanyl IV. A wide bore IV cannula was also inserted. Hypotension defines as systolic blood pressure less than 90 mmHg was treated by decreasing the dexmedetomidine concentration and or sevoflorane concentration and ephedrine in 3 mg IV increments of needed, bradycardia is defined as heart rate less than 60 beat per minute and was managed by decreasing the dexmedetomidine concentration in D group or atropine 0.5mg IV if needed. At the end of surgery, 0.25% bupivacaine was injected by the surgeon at the surgical wound, neuromuscular blockade was reversed with IV neostigmine 0.04mg/kg and atropine 0.02 mg/kg, the trachea was extubated when the patient respond to commands, all patients were transferred to PACU, where they received oxygen via face mask 3-4 L/min and were monitored. The following parameters were evaluated and recorded by senior anesthesia resident unaware of the study protocol: 1. Patients’s characteristics : age, sex, height, weight, ASA physical status and duration of surgery. 2. Heart rate, systolic and diastolic arterial blood pressure, arterial oxygen saturation (SpO2): before induction, after induction of anesthesia, then every 15 minutes intraoperative. 3. Volume of blood loss (ml) :in the surgical swabs and suction bottle 4. Laboratory Hb and hematocrit concentration :(Pre, intra and immediate post-operative) 5. Number of units PRBCs transfused 6. Urine output (ml)