Sedation Complications in Urology During Spinal Anesthesia With Dexmedetomidine or Midazolam Regarding OSA Risk

All participants were premedicated with diazepam 5mg 12 hours and 1 hour before surgery. Thromboprophylaxis (enoxaparin 4000-6000 IU) depending on the body weight was given at least 12 hours before surgery.

Participants were divided by STOP-BANG(Snoring history, Tired during the day, Observed stop breathing while sleep, High blood pressure, BMI more than 35 kg/m2, Age more than 50 years, Neck circumference more than 40 cm and male Gender) questionnaire into one of two groups: high OSA and low&medium OSA. Each group was then allocated by permuted block randomisation into midazolam or dexmedetomidine group. The randomisation list was obtained from R program. The group allocations were contained in closed envelope that were opened before surgery after the completed enrollment procedure.

Participants got IV cannula with switch for continuous intravenous infusion in operating theatre. Non invasive monitoring (electrodes for ECG, blood pressure cuff and pulse oximeter) was placed before induction of spinal anesthesia. Skin was disinfected and 40mg of 2% Lidocaine was given subcutaneously at lumbar vertebrae 3/4 level. 25 G spinal needle was used and after dura and arachnoidea were pierced 12.5-15 mg of 0.5% Levobupivacaine was applied. Participants were then positioned in uniform lithotomy position and 9cm pillow was inserted. After sensory block, defined as the absence of pain at T10 dermatome, was induced by needle-tip test by the anaesthesiologist, the surgery was initiated.

Time after subarachnoid block was T0 and sedation with midazolam or dexmedetomidine was started via continuous intravenous infusion. Midazolam was started with 0.25 mg/kg of ideal body mass, and dexmedetomidine with 0.5 ug/kg through 10 minutes. Every 10 minutes sedation level was observed with Ramsay sedation scale (RSS). Drug was titrated to achieve RSS of 4 or 5 (closed eyes and patient exhibited brisk or sluggish response to light glabellar tap or loud auditory stimulus). Independent blinded doctor was assessing RSS level, vital parameters and signs of airway obstruction every 10 minutes. Every 10 minutes systolic, diastolic and mean arterial pressure(MAP) were noticed along with heart rate, oxygen saturation by pulse oximetry(SpO2), RSS level and adverse intraoperative events: snoring as sign of airway obstruction, cough and restlessness as disturbing factors to surgeon. If peripheral oxygen fell below 90% supplemental oxygen was delivered by facemask with reservoir bag at flow of 10 L/min. End tidal carbon dioxide(CO2)was measured for detection of possible apnea. If oxygenation was still inadequate chin lift and jaw thrust maneuver were performed and oropharyngeal airway was inserted if needed. If heart rate fell below 50 bpm atropine 0.1 mg/kg was given and if systolic blood pressure fell below 100 mmHg(or MAP < 65 mmHg) ephedrine 5mg bolus was given. Total crystalloid infusion volume was noticed at the end of surgery. All measurements were performed every 10 minutes and 1 hour after surgery in urology intensive care. High risk OSA participants underwent cardiorespiratory polygraphy at Center for sleep medicine Split.

Inclusion criteria

• elective transurethral resection of bladder and prostate
• American Society of Anesthesiologists (ASA) physical status classification system: I, II, III

Exclusion criteria

• regional anesthesia contraindications
• American Society of Anesthesiologists (ASA) physical status classification system: IV
• Atrioventricular cardiac block II and III degree
• Psychotic disorders
• Participants with tracheostomy
• Dementia
• Allergy on Dexmedetomidine or Midazolam