Evaluation of Anxiolysis and Pain Associated With Retrobulbar Eye Block for Cataract Surgery : Melatonin Versus Gabapentin ( A Randomized, Double-blind, Placebo-controlled Study)

Principle goals of sedation for eye surgery are to provide patient comfort and to allow the patient to stay calm during both retrobulbar injection and surgery. Insufficient sedation may not prevent the patient from moving during retrobulbar injection, whereas very deep sedation may result in respiratory complications during surgery .The investigators compared the effect of melatonin and gabapentin on the hemodynamic parameters, sedation ,anxiety, and pain and satisfaction profile in cataract surgery. After approval by the Hospital Evaluation Committee of Scientific Studies for ethical purpose and written informed consent, ninety patients scheduled for cataract surgery by phacoemulsification were randomly allocated to three study groups to receive melatonin 6 mg (Group M, n = 30) , gabapentin 600mg(GroupG, n = 30)or placebo(GroupP, n=30) 90 minutes before retrobulbar injection. . Hemodynamic parameters ,anxiety, sedation score , and pain during block and surgery, satisfaction of surgeon were assessed. . At the preoperative visit verbal pain score (VPS) of 10 (0 = no pain and 10 = worst pain imaginable) and verbal anxiety score (VAS) ranging from 0 to 10 (0= completely calm, 10 = the worst possible anxiety) were explained to patients. Then a 20 gauge cannula was inserted into one of the two hands. Patients were monitored with electrocardiogram, noninvasive measurement of blood pressure, and pulse oximetry (SPO2). Retrobulbar nerve block was performed by the same ophthalmic surgeon who was unaware of group allocation with 1.5 ml of solution that prepared by nurse( lidocaine 2%and 0.5 ml bupivacaine) via the percutaneous route with a 25 G, 38 mm Atkinson needle (John Weiss & Son Limited, Milton Keynes,England), at inferotemporal site. No patient received an additional facial nerve block. The investigators assessed the pain immediately after block and surgery. Anxiety score and pain score was recorded in each patient before premedication (T1), ninety minutes after premedication, on arrival in the operating room (T2), one minute after retrobulbar block placement (T3)during the operation period) (T4) and postoperatively before discharging the patient from the recovery room (T5) .At the end of surgery, the patients were asked about average level of their anxiety and pain during the operation period according to the VAS and VPS explained to them before premedication.'. The surgeon was also asked to verbally rate their level of satisfaction according to three degree scale as "very bad, , moderate, good after the operation. The sedation level of patients during performance of block was assessed as Sedation scores were obtained on a 3 point scale with 0 =movements of the head, arms and trunk ,1 =slightly movement of arms,2=slightly change in face,3=complete calm. If sedation was inadequate, fentanyl could be given 0.5microgram/kg as needed.