This prospective, randomized study was carried out following approval from the institutional ethics committee. Patients included in this study were informed about the procedure in their own language, and a written informed consent was taken from all of them.
100, ASA grade 1 & 2 patients, between 18 to 60 years of age, weighing 40 to 70kgs,of both genders, scheduled for either elective or emergency lower limb or lower abdominal surgical procedures, which were anticipated to complete within 2 hours, were included. They were initially assessed in the preoperative checkup room, where along with general and systemic examinations, baseline measurements of heart rate, mean arterial pressure by noninvasive sphygmomanometer, pulse oximetry, respiratory rate, and baseline anxiety score on a 100mm visual analog scale were made by a single observer. Anxiety Score was recorded as 100 for those who were extremely anxious and 0 for those who were not anxious.
Patients with history of allergic reaction to the study drugs, those with significant cardiac , pulmonary, hepatic or renal dysfunction, Obese patients (>130% ideal body weight), those with history of chronic use of sedative drugs, full stomach patients, pregnant patients and epileptic patients were excluded from the study. Sedative premedication was not given to any patient to avoid interference with results. One intravenous cannula was inserted into the patient's dorsum of hand and Ringer's lactate infusion was started. Another wide bore intravenous access was established on the forearm of the other limb, for administration of the study drug infusion.
The patients were subsequently shifted to the operating room and were randomly allocated to receive either Propofol 1mg ml-1or Midazolam 0.1mg ml-1 in 5% dextrose in a 50 ml syringe through Injectomat MC Agilia 018190 syringe pump, Fresenius Kabi Laboratories, France. Propofol was initially started at an infusion rate of 6mg kg-1 hr-1 and Midazolam was started at an initial infusion rate of 0.5mg kg-1 hr-1 in order to achieve a desired level of sedation of score 4 on the Observer's Assessment of Alertness/ Sedation Scale and the time required in minutes to achieve score 4 was noted in each case by a single observer. The infusion rates were later lowered or raised in order to maintain sedation score 4.
Five minutes after the commencement of the sedative infusion subarachnoid black was instituted in the lateral position via a 22 or 23 gauge spinal needle by injecting sufficient doses of bupivacaine 0.5% in order to achieve an adequate sensory block for the proposed surgery. The optimum level of sensory block was assessed 10 minutes after the injection of the spinal drug and noted.
Heart rate, mean arterial pressure, SPO2, respiratory rate and anxiety score were recorded initially at 5 minute intervals for 10 minutes and later at 10 minute intervals till the end of procedure. All patients were given supplemental oxygen via venture mask at 4 liters/minute.
Visual Task of Recall of Pictures
Immediately prior to receiving the sedative infusion, each patient was shown a picture of a commonly occurring object (e.g. kite, dog, tree etc.) to assess their baseline recall (picture1)
At 30 minutes after starting the sedative infusion, another picture (picture 2), different from the first picture, was shown to the patient, for assessing intraoperative recall.
Similarly, at the end of the sedative infusion a third picture (picture 3) different from the first two pictures was shown to the patient. Each picture was shown to the patient for 30 seconds, during which time the patient was prompted to describe all details he or she saw in the picture.
Verbal Task of Recall of Words
30 minutes after commencing the sedative infusion, in order to assess intraoperative recall, a list of 5 commonly used words were told to the patient, close to him, by a single observer. Each word was repeated twice at 5 second intervals with a pause of 10 seconds between two different words.
4 hours postoperatively, the patient was asked to recall the preoperative, intraoperative pictures and words shown or spoken to him or her. Those correctly recalled were analyzed. If the recall of pictures was unsuccessful, the patients were asked to recognize any of the previously presented pictures among other pictures they had not seen by showing a mixed collection of 5 displayed and undisplayed pictures. Patients were also asked regarding recall of insertion of spinal needle.
During the intraoperative period, evidence of pain on commencement of infusion, bradycardia, hypotension, apnea, involuntary movements, limb twitching, excitatory phenomenon, bradypnea, fall in oxygen saturation, confusion and appearance of rash was noted.
The sedative infusion was stopped 5 minutes prior to skin closure or end of surgery. Duration of procedure (Dp) was taken as time from commencement of infusion to stoppage of infusion. Total drug used was measured in milligrams.
In the immediate postoperative period, time taken by the patient to achieve sedation score 5, and correctly give full name and address (recorded preoperatively) was noted as Recovery time. Postoperative side effects, if any, such as, nausea, vomiting, apnea, confusion, delirium, etc. were noted and treated.
Block randomized allocation method was used to divide the patients into two equal groups (n==50), with the help of numbered cards.
The results were analyzed using Student's paired & unpaired t test and chi square test. A ‘p’ value of <0.05 was considered as statistically significant, whereas ‘p’ value of <0.001 was taken as highly significant.