12.5 mg of 0.5% hyperbaric bupivacaine

15 mg of 0.5% isobaric ropivacaine

12.5 mg of hyperbaric bupivacaine 0.5% for spinal anesthesia in geriatric patients undergoing total knee arthroplasty

The assessment of sensory block to pinprick was performed at 2, 4, 6, 8, 10, and 15 min after the intrathecal injection and then every 15 min until regression to L5. Results of the pinprick test were determined bilaterally at midclavicular level by using a short-beveled 27-gauge needle. Response to pain we determined by asking the patient whether or not he feels pain with the pinprick.

Motor block in the lower limb was assessed by using a modified Bromage scale (0 = no paralysis , 1 = unable to raise extended leg , 2 = unable to flex knee , 3 = unable to flex ankle). These assessments were performed immediately after the assessments of sensory block until the return of normal motor function.

All patients of these 2 groups were assessed and monitored for Haemodynamics using ECG for heart rate (HR). Baseline values were defined as heart rate values before the preanesthetic infusion. The values were recorded before the induction and then every 5 min until discharge from the recovery room.

All patients of these 2 groups were assessed and monitored for Haemodynamics as regards non invasive mean arterial blood pressure (MAP). Baseline values were defined as blood pressure values before the preanesthetic infusion. The values were recorded before the induction and then every 5 min until discharge from the recovery room.

Respiratory depression (defined as respiratory rate < 8 min and SPO 2 < 90%)