We examined the onset and the quality of sensory and motor block of the lumbosacral roots during epidural anesthesia performed for foot or ankle surgery with lidocaine HCl, pH adjusted, or carbonated lidocaine in a randomized, double-blind study. Forty-five patients received 20 mL of one of three solutions: control group (n = 15), 20 mL of 2% lidocaine with epinephrine (5 micrograms/mL) plus 2 mL of NaCl 0.9% (pH 4.58 +/- 0.10); pH adjusted group (n = 15) 20 mL of lidocaine with epinephrine (5 micrograms/mL) plus 2 mL of 8.4% sodium bicarbonate (pH 6.47 +/- 0.16); and carbonated group (n = 15) 20 mL of 1.73% carbonated lidocaine with epinephrine (5 micrograms/mL) plus 2 mL of 0.9% NaCl (pH 6.42 +/- 0.04). Onset time of sensory block of the L4-S1 roots and maximum cephalad spread were similar in the three groups. Surgical anesthesia was significantly poorer with lidocaine HCl compared to the carbonated solution with eight patients requiring fentanyl supplementation versus one in the carbonated group. Complete motor block was observed in eight patients of the carbonated group compared to three in the pH adjusted group (P < 0.01) and one in the control group (P < 0.005). Lidocaine venous blood levels were comparable in the three groups. When compared to lidocaine HCl, only carbonated lidocaine, but not the pH adjusted solution, significantly improved epidural block of the L4-S1 roots.
The effects of the sitting position on the quality of both sensory and motor blockade of segments L5 and S1 and the haemodynamic consequences during epidural anaesthesia were studied on 39 patients undergoing ankle or foot surgery. After insertion of an epidural catheter with the patient in the lateral position, 19 patients were kept sitting for 15 min following the injection of the local anaesthetic and 20 remained supine for the duration of anaesthesia (control group). All patients received a dose of 20 ml of 1.73% carbonated lidocaine with epinephrine 1:200,000. The quality and time of onset of the sensory blockade for segments L1-S2 as well as its cephalad spread were comparable in both groups. Fourteen patients of the sitting group achieved motor blockade of more than three of five myotomes compared with five patients in the supine group (P less than 0.001). The maximum decrease in mean arterial pressure occurred sooner in the sitting group (14 +/- 9 min) than in the control group (21 +/- 10 min; P less than 0.01) and was more severe (-24 +/- 10% vs -16 +/- 10% respectively; P less than 0.05). Our results indicate that placing the patient in the sitting position for 15 min after inducing epidural anaesthesia does not influence caudal sensory blockade but does increase the depth of motor blockade.
The influence of variations in the volume of injectate when maintaining an identical dose of a hyperbaric local anesthetic has not previously been investigated when performing spinal anesthesia. This study compares spinal anesthesia of 5 mg of lyophilized tetracaine diluted in 1 ml, 2 ml or 4 ml of 10% glucose in 45 elderly patients undergoing elective hip surgery. While supine and horizontal, each patient received double-blind one of the three solutions through a catheter inserted 4 cm into the intrathecal space at the L2-L3 or L3-L4 interspace. No difference in the anesthetic effects was found between the three groups. The median value of the maximal sensory level was T6 (range T3-L2), T4 (range T3-T9) and T5 (range T3-T11) in the 1-ml, 2-ml, and 4-ml groups, respectively. The number of patients with a motor blockade of grade 2 or 3 was 12/15, 14/15 and 13/15, and the time from the initial dose to the need for the first top-up dose (mean +/- s.d.) was 88 +/- 35 min, 75 +/- 15 min and 68 +/- 15 min for the 1-ml, 2-ml and 4-ml groups, respectively. Hemodynamic changes were also comparable between the three groups. The authors conclude that in elderly patients, undergoing spinal anesthesia while supine and horizontal, variations in volume from 1 to 4 ml do not influence the characteristics of hyperbaric spinal anesthesia while injecting an identical dose of local anesthetic.
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