Francis X. Riegler

Effects of aerosolized and/or intravenous lidocaine on hemodynamic responses to laryngoscopy and intubation in outpatients

A randomized, double-blind study was carried out on 40 unpremedicated, ASA I-II adult surgical outpatients to assess the effects of aerosolized lidocaine, intravenous lidocaine, both, orneither, on circulatory responses to laryngoscopy and intubation. Lidocaine (4 mg/kg) or saline was given by nebulizer in the holding area beginning at −15 minutes. The patient underwent a standarized induction of anesthesia that included IV curare (3 mg) and O2 by facemask at minute 2, followed by IV thiopental (5 mg/kg) and succinylcholine (1.5 mg/kg) at minute 5. Lidocaine (2 mg/kg) or saline was given by IV push at minute 4. Laryngoscopy was begun at 5 minutes and continued for 45 seconds before intubation. Heart rate and systolic, diastolic, and meanblood pressures were automatically recorded at 1-minute intervals from 0 to 11 minutes. The fourtreatment groups included: group 1, aerosolized and IV saline; group 2, aerosolized saline, IV lidocaine; group 3, aerosolized lidocaine, IV saline; and group 4, aerosolized and IV lidocaine. There were no differences among the four treatment groups (n = ten per group) in any of the fourhemodynamic variables before laryngoscopy and intubation. Within each group, after intubation all four hemodynamic variables increased significantly over the corresponding baseline values for that group. However, the maximum values attained after intubation did not differ significantly among the four treatment groups for any of the four hemodynamic variables, whether those maxima were expressed as absolute values or as a percentage of baseline. Having found no difference in the effects of aerosolized and/or intravenous lidocaine and saline placebo on hemodynamic response to laryngoscopy and intubation in adult surgical outpatients using a rigidly standardized protocol, it is recommended that such usage of lidocaine be abandoned.

A Randomized, Double-blind Comparison of the Effects of Interpleural Bupivacaine and Saline on Morphine Requirements and Pulmonary Function after Cholecystectomy

The effect of interpleural bupivacaine and saline placebo on morphine requirements and pulmonary function after cholecystectomy was investigated. Twenty-six patients were randomly assigned on postoperative day 1 to receive either 20 ml preservative-free saline (group 1) or 20 ml 0.5% bupivacaine with epinephrine, 5 micrograms/ml (group 2) through an interpleural catheter. Adequacy of pain relief was determined by the amount of morphine used by the patient following interpleural injection. Morphine use via a patient-controlled analgesia (PCA) system was recorded for several hours before and after interpleural injection. All patients had a forced vital capacity (FVC) and FEV1 measurement immediately before and 1 h after interpleural injection. Mean hourly PCA morphine use ranged from 1.6 to 2.8 mg for the 6 h prior to interpleural treatment for groups 1 and 2. There was no difference in PCA use between the groups during this time. Group 1 patients did not reduce PCA morphine use after interpleural saline. Patients in group 2, however, significantly reduced PCA morphine use after interpleural bupivacaine. Mean PCA morphine use for group 2 was 0.38 +/- 0.15 mg/h (mean +/- SE) (81% reduction vs. control) for the first 2 h after bupivacaine (P less than 0.05). Mean PCA use in group 2 was 0.52 +/- 0.2 mg/h (73% reduction vs. control) for the third hour after bupivacaine (P less than 0.05). At the fourth and fifth hours after bupivacaine injection, mean PCA morphine use was not significantly different from that in group 1. FVC and FEV1 did not improve after interpleural saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Interpleural anesthetics in the dog: differential somatic neural blockade

Differential somatic neural effects of interpleural bupivacaine were determined in dogs. Alterations in evoked responses were used as a marker of neural blockade. Electrode pairs were fastened to the external surface of the right seventh ribs of five male mongrel dogs (25-30 kg) at distal (D), middle (M), and proximal (P) locations. Electrodes were similarly fastened to the ipsilateral laminae of the fifth (T5L), seventh (T7L), and ninth (T9L) thoracic vertebrae, and the contralateral cranium over the sensorimotor cortex (SMC). Pediatric feeding tubes were used as interpleural catheters. Following interpleural bupivacaine (10 ml, 0.5%) intercostal nerve block was produced, as manifested by decreases in amplitude (range 12-32% of control, P less than 0.05), and increases in latency (range 108-126% of control, P less than 0.05), of evoked potentials recorded between T7L and rib electrodes. The block was found to localize over dependent portions of the rib with changes in animal position, indicating a strong influence of gravity. No significant changes were seen in potentials recorded between T9L and T5L, and T9L and SMC, regardless of position. T9L-T5L and T9L-SMC potentials were abolished or severely attenuated following direct subarachnoid or epidural injection of bupivacaine at T7. Thus, there are no spinal, epidural, or gross CNS effects of interpleural bupivacaine.

CONTINUOUS INFUSION OF INTERPLEURAL BUPIVACAINE MAINTAINS EFFECTIVE ANALGESIA AFTER CHOLECYSTECTOMY

Twenty‐five patients who had undergone elective cholecystectomy were prospectively randomized to receive via an interpleural catheter either a continuous infusion of 0.25% bupivacaine at 0.125 mL·kg−1·h−1 (n = 13) or repeated bolus injections (n = 22) of 0.5% bupivacaine with epinephrine 1:200,000 at 0.4 mL/kg every sixth hour. Adequacy of pain relief was measured by the amount of patient‐controlled analgesia morphine required postoperatively and by patient scores on a visual analog scale obtained every sixth hour. Two venous blood samples for measurements of serum bupivacaine levels were obtained from patients in the continuous group at hours 6 and 24; four blood samples were obtained from patients in the bolus group, both immediately before and 30 min after injections at hours 6 and 24. Among the patients receiving the bolus injections, morphine was required 62 ± 15 (SEM) times over the 24-h study period with total morphine dosage averaging 30 ± 15 mg. Corresponding values for patients in the continuous group were 35 ± 10 times and 23 ± 5 mg of morphine. The difference was not, however, statistically significant, but when activity during the 2-h time periods immediately before reinjection ere examined, patients in the bolus group required and received significantly more morphine than did those in the continuous group (P<0.05). Patients in the continuous group had visual analog scale scores that averaged 2.9 ± 0.6 over the 24-h study period. Patients within the bolus group had visual analog scale scores before and again 30 min after injection that averaged 5.8 ± 0.8 arid 1.8 ± 0.5, respectively (P<0.05). Serum bupivacaine levels increased in both groups between the sixth and 24th hour measurements; the average postinjection bupivacaine levels were significantly higher (P<0.05) with intermittent injection than corresponding levels in the continuous infusion group. The bupivacaine level rose to 3.2 ± 0.4 μg/mL 30 min after the bolus injection at hour 24. In summary, continuous interpleural infusion of 0.25% bupivacaine provides safer and more effective postoperative pain relief after cholecystectomy than does intermittent interpleural injection of 0.5% bupivacaine with epinephrine every 6 h.