Addition of bicarbonate to plain bupivacaine does not significantly alter the onset or duration of plexus anesthesia.

BACKGROUND AND OBJECTIVES: In an effort to elucidate further the effect of alkalinization of bupivacaine on its anesthetic effect, a study was undertaken using alkalinized and non-alkalinized bupivacaine for lumbar plexus block and comparing the results with those obtained previously with brachial plexus block. METHODS: Thirty consenting adult patients about to undergo lower extremity surgery under regional anesthesia were selected for the study. All of the patients received an inguinal paravascular lumbar plexus block ("3-in-1 block"), along with a sciatic block to allow the anticipated surgery to be carried out. The patients were divided into two groups, one receiving plain "alkalinized" 0.5% bupivacaine; the other receiving plain "non-alkalinized" 0.5% bupivacaine. After each lumbar plexus block, the onset and duration of analgesia and anesthesia of the nerves derived from the lumbar plexus were determined by an independent investigator who was unaware of which solution had been administered. RESULTS: There was no statistically significant difference between the two groups with respect to the onset or duration of anesthesia and analgesia. CONCLUSIONS: The data obtained in the present study indicate that alkalinization of non-epinephrine-containing bupivacaine does not reduce the latency or increase the duration of analgesia or anesthesia after lumbar plexus block. Since most of the studies that do show such an effect of alkalinization were carried out using epinephrine-containing bupivacaine, it is postulated that in those studies alkalinization contributed to the decrease in latency and increase in duration, not so much by providing an increased amount of local anesthetic in the free base form, but by reactivating epinephrine's vasoconstrictor activity, which is inactivated by a low pH.

Continuous spinal anesthesia and post dural puncture headache: a retrospective study.

Continuous spinal anesthesia (CSA) fell into disuse because of a presumed high incidence of post dural puncture headache (PDPH). A careful retrospective study of 226 continuous spinal anesthetics administered for a variety of surgical (not obstetric) procedures was carried out and indicated that none of the patients developed PDPH. While 62% of the patients were older than 60 years of age, a group with a low incidence of PDPH, it was expected that some of the younger patients would develop this complication, especially since 94% of the dural punctures were carried out with 17- and 18-gauge needles. This study also revealed only a 12% incidence of hypotension, an impressive finding because 64% of the patients were considered ASA III or IV. There were no other intraoperative or postoperative complications or deaths due to CSA. This retrospective study indicates that CSA, properly carried out with 17- and 18-gauge needles, is not necessarily associated with a high incidence of PDPH; and in view of its low morbidity and mortality, CSA is particularly useful and safe in the poor-risk elderly patient. This study also raises the question as to whether there is a need for the recently developed (and expensive) microcatheters that fit through very small-bore needles.

A complete regional anesthesia technique for cardiac pacemaker insertion.

Sixteen consecutive adult patients scheduled for permanent transvenous cardiac pacemaker insertion received as their total anesthetic the combination of a cervical plexus block and blocks of the second, third, and fourth intercostal nerves using a combination of 1% mepivacaine and 0.2% tetracaine with epinephrine, 1:200,000. This technique consistently provided complete surgical anesthesia of the third cervical (C3) through the fourth thoracic (T4) dermatomes, without anesthesia of the brachial plexus. Anesthesia was adequate for the surgical procedure without the need for supplemental analgesia or anesthesia in all cases. Because fluoroscopy was used routinely for the surgical procedure, it was possible to document that there were no instances of diaphragmatic paralysis or pneumothorax. In contrast to other reports, this technique provides surgical anesthesia that is adequate for all of the approaches used for transvenous pacemaker implantation, except for placement of a battery in an abdominal pouch. There were no serious complications and/or side effects in any of the patients studied.

Brachial plexus block with a new local anaesthetic: 0.5 per cent ropivacaine.

A new local anaesthetic, ropivacaine hydrochloride, was used in a concentration of 0.5 per cent in 32 patients receiving a subclavian perivascular block for upper extremity surgery. One group (n = 15) received 0.5 per cent ropivacaine without epinephrine and a second group (n = 17) received 0.5 per cent ropivacaine with epinephrine in a concentration of 1:200,000. Anaesthesia was achieved in 87 per cent of the patients in both groups in all of the C5 through T1 brachial plexus dermatomes. Motor block was profound with 100 per cent of patients in both groups developing paresis at both the shoulder and hand and 100 per cent developing paralysis at the shoulder. There was a rapid initial onset of sensory block (a mean of less than four minutes for analgesia) with a prolonged duration (a mean of greater than 13 hr of analgesia). The addition of epinephrine did not significantly affect the quality or onset of sensory or motor block. The duration of sensory block was reduced by epinephrine at T1 for analgesia and at C7, C8, and T1 for anaesthesia. The duration of sensory block in the remaining brachial plexus dermatomes as well as the duration of motor block was not effected by epinephrine. There was no evidence of cardiovascular or central nervous system toxicity in either group with a mean dose of 2.5-2.6 mg.kg-1 ropivacaine.

Haemodynamic stability with midazolam-ketamine-sufentanil analgesia in cardiac surgical patients.

Although sufentanil in high doses may result in deep coma sufficient to conduct coronary-bypass surgery painlessly in patients, its side effects, e.g., bradycardia and hypotension, may lead to complications in some patients. Since ketamine causes central sympathetic stimulation, we attempted to counteract the vagomimetic effects of sufentanil by ketamine. Anaesthesia was induced in patients, (n = 15), for elective coronary artery-bypass surgery with 0.12 mg.kg-1 midazolam IV, followed by 1 mg.kg-1 ketamine and 0.6 micrograms.kg-1 sufentanil IV eight minutes later. Subsequently, pancuronium 0.1 mg.kg-1 was given to facilitate tracheal intubation. Three minutes later, the trachea was intubated, and ketamine 1 mg.kg-1.hr-1 IV infusion was started. Incremental doses of 0.6 micrograms.kg-1 sufentanil were given whenever a greater than 15 per cent increase in rate-pressure product was observed. The mean +/- S.E.M. dose of sufentanil before cardiopulmonary bypass was 6.5 +/- 0.6 micrograms.kg and 9.1 +/- 0.9 micrograms.kg for the entire procedure. Although midazolam alone caused reductions in systolic BP, SVR and LVSWI, other haemodynamic variables were not altered. The administration of this anaesthetic technique caused no clinically important adverse haemodynamic changes and/or ST-segment changes and prevented the adverse haemodynamic changes caused by intubation, skin incision, sternotomy and periaortic dissection. Adequate analgesia, complete amnesia and early recovery of wakefulness were observed.

pH adjustment schedule for the amide local anesthetics.

Several studies have indicated that the addition of sodium bicarbonate to solutions of local anesthetics to raise the pH closer to the pKa shortens the latency, increases the intensity, and prolongs the duration of the resultant neural blockade. However, the addition of too much bicarbonate will cause precipitation, and this may result in the injection of particulate free base along with the solution. The present study was carried out to determine the maximal amount of sodium bicarbonate that can be added to each of the amide local anesthetics without the formation of a precipitate, and, thus, to construct a pH adjustment schedule to simplify the alkalinization of local anesthetics in clinical practice.

Comparison of the hemodynamic effects of midazolam and diazepam in patients with coronary occlusion.

Midazolam is gradually replacing diazepam in neuroleptanalgesia with fentanyl and sufentanil because of its greater water solubility, greater hypnotic potency, shorter half-life, lack of pharmacologically active metabolites and low incidence of thrombophlebitis. In order to substantiate midazolam as being as safe and effective as diazepam in cardiac patients with severe coronary occlusion, hemodynamic measurements were made before and 10 min after completion of intravenous injection of 0.2 mg/kg i.v. midazolam (n = 45) and 0.4 mg/kg i.v. diazepam (n = 30), the doses which are identical to those used in patients undergoing cardiac catheterization. All 75 patients were spontaneously breathing 40% O2 in air. No positional changes or stimulation of patients were allowed before and during the study. Of hemodynamic variables, systemic systolic blood pressure was significantly reduced by both midazolam and diazepam. Midazolam also caused significant reduction in systemic vascular resistance with reduction in diastolic pressure and left ventricular stroke work index. No changes in heart rate, systolic and diastolic pulmonary artery pressures, cardiac output and index, stroke volume and index, pulmonary vascular resistance, right ventricular stroke work index and rate pressure product were observed following either midazolam or diazepam. No statistically significant differences were observed in any hemodynamic variable between those patients receiving midazolam or diazepam. It is concluded that midazolam is as safe as diazepam in cardiac patients with coronary obstruction.

Haemodynamic stability with midazolam-sufentanil analgesia in cardiac surgical patients.

Since the administration of both diazepam and midazolam are claimed to cause adverse haemodynamic effects following fentanyl or sufentanil intravenous injection, we evaluated the effectiveness and safety of the reverse sequence, (midazolam-sufentanil) on haemodynamic variables, adequacy of analgesia, amnesia and recovery in 15 adult patients undergoing coronary artery surgery (with a mean +/- SEM ejection fraction of 0.41 +/- 0.03). After routine premedication, midazolam 0.14 +/- 0.01 mg.kg-1 IV was given over one min followed 5 min later by sufentanil in incremental IV doses of 1.5 micrograms.kg-1 to a total pre-intubation dose of 4.0-5.0 micrograms.kg-1 injected in 10 min. One minute after the initial dose of sufentanil, pancuronium 0.1 mg.kg-1 IV was given in 30 seconds. The incremental doses of sufentanil were based on a greater than 15 per cent increase in rate-pressure product. The mean dose of sufentanil before cardiopulmonary bypass was 9.6 +/- 2.1 micrograms.kg-1 and 13.9 +/- 1.3 micrograms.kg-1 for the entire procedure. A significant decrease in systolic and diastolic blood pressures occurred after midazolam administration which was sustained until sternotomy. A significant reduction in systemic vascular resistance occurred following midazolam. Sufentanil reduced the left ventricular stroke-work index. Tracheal intubation, skin incision and sternotomy elicited no adverse haemodynamic responses. Adequate analgesia, complete amnesia and early recovery of wakefulness were observed.