Intravenous lipid emulsion for levobupivacaine intoxication in acidotic and hypoxaemic pigs.

Intravenous lipid emulsion is, in some countries, the recommended treatment for local anaesthetic toxicity. Systemic local anaesthetic toxicity results in hypoxaemia and acidosis, and whether this influences the effects of lipid therapy on drug concentrations and cardiovascular recovery is currently unknown. Twenty anaesthetised pigs were given a 3-mg/kg bolus of levobupivacaine followed by a five minute phase of hypoventilation and 1 mmol/kg of lactic acid in one minute. After lactic acid infusion, pigs were treated, in randomised order, with either 20% lipid emulsion or Ringer's acetate for 30 min: a 1.5-ml/kg bolus followed by a 0.25-ml/kg/minute infusion. Haemodynamic parameters were recorded and blood samples were collected for pharmacokinetic analysis. There was no difference between the groups in the area under the plasma levobupivacaine concentration-time curve (AUC) or between that and AUC of unentrapped levobupivacaine in the Lipid group, or in the plasma half-lives. The cardiovascular outcome and normalisation of the electrocardiogram were similar in both groups. Five pigs developed marked hypotension: one in both groups died, while two in the Lipid group and one in the Ringer group needed adrenaline. Administration of lipid emulsion did not improve cardiovascular recovery from levobupivacaine toxicity exacerbated by acidosis and hypoxaemia. Lipid emulsion did not entrap levobupivacaine or affect levobupivacaine pharmacokinetics.

Neural nets and prediction of the recovery rate from neuromuscular block.

BACKGROUND AND OBJECTIVE: The aim was to train artificial neural nets to predict the recovery of a neuromuscular block during general anaesthesia. It was assumed that the initial/early neuromuscular recovery data with the simultaneously measured physical variables as inputs into a well-trained back-propagation neural net would enable the net to predict a rough estimate of the remaining recovery time. METHODS: Spontaneous recovery from neuromuscular block (electrically evoked electromyographic train-of-four responses) were recorded with the following variables known to affect the block: multiple minimum alveolar concentration, end-tidal CO2 concentration, and peripheral and central temperature. RESULTS: The mean prediction errors, mean absolute prediction errors, root-mean-squared prediction errors and correlation coefficients of all the nets were significantly better than those of average-based predictions used in the study. The root-mean-squared prediction error of the net - employing minimum alveolar concentrations from the whole recovery period (the recovery time from E2/E1 = 0.30 to E4/E1 = 0.75; E1 = first response of train-of-four, E2 = second response of train-of-four, etc.)--were significantly smaller than those of other nets, or the same net employing minimum alveolar concentrations only from the initial recovery period (from E2/E1 = 0.30 to E4/E1 = 0.25). CONCLUSIONS: Neural nets could predict individual recovery times from the neuromuscular block significantly better than the average-based method used here, which was supposed to be more accurate than guesses by any clinician. The minimum alveolar concentration was the only monitored variable that influenced the recovery rate, but it did not aid neural net prediction.

Technical aspects and postoperative sequelae of spinal and epidural anesthesia: a prospective study of 3,230 orthopedic patients.

BACKGROUND AND OBJECTIVES: Major complications after spinal or epidural anesthesia are extremely rare. The occurrence of less serious and transient sequelae and complaints may be underestimated if there is no established organization for the systematic and continuous surveillance of patients after anesthesia. This study was designed to evaluate the possible relationship between various block-related occurrences and the intra- and postoperative side effects and complaints. METHODS: This prospective study included 3,230 orthopedic patients operated on under neuraxial block. The block was performed by single-dose (single-shot spinal anesthesia [SPIN], 80.6%), continuous spinal anesthesia (CSA, 10.3%), or combined spinal and epidural anesthesia (CSE, 9.1%) technique. The patient position during surgery and a detailed description of block performance and equipment, as well as all intraoperative problems, were immediately recorded. Every patient was given a standardized questionnaire to be completed and returned after 1 week. RESULTS: The overall incidence of paresthesia was 12.8%, being most frequent during spinal catheter insertion with multiple attempts. Postoperative sensory disturbances (numbness, dysesthesia) occurred unrelated to paresthesia elicited by the puncture or catheterization. The failure rates (SPIN, 1.0%; CSA, 1.5%; and CSE, 1.0%) were quite low. Asystole with successful resuscitation, occurred in 1 patient with CSE but, overall, hemodynamic perturbations were more common with the continuous techniques. On the first postoperative day, decreased sensation of the skin was significantly more frequent after the continuous techniques, still present in 6.5% of SPIN patients, 6.1% of CSA patients, and 17.2% of CSE patients 1 week after surgery. These disturbances were also related to the use of a tourniquet and lateral position of the patient during surgery. The frequency of postdural puncture headache (PDPH) was similar for the different techniques (SPIN, 0.9%; CSA, 1.5%; and CSE, 1.7%). About one third of the patients reported strong postoperative pain on the day after the operation, and 5.6% continued to report this at 1 week. CONCLUSIONS: Although sensory changes were quite frequent, they were mild and transient. Rather than having been caused by the anesthetic technique, per se, a "nonanesthetic" reason (position, tourniquet, immobilization) should also be considered as their origin. Sensory disturbances, as well as strong pain for at least a week, were reported by several patients, and to become aware of these problems and improve the quality of treatment, a universal regional anesthesia follow-up system is recommended.

Evaluation of efficacy and plasma concentrations of ropivacaine in continuous axillary brachial plexus block: high dose for surgical anesthesia and low dose for postoperative analgesia.

BACKGROUND AND OBJECTIVES: Ropivacaine is a potent local anesthetic that, experimentally at low concentrations, produces an effective block of pain conducting nerve fibers. Therefore, it was hypothesized that 0.1% and 0.2% ropivacaine would provide clinically adequate postoperative analgesia in continuous axillary plexus block. METHODS: Sixty patients (ASA I-II) scheduled for elective hand or forearm surgery received 5 mg/kg of 0.75% ropivacaine for axillary block using nerve stimulator technique. One hour later, in random order, a continuous infusion of either 0.1% ropivacaine (0.125 mg/kg/h), 0.2% ropivacaine (0.25 mg/kg/h) or saline 6 to 11 mL/h was started. RESULTS: The mean total ropivacaine dose for the surgical block was 5.1 to 5.2 mg/kg with the supplementation. All patients were pain free for the first 12 to 15 hours after the block. The need for postoperative analgesics during the infusion was similar in all groups. After the initial block, the maximum plasma concentrations (mean 2.5 microg/mL) were measured at 45 or 60 minutes after injection. The highest individual plasma concentration was 4.2 microg/mL. Despite the high venous peak concentration, no toxic reactions were observed. The mean peak plasma concentration (Cmax) was 2.2+/-0.5 microg/mL for saline, 2.6+/-0.8 microg/mL for 0.1% ropivacaine, and 2.6+/-0.7 microg/mL for 0.2% ropivacaine. During the continuous infusion of 24 hours, the ropivacaine concentration declined steadily. CONCLUSIONS: Ropivacaine is safe and effective for axillary brachial plexus block. The continuous infusion of 0.1% or 0.2% ropivacaine was no more beneficial than an infusion of saline in relieving postoperative pain in patients having elective hand surgery. None of the infusions were sufficient to adequately treat the patients' pain without the addition of adjunct agents.

Comparison of 0.5% articaine and 0.5% prilocaine in intravenous regional anesthesia of the arm: a cross-over study in volunteers.

BACKGROUND AND OBJECTIVES: Earlier studies of the use of articaine in intravenous regional anesthesia (IVRA) are conflicting. In fact, despite similar physicochemical properties and regional anesthetic action, significant differences between articaine and prilocaine in IVRA have been reported. Articaine, being a potent local anesthetic with low degree of toxicity and being rapidly metabolized by esterases, could be a useful local anesthetic particularly in IVRA and, perhaps, could challenge prilocaine, the present local anesthetic of choice for this technique. METHODS: A double-blind, cross-over study of IVRA of the upper extremity in 10 healthy volunteers was performed. There was at least a 1-week interval between the use of the two anesthetics in each volunteer. After exsanguination with an Esmarch bandage, IVRA was induced either with preservative-free 0.5% articaine (5% Ultracaine, Hoechst, Germany, diluted with 0.9% NaCl) or 0.5% prilocaine (Citanest, Astra, Södertälje, Sweden) (35-50 mL, according to weight), injected in 2 minutes. Sensation at defined skin spots that were innervated by the median, musculocutaneous, radial, and ulnar nerves was tested by pinprick; motor function was tested by the movements of the wrist. After 20 minutes, the tourniquet cuff was deflated in one step. Circulatory, toxic, and skin reactions were registered. At least 1 week after the second IVRA intracutaneous allergy testing with 0.5% articaine, 0.5% prilocaine, histamine, and saline was performed. RESULTS: There were no significant differences between the two local anesthetics in the onset of analgesia or anesthesia, degree of motor block, and recovery of IVRA. Onset of analgesia occurred 4.2-5.6 minutes, on average, after the injection. One volunteer had short-lasting tinnitus after tourniquet cuff deflation when prilocaine was used. Erythematous nonitching skin rashes developed in 8 of 10 volunteers when articaine was used, and two volunteers had rashes when prilocaine was used. These rashes disappeared within an hour, and negative intracutaneous test results confirmed their nonallergic origin. CONCLUSION: Both 0.5% articaine and 0.5% prilocaine, in a median dose of 40 mL in adults, injected in 2 minutes, are effective and equipotent local anesthetics in IVRA of the arm. An earlier reported four-time faster onset time of the block by articaine in comparison with prilocaine may be caused by a very rapid injection rate (40 mL/30 sec) by the investigators of that study. The erythematous skin rashes after IVRA, in particular when articaine was used, may be a sign of venous endothelial irritation.

Comparison of double-hole and single-hole pencil-point needles for spinal anesthesia with hyperbaric bupivacaine.

BACKGROUND AND OBJECTIVES: The use of thin single-hole pencil-point (SHPP) spinal needles may be a reason for subarachnoid maldistribution of local anesthetic. A new double-hole pencil-point (DHPP) needle may be preferable because of a theoretic more uniform initial distribution of local anesthetic. METHODS: This was a prospective, double-blinded study of 50 patients randomly selected to have spinal anesthesia using either single-hole 27-gauge (B. Braun, Melsungen, Germany) or double-hole 26-gauge (A.L.B. Medical Inc., U.S.A.) pencil-point needles. The former were inserted with the side port directed caudally and the latter with openings in both caudal and cranial direction. Two milliliters of hyperbaric 0.5% bupivacaine were injected in 1 minute, and sensory and motor block were studied at regular intervals during spinal anesthesia. All patients were interviewed on the first (personal) and the seventh (mailed questionnaire) postoperative day. Furthermore, microscopic inspection of the spinal needles was performed. RESULTS: There were no statistically significant differences in sensory or motor block levels between the two needle types at any time during spinal anesthesia. Likewise, there was no difference in the duration of spinal block. The postanesthetic side effects (headache, backache, pricking, numbness, weakness) were similar in both groups. Light and electron microscopic examination showed resistance of the SHPP needles to tip damage. On the other hand, the DHPP needle tips seemed to be distorted quite frequently, and, even in unused needles, the tip was blunt and asymmetric. CONCLUSION: There was no difference between the spread of analgesia using either SHPP or DHPP spinal needles. The DHPP needles appear to be vulnerable to tip damage from mechanical contact.

Comparison of eltanolone and thiopental in anaesthesia for termination of pregnancy.

Eltanolone, a new steroid hypnotic, was compared to thiopental in short anaesthesia. Sixty unpremedicated, Asa 1-2 women were randomized to receive eltanolone 0.6 (group E1) or 0.8 mg.kg-1 (group E2) or thiopental 4 mg.kg-1 (group T) for induction of anaesthesia. One minute before induction glycopyrrolate 0.2 mg and alfentanil 15 micrograms.kg-1 i.v. were administered. If induction failed, additional boluses of the test drug were given. Anaesthesia was maintained with 67% nitrous oxide in oxygen, and additional bolus doses of the test drug were given in a standardized fashion, if needed. Recovery was assessed by a research nurse blinded to the agent used. Mean +/- s.d. induction doss were 0.7 +/- 0.1 mg.kg-1 (group E1), 0.8 +/- 0.1 mg.kg-1 (group E2) and 4.0 +/- 0.0 mg.kg-1 (group T). Induction time was prolonged in the group E1 compared to the other two groups (P < 0.05). Side effects were few in all groups, but involuntary muscle movements or hypertonus occurred in 23% of the patients in the eltanolone and in 3% in the thiopental groups (n.s). Early recovery (eye opening, orientation and sitting) was slower in both eltanolone groups compared to the thiopental group (P < 0.01). No differences between the groups were found in toleration of oral fluids, walking, voiding, postoperative analgesic requirements or postoperative nausea and vomiting.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery from sevoflurane and isoflurane anaesthesia after outpatient gynaecological laparoscopy.

As the low blood solubility (blood gas partition coefficient 0.69) of sevoflurane suggests a rapid emergence from anaesthesia, recovery from sevoflurane anaesthesia was compared to isoflurane in outpatient gynaecological laparoscopy. Fifty ASA I or II, consenting women participated in a randomised, controlled and single blind study. The patients received, after induction of anaesthesia with propofol, either sevoflurane or isoflurane, both with 67% nitrous oxide in oxygen, for maintenance of anaesthesia. The study drug was administered at 1 MAC (end tidal concentration 0.6% for sevoflurane and 0.5% for isoflurane) but adjusted in 0.5 MAC steps, if clinically indicated. Before the end of surgery the end tidal concentration of the study drug was reduced to 0.5 MAC. Recovery assessments were made from the time anaesthetic gases were discontinued. The subjects were able to open eyes in 2.3 (0.8-7.0) min and 4.1 (2.0-6.8) min, orientate in 2.8 (1.0-6.8) min and 4.7 (2.2-8.3) min and follow orders in 2.6 (0.7-6.8) min and 4.3 (1.2-7.3) min, in the sevoflurane and isoflurane groups, respectively (P < 0.05) [median (range)]. Walking was achieved in 72 (24-464) min and 66 (35-134) min, tolerance of oral fluids in 37 (15-88) min and 35 (45-161) min and voiding in 262 (96-459) min and 217 (52-591) min in the sevoflurane and isoflurane groups, respectively (NS). Overall home readiness was achieved in 281 (96-708) min after sevoflurane group and 242 (96-591) min after isoflurane (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of intramuscular dexmedetomidine and midazolam premedication for elective abdominal hysterectomy.

The purpose of this study was to compare the perioperative effects of the intramuscular (i.m.) alpha 2 agonist, dexmedetomidine (DEX), and midazolam (MID) premedication. The study comprised 192 women (64 per group) scheduled for abdominal hysterectomy. The doses of the study drugs were chosen to obtain equal sedative effects. The three groups were: 1) i.m. DEX (2.5 micrograms/kg) and intravenous (i.v.) placebo (DexPla group), 2) i.m. DEX and i.v. fentanyl (FENT) (1.5 micrograms/kg) (DexFent group), and 3) i.m. MID (0.08 mg/kg) and i.v. FENT (MidFent group). I.m. drugs were administered 45-90 min before induction of anesthesia. Preoperative sedation and anxiolysis after DEX was comparable to that after MID. The maximum arterial blood pressure response to endotracheal intubation was blunted in the DexFent group, while in the two other groups blood pressure increased 30-34 mm Hg after endotracheal intubation. The mean isoflurane concentration during surgery was 0.14% in the DexFent group, 0.24% in the DexPla group, and 0.34% in the MidFent group (P < 0.001). During surgery, bradycardia (heart rate < 40 bpm) was observed in 6.2% of DEX patients, and no MID patients, whereas postoperatively 14.1% of DEX patients and 1.6% of MID patients had bradycardia. Fewer patients suffered from postoperative shivering after DEX (10%) than after MID (52%). We conclude that DEX has many desirable effects, but side effects such as bradycardia may limit its routine use in ASA physical status I-II patients.

Comparison of eltanolone and propofol in anesthesia for termination of pregnancy.

A randomized study was designed to compare eltanolone (pregnanolone) and propofol anesthesia in 60 unpremedicated women undergoing outpatient termination of pregnancy. The initial doses for induction of anesthesia were 0.8 mg/kg for eltanolone and 2 mg/kg for propofol followed by an additional 25% increment if necessary. The doses required for successful induction were 0.82 +/- 0.06 and 2.1 +/- 0.3 (mean +/- SD) mg/kg for eltanolone and propofol, respectively. Discomfort or pain on injection occurred in none of the patients given eltanolone and in 20% of those receiving propofol (P < 0.05). To maintain satisfactory anesthesia, 29% of the patients given eltanolone and 70% of the patients given propofol needed extra bolus doses of the study drug (P < 0.01). Excitation (twitching of extremities or slight hypertonus) occurred in 29% of the patients in the eltanolone group compared to none in the propofol group (P < 0.05). Both clinical (opening eyes, orientation, walking, tolerating oral fluids, voiding) and psychomotor recovery (Maddox Wing test and Digit Symbol Substitution test) returned to baseline more slowly after eltanolone than after propofol. Overall home readiness was achieved later in the eltanolone group [median 57 min (range 41-190 min)] compared to the propofol [37 (32-100 min)] group. We conclude that recovery from anesthesia is more rapid from propofol as compared to eltanolone anesthesia.

Comparison of two fentanyl doses to improve epidural anaesthesia with 0.5% bupivacaine for caesarean section.

Ninety women undergoing elective caesarean section under epidural anaesthesia were double blindly randomised into three groups to receive either 2 ml of saline or 50 or 100 micrograms of fentanyl in 2 ml volume added to 0.5% bupivacaine. Both doses of fentanyl intensified the epidural anaesthesia and reduced patient discomfort during the operation. In both fentanyl groups the epidural blockade more often reached the 5th thoracic segment (P = 0.0258), the patients had significantly less pain (P = 0.0256), needed less intravenous diazepam medication during the operation (P = 0.0005) and the operating conditions were were better when compared to the saline group (P = 0.0416). There was no difference between the groups in the condition of the neonates as assessed by the Apgar score and cord blood pH. The postoperative time until treatment for pain was requested by the patients was more than 1 h longer in the fentanyl groups, but there was no difference in the total amount of postoperative analgesics needed during the first 24 h when compared to the saline group. Mild pruritus not requiring treatment was more common in fentanyl groups than in the saline group (P = 0.0187). The results suggest that 50 micrograms of fentanyl added to 0.5% bupivacaine increases patient comfort and improves the quality of epidural anaesthesia for caesarean section, and that adding 100 micrograms does not give further advantage.

Treatment of bupivacaine-induced cardiac arrhythmias in hypoxic and hypercarbic pigs with amiodarone or bretylium.

The treatment of bupivacaine-induced cardiovascular toxicity with amiodarone or bretylium was studied using anesthetized pigs (n = 30). The pigs were given ketamine, glycopyrrolate, enflurane, and pancuronium and made hypoxic (FiO2, 12%; N2O, 88%) and hypercarbic (end-tidal CO2, 7.3-8.0%) before the administration of bupivacaine (4 mg/kg i.v.). The animals were then treated, in a randomized and double-blind fashion, with either amiodarone (n = 10) 10 mg/kg in 5% dextrose solution i.v. followed by a constant infusion of 15 mg/hour, bretylium (n = 10) 20 mg/kg in 5% dextrose solution i.v. followed by a constant infusion of 90 mg/hour, or 5% dextrose solution (n = 10). The animals were resuscitated, if required. After 30 minutes of recovery, the animals that survived were made hypoxic and hypercarbic again and given a second injection of bupivacaine (2 mg/kg IV). Bupivacaine caused marked changes in the ECG; polymorphic ventricular tachycardia (20 cases) or severe bradycardia that resulted in asystole (10 cases). Nine animals out of ten treated with amiodarone survived (stable sinus rhythm, arterial blood pressure at near control level, normocarbia), whereas six animals in the bretylium group and four in the control group died. The difference in survival between the groups was not, however, statistically significant.

Topical anaesthesia of gingival mucosa by 5% eutectic mixture of lignocaine and prilocaine or by 10% lignocaine spray.

The analgesic effect of topical application of local anaesthetics on the gingival mucosa and the absorption of the local anaesthetics into the blood were investigated in healthy volunteers by using a 5% eutectic mixture of the local anaesthetics lignocaine (100 mg) and prilocaine (100 mg) plus emulsifier (EMLA) or 10% lignocaine (200 mg) spray (Xylocain). The pain threshold on labial gingiva was measured by using the stimulator of an EMG-apparatus and a pair of stimulating electrodes, specially constructed for this purpose. There were no differences between the two methods in producing analgesia which was at its maximum in 13 to 14 minutes, on average. Sensation of the gingiva (pain thresholds), had usually returned to normal within 30 minutes. In the dosages used, the absorption of the local anaesthetics was more rapid after the mixture application than after spray application. No toxic reactions occurred.

Continuous interscalene brachial plexus block during and after shoulder surgery.

Continuous interscalene brachial plexus block with a single dose of 0.75% bupivacaine (150-210 mg) with adrenaline, continued with an infusion of plain 0.25% bupivacaine 0.25 mg/kg/h, was performed on 20 patients to provide analgesia during shoulder surgery and in the postoperative period. The control group included 20 patients who were given general anaesthesia for surgery after starting a continuous interscalene brachial plexus block; test dose of 0.75% bupivacaine (22.5 mg) with adrenaline, continued with an infusion of 0.25% bupivacaine 0.25 mg/kg/h. Surgery was performed successfully under regional anaesthesia in 16/20 patients; 4/16 were given one dose of fentanyl during the surgery, and diazepam or midazolam as supplementary sedation were given in 13/16 cases. For postoperative analgesia 35/40 patients had a fully functioning catheter for 20-26 hours and the need for oxycodone i.m. during that time was 1.5 +/- 0.4 doses after regional anaesthesia (n = 14) and 1.8 +/- 0.4 doses after general anaesthesia (n = 18). There was a statistically significant difference in the mean plasma bupivacaine concentrations between the groups, concentrations in the regional anaesthesia group being higher at 5, 30, 60 min and 3 h (maximum 2.3 micrograms/ml at 60 min), but there was no difference between the values at 24 h. One infusion of local anaesthetic was discontinued because of probable treatment-related side-effects (breathing difficulties, nausea). Mild local anaesthetic toxicity (dizziness, tinnitus) was noticed in four patients.

Cubital nerve block vs haematoma block for the manipulation of Colles' fracture.

Blocking efficacy and acute toxicity of prilocaine (15 ml of 10 mg/ml prilocaine) was examined in 35 (16 + 19) patients by using blocks of the radial, ulnar and median nerves in the elbow region (Group 1), or the haematoma block method (Group 2) for the manipulation of Colles' fracture. In Group 1 vs Group 2, the reposition was painless in 44% (7/16) vs 68% (13/19), moderate pain occurred in 38% (6/16) vs 21% (4/19), and severe pain in 19% (3/16) vs 11% (2/19). At 15 minutes there was a higher degree of block, on average, at the median and ulnar nerve innervation areas in Group 1. Complete motor block at peripheral innervation regions of all three nerves was achieved in only one patient in Group 1 and in no case in Group 2. Despite this, the surgeons assessed the relaxation at the wrist satisfactory for reposition of the fracture in all but one patient (Group 2). The highest individual prilocaine plasma concentration in Group 1 was 0.68 microgram/ml at ten minutes, whereas the highest individual value in Group 2 was 0.77 microgram/ml at ten minutes. Systemic toxicity from the local anaesthetic did not occur.

Interaction of lidocaine and hypothermia in Bier blocks in volunteers.

The present investigation was designed to study the interaction of temperature, lidocaine, and ischemia during intravenous regional anesthesia (IVRA) of the arm. Five volunteers were studied during exposure of one of their arms to four different experimental conditions: hypothermia and ischemia; hypothermia, ischemia, and lidocaine; normothermia and ischemia; normothermia, ischemia, and lidocaine. Each subject was tested on four different occasions with only one test condition imposed per occasion and with 3 or more days between experiments. Somatosensory evoked responses (SERs) and muscle responses to ulnar nerve stimulation were measured, and sensory testing was done to determine whether the neural effects of the particular treatments differed. Anesthesia developed sooner and was more extensive when local anesthetic was injected. A 5-10 degrees C decrease in tissue temperature did not accentuate the anesthetic effects of lidocaine as determined by time to loss of pinprick and touch sensation. With ischemia alone, anesthesia of the finger tips with preservation of sensation on the arm was observed in all subjects 20 min after tourniquet inflation. Anesthesia at all cutaneous test sites was achieved in 7 of 10 lidocaine experiments; no systematic order of sensory loss, such as progression from distal to proximal sites, was observed. Decrease in limb temperature slowed the development of lidocaine effects on evoked responses and recovery from the effect. Under conditions of ischemia, deterioration of sensation generally began earlier under cold rather than warm conditions. Primary differences between changes in the SERs and muscle responses under condition of ischemia versus ischemia and lidocaine were the rate and magnitude of change of potential latency and amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous regional anaesthesia of the arm. Effect of the technique of exsanguination on the quality of anaesthesia and prilocaine plasma concentrations.

The effects of different techniques of exsanguination of the upper arm during intravenous regional anaesthesia on prilocaine plasma concentrations, quality of anaesthesia, toxic symptoms after deflation of the tourniquet and injection pressure of the anaesthetic were studied in 10 healthy male volunteers. The nondominant arm was exsanguinated using either Esmarch's bandage or elevation of the arm for 2 minutes plus arterial occlusion by compression of the brachial artery. The injection pressure after the prilocaine dose (3 mg/kg) was significantly higher in the elevation group (maximally 98 mmHg). There were no statistically significant differences in the onset of, or recovery from, anaesthesia between the groups. Various mild toxic symptoms were experienced in the central nervous system after deflation of the tourniquet. However, there was no correlation between the two techniques and the degree of severity of the toxic symptoms. The highest single venous plasma concentration (total) of prilocaine was 2.3 micrograms/ml measured from the contralateral cubital vein (elevation group, 2 minutes). The differences in prilocaine concentrations between the groups were not statistically significant.

Continuous interscalene brachial plexus block: clinical efficacy, technical problems and bupivacaine plasma concentrations.

Continuous interscalene brachial plexus block with a single dose of 0.5% bupivacaine 1.25 mg/kg, continued with an infusion of 0.25% bupivacaine 0.25 mg/kg/h, was performed on 24 patients to provide analgesia during shoulder surgery and in the postoperative period. The drugs for general anaesthesia included glycopyrrolate, thiopentone, vecuronium, enflurane and N2O/O2. All patients had signs of regional analgesia 30 min after the block without haemodynamic problems. The infusion of local anaesthetic was interrupted in six patients because of a failure in catheter function. Of the remaining 18 patients, nine needed no complementary analgesics and nine patients received, on average, 1.6 doses of oxycodone (0.15 mg/kg/dose) during a 24-h period. Displacement of the interscalene catheters could be prevented by a fixation suture to the skin. Two patients noted a metallic taste during the bupivacaine infusion. The most common complaints were numbness of the hand (n = 15) and hoarseness (n = 5). The mean (+/- s.e.mean) plasma concentrations of bupivacaine at 30, 60, 180 min and 24 h were 0.68 +/- 0.06, 0.62 +/- 0.05, 0.52 +/- 0.04 and 0.76 +/- 0.01 micrograms/ml, respectively. During the 24-h period, the alpha 1-acid glycoprotein (AAG) concentration (mean +/- s.e.mean) in plasma rose from 0.41 +/- 0.04 g/l to 0.54 +/- 0.04 g/l (P less than 0.001). The concentration of free bupivacaine was below detectable levels (less than 0.01 micrograms/ml) after the 24-h infusion. The rise in AAG probably increases binding of bupivacaine to plasma proteins, diminishing the risk of systemic toxicity.

Influence of premedication on lignocaine-induced acute toxicity and plasma concentrations of lignocaine.

The effects were studied, in eight healthy volunteers, of premedication with diazepam 0.14 mg kg-1 by mouth or hyoscine 6 micrograms kg-1 + morphine 0.2 mg kg-1 i.m., or no premedication, on toxic symptoms and plasma concentrations after rapid i.v. injection of lignocaine 1 mg kg-1. The alpha 1-acid glycoprotein (AAG) and albumin plasma protein fractions were assessed. A variety of mild central nervous system (CNS) symptoms were experienced after the bolus of lignocaine. However, there was no correlation between premedication and degree of severity or number of CNS symptoms. The highest single arterial plasma concentration of lignocaine was 11.0 micrograms ml-1, 1 min after injection. There was no correlation between plasma concentration of lignocaine and occurrence of CNS symptoms. Furthermore, there was no correlation between AAG or albumin plasma concentrations and lignocaine plasma concentrations.