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Biomedical subjects

J M Bernard

Publications and source records attributed to J M Bernard.

At least 19 recordsLinked to original sources
PubMed1999

Adding clonidine to lidocaine for intravenous regional anesthesia prevents tourniquet pain.

UNLABELLED: Tourniquet pain often complicates the use of the pneumatic tourniquet during surgical procedures performed under IV regional anesthesia. Clonidine-containing local anesthetic solutions have better analgesic properties than plain solutions when used for spinal, epidural, or peripheral blocks. We tested the hypothesis that the addition of clonidine may improve the quality of IV regional anesthesia, especially tourniquet tolerance. Forty patients were allocated randomly in a double-blinded, randomized study to receive 40 mL of 0.5% lidocaine and either 1 mL of isotonic saline or clonidine (150 microg). A double-cuffed tourniquet was kept inflated until patients complained of pain, leading to release of the distal cuff. Pain at the tourniquet site, at the surgical site, and in the distal part of the arm was rated on a visual analog scale (VAS) and a verbal rating scale (VRS) every 15 min during tourniquet placement and every 15 min for 1 h after tourniquet deflation. Motor blockade, sedation, arterial pressure, and heart rate were also recorded. VAS and VRS scores were significantly lower in the clonidine group 30 and 45 min after tourniquet inflation. The tolerance for the distal tourniquet was also significantly longer in the clonidine group (median [range]: 22 [10-40] vs 10 [5-20] min; P < 0.05); motor blockade was comparable between the two groups. Pain was not different in the two groups after tourniquet release. The clonidine group experienced a higher degree of sedation. We conclude that clonidine improves tourniquet tolerance when added to a local anesthetic solution. IMPLICATIONS: A 150-microg dose of clonidine added to lidocaine improved tourniquet tolerance during IV regional anesthesia.

Adrenergic alpha-Agonists↗
PubMed1999

The effects of desflurane on the nervous system: from spinal cord to muscles.

UNLABELLED: Monitoring of motor pathways via muscle contraction recording is sensitive to anesthetics, particularly volatile anesthetics. However, the specific action sites of these anesthetics on the spinal cord and the peripheral nervous system are not well known in humans. Therefore, we studied proximal and distal motor and sensory nerve conduction, neuromuscular junction transmission, and spinal cord excitability (H/M amplitude ratio and F-wave amplitude and persistency) using standard neurophysiological techniques in 10 patients who underwent orthopedic surgery. Muscle potentials evoked by spinal cord stimulation were recorded in five additional patients. Desflurane was introduced to achieve end-tidal concentration of 3.7% and 7.4%, in 50% O2/N2O and in 100% O2. Measurements were obtained before desflurane administration and 20 min after obtaining a stable level of each concentration. Peripheral nerve conduction and neuromuscular function were not significantly affected by desflurane. However, spinal cord excitability was significantly decreased by desflurane administration (H/M ratio 37% +/- 9%, 12% +/- 5%, 7% +/- 4% at desflurane concentration 0.0%, 3.7%, and 7.4% in 100% O2, respectively). Muscle potentials evoked by spinal cord stimulation were abolished by desflurane. These data rule out the possibility that desflurane specifically alters peripheral nerve conduction or synapse transmission at the neuromuscular junction. They demonstrate that desflurane acts preferentially at the level of the spinal motoneuron. IMPLICATIONS: We used neurophysiological techniques to assess the effects of desflurane on spinal cord conduction and excitability, motor and sensory peripheral nerve conduction, and neuromuscular transmission. Our data demonstrate that desflurane acts preferentially at the level of the spinal motoneuron, providing useful information for neurophysiological monitoring and immobilization during surgery and for minimum alveolar anesthetic concentration definition.

Action Potentials↗
PubMed1998

Usefulness of neurogenic motor evoked potentials for spinal cord monitoring: findings in 112 consecutive patients undergoing surgery for spinal deformity.

Neurogenic motor evoked potential (NMEP) monitoring, which basically represents a monitoring of both motor and somatosensory tracts, has been proposed as a warning system in preventing neural damage during spinal surgery. The aim of this study was to report our clinical experience in 112 consecutive patients undergoing surgery for spinal deformity, and to emphasize the interest of NMEP monitoring. NMEPs were elicited in each patient by electrical stimulation of the spinal cord via needle electrodes placed by the surgeon in the rostral part of the surgical field, and recorded from the right and left sciatic nerves. Concomitantly, somatosensory evoked potentials (SSEPs) were obtained using a standard method. No false-negative cases of intra-operative spinal cord damage were reported. In 3 patients, both NMEPs and SSEPs suddenly disappeared during specific surgical manipulations of the vertebral implants. In these patients, the level of the lesion was easily recognized by moving the stimulating electrodes of NMEPs along the spinal cord, allowing the surgeon to perform laminectomy at the appropriate vertebral level. Spinal cord decompression was a success in two patients, the last unfortunately being paraplegic. Two additional patients exhibited transient reduction in NMEP amplitude at the insertion of a rod while SSEPs did not change significantly. In these two cases, the surgeon modified his procedure according to the NMEP changes, possibly avoiding a neurological complication. Each time evoked potentials were significantly altered, significant information was more rapidly acquired with NMEPs than with SSEPs. These results suggest that NMEPs can be used as primary choice for detecting impeding lesion of the spinal cord during critical steps of spinal surgery.

Adolescent↗
PubMed1998

Clonidine does not impair redistribution hypothermia after the induction of anesthesia.

UNLABELLED: Clonidine is commonly given for premedication, and it impairs normal thermoregulatory responses to warm and cold stimuli while depressing sympathetic tone. We studied the effect of premedication by clonidine on redistribution hypothermia induced by the induction of anesthesia. Sixteen ASA physical status I or II patients were randomly assigned to receive either clonidine 150 micrograms or a placebo. Anesthesia was induced 45 min later by thiopental, fentanyl, and vecuronium i.v. and was maintained by the administration of 0.6% isoflurane. We monitored central core (tympanic) temperature and skin surface temperatures at the forearm and the fingertip during the 2 h after the induction of anesthesia before surgery. We estimated skin blood flow at the level of the forearm by using laser Doppler during the same period. The core temperature decreased comparably in the two groups of patients, from 37.1 +/- 0.2 degrees C to 35.3 +/- 0.4 degrees C and from 37.1 +/- 0.2 degrees C to 35.5 +/- 0.3 degrees C in the clonidine and placebo groups, respectively. The forearm-fingertip surface temperature gradient decreased similarly in the two groups. There was no evidence of cutaneous vasoconstriction. The laser Doppler index at the fingertip increased similarly in the two groups, as did the forearm-fingertip temperature gradient. We conclude that premedication with clonidine does not significantly impair the profile of central hypothermia induced by heat redistribution after the induction of anesthesia. IMPLICATIONS: The induction of general anesthesia is associated with redistribution hypothermia. This study shows that premedication with oral clonidine does not worsen the decrease in core temperature resulting from general anesthesia.

Adrenergic alpha-Agonists↗
PubMed1997

Characteristics of successful claims for payment by the Florida Neurologic Injury Compensation Association Fund.

OBJECTIVES: Our purpose was to examine the obstetric characteristics of claims paid by the State of Florida after the birth of a neurologically impaired child. STUDY DESIGN: The Florida Birth Related Neurological Injury Compensation plan is a no-fault alternative to litigation for compensation after a catastrophic neurologic birth injury. The plan has specific criteria for inclusion. We retrospectively analyzed claims for compensation that were accepted and paid (n = 64) after a birth-related neurologic injury. Simple description statistics were compiled for the relative frequencies of various obstetric correlates found in successful claims for payment. RESULTS: Seventy percent of infants (45) were delivered by cesarean section and 15 of 19 vaginal deliveries (79%) were operative (forceps or vacuum), yielding a 94% operative delivery rate. A persistent nonreassuring fetal heart rate tracing was seen before delivery in all cases. The 5-minute Apgar score was < or = 6 in 91% of deliveries and the 10-minute Apgar score was < 6 in 86% of deliveries. When first examined in the labor and delivery suite, 17 women had a nonreassuring fetal heart rate, and a nonreassuring tracing developed in labor in 47. Nine attempts at vaginal birth after a cesarean section led to a uterine rupture. Seven of these deliveries were either inductions or augmentations against an unfavorable cervix. Forty-five percent (27) of deliveries were associated with meconium-stained amniotic fluid, including 17 infants with meconium aspiration syndrome. There were three shoulder dystocias and four infants with group B streptococcal sepsis. In eight cases (12.5%), there appeared to be a breach of the published standard of care, which contributed to the poor outcome. CONCLUSION: Most of these cases should not have been eligible for compensation in a traditional tort-based system because the applicable standard of care was not breached. Meeting the published standard for perinatal care failed to prevent these devastating neurologic injuries. Obviously, not all intrapartum injuries can be prevented; however, if we are to prevent similar injuries in the future, we will need to examine the clinical management in these or similar case for clues to develop novel strategies to respond to intrapartum emergencies. An unexpected finding was the frequency of catastrophic birth injuries after an attempted vaginal birth after cesarean section with the predominance of these deliveries associated with oxytocin stimulation against an unripe cervix. It is apparent that the push to lower cesarean section rates is not without some risk.

Birth Injuries↗
PubMed1997

Length representation in normal and neglect subjects with opposite reading habits studied through a line extension task.

In the first part of this paper, 45 French (left-to-right readers) and 30 Israeli (right-to-left readers) normal dextrals were given half a line and requested to construct the missing other with the same length (either the left one or the right one). Using this line extension task, a significant effect of reading habits on the performance was found, with no significant bias for Israeli subjects, and a significant underconstruction when building the left half from the right one for French subjects. In the second part, two patients with opposite reading habits (one French, one Israeli) suffering from left unilateral neglect were submitted to the same protocol. Both patients were found to under-construct the right half of the line from the left given half, and to over-construct the left half from the right given one, hence reproducing the well-known line bisection bias. Results are discussed with regard to enhancement and activation hypotheses, and current theories of the neglect syndrome.

Adult↗
PubMed1997

A survey of factors determining the utilization of autologous blood donation in hip replacement surgery.

A prospective survey was conducted among anaesthesiologists to determine their criteria for excluding a patient from autologous blood donation prior to total hip prosthesis. Information on patients operated on during a 5-week period was obtained using a questionnaire, consisting of a set of possible responses to simple questions, matched with some parametric values. Sixty-eight of the 99 patients included in the survey underwent surgery without donation. Age was the main cause for exclusion (34%). The age of patients excluded because of their age alone was 75 +/- 11 years (standard deviation). The age of patients excluded from donation and who did not subsequently receive homologous blood was comparable with that of patients not autotransfused but who received homologous blood (68 +/- 4 vs. 69 +/- 6 years, respectively). Post-operative haemoglobin concentrations were similar whether transfusion was performed or not, and regardless of the origin of blood given. Since age is no longer taken into consideration at the time of transfusion, it is likely that exclusion of a patient from autologous blood donation because of age is an arbitrary choice.

Age Factors↗
PubMed1997

Prolonged peribulbar anaesthesia with indwelling catheter: a preliminary report of 217 cases.

We report a technique to prolong peribulbar anaesthesia by repetitive injections of lignocaine through a catheter in the inferotemporal peribulbar space during surgery anticipated to exceed 60 min. After peribulbar anaesthesia by standard percutaneous approach with the eye looking straight, a 19-gauge Tuohy needle was inserted backwards in the sagittal plane and parallel to the 5 degrees slope of the orbit floor, to a distance of less than 3 cm, at the junction of the middle and lateral third of the lower orbital rim. A 23-gauge smooth catheter was advanced up to the tip of the needle which was withdrawn, keeping less than 3 cm of catheter in the inferotemporal compartment. A catheter was inserted in 217 consecutive patients undergoing vitrectomy, retinal detachment and retinal peeling. There were no technical difficulties. Neither additional sedation nor general anaesthesia was required during surgery, but less than 50% of patients requested lignocaine injections to supplement anaesthesia. Catheter insertion into the peribulbar space may represent a potential technique to perform a greater variety of ophthalmic surgery with regional anaesthesia. Indications should be limited to the longest procedures.

Aged↗
PubMed1997

Dose-range effects of clonidine added to lidocaine for brachial plexus block.

BACKGROUND: Although addition of clonidine to local anesthetics can prolong pain relief after peripheral nerve block, a dose-range effect has not been determined. METHODS: Fifty-six outpatients undergoing carpal tunnel release were randomly assigned to receive in a double-blind fashion 45 ml of a mixture containing either 400 mg lidocaine plus saline or 400 mg lidocaine plus 30, 90 or 300 microg clonidine for axillary nerve block. In each group (n = 14), blocks were evaluated at regular time intervals to determine sensory and motor functions in the five nerve regions of the hand and forearm. Also, adequacy of the block for surgery, postoperative pain intensity, and side effects were evaluated. RESULTS: Compared with saline, each dose of clonidine reduced the onset time of sensory block and extended the field of adequate anesthesia. Ten minutes after injection, 30 microg clonidine was more effective than 90 microg clonidine in producing sensory blockade. Sedation occurred with clonidine 30 and 300 microg. Clonidine reduced the use of supplementary intravenous anesthetic agents for surgery and produced dose-dependent prolongation of analgesia, reaching a mean 770 min (range, 190-1440 min) for the largest dose. Clonidine also produced a dose-dependent decrease in systolic arterial pressure of up to -22.5% (range, -6.0 29.9%) of baseline. With clonidine, 300 microg, three patients had mean arterial pressure of <55 mmHg; four patients had episodes of arterial oxyhemoglobin saturation of <90%, and two others were not discharged because of hypotension. CONCLUSION: This study suggests that a small dose of clonidine enhances the quality of the peripheral blocks from lidocaine and limits the classical alpha2-agonist side effects to sedation.

Adult↗
PubMed1996

Effects of isoflurane and desflurane on neurogenic motor- and somatosensory-evoked potential monitoring for scoliosis surgery.

BACKGROUND: Most techniques used to monitor spinal cord tracts are sensitive to the effects of anesthesia, particularly to volatile anesthetic agents. The aim of this prospective study was to show that evoked potentials recorded from the peripheral nerves after spinal cord stimulation, so-called neurogenic motor evoked potentials, are resistant to clinical concentrations of isoflurane or desflurane, compared with somatosensory-evoked potentials. METHODS: Twenty-three patients were studied during surgery to correct scoliosis. The background anesthetic consisted of a continuous infusion of propofol. Isoflurane (n = 12) or desflurane (n = 11) were then introduced to achieve 0.5 and 1.0 end-tidal minimum alveolar concentrations (MAC), both in 50% oxygen-nitrous oxide and in 100% oxygen. Somatosensory-evoked potentials were elicited and recorded using a standard method, defining cortical P40 and subcortical P29. Neurogenic motor-evoked potentials were elicited by electric stimulation of the spinal cord via needle electrodes placed by the surgeon in the rostral part of the surgical field. Responses were recorded from needle electrodes inserted in the right and left popliteal spaces close to the sciatic nerve. Stimulus intensity was adjusted to produce a supramaximal response; that is, an unchanged response in amplitude with subsequent increases in stimulus intensity. Measurements were obtained before introducing volatile agents and 20 min after obtaining a stable level of each concentration. RESULTS: Isoflurane and desflurane in both 50% oxygen-nitrous oxide and 100% oxygen were associated with a significant decrease in the amplitude and an increase in the latency of the cortical P40, whereas subcortical P29 latency did not vary significantly. Typical neurogenic motor-evoked potentials were obtained in all patients without volatile anesthetic agents, consisting of a biphasic wave, occurring 15 to 18 ms after stimulation, with an amplitude ranging from 1.3 to 4.1 microV. Latency or peak-to-peak amplitude of this wave was not significantly altered with isoflurane and desflurane, either in the presence or in the absence of nitrous oxide. CONCLUSIONS: Compared with cortical somatosensory-evoked potentials, neurogenic motor-evoked potential signals are well preserved in patients undergoing surgery to correct scoliosis under general anesthesia supplemented with isoflurane or desflurane in concentrations as great as 1 MAC.

Adolescent↗
PubMed1996

Patient-controlled premedication by i.v. midazolam for ambulatory surgery.

Applying the principle and equipment of patient-controlled analgesia, this double-blind randomised study was designed to determine the premedication dose of midazolam and to provide information about the need for preoperative anxiety control. The effects of patient-controlled premedication by i.v. midazolam were compared to those of a 1-hour i.v. infusion of a fixed dose of 4 mg. Two groups of 25 patients were studied prior to ambulatory surgery. Using a visual analogue scale graded from 0 (no anxiety) to 100, anxiety and short-term memory as well as vital signs, vigilance, cognition and orientation were assessed before premedication and then every 20 min until admission to the operating room. In both groups, 40% of the patients were free of anxiety before premedication. Sixty-four percent of patients in the self-pre-medicated group never used the pump. The dose of midazolam was only 0.7 0.2 mg (mean SD) in this group taken as a whole, 0.7, 1.1 mg (mean SD) in the 8 patients who had an anxiety score at least equal to 50 before premedication, and 1.7 0.3 mg (mean SD) in the 9 patients who chose to push the button of the patient-controlled device. Anxiety and short-term memory scores decreased significantly and similarly in the self-premedicated group and in the fixed-dose group. For similar intraoperative anaesthetic requirements, time from the end of anaesthesia for determining whether a patient was ready for admission to the postrecovery lounge was shorter in the self-premedicated group (26 +/- 8 min vs 32 +/- 8 min; mean +/- SD. Reduced doses of midazolam self-administered via a patient-controlled device can result in a relaxed preoperative period and amnesia in ambulatory surgery patients. However, the level of anxiety before premedication was low, which calls into question the legitimacy of the patient-controlled premedication in this kind of population. The expense of the pump was not justified by the small number of patients using it, probably because they were worried by the technical nature and the invasiveness of this technique.

Adult↗
PubMed1995

Motor and blood pressure effects of epidural sustained-release bupivacaine from polymer microspheres: a dose-response study in rabbits.

The incorporation of local anesthetics into injectable polymer microspheres can be useful in providing prolonged regional effects. This randomized study was designed to compare the effects of bupivacaine and bupivacaine-loaded microspheres on the time course of motor block in rabbits injected epidurally. Bupivacaine-loaded microspheres and drug-free microspheres 1-10 microns in size were devised from poly-d,l-lactic acid by using a solvent evaporation/extraction method. The effects of bupivacaine and of similar amounts of bupivacaine-loaded microspheres were studied in 26 rabbits as follows: 0.9% sodium chloride, followed by drug-free microspheres, then 1.25 mg of bupivacaine and 1.25 mg of bupivacaine-loaded microspheres (Group I; n = 8); 2.5 mg of bupivacaine, then 2.5 mg of bupivacaine-loaded microspheres (Group II; n = 8); and 5 mg of bupivacaine and 5 mg of bupivacaine-loaded microspheres (Group III; n = 10). Motor block was evaluated blindly by observation of walking disturbances, using a scale from 0 (free movements) to 3 (total limb paralysis). A period of 3 days elapsed between each injection. No limitation on movements was observed after 0.9% sodium chloride and drug-free microsphere injection. With 5 mg, both bupivacaine solutions provided complete motor block which was significantly more prolonged (+244% +/- 129%, mean +/- SD) with bupivacaine-loaded microspheres than bupivacaine. With 2.5 and 1.25 mg, block intensity was less marked, and block duration was shorter after administration of bupivacaine-loaded microspheres than after bupivacaine. We concluded that blocks resulting from bupivacaine-loaded microspheres are highly influenced by the amount of drug initially released by the polymer.

Animals↗
PubMed1995

Comparison of intravenous and epidural clonidine for postoperative patient-controlled analgesia.

Both epidural and intravenous clonidine are used to provide postoperative analgesia, but in predetermined doses. This double-blind randomized study was designed to 1) determine the clonidine dose inducing pain relief after major orthopedic surgery, when controlled by patient, either intravenously or epidurally; and 2) assess whether these two administration routes are clinically equivalent. At the first complaint of pain after scoliosis correction, patients received an initial dose of 8 micrograms/kg clonidine during 30 min either intravenously (n = 12) or epidurally (n = 12). Then, clonidine was given using a patient-controlled analgesia pump via the corresponding administration route. In both cases, the bolus dose was set at 30 micrograms and the lockout interval at 15 min. Pain (0-100 scale), clonidine requirements, sedation (0-4 scale), and hemodynamics (by fiberoptic pulmonary artery catheter) were measured before and 15, 30, 120, 240, 360, 480, and 600 min after the loading dose was started. Plasma clonidine concentrations and arterial blood gases were determined at the 15th, 30th, 240th, and 480th min. Self-administered and total clonidine doses were larger in the intravenous group than in the epidural group (at 600 min: 372 +/- 110 vs 235 +/- 144 micrograms, and including the initial dose, 814 +/- 114 vs 652 +/- 187 micrograms; mean +/- SD). Clonidine administration resulted in pain relief and sedation in both groups but, for comparable pain relief, sedation scores were lower in the epidural group. No intergroup differences in hemodynamic data were observed, although the decrease in blood pressure occurred earlier in the intravenous group. Plasma clonidine concentrations were higher in the intravenous group than in the epidural group (2.5 +/- 0.6 vs 1.5 +/- 0.5 ng/mL after the initial dose and 2.1 +/- 0.5 vs 1.5 +/- 0.4 ng/mL during self-administration; mean +/- SD). We conclude that analgesia can be achieved postoperatively by both epidural and intravenous clonidine administration. The epidural route is associated with significant reductions in self-administered clonidine dose, and thus in the plasma clonidine concentration, and the level of sedation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Induction of anaesthesia by propofol and hepatic blood flow in the rabbit.

Effects of propofol (12.5 mg kg-1, i.v. bolus injection) or 0.9% sodium chloride on arterial blood pressure, arterial blood gases and hepatic circulation (radio-labelled microsphere technique) were studied in 15 conscious and unpremedicated rabbits. No significant changes were observed after sodium chloride. Propofol resulted in anaesthesia, respiratory depression (-49 +/- 14% decrease in PaO2; mean +/- SD) and hypotension (-49 +/- 13% decrease in mean arterial pressure; mean +/- SD) but no changes in hepatic arterial and portal venous blood flows. We conclude that propofol does not affect the liver circulation despite marked depression of mean arterial pressure and respiration.

Anesthesia↗
PubMed1995

[Influence of post-infarction myocardial revascularization on the prevalence of delayed potentials].

It has been shown that the presence of ventricular late potentials is a predictive factor of ventricular tachycardia and sudden death after myocardial infarction. The value of thrombolysis in the reduction of the prevalence of ventricular late potentials is now well established. However, the effects of other modes of revascularisation is less well known and more controversial. The authors undertook a retrospective study of 139 consecutive patients undergoing coronary angiography after primary myocardial infarction. The presence of ventricular late potentials fulfilling two of the three usual criteria was sought after a revascularisation procedure. The overall prevalence of ventricular late potentials was 30.9%. This was not affected either by the site of infarction of by the single or multiple character of the coronary artery disease. In addition, the left ventricular ejection fraction was not significantly different in patients with positive ventricular late potentials compared with the others. On the other hand, revascularisation of the culprit lesion responsible for the infarction was strongly correlated with a lower incidence of ventricular late potentials (p < 10 (-5)). In particular, the different incidence of positive late potentials between the dilated (9.3%) and non-dilated group (49.2%) was statistically significant (p < 10 (-6)) without any correlation to the single or multiple character of the coronary disease. The authors discuss the different reports in the literature concerning the effects of angioplasty and coronary bypass surgery on the incidence of ventricular late potentials. Conclusion; the review of the literature shows that thrombolysis significantly reduces the incidence of late potentials after myocardial infarction and the present study suggests that angioplasty and coronary bypass surgery may also be effective.

Arrhythmias, Cardiac↗