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Biomedical subjects

M Chauvin

Publications and source records attributed to M Chauvin.

At least 109 records · Page 6Linked to original sources

[Arrhythmias in chronic heart failure. Prognostic significance and treatment].

Almost 50 percent of patients with chronic heart failure die of sudden death often due to arrhythmia. In these patients the prognosis is related to the severity of myocardial lesions and also, probably, to the presence of ventricular arrhythmias. The potential severity of which can be assessed by various methods, including ECG, Holter monitoring, late potentials study and programmed ventricular stimulation tests. The first therapeutic measure to improve the prognosis of heart failure is to improve the myocardial function by prescribing converting enzyme inhibitors. The second measure consists of acting on potentially dangerous ventricular arrhythmias with few or no symptoms. Among antiarrhythmic agents, only beta-blockers and amiodarone seem to be valuable.

Adrenergic beta-Antagonists↗

[Spinal anesthesia with bupivacaine without glucose in the elderly: effect of concentration and volume on the hemodynamic profile].

This study aimed to compare the haemodynamic effects of two different glucose-free bupivacaine solutions is thirty patients aged more than 70 years (mean age 82 years) undergoing hip surgery under spinal anaesthesia. They were randomly assigned to two groups, group A to receive 2.5 ml of a 0.5% bupivacaine solution, and group B 10 ml of a 0.125% solution in normal saline. All the patients were therefore given the same dose of bupivacaine, 12.5 mg. Lorazepam (1 mg orally) was administered to all for premedication two hours beforehand. Those patients taking antihypertensive agents were given their last dose on the eve of surgery. Lactated Ringer's solution (500 ml) was infused to all before the spinal puncture. Systolic (Pasys), mean and diastolic arterial pressures, and heart rate, were recorded every minute before volume loading, and for 30 minutes after the start of the spinal anaesthesia. Ephedrine (3 mg every two minutes if required) was given whenever Pasys decreased by more than 30% of the pre-induction value. The upper level of sensory blockade was assessed by the pin-prick test, and the quality of motor blockade with the Bromage scale. The cephalad spread of the solutions was similar, as well as the haemodynamic profile in each group. The total dose of ephedrine required in each group was not significantly different. It may therefore be concluded that, in the elderly, the upper level of, and the haemodynamic changes due to, spinal anaesthesia do not depend on the concentration or the volume of glucose-free bupivacaine solution.

Age Factors↗

Effect of upper abdominal surgery and cirrhosis upon the pharmacokinetics of methohexital.

The pharmacokinetic profile of methohexital was studied in cirrhotic patients (n = 8), patients undergoing upper abdominal surgery (n = 8) and orthopaedic patients under general anaesthesia (n = 8). The total plasma clearance of methohexital was unchanged in cirrhotics: 54 +/- 22 l.h-1 (mean +/- s.d.) as well as in patients undergoing upper abdominal surgery: 60 +/- 14 l.h-1 in comparison to orthopaedic surgery: 70 +/- 24 l.h-1. The central volume and total volume of distribution and the distribution and elimination half-lives were similar between the three groups. Despite its hepatic dependent elimination, methohexital elimination kinetics were unchanged in patients undergoing upper abdominal surgery and in cirrhosis. Owing to the high hepatic extraction ratio of methohexital, its elimination should be influenced by the hepatic blood flow. The unchanged elimination kinetics presently observed in patients with cirrhosis or those undergoing upper abdominal surgery suggest that the hepatic blood flow is less diminished than expected in these patients.

Abdomen↗

[Pharmacology and mechanism of action of opioids administered by the peridural route].

The pharmacokinetics and pharmacodynamics of spinal narcotics are very important to determine dosage and intervals with bolus administration. Among known factors that may effect narcotic activity, lipid solubility seems to be the most important factor determining onset, greater dermatomal spread and longer duration of action than more lipid-soluble narcotics. This dermatomal spread is associated to a delayed respiratory depression which necessitates precautions and surveillance.

Analgesia, Epidural↗

Non-pharmacological therapy of atrial fibrillation and flutter.

Atrial fibrillation and atrial flutter are the most frequent arrhythmias encountered by the cardiologists in an everyday practice. External cardioversion, atrial temporary pacing and/or drugs are commonly and often successfully used in their treatment. The failures of these methods are rare, and for the patients who remain prone to arrhythmias or a recurrence with serious hemodynamic consequences, new therapies are presently under assessment. Electrical internal cardioversion can be performed when a permanent and bad tolerated atrial fibrillation is not managed by an external cardioversion. Elective ablation of a reentrant area will be probably the best solution to treat a recurrent atrial flutter or a junctional tachycardia by intranodal reentry. Finally, a radical solution consists to separate electrically the atria from the ventricles by interrupting totally or partially the A-V conduction. This can be performed by an endocavitary fulguration or an ablation by radiofrequency currents. To avoid recurrences, we usually use a pharmacological therapy. Permanent pacing is an exceptional solution.

Atrial Fibrillation↗

[Fulguration of atrial flutter in man. A pathological case].

A 63 year old man with ischemic heart disease underwent two sessions of catheter ablation in the inferior right atrium for poorly tolerated resistant and recurrent atrial flutter. After endocavitary mapping and comparison with surface recordings of the f waves, a shock of 50 joules was delivered to the zone situated anteriorly to the inferior vena cava, under the orifice of the coronary sinus and behind the tricuspid valve. Early recurrence of the arrhythmia led to a second attempt and another 50 joules shock was administered to the same area. Another short term recurrence led to definitive nodohisian interruption with a 270 joules shock. Thirty months later, the patient died suddenly during an episode of cardiac failure. Macroscopic examination of the right atrium showed a zone of parietal congestion measuring 4 x 3 cm with a very thin, translucid, central zone measuring 3 x 1.5 cm, just anterior to the inferior vena cava in the right atrial free wall. Histological examination of this zone showed an intense, mutilating fibrosis dissociating the muscular fibres, of the pectinate muscle and even replacing the myocardium in certain regions. In the Eustachian valve, there were muscular fibres, probably representing the posterior internodal pathway, which were also fibrosed. These observations suggest that: 1) in view of the extreme thinness of the atrial wall at the site of ablation there is a high risk of perforation even when right endoatrial catheter ablation is performed with low energy shocks; 2) the posterior internodal pathway does not seem to be an essential component for atrial flutter.

Atrial Flutter↗

[Internal electroshock in the treatment of chronic atrial fibrillation resistant to external cardioversion. Initial results apropos of 21 patients].

The authors report their experience involving 21 right endoatrial electroversions aimed at converting chronic atrial fibrillation resistant to external electroversion. All prior precautions were taken to ensure that the shocks were not in contact with an atrial wall nor over the node-His bundle (two dimensional radiological identification, endocavitary recordings). A total of 37 internal electric shocks were administered. Results were: 16 immediate successes out of 21 (72.2 per cent) and 12 short term successes out of 21 (57 per cent). The mean effective energy value was 200 Joules. There were no traumatic complications. The authors conclude that this technique is effective and reliable in the management of atrial fibrillation resistant to external electroversion.

Adult↗

[Role of internal cardioversion in the treatment of permanent atrial fibrillation. Early results apropos of 28 cases].

Internal cardioversion is a new method of treating atrial fibrillation. It consists in delivering an electric shock between an electrode positioned in the right atrium and a dorsal electrode. A quadripolar electrophysiological catheter is used as the proximal electrode, the two distal poles of which are used to locate the His bundle deflection. Care is taken that the electrode used for cardioversion is not in contact with the atrial wall by using biplane fluoroscopy and unipolar endocavitary recordings. Twenty-eight patients (18 men and 10 women) average age 55 years, underwent this treatment for chronic atrial fibrillation resistant to one or two attempts at external cardioversion. Each patient was given one or two shocks (average 1.68) in the same session. There were 22 immediate reversions to sinus rhythm, giving a primary success rate of 78.57%. Four patients relapsed in the 3 days following the procedure, giving a short term success rate of 64.28%. The minimum effective energy would seem to be 200 joules. The only rhythm complications were sinus bradycardia and/or atrioventricular block lasting a few seconds, both countered by prophylactic ventricular pacing : no traumatic complications due to electric shock were observed. The long term results show sinus rhythm maintained in 66.66% of patients at 6 months and more. In conclusion, internal cardioversion is an effective method of treating cardiac arrhythmias resistant to external cardioversion. The procedure would seem to be reliable and relatively atraumatic. The long term results are promising, particularly the stability of sinus rhythm which seems to be longer than after external cardioversion, by they need further confirmation.

Adult↗

[In vitro study of the effects of high frequency electrical current on cardiac pacemakers].

The authors studied the possible consequences of the use of high frequency electrical currents of cardiac pacemaker function. Twenty-five unipolar pacemakers (22 single and 3 double chamber) were tested. They were connected to a pacing catheter, emerged in a saline bath and submitted to a modulated and then unmodulated current of 348 KHz in as many pacing modes as possible for each unit. Three dangerous deprogrammations were observed which could nevertheless be easily corrected. Five pacemakers immediately adopted the reversion mode specified by their manufacturer. The other changes observed only lasted as long as the electric current was applied. The commonest abnormality was a drop in the output voltage proportional to the energy delivered which sometimes led to true inhibition of the pacemaker. Two abnormal rate increases were observed reaching frequencies higher than 250/mn. No particular pacing mode seemed to protect the pacemakers from the effects of high frequency currents.

Cardiac Pacing, Artificial↗

[Carotid surgery under locoregional anesthesia].

Eight-five carotid endarterectomies were performed in 77 patients, under regional anaesthesia using 2 different techniques: cervical epidural anaesthesia (35 cases) and cervical plexus block (50 cases). The patients' mean age was 71 years; 80 per cent had arterial hypertension and 41 per cent coronary disease. Transoperative cerebral ischaemia was detected by a 5-minute carotid clamping test, the occurrence of a neurological event indicating that shunting was required. In 62 patients this test was combined with measurement of carotid back pressure. None of the patients needed general anaesthesia. Intraoperative neurological events occurred more frequently (P less than 0.01) when the carotid back pressure was 25 mmHg or less, and 12 temporary shunts were installed for that reason (14.1 per cent). Three neurological events occurred at the end of endarterectomy: no shunt was installed and complete recovery was observed immediately after declamping. No complications ascribable to the anesthetic techniques were recorded. Mortality was nil, and the only neurological morbidity was a brachio-facial deficit which left few sequelae. The frequency of intra- or postoperative arterial hypertension was similar in both groups. Intraoperative hypotension, frequent under epidural anaesthesia, was observed in only one patient who had brachial plexus block (P less than 0.01). The analgesia obtained was equally good with both anaesthetic techniques, but cervical plexus block anaesthesia is easier to perform, had less haemodynamic repercussions and therefore tends to be preferred to cervical epidural anaesthesia. The lack of mortality, low morbidity and absence of systemic complications in this series despite the high number of patients at risk are in favour of this type of anaesthesia, notably for such patients. Moreover, because vigilance is preserved attention can be paid to the quality rather than the rapidity of endarterectomy, which is the best way of preventing embolism.

Adult↗

[Use of halothane in a semi-closed circuit].

Halothane was administered to 10 ASA or 11 patients undergoing elective peripheral surgery. The vaporizer was included in the delivery gas line of the semiclosed system. Löwe's square root of time model of uptake was used to calculate the required doses of halothane. In order to reach an alveolar concentration corresponding to 1.3 MAC, 0.5 vol % of halothane (1.3 MAC) combined with 60 vol % of nitrous oxide (0.6 MAC) were administered at a fresh of 20 ml.kg-1. The ventilation controlled in order to maintain end-tidal CO2 partial pressure at a 5 vol %. Inspiratory halothane concentration was measured during the inspiratory plateau. The alveolar fraction was defined as being the mean end expiratory concentration. The latter was well above the theoretical values during the first 9 min of anaesthesia (0.85% at the 4 th min). This concentration then decreased progressively, becoming less than the expected value after 15 min (0.4% at the 30 th min). Löwe's model would therefore seem to lead to a gross overestimation of the amount of anaesthetic vapour to be delivered to a patient at the beginning of anaesthesia, and an underestimation thereafter.

Anesthesia, Inhalation↗

Relative potency of vecuronium on the diaphragm and the adductor pollicis.

To quantify the neuromuscular blocking effect of vecuronium on the diaphragm and the adductor pollicis, single twitch stimuli were applied to the phrenic nerves at the neck and the ulnar nerve at the wrist in anaesthetized patients. The evoked responses were measured simultaneously by recording the transdiaphragmatic pressure with a differential pressure transducer and the adductor pollicis strength with a force displacement transducer. Cumulative vecuronium dose-response curves were determined for both muscles in 11 ASA class I adult patients. The mean (SD) doses required to depress adductor pollicis and diaphragm responses to 50% (ED50) were 30 (9) micrograms kg-1 and 37 (12) micrograms kg-1, respectively. Corresponding values for 95% depression of the twitch response (ED95) were 48 (13) micrograms kg-1 and 67 (23) micrograms kg-1 (P less than 0.02), indicating that the diaphragm required approximately 40% more vecuronium for subtotal abolition of the single twitch response.

Arm↗

Atrial refractory periods after atrial premature beats in patients with paroxysmal atrial fibrillation.

To study the effects of an atrial premature beat on atrial refractory periods, we investigated 11 patients (group A) who were the control group, 12 patients suffering from paroxysmal atrial fibrillation (group B), and 10 patients (group C) without arrhythmias but with cardiopathy or cardiomyopathy. At every eighth complex of a constant atrial electrostimulated rhythm a fixed premature extrastimulus was introduced, and effective and functional refractory periods (ERP and FRP) were measured in three different sites of the right atrium, before and after introduction of this extrastimulus. Average ERP and FRP shortened respectively in group A, from 220.28 +/- 25.68 msec and 281.17 +/- 28.15 msec before extrastimulation, to 190.58 +/- 22.74 msec and 245.88 +/- 19.86 msec after; in group B, from 219.44 +/- 27.38 msec and 284 +/- 30.06 msec to 191.66 +/- 28.72 msec and 253.23 +/- 34.01 msec; and in group C from 229.03 +/- 29.65 msec and 289.67 +/- 51.62 msec to 194.19 +/- 24.6 msec and 237.74 +/- 39.59 msec. The average dispersions of ERP and FRP in group A were, respectively: 41.81 +/- 21.36 msec and 36.36 +/- 18.04 msec before extrastimulation, 28.18 +/- 18.14 msec and 35.45 +/- 15.72 msec after. In group B: 26.66 +/- 19.46 msec and 41.66 +/- 16.96 msec versus 45.83 +/- 23.91 msec and 45 +/- 34.77 msec and in group C: 27 +/- 11.59 msec and 45 +/- 29.15 msec versus 29 +/- 18.52 and 27 +/- 18.88.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

A clinical study of the application of endocardial fulguration in the treatment of recurrent atrial flutter.

Endocardial catheter fulguration has been recently proposed for treatment of arrhythmias originating within the right atrium. In this study the authors attempted to use this technique in eight patients with paroxysmal common atrial flutter. Numerous antiarrhythmic agents failed to prevent recurrences of the episodes, which occurred frequently over periods of at least 4 months. In every procedure, we used a 7F quadripolar catheter electrode introduced via the subclavian vein into the lower part of the right atrium. The two distal electrodes allowed the recording of bipolar double potentials where the critical slow pathway of the reentrant circuit was localized. A unipolar electrogram recording by the tip electrode gave us the location of the area to be ablated when this electrogram was in complete concordance with a small step in the descending part of the F waves in II, III and aVF. This step corresponded to the very depolarization of the reentry area. A DC shock of 100 to 120 J was delivered between the tip electrode and a paddle applied to the left chest wall. Sinus rhythm resumed instantaneously. No mechanical or electrical complications were noted. Three patients are free of relapses without antiarrhythmic drugs (follow-up: 14 to 17 months); three others are also free of relapses, but antiarrhythmic agents were required for treatment of other supraventricular dysrhythmias (follow-up: 3 to 17 months); atrial flutter recurred within several days and persisted in spite of two more procedures in two patients. We conclude that endocardial catheter fulguration of paroxysmal and recurrent atrial flutter seems to be effective therapy. Nevertheless, more experience is required in order to confirm these results.

Aged↗

Sufentanil pharmacokinetics in patients with cirrhosis.

The effects of cirrhosis on the elimination kinetics and plasma protein binding of sufentanil were evaluated in 12 anesthetized patients with uncomplicated cirrhosis and these findings were compared with data from age-matched control anesthetized patients with normal hepatic and renal function. Sufentanil 3 micrograms/kg was given intravenously as a bolus injection and venous plasma concentrations were measured at intervals up to 10 hrs. The average (+/- SD) elimination half life was 3.5 +/- 0.9 hrs in controls and did not differ in cirrhotics: 4.1 +/- 0.6 hrs. The plasma clearance did not differ between the two groups: 11.3 +/- 2.5 ml.min-1.kg-1 in controls and 10.8 +/- 4.6 ml.min-1.kg-1 in cirrhotic patients. The sufentanil free fraction was also similar in controls (8.3 +/- 1.5%) and in cirrhotic patients (9.6 +/- 1.8%). These data suggest that sufentanil in a single dose should have a similar duration of action in patients with uncomplicated cirrhosis and in normal patients.

Adult↗