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Biomedical subjects

B Riou

Publications and source records attributed to B Riou.

At least 109 records · Page 6Linked to original sources
PubMed1995

[Combination of propofol-sufentanil on somatosensory evoked potentials in surgery of the spine].

OBJECTIVES: Most anaesthetics depress cortical somatosensory evoked potentials (CSEPs). However, the modification of CSEPs during total intravenous anaesthesia using propofol remaining still unknown, justified this trial. TYPE OF STUDY: Open, prospective, clinical study. METHODS: Nine consecutive patients requiring CSEPs monitoring for spine surgery, were studied. Anaesthesia was induced with propofol (2.5 mg.kg-1 then 10 mg.kg-1.h-1) and sufentanil (0.50 micrograms.kg-1 then 0.25 micrograms.kg-1.h-1). Maximum positive (P40) and negative (N50) waweform latencies, and the peak to peak amplitude of CSEPs (posterior tibial nerve stimulation, cortical recording), were recorded before induction, 30 min, 1 and 2 h after induction, and at the end of surgery. Data are means +/- SD. RESULTS: Duration of anaesthesia was 260 +/- 73 min. Propofol induced significant lengthening of CSEPS (P40: from 37 +/- 10 up to 41 +/- 11 ms; N50: from 45 +/- 11 up to 51 +/- 14 ms), and a significant decrease in amplitude (from 1.9 +/- 0.9 down to 0.8 +/- 0.4 microV), but these changes were stable from 30 min after the induction to the end of spine surgery. A motor response was obtained 29 +/- 14 min after the end of anaesthetic administration. CONCLUSIONS: Total intravenous anaesthesia with propofol and sufentanil induces a small but stable lengthening of CSEPs latency and a stable decrease of its amplitude, which enable an appropriate monitoring of CSEPs during spine surgery.

Adult↗
PubMed1995

Cardiovascular consequences of severe hypophosphataemia in brain-dead patients.

Hypophosphataemia is known to induce reversible myocardial dysfunction, but the incidence of hypophosphataemia and its effect on myocardial function during brain death are unknown. In 90 consecutive brain-dead patients, we measured plasma concentrations of phosphate and left ventricular ejection fraction area (LVEFa), using transoesophageal echocardiography. In 15 severely hypophosphataemic (< 0.40 mmol litre-1), consecutive, brain-dead patients, haemodynamic status, LVEFa, and oxygen delivery and consumption were assessed before and after phosphorus loading (0.30 mmol kg-1). In 10 other brain-dead patients, urine elimination of phosphates was measured. Only 30 (33%) brain-dead patients had normal plasma phosphate concentrations, 22 (24%) had mild hypophosphataemia (0.40-0.80 mmol litre-1) and 38 (42%) had severe hypophosphataemia (< 0.40 mmol litre-1). There were no significant differences in LVEFa between these three groups (mean 53 (SD 16), 55 (12) and 51 (17)%, respectively) and no significant correlation between LVEFa and plasma phosphate concentration (r = 0.04). In 15 severely hypophosphataemic patients, phosphorus loading increased plasma phosphate concentration from 0.30 (0.10) to 1.06 (0.41) mmol litre-1, but did not modify haemodynamic status, LVEFa or oxygen delivery and consumption. In 10 other patients, urine phosphorus elimination was 16.8 (23.3) mmol/24 h while plasma phosphate concentration was at its highest level (0.80 (0.37) mmol litre-1), and only one of these patient had a slightly elevated phosphaturia. In conclusion, hypophosphataemia frequently occurs after brain death but has no significant cardiovascular consequences, suggesting that it is related to intracellular transfer and not phosphorus depletion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Myocardial effects of propofol in hamsters with hypertrophic cardiomyopathy.

BACKGROUND: Propofol is a short-acting intravenous induction agent that induces cardiovascular depression but without significant effect on intrinsic myocardial contractility in various species. However, its effects on diseased myocardium remain unknown. METHODS: The effects of propofol (1, 3, and 10 micrograms.ml-1) on the intrinsic contractility of left ventricular papillary muscles from normal hamsters and those with hypertrophic cardiomyopathy (strain BIO 14.6, aged 6 months) were investigated in vitro (Krebs-Henseleit solution, 29 degrees C, pH 7.40, Ca++ 2.5 mmol.l-1, stimulation frequency 3/min). RESULTS: Cardiac hypertrophy (143 +/- 13%, P < 0.001) was observed in cardiomyopathic hamsters. The contractility of papillary muscles from hamsters with cardiomyopathy was less than that of controls, as shown by the decrease in maximum shortening velocity (-29%, P < 0.03) and active isometric force (-51%, P < 0.001). Propofol did not induce any significant effect on contraction, relaxation, and contraction-relaxation coupling under low and high loads in normal hamsters. The effects of propofol were not significantly different between normal hamsters and those with cardiomyopathy. A slight but significant increase in maximum unloaded shortening velocity was observed in cardiomyopathic hamsters at 3 micrograms.ml-1 (4 +/- 6%, P < 0.05) and 10 micrograms.ml-1 (7 +/- 6%, P < 0.05). CONCLUSIONS: Propofol did not modify intrinsic myocardial contractility in normal hamsters, and no significant differences were observed between normal and cardiomyopathic hamsters. These results may be useful because, unlike propofol, most anesthetics decrease myocardial contractility. Nevertheless, indirect cardiac effects of propofol may be more important than its direct cardiac effects in patients with impaired cardiac function.

Animals↗
PubMed1995

In vitro effects of eltanolone on rat myocardium.

BACKGROUND: Eltanolone is a new short-acting intravenous induction agent. However, its effects on intrinsic myocardial contractility remain unknown. METHODS: The effects of eltanolone and its solvent (soya bean emulsion) on the intrinsic contractility of rat left ventricular papillary muscles were investigated in vitro (Krebs-Henseleit solution, 29 degrees C, pH 7.40, Ca2+ 0.5 mM, stimulation frequency 12 pulses/min). We studied contraction; relaxation; contraction-relaxation coupling under high and low loads; and postrest potentiation. RESULTS: Eltanolone (0.1, 0.3, 1, 3, and 10 micrograms.ml-1) induced no significant inotropic effect, as shown by the lack of changes in maximum unloaded shortening velocity and active isometric force. Eltanolone did not significantly modify the contraction-relaxation coupling under low load, suggesting that it did not modify calcium uptake by the sarcoplasmic reticulum. Eltanolone did not significantly modify the contraction-relaxation coupling under high load, suggesting that it did not modify calcium myofilament sensitivity. Eltanolone decreased the postrest potentiation in a concentration-dependent manner (from 150 +/- 14% to 118 +/- 9% at 10 micrograms.ml-1, P < 0.001), suggesting a decrease in the maximum capacity of calcium release by the sarcoplasmic reticulum, whereas its solvent did not. However, eltanolone did not slow postrest potentiation recovery, as shown by the absence of significant changes in the recovery slope, tau (4.5 +/- 1.4 vs. 3.8 +/- 1.0 beats; difference not statistically significant). CONCLUSIONS: Eltanolone induced no significant inotropic effect on rat myocardium. It induced a decrease in the calcium release function of the sarcoplasmic reticulum, but this effect was not sufficiently important to modify the inotropic properties.

Anesthetics, Intravenous↗
PubMed1995

Systemic gas embolism complicating pulmonary contusion. Diagnosis and management using transesophageal echocardiography.

Systemic air embolism has been frequently reported after penetrating thoracic trauma. In blunt thoracic trauma, systemic air embolism has been rarely diagnosed, and then only after an invasive procedure such as thoracotomy. Transesophageal echocardiography has been recently introduced for the early assessment of trauma patients and is considered a sensitive noninvasive procedure to diagnose air embolism. We report three cases of systemic air embolism in patients with pulmonary contusion secondary to a blunt thoracic trauma requiring controlled ventilation. Transesophageal echocardiography was performed for evaluation of hemodynamic instability, and it showed air bubbles in the left atrium and left ventricle during the insufflation phase, which disappeared during apnea. A decrease in airway pressure (release of PEEP, low tidal volume, high frequency jet ventilation) significantly reduced the systemic air embolism. We concluded that systemic air embolism can occur after blunt thoracic trauma, and transesophageal echocardiography enables a rapid and accurate diagnosis that may be useful for therapeutic management.

Adult↗
PubMed1995

Contraction, relaxation, and economy of force generation in isolated human diaphragm muscle.

Contraction, relaxation, and energetics of normal human diaphragm strips (n = 10) were investigated over the whole load continuum in both twitch and tetanus modes. For a given level of isotonic total force and over a large part of the contraction phase, instantaneous velocity was shown to be a unique function of instantaneous length, regardless of time and initial length. In afterloaded tetanic contractions and over a wide range of loads, the peak lengthening velocity (VL) linearly decreased when maximum extent of muscle shortening (delta L) decreased. Stimulation mode modulated the VL versus delta L relationship, the slope of this linear regression being greater in tetanus than in twitch. Conversely, over a wide range of load, an increase in load linearly accelerated the peak rate of force decay, regardless of the stimulation mode. The energetics of human diaphragm muscle was evaluated in terms of both mechanical activity and economy of force generation. Maximum mechanical work (Wmax) differed significantly according to the stimulation mode, and the relative force at which Wmax occurred was higher in tetanus than in twitch (p < 0.05). The G curvature of the P-V hyperbola and maximum mechanical efficiency were significantly higher in tetanus than in twitch. This strongly suggests that the economy of force generation is higher in tetanus contractions than in twitch.

Adult↗
PubMed1994

Cardiotoxicity of colchicine in the rat.

OBJECTIVES: Colchicine poisoning may be lethal and a decrease in cardiac function has been reported in several case reports, but the precise cardiotoxicity of colchicine remains unknown. DESIGN: The experimental in vitro study assessed the intrinsic contractility of left ventricular papillary muscle in rats, 24 h after administration of intraperitoneal colchicine or saline. RESULTS: The administration of colchicine (2 or 4 mg.kg-1) in adult Wistar rats markedly impaired intrinsic myocardial contractility, as shown by a decrease in maximum shortening velocity (-32 and -61%, respectively), active isometric force (-47 and -65%, respectively), and peak power output (-57 and -69%, respectively) of left ventricular papillary muscle. Colchicine impaired isotonic relaxation and load dependence of relaxation, suggesting a decrease in sarcoplasmic reticulum function. Conversely, colchicine significantly accelerated isometric relaxation, suggesting a decrease in calcium myofilament sensitivity. Myothermal economy was markedly impaired only in some rats (3/10 in each group), in which the negative inotropic effect of colchicine appeared to be more particularly pronounced. CONCLUSION: The results indicate that the administration of high doses of colchicine induced intrinsic cardiotoxic effects. Due to its amplitude, such cardiotoxic action may participate in the fatal outcome of acute colchicine poisoning.

Acute Disease↗
PubMed1994

Ventilatory effects of active compression-decompression in dogs.

STUDY OBJECTIVE: To determine the ventilatory effect of active compression-decompression CPR and to compare it with two other techniques, standard manual cardiac massage and mechanical cardiac massage. DESIGN: Prospective, randomized laboratory investigation. PARTICIPANTS: Mongrel dogs. INTERVENTIONS: Nine adult mongrel dogs were anesthetized, intubated, and mechanically ventilated. They were instrumented to measure arterial pressure, esophageal pressure, airway pressure, end-tidal carbon dioxide concentration, and minute ventilation. RESULTS: After induction of ventricular fibrillation, three sequences of cardiac massage were performed randomly during mechanical ventilation, standard cardiac massage, mechanical cardiac massage, and active compression-decompression technique. The animals then were disconnected from the ventilator, and the three sequences were performed again. Active compression-decompression created negative minimum esophageal pressures and significantly decreased the minimum airway pressure as compared with the other techniques. Whatever the ventilatory condition, minute ventilation was increased dramatically during active compression-decompression. CONCLUSION: In this model of cardiac arrest, an important increase in minute ventilation was observed during active compression-decompression. This effect was significantly greater than the increases observed with other techniques of cardiac massage and was related to the negative pressure generated by active decompression.

Airway Resistance↗
PubMed1994

[Cardiovascular effects of Diprivan].

Propofol is a greater cardiovascular depressant agent than barbiturates (thiopentone, methohexitone). It is agreed that propofol changes the ventricular load as a result of its vasodilating effects, and that it depresses the sympathetic nervous system and the baroreflex, which result in a moderate bradycardia. The direct effects of propofol on the myocardium remain controversial. Propofol has no significant direct effect on intrinsic myocardial contractility and the decrease in cardiac output is related to anaesthesia on the one hand and to changes in ventricular load and the activity of the cardiac autonomic nervous system on the other hand. It is therefore understandable that the overall depressant effect of the cardiovascular system is amplified in patients whose ventricular function is closely dependent upon ventricular load and/or the activity of the sympathetic nervous system, and that the association with drugs causing bradycardia must be avoided. The logical therapeutic solution to propofol related cardiovascular depression, when deemed necessary, consists of vascular fluid loading and/or the administration of a vasoconstrictor.

Animals↗
PubMed1994

[Bilateral sensorineural hearing loss after general anesthesia].

A bilateral sensorineural (perceptive) deafness occurred in a 12-year-old girl, following laparoscopic appendicectomy under general anaesthesia not comprising nitrous oxide and low insufflation pressures and a normal haemodynamic status. There was neither a personal nor a familial history of hearing disturbances nor a preoperative intake of ototoxic drugs. The initial loss of 50 dB has been substantiated by evoked auditive potentials. The treatment consisted of hyperbaric oxygenotherapy and vasodilators. The girl recovered completely. Finally the etiology of this complication remained unrecognized. Possibly the CO2 insufflated into the abdominal cavity could be considered. However, its causative effect remains to be proven.

Anesthesia, General↗
PubMed1994

Intraoperative autologous transfusion in emergency surgery for spine trauma.

Although numerous studies have reported the use of intraoperative blood salvage in elective spine, cardiac, and vascular surgery, very few have assessed its efficiency during emergency surgery after spine trauma. We therefore retrospectively analyzed 238 cases of patients with spine trauma who had emergency surgery. Three variables were significantly associated with the risk of perioperative blood transfusion: thoracolumbar spine injury, a preoperative hematocrit < 35%, and an Injury Severity Score > 20. Among the 118 patients who received blood transfusions, 53 benefitted from intraoperative blood salvage using the Cell-Saver apparatus (Cell-Saver group) and 65 did not (control group). The Cell-Saver enabled a 47% reduction in homologous blood requirements (743 +/- 1191 mL vs. 1403 +/- 1453 mL, p < 0.008) and a 45% reduction in the number of patients who received homologous blood (45% vs. 82%, p < 0.001). Between these two groups, no significant differences were observed in the evolution of hematocrit, platelet count, and hemostasis values, but a slight increase in postoperative blood loss was noted in the Cell-Saver group (465 +/- 383 mL vs. 301 +/- 292 mL, p < 0.01). In conclusion, the efficiency of intraoperative blood salvage in emergency surgery for spine trauma is high and similar to that previously reported in elective spine surgery. The cost-effectiveness of this technique may be improved by appropriate selection of the patient.

Adolescent↗
PubMed1994

Pharmacokinetics of hydroxocobalamin in dogs.

Hydroxocobalamin is a powerful cyanide antidote that prevents sodium nitroprusside-induced cyanide toxicity. The pharmacokinetics of an i.v. bolus of hydroxocobalamin (70 and 140 mg/kg) were studied in conscious dogs (n = 6). Plasma hydroxocobalamin concentrations were measured using derivative spectrophotometry. The pharmacokinetics were compatible with a two-compartment model with a first-order distribution and elimination rate, and pharmacokinetic parameters were not different between the two doses, except for the elimination half-life. At 70 mg/kg, which is the recommended dose in acute cyanide poisoning, the elimination half-life was 7.36 +/- 0.79 h, the volume of distribution was 0.49 +/- 0.10 L/kg, and the total clearance 0.58 +/- 0.11 L/h. At high doses, hydroxocobalamin has a short elimination half-life and a limited volume of distribution that exceeds blood volume. These results could be useful in elaborating guidelines for the administration of hydroxocobalamin, when repetitive bolus and/or continuous infusion is required.

Animals↗
PubMed1994

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor.

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba-Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance (P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Haematological effects of postoperative autotransfusion in spinal surgery.

A prospective, randomized, controlled study was performed to determine the haematological and biochemical changes and clinical safety of postoperative autotransfusion (Solcotrans Orthopedic Plus system) in patients undergoing spinal surgery. Fifty patients were studied and were randomly allocated to Control (n = 25) and Solcotrans (n = 25) groups. Both groups had their postoperatively drained blood collected into the Solcotrans reservoir but only the Solcotrans group had this salvaged blood considered for reinfusion. After a 5-h postoperative collection period, analysis of the shed blood showed a haematocrit of 0.26 +/- 0.11, few platelets (80 +/- 63 10g.l-1), a fibrinogen level of less than 0.1 g.l-1 and a high level of D-dimers. The salvaged blood did not clot and aerobic and anaerobic culture produced no growth. The volume of blood collected was greater than 200 ml in 21 patients in the Solcotrans group who were autotransfused (384 +/- 101 ml, range 200-600 ml), and in 16 patients in the Control group. Within 15 min following completion of reinfusion of the salvaged blood there was a significant, but moderate decrease in platelet count (181 +/- 74 vs 223 +/- 90 10g.l-1, P < 0.001) and fibrinogen concentrations (2.1 +/- 0.8 vs 2.3 +/- 0.9 g.l-1, P < 0.02), and an increase in circulating D-dimers (P < 0.001) and plasma free haemoglobin concentrations (236 +/- 155 vs 82 +/- 79 mg.l-1, P < 0.001). Prothrombin time (PT) and activated partial thromboplastin time (APTT) did not increase, and potassium concentrations were not significantly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗
PubMed1994

Mechanics of human quadriceps muscle.

Mechanics of human quadriceps muscle strips (vastus lateralis; n = 10) were investigated over the whole load continuum. Mechanical experiments were performed at 29 degrees C and in both twitch and tetanus modes. For a given level of isotonic total load (P) and over a large part of the contraction phase, instantaneous velocity (V) was shown to be a unique function of instantaneous length (L), regardless of time and initial length. By considering this time- and initial length-independent mechanical property between instantaneous L and instantaneous V over the whole P continuum, a three-dimensional P-V-L relationship was constructed. Any variations in stimulation conditions modified the time-independent P-V-L diagram. Such modifications in the P-V-L relationship were characteristics of changes in contractile performance. Moreover, characteristics of the P-V relationship were investigated in both twitch and tetanus modes. The curvature of the P-V hyperbola was significantly higher in tetanus at 30 Hz than in twitch mode (P < 0.001). In conclusion, our study indicates that, in human quadriceps muscles, contractility can be defined as the time- and initial length-invariant part of a three-dimensional P-V-L relationship. Moreover, our data are consistent with an increase in economy of force generation in tetanus contractions compared with that in twitches.

Adult↗
PubMed1994

Fiberoptic bronchoscopy in brain-dead organ donors.

Criteria for selecting lung donors include normal chest X-ray and adequate gas exchange, but normal bronchoscopy is not always required. Thus, we conducted a prospective study of fiberoptic bronchoscopy in 72 brain-dead donors scheduled for multiple organ procurement. Chest X-ray was considered normal in 37 donors (51%), and PaO2 was > 400 mm Hg with an FIO2 of 100% in 34 donors (47%). Fiberoptic bronchoscopy was normal in only 24 donors (33%). In the remaining 48 donors, inhalation of gastric contents (n = 26) or blood (n = 17), pulmonary contusion (n = 5), or purulent bronchial secretions (n = 4) were noted. In the 26 donors with normal chest X-ray and PaO2 > 400 mm Hg with FIO2 of 100%, bronchoscopy was abnormal in 10 donors (38%). In 33 donors, arteriovenous difference in oxygen content (2.4 +/- 0.8 ml O2/100 ml), and pulmonary shunt (0.30 +/- 0.11, range 0.13-0.49) were measured. In the 15 donors with PaO2 > 400 mm Hg, pulmonary shunt was 0.23 +/- 0.07 (range 0.13-0.35). Our study suggests that chest X-ray and arterial blood gas analysis are not sufficient, and that fiberoptic bronchoscopy should be routinely performed to select potential lung donors. Even in brain-dead donors, only the measurement of pulmonary shunt can precisely assess pulmonary gas exchange.

Adult↗