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Biomedical subjects

Bruno Riou

Publications and source records attributed to Bruno Riou.

At least 55 records · Page 3Linked to original sources
PubMed2004

Cardioprotection with cariporide, a sodium-proton exchanger inhibitor, after prolonged ischemia and reperfusion in senescent rats.

This study investigated the effects of cariporide, an inhibitor of sodium-proton exchanger (NHE), during myocardial ischemia and reperfusion in senescence. Isolated Langendorff perfused hearts from 4 (adult) and 24 (senescent) month old male Wistar rats were submitted to prolonged low-flow ischemia (LFI) at 15% of initial coronary flow (180 min) or to 45 min of LFI (15% of initial coronary flow) followed by 30 min of reperfusion, without or with cariporide (10(-6)M). In senescent hearts, but not in adults, treatment with cariporide during prolonged LFI attenuated the elevation of coronary resistances (578 +/- 84 vs 1020 +/- 129% of baseline value after 180 min, P < 0.05) and delayed the decrease in active tension (35.6 +/- 5.1 vs 22.2 +/- 3.4% of baseline value after 60 min; P < 0.05). During reperfusion following LFI, the coronary flow impairment was more pronounced in senescents than in adults (48.4 +/- 9.4 and 75.3 +/- 4.9% of baseline value, respectively; P < 0.05) but was fully prevented in senescent hearts by cariporide treatment (95.6 +/- 17.0% of baseline value; P < 0.05 vs untreated group). This beneficial effect of cariporide on coronary tone was associated with an improvement of active and resting tensions and lower LDH release. Such functional protective effects of cariporide suggest an operative NHE during LFI at both coronary and myocardial levels in senescent heart. In addition, cariporide-associated improvement of post-ischemic recovery of coronary and contractile function as well as the limitation of cellular injury suggests a major role of calcium overload via NHE activation during reperfusion of senescent ischemic heart.

Aging↗
PubMed2004

Remifentanil induces systemic arterial vasodilation in humans with a total artificial heart.

BACKGROUND: To assess intrinsic vascular effects of remifentanil, increased concentrations were infused in critically ill patients with a total artificial heart. METHODS: In the early postoperative period after implantation of a total artificial heart, nine ventilated patients requiring short general anesthesia were included in this study. After anesthesia was induced with 0.3 mg/kg intravenous etomidate, the artificial heart settings were modified to render cardiac output "preload-independent." While maintenance of anesthesia was ensured by a continuous infusion of etomidate, increased concentrations of remifentanil (from 0.1 to 1 microg x kg(-1) x min(-1)) were infused in steps of 5 min under hemodynamic monitoring, including left and right atrial pressures, systemic and pulmonary arterial pressures, and left and right cardiac indices. The invasive procedure was started under the highest concentration of remifentanil tolerated by the patient. Infusion of remifentanil was stopped at the end of the invasive procedure, while etomidate infusion was maintained. New hemodynamic measurements were performed at the end of the 12-min recovery period. RESULTS: Remifentanil produced a dose-dependent and significant decrease in systemic arterial pressure and vascular resistances (n = 9) from a concentration of 0.25 microg x kg(-1) x min(-1). No significant changes were observed on pulmonary vascular resistances (n = 6). Neither right (n = 9) nor left (n = 6) atrial pressures were affected by remifentanil infusion. Hemodynamic variables returned to baseline value over the 12-min recovery period. CONCLUSIONS: In humans with a total artificial heart, remifentanil induces a systemic arterial vasodilation without significant effect on the capacitance vessels.

Adult↗
PubMed2004

Influence of sensory and proprioceptive impairment on the development of phantom limb syndrome during regional anesthesia.

BACKGROUND: The relation between impairment of sensorimotor function and occurrence of phantom limb syndrome (PLS) during regional anesthesia has not been described. This study assessed the temporal relation between PLS and the progression of sensorimotor impairment during placement of a brachial plexus nerve block. METHODS: Fifty-two patients had their arm randomly placed either alongside their body (group A) or in 90 degrees abduction (group B) immediately after brachial plexus nerve block placement. Responses to pin prick, cold, heat, touch, proprioception, and voluntary movement were assessed every 5 min for 60 min. Meanwhile, patients described their perceptions of the size, shape, and position of their anesthetized limb. RESULTS: Phantom limb syndrome occurred 19 +/- 9 min after nerve block placement. Proprioception was impaired and abolished after 22 +/- 9 and 43 +/- 17 min, respectively (P < 0.05 vs. PLS onset). When PLS occurred, responses to pin prick, cold, heat, and proprioception were abolished in 96, 94, 87, and 4% of patients, respectively. Patients were more likely to feel their anesthetized limb in adduction and in abduction in groups A and B (P < 0.05 vs. group A), respectively. After PLS had become motionless, two stereotyped positions were identified: arm adduction, elbow flexion, hand over the abdomen (68% of group A patients) and arm abduction, elbow flexion, hand held close to the homolateral ear (48% of group B patients). CONCLUSIONS: This study provides a better understanding of the determinants of PLS by showing that the final position of PLS is related both to the abolition of proprioception and the initial position of the anesthetized limb.

Adult↗
PubMed2004

Myocardial effects of halothane and sevoflurane in diabetic rats.

BACKGROUND: Diabetes induces significant myocardial abnormalities, but the effects of halogenated anesthetics on this diseased myocardium remain a matter of debate. METHODS: Left ventricular papillary muscles and triton-skinned cardiac fibers were provided from control and streptozotocin-induced diabetic rats. The effects of halothane and sevoflurane were studied on inotropic and lusitropic responses, under low (isotony) and high (isometry) loads in papillary muscles and then on isometric tension-Ca2+ concentration (pCa) relations obtained in triton-skinned cardiac fibers. Data are presented as mean +/- SD. RESULTS: Sevoflurane and halothane induced a negative inotropic effect that was more important in diabetic rats (active force: 1.5% halothane, 19+/-6 vs. 24+/-6% of baseline, P < 0.05; 3.6% sevoflurane, 47+/-14 vs. 69+/-17% of baseline, P < 0.05). However, when differences in minimum alveolar concentration were considered, no significant difference was observed between groups for halothane. The effects of halothane and sevoflurane on isotonic relaxation and postrest potentiation were not significantly different between groups. In contrast, the decrease in Ca myofilament sensitivity produced by each anesthetic agent was greater in diabetic rats than in control rats (0.65% halothane, -0.15+/-0.07 vs. -0.05+/-0.04 pCa unit, P < 0.05; 1.8% sevoflurane, -0.12+/-0.06 vs. -0.06+/-0.04 pCa unit, P < 0.05). CONCLUSIONS: The negative inotropic effect of halothane and sevoflurane was greater in diabetic rats, mainly because of a significant decrease in myofilament Ca sensitivity.

Animals↗
PubMed2004

Predictive performance and variability of the cardiac anesthesia risk evaluation score.

BACKGROUND: The Cardiac Anesthesia Risk Evaluation (CARE) score, a simple Canadian classification for predicting outcome after cardiac surgery, was evaluated in 556 consecutive patients in Paris, France. The authors compared its performance to those of two multifactorial risk indexes (European System for Cardiac Operative Risk Evaluation [EuroSCORE] and Tu score) and tested its variability between groups of physicians (anesthesiologists, surgeons, and cardiologists). METHODS: Each patient was simultaneously assessed using the three scores by an attending anesthesiologist in the immediate preoperative period. In a blinded study, the CARE score category was also determined by a cardiologist the day before surgery, by a surgeon in the operating room, and by a second anesthesiologist at arrival in intensive care unit. Calibration and discrimination for predicting outcomes were assessed by goodness-of-fit test and area under the receiver operating characteristic curve, respectively. The level of agreement of the CARE scoring between the three physicians was then assessed. RESULTS: The calibration analysis revealed no significant difference between expected and observed outcomes for the three classifications. The areas under the receiver operating characteristic curves for mortality were 0.77 with the CARE score, 0.78 with the EuroSCORE, and 0.73 with the Tu score (not significant). The agreement rate of the CARE scoring between two anesthesiologists, between anesthesiologists and surgeons, and between anesthesiologists and cardiologists were 90%, 83%, and 77%, respectively. CONCLUSIONS: Despite its simplicity, the CARE score predicts mortality and major morbidity as well the EuroSCORE. In addition, it remains devoid of significant variability when used by groups of physicians of different specialties.

Aged↗
PubMed2004

Time sequence of sensory changes after upper extremity block: swelling sensation is an early and accurate predictor of success.

BACKGROUND: Sensory assessment to estimate spread and effectiveness of a peripheral nerve block is difficult because no clinical test is specific for small sensory fibers. Occurrence of a swelling illusion (SI) during a peripheral nerve block corresponds to the impairment of small sensory fibers. The authors investigated the usefulness of SI in predicting successful peripheral nerve block by assessing the temporospatial correlation between progression of sensory impairment in cutaneous distributions anesthetized and localization of SI during peripheral nerve block installation. METHODS: Interscalene, infracoracoid, or sciatic nerve blocks were performed using a nerve stimulator and 1.5% mepivacaine in 53 patients, with a total of 201 nerves to be anesthetized. Pinprick, cold, warm, touch, and proprioception were assessed every 3 min, while patients were asked to describe their perception of size and shape of their anesthetized limb and localization of these illusions. Data are presented as mean +/- SD and percentage (95% confidence interval). RESULTS: Failure occurred in 12 cutaneous distributions out of a total of 201 theoretically blocked nerves. SI appeared earlier than warmth impairment (4.3 +/- 2.7 vs. 6.2 +/- 2.0 min; P < 0.05), always corresponding to successfully anesthetized cutaneous distributions, with the exception of 1 patient, who developed SI in 2 cutaneous distributions while sensory testing indicated failure in 1 distribution. SI successfully predicted the blockade of a cutaneous distribution with a sensitivity of 1.00 (0.98-1.00), a specificity of 0.92 (0.65-0.99), and an accuracy of 0.99 (0.97-1.00). CONCLUSIONS: Swelling illusion may provide an early assessment of the success of a peripheral nerve block in unsedated patients.

Adult↗
PubMed2004

Interaction of halogenated anesthetics with alpha- and beta-adrenoceptor stimulations in diabetic rat myocardium.

BACKGROUND: Halogenated anesthetics potentiate the positive inotropic effects of alpha- and beta-adrenoceptor stimulations. Although diabetes mellitus induces significant myocardial abnormalities, the interaction of halogenated anesthetics and adrenoceptor stimulation in diabetic myocardium remains unknown. METHODS: Left ventricular papillary muscles were provided from healthy and streptozotocin-induced diabetic rats. Effects of 1 minimum alveolar concentration halothane, isoflurane, and sevoflurane on the inotropic and lusitropic responses of alpha (phenylephrine)- and beta (isoproterenol)-adrenoceptor stimulations were studied at 29 degrees C with 12 pulses/min. Data shown are mean percentage of baseline active force +/- SD. RESULTS: Phenylephrine induced comparable positive inotropic effects in healthy and diabetic rats (143 +/- 8 vs. 136 +/- 18%; not significant), but the potentiation by halogenated anesthetics was abolished in the diabetic rats (121 +/- 20, 130 +/- 20, and 123 +/- 20% for halothane, isoflurane, and sevoflurane, respectively; not significant). In diabetic rats, the positive inotropic effect of isoproterenol was markedly diminished (109 +/- 9 vs. 190 +/- 18%; P < 0.05), but its potentiation was preserved with isoflurane (148 +/- 21%; P < 0.05) and sevoflurane (161 +/- 40%; P < 0.05) but not with halothane (126 +/- 16%; not significant). Halothane induced a deleterious effect on the sarcoplasmic reticulum, as shown by its impairment in the lusitropic effect of isoproterenol, compared with isoflurane and sevoflurane. CONCLUSION: Potentiation of the positive inotropic effect of alpha-adrenoceptor stimulation by halogenated anesthetics is abolished in diabetic rats. In contrast, potentiation of beta-adrenoceptor stimulation is preserved with isoflurane and sevoflurane but not with halothane, probably because of its deleterious effects on sarcoplasmic reticulum.

Adrenergic alpha-Agonists↗
PubMed2004

The effects of a polymerized bovine-derived hemoglobin solution in a rabbit model of arterial thrombosis and bleeding.

UNLABELLED: Hemoglobin-based oxygen carriers (HBOCs) have been developed primarily for their oxygenating function and possible use as an alternative to red blood cells during surgery or after major trauma. However, their effect on hemostasis has not been studied extensively. We compared the effects on hemostasis of bovine-derived hemoglobin solution (HBOC-201) with gelatin solution and saline infusion in an experimental model of arterial thrombosis and bleeding. After anesthesia, the Folts model was constructed in 30 rabbits. The common carotid artery was exposed, and a 60% stenosis was induced. A compression injury of the artery was then produced, which triggered a series of cyclic episodes of thrombosis (cyclic flow reductions [CFRs]). After the number of baseline CFRs was counted, animals were assigned randomly to one of three groups (n = 10 each): saline (control), gelatin, or HBOC-201 solution. The effect of studied solutions was observed by recording the number of CFRs during another period and was compared with that of saline. Ear immersion bleeding time was recorded after each CFR period. Gelatin and HBOC-201 had similar effects, manifested by significantly decreased CFRs (from median of 7 to 1 and 6 to 1, respectively) and significantly lengthened bleeding time (from 88 to 98 s and 81 to 102 s, respectively; P < 0.05). Saline infusion had no significant effect on CFRs or bleeding time. HBOC-201 and gelatin had similar effects marked by a reduction in the arterial thrombosis rate and increased bleeding time in rabbits. IMPLICATIONS: In a rabbit thrombosis and hemorrhagic model, a polymerized bovine-derived hemoglobin solution and a gelatin solution infusion decreased arterial thrombosis and lengthened bleeding time.

Animals↗
PubMed2004

Assessing residual neuromuscular blockade using acceleromyography can be deceptive in postoperative awake patients.

UNLABELLED: Postoperative awake patients may have significant residual neuromuscular block. In awake patients, the results of accelerometry are affected by extra movements to which the thumb may be subject. In this study, we evaluated the repeatability of train-of-four (TOF) ratio using acceleromyography in 253 patients recovering from anesthesia. Immediately after arrival in the postanesthesia care unit, the ulnar nerve was stimulated with TOF stimulation. The evoked response at the thumb was measured by the TOF-Watch apparatus. The current intensity was 30 mA. Two TOF stimulations were applied and recorded at 30-s intervals. A Bland-Altman test was used. The Kappa (kappa) test for clinical agreement between the two measurements was also calculated according to the presence or absence of a residual neuromuscular blockade, defined as a TOF ratio <0.9. According to the presence of a residual neuromuscular blockade, the paired TOF ratios were discordant in 61 patients (24%; 95% confidence interval, 21%-27%). The kappa test indicated a moderate agreement (k = 0.47). We demonstrated that accelerometry as used in this study is not always accurate. Two isolated acceleromyograph TOF ratios are not an accurate representation of the neuromuscular status of the patient recovering from anesthesia. IMPLICATIONS: Clinicians should be aware that acceleromyography as used in this study does not always provide precise train-of-four ratio measurements. Two isolated acceleromyograph train-of-four ratios are not an accurate representation of the neuromuscular status of the patient recovering from anesthesia.

Adult↗
PubMed2004

Amplification by hyperoxia of coronary vasodilation induced by propofol.

UNLABELLED: We tested the hypothesis that in vitro coronary and myocardial effects of propofol (10-300 microM) should be significantly modified in an isolated and erythrocyte-perfused rabbit heart model in the absence (PaO(2) = 137 +/- 16 mm Hg, n = 12) or in the presence (PaO(2) = 541 +/- 138 mm Hg, n = 12) of hyperoxia. The induction of hyperoxia provoked a significant coronary vasoconstriction (-13% +/- 7%). Propofol induced increased coronary vasodilation in the presence of hyperoxia. Because high oxygen tension has been reported to induce a coronary vasoconstriction mediated by the closure of adenosine triphosphate-sensitive potassium channels, we studied the effects of propofol in 2 additional groups of hearts (n = 6 in each group) pretreated by glibenclamide (0.6 microM) and cromakalim (0.5 microM) in the absence and presence of hyperoxia, respectively. The pretreatment by glibenclamide induced a coronary vasoconstriction (-16% +/- 7%) which did not affect propofol coronary vasodilation. The pretreatment by cromakalim abolished the amplification of propofol coronary vasodilation in the presence of hyperoxia. Propofol induced a significant decrease in myocardial performance for a concentration >100 micro M both in the absence and presence of hyperoxia. We conclude that propofol coronary vasodilation is amplified in the presence of hyperoxia. This phenomenon is not explained by the previous coronary vasoconstriction induced by glibenclamide. However, the pretreatment of hearts by cromakalim abolished the amplification of propofol coronary vasodilation in the presence of hyperoxia. The myocardial effects of propofol were not affected by the presence of hyperoxia. IMPLICATIONS: Propofol induced a coronary vasodilation that was amplified in the presence of hyperoxia. This phenomenon does not seem to be related to previous coronary vasoconstriction. The myocardial effects of propofol were not significantly modified in the presence of hyperoxia.

ATP-Binding Cassette Transporters↗
PubMed2004

Mechanical properties of tracheal smooth muscle are impaired in the rabbit with experimental cardiac pressure overload.

UNLABELLED: STUDY OBJECTIVES/DESIGN: Impaired function of striated and arterial smooth muscle is known to occur in humans and animals with various forms of cardiac diseases, but limited information is available on the mechanical behavior of airway smooth muscle. We tested the hypothesis that the baseline mechanical properties of tracheal smooth muscle (TSM) were impaired at an early stage of cardiac overload. ANIMALS: We used a model of cardiac hypertrophy induced by surgical abdominal aortic stenosis (AS) in adult rabbits. Twelve animals with AS and 8 sham-operated control rabbits were studied 12 weeks after surgery. In rabbits with AS, the heart weight/body weight ratio was higher than in control rabbits (2.36 +/- 0.43 g/kg vs 1.98 +/- 0.20 g/kg, p < 0.05) [mean +/- SD], attesting to moderate cardiac hypertrophy. No clinical signs of congestive heart failure were observed. MEASUREMENTS: Isolated TSM strips were electrically stimulated at 37 degrees C, 2.5 mM [Ca(2+)](0), against 8 to 10 load levels, from zero load to full isometry. Force-velocity relationship was elicited using the conventional afterloaded isotonic method. RESULTS: Peak isometric tension was lower in rabbits with AS than in control rabbits (25 +/- 11 mN/mm(2) vs 34 +/- 14 mN/mm(2), p < 0.05), whereas maximum unloaded shortening velocity, maximum extent of muscle shortening, and relaxation parameters did not differ between groups. The curvature of the force-velocity relationship (which reflects the myothermal economy of force generation) and peak mechanical efficiency were lower in rabbits with AS than in control rabbits. CONCLUSIONS: These results indicate that the contraction of isolated rabbit TSM was less powerful and less economical in cardiac hypertrophy, attesting to early impairment of the mechanical properties of TSM during cardiac overload.

Animals↗
PubMed2003

Unprecedented heat-related deaths during the 2003 heat wave in Paris: consequences on emergency departments.

In August 2003, France sustained an unprecedented heat wave that resulted in 14,800 excess deaths. The consequences were maximal in the Paris area. The Assistance Publique-Hôpitaux de Paris reported more than 2600 excess emergency department visits, 1900 excess hospital admissions, and 475 excess deaths despite a rapid organization. Indeed, simple preventice measures before hospital admissions are only able to reduce mortality which mostly occurred at home and in nursing homes.

Climate↗
PubMed2003

DCL-Hb for trauma patients with severe hemorrhagic shock: the European "On-Scene" multicenter study.

OBJECTIVE: A major cause of death in patients with severe hemorrhagic shock following trauma is the subsequent occurrence of multiple organ failure due to tissue hypoxia. Early administration of an oxygen carrier may reduce the occurrence of organ failures and improve survival. It may also reduce the need of blood products. DESIGN AND SETTING: Prospective multicenter study in a university clinic. PATIENTS: 121 patients with severe hemorrhagic shock. INTERVENTIONS: Patients were randomly assigned "on-scene" to receive either up to 1000 ml of a 10% diaspirin cross-linked hemoglobin (DCLHb) solution or the study center's standard therapy. MEASUREMENTS AND RESULTS: Demographic and physiological characteristics of the two treatment groups at baseline were comparable. Organ failures and survival rates until day 5 and day 28 showed no significant differences. The sponsor therefore terminated this trial prematurely after an interim evaluation of the data indicated no evidence of efficacy to offset concerns raised about the safety of DCLHb. Median volumes of cumulative blood products administered on 1 (1595 vs. 3716 ml) and 7 days (3139 vs. 4746 ml) after admission were lower in the DCLHb group. CONCLUSIONS: The early application of an oxygen carrier (DCLHb) to patients with severe hemorrhagic shock following trauma had no significant effect on the occurrence of organ failure or on 5- and 28-day survival in this abbreviated trial. However, early infusion of up to 1000 ml DCLHb reduces the need for blood products without changing morbidity or survival.

Adolescent↗
PubMed2003

Terlipressin versus norepinephrine to correct refractory arterial hypotension after general anesthesia in patients chronically treated with renin-angiotensin system inhibitors.

BACKGROUND: Terlipressin, a precursor that is metabolized to lysine-vasopressin, has been proposed as a drug for treatment of intraoperative arterial hypotension refractory to ephedrine in patients who have received long-term treatment with renin-angiotensin system inhibitors. The authors compared the effectiveness of terlipressin and norepinephrine to correct hypotension in these patients. METHODS: Among 42 patients scheduled for elective carotid endarterectomy, 20 had arterial hypotension following general anesthesia that was refractory to ephedrine. These patients were the basis of the study. After randomization, they received either 1 mg intravenous terlipressin (n = 10) or norepinephrine infusion (n = 10). Beat-by-beat recordings of systolic arterial blood pressure and heart rate were stored on a computer. The intraoperative maximum and minimum values of blood pressure and heart rate, and the time spent with systolic arterial blood pressure below 90 mmHg and above 160 mmHg, were used as indices of hemodynamic stability. Data are expressed as median (95% confidence interval). RESULTS: Terlipressin and norepinephrine corrected arterial hypotension in all cases. However, time spent with systolic arterial blood pressure below 90 mmHg was less in the terlipressin group (0 s [0-120 s] vs. 510 s [120-1011 s]; P < 0.001). Nonresponse to treatment (defined as three boluses of terlipressin or three changes in norepinephrine infusion) occurred in zero and eight cases (P < 0.05), respectively. CONCLUSIONS: In patients who received long-term treatment with renin-angiotensin system inhibitors, intraoperative refractory arterial hypotension was corrected with both terlipressin and norepinephrine. However, terlipressin was more rapidly effective for maintaining normal systolic arterial blood pressure during general anesthesia.

Aged↗
PubMed2003

Relationships between measurement of pain using visual analog score and morphine requirements during postoperative intravenous morphine titration.

BACKGROUND: Although intravenous morphine titration is widely used to obtain rapid and complete postoperative pain relief, the relationship between measurement of pain and morphine requirements varies, and the evolution of pain during titration is poorly understood. METHODS: Intravenous morphine titration was administered as a bolus of 2 (body weight < or = 60 kg) or 3 mg (body weight > 60 kg) during the immediate postoperative period in the PACU. The interval between each bolus was 5 min. The visual analog scale (VAS) score threshold required to administer morphine was 30, and pain relief was defined as a VAS score of 30 or less. RESULTS: Data from 3,045 patients were analyzed. The mean initial VAS score was 73 +/- 19 (mean +/- SD), and the mean morphine dose required to obtain pain relief was 0.17 +/- 0.10 mg/kg, i.e., a median of four boluses (range, 1-20). When patients were grouped according to several classes of initial VAS score (31-39, 40-49, 50-59, 60-69, 70-79, 80-89, 90-100), it seemed that the relationship between VAS score and morphine requirements was a sigmoid curve. A VAS score of 70 or greater predicted the need for a high (>0.15 mg/kg) morphine dose (sensitivity, 0.77; specificity, 0.54). During the pain relief process, the relationship between VAS score and time was depicted by a sigmoid curve. CONCLUSION: A VAS score of 70 or greater should be considered indicative of severe pain. The relationship between the initial VAS score and morphine requirements is not linear, and the evolution of the VAS score during the pain relief process is described by a sigmoid curve.

Aged↗
PubMed2003

Overestimation of Bispectral Index in sedated intensive care unit patients revealed by administration of muscle relaxant.

BACKGROUND: Electromyographic activity has previously been reported to elevate the Bispectral Index (BIS) in patients not receiving neuromuscular blockade while under sedation in the intensive care unit. This study aimed to investigate the magnitude of the decrease of BIS following administration of muscle relaxant in sedated intensive care unit patients. METHODS: The authors prospectively investigated 45 patients who were continuously sedated with midazolam and sufentanil to achieve a Sedation-Agitation Scale value equal to 1 and who required administration of muscle relaxant. BIS (BIS version 2.10), electromyography, and acceleromyography at the adductor pollicis muscle were recorded simultaneously before and after neuromuscular blockade. Sixteen of these 45 patients were also studied simultaneously with the new BIS XP. RESULTS: After administration of a muscle relaxant, BIS (67 +/- 19 vs. 43 +/- 10, P < 0.001) and electromyographic activity (37 +/- 9 vs. 27 +/- 3 dB, P < 0.001) significantly decreased. Multiple regression analysis showed that the decrease of BIS following administration of myorelaxant was significantly correlated to BIS and electromyographic baseline values. Using standard BIS range guidelines, the number of patients under light or deep sedation versus general anesthesia or deep hypnotic state was markedly overestimated before administration of myorelaxant (53 vs. 2%, P < 0.001). CONCLUSIONS: The BIS in sedated intensive care unit patients may be lower with paralysis for an equivalent degree of sedation because of high muscular activity. The magnitude of BIS overestimation is significantly correlated to both BIS and electromyographic activity before neuromuscular blockade. The authors conclude that clinicians who determine the amount of sedation in intensive care unit patients only from BIS monitoring may expose them to unnecessary oversedation.

Anesthetics, Intravenous↗