Olivier Langeron

Prediction of Difficult Mask Ventilation

Background Maintenance of airway patency and oxygenation are the main objectives of face-mask ventilation. Because the incidence of difficult mask ventilation (DMV) and the factors associated with it are not well known, we undertook this prospective study. Methods Difficult mask ventilation was defined as the inability of an unassisted anesthesiologist to maintain the measured oxygen saturation as measured by pulse oximetry > 92% or to prevent or reverse signs of inadequate ventilation during positive-pressure mask ventilation under general anesthesia. A univariate analysis was performed to identify potential factors predicting DMV, followed by a multivariate analysis, and odds ratio and 95% confidence interval were calculated. Results A total of 1,502 patients were prospectively included. DMV was reported in 75 patients (5%; 95% confidence interval, 3.9–6.1%), with one case of impossible ventilation. DMV was anticipated by the anesthesiologist in only 13 patients (17% of the DMV cases). Body mass index, age, macroglossia, beard, lack of teeth, history of snoring, increased Mallampati grade, and lower thyromental distance were identified in the univariate analysis as potential DMV risk factors. Using a multivariate analysis, five criteria were recognized as independent factors for a DMV (age older than 55 yr, body mass index > 26 kg/m2, beard, lack of teeth, history of snoring), the presence of two indicating high likelihood of DMV (sensitivity, 0.72; specificity, 0.73). Conclusion In a general adult population, DMV was reported in 5% of the patients. A simple DMV risk score was established. Being able to more accurately predict DMV may improve the safety of airway management.

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.

Voluven, a Lower Substituted Novel Hydroxyethyl Starch (hes 130/0.4), Causes Fewer Effects on Coagulation in Major Orthopedic Surgery than Hes 200/0.5

Hydroxyethyl starch (HES) solutions are effective plasma volume expanders. Impairment of coagulation occurs with large HES volumes infused perioperatively. Therefore, a lower substituted novel HES (Voluven®; Fresenius Kabi, Bad Homburg, Germany) was developed to minimize hemostatic interactions, and was compared with HAES-steril® (Fresenius Kabi) (pentastarch) regarding safety and efficacy. We performed a prospective, randomized, double-blinded study in 100 major orthopedic surgery patients. Because the 95% confidence interval (-330 mL; +284 mL) for the treatment contrast Voluven®-HAES-steril® was entirely included in the predefined equivalence range (± 500 mL), comparable efficacy was established. Voluven® interfered significantly less than HAES-steril® with coagulation factor VIII levels and partial thromboplastin time postoperatively. Total amounts of red blood cells transfused were comparable between the Voluven® and HAES-steril® groups, but a significantly reduced need for homologous red blood cells was observed in the Voluven® group. We conclude that in large-blood–loss surgery, Voluven® has a comparable efficacy with HAES-steril® and may reduce coagulation impairment, possibly leading to a smaller number of allogeneic blood transfusions.

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 ≤ 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.

Postoperative titration of intravenous morphine in the elderly patient.

Background Intravenous morphine titration is used to obtain rapid and complete postoperative pain relief. Whether this titration can be safely administered in the elderly patients remains a matter for debate. Methods Intravenous morphine titration was administered as a bolus of 2 (body weight ≤ 60 kg) or 3 (body weight > 60 kg) mg. The interval between each bolus was 5 min. There was no limitation in the number of boluses given until pain relief or severe adverse effect occurred. The visual analog scale threshold required to administer morphine was 30 mm, and pain relief was defined as a visual analog scale score of 30 mm or less. Patients were divided into two groups: young and elderly (age ≥ 70 yr) patients. Data were expressed as mean ± SD. Results Eight hundred seventy-five patients (83%) were young and 175 patients (17%) were elderly. At the end of morphine titration, the visual analog scale score and the number of patients with pain relief were not significantly different between groups. The total dose of morphine per kilograms of body weight administered was not significantly different between groups (0.15 ± 0.10 vs. 0.14 ± 0.09 mg/kg, not significant). No significant differences were observed in the incidence of morphine-related adverse effects (13 vs. 14%, not significant), the number of sedated patients (60 vs. 60%, not significant), and the number of patients whose titration had to be stopped (2 vs. 2%, not significant). Conclusion Intravenous morphine titration can be safely administered to elderly patients. Because titration is adapted to individual pain, the same protocol can be applied to young and elderly patients.

Comparison of the intubating laryngeal mask airway with the fiberoptic intubation in anticipated difficult airway management.

Background The intubating laryngeal mask airway (ILMA; Fastrach ™; Laryngeal Mask Company, Henley-on-Thames, UK) may provide an alternative technique to fiberoptic intubation (FIB) to facilitate the management of the anticipated difficult airway. The authors therefore compared the effectiveness of the ILMA with FIB in patients with anticipated difficult intubation. Methods One hundred patients, with at least one difficult intubation criteria (Mallampati class III or IV, thyromental distance < 65 mm, interincisor distance < 35 mm) were enrolled (FIB group, n = 49; ILMA group, n = 51) in this prospective randomized study. Anesthesia was induced with propofol and maintained with alfentanil and propofol after an efficient mask ventilation has been demonstrated. The success of the technique (within three attempts), the number of attempts, duration of the successful attempt, and adverse events (oxygen saturation < 90%, bleeding) were recorded. Results The rate of successful tracheal intubation with ILMA was 94% and comparable with FIB (92%). The number of attempts and the time to succeed were not significantly different between groups. In case of failure of the first technique, the alternative technique always succeeded. Failures in FIB group were related to oxygen desaturation (oxygen saturation < 90%) and bleeding, and to previous cervical radiotherapy in the ILMA group. Adverse events occurred significantly more frequently in FIB group than in ILMA group (18 vs. 0%, P < 0.05). Conclusion The authors obtained a high success rate and comparable duration of tracheal intubation with ILMA and FIB techniques. In patients with previous cervical radiotherapy, the use of ILMA cannot be recommended. Nevertheless, the use of the ILMA was associated with fewer adverse events.

Minimum Alveolar Concentration of Volatile Anesthetics in Rats during Postnatal Maturation

BackgroundAlthough neonatal rats have become widely used as experimental laboratory animals, minimum alveolar concentration (MAC) values of volatile anesthetics in rats during postnatal maturation remain unknown. MethodsWe determined MAC values of volatile anesthetics in spontaneously breathing neonatal (2-, 9-, and 30-day-old) and adult Wistar rats exposed to increasing (in 0.1–0.2% steps) concentrations of halothane, isoflurane, or sevoflurane (n = 12–20 in each group), using the tail-clamp technique. MAC and its 95% confidence intervals were calculated using logistic regression and corrected for body temperature (37°C). ResultsIn adult rats, inspired MAC values corrected at 37°C were as follows: halothane, 0.88% (confidence interval, 0.82–0.93%); isoflurane, 1.12% (1.07–1.18%); and sevoflurane, 1.97% (1.84–2.10%). In 30-day-old rats, the values were as follows: halothane, 1.14% (1.07–1.20%); isoflurane, 1.67% (1.58–1.76%); and sevoflurane, 2.95% (2.75–3.15%). In 9-day-old rats, inspired MAC values were as follows: halothane, 1.68% (1.58–1.78%); isoflurane, 2.34% (2.21–2.47%); and sevoflurane, 3.74% (3.64–3.86%). In 2-day-old rats, inspired MAC values were as follows: halothane, 1.54% (1.44–1.64%); isoflurane, 1.86% (1.72–2.01%); and sevoflurane, 3.28% (3.09–3.47%). ConclusionAs postnatal age increases, MAC value significantly increases, reaching the greatest value in 9-day-old rats, and decreases thereafter, and at 30 days is still greater than the adult MAC value.

Detection of brain death onset using the bispectral index in severely comatose patients

Abstract.Objectives: To evaluate the accuracy of bispectral index (BIS) monitoring for the diagnosis of brain death in severely comatose patients. Design: A prospective study in an intensive care unit of a university hospital. Population: Fifty-six severely comatose patients (Glasgow Coma Score ≤5) admitted to the ICU mainly because of intracerebral hemorrhage, head injury, or postanoxic coma. Methods: BIS was recorded continuously during the hospitalization in the ICU. Where necessary, clinical brain death was confirmed by EEG or cerebral angiography. Measurements and results: Twelve patients were already clinically brain dead at the time of admission, and their individual BIS values were 0. In each of these 12 patients brain death was thereafter confirmed by EEG or cerebral angiography. Forty-four patients were not clinically brain-dead at the time of admission, and their individual BIS values were between 20 and 79. Twenty-seven of these patients became brain-dead, and their individual BIS values dropped to 0 in a few hours to a few days. In these 27 patients EEG or cerebral angiography was performed after the BIS value decreased to 0 and confirmed brain death in all cases. Seventeen patients who did not become brain dead during their hospitalization in the ICU had persistent electrocerebral activity on EEG, and their average BIS values remained above 35. Conclusion: BIS can be used in severely comatose patients as an assessment of brain death onset, enabling appropriate scheduling of either EEG or cerebral angiography to confirm brain death.

Prognostic Significance of Blood Lactate and Lactate Clearance in Trauma Patients

Background:Lactate has been shown to be a prognostic biomarker in trauma. Although lactate clearance has already been proposed as an intermediate endpoint in randomized trials, its precise role in trauma patients remains to be determined. Methods:Blood lactate levels and lactate clearance (LC) were calculated at admission and 2 and 4 h later in trauma patients. The association of initial blood lactate level and lactate clearance with mortality was tested using receiver-operating characteristics curve, logistic regression using triage scores, Trauma Related Injury Severity Score as a reference standard, and reclassification method. Results:The authors evaluated 586 trauma patients (mean age 38 ± 16 yr, 84% blunt and 16% penetrating, mortality 13%). Blood lactate levels at admission were elevated in 327 (56%) patients. The lactate clearance should be calculated within the first 2 h after admission as LC0–2 h was correlated with LC0–4 h (R2 = 0.55, P < 0.001) but not with LC2–4 h (R2 = 0.04, not significant). The lactate clearance provides additional predictive information to initial blood lactate levels and triage scores and the reference score. This additional information may be summarized using a categorical approach (i.e., less than or equal to −20 %/h) in contrast to initial blood lactate. The results were comparable in patients with high (5 mM/l or more) initial blood lactate. Conclusions:Early (0–2 h) lactate clearance is an important and independent prognostic variable that should probably be incorporated in future decision schemes for the resuscitation of trauma patients.

Postoperative morphine consumption in the elderly patient.

Background It has been suggested that the dose of intravenous morphine used during postoperative titration is not modified by aging. The authors therefore studied morphine requirements in patients undergoing total hip replacement. Methods Intravenous morphine titration was administered as boluses, then subcutaneous morphine was administered every 4 h over 24 h. Pain was assessed by use of the visual analog scale (0 to 100), and the threshold required to administer morphine was 30. Young and elderly (≥70 yr old) patients were compared. Data are mean ± SD or odds ratio (OR) [95% CI]. Results Two hundred twenty-four patients (68%) were young and 105 (32%) were elderly. The initial visual analog scale was not significantly different between groups. The dose of intravenous morphine in the postanesthesia care unit was not significantly different between young and elderly patients (0.15 ± 0.11 vs. 0.14 ± 0.10 mg/kg, P = NS), in contrast to the dose of subcutaneous morphine (0.18 ± 0.18 vs. 0.11 ± 0.11 mg/kg, P < 0.001) in the ward. Only severe pain (visual analog scale of 70 or greater; OR, 10.5 [4.5–24.8]) was significantly associated with a high dose (greater than 0.15 mg/kg) of intravenous morphine, whereas severe pain (OR, 2.5 [1.6–4.0]), age less than 60 yr (OR, 2.3 [1.4–3.8]), and absence of a nonsteroidal antiinflammatory drug (OR, 1.9 [1.2–3.1]) were significantly associated with a high dose (greater than 0.12 mg/kg) of subcutaneous morphine. Conclusions The dose of intravenous morphine during titration is not modified in elderly patients, in contrast to the dose administered subcutaneously over a prolonged period.