Alain D'Hollander

Large Tidal Volume Ventilation Does Not Improve Oxygenation in Morbidly Obese Patients During Anesthesia

Eight morbidly obese patients (body mass index [BMI] = 46) were studied during general anesthesia and controlled mechanical ventilation.To evaluate the effect of large tidal volume ventilation on oxygenation and ventilation, the baseline 13 mL/kg tidal volume (VT) (calculated by the ideal body weight) was increased in 3 mL/kg volume increments to 22 mL/kg, while ventilatory rate (RR) and inspiratory time (TI) were kept constant. Each volume increment was maintained for 15 min. Gas exchange was assessed by measuring the arterial blood oxygen tensions, and calculating the indices of alveolar-arterial oxygen tension difference [P(A-a)O2] and arterial/alveolar oxygen tension ratio (a/A). Peak inspiratory airway pressure (Ppeak), end-inspiratory airway pressure (Pplateau), and compliance of the respiratory system (CRS) were recorded using the Capnomac Ultima Trademark (Datex, Helsinki, Finland) on-line respiratory monitor. Increasing tidal volumes to 22 mL/kg increased the recorded Ppeak (26.3 +/- 4.1 vs 37.9 +/- 3.2 cm H2 O, P < 0.008), Pplateau (21.5 +/- 3.6 vs 27.7 +/- 4.3 cm H2 O, P < 0.01), and CRS (39.8 +/- 7.7 vs 48.5 +/- 8.3 mL/cm H2 O significantly without improving arterial oxygen tension and resulted in severe hypocapnia. Since changes in arterial oxygenation were small and not statistically significant, mechanical ventilation of morbidly obese patients with large VTS seems to offer no advantage to smaller (13 mL/kg ideal body weight) VTS. (Anesth Analg 1995;81:385-8)

Pharmacokinetics, pharmacodynamics, and dose-response relationships of pancuronium in control and elderly subjects.

Twenty-eight elderly patients (>75 years old) and 43 younger patients (25 to 60 years old) were studied to evaluate the effect of aging on the pharmacokinetics and pharmacodynamics of pancuronium. The pancuronium dose-response relationship and the duration of neuromuscular blockade after the administration of a single dose (70 to 100 μg/kg) were compared in the two groups. The plasma concentration-response relationship was established during recovery from paralysis. The pharmacokinetics of pancuronium were characterized after a single bolus dose by measuring plasma and urine concentrations of pancuronium fluorimetrically. The dose–response and plasma concentration–response relationships in elderly patients were comparable to that of the control group. The dose that caused 50 per cent paralysis averaged 39 ± 10 and 44 ± 12 μg/kg in control subjects and elderly patients, respectively. The plasma concentrations corresponding to a fixed degree of neuromuscular blockade were similar between the two groups. The time for recovery of the twitch tension to 25 per cent of the control value was prolonged from 44 ± 10 to 73 ± 22 min in the elderly patients. The recovery rate of the twitch from 25 to 75 per cent of the control value also was prolonged from 39 ± 13 to 62 ± 30 min in the elderly patients. The plasma clearance was decreased by 35 per cent in the elderly patients and caused a prolongation of the elimination half-life to 201 min as compared with 107 min in the younger adults. Urinary excretion of pancuronium was delayed in the elderly patients. It is concluded that pancuronium exerts a prolonged effect in elderly patients because of delayed elimination; the pharmacodynamics of pancuronium are not altered by aging.

Prolonged Neuromuscular Block from Mivacurium in Two Patients with Cholinesterase Deficiency

M ivacurium’s short duration of action, like the ultra-short action of succinylcholine, is due to its rapid hydrolysis by plasma cholinesterase (ChE); an inverse relationship has been found between ChE activity and the duration of action of mivacurium in phenotypically normal patients (1). Reports of prolonged paralysis from succinylcholine in the presence of ChE deficiency have been reported (2), and there has been a case report of prolonged mivacurium block in a patient with dermatomyositis and muscle weakness (3). The following two incidents of prolonged paralysis occurred during the evaluation phases of mivacurium; they were seen in separate institutions and managed with different approaches.

Relation between oxygen consumption and oxygen delivery in patients after cardiac surgery

The relative contributions of oxygen delivery (DO2) and oxygen extraction (O2ER) to the increase in cellular oxygen uptake (VO2) after cardiopulmonary bypass were studied prospectively in 36 patients after coronary artery bypass grafting (n = 18), valve replacement (n = 17), and removal of a left atrial tumor (n = 1). VO2 was calculated from the Fick equation and DO2 from thermodilution cardiac output and arterial oxygen content. During the first 24 h after cardiac surgery, there was a strong relation between VO2 and DO2 (VO2 = 28 + 0.27 x DO2, r = 0.79, P < 0.0001) but not between VO2 and oxygen extraction. Mixed venous oxygen saturation (SVO2) was usually reduced when cardiac index was below 2.0 L.min-1.m-2. Patients with a prolonged intensive care unit course (> 24 h) had lower cardiac index and lower SVO2 than the other patients. Therefore, the progressive increase in VO2 after cardiac surgery is accomplished primarily by an increase in cardiac output and DO2. It is usually when cardiac function is compromised that O2ER increases and SVO2 decreases.

Airway pressure changes during one-lung ventilation

This investigation analyzed the changes in inspiratory airway pressures during transition from two-lung to one-lung ventilation in patients tracheally intubated with a double-lumen endotracheal tube (DLT) using a classical method of intubation without fiberoptic bronchoscopy. All patients were anesthetized in a standardized fashion. Ventilation was accomplished with the Siemens 900 constant-flow mechanical ventilator (Solna, Sweden). Peak (Ppeak) and plateau (Pplateau) inspiratory airway pressures were recorded with an on-line respiratory monitor before and after clamping the tracheal limb of the DLT. The position of the DLTs was evaluated by fiberoptic bronchoscopy with the patient in supine position. Of the 51 intubations, the DLT was malpositioned in 15 cases (29.5%). Ppeak and Pplateau increased significantly when switched from two-lung ventilation to one-lung ventilation in both correctly and incorrectly positioned DLTs. When the DLT was in a correct position, Ppeak increased by a mean of 55.1% and Pplateau increased by a mean of 41.9%. When the DLT was malpositioned, this increase was significantly larger (74.9% and 68.8%, respectively). Three tests commonly used as markers of malpositioned DLTs were evaluated based on the data of this study, and it was established that, although the pressure differences related to position are statistically significant, as a single value, they cannot be used for clinical decision making. (Anesth Analg 1997;84:1034-7)

Intrinsic Positive End-Expiratory Pressure During One-Lung Ventilation for Thoracic Surgery: The Influence of Preoperative Pulmonary Function

OBJECTIVE To detect and to quantify intrinsic positive end-expiratory pressure (PEEPi) during thoracic surgery in the dependent lung of patients intubated with a double-lumen endotracheal tube (DLT) in the lateral position. METHODS Twenty consecutive patients undergoing elective pulmonary resection were anesthetized, paralyzed, and intubated with a DLT. Their lungs were ventilated (Siemens Servo 900 C ventilator; Siemens Elevna; Solna, Sweden) with constant inspiratory flow. Fraction of inspired oxygen, tidal volume (10 mL/kg), frequency (10/min), and inspiratory time/total time (0.33) were kept constant during the study. PEEPi and ventilatory data were measured in the dependent lung in the supine then in the lateral position with a closed hemithorax. The obtained data were analyzed according to the presence (group PH) or absence (group N) of pulmonary hyperinflation determined from the preoperative pulmonary function data as higher than 120% of predicted value of functional residual capacity (FRC) and residual volume (RV). DATA ANALYSIS In the dependent lung of patients in group PH (n = 11), PEEPi was present in the supine (n = 8) and in the lateral (n = 11) positions in the range of 1 to 10 cm H2O. In group N (n = 9), PEEPi was detected in one patient and only in the supine position. In the whole group of 20 patients, the preoperative value of FRC (% predicted) and RV (% predicted) was statistically significantly correlated to the presence of PEEPi, whereas the preoperative FEV1 (% predicted) was poorly related to PEEPi in both positions. There was no significant correlation between the value of PaCO2 and PEEPi during one-lung ventilation (OLV) but patients in group PH had a significantly higher PaCO2 during OLV than group N (p = 0.012). CONCLUSIONS In patients with chronic obstructive lung disease and pulmonary hyperinflation, PEEPi occurs commonly during the period of OLV and only occasionally in patients with normal lungs. As the ventilatory pattern, the size of DLT, and the side of surgery were similar in the two groups of patients, we conclude that the occurrence of PEEPi in our patients was influenced mainly by the preexisting pulmonary hyperinflation and airflow obstruction.

Visual Evaluation of Residual Curarization in Anesthetized Patients Using One Hundred-hertz, Five-second Tetanic Stimulation at the Adductor Pollicis Muscle

We were looking for a clinical test to indicate a train-of-four (TOF) ratio of approximately 0.9. We compared the adductor pollicis muscle (AP) visually evaluated response to ulnar nerve 100-Hz, 5-s tetanus (RF100 Hz) with the measured AP TOF ratio in 30 ASA physical status I or II adult anesthetized (propofol, sufentanil, N2O/O2) patients. After the induction of anesthesia, the left ulnar nerve was stimulated at the wrist (single twitch and TOF) and the resultant isometric force was measured. When TOF was assessed, the independent investigators, unaware of the left AP-measured TOF ratios, visually evaluated the presence or absence of AP fading elicited by right ulnar nerve 100-Hz, 5-s tetanus. The 30 patients were randomly allocated to receive either 0.5 mg/kg atracurium (n = 15) or 0.1 mg/kg vecuronium (n = 15). The neuromuscular blockade was allowed to resolve spontaneously. A multiple logistic regression analysis was performed by computing the 771 visual observations. The probabilities of success of 100-Hz, 5-s tetanus to detect TOF ratios of 0.8, 0.85, and 0.9 were 99%, 96%, and 67%, respectively. The sensitivity and specificity of 100-Hz, 5-s tetanus as an indicator of TOF ratios of 0.85 and 0.9 are 100% and 75%, 54% and 67%, respectively. We conclude that RF100 Hz visual assessment seems to be highly sensitive in evaluating residual paralysis, as the absence of RF100 Hz visual fading at the AP is compatible with a TOF ratio >0.85. Implications: After the administration of muscle relaxants, the absence of visual fading at the adductor pollicis, elicited in anesthetized patients by 100-Hz, 5-s tetanus, is compatible with a train-of four ratio >0.85. Therefore, clinical observation of fading after 100-Hz, 5-s tetanus seems to be a highly sensitive test in evaluating residual paralysis. (Anesth Analg 1998;87:185-9)

Intravenous dolasetron mesilate ameliorates postoperative nausea and vomiting

PurposeTo compare the efficacy, safety, and tolerability of dolasetron mesilate with placebo for the treatment of postoperative nausea and vomiting (PONV).MethodsIn a randomized, multicentre, double-blind, placebo-controlled study 337 adult patients undergoing surgery with general anaesthesia received one of four single, doses of dolasetron mesilateiv (12.5, 25, 50. or 100 mg) or placebo. Study medication was administered postoperatively when the patient reported nausea lasting 10 mm or when one emetic episode occurred within two hours of the patient’s arrival in the recovery room. Efficacy was assessed by the investigators over the 24-hr study penod by recording the number and timing of emetic episodes, the severity of nausea, the timing of administration of escape antiemetic medications. and patients’ and investigators’ satisfaction with antiemetic therapy.ResultsThe study sample was predominately women, and the surgical procedures were primarily gynaeco logical. All dolasetron mesilate doses produced higher complete response rates than placebo (P< 0.05). Only approximately one-third of dolasetron patients required escape antiemetic medication compared with more than 50% of patients in the placebo group. Both patient and physician satisfaction with dolasetron treatment was high. The most common adverse event was mild or moderate headache for both placebo-treated patients and dolasetron-treated patients. Clinical laboratory results were unremarkable.ConclusionSingle doses of dolasetron mesilateiv, given after the first episode of PONV were both effective and safe in this adult patient population.RésuméObjectifComparer l’efficacité, la sécurité et l’acceptabilité du mésilate de dolasetron avec celles d’un placebo pour le traitement des nausées et vomissements postopératoires (NVPO).MéthodesAu cours d’une étude multicentrique, en double aveugle, contrôlée par placebo. 337 adultes soumis à une chirurgie sous anesthésie générale ont reçu du mésilate de dolasetron à une de quatre posologies iv (12,5. 25. 50, ou 100 mg) ou un placebo. Le médicament était administré en postopératoire lorsque le patient se plaignait d’une nausée de durée 10 min ou quand au moins en épisode émétique survenait au cours des deux heures suivant l’arrivée du patient en salle de réveil. Sur une période d’étude de 24 h, l’efficacité était évaluée par les investigateurs par l’enregistrement du nombre et de la chronologie des épisodes, la gravité de la nausée, le temps de l’administration de la médication antiémétique de rattrapage, et la satisfaction du patient ou de l’investigateur envers le traitement.RésultatsL’échantillon de la population étudiée comprenait surtout des femmes et les interventions étaient surtout gynécologiques. Toutes les doses de mésilate de dolasetron procuraient une réponse complète plus fréquente que le placebo (P < 0,05). Seulement un tiers environ des patients sous dolasetron ont eu besoin d’un médicament antiémétique de rattrapage comparativement à plus de 50% du groupe placebo. La satisfaction du chirurgien et de l’anesthésiste à l’égard de la prévention réalisée par le dolasetron était élevée. Une céphalée légère ou modérée constituait la réaction défavorable la plus fréquente tant chez les patients sous placebo que sous dolasetron. Les résultats des examens de laboratoire étaient non significatifs.ConclusionChez une population adulte, les doses uniques de mésilate de dolasetroniv administrées après un premier épisode de NVPO sont à la fois efficaces et bien tolérées.

Variations in Pancuronium Requirement, Plasma Concentration, and Urinary Excretion Induced by Cardiopulmonary Bypass with Hypothermia

To determine the effects of cardiopulmonary bypass (CPB) and hypothermia on the neuromuscular blockade produced by pancuronium, this relaxant was infused intravenously into 10 anesthetized patients to produce and maintain 90% depression of the twitch tension of the adductor pollicis muscle following supramaximal ulnar nerve stimulation. Infusion rates, plasma concentration of pancuronium, and adductor pollicis temperature were measured every 15 min. During the normothermic period preceding the start of CPB, the pancuronium requirement, the pancuronium plasma concentration, and muscle temperature were (mean ± SEM): 238 ± 12 μg·m-2.15 min-1, 0.31 ± 0.01 μg/ml, and 33.9 ± 0.1 ° C, respectively. At the beginning of CPB, the pancuronium infusion rate increased to 362 ± 32 μg·m-2 15 min-1 (P < 0.001) despite a decrease in the muscle temperature to 29.2 ± 0.9° C (P < 0.001) and in pancuronium plasma concentration to 0.22 ± 0.02 μg/ml. During sustained muscle hypothermia to 28.3 ± 0.4° C the pancuronium plasma concentration remained constant at 0.22 ± 0.01 μg/ml (P < 0.001) while the requirement decreased to 94 ± 15 μg·m-2·15 min-1 (P < 0.001). After the muscle temperature was returned to 34 · 0.6° C, the plasma pancuronium concentration and requirements increased to 0.35 · 0.05 μg/ml and 392 · 32 μg·m-215 min-1 (P < 0.001), respectively. After CPB, these values were 0.39 · 0.04 μg/ml and 239 · 25 μg·m-2*15 min-1. These results demonstrate that pancuronium requirements are increased at the beginning of CPB because of circulatory volume changes and again during rewarming of the patient once muscle temperature reaches about 34° C.

Intravenous dolasetron mesilate in the prevention of postoperative nausea and vomiting in females undergoing gynecological surgery

STUDY OBJECTIVE To evaluate a range of doses of intravenous (i.v.) dolasetron mesilate, in preventing postoperative nausea and vomiting (PONV). DESIGN Double-blind, placebo-controlled, randomized, multicenter trial. SETTING Ten hospitals and/or surgical centers. PATIENTS 281 women undergoing gynecologic surgery with general anesthesia. INTERVENTIONS Patients received one of four single, i.v. doses of dolasetron mesilate (12.5 mg, 25 mg, 50 mg, and 100 mg) or placebo administered following cessation of anesthesia. MEASUREMENTS AND MAIN RESULTS Patients were monitored for 24 hours following study drug administration. The antiemetic efficacy of each dolasetron mesilate dose was evaluated by recording the number and timing of emetic episodes, and the effects on nausea were assessed by use of visual analog scales (VAS). Safety was assessed by adverse event reports, clinical laboratory tests, electrocardiographic (ECG) measurements, and monitoring vital signs. Complete responses (patients with no emetic episodes and no escape antiemetic medication requirements in 24 hours) were achieved by 54% in the 12.5-mg, 67% in the 25-mg, and 59% in both the 50-mg and 100-mg dolasetron mesilate dose groups, and by 43% in the placebo group. Nausea VAS assessments demonstrated that dolasetron-treated patients were significantly (p = 0.048) more likely to report no nausea (VAS score < 5 mm) than those in the placebo group. Adverse events reported generally were mild in intensity, and there were no clinically significant changes in laboratory tests, vital signs, or ECG parameters. CONCLUSIONS Dolasetron was effective and well tolerated for the prevention of PONV in female patients undergoing gynecologic surgery with general anesthesia.