Jean-Yves Dupuis

Acute Kidney Injury After Cardiac Surgery Focus on Modifiable Risk Factors

Background— Acute kidney injury (AKI) after cardiac surgery is a major health issue. Lacking effective therapies, risk factor modification may offer a means of preventing this complication. The objective of the present study was to identify and determine the prognostic importance of such risk factors. Methods and Results— Data from a multicenter cohort of 3500 adult patients who underwent cardiac surgery at 7 hospitals during 2004 were analyzed (using multivariable logistic regression modeling) to determine the independent relationships between 3 thresholds of AKI (>25%, >50%, and >75% decrease in estimated glomerular filtration rate within 1 week of surgery or need for postoperative dialysis) with death rates, as well as to identify modifiable risk factors for AKI. The 3 thresholds of AKI occurred in 24% (n=829), 7% (n=228), and 3% (n=119) of the cohort, respectively. All 3 thresholds were independently associated with a >4-fold increase in the odds of death and could be predicted with several perioperative variables, including preoperative intra-aortic balloon pump use, urgent surgery, and prolonged cardiopulmonary bypass. In particular, 3 potentially modifiable variables were also independently and strongly associated with AKI. These were preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration. Conclusions— AKI after cardiac surgery is highly prevalent and prognostically important. Therapies aimed at mitigating preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration may offer protection against this complication.

The cardiac anesthesia risk evaluation score: a clinically useful predictor of mortality and morbidity after cardiac surgery.

BackgroundThe Cardiac Anesthesia Risk Evaluation (CARE) score is a simple risk classification for cardiac surgical patients. It is based on clinical judgment and three clinical variables: comorbid conditions categorized as controlled or uncontrolled, surgical complexity, and urgency of the procedure. This study compared the CARE score with the Parsonnet, Tuman, and Tu multifactorial risk indexes for prediction of mortality and morbidity after cardiac surgery. MethodsIn this prospective study, 3,548 cardiac surgical patients from one institution were risk stratified by two investigators using the CARE score and the three tested multifactorial risk indexes. All patients were also given a CARE score by their attending cardiac anesthesiologist. The first 2,000 patients served as a reference group to determine discrimination of each classification with receiver operating characteristic curves. The following 1,548 patients were used to evaluate calibration using the Pearson chi-square goodness-of-fit test. ResultsThe areas under the receiver operating characteristic curves for mortality and morbidity were 0.801 and 0.721, respectively, with the CARE score rating by the investigators; 0.786 and 0.710, respectively, with the CARE score rating by the attending anesthesiologists (n = 8); 0.808 and 0.726, respectively, with the Parsonnet index; 0.782 and 0.697, respectively, with the Tuman index; 0.770 and 0.724 with the Tu index, respectively. All risk models had acceptable calibration in predicting mortality and morbidity, except for the Parsonnet classification, which failed calibration for morbidity (P = 0.026). ConclusionsThe CARE score performs as well as multifactorial risk indexes for outcome prediction in cardiac surgery. Cardiac anesthesiologists can integrate this score in their practice and predict patient outcome with acceptable accuracy.

Amrinone and dobutamine as primary treatment of low cardiac output syndrome following coronary artery surgery: A comparison of their effects on hemodynamics and outcome

This study was undertaken in order to compare the effectiveness of amrinone and dobutamine as primary treatment of a low cardiac output (CO) after coronary artery bypass graft (CABG) surgery. Thirty patients with preoperative left ventricular dysfunction participated in this open-label randomized study. Patients were included if they failed to separate from cardiopulmonary bypass (CPB) without inotropic support or if they had a cardiac index (CI) less than 2.4 L/min/m2 after CPB regardless of the blood pressure, in the presence of adequate filling pressures. The treatment objectives were to separate from CPB and achieve a CI > or = 2.4 L/min/m2 and a mean arterial pressure > or = 70 mmHg. Patients treated with amrinone received 0.75 mg/kg followed by 10 micrograms/kg/min; when the objectives were not achieved within five minutes, another 0.75 mg/kg was given. Patients treated with dobutamine received an initial infusion of 5 micrograms/kg/min increased stepwise to 15 micrograms/kg/min if necessary. Eleven of 15 amrinone versus 6 of 15 dobutamine patients achieved the predefined treatment objectives with the test drug alone (P = NS). Comparisons of hemodynamics in patients treated solely with amrinone (n = 7) or dobutamine (n = 6) after CPB showed no significant differences between the treatment groups. The incidence of myocardial ischemia as detected by Holter monitor was 36% with amrinone and 33% with dobutamine. Two patients suffered ventricular fibrillation and two had significant supraventricular tachyarrhythmias (heart rate > 130/min) during treatment with dobutamine alone, whereas no significant arrhythmias occurred in the amrinone group (P = NS). Six dobutamine patients (40%) had postoperative myocardial infarction (MI) as opposed to none among the amrinone patients (P = 0.017). These results indicate that amrinone compares favorably with dobutamine as a primary treatment of low CO after CABG. Further study in a larger number of patients will be required in order to determine if the lower incidence of MI in the amrinone group was due to the treatment drug.

Atracurium and vecuronium interaction with gentamicin and tobramycin

Drug interactions between the aminoglycosides (tobramycin and gentamicin) and atracurium and vecuronium were studied prospectively in 44 patients. Twenty-two patients had therapeutic serum levels of tobramycin or gentamicin and 22 served as controls. Onset time, clinical duration, and time to spontaneous recovery of T4/T1 ratio of 0.70 after atracurium or vecuronium injection were measured. No statistically significant differences were found in onset time, but clinical duration and time to recovery were significantly longer in patients receiving tobramycin or gentamicin and paralyzed with vecuronium than for controls (P < 0.01 for clinical duration and P < 0.0005 for recovery). The neuromuscular block produced by atracurium was not significantly influenced by the presence of therapeutic serum levels of tobramycin or gentamicin. We conclude that for patients treated with these antibiotics, atracurium may present some advantages over vecuronium when a prolonged block is not desired.RésuméL’interaction entre les aminoglycosides (tobramycine-gentamicine) et le vécuronium ainsi que l’atracurium a été étudiée de façon prospective chez 44 patients dont 22 avaient des niveaux sanguins thérapeutiques de tobramycine ou de gentamicine et 22 constituaient des sujets témoins qui ne prenaient pas d’antibiotiques. Le début d’action, la durée clinique ainsi que le temps nécessaire pour une récupération du rapport T4/T1 à 0.70 ont été mesurés. Aucune différence statistiquement significative n’a pu être démontrée en ce qui a trait au début d’action des myorelaxants, mats les patients recevant de la gentamicine ou de la tobramycine à qui l’on a administré du vécuronium ont présenté des temps de récupération significativement plus longs que le groupe témoin (P<0.01 pour la durée clinique et P< 0.0005 pour le temps de récupération du rapport T4/T1 à 0.70). L’atracurium n’a pas semblé subir d’influence de la tobramycine ou de la gentamicine utilisés à un niveau thérapeutique. Nous concluons que pour des patients traités avec de la tobramycine ou de la gentamicine l’atracurium peut présenter certains avantages sur le vécuronium quand on veur éviter un bloc neuromusculaire prolongé.

Clinical, electrical and mechanical correlations during recovery from neuromuscular blockade with vecuronium

In order to détérmine correlations between electromyographic (EMG), mecanomyographic (MMG) and clinical criteria of adequate recovery from neuromuscular blockade with vecuronium, seven young healthy conscious volunteers were given subparalysing doses of vecuronium. During recovery from neuromuscular blockade, vital capacity, negative inspiratory pressure, peak expiratory flow rate and five-second head lift were assessed. Neuromuscular monitoring included the evoked EMG response of the adductor digiti minimi and the simultaneous evoked MMG response of the adductor pollicis on the same side. We found that all subjects maintained head lift for five seconds at EMG T4T1 of 0.70, and they achieved normal respiratory tests at EMG T4/T1 of 0.90. The MMG T4/T1 needed for the subjects to perform normal respiratory tests was found to be 0.50, at which time six of the seven subjects were able to perform adequately the head lift test.RésuméLa correlation entre l’électromyographie (EMG), la mécano-myographie (MMG) et des critères cliniques de récuperation adéquate suite à l’administration de doses sous-paralytisantes de vécuronium a été étudiée chez sept jeunes volontaires sains. Pendant la phase de récupération du bloc neuromusculaire, la capacité vitale, la force inspiratoire, le débit expiratoire de pointe et la capacité de maintien de la tête soulevée pour cinq secondes ont été évalués. Le monitorage neuromusculaire comprenait au niveau d’un même membre supérieur un EMG de l’adductor digiti minimi et un MMG de l’adductor pollicis. En ce qui a trait à l’EMG, tous les sujets ont réussi l’épreuve du maintien de la tête soulevée pour cinq secondes lorsque le rapport T4/T1 était de 0,70 et les tests de fonction respiratoire se sont avérés dans les limites normales lorsque le rapport T4/T1 était revenu à 0,90. Quant au MMG, six des sept sujets ont réussi le test du maintien de la tête soulevée pour cinq secondes lorsque le rapport T4/T1 etait de 0,50, alors que tous les tests de fonction respiratoire étaient revenus à la normale à ce momentlà.

Clinical assessment of the muscular response to tetanic nerve stimulation

The study was undertaken in order to determine clinical tactile evaluation of tetanic nerve stimulation (50 Hz, 5 sec) as a means of detecting fade and possible residual curarization. Forty-four patients were studied and 128 clinical evaluations by eight different observers were performed at various levels of neuro-muscular blockade. Tetanic fade was detected reliably by clinical evaluation only when high degrees of fade (tetanic fade ratio of 0.3 or less) were detected with a force-displacement transducer. We conclude that the clinical tactile assessment of the response to tetanic stimulation is not accurate except at very high degrees of fade and that its usefulness in monitoring neuromuscular recovery is doubtful.RésuméLa présente étude avail pour but de justifier l’évaluation tactile clinique de la réponse à la stimulation tétanique (50 Hz, 5 sec) comme moyen de détection d’un affaiblissement à cette stimulation télanique et d’une curarisation résiduelle possible. Quarantequatre patients ont étée étudiés et soumis à 128 évaluations cliniques de l’affaiblissement à la stimulation tétanique par huit observateurs différents, et ce à divers niveaux de bloc neuro-musculaire. L’affaiblissement tétanique n’a été détecté par i évaluation clinique que lorsque de hauls niveaux d’affaiblissement étaient objectivés au transducteur de force (rapport d’affaiblissement tétanique de 0,3 ou moins). Nous concluons que l’évaluation clinique tactile de la réponse à la stimulation tétanique n’est pas un moyen efficace de détection de l’affaiblissement tétanique et que son utilité comme moyen de monitorage de la récupération neuromusculaire peut être mise en doute.

Predicting New-Onset Postoperative Atrial Fibrillation in Cardiac Surgery Patients

OBJECTIVE To derive a simple clinical prediction rule identifying patients at high risk of developing new-onset postoperative atrial fibrillation (POAF) after cardiac surgery. DESIGN Retrospective analysis on prospectively collected observational data. SETTING A university-affiliated cardiac hospital. PARTICIPANTS Adult patients undergoing coronary artery bypass grafting and/or valve surgery. INTERVENTIONS Observation for the occurrence of new-onset postoperative atrial fibrillation. MEASUREMENTS AND MAIN RESULTS Details on 28 preoperative variables from 999 patients were collected and significant predictors (p<0.2) were inserted into multivariable logistic regression and reconfirmed with recursive partitioning. A total of 305 (30.5%) patients developed new-onset POAF. Eleven variables were associated significantly with atrial fibrillation. A multivariable logistic regression model included left atrial dilatation, mitral valve disease, and age. Coefficients from the model were converted into a simple 7-point predictive score. The risk of POAF per score is: 15.0%, if 0; 20%, if 1; 27%, if 2; 35%, if 3; 44%, if 4; 53%, if 5; 62%, if 6; and 70%, if 7. A score of 4 has a sensitivity of 44% and a specificity of 82% for POAF. A score of 6 has a sensitivity of 11% and a specificity of 97%. Bootstrapping with 5,000 samples confirmed the final model provided consistent predictions. CONCLUSIONS This study proposed a simple predictive score incorporating three risk variables to identify cardiac surgical patients at high risk of developing new-onset POAF. Preventive treatment should target patients ≥ 65 years with left atrial dilatation and mitral valve disease.

Pancuronium or vecuronium for treatment of shivering after cardiac surgery

This randomized double-blind study compared the hemodynamic and metabolic effects of pancuronium and vecuronium during treatment of shivering after cardiac surgery with hypothermic cardiopulmonary bypass. Thirty sedated and pain-free patients who shivered after cardiac surgery were treated with pancuronium (n = 15) or vecuronium (n = 15) 0.08 mg/kg. Baseline values of heart rate (HR), mean arterial pressure, arterial and venous blood gases, total body oxygen consumption indexed to body surface area (VO2-I), and pressure work index (PWI, an estimate of myocardial oxygen consumption) were measured on arrival in the intensive care unit, at onset of shivering, and repeatedly for 2 h after treatment. Continuous ST segment analysis of leads II and V5 were used for detection of myocardial ischemia. Treatment of shivering with pancuronium decreased VO2-I by 32% (P = 0.0001). This was accompanied by a 14% increase in HR (P = 0.001) and a 10% increase in PWI (P = 0.03). Vecuronium decreased VO2-I by 36% (P = 0.003) with a 4% decrease in HR (P = 0.04) and a 6% decrease in PWI (P = 0.06). Myocardial ischemia (n = 3) and ventricular arrhythmias (n = 3) occurred in five patients treated with pancuronium. Only one patient treated with vecuronium had ventricular arrhythmia (P = 0.08). Seven patients treated with pancuronium and eight treated with vecuronium were taking beta-adrenergic blockers preoperatively which was associated with lower HR (96 +/- 16 vs 109 +/- 15 bpm; P = 0.025) and lower PWI (8.8 +/- 1.2 vs 10.7 +/- 1.92 mL.min-1 x 100 g-1; P = 0.003) at onset of shivering. However, beta-adrenergic blockers did not attenuate the relative HR increase induced by pancuronium. No relationship was found between hypercapnia and tachycardia or hypertension. These results suggest that, when compared to pancuronium for treatment of postoperative shivering, vecuronium may be advantageous because it does not increase myocardial work. The disproportionate relationship between VO2-I and PWI after treatment with muscle relaxants indicates that increased VO2-I does not contribute significantly to the hemodynamic disturbances associated with shivering. These disturbances are more likely the results of increased adrenergic activity related to pain and recovery from anesthesia. Shivering and its associated hemodynamic disturbances appear to be concomitant but independent signs of awakening.

Noncardiac surgery in patients with coronary artery stent: what should the anesthesiologist know?

decrease coronary restenosis and abrupt vessel closure as compared to standard coronary balloon angioplasty.1–4 Consequently, they are implanted in most patients requiring percutaneous coronary intervention (PCI).5 One major consideration with coronary stents is their thrombogenicity at the blood-tissue interface which may cause local thrombosis or distal coronary embolization. Those complications are associated with a 50% incidence of acute myocardial infarction (MI) and a 20% mortality rate,6 making prevention of stent thrombosis mandatory in all cases. The most effective antithrombotic strategy involves the administration of aspirin and a thienopyridine (clopidogrel or ticlopidine) for a minimum period of four to six weeks for bare metal stents and several months for drug-eluting stents, until significant re-endothelialization of the stent has occurred. With this approach, stent thrombosis within 30 days of implantation occurs in less than 1% of patients who had an uncomplicated PCI.6 The perioperative management of a patient with recent coronary stent implantation represents an obvious challenge. On the one hand, the continuation of the combined antiplatelet therapy during the perioperative period may cause major bleeding; on the other, its early cessation may lead to coronary thrombosis, a complication enhanced by the procoagulatory effect of surgery. In their most recent guideline update for perioperative cardiovascular evaluation for noncardiac surgery, the American College of Cardiology (ACC) and the American Heart Association (AHA) recommended a delay of at least two weeks and ideally four to six weeks between stent implantation and noncardiac surgery (e.g., four full weeks of dual antiplatelet therapy during stent re-endothelialization and two weeks for the antiplatelet effect to wear off).7 There is no prospective controlled trial to support that recommendation. However, at least two retrospective studies provide convincing arguments for its rationale.8,9 In the first study, of 40 patients undergoing noncardiac surgery less than six weeks after coronary stenting, seven (18%) had an MI, 11 (28%) had major bleeding and eight (20%) died.8 All deaths and MIs, and eight of the 11 bleeding episodes occurred in patients who had surgery less than two weeks after coronary stenting. In the second study, eight (4.0%) of 207 patients who had surgery within two months of coronary stenting suffered an MI, of whom six (2.9%) died.9 All deaths and MIs occurred among the 168 patients who had surgery within six weeks of stent placement. No major adverse event occurred in the 39 patients operated seven to nine weeks after stent placement. Those two studies did not determine whether the acute ischemic complications were due to coronary stenting or to the increased inflammatory and procoagulable state of those patients and the presence of other vulnerable plaques. In addition, they did not test whether postponing of surgery could improve outcome or not. However, they clearly indicate that noncardiac surgery within six weeks of coronary stenting is associated with an increased risk of serious perioperative cardiac events. Considering the potential risk of noncardiac surgery shortly after coronary stenting, one may assume that most Canadian anesthesiologists are familiar with the ACC/AHA guidelines for management of this condition. However, the survey conducted by Patterson et al. and published in this issue of the Canadian Journal of Anesthesia suggests that this may not be true.10 Of the 996 anesthesiologists who responded to the questionnaire, 63% were unaware of any published guidelines on this topic. Despite this lack of knowledge, 56% of the anesthesiologists 356 EDITORIAL

Is tranexamic acid safe in patients undergoing coronary endarterectomy

BACKGROUND Patients undergoing coronary endarterectomy during coronary artery bypass grafting (CABG) are at increased risk of perioperative myocardial infarction due to coronary intimal disruption. Data assessing the safety of the antifibrinolytic drug tranexamic acid (TA) in patients undergoing this procedure are lacking. METHODS From September 1997 to December 1999, 221 patients underwent nonemergency primary CABG with endarterectomy of the right coronary artery alone in 149, the left anterior descending in 35, or both right and left anterior descending in 27. TA was administered intraoperatively to 87 patients (TA group: average total dose 62 +/- 4.4 mg/kg; range 20 to 109 mg/kg), and was not administered to 134 patients (No TA group). RESULTS The patient characteristics of the 2 groups were similar. In-hospital mortality consisted of 2 patients in the TA group and 4 patients in the No TA group. Perioperative myocardial infarction rates were 2% and 5% in the TA and No TA groups, respectively (p = 0.49). The relative risk for any type of perioperative cardiac ischemic event in the TA group versus the No TA group was 0.77 (95% CI; 0.4, 1.2). Patients in the TA group had a significant reduction in postoperative chest tube drainage (685 versus 894 mL in the TA versus No TA groups, respectively) and in the use of fresh-frozen plasma (p = 0.03). CONCLUSIONS These results suggest that the clinical effectiveness of tranexamic acid in reducing postoperative blood loss in patients undergoing coronary endarterectomy is not associated with a higher incidence of myocardial ischemia-related complications.