André Y. Denault

A Proposed Algorithm for the Intraoperative Use of Cerebral Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) is a technique that can be used as a noninvasive and continuous monitor of the balance between cerebral oxygen delivery and consumption. The authors develop and propose an algorithm for the use of NIRS based on optimizing factors that can affect cerebral oxygen supply/demand. These factors are the position of the vascular cannula, perfusion pressure, arterial oxygen content, partial pressure of carbon dioxide, haemoglobin, cardiac output, and the cerebral metabolic rate of oxygen. Dissemination of a useful treatment algorithm is the primary purpose of this article. Further multicenter studies are necessary to confirm the benefits and cost-effectiveness of this promising monitoring modality.

The right ventricle in cardiac surgery, a perioperative perspective: II. Pathophysiology, clinical importance, and management.

The importance of right ventricular (RV) function in cardiovascular disease and cardiac surgery has been recognized for several years. RV dysfunction has been shown to be a significant prognostic factor in cardiac surgery and heart transplantation. In the first article of this review, key features of RV anatomy, physiology, and assessment were presented. In this second part, we review the pathophysiology, clinical importance, and management of RV failure in cardiac surgery.

Diastolic dysfunction is predictive of difficult weaning from cardiopulmonary bypass.

: Diastolic function is receiving more attention since echocardiographic measurements were developed and have become widely available. The importance and significance of diastolic dysfunction (DD) observed before cardiac surgery and its relationship with adverse outcomes, such as difficult separation from cardiopulmonary bypass (CPB), have not been fully explored. In this study, we hypothesize that DD can be a predictor for the need of inotropic support to successfully separate from CPB. Ninety-two consecutive patients underwent surgery during the study period. Twenty-six patients were excluded. From the remaining 66 patients, 52 had coronary artery bypass grafting alone and 14 combined procedures, valvular surgery, and reoperations (redo). Systolic and diastolic function was evaluated by two experts blinded as to the clinical data except for the age. The evaluation of diastolic function was done according to published guidelines. The demographic, echocardiographic, and hemodynamic variables were entered in a logistic regression analysis to determine which variables were independent predictors of difficult separation from CPB and the need for postoperative vasoactive support. DD was present in 20 patients (30%). Patients with DD had lower weight (P = 0.046), less frequent coronary artery bypass grafting alone (P = 0.0004), more myocardial infarction before surgery (P = 0.02), higher regional wall motion score index (P = 0.0002), and larger left ventricle (P = 0.03). Total CPB time (P = 0.004) and ischemic time (P = 0.007) were longer in the DD group. Patients with DD required more frequent inotropic support at the end of surgery (P = 0.006) and up to 12 h after surgery (P = 0.003). Multivariate logistic regression identified female sex, DD, and total CPB time as predictive of difficult weaning and inotropic requirements up to 12 h after surgery.

Cerebral near-infrared spectroscopy in adult heart surgery: systematic review of its clinical efficacy.

PurposeThis systematic review is aimed at answering the following questions: 1) Is near-infrared spectroscopy (NIRS) clinically effective in detecting cerebral desaturation during heart surgery? 2) Are these results based on studies with solid methodology?SourcesMEDLINE, internet, and hand searches up to February 2004 for English and French papers on NIRS.Principal findingsForty-eight papers were retrieved, with a total of 5,931 cardiac surgery patients monitored by NIRS. More than 83% of patients underwent coronary artery bypass graft surgery. The majority of studies were prospective for the monitored group. Clinically, NIRS monitoring appears to detect brain desaturation episodes encountered during surgery. However, the majority of studies retrieved suffered from major methodological limitations and a low level of evidence. NIRS validity vs jugular bulb oximetry is questioned together with its predictive value in identifying those who will suffer postoperatively from neurological deficits. The sole randomized controlled trial appears to have recorded negative results in this respect.ConclusionThe clinical application of NIRS in heart surgery as a brain-monitoring device seems interesting. However, NIRS has to be investigated more rigorously to prove its clinical utility in cardiac surgery.RésuméObjectifRépondre à ces questions: 1) La spectroscopie par infrarouge (SPIR) est-elle efficace pour la détection clinique de la désaturation cérébrale en chirurgie cardiaque? 2) Les résultats sont-ils fondés sur une solide méthodologie des études?SourcesMEDLINE, Internet et une recherche manuelle jusqu’en février 2004 pour les articles en anglais et en français sur la SPIR. Constatations principales: Nous avons revu 48 articles, pour un total de 5931 interventions en cardiochirurgie avec monitorage par la SPIR. Plus de 83 % des patients avaient eu un pontage aortocoronarien. La majorité des études avec monitorage étaient prospectives. Du point de vue clinique, le monitorage avec la SPIR permet de détecter les épisodes de désaturation cérébrale survenus pendant la chirurgie. Cependant, la majorité des études avaient d’importantes limites méthodologiques et un faible niveau de preuve. La validité de la SPIR vs l’oxymétrie du bulbe jugulaire est mise en question, ainsi que sa valeur prédictive à détecter les patients qui vont souffrir de déficits neurologiques postopératoires. Le seul essai randomisé et contrôlé avait des résultats négatifs à cet égard.ConclusionL’application clinique de la SPIR en cardiochirurgie comme moniteur cérébral semble intéressante. Cependant, la SPIR doit être étudiée plus rigoureusement si on veut prouver son utilité clinique en chirurgie cardiaque.

The Right Ventricle in Cardiac Surgery, a Perioperative Perspective: I. Anatomy, Physiology, and Assessment

The importance of right ventricular (RV) function in cardiovascular disease and cardiac surgery has been recognized for several years. RV dysfunction has been shown to be a significant prognostic factor in heart failure, congenital heart disease, valvular disease, and cardiac surgery. In the first of our two articles, we will review key features of RV anatomy, physiology, and assessment. In the first article, the main discussion will be centered on the echographic assessment of RV structure and function. In the second review article, pathophysiology, clinical importance, and management of RV failure in cardiac surgery will be discussed.

Impact of routine use of intraoperative transesophageal echocardiography during cardiac surgery

PurposeTo determine the relative impact of each category-based TEE indication according to the ASA guidelines.MethodsIn 851 patients undergoing cardiac surgery, TEE clinical indications were classified as category I or II according to the ASA guidelines. Category 1 indications are patients in which TEE is considered useful and category II are those where TEE is potentially useful but indications are less clear. All TEE examinations were reviewed by two anesthesiologists with advanced training in TEE. For each patient, the clinical impact of TEE in the clinical management was assessed using five criteria: 1) change of medical therapy; 2) change in the surgical procedure; 3) confirmation of a suspected diagnosis; 4) positioning of an intravascular device, and 5) substitute to a pulmonary artery catheter (PAC).ResultsTEE had greater utility in category I than in category II indications (15/53 (28%)vs 110/798 (14%) respectively) (P < 0.01). The nature of the clinical impact was as follows: modification of medical therapy in 67/125 (53%), modification of planned surgical intervention in 38/125 (30%), confirmation of a diagnosis in 34/125 (27%). The impact on therapy was higher in complex surgical procedures (39%) than in valvular replacement (19%) (P < 0.01) and coronary artery bypass surgery (10%) (P < 0.001).ConclusionsOur findings validate the usefulness of the ASA practice guidelines demonstrating a greater impact of TEE on clinical management for category I indications than for category II. TEE also had a greater clinical impact in complex surgical procedures and in valvular replacement.RésuméObjectifDéterminer l’effet relatif de l’indication de l’ETO basée sur chacune des catégories relevant des recommandations ASA.MéthodeChez 851 patients devant subir une intervention chirurgicale cardiaque, les indications cliniques de l’ETO ont été classées en catégorie I ou II selon les recommandations de l’ASA. Dans la catégorie I, ce sont les patients pour qui l’ETO est considérée utile et dans la catégorie II, ceux pour qui l’ETO est probablement utile, les indications n’étant pas aussi claires. Tous les examens d’ETO ont été révisés par deux anesthésiologistes de formation poussée en ETO. Les répercussions cliniques de l’ETO sur le traitement clinique de chaque patient ont été évaluées selon cinq critères: 1) la modification du traitement médical 2) un changement de technique chirurgicale 3) la confirmation d’un diagnostic présumé 4) la mise en place d’un appareil intravasculaire 5) un substitut au cathéter de l’artère pulmonaire (CAP).RésultatsL’ETO a présenté une plus grande utilité avec les indications de catégorie 1 qu’avec celles de catégorie II (15/53 (28 %) vs 110/798 (14 %) respectivement) (P < 0,01). La nature de l’effet clinique a été : une modification de traitement médical chez 67/125 (53 %), un changement d’intervention chirurgicale chez 38/125 (30 %), la confirmation d’un diagnostic chez 34/125 (27 %). Les conséquences sur le traitement ont été plus grandes pour des interventions chirurgicales complexes (39 %) que pour le remplacement valvulaire (19 %) (P < 0,01) et le pontage aortocoronarien (10 %) (P < 0,001).ConclusionNos résultats confirment l’utilité des recommandations de pratique de l’ASA qui démontrent une plus grande influence de l’ETO sur le traitement clinique pour les indications de catégorie I que pour celles de catégorie II. L’ETO a aussi un effet plus important sur les interventions chirurgicales complexes et sur le remplacement valvulaire.

The Relationship Between Cerebral Oxygen Saturation Changes and Postoperative Cognitive Dysfunction in Elderly Patients After Coronary Artery Bypass Graft Surgery

OBJECTIVE The aim of this study was to evaluate the predictive value of cerebral regional oxygen saturation (rSO(2)) in the occurrence of postoperative cognitive dysfunction (POCD) in elderly patients undergoing coronary artery bypass graft (CABG) surgery. DESIGN A prospective study. SETTING University hospital. PARTICIPANTS A total of 61 patients (84% male) with a mean age of 70.39 ± 4.69 on a waiting list for CABG surgery were enrolled in the study. INTERVENTION A complete neurocognitive evaluation was performed 1 day before surgery as well as 4 to 7 days and 1 month after surgery. During surgery, rSO(2) was monitored continuously. MEASUREMENTS AND MAIN RESULTS POCD was defined as a reduction of 1 standard deviation on 2 or more neuropsychologic indices. Forty-six patients (80.7%) developed early POCD, and 23 (38.3%) showed late POCD. Patients whose rSO(2) decreased to less than 50% during the surgery experienced more POCD 4 to 7 days after surgery (p = 0.04). In addition, a decrease of more than 30% from the patients baseline rSO(2) was associated with POCD 1 month after surgery (p = 0.03). CONCLUSION Intraoperative cerebral oxygen desaturation is associated with early and late POCD in elderly patients. Cerebral oximetry is a promising tool in the prediction of subtle neuropsychologic deficits and further studies are needed.

Perioperative use of transesophageal echocardiography by anesthesiologists: Impact in noncardiac surgery and in the intensive care unit

BackgroundThe American Society of Anesthesiologists (ASA) has published practice guidelines for the use of perioperative transesophageal echocardiography (TEE) but the role and impact of TEE performed by anesthesiologists outside the cardiac operating room (OR) is still poorly explored. We report our experience in the use of TEE in the noncardiac OR, the recovery room and in the intensive care unit (ICU) in a university hospital, and analyze the impact of TEE on clinical decision making.MethodsTwo hundred fourteen patients were included and TEE indications were classified prospectively according to the ASA guidelines. The examinations and data sheets were reviewed by two anesthesiologists with advanced training in TEE. For each examination, it was noted if TEE altered the management according to five groups: 1) changing medical therapy; 2) changing surgical therapy; 3) confirmation of a diagnosis; 4)positioning of an intravascular device; and 5) TEE used as a substitute to a pulmonary artery catheter.ResultsEighty-nine (37%), 67 (31%) and 58 (27%) patients had category I, II and III indications. The impact was more significant in category I where TEE altered therapy 60% of the time compared with 31% and 21% for categories II and III (P < 0.001). The most frequent reason for changing management was a modification in medical therapy in 53 instances (45%).ConclusionOur results confirm a greater impact of TEE performed by anesthesiologists on clinical management for category I compared to category II and III indications in the noncardiac OR surgical setting and in the ICU.RésuméContexteL’American Society of Anesthesiologists (ASA) a publié lelignes directrices pour l’utilisation périopératoire de l’échocardiographie transœsophagienne (ETO), mais le rôle et l’impact de l’ETO réalisée par les anesthésiologistes à l’extérieur de la salle d’opération (SO) sont encore peu connus. Nous présentons notre expérience de l’usage de l’ETO dans une SO non cardiaque, dans la salle de réveil et à l’unité des soins intensifs (USI) d’un hôpital universitaire. Aussi, nous analysons l’impact de l’ETO sur la prise de décision en clinique.MéthodeDeux cent quatorze sujets ont participé à l’étude et les indications d’ETO ont été classifiées prospectivement selon les lignes directrices de l’ASA. Les examens et les fiches techniques ont été passées en revue par deux anesthésiologistes de formation avancée en ETO. Pour chaque examen, on a noté si l’ETO modifiait le traitement en regard de cinq groupes: 1) modification de la thérapie médicale 2) modification de la thérapie chirurgicale 3) confirmation du diagnostic 4) installation d’une sonde intravasculaire 5) usage de l’ETO comme substitut d’un cathéter artériel pulmonaire.RésultatsQuatre-vingt-neuf (37 %), 67 (31 %) et 58 (27 %) patients présentaient des indications de catégorie I, II et III. L’ETO a eu un impact plus significatif pour la catégorie I où elle modifiait la thérapie dans 60 % des cas comparativement à 31 % et à 21 % pour les catégories II et III (P < 0,001). C’est la modification de la thérapie médicale qui apparaît comme la raison principale de changement du traitement avec 53 cas (45 %).ConclusionNos résultats confirment une plus grande répercussion de l’ETO réalisé par les anesthésiologistes sur le traitement clinique pour les indications de catégorie I comparées à celles de catégories II et III dans le contexte chirurgical d’une SO non cardiaque et de l’USI.

The hemodynamically unstable patient in the intensive care unit: Hemodynamic vs. transesophageal echocardiographic monitoring

ObjectiveTransesophageal echocardiography is a diagnostic and monitoring modality. The objectives of our study were to compare the diagnoses obtained with continuous transesophageal echocardiography and hemodynamic monitoring in the intensive care unit, to determine interobserver variability of diagnosis obtained with both modalities, and to evaluate its impact. DesignProspective cohort study. SettingSurgical intensive care unit. PatientsConsecutive hemodynamically unstable patients after cardiac surgery. InterventionsAt admission, unstable patients were monitored during 4 hrs with transesophageal echocardiography and standard hemodynamic monitoring. The critical care physician evaluated the patients based on all information except the transesophageal echocardiography at 0, 2, and 4 hrs and formulated a hypothesis on the most likely cause of hemodynamic instability. Transesophageal echocardiography information was provided after each evaluation. To evaluate interobserver variability, all the hemodynamic and echocardiographic information was gathered, randomized, and evaluated by five clinicians for the hemodynamic data and five echocardiographers for the transesophageal echocardiography data. The evaluators were blinded to all other information. Kappa statistics were used to evaluate agreement. Impact of transesophageal echocardiography was assessed retrospectively by using the Deutsch scale. ResultsTwenty patients qualified for the study. The agreement between the hemodynamic and echocardiographic diagnosis showed a kappa at admission, 2 hrs, and 4 hrs of 0.33, 0.47, and 0.28. The interobserver agreement for the initial diagnosis (p = .014) and between all evaluators (p < .001) was significantly higher in the echocardiographic compared with the hemodynamic group. The transesophageal echocardiographic information was considered retrospectively to be essential in 34% and valuable in 34% of cases. ConclusionsThese observations support the belief that transesophageal echocardiographic monitoring in the intensive care unit is associated with higher interobserver agreement in diagnosing and excluding significant causes of hemodynamic instability for postoperative cardiac surgical patients.

Rapid Estimation of Left Ventricular Contractility from End-Systolic Relations by Echocardiographic Automated Border Detection and Femoral Arterial Pressure

Automated echocardiographic measures of left ventricular (LV) cavity area are closely correlated with changes in volume and can be coupled with LV pressure to construct pressure-area loops in real time. The objective was to rapidly estimate LV contractility from the end-systolic relations of cavity area (as a surrogate for LV volume) and femoral arterial pressure (as a surrogate for LV pressure) in patients undergoing cardiac surgery. Methods:Studies were attempted on 18 consecutive patients with recordings of LV pressure, LV area, and femoral arterial pressure on a computer workstation interfaced with the ultrasound system. End-systolic pressure-area relations (in terms of pressure-area elastance [E′es) from pressure-area loops during inferior vena caval occlusions were determined before and immediately after cardiopulmonary bypass using both LV and arterial pressure by semiautomated and automated iterative linear regression methods. Results:Data sets were available for 13 patients before and 8 patients after bypass (21 studies in 14 patients). E′es by arterial pressure was closely correlated with E′es by LV pressure: r=0.96, standard error of the estimate=2 mmHg/cm2, y=1.01 X -0.7 by the semiautomated method and r=0.94, standard error of the estimate=3 mmHg/cm2, y=1.02 X -0.5 by the automated method. Analysis of semiautomated and automated estimates of E′es from arterial pressure and E′es using LV pressure by the Bland-Altman method showed no systematic measurement bias and calculated limits of agreement of 8 and 9 mmHg/ cm2, respectively. Similar decreases in E′es by arterial and LV pressure occurred from before to after bypass in 7 patients with paired data sets: 32 ± 12 to 15 ± 6 mmHg/cm2 and 32 ±15 to 15 ± 7 mmHg/cm2, respectively (P<0.05 for both). Conclusions:On-line femoral arterial pressure and LV area data by echocardiographic automated border detection may be used to rapidly calculate E′es as a means to estimate LV contractility in selected patients.