Guy Aya

Comparison of the diagnostic value of cardiac troponin I and T determinations for detecting early myocardial damage and the relationship with histological findings after isoprenaline-induced cardiac injury in rats

Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. The purpose of this study was to investigate the diagnostic value of cTnI and cTnT with regard to creatine kinase (CK) and lactate dehydrogenase (LD) and to determine whether they can be used for early diagnosis of myocardial damage in rats, and to examine the relationship between cTnl and cTnT release with histological examinations, using isoprenaline-induced cardiac muscle damage as an experimental model in the rat. Eighteen Wistar rats per group were treated with a single dose of either isoprenaline (iso) or with normal saline as a control group. The anti-cTnI and cTnT monoclonal antibodies (mAbs) employed in the cTnI (Access) and cTnT (Elecsys) assays cross-react with cTnI and cTnT of the rat. A highly significant rise of cTnl or cTnT was found already 2 h after iso. The time-courses of cTnI and cTnT were monophasic in form. The highest cTnI (mean+/-S.D., 1.1+/-2.3 ng/ml) and cTnT (mean+/-S.D. 3.6+/-30 ng/ml) were found 4 h after iso. cTnI and cTnT significantly increased in iso-treated rats in comparison with controls whether the differences between 2-, 4- and 6-h levels and basal levels were considered or not. The areas under cTnl and cTnT curves (AUC) (0-6 h) and the maximal cTnI and cTnT (0-6 h) after iso were significantly different from the controls. For CK and LD, no elevation in comparison with controls could be detected (except a trend for LD whether or not the difference between 6-h levels and basal levels were considered (P=0.08) and for LD AUC (0-6 h) (P=0. 059)). Correlations between maximal cTnI and cTnT and AUC were 0.69 (P=0.0001) and 0.60 (P=0.0066), respectively. Histological examinations of iso-treated rats revealed acute focal or multifocal myofibrillar degeneration of the myocardial tissue in ten out of 14 rats and showed the earliest alterations 4 h after iso in one treated rat. Only four of the controls exhibited evidence of mild changes and slight mononuclear cell infiltration. cTnl and cTnT peak values to at least 0.35 and 1.3 ng/ml, respectively, were necessary to detect histological myocardial cell injury after iso. cTnI and cTnT were found to be early markers for diagnosing iso-induced myocardial damage in comparison with CK and LD. Elevations of cTnI and cTnT appeared to relate to the severity of histologic changes after myocardial injury. Although there was a difference in the absolute concentration of results between cTnI and cTnT assays, due to a lack of standardization and heterogeneity in the cross-reactivities of mAbs to various troponin I and T forms, cTnI and cTnT can be used as easily measurable target parameters for detection of cardiotoxic and/or cardiodegenerative effects in rats.

Cardiac output measurement in critically ill patients: comparison of continuous and conventional thermodilution techniques

The purpose of the study was to compare cardiac output (CO) measurement by continuous (CTD) with that by conventional thermodilution (TD) in critically ill patients. In 19 of 20 critically ill patients requiring a pulmonary artery catheterism, 105 paired CO measurements were performed by both CTD and TD. Regression analysis showed that: CTD CO = 1.18 TD CO − 0.47. Correlation coefficient was 0.96. Bias and limit of agreement were — 0.8 and 2.4 L · min−1, respectively. When a Bland and Altman diagram was constructed according to cardiac index ranges, biases were −0.2 and −0.3 and −0.8 L · min−1 · m−2 and limits of agreement were 0.3, 0.7 and 1.6 L · min−1 · m−2 for low (<2.5 L · min−1 · m−2), normal (between 2.5 and 4.5 L · min−1 · m−2) and high (> 4.5 L · min−1 · m−2) cardiac indexes, respectively. It is concluded that CTD, compared with TD, is a reliable method of measuring CO, especially when cardiac index is ≤4.5 L · min−1 · m−2.RésuméCette étude avait pour but de comparer les mesures du débit cardiaque réalisées par thermodilution continue (CTD) par rapport à la thermodilution classique (TD) chez des patients de réanimation. Cent cinq paires de mesures du débit cardiaque ont été comparées chez 19 des 20 patients de réanimation inclus dans l’étude. L’équation de la droite de régression est CTD CO = 1,18 TD CO − 0,47. Le coefficient de corrélation s’élève à 0,96. L’erreur moyenne et l’intervalle de confiance sont respectivement de −0,8 et 2,4 L · min−1. En réalisant un diagramme de Bland and Altman selon le niveau d’index cardiaque, les erreurs moyennes s’élèvent à −0,2, −0,3 et −0,8 L · min−1 · m−2 et les intervalles de confiance à 0,3, 0,7 et 1,6 L · min−1 · m−2, respectivement pour les index cardiaques bas (<2,5 L · min−1 · m−2), normaux (entre 2,5 et 4,5 L · min−1 · m−2) et hauts (> 4,5 L · min−1 · m−2). La thermodilution continue, comparée à la thermodilution classique, est une méthode fiable pour le monitorage du débit cardiaque surtout pour les index cardiaque ≤4,5 L · min−1 · m−2.

Experimental model for comparative evaluation of pharmacologically induced vasodilation of arterial wall mechanical properties.

&NA; Arterial wall compliance (C) and distensibility coefficient (DC) are key factors of pathologic physiology, especially in arteries less than 2 mm in diameter. The aim of this study was to design an experimental model allowing comparative measurement of C and DC during pharmacologically induced vasodilation on small‐diameter arteries. Both femoral arteries were exposed in eight New Zealand White rabbits. Diameter (d) and systolic/diastolic diameter changes (&dgr;d) were measured simultaneously, and C and DC were calculated before and after topical application of 1 mL of 4% papaverine on the right side and topical application of 1 mL of 1% lidocaine on the left side. Diameter measurements were performed by echo tracking with 20‐MHz implanted microprobes. After papaverine and lidocaine application, respectively, d increased from 1.36 mm to 2.23 mm (P < 0.0001) and from 1.45 mm to 2.4 mm (P < 0.0001), &dgr;d increased from 0.0568 mm to 0.0571 mm (P = 0.34) and from 0.064 mm to 0.077 mm (P < 0.01), C increased from 5.7 × 10‐3 mm/mm Hg to 6 × 10‐3 mm/mm Hg (P < 0.02) and from 6.23 × 10‐3 mm/mm Hg to 8.49 × 10‐3 mm/mm Hg (P < 0.01), and DC decreased from 4.22 × 10‐3 mm Hg‐1 to 2.61 × 10‐3 mm Hg ‐1 (P < 0.0004) and from 4.36 × 10‐3 mm/mm Hg to 3.46 × 10‐3 mm/mm Hg (P < 0.005). Papaverine‐ and lidocaine‐induced changes were significantly different for &dgr;d, C, and DC (P < 0.01). These results suggest that, unlike that with papaverine, lidocaine‐induced vasodilation leads the artery up to the nonlinear part of its pressure/diameter relationship, with decreased distensibility contrasting with increased diameter and compliance. Our experimental model may be useful to compare the effects of different vasoactive drugs at different concentrations on the mechanical properties of the arterial wall.

Regional blood flows are affected differently by PEEP when the abdomen is open or closed: An experimental rabbit model

ObjectiveThe study of induced circulatory changes requires simultaneous assessment of multiple regional circulations because of interactions and compensatory mechanisms. Positive end expiratory pressure mechanical ventilation (PEEP) is known to cause marked, and potentially deleterious, cardiovascular changes. Our aim was to use a comprehensive approach to assess PEEP-induced circulatory changes in openvs closed abdomen animals.Material and methodsIn the anesthetized rabbit, we used implantable Doppler micro-probes to measure blood flow simultaneously in the ascending aorta, inferior vena cava, portal vein, hepatic artery, common carotid artery, and renal artery. We studied spontaneously breathing animals (Group A), and open (Group B) and closed abdomen (Group C) animals mechanically ventilated at 0 (ZEEP) and 12 cm H2O PEEP.ResultsIn Group A, all biological and hemodynamic variables remained unchanged for three hours at the end of the surgical procedure. In Groups B and C, ZEEP produced no significant hemodynamic change. PEEP induced a decrease in carotid, hepatic, and renal artery blood flow in Groups B and C, a decrease in heart rate and mean arterial blood pressure in Group B, and a decrease in aorta blood flow in Group C.ConclusionsThese experimental results demonstrate the usefulness of the comprehensive approach of circulatory changes, and confirm that PEEP may have deleterious effects on regional blood flow, even without significant change in cardiac output, especially when the abdomen is open.RésuméObjectifL’étude de changements circulatoires induits exige une évaluation simultanée de multiples circulations régionales à cause des interactions et des mécanismes compensateurs. La ventilation mécanique à pression télé-expiratoire positive (PTEP) cause des modifications cardio-vasculaires marquées, potentiellement nocives. Nous évaluons, selon une démarche globale, les changements circulatoires induits par la PTEP dans un abdomen animal ouvert vs fermé.MéthodeNous avons utilisé, chez un lapin anesthésié, des microsondes Doppler implantables pour mesurer le débit sanguin simultanément dans l’aorte ascendante, la veine cave inférieure, la veine porte, l’artère hépatique, l’artère carotide commune et l’artère rénale. Nous avons observé les animaux en respiration spontanée (Groupe A), et des animaux à l’abdomen ouvert (Groupe B) ou fermé (Groupe C) sous ventilation mécanique à 0 (ZEP) et 12 cm H2OPTEP.RésultatsDans le Groupe A, toutes les variables biologiques et hémodynamiques sont demeurées inchangées pendant trois heures après la fin de l’intervention chirurgicale. Dans les Groupes B et C, la ZEP n’a produit aucun changement hémodynamique significatif. La PTEP a provoqué une baisse du débit sanguin artériel carotide, hépatique et rénal chez les lapins des Groupes B et C, une baisse de la fréquence cardiaque et de la tension artérielle moyenne chez ceux du Groupe B et une baisse du débit sanguin aortique chez ceux du Groupe C.ConclusionCes résultats expérimentaux démontrent l’utilité d’aborder globalement les changements circulatoires et confirment que la PTEP peut provoquer des effets nocifs sur le débit sanguin régional, même sans modification significative du débit cardiaque, surtout lorsque l’abdomen est ouvert.

Cardiac Output Measurement in Critically Ill Patients: Comparison of Continuous and Conventional Thermodilution Techniques

The purpose of the study was to compare cardiac output (CO) measurement by continuous (CTD) with that by conventional thermodilution (TD) in critically ill patients. In 19 of 20 critically ill patients requiring a pulmonary artery catheterism, 105 paired CO measurements were performed by both CTD and TD. Regression analysis showed that: CTD CO = 1.18 TD CO - 0.47. Correlation coefficient was 0.96. Bias and limit of agreement were -0.8 and 2.4 L.min-1, respectively. When a Bland and Altman diagram was constructed according to cardiac index ranges, biases were -0.2 and -0.3 and -0.8 L.min-1.m-2 and limits of agreement were 0.3, 0.7 and 1.6 L.min-1.m-2 for low (< 2.5 L.min-1.m-2), normal (between 2.5 and 4.5 L.min-1.m-2) and high (> 4.5 L.min-1.m-2) cardiac indexes, respectively. It is concluded that CTD, compared with TD, is a reliable method of measuring CO, especially when cardiac index is < or = 4.5 L.min-1.m-2.