Length-dependent regulation of left ventricular function in coronary surgery patients

BACKGROUND: Load-dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine. METHODS: The study was performed in patients undergoing elective coronary surgery prior to cardiopulmonary bypass. High-fidelity LV pressure tracings (n = 25) and conductance LV volume data (n = 10) were obtained consecutively during leg elevation and after phenylephrine administration (5 microg/kg). RESULTS: Leg elevation resulted in a homogeneous increase in end-diastolic volume. The change in stroke volume (SV), stroke work (SW) and dP/dtmax was variable, with an increase in some patients but no change or a decrease in other patients. For a matched increase in systolic pressures, phenylephrine increased SW and dP/dtmax in all patients with no change in SV. Load dependence of relaxation (slope R of the tau-end-systolic pressure relation) was inversely related for changes in SV, SW, and dP/dtmax with leg elevation but not with phenylephrine. CONCLUSIONS: The different effects of leg elevation and phenylephrine suggest that the observed decrease in SV, SW, and dP/dtmax with leg elevation in some patients could not be attributed to an impaired contractile response to increased systolic LV pressures. Instead, load-dependent impairment of LV function after leg elevation appeared related to a deficient length-dependent regulation of myocardial functio

Dose dependent effect of aprotinin on rate of clot formation

Forty-eight patients scheduled for elective cardiac surgery were randomly assigned to receive aprotinin in the following doses: 0.2 mg kg-1 (group A), 0.7 mg kg-1 (group B), 1 mg kg-1 (group C) and 1.4 mg kg-1 (group D). Clot formation was analysed by thromboelastography immediately after induction of anaesthesia and again 30 min after administration of aprotinin. Rate of clot formation was assessed using R (reaction time = rate of initial fibrin formation), K (clot formation time = rate of fibrin build-up and cross linking) and angle of clot formation (denoting speed at which solid clot forms). Strength of the clot was assessed by maximal amplitude of clot formation (MA) and % lysis after 30 and 60 min. Significant reduction of R and K times and increase in angle of clot formation was observed in groups A and B. This effect was not apparent in the other groups. In group D, an increase in R time was noted. These findings indicate a dose-dependent effect of aprotinin on rate of clot formation with an earlier clot formation at low dose

Inferior vena cava diameter and central venous pressure correlation during cardiac surgery

OBJECTIVE: The purpose of this study was to determine whether a relationship exists between the inferior vena cava diameter (IVCD) or the superior vena cava diameter (SVCD) measured at the point of entry into the right atrium using transesophageal echocardiography (TEE) and the central venous pressure (CVP) under different experimental conditions. DESIGN: Prospective study. SETTING: University hospital, single institution. PARTICIPANTS: Seventy patients undergoing elective cardiac surgery. Interventions: CVP, IVCD, and SVCD were measured in a 2-dimensional, long-axis midesophageal bicaval view at end-diastole with electrocardiographic synchronization. Data were recorded during suspended ventilation, before and after leg elevation, and at different levels of positive end-expiratory pressure (0, 5, and 10 cmH(2)O). MEASUREMENTS AND MAIN RESULTS: The relationship between IVCD and CVP had 2 portions: A first (CVP 11 mmHg) in which the correlation was poor (R = 0.272, p = 0.065). No correlation between SVCD and CVP was observed. CONCLUSION: A strong correlation between TEE-derived IVCD measured at the point of entry into the right atrium and CVP was observed in cardiac surgical patients when CVP was <or=11 mmH