Effects of clinically relevant acute hypercapnic and metabolic acidosis on the cardiovascular system: an experimental porcine study

INTRODUCTION: Hypercapnic acidosis (HCA) that accompanies lung-protective ventilation may be considered permissive (a tolerable side effect), or it may be therapeutic by itself. Cardiovascular effects may contribute to, or limit, the potential therapeutic impact of HCA; therefore, a complex physiological study was performed in healthy pigs to evaluate the systemic and organ-specific circulatory effects of HCA, and to compare them with those of metabolic (eucapnic) acidosis (MAC). METHODS: In anesthetized, mechanically ventilated and instrumented pigs, HCA was induced by increasing the inspired fraction of CO(2) (n = 8) and MAC (n = 8) by the infusion of HCl, to reach an arterial plasma pH of 7.1. In the control group (n = 8), the normal plasma pH was maintained throughout the experiment. Hemodynamic parameters, including regional organ hemodynamics, blood gases, and electrocardiograms, were measured in vivo. Subsequently, isometric contractions and membrane potentials were recorded in vitro in the right ventricular trabeculae. RESULTS: HCA affected both the pulmonary (increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR)) and systemic (increase in mean arterial pressure (MAP), decrease in systemic vascular resistance (SVR)) circulations. Although the renal perfusion remained unaffected by any type of acidosis, HCA increased carotid, portal, and, hence, total liver blood flow. MAC influenced the pulmonary circulation only (increase in MPAP and PVR). Both MAC and HCA reduced the stroke volume, which was compensated for by an increase in heart rate to maintain (MAC), or even increase (HCA), the cardiac output. The right ventricular stroke work per minute was increased by both MAC and HCA; however, the left ventricular stroke work was increased by HCA only. In vitro, the trabeculae from the control pigs and pigs with acidosis showed similar contraction force and action-potential duration (APD). Perfusion with an acidic solution decreased the contraction force, whereas APD was not influenced. CONCLUSIONS: MAC preferentially affects the pulmonary circulation, whereas HCA affects the pulmonary, systemic, and regional circulations. The cardiac contractile function was reduced, but the cardiac output was maintained (MAC), or even increased (HCA). The increased ventricular stroke work per minute revealed an increased work demand placed by acidosis on the heart

Action potential contour and inter-species differences

This editorial refers to ‘Action potential contour contributes to species differences in repolarization response to b-adrenergic stimulation’ by L. Sala et al., on pages 1543–1552

Action potential contour and inter-species differences

This editorial refers to ‘Action potential contour contributes to species differences in repolarization response to b-adrenergic stimulation’ by L. Sala et al., on pages 1543–1552

Action potential contour and inter-species differences

This editorial refers to ‘Action potential contour contributes to species differences in repolarization response to b-adrenergic stimulation’ by L. Sala et al., on pages 1543–1552

Ineffectiveness of hemoadsorption in large animals with abdominal sepsis: a randomized controlled porcine study

Abstract Objectives The use of hemoadsorption (HA) has become popular in the treatment of vasoplegic states associated with massive cytokine release, including septic shock. However, this approach does not seem to be based on robust evidence, and it does not follow international guidelines. To understand the pathophysiological rationale and timing of HA, we conducted a large animal septic shock experiment. Design Prospective randomized large-animal peritoneal septic shock experiment. Setting Laboratory investigation. Subjects Twenty-six anesthetized, mechanically ventilated, and instrumented pigs randomly assigned into (1) sham-operated group with HA (SHAM, n = 5); (2) sepsis animals without HA (SEPSIS, n = 5); (3) sepsis group with HA at norepinephrine initiation (EARLY, n = 8); and (4) sepsis group with HA initiated at norepinephrine rate reaching 0.5 μg/kg/min (LATE, n = 8). Interventions Peritoneal sepsis was induced by cultivated autologous feces inoculation. A CytoSorb cartridge (200 g) with a blood flow rate of 200 mL/min and heparin anticoagulation was used to perform HA. The animals received sedation and intensive organ support up to 48 h or until they experienced cardiovascular collapse. Measurements and main results Systemic hemodynamics, multiple-organ functions, and immune-inflammatory response were measured at predefined periods. The HA treatment was not associated with any measurable benefit in terms of systemic hemodynamics and organ support. The systemic inflammatory markers were unaffected by any of the treatment timings. In contrast, the HA resulted in higher vasopressor load and decreased 36-h survival (5 animals in SHAM (100%), 4 (80%) in SEPSIS, 4 (57%) in EARLY, and 2 (25%) in LATE; p = 0.041). The HA exposure in healthy animals was associated with hemodynamic deterioration, systemic inflammatory response, and cytopenia. Conclusions In this large-animal-controlled fulminant sepsis study, the HA was unable to counteract the disease progression in the early or advanced septic shock phase. However, findings from the HA-exposed sham animals suggest potential safety concerns

Heart-rate variability depression in porcine peritonitis-induced sepsis without organ failure

Depression of heart-rate variability (HRV) in conditions of systemic inflammation has been shown in both patients and experimental animal models and HRV has been suggested as an early indicator of sepsis. The sensitivity of HRV-derived parameters to the severity of sepsis, however, remains unclear. In this study we modified the clinically relevant porcine model of peritonitis-induced sepsis in order to avoid the development of organ failure and to test the sensitivity of HRV to such non-severe conditions. In 11 anesthetized, mechanically ventilated and instrumented domestic pigs of both sexes, sepsis was induced by fecal peritonitis. The dose of feces was adjusted and antibiotic therapy was administered to avoid multiorgan failure. Experimental subjects were screened for 40 h from the induction of sepsis. In all septic animals, sepsis with hyperdynamic circulation and increased plasma levels of inflammatory mediators developed within 12 h from the induction of peritonitis. The sepsis did not progress to multiorgan failure and there was no spontaneous death during the experiment despite a modest requirement for vasopressor therapy in most animals (9/11). A pronounced reduction of HRV and elevation of heart rate developed quickly (within 5 h, time constant of 1.97 ± 0.80 h for HRV parameter TINN) upon the induction of sepsis and were maintained throughout the experiment. The frequency domain analysis revealed a decrease in the high-frequency component. The reduction of HRV parameters and elevation of heart rate preceded sepsis-associated hemodynamic changes by several hours (time constant of 11.28 ± 2.07 h for systemic vascular resistance decline). A pronounced and fast reduction of HRV occurred in the setting of a moderate experimental porcine sepsis without organ failure. Inhibition of parasympathetic cardiac signaling probably represents the main mechanism of HRV reduction in sepsis. The sensitivity of HRV to systemic inflammation may allow early detection of a moderate sepsis without organ failure. Impact statement A pronounced and fast reduction of heart-rate variability occurred in the setting of a moderate experimental porcine sepsis without organ failure. Dominant reduction of heart-rate variability was found in the high-frequency band indicating inhibition of parasympathetic cardiac signaling as the main mechanism of heart-rate variability reduction. The sensitivity of heart-rate variability to systemic inflammation may contribute to an early detection of moderate sepsis without organ failure. </jats:sec