STUDY OBJECTIVE - The aim was to investigate whether heterogeneous coronary blood flow is maldistributed during endotoxin shock. DESIGN - Variables were studied before (t = 0) and at t = 90 and t = 120 min after bolus injection of saline (n = 6) or endotoxin (n = 6). SUBJECTS - 12 anaesthetised mongrel dogs, weight 20-27 kg, were used. MEASUREMENTS AND MAIN RESULTS - We studied myocardial blood flows in small tissue sections (of about 1 g in left and 2 g in right ventricle) with radioactive microspheres, together with haemodynamic variables and global myocardial metabolism. At t = 0 min in controls, regional flows per 100 g were heterogeneous and ranged from a factor 0.2 to 2.7 and 0.6 to 1.6 of mean flow per 100 g to the left and right ventricle respectively; heterogeneity was unchanged at t = 90 and t = 120 min. Between t = 0, t = 90, and t = 120 min regional flows correlated: r = 0.78(SD 0.14), n = 18, for left ventricle, and r = 0.70(0.17) for right ventricle. In the endotoxin group, cardiac output and mean arterial pressure decreased by 44(7) and 48(11)% respectively, and lactate increased by 3.2(0.6) mmol.litre-1 at t = 120 min. Global left ventricle blood flow and delivery and metabolism of O2 were unchanged; lactate extraction and external work fell. The ratio between global right ventricular O2 delivery and external work also rose. Regional blood flows ranged from a factor 0.2 to 2.7 and 0.1 to 1.8 of mean flow to left and right ventricles respectively; heterogeneity did not differ from controls and did not change with time. Flow correlations with time were reduced: 0.45(0.24) for left ventricle and 0.45(0.26) for right ventricle (both n = 18, p less than 0.005 v controls). The left ventricular endocardial to epicardial flow ratio fell; flow was redistributed to both layers. CONCLUSIONS - Heterogeneous blood flow is redistributed throughout the heart during canine endotoxin shock so that, at unchanged global blood flow and flow heterogeneity, flow decreases in some but increases in other areas. Flow maldistribution may be associated with focal ischaemia, which may be masked by a rise in O2 uptake for a given workload (contractile inefficiency) in overperfused areas, and may thereby contribute to a fall in global myocardial external work for a given O2 delivery.
SUMMARY. We have studied the effect of changes in pulse wave reflection on the configurations of pressure and flow in systemic and pulmonary circulation. Electromagnetic flow transducers, atrial catheters, and pacing leads were implanted in 10 dogs. In four animals, the flow transducer was placed on the pulmonary artery, in another four on the ascending aorta, and in two additional dogs on both vessels. One week later, ascending aortic and/or pulmonary artery flow and pressure (catheter tip manometer) were measured under general anesthesia (Nembutal, 30 mg/kg, iv). When the pulmonary circulation was studied (six dogs), measurements were made before and during serotonin infusion (0.5-0.75 mg/min). When the systemic circulation was studied (six dogs), measurements were made before and during nitroprusside infusion (50-200 jug/min). To quantify the arterial load, we calculated pulmonary and systemic input impedances. To estimate the amount of reflection, we used a reflection index which we defined as the amplitude ratio of reflected and forward wave. Nitroprusside decreased total peripheral resistance, increased total arterial compliance, and decreased the reflection index; similarity between aortic pressure and flow wave shapes increased, and they looked more like their pulmonary counterparts. Serotonin increased pulmonary vascular resistance, decreased pulmonary arterial compliance, and increased the reflection index. Resemblance of pressure and flow waves decreased. The differences in wave shapes can thus be explained by the amount of reflection: the less reflection the more pressure and flow resemble each other. (Circ Res 51: 479-485, 1982)
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