THE CIRCULATORY RESPONSE TO A STANDARD POSTURAL CHANGE IN ISCHAeMIC HEART DISEASE

Abstract

A direct hemodynamic assessment of cardiac function in man is a desirable addition to a clinical appraisal of the cardiovascular system. Cardiac performance, however, involves many factors and while it is possible to analyse some of these in animal experiments, extensive investigations are not usually admissible in patients with ischmmic heart disease.McMichael and Sharpey-Schafer (1944) showed in normal subjects that by changing the posture from the upright to recumbent position the cardiac output and stroke volume were raised. These observations have been used as a basis for a test of myocardial function in which changes of cardiac output are measured by dye dilution and the photoelectric earpiece technique.The purpose of this paper is to describe such a test, to give the results when applied to normal subjects and to patients with ischaemic heart disease, and to discuss their significance in relation to the clinical findings. SUBJECTS AND METHODSStudies were carried out on 26 patients; 18 of these had suffered a myocardial infarction and 8 had no evidence of cardiovascular or debilitating disease. The ages are shown in the Table; with one exception those of the controls are comparable with those of the patients with ischoemic disease.In most cases the ischemic patients were convalescent following myocardial infarction and were undertaking only minor activities. In these, the investigation was made between two and six weeks after the acute episode. Two patients had recovered from infarction several months previously.Of the patients with ischoemic heart disease, 11 had been in cardiac failure previously, but at the time of the investigation only 6 had clinical evidence of failure; 7 were receiving treatment with digitalis with or without a diuretic. The patients were in sinus rhythm.A routine clinical examination, chest radiograph, and electrocardiogram were carried out in all patients. The diagnosis of myocardial infarction was accepted on the basis of a typical history and electrocardiographic abnormality.Two estimations of the cardiac output, pulse rate, and blood pressure were made with the patient resting quietly in a twenty degree feet down position on a tipping table. The position was then changed to the horizontal and the legs were raised to sixty degrees by means of a wooden support (Fig. IA and B). Two further measurements of cardiac output, pulse rate, and blood pressure were then made at three-minute intervals, the first of these being made three minutes after the change of posture. Cardiac output was estimated by an indicator dilution technique (Taylor and Shillingford, 1959;Thomas, Malmcrona, and Shillingford, 1964) using the photoelectric earpiece.* A known quantity (50 mg.) of Coomassie Blue dye was injected from a special syringe through a fine polythene cathetert inserted through a needle in the median antecubital vein and advanced into the great veins. The resultant dye dilution curve was calibrated in terms * Cambridge Instrument Co.

Passive leg raising predicts fluid responsiveness in the critically ill*

“…PLR induces a translocation of venous blood from the legs to the intrathoracic compartment (3,4), resulting in a transient increase in right ventricular (5) and left ventricular (6,7) preload. PLR as a "reversiblevolume challenge" (8) is attractive because it is easy to perform at the bedside, induces a reversible volume challenge that is proportional to body size, and does not result in volume overload in nonpreload-responsive subjects.…”

“…PLR as a "reversiblevolume challenge" (8) is attractive because it is easy to perform at the bedside, induces a reversible volume challenge that is proportional to body size, and does not result in volume overload in nonpreload-responsive subjects. The effects of PLR on cardiac output are variable (5,8,9), presumably depending on the existence of cardiac preload reserve. In this regard, our group previously proposed to predict fluid responsiveness in patients fully synchronized to their ventilator by examining the effects of PLR on pulse pressure, taken as a surrogate for stroke volume (10).…”

Bilateral passive leg raising attenuates and delays tourniquet deflation-induced hypotension and tachycardia under spinal anaesthesia

“…13 PLR has also been shown to increase both the right and left ventricular preload, leading to an increase in stroke volume and cardiac output. [14][15][16] Second, PLR can increase systemic vascular resistance, 17,18 which may attenuate the tourniquet's deflation-related reduction in systemic vascular resistance. 8 Third, when the tourniquet is deflated while the legs are elevated, the normally abrupt shift in flow back to the raised legs will be slower, as gravity counteracts the blood flow.…”

Preload Dependency Dynamic Indices

“…This maneuver comprises simultaneously lifting both of the patient's lower limbs to an angle of 45° to allow for the transfer of venous blood contained in the legs to the intrathoracic compartment [14]. This causes increased right ventricular [15] and then left ventricular preloads [16,17], and the result of this maneuver is similar to an autotransfusion, mimicking the effects of fluid expansion. This technique is well known among anesthetists and emergency doctors because it is an emergency maneuver used for patients in hypovolemic shock.…”