Simple method for evaluating cardiac output.

This study compared the accuracy of a formula calculating cardiac output utilizing a patient size modification of a pulse pressure formula of Starr with that measured with a standard thermal dilution technique. During a six-month period 111 patients in the intensive care unit (ICU) on the cardiothoracic and vascular surgical services had comparison of their cardiac output by these two methods. The basic formula of Starr for stroke volume was converted to a stroke volume index by dividing by 1.7 and the empirically derived average body surface area in meters square. The stroke volume index was multiplied by the body surface area (BSA) of the patient to determine the patient's stroke volume in ml. Thus the modified stroke volume formula was 100-0.6 age-0.6 Diastolic Pressure + 0.5 Pulse Pressure x Patients BSA (m2)" over 1.7. Cardiac output was calculated by multiplying the stroke volume by heart rate. Nearly 60% of the patients had less than a 5% difference between the two methods, and over 90% had less than a 10% variance. In this particular population the highest variation was 18%. Thus, using only a carefully measured sphygmomanometer blood pressure, stroke volume and cardiac output can be determined with sufficient accuracy for clinical use.

A rapid hemodynamic monitor of acute ischemia during cardiac procedures: changes in relaxation via a continuous left ventricular pressure-derivative loop.

BACKGROUND: Procedures that induce ischemic pre-conditioning during cardiac surgery will require a rapidly visualized hemodynamic monitor of acute ischemia. This study investigated the utility of a continuous loop tracing of left ventricular pressure (LVP) plotted against its derivative (dP/dt) as a visual beat-to-beat monitor of acute changes in myocardial relaxation due to global ischemia. MATERIALS AND METHODS: In 11 dogs, LVP, recorded via a micromanometer-tip catheter, was plotted against dP/dt as a continuous loop. The angle of the loop during relaxation is inversely related to tau, the time constant of isovolumic relaxation. The angle was measured before and during: infusion of dextran to increase pre-load, infusion of nitroprusside to reduce after-load, and a 30-s occlusion of the left main coronary artery to induce temporary global ischemia. RESULTS: The relaxation angle of the loop did not change with dextran or nitroprusside infusion. During left main occlusion, the angle increased from 57 +/- 7 degrees to 92 +/- 3 degrees (P < 0.001), reflecting markedly impaired relaxation. In five of nine cases, the angle became greater than 90 degrees, rendering the monoexponential model of pressure decay inapplicable. However, the beat-to-beat progression of the angle could easily be followed visually. CONCLUSIONS: The LVP-dP/dt loop is a readily visualized, continuous display of beat-to-beat changes in myocardial relaxation. It provides a dynamic and specific display of immediate changes in relaxation during global ischemia, even when the exponential model of pressure decay is not applicable. The loop may be useful for guiding procedures that induce ischemic pre-conditioning or post-conditioning during cardiac surgery.

Sentinel nodal assessment in patients with carcinoma of the lung.

BACKGROUND: Assessment of sentinel nodes to predict metastases in a regional nodal basin is valuable for staging patients with melanoma and breast carcinoma. This study tested whether injection of isosulfan blue and technetium-99 could identify mediastinal sentinel nodes in patients with lung carcinoma and determine whether sentinel node histology predicts distal nodal metastases. METHODS: Isosulfan blue and technetium-99 were injected into the tumor and pulmonary resection performed. The hilum and mediastinum were assessed visually and with the gamma probe, and a mediastinal nodal dissection was performed. RESULTS: Thirty-one patients were evaluated. Three patients had positive sentinel nodes and positive distal mediastinal nodes. Twenty-two patients had negative sentinel nodes and negative distal nodes. No sentinel node was identified in 6 patients and 2 patients had two sentinel nodes. CONCLUSIONS: These data demonstrate that this rapid, simple technique can identify sentinel nodes in the mediastinum and that the sentinel node is an accurate predictor of distal nodal metastases in patients with lung cancer.

Findlay Implantable Two-Stage Centrifugal Pump.

The Findlay centrifugal pump is unique in its two-stage pumping mechanisms and in its complementary interrelationship of the stages to each other and to the exit system, and it forms an extremely efficient unit. The first stage is a lift force pump as an inlet. The second and major stage is a shear force pump. Twenty-six prototypes, many multiply modified, have been hand fabricated, and most have had classic pump function analyses. Six pumps have demonstrated minimal hemolysis (3.5-5 h). At modest rotation speeds, it pumps water up to 10 L/min. Forty-four acute studies in normal dogs have been performed with the Findlay pump in a ventricular assist system. Blood flows through the pump ranged from 1.2 to 4.5 L/min. The conclusion is that the Findlay pump has the ability to operate with low blood damage, performs at acceptable rotational speed with reasonable hydraulic and mechanical efficiency, and is small and implantable.