Data on the cardiac output and circulatory dynamics obtained by cardiac catheter studies in 51 subjects with chronic severe anemia are presented. Patients are divided into two groups: group A consists of 26 subjects with an average hemoglobin value of 3.0 Gm. per 100 ml. (range 1.5 to 3.8 Gm.); group B, 25 patients with a hemoglobin level of 4.0 to 6.5 Gm., average 4.5 Gm. Group A subjects have a somewhat faster heart rate (99 against 92 a minute), higher cardiac index (8.0 versus 6.3 liters per minute per square meter), and stroke index (88 and 68 ml. per beat per square meter) than group B patients. The oxygen consumption values in both groups are normal (average 158 and 160 ml. per minute per square meter), while more oxygen is extracted by the tissue in group A subjects (61 and 53 per cent) whereas less oxygen is transported to the tissue (261 and 321 ml. per minute per square meter). The stroke volume seems to bear a closer relationship to the high cardiac output than such other parameters as heart rate, right heart filling pressure, and velocity of blood flow. Apparently the presence of slow heart rate does not negate high cardiac output. Data also suggest that systemic vascular resistance may play an important role in the high cardiac output as the two are inversely related, and by increasing the peripheral arterial pressure the output can be significantly reduced. Restudy data after the treatment of the anemia (hemoglobin 10.0 to 12.5 Gm. per 100 ml.) show appreciable reduction in the cardiac output and in the right heart filling pressure, increase in the peripheral vascular resistance and oxygen transport values, and widening of the arteriovenous oxygen differences with concomitant decrease in the oxygen extraction by the tissue.

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Guanethidine ("ismelin"), a potent hypotensive drug, is being increasingly employed in clinical practice (Page and Dustan, 1959;Dollery et al., 1960), and knowledge of its circulatory effects on the various manifestations of hypertension is essential. In this preliminary report we record the effects of intracardiac guanethidine on the cardiac output and circulatory dynamics in seven patients with hypertensive heart failure. They were studied as a preliminary to the proposed oral treatment with guanethidine. We also report the clinical response to guanethidine of these seven and another four unstudied cases of hypertensive failure treated for two to six months.Material and Method The clinical details of seven studied and four unstudied patients are outlined in Table I Fig. 1), reveal that cardiac index in three, heart rate in five, and stroke index in four patients only became normal at the end of 30 minutes after intracardiac guanethidine administration. In Case 5 the cardiac index, heart rate, and stroke index were unaffected, and in Case 7, although the cardiac index was unaltered, because of the slowing of the heart, the stroke index increased by 14%.Systemic

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