Dietary sodium intake of 10, 300, 600, 800, 1200, and 1500 mEq sodium/day were studied in 14 normotensive men (7 black, 7 white) following equilibration. Significant increases in mean arterial blood ...pressure (bp) were noted after sodium (Na) intake of 800 mEq/d. Bp increases were noted in blacks at lower levels and to a greater magnitude (21 mm Hg). Na loading suppressed plasma renin activity, aldosterone, and norepinephrine, and increased the cardiac index. Higher levels of Na intake increased potassium (K) loss. Another experiment replaced urinary K losses as they occurred in 6 subjects demonstrating attenuation of bp increases in response to dietary sodium loading. The potential role for Na and K in bp regulation in normotensive men was demonstrated and a connection was suggested between the development of hypertension in individuals predisposed to avid Na conservation. (kbc)
Alterations in intestinal permeability have been postulated to occur after thermal injury. We evaluated the status of intestinal permeability during the first 2 postburn weeks in 15 subjects by ...measuring the differential excretion of enterally administered lactulose and mannitol. The mean age and burn size of the patients were 32.7 +/- 3.6 years and 53.3% +/- 5.1% of the total body surface area, respectively. Ten healthy volunteers were also studied. The lactulose-mannitol excretion ratio was 0.159 +/- 0.017 for the patients and 0.017 +/- 0.003 for controls. The increased ratio did not correlate with burn size or postburn day. Patients who developed significant clinical infections during their first 2 postburn weeks had lactulose-mannitol ratios on postburn day 2 that were significantly higher than those of controls and patients who did not develop infections. This suggests a relationship between susceptibility to infection and early alterations in intestinal permeability.
The renal effects of low-dose dopamine (LDD) therapy in hyperdynamic thermally injured patients are unknown. We investigated the renal effects of LDD in ten burn patients (mean +/- SEM age and % ...total body surface burned: 30.2 +/- 3.3 years and 53.4% +/- 7%) and six controls (mean age; 20.2 +/- 0.5 years). Administration of LDD significantly increased glomerular filtration rate, effective renal plasma flow, sodium excretion, and urine flow in the controls and effective renal plasma flow, urine flow, heart rate, and cardiac index in the patients. The chronotropic effect of dopamine appears to be a principal contributor to the patients' increased effective renal plasma flow. Sodium excretion was increased by LDD only in the patients in whom the predopamine sodium excretion exceeded 5 mEq/h. Lack of a consistent natriuretic effect and the consistent chronotropic effect suggest that the routine use of low-dose dopamine in burn patients is unwarranted. The side effects that attend the desired response determine clinical use, i.e., the potential for blood flow redistribution and increased cardiac work demands must be balanced against increased renal plasma flow and natriuresis.
