Dopamine increases renal oxygenation: a clinical study in post-cardiac surgery patients.
BACKGROUND
Imbalance of the renal medullary oxygen supply/demand relationship can cause ischaemic acute renal failure (ARF). The use of dopamine for prevention/treatment of ischaemic ARF has been questioned. It has been suggested that dopamine may increase renal oxygen consumption (RVO(2)) due to increased solute delivery to tubular cells, which may jeopardize renal oxygenation. Information on the effects of dopamine on renal perfusion, filtration and oxygenation in man is, however, lacking. We evaluated the effects of dopamine on renal blood flow (RBF), glomerular filtration rate (GFR), RVO(2) and renal O(2) demand/supply relationship, i.e. renal oxygen extraction (RO(2)Ex).


METHODS
Twelve uncomplicated, mechanically ventilated and sedated post-cardiac surgery patients with pre-operatively normal renal function were studied. Dopamine was sequentially infused at 2 and 4 ug/kg/min. Systemic haemodynamics were evaluated by a pulmonary artery catheter. Absolute RBF was measured using two independent techniques: by the renal vein thermodilution technique and by infusion clearance of paraaminohippuric acid (PAH), with a correction for renal extraction of PAH. The filtration fraction (FF) was measured by the renal extraction of (51)Cr-EDTA.


RESULTS
Neither GFR, tubular sodium reabsorption nor RVO(2) was affected by dopamine, which increased RBF (45-55%) with both methods, decreased renal vascular resistance (30-35%), FF (21-26%) and RO(2)Ex (28-34%). The RBF/CI ratio increased with dopamine. Dopamine decreased renal PAH extraction, suggestive of a flow distribution to the medulla.


CONCLUSIONS
In post-cardiac surgery patients, dopamine increases the renal oxygenation by a pronounced renal pre-and post-glomerular vasodilation with no increases in GFR, tubular sodium reabsorption or renal oxygen consumption.
Redfors
Bengt
B
Department of Cardiothoracic Anesthesia and Intensive Care, Sahlgrenska University Hospital, Göteborg, Sweden.
Bragadottir
Gudrun
G
Sellgren
Johan
J
Swärd
Kristina
K
Ricksten
Sven-Erik
SE
D000042:Absorption; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects; D006348:Cardiac Surgical Procedures; D002406:Catheterization, Peripheral; D002860:Chromium Radioisotopes; D004298:Dopamine / Q000008:administration & dosage / Q000494:pharmacology*; D015259:Dopamine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004492:Edetic Acid; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007202:Indicators and Reagents; D007262:Infusions, Intravenous; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects; D007684:Kidney Tubules / Q000187:drug effects; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D019275:Radiopharmaceuticals; D012079:Renal Circulation / Q000187:drug effects; D012964:Sodium / Q000493:pharmacokinetics; D013318:Stroke Volume / Q000187:drug effects; D013815:Thermodilution; D014655:Vascular Resistance / Q000187:drug effects; D010130:p-Aminohippuric Acid
D002860:Chromium Radioisotopes; D015259:Dopamine Agents; D007202:Indicators and Reagents; D019275:Radiopharmaceuticals; D004492:Edetic Acid; D012964:Sodium; D004298:Dopamine; D010130:p-Aminohippuric Acid