Effects of mannitol alone and mannitol plus furosemide on renal oxygen consumption, blood flow and glomerular filtration after cardiac surgery

An integrated clinical approach for the identification, prevention, and treatment of tumor lysis syndrome

Tumor lysis syndrome (TLS) is a potentially life-threatening metabolic disorder that occurs when tumor cells undergo rapid decomposition spontaneously or in response to cytoreductive therapy. Delayed recognition of the metabolic imbalances caused by the massive release of tumor cell contents may result in clinical complications such as acute kidney injury, seizures, and cardiac arrhythmias. Prevention, the key principle in TLS management, relies on the identification of patients at risk for developing TLS during chemotherapy or because of disease progression. TLS-related risk factors pertain to tumor type (particularly hematologic malignancies), specific tumor characteristics (e.g. bulky tumor, high cellular proliferation rate, sensitivity to cytoreductive therapy), and other host-related factors. A comprehensive grading system proposed by Cairo and Bishop classifies TLS syndromes into laboratory or clinical TLS, thus facilitating TLS prevention and management. The mainstays of TLS management include monitoring of electrolyte abnormalities, vigorous hydration, prophylactic antihyperuricemic therapy with allopurinol, and rasburicase treatment of patients at high TLS risk or with established hyperuricemia. Urine alkalinization and use of diuretics remain controversial clinical practices. In this review, we describe the incidence of, risk factors for, and diagnostic characteristics of TLS and summarize strategies for the prevention and management of TLS-associated metabolic abnormalities, particularly hyperuricemia. We specifically highlight recently published TLS management guidelines, which focus on the prevention of TLS and hyperuricemia based on a patient's level of risk, and the important role of nephrologists in the prevention and treatment of one of the most serious complications of TLS, acute kidney injury.

Low-dose vasopressin increases glomerular filtration rate, but impairs renal oxygenation in post-cardiac surgery patients

BACKGROUND

The beneficial effects of vasopressin on diuresis and creatinine clearance have been demonstrated when used as an additional/alternative therapy in catecholamine-dependent vasodilatory shock. A detailed analysis of the effects of vasopressin on renal perfusion, glomerular filtration, excretory function and oxygenation in man is, however, lacking. The objective of this pharmacodynamic study was to evaluate the effects of low to moderate doses of vasopressin on renal blood flow (RBF), glomerular filtration rate (GFR), renal oxygen consumption (RVO2) and renal oxygen extraction (RO2Ex) in post-cardiac surgery patients.

METHODS

Twelve patients were studied during sedation and mechanical ventilation after cardiac surgery. Vasopressin was sequentially infused at 1.2, 2.4 and 4.8 U/h. At each infusion rate, systemic haemodynamics were evaluated by a pulmonary artery catheter, and RBF and GFR were measured by the renal vein thermodilution technique and by renal extraction of 51chromium-ethylenediaminetetraacetic acid, respectively. RVO2 and RO2Ex were calculated by arterial and renal vein blood samples.

RESULTS

The mean arterial pressure was not affected by vasopressin while cardiac output and heart rate decreased. RBF decreased and GFR, filtration fraction, sodium reabsorption, RVO2, RO2Ex and renal vascular resistance increased dose-dependently with vasopressin. Vasopressin exerted direct antidiuretic and antinatriuretic effects.

CONCLUSIONS

Short-term infusion of low to moderate, non-hypertensive doses of vasopressin induced a post-glomerular renal vasoconstriction with a decrease in RBF and an increase in GFR in post-cardiac surgery patients. This was accompanied by an increase in RVO2, as a consequence of the increases in the filtered tubular load of sodium. Finally, vasopressin impaired the renal oxygen demand/supply relationship.