Association Between Changes in Norepinephrine Infusion Rate and Urinary Oxygen Tension After Cardiac Surgery

Abstract

To determine if the administration of norepinephrine to patients recovering from on-pump cardiac surgery is associated with changes in urinary oxygen tension (PO2), an indirect index of renal medullary oxygenation. Single center, prospective observational study. Surgical intensive care unit (ICU). A nonconsecutive sample of 93 patients recovering from on-pump cardiac surgery. In the ICU, norepinephrine was the most commonly used vasopressor agent (90% of patients, 84/93), with fewer patients receiving epinephrine (48%, 45/93) or vasopressin (4%, 4/93). During the 30-to-60-minute period after increasing the infused dose of norepinephrine (n=89 instances), urinary PO2 decreased by (least squares mean ± SEM) 1.8 ± 0.5 mmHg from its baseline level of 25.1 ± 1.1 mmHg. Conversely, during the 30-to-60-minute period after the dose of norepinephrine was decreased (n=134 instances), urinary PO2 increased by 2.6 ± 0.5 mmHg from its baseline level of 22.7 ± 1.2 mmHg. No significant change in urinary PO2 was detected when the dose of epinephrine was decreased (n=21). There were insufficient observations to assess the effects of increasing the dose of epinephrine (n=11) or of changing the dose of vasopressin (n <4). In patients recovering from on-pump cardiac surgery, changes in norepinephrine dose are associated with reciprocal changes in urinary PO2, potentially reflecting an effect of norepinephrine on renal medullary oxygenation.