Author: Bob Kronemyer
Intraoperative vasopressor infusion to treat hypotension during complex spine surgery does not compromise renal function, according to a retrospective cohort analysis in Anesthesia & Analgesia (2019. [Epub ahead of print]).
“A few years ago, a couple of studies flagged the danger of using vasopressor infusion, as it was shown to be an independent risk factor for developing an acute kidney injury postoperatively,” said principal investigator Ehab Farag, MD, FRCA, FASA, a professor of anesthesiology at the Cleveland Clinic Lerner College of Medicine; the director of clinical research in anesthesiology at the Cleveland Clinic, in Ohio; and a member of the Anesthesiology News editorial advisory board. “However, we often use vasopressor infusion in complex spine surgery to maintain blood pressure, which can also decrease the fluid overload.”
The current study was undertaken to prove that vasopressor infusion is the main factor in maintaining blood pressure during complex spine surgery, and that such an infusion has a benign effect on the kidneys. “The objective is to maintain kidney perfusion and avoid fluid overload,” Dr. Farag said.
The study authors obtained data on 1,814 adult surgeries for complex spine surgery performed at the Cleveland Clinic’s main campus between January 2005 and September 2014. In total, 689 patients (38%) were given vasopressor infusion for at least 30 minutes during surgery, while the remaining 1,125 patients (62%) were not administered any vasopressor infusion.
In the same cohort, 540 patients with and 540 patients without vasopressor infusion were well matched on 32 potential confounding variables.
Among matched patients, the postoperative difference in mean estimated glomerular filtration rate was only 0.8 mL/min/1.73 m2.
Patients who received vasopressor infusion had more lengthy surgical times and were more prone to develop acute kidney injury, as they received more blood transfusion and hydroxyethyl starch (Hextend, BioTime) infusions than the control group. “Surprisingly, though, these patients had better urine output, which is a very good sign of a healthy kidney,” Dr. Farag said.
Based on the study, Dr. Farag encourages anesthesiologists to employ normovolemia with vasopressor infusion during noncardiac surgery to maintain appropriate perfusion pressure. Avoiding fluid overload and maintaining renal perfusion pressure are the key factors for avoiding acute kidney injury. “In fact, avoiding vasopressor infusion to tolerate hypotension is probably a poor strategy,” he said.
To improve outcomes with vasopressor infusion, Dr. Farag recommended a low dose to maintain the MSFP and normovolemia to enhance the venous return and tissue perfusions.
Senior investigator Daniel Sessler, MD, a professor and the chair of the Department of Outcomes Research at the Cleveland Clinic, said, “There are undoubtedly vasopressor doses that injure various organs, but extreme doses are typically restricted to critical care units and used in patients who are extremely ill.”
The study’s results suggest that mild to moderate doses of perioperative phenylephrine do not provoke renal injury, according to Dr. Sessler. “In contrast, there is substantial evidence that intraoperative hypotension is associated with renal and myocardial injury, and even death,” he said. There are also limited randomized data showing that preventing hypotension reduces major complications.
Ephedrine and norepinephrine, which increase cardiac output and tissue perfusion, “are theoretically preferable to phenylephrine,” Dr. Sessler said. “But there is no randomized data proving one vasopressor superior to another.”
Dr. Sessler said the optimal approach depends on the presumed etiology, which might include vasoplegia, inadequate vascular volume or myocardial dysfunction. “However, when vasoplegia is thought to be the cause, by all means use vasopressors rather than tolerate hypotension,” he said.