Study: Vitamin D supplementation before surgery may reduce adverse outcomes
PHILADELPHIA — Patients with low blood levels of vitamin D are at increased risk of death and serious complications after noncardiac surgery, according to a study published Friday in Anesthesia & Analgesia.
"Vitamin D concentrations were associated with a composite of in-hospital death, serious infections and serious cardiovascular events," according to the new research by Alparslan Turan and colleagues of the Cleveland Clinic. They believe their results warrant further study to see if giving vitamin D supplementation before surgery can reduce the risk of these adverse outcomes.
The researchers analyzed the relationship between vitamin D level and surgical outcomes in approximately 3,500 patients who underwent operations other than heart surgery between 2005 and 2011. Only patients who had available data on vitamin D levels around the time of surgery — from three months before to one month afterward — were included in the study.
The concentration of vitamin D — specifically, 25-hydroxyvitamin D — in blood samples was analyzed as a risk factor for death, cardiovascular events or serious infections while in the hospital. The analysis included adjustment for other factors, such as demographic characteristics, medical conditions and type and duration of surgery.
Most patients did not meet the recommended 25-hydroxyvitamin D concentration of greater than 30 ng/mL. The median vitamin D level was 23.5 ng/mL — more than 60% of patients were in the range of vitamin D insufficiency (i.e., 10 ng/mL to 30 ng/mL). Nearly 20% had vitamin D deficiency (i.e., less than 10 ng/mL).
"Higher vitamin D concentrations were associated with decreased odds of in-hospital mortality/morbidity," the researchers wrote. For each 5 ng/mL increase in 25-hydroxyvitamin D level, the combined risk of death, cardiovascular events, or serious infections decreased by 7%.
Patients at the lowest level of 25-hydroxyvitamin D, less than 13 ng/mL, were at highest risk of death or serious complications. Those with higher vitamin D levels, up to 44 ng/mL, had about half the risk as those in the lowest group. The association with low vitamin D was statistically significant only for cardiovascular complications, although there were "strong trends" for mortality and infections.
However, Turan noted that the study had some important limitations — especially the fact that it included only patients who had recent measurements of vitamin D levels. They may represent a less healthy group, introducing a potential source of selection bias.
The study can't determine whether there is any cause-and-effect relationship between vitamin D levels and the risk of adverse outcomes. Turan and colleagues suggested a formal randomized trial to evaluate whether preoperative vitamin D supplementation can reduce the risk of serious complications and death after surgery.