Author: Michael Vlessides
Intraoperative hyperglycemia is independently associated with postoperative delirium but not postoperative cognitive dysfunction, according to the results of a new study.
The German researchers behind the trial also found that the relative time spent in hyperglycemia may play a role in the development of postoperative delirium.
“We know that postoperative cognitive disorders, like the acute form of postoperative delirium and the long-term form of postoperative cognitive dysfunction, often occur after surgery, particularly in elderly patients,” said Gunnar Lachmann, MD, a clinician-scientist at CharitÉ–UniversitÄtsmedizin Berlin, in Berlin. “But we do not know much about intraoperative metabolic risk factors.
“We also know that perioperative hyperglycemia often occurs during surgery, also in the postoperative period, and this is associated with postoperative complications like increased infection rates and impaired immune function,” he said. “So we wanted to know if intraoperative hyperglycemia increases the risk of postoperative delirium and postoperative cognitive dysfunction.”
Screening for postoperative delirium was performed twice daily until postoperative day 7 using a variety of measures: the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; Nursing Delirium Screening Scale; Confusion Assessment Method (CAM); CAM-ICU; and chart review. The researchers also assessed patients for postoperative cognitive dysfunction three months after surgery.
Multivariable logistic regression analysis was used to analyze the influence of intraoperative hyperglycemia on both postoperative delirium and cognitive dysfunction. Secondary end points included the time of hyperglycemia, maximum glucose levels, and differences between diabetic and nondiabetic patients.
In a presentation at the 2019 annual meeting of the American Society of Anesthesiologists (abstract F2038), Dr. Lachmann explained that 1,354 measurements were obtained from the 87 participants, a median of 15 per patient. It was found that postoperative delirium was commonplace, occurring in 41 patients (47.1%). Postoperative cognitive dysfunction, on the other hand, was only observed in five of the 33 patients available for long-term follow-up (15.2%). “Unfortunately, we had a very high rate of patients lost to follow-up,” Dr. Lachmann said in an interview with Anesthesiology News.
Multivariable logistic regression revealed that hyperglycemia was significantly associated with postoperative delirium, with an odds ratio (OR) of 3.86 (95% CI, 1.13-39.49; P=0.044).
“This analysis showed that intraoperative hyperglycemia was associated with postoperative delirium, independent of age, sex, diabetes, ASA status, duration of surgery, type of surgery, mean intraoperative norepinephrine rate, and the lowest intraoperative hemoglobin level,” Dr. Lachmann said.
Nevertheless, hyperglycemia was not found to be associated with postoperative cognitive dysfunction (OR, 3.59; P=0.157).
Univariately, the relative time spent in hyperglycemia tended to be higher in postoperative delirium patients than in their counterparts who did not suffer the complication (P=0.075). Maximum glucose levels during surgery showed no differences between the two groups.
“We also found that among nondiabetic patients, the glucose maximum and the relative time spent in hyperglycemia were significantly higher in the postoperative delirium patients compared to nondelirium patients,” he said.
Given this association, Dr. Lachmann urged fellow anesthesiologists to avoid intraoperative hyperglycemia whenever possible. “This means that the anesthesiologist should measure glucose levels and prevent levels from rising over 150 mg/dL, while at the same time avoiding intraoperative hypoglycemia. It’s a fine balance.”
Glucose Control in the OR Is Difficult
For Boris Mraovic, MD, a professor of clinical anesthesiology at the University of Missouri, in Columbia, the study adds to growing evidence regarding the detrimental effects of hyperglycemia.
“Diabetes mellitus and hyperglycemia were previously reported as an independent predictor of postoperative delirium/postoperative cognitive dysfunction,” he said. “This observational study found that postoperative delirium, but not postoperative cognitive dysfunction, is associated with hyperglycemia. This is likely because a number of patients were lost to follow-up, leaving a small number of patients with postoperative cognitive dysfunction.”
Nevertheless, Dr. Mraovic noted that preventing perioperative hyperglycemia is a challenging task. “It should start with optimizing preoperative control, frequent intraoperative glucose measurement, and careful insulin management to avoid hypoglycemia, which could be more detrimental than an increase of blood glucose.”
Unfortunately, intraoperative glucose control is frequently omitted or neglected by clinicians. “This is likely because intraoperative hyperglycemia is clinically difficult to recognize, even in a very high range, unless blood glucose is measured,” Dr. Mraovic explained. “Also, complications from hyperglycemia are not seen immediately, but rather postoperatively.”