Pre-operative Elevated HbA1c associated with increased Infections after Spine surgeries

Preoperative Hb1Ac screening has substantial association with estimation of the risk to develop postoperative infections after elective spine procedures, as suggestied by a systemic review published in Clinical Neurology and Neurosurgery recently.

Spinal surgery (SS) is associated with early postoperative complications occurring in 4–16.4% of patients, which include surgical, medical and neurological complications. Early postoperative infections can complicate up to 9% of the cases  and implicate the need for revision surgeries, long - term use of intravenous antibiotics and finally - prolonged hospitalization resulting in higher economic costs. Infection rates may vary depending on the type and extent of surgery, use of instrumentation and patient’s characteristics.[5] Increased incidence of postoperative infections is reported in patients with a chronic state of impaired glucose metabolism. Infectious complications may present as local site infections with a diverse degree of severity (surgical site infections (SSI) - either superficial or deep subfascial infections with myonecrosis) as well as systemic infections such as pneumonia, urinary tract infection (UTI) or sepsis.

Prus et al, conducted a systematic review (SR) to report available clinical evidence on the relationship between increased preoperative HbA1c and early postoperative infections in patients undergoing spinal surgery. They found that 9n majority of selected studies, the elevated preoperative HbA1c associated with higher risk of postoperative infections (especially SSI’s) as well as non-infectious postoperative complications including: thrombotic events, acute kidney injury, delirium or anemia requiring transfusion. Patients with elevated HbA1c were also less likely to achieve functional improvement after the treatment and demonstrated higher incidence of re-admissions and the need for re-operation.

Optimising glucose metabolism should be pursued during all of the stages of preoperative period. Recent studies on a group of neurosurgery and orthopaedic patients state that proper management of intraoperative and postoperative hyperglycemia could also be beneficial in reducing the incidence of postoperative infections, however it is suggested, that chronic glucose metabolism disorders might be a more significant risk factor than acute episodes of hyperglycemia.

Studies included in present SR did not provide a consequent HbA1c threshold associated with elevated risk of postoperative infections as well as non-infectious complications in SS patients. The American Diabetes Association guidelines recommend maintaining HbA1c levels in DM patients below 7.0% prior to elective surgery to minimize the incidence of complications. In present SR the level above which a risk of postoperative infections differed between the studies and was reported as 6,65%  up to 8%.

Majority of the studies included in present SR investigated the incidence of postoperative complications in a subgroup of DM patients. However, available data indicate, that elevated levels of HbA1c can be found in a group of patients with no previous diagnosis of DM. Authors state, that up to 65,2% of study subjects self-reporting no diabetes were previously unaware of their metabolic derangement. This suggests that to reduce the risk of postoperative complications preoperative HbA1c testing should be considered even if no information on glucose metabolism disorders was found in patients medical records - especially in groups of patients with high risk of glucose metabolism disorders such as obese patients. Obesity strongly correlates with the incidence of DM. Furthermore it is an independent risk factor for postoperative infections following SS procedures. 

In conclusion the predominance of reported evidence suggest that preoperative Hb1Ac screening has substantial association with estimation of the risk to develop postoperative infections after elective spine procedures. This variable is also correlated with the risk for non-infective complications and postoperative functional outcome. There are controversies on the implementation of Hb1Ac testing as a part of routine preoperative assessment in patients scheduled for elective spine surgery. We may consider the possibility, that in patients with elevated HbA1c values the surgery may be postponed (in case of no concurrent neurologic deterioration) - to optimize the metabolic conditions and to implement specific therapeutic strategies to reduce metabolic derangement before surgery. Due to significant difference in the results of prospective and retrospective research in this area future studies should address the open controversies using an appropriate methodological design in a purposely dimensioned sample size projects.

Reference

Katarzyna Prus, Başak Akça, Federico Bilotta,

Preoperative glycated hemoglobin concentration and early postoperative infections in patients undergoing spinal surgery: A systematic review,

Clinical Neurology and Neurosurgery, Volume 233, 2023,

https://doi.org/10.1016/j.clineuro.2023.107938.