Letter to the Editor. Clinical relevance of preoperative hyperglycemia in patients undergoing elective craniotomy

We read with great interest the article of Zhang et al.1 on the association of preoperative hyperglycemia with postoperative 30-day mortality in pa tients undergoing elective brain tumor resection (Zhang Y, Tan H, Jia L, et al. Association of preoperative glucose concentration with mortality in patients undergoing cra niotomy for brain tumor. J Neurosurg. Published online October 28, 2022. doi:10.3171/2022.9.JNS221251). The authors concluded that even mild preoperative hypergly cemia (5.6–6.9 mmol/L) was associated with an increased mortality rate in this cohort. We are impressed by their remarkable results found in a large group of neurosurgical patients and grateful for their substantial efforts to raise awareness of the problem of perioperative blood glucose management. However, there are several issues that we would like to highlight to clarify the clinical relevance of the conclusion