Hypoglycemia (<60 mg/dL) was encountered in both the scenarios as depicted in Table 5. There was no statistically significant difference in the frequency of hypoglycemia either intraoperatively or postoperatively for the 2 scenarios. For the entire study population, intraoperative hypoglycemia was encountered in 12 patients (8 diabetic and 4 nondiabetic patients) and postoperative hypoglycemia in 29 patients (15 diabetic and 14 nondiabetic patients). Immediate postoperative hypoglycemia upon admission to a recovery area was observed in 5 patients. Postoperative hypoglycemia occurred in 23 of the 29 incidences during the first 12 hours of the postoperative phase. Severe hypoglycemia (<40 mg/dL) was observed in 2 patients intraoperatively and in 6 patients postoperatively.
Postoperative Glucose Levels in Diabetic Patients Without Intraoperative Glucose Management
Postoperative blood glucose levels were determined for diabetic patients who had no glucose management initiated intraoperatively (no intraoperative glucose measurement or insulin infusion). Only a subset of diabetic patients (n = 78) did not receive intraoperative glucose management. Among these patients, for those who had short (<2 hours) and long (≥2 hours) duration surgery, the mean postoperative glucose levels were 158 ± 47 mg/dL (n = 50) and 156 ± 36 mg/dL (n = 28), respectively. In addition, for both short- and long-duration cases, hyperglycemia was encountered half the time (48% for short and 57% for long cases).
Previous studies have shown that perioperative hyperglycemia could lead to postsurgical complications in both cardiac and surgery patients.1–10 However, most studies have focused on the effect of postoperative hyperglycemia on outcome, leaving the significance of glucose management during the shorter intraoperative phase unclear.1,3,7,8,10 Institutions generally extend their postoperative glucose management protocol to cover the intraoperative phase with the belief that adequate intraoperative glucose management could improve postoperative glucose levels. However, whether intraoperative glucose management has any significant effect on postoperative glucose levels is poorly understood. To specifically answer this question, we performed the current study. The study revealed that an elevated mean intraoperative glucose level is associated with higher mean postoperative glucose levels in surgery patients. Diabetes status and intraoperative steroid use had strong positive effects consistent with the reported literature.20 Age and BMI also had a positive effect on elevated postoperative glucose levels. Intraoperative hyperglycemia (>180 mg/dL) was associated with increased odds for postoperative hyperglycemia. Increased odds for postoperative hyperglycemia were observed even when intraoperative glucose levels exceeded 140 mg/dL. Diabetes status, higher BMI, and intraoperative steroid use favored the odds for postoperative hyperglycemia.
Multivariate models showed significant interactions between patient- and procedure-specific parameters and the association between intraoperative and postoperative glucose levels. The interactions were somewhat unexpected, and this makes the relationship between intraoperative and postoperative glucose levels complicated, as well as difficult to interpret. For example, the association between intraoperative glucose level and postoperative glucose levels is modified by the BMI. Because of this interaction, the association is amplified for patients with larger BMI and diminished for patients with smaller BMI. Future studies to estimate marginal treatment effect would be needed to appropriately apply the results of this study in clinical practice.
An elevated glucose level during surgery is commonly treated by initiating insulin infusion.19,21–23 However, when to initiate insulin remains unclear.12,15,18 Fear of hypoglycemia under anesthesia and an unclear target for optimal glucose management have perhaps created a variable practice pattern among anesthesia providers when it comes to intraoperative glucose management. The glucose management protocol in our institution recommends initiation of insulin treatment when the intraoperative glucose level exceeds 140 mg/dL. The results from this study seem to justify the choice of this threshold because starting insulin at a glucose level of 140 mg/dL was associated with lower postoperative glucose levels and fewer incidents of postoperative hyperglycemia. Furthermore, starting insulin early at this threshold did not increase the incidence of hypoglycemia.
This study was limited in scope to compare just intraoperative glucose management to postoperative glucose level. We did not explore whether adequate intraoperative glucose management improves postsurgical patient outcome. In addition, the association between postoperative glucose levels and postoperative outcome was not explored because this had already been performed by others previously.1,3,7,8,10 Intraoperative and postoperative blood glucose levels are affected by a variety of patient, surgical, anesthesia, and postsurgical factors. We attempted to compensate for confounding factors by adjusting for several patient and procedural risk factors in the statistical models. Whether other factors, such as compliance to institutional glucose control protocol, that were not considered in the statistical models may have influenced the results is unknown.
Perioperative insulin administration should be performed cautiously to prevent hypoglycemia. This is particularly true in the intraoperative setting where hypoglycemia is difficult to detect under anesthesia. In this study, although the frequency of occurrence of hypoglycemia was low, both intraoperative and postoperative hypoglycemia was still observed. Diabetes status did not predispose a patient to have hypoglycemia. There was also a greater tendency to have postoperative hypoglycemia during the first 12 hours of recovery.
Additional surgery and anesthesia-specific parameters that can affect perioperative glucose levels would need to be explored to better understand the risk factors for poor glycemic control. Examples would be the effects of the type and severity of diabetes and hemoglobin A1C level on intraoperative and postoperative glucose levels. An association between preoperative hyperglycemia and postsurgical complications has been shown in a study by Abdelmalak et al.24 In this context, it would be interesting to explore the effect of preoperative glucose levels on intraoperative and postoperative levels. Our study revealed that intraoperative steroid use is strongly associated with elevated perioperative glucose levels consistent with previous studies.20 However, withholding the use of steroids may not always be feasible because of clinical reasons such as postoperative nausea and vomiting prophylaxis and cerebral or airway edema reduction. Future studies exploring the dose-response relationship between steroid use and glucose levels may clarify the optimal use of steroids that balances its clinical need and effect on glucose levels.
In this study, we did not differentiate point-of-care and central laboratory glucose measurements in our analysis. Approximately 30% of the glucose measurements in the study came from point-of-care glucose meters. Although Rice et al.25 caution about the inaccuracies of self-monitored glucose meters in a perioperative setting, it should be noted that our institution uses an accurate point-of-care glucose meter that is approved for in-hospital use (ACCU-CHEK Inform II; Roche Diagnostics, Indianapolis, IN). Furthermore, the anesthesia providers were trained and certified to properly use these meters.
Consensus among anesthesia providers on what constitutes adequate intraoperative glucose control is poor because of a variety of reasons such as the fear of hypoglycemia during anesthesia, an unclear glucose target range for optimal patient outcome, and the varying effects of surgical stress and anesthesia management. Guidelines for intraoperative glycemic management remain nonstandard and poorly followed by anesthesia providers.12,15 Our study explored the question of whether intraoperative glycemic management affects postoperative glucose levels. The results indicate that adequate glucose management avoiding intraoperative hyperglycemia leads to better postoperative glucose levels and fewer incidences of postoperative hyperglycemia. In addition, our study highlights the importance of initiating insulin intraoperatively when the glucose level exceeds a threshold of 140 mg/dL and to administer an insulin dose targeted to avoid hyperglycemia. Early and adequate treatment of elevated intraoperative glucose levels provides a better “starting point” or lower starting glucose levels for postoperative glucose management.
Institutional Protocol for Intraoperative Glucose Management (the Target Glucose Range is 100–140 mg/dL)
Name: Bala G. Nair, PhD.
Contribution: This author is the primary investigator and the primary individual who performed the study design, conducted the study, analyzed the data, and prepared the manuscript.
Attestation: Bala G. Nair approved the final manuscript, attests to the integrity of the original data and the analysis reported in this manuscript, and is also the archival author.
Name: Mayumi Horibe, MD.
Contribution: This author is the co-investigator and helped with clinical advice, data analysis, and manuscript preparation.
Attestation: Mayumi Horibe approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript.
Name: Moni B. Neradilek, MS.
Contribution: This author helped with statistical study design and analysis, and assisted with manuscript preparation.
Attestation: Moni B. Neradilek approved the final manuscript and also attests to the integrity of the statistical analysis reported in this manuscript.
Name: Shu-Fang Newman, MS.
Contribution: This author helped with data extraction and processing from clinical information systems.
Attestation: Shu-Fang Newman approved the final manuscript.
Name: Gene N. Peterson, MD, PhD.
Contribution: This author is the clinical advisor for research study and assisted with manuscript preparation.
Attestation: Gene N. Peterson approved the final manuscript.
This manuscript was handled by: Sorin J. Brull, MD.
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© 2016 International Anesthesia Research Society
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