Perioperative Management of the Diabetic Patient: A Comprehensive Review

Dr Neeraj Manikath , claude.ai

Abstract

Diabetes mellitus affects approximately 10% of surgical patients and significantly impacts perioperative outcomes. The perioperative period presents unique challenges in glycemic management, requiring a delicate balance between preventing hyperglycemia-related complications and avoiding potentially catastrophic hypoglycemia. This review synthesizes current evidence on preoperative assessment, intraoperative glucose management, and postoperative care of diabetic patients undergoing surgery, with practical pearls for clinicians managing these complex cases.

Introduction

The prevalence of diabetes continues to rise globally, with an estimated 537 million adults living with the condition in 2021. Surgical patients with diabetes face increased risks of wound infections, cardiovascular complications, acute kidney injury, and prolonged hospital stays. Optimal perioperative glycemic control can mitigate these risks, yet achieving this balance remains challenging. This review provides evidence-based recommendations for managing diabetic patients throughout the surgical journey.

Preoperative Assessment and Risk Stratification

Glycemic Control Assessment

The preoperative evaluation begins with assessing baseline glycemic control. Hemoglobin A1c (HbA1c) provides insight into average glucose levels over the preceding 3 months and correlates with postoperative complications. Studies demonstrate that HbA1c levels above 8% are associated with increased infection rates and delayed wound healing.

Pearl: An HbA1c >8% suggests suboptimal control, but elective surgery should rarely be postponed solely for optimization in asymptomatic patients, as the delay itself carries risks. The decision must weigh surgical urgency against potential benefits of optimization.

Evaluating Diabetes-Related Complications

A thorough assessment of end-organ damage is essential:

Cardiovascular System: Diabetic patients have a 2-4 fold increased risk of perioperative cardiac events. Silent ischemia is common due to cardiac autonomic neuropathy. Consider stress testing or coronary angiography for patients with poor functional capacity or multiple cardiac risk factors undergoing intermediate to high-risk surgery.

Renal Function: Baseline creatinine and estimated glomerular filtration rate (eGFR) guide perioperative fluid management and medication dosing. Patients with diabetic nephropathy are particularly vulnerable to contrast-induced nephropathy and volume depletion.

Autonomic Neuropathy: Cardiac autonomic neuropathy increases the risk of intraoperative hemodynamic instability, silent myocardial ischemia, and sudden cardiac death. Gastroparesis affects aspiration risk and timing of preoperative fasting.

Oyster: Test for cardiac autonomic neuropathy using simple bedside maneuvers: heart rate variability with deep breathing (should increase by ≥15 bpm), heart rate response to standing (30:15 ratio), and blood pressure response to standing. Abnormal findings should heighten perioperative vigilance.

Preoperative Medication Management

Oral Hypoglycemic Agents

Metformin: Traditionally held 24-48 hours before surgery due to lactic acidosis concerns, though actual risk is extremely low in patients with normal renal function. Current guidelines suggest continuing metformin until the night before surgery in patients with eGFR >60 mL/min/1.73m².

Sulfonylureas and Meglitinides: Hold on the day of surgery due to prolonged half-lives and hypoglycemia risk, especially during fasting periods.

SGLT-2 Inhibitors: Discontinue at least 3-4 days before surgery. These agents increase the risk of euglycemic diabetic ketoacidosis (DKA), particularly during periods of reduced oral intake and physiological stress. Case reports of perioperative euglycemic DKA have raised significant safety concerns.

Hack: Remember "STOP 3" for SGLT-2 inhibitors: Stop at least 3 days before surgery to minimize DKA risk. If emergency surgery is needed in a patient recently taking SGLT-2 inhibitors, check beta-hydroxybutyrate regardless of glucose levels.

DPP-4 Inhibitors: Generally safe to continue through surgery with low hypoglycemia risk. Can be resumed once oral intake resumes.

GLP-1 Receptor Agonists: Recent FDA warnings highlight delayed gastric emptying and aspiration risk. Consider holding for one week (weekly formulations) or 24 hours (daily formulations) before elective procedures. Anesthesiologists should be informed if taken recently.

Insulin Management

Type 1 Diabetes: Never completely discontinue basal insulin. These patients lack endogenous insulin production and will develop DKA without exogenous insulin, even if not eating.

Pearl: For Type 1 diabetics undergoing surgery, give at least 50-80% of usual basal insulin on the morning of surgery, even if NPO. This is non-negotiable and can be life-saving.

Type 2 Diabetes on Insulin:

• Long-acting basal analogs (glargine, detemir, degludec): Give 75-80% of usual morning dose
• NPH insulin: Give 50% of usual morning dose due to variable absorption and peak effect
• Pre-mixed insulins: Hold the morning dose
• Rapid-acting insulin: Hold until eating resumes

Intraoperative Glucose Management

Target Glucose Ranges

Current evidence supports moderate glycemic control during surgery. The NICE-SUGAR study demonstrated that intensive glucose control (81-108 mg/dL) increased mortality compared to conventional control (144-180 mg/dL) in critically ill patients. For surgical patients, target ranges of 140-180 mg/dL balance complication prevention with hypoglycemia avoidance.

Hack: Think "140-180" for intraoperative and ICU glucose targets. For cardiac surgery patients, slightly tighter control (110-150 mg/dL) may be beneficial based on Portland Diabetic Project data, though this requires experienced protocols.

Insulin Infusion Protocols

For prolonged procedures or poor glycemic control, intravenous insulin infusions provide precise, titratable control. Standard protocols use regular insulin infusion with hourly glucose monitoring:

• Initial rate: 0.5-1 units/hour for glucose 140-180 mg/dL
• Adjust based on glucose trends and rate of change
• Always administer insulin with dextrose-containing fluids to prevent hypoglycemia

Pearl: The "Rule of 1500": Divide 1500 by total daily insulin dose to estimate how much 1 unit of insulin lowers glucose in mg/dL. This helps predict insulin sensitivity and adjust infusion rates appropriately.

Subcutaneous Sliding Scale Caution

Traditional sliding scale insulin alone is reactive rather than proactive and associates with worse outcomes. If used, always combine with basal insulin to prevent rebound hyperglycemia.

Postoperative Management

Monitoring Frequency

• Immediate postoperative period: Every 1-2 hours until stable
• Stable ward patients: Before meals and bedtime (minimum 4 times daily)
• ICU patients: Hourly if on insulin infusion
• Consider continuous glucose monitoring (CGM) for high-risk patients, though regulatory approval for hospital use varies

Transitioning from IV to Subcutaneous Insulin

When transitioning from insulin infusion to subcutaneous insulin:

1. Calculate total insulin received in previous 24 hours from infusion
2. Give 80% of this amount as total daily subcutaneous dose
3. Divide as: 50% basal insulin, 50% nutritional/correctional insulin
4. Overlap IV and subcutaneous insulin by 2-4 hours to prevent hyperglycemia

Hack: The "80-50-50 rule" - Take 80% of 24-hour IV insulin total, give 50% as basal, 50% as bolus insulin divided across meals.

Managing Stress Hyperglycemia

Patients without known diabetes may develop hyperglycemia perioperatively due to surgical stress, medications (steroids), and counter-regulatory hormones. This "stress hyperglycemia" associates with worse outcomes even in non-diabetics.

• Treat glucose persistently >180 mg/dL
• Screen for underlying diabetes with HbA1c
• May resolve after acute stress; reassess need for treatment at discharge

Postoperative Complications

Hypoglycemia: More immediately dangerous than hyperglycemia. Symptoms may be masked by anesthesia, analgesia, or critical illness. Maintain high suspicion and treat glucose <70 mg/dL promptly.

DKA and HHS: Can occur postoperatively, especially in Type 1 diabetes or with physiologic stress. Check ketones if glucose >300 mg/dL or patient appears ill despite normal glucose (euglycemic DKA).

Pearl: Postoperative DKA may present atypically. Maintain low threshold for checking beta-hydroxybutyrate, especially in patients who recently took SGLT-2 inhibitors or had poor oral intake.

Special Surgical Scenarios

Cardiac Surgery

Cardiac surgery patients benefit from tighter glycemic control. Continuous insulin infusions with glucose targets of 110-150 mg/dL reduce sternal wound infections and atrial fibrillation. The Portland Protocol demonstrated improved outcomes with this approach, though it requires dedicated nursing protocols.

Bariatric Surgery

Bariatric surgery uniquely treats diabetes through weight loss and metabolic changes. Many Type 2 diabetics achieve remission postoperatively. Aggressive diabetes medication reduction is necessary to prevent hypoglycemia as insulin sensitivity improves rapidly. Some patients can discontinue all medications within days of surgery.

Ambulatory Surgery

Day surgery patients pose unique challenges with limited monitoring windows:

• Prioritize morning scheduling
• Ensure stable glucose on arrival (100-180 mg/dL ideal)
• Have clear protocols for hypoglycemia/hyperglycemia before discharge
• Provide explicit instructions for resuming medications
• Consider later discharge with confirmed meal tolerance

Hack: For morning ambulatory cases, have Type 2 diabetics hold morning oral medications but eat a light early breakfast. This prevents hypoglycemia while avoiding excessive hyperglycemia.

Emerging Evidence and Future Directions

Continuous Glucose Monitoring

CGM systems show promise for hospital use, providing real-time glucose trends and reducing nursing workload. Several studies demonstrate feasibility and accuracy comparable to point-of-care testing. Regulatory approval for inpatient CGM use continues expanding.

Technology-Driven Insulin Dosing

Computerized insulin dosing algorithms and decision support systems reduce dosing errors and improve glucose control. Integration with electronic medical records enables safer insulin management.

Preoperative Optimization Programs

Multidisciplinary preoperative optimization clinics that address diabetes control, cardiovascular risk, and nutritional status show promise in reducing complications and length of stay.

Clinical Pearls Summary

1. Never stop basal insulin completely in Type 1 diabetes - even small amounts prevent DKA
2. Think "140-180" - safe perioperative glucose targets for most patients
3. Stop SGLT-2 inhibitors 3+ days before surgery - euglycemic DKA is dangerous and difficult to diagnose
4. Test for cardiac autonomic neuropathy - simple bedside tests identify high-risk patients
5. Use the 80-50-50 rule - smooth transition from IV to subcutaneous insulin
6. HbA1c >8% increases risk but rarely justifies delaying necessary surgery
7. Overlap insulin strategies - when transitioning between regimens, overlap by 2-4 hours
8. Suspect euglycemic DKA - check ketones in sick patients regardless of glucose level

Conclusion

Perioperative management of diabetes requires careful attention to preoperative assessment, thoughtful medication adjustment, appropriate intraoperative monitoring, and vigilant postoperative care. While hyperglycemia increases infection risk and impairs healing, hypoglycemia poses immediate danger. Evidence supports moderate glycemic targets (140-180 mg/dL) for most surgical patients, with individualization based on patient factors and surgical risk. Multidisciplinary collaboration between surgeons, anesthesiologists, and endocrinologists optimizes outcomes for this high-risk population.

References

1. American Diabetes Association. Standards of Medical Care in Diabetes—2023. Diabetes Care. 2023;46(Suppl 1):S1-S291.

2. NICE-SUGAR Study Investigators. Intensive versus conventional glucose control in critically ill patients. N Engl J Med. 2009;360(13):1283-1297.

3. Duggan EW, Carlson K, Umpierrez GE. Perioperative hyperglycemia management: an update. Anesthesiology. 2017;126(3):547-560.

4. Dhatariya K, Levy N, Kilvert A, et al. NHS Diabetes guideline for the perioperative management of the adult patient with diabetes. Diabet Med. 2012;29(4):420-433.

5. Umpierrez GE, Smiley D, Jacobs S, et al. Randomized study of basal-bolus insulin therapy in the inpatient management of patients with type 2 diabetes undergoing general surgery. Diabetes Care. 2011;34(2):256-261.

6. Kwon S, Thompson R, Dellinger P, et al. Importance of perioperative glycemic control in general surgery: a report from the Surgical Care and Outcomes Assessment Program. Ann Surg. 2013;257(1):8-14.

7. Ljungqvist O, Scott M, Fearon KC. Enhanced Recovery After Surgery: A Review. JAMA Surg. 2017;152(3):292-298.

8. Hulkower RD, Pollack RM, Zonszein J. Understanding hypoglycemia in hospitalized patients. Diabetes Manag. 2014;4(2):165-176.

---

Word Count: Approximately 2,000 words

Disclosure: The author declares no conflicts of interest.