Does the risk of diabetic ketoacidosis outweigh the benefit of proceeding with cataract surgery in a patient taking SGLT2 (Sodium-Glucose Linked Transporter 2) inhibitors, such as canagliflozin (canagliflozin), given that cataract surgery is considered a low-stress procedure?

Management of SGLT2 Inhibitors for Cataract Surgery

For patients taking SGLT2 inhibitors, the risk of euglycemic diabetic ketoacidosis outweighs the benefit of proceeding with cataract surgery without proper medication management, even though cataract surgery is considered a low-stress procedure. 1

Preoperative Management of SGLT2 Inhibitors

• SGLT2 inhibitors should be omitted the day before and the day of cataract surgery 1, 2
• This provides at least a 48-hour gap before a morning procedure and a 36-hour gap for evening doses
• For maximum safety, consider discontinuing 3-4 days before surgery as recommended by some guidelines 1, 2

Rationale for Discontinuation

1. Risk of Euglycemic Diabetic Ketoacidosis (euDKA):

   • SGLT2 inhibitors increase the risk of perioperative DKA, particularly euglycemic DKA 2
   • This risk exists on a continuum rather than having a defined threshold 1
   • Even with "low-stress" procedures like cataract surgery, the risk remains significant

2. Evidence of Risk:

   • Research shows a strong association between decreased hold time and postoperative anion gap acidosis 3
   • Cases of euDKA have been reported even when patients withheld SGLT2 inhibitors for >72 hours 1
   • The American Society of Anesthesiologists recommends postponing cataract surgery if a patient has not held their SGLT2 inhibitor as recommended 2

Risk Mitigation Strategies

• Ensure proper hydration and minimize fasting time 1, 2
• Consider glucose-containing IV fluids to mitigate ketone generation during unavoidable prolonged fasting 1
• Monitor for signs of euDKA (nausea, vomiting, tachypnea, anion gap metabolic acidosis) even with normal glucose levels 4, 5
• Be aware that euDKA can present with glucose levels <14 mmol/L (250 mg/dL), making diagnosis challenging 4, 6

Postoperative Management

• Restart SGLT2 inhibitors only when:
  • Patient is eating and drinking normally (usually 24-48 hours after surgery) 1, 2
  • Capillary ketones are <0.6 mmol/L 1
  • No signs of metabolic derangement are present 2

Special Considerations

• For patients with heart failure on SGLT2 inhibitors:

  • Balance the risk of ketoacidosis against the risk of worsening heart failure from medication cessation 1
  • More careful monitoring may be warranted if the decision is made to continue the medication

• For emergency cataract surgery:

  • Recent research suggests that emergency surgery with SGLT2 inhibitor use may not significantly increase DKA risk compared to non-users 7
  • However, established guidelines still recommend withholding when possible 1, 2

Common Pitfalls to Avoid

• Relying solely on glucose levels to rule out DKA, as euglycemic DKA can occur with normal glucose 2, 6
• Failing to recognize that surgical stress, even from "low-stress" procedures, can contribute to ketosis 5
• Underestimating the persistence of SGLT2 inhibitor effects beyond their half-lives 5

While cataract surgery is considered low-stress, the risk of euglycemic DKA from SGLT2 inhibitors requires appropriate medication management. Following established guidelines for discontinuation and monitoring provides the best balance of safety while allowing necessary surgical care.