The document discusses anaesthetic considerations for patients with diabetes mellitus. It notes that the preanesthesia evaluation should include assessing the patient's type of diabetes, level of blood glucose control, and medication regimen. It also discusses implications for different types of diabetes, implications of regional anesthesia, diabetic complications like nephropathy and implications for airway management. The document provides guidance on adjustments to insulin regimens prior to surgery depending on the patient's usual insulin doses and risk of hypoglycemia.

1. Anaesthetic considerations
in diabetes mellitus
Dr. Hassam Zulfiqar
PGT Anaesthesia, HFH

2. PREANESTHESIA EVALUATION
● The preanesthesia evaluation of diabetic patient should include assessment of patient's
type of diabetes (ie, type 1 or type 2), the baseline level of blood glucose control,
and the patient's medication regimen.
● Basic laboratory investigation should include a baseline electrocardiogram (ECG),
assessment of renal function (serum creatinine), glycated hemoglobin (A1C) if not
measured in previous four to six weeks, and fasting blood glucose
● Diabetes is a risk factor for macrovascular disease (ie, coronary heart disease [CHD],
cerebrovascular disease [CVD], and peripheral vascular disease) and microvascular
disease (ie, retinopathy, nephropathy, neuropathy), all of which may have implications
for perioperative care.

3. DIABETES HISTORY
● Type 1 versus type 2 diabetes — The type of diabetes should be determined, since
patients with type 1 diabetes are at much higher risk of diabetic ketoacidosis and must
receive basal insulin at all times. Patients with type 2 diabetes are susceptible to
developing hyperosmolar hyperglycemic state (also known as nonketotic
hyperosmolar state) that may lead to severe volume depletion and neurologic
complications, and they may develop ketoacidosis in the setting of extreme stress.

4. ● Level of blood glucose control — The level of blood glucose control should be
assessed preoperatively, including average and range of blood glucose levels, glycated
hemoglobin (A1C) levels, and the frequency of patient monitoring
● Different societal guidelines recommend various A1C thresholds for delaying elective
surgery. The American Diabetes Association does not make specific recommendations
for this scenario, whereas the Australian Diabetes Association guidelines recommend
delaying surgery for A1C ≥9 percent, and the Association of Anaesthetists of Great
Britain and Ireland recommends delay of elective surgery for a preoperative A1C
≥8.5 percent. The Joint British Societies guidelines recommend referral to a specialist
for evaluation if preoperative A1C is ≥8.5 percent, but state that the decision to delay
surgery must be individualized.

5. ● Medication regimen — Assessment of the patient's medication regimen is part of every
preanesthesia evaluation. For diabetic patients, insulin type, dose and timing, and oral
diabetes medications must be determined to allow for appropriate preoperative management
● SGLT2 inhibitors (eg, empagliflozin, dapagliflozin, canagliflozin) should be stopped
three to four days before surgery (ADA 2021). These agents increase the risk of
urinary tract infections and hypovolemia. There have also been reports of acute kidney
injury and euglycemic diabetic ketoacidosis in patients with type 2 diabetes taking
SGLT2 inhibitors

6. ● Other oral agents or GLP-1 receptor agonists – Oral hypoglycemic and/or noninsulin
injectable drugs (GLP-1 agonists e.g exenatide) should be withheld starting on the
morning of scheduled surgery for the reasons stated below:
❖ Metformin is contraindicated in conditions that increase the risk of renal hypoperfusion,
lactate accumulation, and tissue hypoxia.
❖ Sulfonylureas and meglitinides can cause hypoglycemia.
❖ Thiazolidinediones may worsen fluid retention and peripheral edema and could
precipitate congestive heart failure.
❖ Dipeptidyl peptidase 4 (DPP-4) inhibitors and GLP-1 receptor agonists could alter
gastrointestinal motility and worsen the postoperative state. Since DPP-4 inhibitors are
generally considered not to increase the risk of hypoglycemia, some experts continue
DPP-4 inhibitors on the day of surgery (AAGBI 2019)

8. ● Diabetic patients should be scheduled as the first patient of the day, or as early as
possible to minimize disruption of normal insulin dosing schedules.

10. Why should insulin be continued when the patient is fasted?
● Patients with type 1 diabetes and some insulin-treated patients with type 2 diabetes
are insulin deficient. They are at much higher risk of diabetic ketoacidosis and must
have basal insulin supplied at all times.
● Basal insulin dosing generally accounts for approximately one-half of an individual's
total daily insulin dose. It is necessary to prevent ketoacidosis and limit protein loss
during reduced caloric intake and perioperative stress. Therefore, basal insulin must be
given to insulin-deficient patients even in the absence of oral intake

12. ● Patients who are on home insulin therapy should reduce the dose of long-acting basal
insulin (glargine, detemir) by 20-25% the evening before surgery.
● If they routinely take basal insulin only in the morning, then the reduced dose should
instead be administered on the morning of surgery.
● Patients who are on twice daily glargine or detemir should reduce the dose by 20 to
25% in the evening prior to as well as the morning of surgery.
● However, in patients who take high doses of basal insulin (>60% of total daily insulin)
or total daily insulin dose is greater than 80 units or are at high risk of hypoglycemia
(elderly, renal or hepatic insufficiency, prior hypoglycemic episodes); basal insulin
dose should be reduced by 50 to 75% to minimize hypoglycemia risk

13. ● Patients who are on premixed insulin (NPH/Regular 70/30, aspart protamine/aspart
75/25, etc.), should preferably receive long-acting insulin the evening prior instead of
their premixed formulation.
● However, this may not be feasible in a lot of these patients. In such scenarios, the
premixed insulin is reduced by 50% on the morning of surgery, followed by the
initiation of dextrose-containing intravenous solutions.
● Alternatively, these patients can be asked to skip the morning dose and arrive early to
the preoperative area where they can receive a long-acting formulation.

14. Other Anaesthetic Considerations
● The choice of anesthetic technique (general anesthesia, regional anesthesia, or monitored
anesthesia care) should be based on the surgical procedure, patient factors, and patient and
provider preferences. Neuraxial anesthesia/analgesia may reduce postoperative insulin
resistance and hyperglycemia by reducing the stress response to surgery.
● Diabetic patients are at increased risk of atherosclerosis due to the frequent presence of
risk factors other than diabetes itself (ie, hypertension, hyperlipidemia, obesity, and
uncontrolled hyperglycemia)
● Diabetes or insulin dependence is a risk factor in a number of the commonly used tools for
assessment of cardiac risk prior to noncardiac surgery (eg, the Revised Cardiac Risk
Index [RCRI], the Vascular Study Group of New England [VSGNE] risk index, the American
College of Surgeons National Surgical Quality Improvement Program [NSQIP] calculator)

15. Implications for Regional Anesthesia
.
● Increased nerve stimulation threshold – Ultrasound guidance is preferred for most peripheral
nerve blocks, rather than nerve stimulator guidance, and this may be particularly important for
patients with diabetic neuropathy. The nerve electrical stimulation threshold is markedly increased in
patients with diabetic neuropathy, and varies widely. Thus the safe stimulation threshold for
stimulator guided peripheral nerve block may be unpredictable in patients with neuropathy, and the
risk for nerve injury may be increased
● Increased sensitivity to local anesthetics – Sensitivity of nerves to LA may be increased in
patients with diabetes. Thus diabetic patients may be at increased risk of nerve damage with
regional anesthesia, and duration of peripheral nerve block may be prolonged
● Epidural abscess occurs more commonly in patients with diabetes than in nondiabetic
patients

16. Diabetic Autonomic Neuropathy
● Cardiovascular autonomic neuropathy (CAN) is associated with resting tachycardia, exercise
intolerance, orthostatic hypotension, supine hypertension, syncope, intraoperative cardiovascular
instability, silent myocardial infarction and ischemia, and increased mortality.
● DAN of the GI tract can result in gastroesophageal reflux disease (GERD) and/or delayed gastric
emptying, either of which can increase the risk of aspiration during induction of anesthesia.
● During preanesthesia evaluation all patients should be questioned about symptoms of GERD and
delayed gastric emptying, including heart burn, regurgitation, early satiety, bloating, nausea,
vomiting, or abdominal pain. Patient with such symptoms may require longer fasting duration
preoperatively, and many clinicians utilize rapid sequence induction and intubation (RSII) to
minimize the risk of aspiration.
● Patients who have constipation as a result of DAN of the GI tract may benefit from multimodal
postoperative analgesia that minimizes the use of opioids.

17. Airway Considerations
● Patients with diabetes-associated musculoskeletal abnormalities may be at increased risk of
difficulty with airway management
● Postulated mechanisms for difficult laryngoscopy include diabetes-related cervical spine,
atlanto-occipital joint, or temporomandibular joint disease. Limited range of motion of the
head and neck can result from the syndrome of limited joint mobility (previously known as
cheiroarthropathy), which most commonly affects the joints of the hands but can affect the
axial spine as well. Limited joint mobility can occur in patients with either type 1 or type 2
diabetes
● One test of limited joint mobility is a positive "prayer sign," which refers to the inability to
completely flatten the hands together as in prayer. In some studies, a palm print test has
been used as a more objective measure of limited joint mobility

19. Diabetic nephropathy and retinopathy
● Diabetic nephropathy occurs in both type 1 and type 2 diabetes, and routine screening for patients
with known diabetes includes annual testing for urinary albumin excretion.
● For patients with diabetic nephropathy, we apply general principles for avoidance of perioperative
kidney injury, including maintenance of renal perfusion and avoidance of nephrotoxins.
● Renal dysfunction (independent of diabetes) is one of the risk factors in the commonly used
preoperative cardiac risk assessment tools (ie, RCRI, VSGNE, NSQIP calculator).
● Nonsteroidal antiinflammatory drugs (NSAIDs), which are often administered as part of
multimodal postoperative analgesia, should be used cautiously or avoided in patients with diabetic
nephropathy
● In patients with known Diabetic Retinopathy who undergo surgery associated with an increased
risk of postoperative visual loss (eg, prone spinal fusion, bilateral head and neck procedures,
prolonged procedures in the head down position), it is important to document preoperative
visual acuity and visual fields.

20. MCQ
A 55-year old female, with a past medical history of type 2 diabetes mellitus, hypertension, and
dyslipidemia. Her medications include subcutaneous insulin glargine 20 units in the morning,
subcutaneous insulin lispro 6 units three times a day with meals, and oral atorvastatin 40 mg at
bedtime. She visits pre-operative clinic for evaluation before elective hysterectomy scheduled next
week. She denies episodes of hypoglycemia. Her hemoglobin A1c is 6.8%. What changes in her
insulin regimen should be recommended prior to the surgery?
1.No change in the insulin regimen
2.Hold insulin lispro and take 16 units of insulin glargine on the day of surgery
3.Hold insulin lispro and take 16 units of insulin glargine on the day of surgery and the day prior
4.Hold insulin glargine and take 4 units of insulin lispro three times a day on the day of surgery

21. ANSWER: 2 Hold insulin lispro and take 16 units of insulin glargine on the day of surgery
● In the case discussed above, the patients total daily dose of insulin is 38 units, approximately 50% of which
she takes as long-acting basal insulin and the remaining as rapid-acting nutritional insulin with meals. She
denies any episodes of hypoglycemia and her hemoglobin A1C reflects optimal glycemic control. The best
recommendation for the patient is to hold nutritional insulin and reduce basal insulin by 20-25%
(approximately 16 units) on the day of surgery.
● In this case, it is unnecessary to reduce long-acting insulin the day before surgery as she routinely takes
her basal insulin in the morning and will not be in fasting state. This can predispose her to unwanted
hyperglycemia.
● Holding basal insulin and continuation of nutritional insulin while in a fasting state can predispose her to
fluctuating episodes of hypoglycemia and hyperglycemia.

22. THANK YOU