Diabetes and surgical interventions

1. preoperative

For minor to moderate surgery, diabetes type 2 patients who are on oral antidiabetics should receive either an insulin perfusor or a long-acting insulin such as NPH- insulin (Karges 2014) s. c. (25-50% reduction) plus a short-acting insulin such as regular ins ulin (Wooliscroft 2013). (Kasper 2015)

Before major surgery, it is often advisable to admit diabetics as inpatients for metabolic control and preoperative diagnostics 2 - 3 days beforehand, if possible (Mehnert 2003).

Waldhäusl (2013) recommends extending the preoperative fasting period because of the gastroparesis with delayed gastric emptying demonstrated in diabetics, otherwise there is a risk of aspiration. Gallwitz (2019), on the other hand, points out that the period of food abstinence should be kept as short as possible to avoid glucose fluctuations. Moreover, food abstinence > 12 h worsens peripheral insulin action.

• Metformin should be discontinued as early as 48 h before surgery, otherwise there is a risk of lactic acidosis (Waldhäusl 2013). For major surgery, the patient should be started on insulin preoperatively (Herold 2020).
• Sulfonylureas have a long half-life of up to 72 h and should also be paused because of the potential risk of hypoglycemia (Gallwitz 2019).
• DPP- 4- inhibitors can continue to be administered-with the exception of existing pancreatitis (Gallwitz 2019).
• SGLT- 2- inhibitors have an antihyperglycemic effect but have no hypoglycemic risk oftheir own, but significantly increase the rate of genital infections. They should not be used in patients exposed to prolonged fasting periods, receiving loop diuretics, or with volume deficiency (Gallwitz 2019).
• GLP- 1 receptor antagonists have no intrinsic hypoglycemic risk. Treatment can be continued, except in cases of pancreatitis (Gallwitz 2019).

If diabetes has been poorly controlled for years, echocardiography should be performed preoperatively to rule out cardiomyopathy (Gallwitz 2019).

Preoperative minimum requirements are:

• current blood glucose < 200 mg / dl
• no hypoglycemia
• stable circulation
• Isohydria
• water and electrolyte balance balanced (Herold 2020)
• HbA1c not > 9 % (64 - 75 mmol / mol) (Gallwitz 2019).

The HbA1c value also allows conclusions to be drawn about the immune status: the higher the HbA1c value, the more immunocompetent cells such as leukocytes, macrophages are glycated and therefore unable to function (Zander 2019).

• Determination of triglycerides

These give an indication of endogenous and exogenous insulin action: the higher the level, the greater the insulin resistance(Zander 2019).

• Creatinine
• glomerular filtration rate (GFR).

Due to any renal damage present, there are consequences peri- and postoperatively for volume control and with regard to avoiding potentially kidney-damaging drugs such as NSAIDs.

• Electrolytes (especially because of possible hypokalemia and hyponatremia) (Zander 2019).

Anesthesia

In long-term diabetics, stiffening of the joints, a so-called "stiff joint syndrome," may lead to difficulty in reclining the head during intubation. Therefore, intubation is usually more difficult in diabetics than in non-diabetics. An indication of this is the so-called prayer sign, in which the patient is asked to bring the folded hands completely together in front of the chest (Zander 2019). Anesthesia leads to an anti-insulin stress response with increase in cortisol secretion and increase in sympathetic activity.

Fewer adverse effects are found with epidural or spinal anesthesia, which should be preferred when possible. Contraindication to regional anesthesia is severe autonomic neuropathy (Waldhäusl 2013).

With local anesthesia, patients with prolonged diabetes mellitus usually require fewer anesthetics than healthy individuals, but the duration of action is often prolonged (Zander 2019).

Patients with preexisting autonomic neuropathy should not be anesthetized with nitrous oxide because it has a potentially negative effect on the nervous system (Zander 2019).

Surgery should be scheduled as

• scheduled early in the day (Herold 2020) to keep the fasting period as short as possible (Zander 2019) and
• at the beginning of the week, in order to be able to optimize the staff-intensive postoperative care (Mehnert 2003).

2. perioperative

Autonomic neuropathy is present in approximately 20%-40% of diabetic patients. This can cause cardiovascular problems during positioning due to reduced perfusion of the higher body regions.

Likewise, a pre-existing diabetic polyneuropathy can lead to a pressure load on the tissue more quickly than in healthy persons if the patient is positioned unchanged on the operating table for a longer period of time, thus triggering focal ischemia (Zander 2019).

The greatest perioperative risk for the patient is ketoacidosis and severe hypoglycemia (Müller 2021).

Perioperatively, the patient should receive separate infusions according to the GIK- regimen (glucose, insulin, potassium regimen [Mehnert 2003]) of:

• Glucose 5% (140 - 180 mg / dl or 7.8 - 10 mmol / l[Gallwitz 2019]).
• electrolytes (100 - 200 ml / h)
• Insulin

The basic rule here is:

• 1 IU of normal insulin lowers blood glucose by 0.5 to a maximum of 2.0 mmol / l (depending, for example, on the existing stress metabolism and the type of diabetes [Müller 2021]).
• Normal insulin via perfusor at blood glucose levels between 120 - 180 mg / dl:
  • With a daily requirement of < 40 I. E. administration of 1.0 I. E. / h
  • at a daily requirement of 40 - 80 I. E. Administration of 1.5 I. E. / h
  • at a daily requirement of > 80 I. E. Administration of 2.0 I. E. / h
  • as soon as the blood glucose rises > 200 mg / dl, the administration of an additional 0.5 I. E. normal insulin is required
  • at BG values of < 120 mg / dl, 0.5 I. E. normal insulin less should be given
  • at BG- values of ≤ 100 mg / dl, the insulin supply should be reduced or stopped and the glucose supply increased. Blood glucose should then be measured every 15-30 min (Herold 2020).

During surgery, the target blood glucose should be between 7.8 - 10.0 mmol / l = 144 - 180 mmol / l (Müller 2021).

• Check blood glucose hourly (Herold 2020).

Since insulin and glucose increase the potassium efflux into the cell, there is a particular risk of hypokalemia. When infusing with insulin and glucose, the potassium requirement is approximately 1 - 4 mmol / h, this should be controlled accordingly with reference to the serum potassium level (Waldhäusl 2013).

• Check serum potassium every 4 h (Herold 2020).
• To avoid p. o. PONV (postoperative nausea and vomiting), administration of 4 mg dexamethasone is recommended (Zander 2019)

Perioperative complications may occur due to diabetes-related sequelae such as:

• microvascular:
  • Retinopathy
  • renal insufficiency
• macrovascular:
  • peripheral AVK
  • Carotid stenosis
  • CHD
• neuropathic:
  • autonomic neuropathy
  • polyneuropathy (Zander 2019)

Perioperative mortality is increased in diabetics especially due to vascular complications.

3. postoperative

Indication for intensive medical monitoring should be generous in diabetics (Waldhäusl 2013).

• Urine acetone / ABG control

In the monitoring ward, urine acetone or a ABG should be checked several times a day in type 1 diabetes and pancreopriven patients because of the risk of ketoacidosis (Zander 2019).

The 3 most common postoperative complications are:

• Infections
• Myocardial infarction (often manifested in diabetics only by shortness of breath [Zander 2019]).
• Renal complications (especially in diabetics with autonomic neuropathy or intraoperative hemodynamic problems [Waldhäusl 2013]).
• Blood glucose:

Blood glucose concentration should be monitored p.o. every 4 h (Waldhäusl 2013). In hypoglycemia, 1 BE increases blood glucose by 50 mg / dl (Zander 2019) and in hyperglycemia, 1 IU of normal insulin lowers blood glucose by 0.5 to a maximum of 2.0 mmol / l (depending, for example, on the existing stress metabolism and the type of diabetes (Müller 2021).

• Fluid requirements:

The fluid requirement is high and is 2 - 3 l / d (Waldhäusl 2013). To avoid edema, especially cerebral edema, electrolyte shifts, etc., fluid administration should be slow (Zander 2019).

• Oral antidiabetics:

The patient can be switched back to oral antidiabetics with regular food intake p. o. (Müller 2021), which is usually the case 1 - 2 days after surgery (Herold 2020).

For metformin, the manufacturer recommends a minimum 48-hour break postoperatively (Zander 2019).

• Postoperative insulin resistance:

This depends on the size of the surgery (Herold 2020).

• Close blood glucose monitoring required (Herold 2020).
• Lactic acidosis:

Lactic acidosis, a life-threatening complication that occurs very rarely (2 - 5 cases per 100,000 years of use), can be triggered by administration of biguanides such as metformin or Glucophage ret. The risk is particularly present in patients with renal insufficiency. The typical symptoms are:

• Hyperglycemia (500 - 1,000 mg %)
• plus metabolic acidosis with anion gap
• plus ketonemia
• Kussmaul breathing (if the patient breathes spontaneously).

Treatment consists of immediate slow delivery of insulin via syringe pump. The high bolus doses used in the past now appear to be no longer useful (Zander 2019).

• Pain management:

It is imperative to provide adequate pain management, as pain is a stressful state for the body. Potentially kidney-damaging drugs such as NSAIDs should be avoided in diabetic patients (Zander 2019).

Hypoglycemia:

Certain surgeries pose a risk of hypoglycemia postoperatively due to decreased insulin requirements p.o.. These include:

• Amputation of a limb in the presence of gangrene and / or severe infection.
• Drainage of an abscess or phlegmon.
• Extirpation of an infected organ such as the gallbladder
• Sectio
• Pheochromocytoma - surgery
• Hypophysectomy
• Adrenalectomy (Herold 2020).

In the postoperative phase, wound healing disorders occur more frequently in diabetics, and resistance to infection is also reduced (Waldhäusl 2013).

Metabolic derailments can also occur during surgery. Patients with autonomic neuropathy are usually particularly affected (Waldhäusl 2013).

In every patient there is a so-called post-aggression syndrome - independent of diabetes - a metabolic disorder with an

• Increase of the insulin level
• Increase in anti-insulin factors such as:
  • Glucagon
  • Catecholamines
  • Corticosteroids

The expression of postaggression syndrome depends, among other things, on the extent of the surgical trauma (Zander 2019).

Metabolically healthy individuals can compensate for these hormonal-metabolic changes, but this is not the case in diabetics. The latter reacts to the post-aggression syndrome with:

• Hyperglycemia
• Ketoacidosis
• Ketonemia
• lactic acidosis
• increased tendency to thrombosis (due to activated hemostasis)
• disturbed micro- and macrocirculation with consecutive deficiency of tissue supply and subsequent wound healing disorders (Mehnert 2003)

Emergency surgery

Emergency required surgery accounts for <5% in diabetic patients.

Of particular importance here are monitoring of cardiac and renal functional parameters and checking metabolic status. Insulin should always be delivered via a perfusor as described above. It should be noted that high glucose intake without simultaneous insulin administration and loop diuretics favors the development of hyperosmolar non-ketotic coma (Waldhäusl 2013).

In 1959, according to Joslin et al, every 2nd diabetic patient needed to see a surgeon at least once in their lifetime and according to Briem (1969), every 7th surgical patient was diabetic (Beckmann 2013).

Overall, diabetics require surgical interventions more frequently than metabolically healthy individuals. For example, bypass surgery was required in 11.3% of diabetics and 4.3% of the general population (Waldhäusl 2013).

A surgical procedure creates stress in the body, which manifests itself as the induction of a catabolic metabolic state. It leads to an:

• Increase in gluconeogenesis (mainly from lactate)
• Increase in lipolysis
• Increase in proteolysis
• inhibition of peripheral glucose oxidation

The resulting insulin resistance cannot be regulated by endogenous insulin secretion, as is the case in healthy individuals, and there is a risk of ketoacidosis even with moderate hyperglycaemia of < 300 mg/dl.

A further problem is the disturbed regulation of macro- and microcirculation in diabetics, which leads to a nutritional deficiency in the tissue in the event of blood loss or a drop in blood pressure. This leads to hyperlactatemia and even lactic acidosis, which also explains the wound healing disorders and the deterioration of kidney function.

Thirdly, the activation of haemostasis plays a role. In diabetics, this is already activated even in the absence of stress and increases even more during surgical interventions. This increases the postoperative risk of thrombosis and worsens the microcirculation.

(Waldhäusl 2013)

According to Constam, surgical mortality in diabetics ranged from 18% - 46% in 1942 and was reduced to 1.4% - 3.7% in 1971 due to the insulin era and improved anesthesia and surgical procedures (Beckmann 2013).

Nowadays, the surgical risk is still increased in diabetics, especially because of cardiovascular risk factors with macro- and microangiopathy (Waldhäusl 2013).

The length of stay in diabetics is almost always prolonged, and the mortality risk compared to metabolically healthy patients can be increased by up to 50%, depending on the metabolic situation (Gallwitz 2019). On the other hand, many clinical observations show that the risk of surgery - even in major procedures such as open heart surgery - does not have to be generally increased (Mehnert 2003).

In surgical intensive care patients, mortality can be reduced by up to 30 % when blood glucose is normalized with insulin; in the case of septic complications, mortality can even be reduced by up to 50 % (Herold 2020).

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