Diabetes and Anesthesia: What Are the Risks?
Diabetes affects over 25 million Americans and the number is expected to grow.
Diabetes is a disorder of internal blood sugar management and either a deficiency of, or resistance to, the hormone insulin. But diabetes is really a systemic disease with implications for abnormalities in almost every body system. Because of this, diabetic patients may have extra risk when undergoing surgery and anesthesia.
Type I Diabetes
This type used to be called "juvenile diabetes" or "insulin-dependent diabetes". These terms aren't used as much anymore since it's known that type I diabetes can occur at any age. Also, type II diabetics may also use insulin, so that phrase is a bit misleading, as well.
In any case, type I diabetes is diagnosed when the body does not produce enough insulin to help manage the body's blood sugar. This lack of production occurs because the cells in the pancreas that make insulin are destroyed by the body's own immune system.
Type II Diabetes
An overwhelming majority (about 95 percent) of diabetes in this country is type II diabetes.Type II diabetes is associated with poor diet, obesity, and inactivity. It results from the body's inability to produce enough insulin OR the body's resistance to the effects of insulin. So, insulin may be made, but the body doesn't react normally to it, leading to abnormalities with blood sugar and complications from it.
This is the type that has traditionally been called "adult onset" or "non-insulin dependent" diabetes. These terms also are becoming misnomers since more children are being diagnosed with type II diabetes as the percentage of overweight children climbs. Also, some of these patients don't achieve good control with diet or oral medications and end up using insulin for blood sugar management.
For Diabetes Patients
Risks: Airway and Lungs
Airway: The airway is the passageway for oxygen. For anesthesiologists, it refers to the passageway into which a breathing tube must be placed. Because of the affects of high blood sugar on joints, "stiff joint syndrome" may be present. This can make the jaw and neck stiff, making it more difficult to place the breathing tube.
Aspiration Risk: Aspiration occurs when contents of the stomach (food or acid) is pushed upward into the esophagus (food tube), into the throat and can then enter the windpipe and lungs. Diabetics have a slowed stomach-emptying process, called "gastroparesis". This increases the risk that food or acid may be regurgitated and aspirated into the lungs which can lead lung damage or a dangerous pneumonia.
Lung Function: Type I diabetics with long-term poor glucose control have reduced lung function and may be more susceptible to complications such as pneumonia. Obesity in many type II diabetics can also potentially predispose to lung and oxygen issues after surgery. Studies have also found a higher incidence of respiratory arrest in diabetics in the postoperative period.
Higher Rates of Heart Disease
Diabetics have an accelerated and increased rate of heart disease, such as hardening of the arteries. In fact, diabetes increases the risk of heart disease four- to five-fold. In addition, diabetic patients don't always have obvious symptoms (less incidence of chest pain, for example) when heart disease is present.
This increases the risk of having intra- and post-op cardiac complications. Heart attacks, cardiac ischemia, arrhythmias, and cardiac arrest risk are all increased. The anesthesiologist will be monitoring the EKG and vital signs carefully to minimize this risk.
The Diabetic Kidney
Nephropathy--kidney disease--is more likely to be present in diabetic patients. This is due to the excessive glucose to which the kidney are exposed in diabetics.
Kidney disease changes the metabolism and excretion of some anesthetic drugs, leading to unpredictable responses to some medications, and the potential for dangerous build-up of others.
The kidneys are also responsible for helping to balance the important electrolytes in the body such as sodium, potassium and calcium. Abnormal clearance or altered balance of these substances can lead to dangerous consequences such as lethal heart arrhythmias.
Nerve Problems: Because nerve dysfunction is so common, injuries related to positioning on the operating table may be more likely in diabetic patients. Diabetics are prone to ulceration and infections, especially of the feet and toes, in areas that are numb due to nerve dysfunction. These areas must be carefully padded and protected while a diabetic patient is unconscious under anesthesia.
Autonomic Neuropathy: Also, the autonomic nervous system is affected. This means that changes in heart rate, rhythm and blood pressure may be more dramatic and harder to treat. Again, anesthesiologists are aware of these issues and prepared to deal with them.
Hypoglycemia and Hyperglycemia
Problems can develop with blood sugar that is either too high or too low, as well. The stress response to surgery increases blood sugar levels. Treatment of high blood sugar can inadvertently cause dangerously low blood sugar. Some patients have levels that are difficult to manage and can present quite a challenge, both intraoperatively and postoperatively in trying to achieve good control of blood sugar.
Dangers of High Blood Sugar
Type I diabetics are at risk for diabetic ketoacidosis when blood sugar surges to very high levels. DKA as it is known, results from the effects of abnormal metabolism of excess blood sugar. In the absence of insulin in type I diabetes, sugar cannot be burned as fuel for the body. Instead, fats are broken down excessively and ketones build up as a by-product of this metabolism. Ketones are poisonous when they accumulate in the blood. Acidosis, a lowered blood pH (high acid level), causes dangerous changes throughout the body. The dangers include kidney failure, brain swelling, electrolyte problems and cardiac arrest.
In type II diabetics, a condition called HHNS for "hyperosmolar hyperglycemic nonketotic syndrome". Very high blood sugar levels cause increased fluid loss through the kidneys. Severe dehydration and dangerously low potassium levels are among the dangers of this condition. It is "non-ketotic" because ketones aren't usually produced since some insulin is present, preventing their formation.
Dangers of Low Blood Sugar
Low blood sugar, called hypoglycemia, creates difficulty concentrating and other changes in mentation or level of consciousness. This can be confused in the postoperative period with other problems like overdose of medication or stroke, leading to unnecessary testing and therapies. Low blood sugar also causes adrenaline to be released which can lead to rapid or irregular heartbeat. Other cardiac and nervous system problems may also occur.