Hypoglycaemia is a condition, in which blood sugar level falls below 70mg%. When blood sugar levels fall, there is an increase in counter-regulatory hormone levels to maintain the optimum blood glucose levels. In diabetics, hypoglycaemia is very common among the
•Patients with infections,
•Patients with impaired kidney function,
•Patients on insulin therapy,
•After alcohol abuse (or) vigorous exercise
•Diabetics who fast for religious reasons or those with continuous vomiting are prone to hypoglycaemia.
1) It is more common in insulin-dependent diabetes than maturity onset diabetes (type II diabetes). Hypoglycaemia is more common and pronounced if one aims for intense blood sugar control. Hypoglycaemia can result in ECG changes with or without any symptom (silent ischemia). It also can trigger angina, heart attacks, acute heart failure and/or cardiac rhythm disturbances. Some of the recent studies have shown that hypoglycaemic episodes increase cardiovascular events and mortality. Studies have also shown that adverse cardiovascular events are three times more common among those with intense glucose control compared with optimal control. Swings in blood sugar levels are equally hazardous.
Symptoms of hypoglycaemia
With the onset of hypoglycaemia, heart rate and systolic blood pressure increase with vigorous heart pumping activity owing to adrenaline release. This may result in such symptoms as sweating, palpitations, giddiness, restlessness and confusion. Some patients may experience intense hunger and lack of concentration. Rarely can hypoglycaemia be silent without any symptoms.
2) The exact incidence of hypoglycaemia is not known because these episodes may be mild, moderate or severe. Mild symptoms may even be undetected. Mild hypoglycaemic events are more common but less reported. Patients, who experience frequent hypoglycaemic episodes, may take corrective steps with the onset of premonitory symptoms. Dead in the bed syndrome due to nocturnal hypoglycaemia resulting in cardiac rhythm disturbances has been thought to be due to extreme hypoglycaemia, and fortunately this is very rare.
The challenge of physicians is to adjust blood glucose levels to near normal range and reduce complications of diabetes, while at the same time minimise or prevent hypoglycaemic events. One must particularly be more cautious in diabetics with underlying heart disease. Blood HbA1c level is a biochemical parameter to assess long-term glucose control. Hypoglycaemic episodes are more common if HbA1c level is < 7%. “Lower the better is no longer the rule.”
(Dr. I. Sathyamurthy is an interventional cardiologist and director of the Department of Cardiology, Apollo Hospitals, Chennai. He is the recipient of the Padma Shri Award for 2000 and the Dr. B.C. Roy National Award for 2001).