Nocturnal convulsions and insulin-induced hypoglycaemia in diabetic patients

Nocturnal hypoglycemia in type 1 and type 2 diabetes: an update on prevalence, prevention, pathophysiology and patient awareness

INTRODUCTION

Despite considerable progress in diabetes treatment, prevalence of nocturnal hypoglycemia in type 1 diabetes mellitus (T1DM) and advanced insulin treated type 2 diabetes mellitus (T2DM) remains high.

AREAS COVERED

The present manuscript describes the prevalence of night-time hypoglycemia as reported in observational and randomized controlled trials. Factors that affect the risk of hypoglycemia are highlighted. The authors also describe impaired awareness of hypoglycemia and available preventive methods.

EXPERT OPINION

Prevention of nocturnal hypoglycemia includes behavioral, dietary and pharmacologic interventions. The most recent development with the lowest rate of hypoglycemia is sensor-augmented pumps with predictive low glucose suspend technology. These pumps combine continuous subcutaneous insulin infusion with continuous glucose monitoring and use various algorithms to predict and stop hypoglycemia before it develops.

The risks of nocturnal hypoglycaemia in insulin-treated diabetes

Over half of all episodes of severe hypoglycaemia (requiring external help) occur during sleep, but nocturnal hypoglycaemia is often asymptomatic and unrecognised. The precise incidence of nocturnal hypoglycaemia is difficult to determine with no agreed definition, but continuous glucose monitoring has shown that it occurs frequently in people taking insulin. Attenuation of the counter-regulatory responses to hypoglycaemia during sleep may explain why some episodes are undetected and more prolonged, and modifies cardiovascular responses. The morbidity and mortality associated with nocturnal hypoglycaemia is probably much greater than realised, causing seizures, coma and cardiovascular events and affecting quality of life, mood and work performance the following day. It may induce impaired awareness of hypoglycaemia. Cardiac arrhythmias that occur during nocturnal hypoglycaemia include bradycardia and ectopics that may provoke dangerous arrhythmias. Treatment strategies are discussed that may help to minimise the frequency of nocturnal hypoglycaemia.

Pharmacokinetics of phenytoin and its metabolite, 4'-HPPH, after intravenous and oral administration of phenytoin to diabetic rats induced by alloxan or streptozotocin

It has been reported that diabetic patients have an increased risk of developing epileptic convulsions compared with the non-diabetic population, and phenytoin has widely been used for neuralgia in diabetic neuropathy. It has also been reported that in both diabetic rats induced by alloxan (DMIA rats) and by streptozotocin (DMIS rats), the protein expression and mRNA level of 2C11 decreased, but in DMIS rats, the protein expression of CYP2C6 increased. Thus, the pharmacokinetics of phenytoin and 4'-HPPH were investigated after intravenous or oral administration of phenytoin at a dose of 25 mg/kg to DMIA and DMIS rats. After intravenous or oral administration of phenytoin, the AUC (or AUC(0-12 h)) values of both phenytoin and 4'-HPPH were comparable (not significantly different) between each diabetic and the respective control rats. Although the exact reason is not clear, this could have been due to opposite protein expression (and/or mRNA levels) of CYP2C6 and 2C11 in diabetic rats.

Seizures as the only clinical manifestation of reactive hypoglycemia: a case report

A 45-yr old diabetic patient, who had received a diagnosis of grand mal epilepsy, for two episodes of nocturnal tonic-clonic convulsions, underwent continuous glucose monitoring (CGM). During CGM, the patient had an episode of tonic-clonic convulsion, and at the same time a prolonged nocturnal hypoglycemia (<2.2 mmol/l) was observed. CGM revealed that tonic-clonic convulsions, which had been interpreted as a manifestation of epilepsy, were in fact a symptom of severe hypoglycemia. In order to assess the pathogenesis of hypoglycemia, the patient underwent a 75-g oral glucose tolerance test, that was interrupted shortly afterwards for hypoglycemic symptoms (i.e., reactive hypoglycemia). To our knowledge, this is the first case ever reported of reactive hypoglycemia associated with Type 2 diabetes.

Nocturnal hypoglycemia: clinical manifestations and therapeutic strategies toward prevention

OBJECTIVE

To review the features of nocturnal hypoglycemia and various preventive strategies.

METHODS

We discuss the physiologic changes, the potential precipitating factors, the immediate and long-term effects, and the currently available options for treatment of nocturnal hypoglycemia in patients with diabetes.

RESULTS

Nocturnal hypoglycemia is common in patients with type 1 diabetes and is usually asymptomatic. Nocturnal hyperinsulinemia frequently occurs with insulin therapy, and although blood glucose levels are often low during sleep, they are seldom measured routinely. Almost 50% of all episodes of severe hypoglycemia occur at night during sleep. Such episodes can cause convulsions and coma and have been implicated as a precipitating factor in cardiac arrhythmias resulting in sudden death--the "dead-in-bed syndrome." Nocturnal hypoglycemia seems to have no immediate detrimental effect on cognitive function; however, on the following day, mood and well-being may be adversely affected. Recurrent exposure to nocturnal hypoglycemia may impair cognitive function; other substantial long-term morbidity includes the development of acquired hypoglycemia syndromes, such as impaired awareness of hypoglycemia, through the putative effect of unsuspected recurrent episodes of nocturnal hypoglycemia.

CONCLUSION

In efforts to decrease the risk of nocturnal hypoglycemic episodes, various strategies can be used to minimize the nocturnal hyperinsulinemia that is associated with many insulin replacement regimens. Regular blood glucose monitoring (particularly at bedtime), the ingestion of appropriate bedtime snacks, and the utilization of short- and long-acting insulin analogues may all help to prevent or minimize the frequency of nocturnal hypoglycemia.

Incidence and predictive criteria of nocturnal hypoglycemia in young children with insulin-dependent diabetes mellitus

OBJECTIVE

To determine the incidence of significant nocturnal hypoglycemia occurring at home in young children with insulin-dependent diabetes mellitus using conventional therapy.

DESIGN

Sixty-one children (aged 2.6 to 8.5 years) were studied on one night, at home, with blood collection occurring at dinner, bedtime/supper, 11 PM, 2 AM, and breakfast, with subsequent laboratory analysis.

RESULTS

The proportion of subjects with blood glucose levels less than 64, 55, 45, and 36 mg/dl (3.5, 3.0, 2.5, and 2.0 mmol/L) was 37.8%, 17%, 13%, and 8%, respectively. Nocturnal hypoglycemia was associated with younger age (< 5 years 57% vs 5 to 8.5 years 36%; p < 0.001) and lowered glycosylated hemoglobin levels (HbA1c) with a greater than 50% incidence of hypoglycemia seen in subjects with HbA1c levels of less than 8.5%. The average HbA1c concentration was lower in the hypoglycemic group than in the nonhypoglycemic group (7.8 vs 8.3%; p < 0.02). Nocturnal hypoglycemia occurred with increasing frequency throughout the night in subjects less than 5 years of age (dinner, supper, 11 PM, 2 AM, and breakfast incidences being 0%, 12.5%, 26%, 33%, and 30%, respectively) but not in those older than 5 years. Carbohydrate intake at supper did not prevent subsequent hypoglycemia. Blood glucose levels at 11 PM were poor predictors of subsequent hypoglycemia at 2 AM in either the group as a whole or in the children less than 5 years of age. Symptom recognition of nocturnal hypoglycemia was decreased in younger children (< 5 years (36%) > 5 years (58%)), in those with a lower HbA1c, and when hypoglycemia occurred at breakfast rather than at dinner (0% vs 50%).

CONCLUSIONS

The incidence of nocturnal hypoglycemia in young children with insulin-dependent diabetes mellitus receiving conventional therapy is unacceptably high and is increased with lowered age and HbA1c concentration; the condition is often asymptomatic. Early-morning hypoglycemia is poorly predicted by a blood glucose determination at 11 PM and is not prevented by carbohydrate intake at supper. In younger children, blood glucose profiles should include early-morning measurements.

Nocturnal hypoglycaemia and sleep disturbances in young teenagers with insulin dependent diabetes mellitus

OBJECTIVE

To determine the effect of nocturnal hypoglycaemia on sleep architecture in adolescents with insulin dependent diabetes mellitus (IDDM).

DESIGN

20 adolescents with IDDM (mean age 12.8 years, mean glycated haemoglobin (HbA1c) 8.9%) were studied on one night. Plasma glucose was measured every 30 minutes and cortisol and growth hormone levels every 60 minutes. Sleep was recorded using standard polysomnographic montages, and sleep architecture was analysed for total sleep time, stages 1-4, rapid eye movement, fragmentation, and arousals.

RESULTS

Six subjects (30%) became hypoglycaemic (five subjects < 2.5 mmol/l), with one being symptomatic. There were no differences in age, HbA1c, duration of diabetes, or insulin regimen between hypoglycaemic and non-hypoglycaemic subjects. Hypoglycaemia was not predicted by glucose measurements before bed. There was no detectable rise in plasma cortisol or growth hormone concentrations during hypoglycaemia. Sleep architecture was not disturbed by nocturnal hypoglycaemia with no differences found in sleep stages, fragmentation, or arousals.

CONCLUSIONS

Nocturnal hypoglycaemia is a common and usually asymptomatic complication of treatment in adolescents with IDDM. Moderate hypoglycaemia has not been shown to affect sleep architecture adversely. These findings are consistent with, and may explain, the observation that severe hypoglycaemia, with consequent seizure activity, is more common at night than during the day. Counterregulatory hormone responses to nocturnal hypoglycaemia may be less marked than with similar degrees of diurnal hypoglycaemia.

Frequency and morbidity of severe hypoglycaemia in insulin-treated diabetic patients

To estimate the frequency and morbidity of insulin-induced hypoglycaemia, a retrospective survey was undertaken of the frequency of severe hypoglycaemia in 600 randomly selected patients with insulin-treated diabetes who were attending a large diabetic outpatient clinic in a teaching hospital. The resulting morbidity (hypoglycaemia-related injuries, convulsions, and road traffic accidents) was ascertained in 302 patients. One hundred and seventy-five (29.2%) of the 600 patients reported a total of 964 episodes of severe hypoglycaemia in the preceding year, giving an overall frequency for the group of 1.60 episodes patient-1year-1. The frequency of severe hypoglycaemia which was documented in 544 Type 1 (ketosis prone) diabetic patients was double that observed in a subgroup of 56 Type 2 diabetic patients who were being treated with insulin (1.70 vs 0.73 episodes patient-1year-1). In the subset of 302 patients, those who had experienced severe hypoglycaemia had greater morbidity associated with an estimated rate of injury of 0.04 injuries person-1year-1. Twenty (6.6%) patients reported a total of 37 convulsions associated with hypoglycaemia, 5 of which had occurred in the preceding year (0.02 convulsions person-1year-1). Five patients reported road traffic accidents in the preceding year which had been caused by hypoglycaemia. The only reliable predictors of severe hypoglycaemia were a history of previous severe hypoglycaemia (p < 0.001), a history of hypoglycaemia-related injury (p < 0.001) or convulsion (p < 0.001), and the duration of insulin therapy (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)