Hypoglycaemia in Clinical Diabetes

SIGNS AND SYMPTOMS OF HYPOGLYCAEMIA 193Table 9.1 Example of classification of hypoglycaemia (data sourced from ISPAD Consensus Guidelines,2000)GradeMild (Grade 1)Moderate (Grade 2)Severe (Grade 3)DescriptionAware of, responds to and self-treats the hypoglycaemiaCannot respond to hypoglycaemia and requires help fromsomeone else, but oral treatment is successfulSemi-conscious or unconscious or in coma ± convulsions andmay require parenteral therapy (glucagon or IV glucose)PREVALENCE OF HYPOGLYCAEMIAAs the definition of hypoglycaemia has been controversial, studies of prevalence have oftenused variable definitions, both for daytime hypoglycaemia and for that occurring duringsleep. Hypoglycaemia is notoriously under-reported, as episodes, particularly mild ones, arequickly forgotten. Even severe episodes may be overlooked. The individual themselves mayhave amnesia for the event and, if it occurred away from their normal environment, nobodymay document what took place.A number of studies have examined the prevalence of severe hypoglycaemia in thepaediatric population (Table 9.2). Some studies included only episodes of coma/convulsionwhereas others also included those events in which neurological impairment was severeenough to require intervention. Hypoglycaemia has been shown to be a significant problembut, given the methodological complexities, prevalence rates of severe hypoglycaemia havevaried greatly from 3.1 to 85.7 episodes per 100 patient-years. It is likely that less severeepisodes are much more common and under-reported.Nocturnal HypoglycaemiaStudies have also examined the prevalence of nocturnal hypoglycaemia. In these studiesa biochemical rather than a symptomatic definition of hypoglycaemia was used and hasbeen very variable, ranging from 3.0 to 3.8 mmol/l. The prevalence of hypoglycaemia hasvaried from 10 to 55% but it is noticeable that the more recent studies have detecteda higher prevalence (Beregszaszi et al., 1997; Lopez et al., 1997; Porter et al., 1997;Matyka et al., 1999a). The majority of these episodes do not wake the patient and, ineveryday life, a great number of episodes of nocturnal hypoglycaemia will be completelyundetected.SIGNS AND SYMPTOMS OF HYPOGLYCAEMIADaytime HypoglycaemiaThe classical symptoms of hypoglycaemia, as described in adults (Chapter 2), are classifiedinto three distinct groups: autonomic, neuroglycopenic and non-specific (Deary et al.,1993). In adults the sympathoadrenal response during hypoglycaemia is primarily responsiblefor the classical autonomic symptoms which alert the individual to the falling glucose