This retrospective study examined the effectiveness of vital signs to predict hypoglycaemia in patients presenting with AMS to avoid unnecessary BG measurements by paramedics attending emergency medical conditions in pre-hospital settings. In this study, there were statistically significant differences in all vital signs between non-hypoglycaemic and hypoglycaemic patients. Among the vital signs evaluated, sBP and BT may be effective in predicting hypoglycaemia, and AUC indicated that BT could be the most useful vital sign for differentiating between hypoglycaemic and non-hypoglycaemic episodes.
In our study, the hypoglycaemic group had more abnormal vital signs than the non-hypoglycaemic group. Wide variability in bioprotective responses can occur in hypoglycaemia. Such variabilities include but not limited to decreased insulin secretion, increased glucagon, epinephrine, and norepinephrine secretion associated with the activation of the sympathetic-adrenal function system. These responses occur early in the course of low BG levels and cause an increase in sBP, RR and HR [6–8]. Our study findings were consistent with these previous studies, and the hypoglycaemic group tended to have increased sBP, RR and HR compared to the non-hypoglycaemic group. In terms of the association between hypoglycaemia and BT, we found that the higher the BT, the lower the likelihood of hypoglycaemia. There have been reports that hypoglycaemia is associated with hypothermia , which appeared to be induced by glucose deficiency in the cells of the hypothalamic centre regulating BT .
Among these vital sign changes, sBP and BT may be the most useful indicators for predicting hypoglycaemia in our study. When sBP was less than 100 mmHg and BT was more than 38 °C, the LRs of hypoglycaemia were very low (0.12 and 0.15, respectively). This finding is supported by previous studies. Ikeda et al. reported that high sBP was associated with brain lesions accounting for impaired consciousness observed in patients with AMS , and higher BT was associated with infectious diseases such as sepsis in other studies [12, 13].
Although early detection and treatment of hypoglycaemia are important, previous studies have found that BG measurement prolongs the field time of emergency services by 2–5 minutes in Japan [14, 15]. This delay can be fatal and may be damaging in patients with impaired consciousness with other critical conditions such as stroke or sepsis as found in our study. Therefore, it is ideal to avoid unnecessary BG measurement in these patients and transfer them to the hospital as early as possible.
Evaluating the known risk factors for hypoglycaemia, such as history of diabetes mellitus and renal dysfunction, is useful to predict it [16–18], though impaired consciousness makes it difficult to obtain clinical information from patients. Vital signs represent important information that can be obtained over a short period of time even in patients with impaired consciousness, and the results of our study indicated that certain changes in vital signs such as sBP < 100 mmHg or BT ≥ 38 °C may help paramedics to make decisions to not to perform BG measurement and avoid prolonged pre-hospital care. In this study, nine patients in the non-hypoglycaemic group were diagnosed hypoglycaemia. The BG levels of eight patients in pre-hospital settings were 50–65 mg/dL, This indicated an undeniable possibility of hypoglycaemia. One patient was found at the history interview to have been administered oral glucose by a family member before the paramedic performed BG measurement. Based on these results, it may be necessary to discuss the validity of the hypoglycaemia criterion hypoglycaemia as less than 50 mg/dl. In contrast, these nine patients did not show vital signs (sBP < 100 mmHg, BT ≥ 38 °C) that would indicate that the cause of AMS is likely to be non-hypoglycaemic, and we believe that the validity of the results of this study will not change significantly.
This study has several limitations. First, the number of patients with AMS who did not receive BG measurements, despite satisfying the criteria for the BG measurement protocol, was highly dependent on the paramedics’ choice on whether to perform a BG measurement. It could not have been determined which patients were transported to the hospital without BG measurement. Because brain injuries such as stroke are considered an emergency and are less likely to be associated with hypoglycaemia , BG measurement may not have been performed if the paramedics suspected such diseases. Patients with brain injury often develop fever and hypertension [11, 19], and the results of our study would not have been significantly different from the present results even if they had been monitored. Second, in this study, the possibility of hypoglycaemia may not have been adequately assessed by the paramedics with regard to patient background including past medical history and medications, which may have influenced the decision to perform BG measurement. Further, there was a bias in patient selection, though we think that this is a practical consequence of paramedical field activities. Finally, the final diagnosis other than hypoglycaemia was recorded only for those patients transported to a single institution, and the possibility of comorbidities other than hypoglycaemia was not sufficiently examined. Thus, further investigations, including enrolling cases from other institutions, is necessary.