Although there are many differential diagnoses of the cause of impaired consciousness, it is difficult to obtain a detailed history and physical examination of patients with severely impaired consciousness. The concordance rate between prehospital and final diagnoses is approximately 60% [9]. In this retrospective, observational study, we examined patients’ age, sBP, need for airway management, and symptoms. In addition, we identified characteristics for the differential diagnosis of patients with severely impaired consciousness using JCS Ⅲ-digit codes. Notably, stroke and cardiovascular disease have significantly higher mortality rates, and it is crucial to diagnose these diseases early and accurately. Here, stroke was the most common cause of severely impaired consciousness, similar to that in a previous study [10]. It is crucial to recognize stroke because early treatment of cerebral infarction, including thrombolytic therapy and endovascular treatment, is associated with patient prognosis [11]. Here, we highlighted age, sBP, and the presence of airway abnormalities as characteristics for the differential diagnosis of severely impaired consciousness. Patients with intoxication or psychiatric disorders were significantly younger, and those with stroke had the highest sBP, which showed a significant difference compared with most differential diagnoses other than seizures and metabolic disorders. However, age and sBP are important factors in differentiating impaired consciousness, and patients with impaired consciousness caused by intoxication are frequently younger [12]. Notably, when the sBP is higher than 180 mmHg, the cause of impaired consciousness is probably stroke [13]. The results were consistent with this study and suggested that age and sBP are important factors in the differential diagnosis of severely impaired consciousness.
Therefore, airway obstruction should be considered in patients with severe impaired consciousness. Although many patients with stroke-induced severely impaired consciousness require intubation, those with intoxication-induced severely impaired consciousness can be monitored without intubation [14]; therefore, it is crucial to confirm the necessity of airway management for patient management and to estimate the causes of impaired consciousness. Here, airway obstruction was most frequently observed in patients with severely impaired consciousness due to stroke, accounting for 73.5% of cases. Among the conditions presenting with impaired consciousness, stroke was significantly more likely to present with airway obstruction, and stroke should be the first differential diagnosis in patients with impaired consciousness presenting with airway obstruction. In contrast, airway obstruction was significantly less common in patients with intoxication or psychiatric disorders. In addition to previous reports, the absence of the need for airway management despite severely impaired consciousness may be a useful finding when considering intoxication or psychiatric disorders as possible causes.
Clinical symptoms are significant in diagnosing stroke; however, it is challenging to confirm facial nerve palsy, paralysis, or dysarthria in the presence of severe impairment of consciousness. Here, among the patients diagnosed with a stroke, 19.1% had paralysis or abnormal limb position, while 45.6% had ocular abnormalities, including conjugate eye deviation or pupillary irregularities. Notably, conjugate eye deviation is found in 45–50% of strokes and is associated with stroke severity and large vessel occlusion [15–17], making it important to check the ocular status in patients with severely impaired consciousness for early diagnosis and treatment of stroke.
This study has several limitations. First, this was a single-center observational study. Our institution is a tertiary care hospital and is commonly selected as an institution for patients with severely impaired consciousness with JCS Ⅲ-digit codes. However, it is yet to be confirmed how many patients with severely impaired consciousness are transported to other institutions. Second, the prevalence of symptoms before impaired consciousness (e.g., headache and chest pain) and comorbidities such as atrial fibrillation are often crucial for differential diagnosis, and we have not examined these factors. In addition, for patients with stroke, the evaluation of abnormal limb positions and ocular abnormalities may not be accurate for some paramedics. Although early transport is vital for patients with severely impaired consciousness, obtaining as much medical history and physical examination as possible and making a comprehensive assessment of the patient's condition is important. Finally, diseases classified as others as the final diagnosis were not statistically validated. However, if these cases are increased and verified, the rates of airway obstruction and mortality may be higher.