Short Term Hospital Outcome of Ischemic Stroke Patient Presenting with Hyponatremia

Introduction

Stroke remains a leading cause of death world-wide [1]. World Health Organization defined stroke as a clinical syndrome occurring due to sudden cerebral dysfunction, producing focal or global neurological deficit, persisting for more than24 hours, or the patient dieswithin24 hours, which is vascular in origin, non-traumatic in nature [2]. Incidence of stroke in Bangladesh is 2.55/1000 population/ year in both sexes [3]. Acute ischemic Stroke affects 795,000 people every year, is the fourth leading cause of death and the most common cause of long term disability in the United States [4]. It is the third most common cause of mortality and most common cause of chronic disability in developed countries. Modifiable risk factors for store are dyslipidaemia, hypertension, diabetes mellitus, valvular heart disease, atrial fibrillation, smoking, ischemic heart disease, sedentary life style and non-modifiable risk factors are age, gender, heredity, high fibrinogen [5]. Hyponatremia is the most common electrolyte abnormality encountered in the hospitalized patient, and the reported prevalence has varied with the nature of the patient population and health care setting studied [6, 7, 8, 9, 10]. It frequently develops during the course of hospitalization as a complication of acute illness or a consequence of therapeutic interventions [11, 12, 13, 14]. Hyponatremia among hospitalized patients has been associated with increased morbidity and mortality, but whether the mortality is associated with hyponatremia itself or the underlying illness remains unclear [15, 16, 17]. Rapid changes in the cell volume as a result of hyponatremia can have profound effects on tissue and organ function, especially the brain. A rapid reduction in plasma sodium concentration can cause brain cell odema, neurological symptoms, including headache, nausea, lethargy and disorientation. If plasma sodium concentration rapidly falls below 115 to 120 mmol/L brain swelling may lead to seizures, coma, permanent brain damage, and death [18]. This study was conducted to predict the short term outcome of ischemic stroke presenting with hyponetremia.

Methods

This prospective observational study was conducted in Neurology and Medicine Wards of Mymensingh Medical College Hospital, Mymensingh, Bangladesh from March 2014 to February 2015 over a period of one year. Patients diagnosed as ischaemic stroke admitted in the Neurology and Medicine Wards of Mymensingh Medical College Hospital were primarily enrolled as study population. Of them, 50 patients were selected as hyponatremic (Serum sodium concentration < 135 meq/L) and another fifty patients were selected as normonatremic (serum sodium = 135- 145 meq/L). After taking written consent patients or eligible attendants were questioned about past and family (parents and siblings) history of stoke. The age, sex, time delay from symptom onset to hospital arrival and risk factors were recorded in a standard and pre-tested structured questionnaire. Serum electrolyte, fasting glucose and lipid profile were measured. All data were compiled and edited meticulously. Quantitative data was expressed as mean & standard deviation and qualitative data was expressed as frequency and percentage and data was analysed by Chi- square (χ2) test in case of qualitative data and unpaired t test in case of quantitative data. A probability (p) of less than 0.05 was considered statistically significant. Statistical analysis was performed by using SPSS 12.0.

There was no significant difference in age, gender, smoking habit, systolic BP and diabetic between hyponatemic and normonatremic ischemic patients. But diastolic BP was significantly lower in hyponatemic patients than that of normonatremic patients (88.4 ± 8.5 vs 92.3 ± 8.6).

There was no significant difference in TC, HDL and LDL between hyponatemic and normonatremic ischemic patients. But Triglyceride was significantly higher in hyponatemic patients than that of normonatremic patients (167.1 ± 42.7 mg/dl vs 153.5 ± 43.9 mg/dl).

There was no significant difference in K+ and Cl- between hyponatemic and normonatremic ischemic patients.

Clinical features were almost similar in both groups except convulsion and unconsciousness. Convulsion and unconsciousness were observed significantly higher in hyponatemic patients than that of normonatremic patients.

Mortality and morbidity rate was higher in hyponatremia patients (12.0% and 81.8%) than that of normonatremia patients (4.0% and 72.9%) but the difference was not statistically significant (p>0.05).

Table 6 shows association of mRS score with hyponatremia. Mean mRS at the time of admission was 4.16 ± 1.03 and 3.74 ± 0.75 in hyponatremia and normonatremia patients respectively. The difference was statistically significant (p<0.05). Similarly mean mRS at the time of discharge was 3.56 ± 1.21 and 3.04 ± 0.98 in hyponatremia and normonatremia patients respectively. The difference was statistically significant (p<0.05).

Discussion

In this study, males were predominant than females in both groups indicating that stroke is a male predominant disease. Similar result was seen in the study of Goldberg, et al. [19] and Zhang, et al. [20] but opposite result was seen in the study of Rodrigues, et al. [21] where female is slightly higher in number than male in both groups. Stroke, either ischaemic or haemorrhagic, is more prevalent in men than in women [22]. In the present study mean age in group A and group B were 64.8 ± 12.3 years and 60.9 ± 13.1 years respectively. Almost similar result was seen in the study of Goldberg, et al. [19]. Slightly higher mean age was seen in both groups in the study of Rodrigues, et al. [21]. In this study 27 (54.0%) patients and 21 (42.0%) patients were smoker in group A and group B respectively. Almost similar percent of smoker was seen in both groups in the study of Rodrigues, et al. [21] and Goldberg, et al. [19]. Devkota, et al. [23] reported 58.3% of stroke patients had smoking history. It was seen in this study that diabetes mellitus was in 14 (28.0%) and 11 (22.0%) patients in hyponatremia patients and normonatremia patients respectively. Diabetic was more in hyponatremia patients (44%) than that of normonatremia patients (20%) [19]. Overall incidence was 25% which is consistent with the study of Uddin, et al. [24] where diabetic patient was 20% in ischaemic stroke patients. Diabetic was seen in 38.4% and 28.5% patients in hyponatremia and normonatremia patients respectively in the study of Rodrigues, et al. [21]. In this study, it was seen that lipid profile levels were worse in hyponatremia patients than that of normonatremia patients. Mortality rate was higher in hyponatremia patients (12.0%) than that of normonatremia patients (4.0%). Rodrigues, et al. [21] showed that mortality was higher in hyponatremia patients than normonatremia patients. In-hospital mortality was 13.5% and 10.5% in hyponatremia and normonatremia patients respectively among ischaemic patients Rodrigues, et al. [21] which is consistent with our result in case of hyponatremia. Mortality rate was higher among hyponatremia patients than that of normonatremia patients [25]. Morbidity rate was higher in hyponatremia patients (81.8%) than that of normonatremia patients (72.9%) but the difference was not statistically significant (p>0.05). Mean mRS at the time of admission was 4.16 ± 1.03 and 3.74 ± 0.75 in hyponatremia and normonatremia patients respectively. The difference was statistically significant (p<0.05). Similarly mean mRS at the time of discharge was 3.56 ± 1.21 and 3.04 ± 0.98 in hyponatremia and normonatremia patients respectively. The difference was statistically significant (p<0.05).

Conclusion

This study result shows that mRS score is significantly higher in hyponatremia patient then normonatremia patients but hyponatremia does not have significant mortality and morbidity in acute ischaemic stroke patient in comparison with normonatrimic stroke patients. So, it can be concluded that outcome of ischaemic stroke patients with hyponatremia is worse than ischaemic stroke patients with normonatremia.