The study involved 846 hospitalized patients on the medical ward of the Komfo Anokye Teaching Hospital. They included 406 patients with hyponatraemia as cases and 440 patients with normonatraemia as controls. The mean age of all participants was 52.1 ± 18.8 years and there were 460 (54.4%) males. There was no statistical difference in demographics data with respect to age and gender between the patients with hyponatraemia and those with normonatraemia as shown in Table 1.
Table 1 Showing a comparison of patients with hyponatraemia as compared to normonatraemia n=846
Variable
|
All cases
N= 846
|
Hyponatremia
N=406
|
Controls
N= 440
|
P value
|
Male gender n (%)
|
460 (54.4)
|
217 (53.5)
|
243 (55.2 )
|
0.604
|
Age (years) µ (SD)
|
52.1 ±18.8
|
51.5 ±19.0
|
52.7 ± 18.6
|
0.340
|
Serum Sodium (mmol/L) µ (SD)
|
133.8±7.6
|
128 ±7.8
|
138.0 ± 5.0
|
< 0.001
|
Serum albumin (g/L) µ (SD
|
33.9 ±19.8
|
31.6 ±16.5
|
36.1 ± 22.4
|
<0.001
|
Serum protein (g/L) M (IQR)
|
66.5 (58-75.6)
|
64 (55.2-75.6)
|
71 (63.3-78.8)
|
<0.001
|
Serum urea mmol/L M (IQR)
|
5.8 ( 3.44-12.0)
|
6.9 (3.9-15.8)
|
5.2 (3.3-9.6)
|
<0.001
|
Serum creatinine (µmol/L) M (IQR)
|
90 (61.1-170)
|
95 (61-232.5)
|
88 (62-144)
|
0.091
|
Mortality n (%)
|
227 (26.9%)
|
129 (31.8)
|
98 (22.3)
|
0.002
|
Duration of hospital stay (days) M (IQR)
|
6 (3-10)
|
7(4-10)
|
6 (3-10)
|
0.090
|
n,number; µ, mean; SD, Standard deviation; M, median; IQR, interquartile range; mmol, millimol; L, litre;g, grams; µmol/L, micromole per litre
The mean sodium concentration was 128.0 ± 7.8 mmol/L in the hyponatraemia group as compared to 138.0 ± 5.0 mmol/L among the normonatraemia group (p < 0.001). Serum albumin was also significantly lower in patients with hyponatraemia as compared to those with normonatraemia 31.6 ± 16.5 vs 36.1 ± 22.4 p value < 0.001. Median serum protein was also significantly lower in the hyponatremia patients as compared to those with normal sodium concentration. 64 (55.2–75.6) vs 71 (63.3–78.8), p < 0.001. All as shown in Table 1.
The most common medical conditions associated with hyponatraemia were infections 105 (25.9%), chronic liver disease 69 (17.0%), diabetes mellitus 68(16.8%) and chronic kidney disease in 66(16.3%) patients as shown in Fig. 1.
The most common medical conditions in the normonatraemia group were intracranial pathologies 131(29.8%), chronic heart failure 76 (17.3%), and infections in 72 (16.4%) all as shown in Fig. 2.
The proportions of some medical conditions varied in the hyponatraemia and normonatraemia groups. Infections, chronic kidney disease and diabetes mellitus were significantly of higher proportions in patients with hyponatraemia as compared to patients with normonatraemia. Malignancies and alcoholism did not vary significantly within the two groups. There were lower proportions of patients with heart failure and cranial pathologies in hyponatraemia groups as compared to those with normonatraemia. All as shown in Table 2.
Table 2 Showing the medical conditions associated with hyponatraemia as compared to normonatraemia n= 846
Medical condition
|
All patients
n=846
|
Hyponatraemia
n=406
|
Normonatraemia
n=440
|
P value
|
Infections
|
177 (20.9)
|
105 (25.9)
|
72 (16.4)
|
0.001
|
Malignancies
|
22 (2.6)
|
11 (2.7)
|
11 (2.5)
|
0.848
|
Heart failure
|
109 (12.9)
|
33 (8.1)
|
76 (17.3)
|
<0.001
|
Cranial pathologies
|
154 (18.2)
|
23 (5.7)
|
131 (29.8)
|
<0.001
|
Kidney disease
|
96 (11.4)
|
66 (16.3)
|
30 (6.8)
|
<0.001
|
Diabetes mellitus
|
98 (11.6)
|
68 (16.8)
|
30 (6.8)
|
<0.001
|
Liver diseases
|
116 (13.7)
|
69 (17.0)
|
47 (10.7)
|
0.008
|
Alcoholism
|
27 (3.2)
|
16 (3.9)
|
14 (3.18)
|
0.551
|
Infections were significantly higher in hyponatraemia patients as compared to normonatraemia patients 105 (25.9%) vs 72 (16.4), P = 0.001. As well as patients with chronic kidney disease 66 (16.3%) vs 30 (6.8%), p < 0.001 and in patients with hyperglycaemia 68 (16.8) versus 30 (6.8) p < 0.001 and those with liver disease. Malignancies and alcoholism did not vary significantly with hyponatraemia. There were proportionally lower patients with heart failure and cranial pathologies in the hyponatraemia group as compared to those with normonatraemia. All as shown in Table 2.
The highest proportion of mortality in the normonatraemia patients occurred in patients with hyperglycemia 10(33.3%), followed by liver disease 13(27.6%) and pain presentations 3 (25%) but mortalities did not vary significantly with diagnoses (P = 0.741) as shown in Fig. 2.
In-hospital mortality was significantly higher in patients with hyponatraemia as compared to patients with normonatraemia 129(31.8%) versus 98(22.3%) p = 0.002 as shown in Table 1. Hyponatraemia was associated with increased odds of in-patient mortality [OR = 1.62, (95% CI 1.18–2.22) and p = 0.002)] as compared to normonatraemia as shown in Table 4. Hypoalbuminemia was associated with increased odds of in-hospital mortality with OR of 2.08 (1.46–2.99, 95% CI, p < 0.001). Hyperglycaemia was significantly protective of in-hospital mortality [OR = 0.50 (95% CI 0.26–0.87, p = 0.012) as shown in Table 3.
Table 3 Showing the predictors associated with in-hospital mortality
Variable
|
Odds ratio
|
95% Confidence interval
|
P value
|
Male gender
|
1.14
|
0.84 - 1.58
|
0.375
|
Age greater than 50yrs
|
1.05
|
0.77 – 1.45
|
0.720
|
Hyponatraemia
|
1.62
|
1.18 - 2.22
|
0.002
|
Infection
|
1.01
|
0.68 - 1.49
|
0.932
|
Malignancies
|
1.92
|
0.71- 4.93
|
0.132
|
Heart failure
|
1.11
|
0.69 - 1.77
|
0.644
|
Cranial pathologies
|
0.87
|
0.57 – 1.32
|
0.498
|
Kidney disease
|
1.50
|
0.92 – 2.40
|
0.078
|
Hyperglycaemia
|
0.50
|
0.26 - 0.87
|
0.012
|
Liver disease
|
1.39
|
0.89 – 2.16
|
0.123
|
Alcoholism
|
0.67
|
0.22 – 1.72
|
0.389
|
Hypoalbuminaemia
|
2.08
|
1.46 - 2.99
|
<0.001
|
Hypoalbuminaemia, serum albumin of less than 35g/L; yrs, years; hyperglycaemia, serum random blood glucose above11.1mmol/L on admission
In-hospital stay was longer in patients with hyponatraemia than normonatraemia 7 (4–10) vs 6 (3–10) but not statistically significant p = 0.09 as shown in Table 1
Multiple logistic regression shows that serum sodium concentration [OR = 0.94 (95% CI 0.92–0.97) (p < 0.001)] and serum albumin concentration [OR = 0.97 (95% CI 0.94–0.99) (0.007)] where significantly protective of mortality. Serum protein, urea, creatinine and length of hospital stay were not significant predictors of in-hospital mortality as shown in Table 4.
Table 4 Showing the multiple logistic regression independent variable for mortality
Variable
|
Z
|
Standard error
|
Odds ratio
|
95% confidence interval
|
P value
|
Serum sodium
|
- 4.14
|
0.013
|
0.93
|
0.92-0.97
|
<0.001
|
Serum albumin
|
- 2.62
|
0.013
|
0.96
|
0.94 -0.99
|
0.009
|
Total protein
|
0.19
|
0.009
|
1.00
|
0.98-1.02
|
0.846
|
Serum Urea
|
1.39
|
0.009
|
1.01
|
0.99-1.03
|
0.164
|
Serum creatinine
|
- 0.42
|
0.002
|
0.99
|
0.99-1.00
|
0.675
|
Length of hospital stay
|
- 1.21
|
0.139
|
0.98
|
0.96-1.01
|
0.227
|