Geriatrics intensive care unit : Outcome and risk factors for in hospital mortality *

OBJECTIVES: To evaluate outcome and risk factors, particularly the (APATCHE II) score in elderly patients after admission to a geriatrics intensive care unit (ICU). Methods: A cross sectional study of patients ≥ 60 years admitted to the intensive care unit (ICU) of the Geriatrics department at Ain Shams University Hospital over 2 years period. We recorded age, sex, previous medical history, primary diagnosis, date of admission and discharge or death and APACHE II score on admission. Results: 202 patients admitted to the ICU were studied. The mean ICU mortality rates for these patients were (32, 5%), the mean APATCHE II score was (19.07). 27.3% of patients who died had hypokalemia and 43.2% had hyponatremia. Conclusion: ICU mortality rate are higher in elderly patients particularly with long ICU stay and hyponatremia.


INTRODUCTION
In many countries average age and life expectancy of the population are increasing [1].Because of this, a growing number of older patients are being admitted to the intensive care unit (ICU).There is some evidence to suggest that age is a restrictive factor for ICU admission [2,3] and that it determines treatment intensity [4,5].However, even though an increased risk of mortality accompanies old age [6][7][8][9][10], most studies suggest that age alone does not represent a strong predictor for mortality [4].We have studied risk factors for in hospital mortality in elderly patients, in particular we have evaluated the Acute physiology and chronic health evaluation (APATCHE II) scoring system [11].

MATERIALS AND METHODS
A single center, cross sectional study was carried out in the ICU of the Geriatrics Department at Ain Shams University Hospital in Cairo Egypt from April1/2011 through April 1/2013.
During this period of two years, all patients admitted in the ICU were recruited for the study.After admission, the patients were divided into survival group (those who were discharged from the ICU after improvement) and non survival group (those who died in the ICU).
The study was approved by the University and Hospital Ethics Committees.
Data collection was done for all participants including patients' demographics and medical history, length of stay in the ICU.
The Acute Physiology and Chronic Health Evaluation (APACHE) II score incorporates 12 physiologic variables, age, and an assessment of chronic diseases in individual patients.

STATISTICAL ANALYSIS
Data was analyzed using the statistical program SPSS for window, Release 16.All values are reported as mean ± SD., two tailed students t-test is used for continuous variables.Chi-square and Fisher's exact tests were used to compare categorical variables between survival and non survival group.Multiple logistic regression analysis was performed to determine the independent risk factors for in hospital mortality.Relative risk is given with the 95% confidence interval (CI).Pearson's correlation coefficient and linear regression were used to evaluate the in hospital risk factors for mortality.A p value of <0.05 was considered as statistically significant.

RESULTS
A total of 202 patients' ≥60 years old were studied.The mean age of the studied groups was 69.9 years.The study included 68 (33.7%) males and 134 (66.3%) females.31.6% of patients were admitted with diabetes mellitus complications, 19, 8% with cardiovascular complications, 13.8% with disturbed level of conscious and 12.8% with pulmonary complications.
114 patients (56.4%) were discharged from ICU after improvement while patients (43.6%) were died during ICU stay.The mean lengthy of ICU stay was 7.03 days among the survival group and 10.15 days among the non survival group with high statistical significant difference (p = 0.004) (Table 1).
The mean APATCHE II score for all subjects was 19.07 and among the non-survival group was 22.77.The score was significantly higher in non survival compared with survival group with high statistical significant difference (p = 0.000) (Table 1).
68.2% of the non-survival group were females with no statistical significant difference.There was negative correlation between age and length of ICU stay with no statistical significant difference.The mean death rate for all subjects was 32.5% and 42.5% among the non-survival group the rate was significantly higher in non-survivals compared with survivals with high statistical significant difference (p = 0.000).There was a positive correlation between age and death rate with no statistical significant difference (Table 2).
27.3% of non-survival group had hypokalemia and 43.2% had hyponatremia with no statistical significant difference (Table 3).

DISCUSSION
Age was strongly associated with the severity of illness scores [12][13][14], but even when adjusted for the degree of physiological impairment, age remained a strong predictor of mortality.This finding is consistent with previous studies, which evaluated the severity of illness upon admission to the ICU through the APS application and differs from many others that found no association between age and mortality [15,16].Although age has frequently been examined as a prognostic factor related to mortality of patients admitted to the ICU, few prior studies have provided quantitative estimates of increased risk associated with specific age intervals.Most of these studies adopted different selection criteria when defining an elderly population, mainly ranging from 60 to 85 years of age and not differentiating between various age intervals [15,17].In the current study, there is positive correlations between age and death rate among the studied group and the mean age of the studied group was 69.9 years.Esteban et al. created a different model to determine a threshold of age that could best discriminate for ICU survival [18].However, our goal was to evaluate outcome and risk factors for in hospital mortality in elderly patients after ICU admission.
Recent studies have revealed important data related to the short-and long-term outcomes of elderly patients.In a study done by Castillo et al. they show that ICU mortality rates for patients aged ≥ 75 years, varying from 22% to 31%, reflect differences in underlying diseases and severity of illness on admission and are mostly related to underlying disease, severity of illness, nosocomial infection, evolving organ dysfunction and quality of care after discharge from the ICU [19][20][21].Acute physiological impairment and diagnosis have much larger relative effects on prognosis than age [22].In the current study, death rate was higher in non survival group with high statistical significant difference.Risk prediction in elderly patients will become increasingly important over the next decade as the population age.More accurate prognosis predictions in critically ill elderly patients may help to decrease morbidity, improve therapeutic strategies and increase patients' quality of life [23].The APACHE II score measures severity of illness using a numerical score based on physiological variables selected because of their known impact on mortality: a more ill patient has more deranged values and a higher APACHE II score [24].As in other studies [25][26][27][28] the APACHE II score was sufficiently accurate in the present study to be able to predict mortality in individual patients.The APACHE II score alone can, therefore, is used to predict the outcome of critically ill elderly patients on admission.In the current study the mean APATCHE II score was higher among the non-survival group with high statistical significant difference.Disturbances in plasma sodium concentrations are a common clinical problem in patients admitted to the intensive care unit.Many cases of dysnatremia are acquired after a patient is admitted to the ICU, and the presence of dysnatremia is associated with poor prognosis.A recent study involving 151,486 adult patients from 77 intensive care units over a period of 10 years has demonstrated that many cases of dysnatremia are acquired in the intensive care unit, and that the severity of dysnatremia is associated with poor outcome in a graded fashion [29].Another study on the ICU patients with dysnatremias corroborated these findings, reporting that ICU-acquired hyponatremia and ICU-acquired hypernatremia were associated with increased mortality [30].In the current study (43.2%) of the non survivals group had hyponatremia.

CONCLUSION
Critically ill elderly patients have multiple system disorders and complications.We found that mortality in elderly patients was higher among those with prolonged ICU stay.The independent factors associated with the highest risk of death are the factors affecting the APATCHE II.The APACHE II score has excellent capability to predict mortality on the basis of values measured within the first 24 h after admission.This score does not, however, take into account the many factors that can influence patient outcome during the course of an ICU stay, so proper evaluation of changes in patient status over time is also important.

Table 2 .
Correlation between age and length of ICU stay, death rate.

Table 3 .
Relation between serum sodium, potassium and patients outcome.