The Dialysis Outcomes and Practice Pattern Study (DOPPS) study conducted in 11 countries showed that the highest mortality of HD patients was observed in the first month after dialysis initiation (10). It is well documented that the mortality of HD patients is higher within three to six months after dialysis initiation. According to the United States Renal Data System (USRDS) report (1), all-cause mortality peaked about two months after dialysis initiation in HD patients. Therefore, the high mortality rate of dialysis patients in the early stage of HD should not be ignored. This study developed and validated a model for predicting all-cause mortality risk among incident HD patients using five easily available baseline variables, with the overarching goal of informing patients about their future risk up to six months.
The five predictors were: age, temporary dialysis catheter, intradialytic hypotension, use of ACEi or ARB, and use of loop diuretics. Notably, they included traditional death risk factors and dialysis-related factors. The easy and calculable score described here was designed to identify HD patients who were at high risk of death during the first six months after initiating dialysis. This model would not only identify patients' risk factors for early death, but would also help health care workers to make targeted treatment measures in advance. Identifying death risk factors for dialysis patients in early stage can help initiate earlier interventions for those at risk, which include, but are not limited to, management of hypertension and hypotension, choice of the dialysis pathway, and strategies for the use of ACEi or ARB or diuretics in different populations.
In this study, multivariable analysis was performed using Cox regression models. Results showed that age was an independent risk factor for death in HD patients, with every one-year increase in age resulting in a concomitant 3% increase in the risk of death in dialysis patients. Given that elderly patients are prone to complicated complications with poor body resistance and cognitive decline, their quality of life decreases and mortality increases after initiation of dialysis(11). In particular, elderly HD patients who lived alone and did not have caregivers during or after the HD treatment had a higher risk of death. Therefore, elderly HD patients should be given special care by doctors and nurses as well as social welfare institutions.
Results also showed that patients who received temporary dialysis catheter had a higher risk of death compared to those who used arteriovenous fistula (AVF) to perform dialysis treatment. Previous studies have shown that the risk of death in patients using temporary dialysis catheter is 1.43 times higher than in HD patients who use AVF at the initial stage of dialysis (12). It is worth noting that the increased risk of death associated with temporary dialysis catheter may be caused by unplanned and delayed dialysis treatment, or associated with catheter-related infections. Studies have shown that about 13.3% of patients using dialysis catheters have positive blood culture results, and the risk of blood-borne infection in catheter patients is three times higher than in AVF patients (13). Therefore, effective evaluation of vascular conditions in HD patients before dialysis, preparation for establishment of dialysis pathway in advance, and increasing the proportion of AVF in the initial treatment may reduce the risk of death.
A previous study found that hypertension was one of the risk factors for predicting 3-year all-cause mortality in HD patients, which was caused by the increased incidence of cardiovascular and cerebrovascular diseases in dialysis patients (14). However, in this study we found that patients with intradialytic hypotension had a lower mortality compared to patients with normal or hypertension in the first six months after initiating dialysis. It has previously been reported that intradialytic hypotension is a common complication of HD patients, which may be associated with decreased blood volume, autonomic nervous dysfunction, cardiac dysfunction, and vascular dysfunction during dialysis (15). Notably, severe intradialytic hypotension may cause arrhythmia, occlusion of AVF, and shorter dialysis times. Many clinical studies have found that the occurrence of intradialytic hypotension can increase the risk of death in HD patients (16, 17). Results obtained in this study also found that intradialytic hypotension is a risk factor for death in HD patients, thus, clinicians should pay enough attention to this clinical complication.
Gamboa et al. (18) reported that the use of ACEi or ARB can inhibit the microinflammatory state in HD patients. Another study also found that application of ACEi or ARB in HD patients has different degrees of efficacy in hemodynamics, cardiovascular remodeling, cardiovascular events, all-cause death, and other aspects (19). Therefore, ACEi or ARB is one of the most commonly used antihypertensive drugs in HD patients. However, we found that HD patients using ACEi or ARB had a lower 6-month survival rate, which is an interesting finding with two probable causes. First, the use of ACEi or ARB may cause the occurrence of hypotension during dialysis which can lead to increased mortality in HD patients. Second, the use of ACEi or ARB is a common cause of hyperkalemia in dialysis patients, which is a risk factor of cardiovascular death in HD patients.
It has been reported that continued use of loop diuretics during the first year of dialysis is associated with lower hospitalization rates, lower intradialytic hypotension rates, and lower interdialysis weight gain, but it had no effect on mortality (20). Herein, results showed that continued use of loop diuretics after HD treatment can reduce the risk of death within six months. In addition to increasing urine output, loop diuretics can improve sodium excretion by about 20% and is unaffected by the levels of glomerular filtration rate (GFR) (21). It is well known that better volume control and urinary sodium excretion are beneficial to fluid overload. Moreover, urinary potassium excretion allows the patient to eat more freely, which can improve the quality of life of dialysis patients. Therefore, loop diuretics are the most commonly used and most effective in patients with ESKD. The findings of this study also recommend the use of loop diuretics in dialysis patients in the first six months.
However, this study had some limitations. First, the sample size was small, which may increase the possibility of type II errors. Notably, only variables with univariate analysis results of P < 0.05 were selected for Cox analysis, which to some extent lost the related risk factors affecting death. Therefore, a larger sample size study should be conducted to confirm our findings. Second, although the robustness of our nomogram was subjected to extensive internal validation using bootstrap testing, the universality was uncertain for other HD patients. Thus, external assessment should be conducted in wider HD populations.