We performed a retrospective observational study examining long-term outcomes of patients, aged >55, admitted to the ICU who received RRT for AKI. We studied 352 patients over a median duration of 32.7 months. We found that, across all age groups, in-hospital and post-discharge mortality rates were very high. Compared to the rest of our cohort, older patients had a higher rate of long-term dialysis dependence and a lower QOL as assessed by EQ-5D and VAS scale. More importantly, we found that their QOL was significantly lower than an age/sex matched reference population. A higher proportion of them experienced pain, mobility limitation, depression and/or required help for their daily activities.
Long-term follow-up studies of patients undergoing RRT have reported similar mortality rates to our series (51.9%) ranging between 35 % and 71% [5-9, 11, 18, 19] The even higher mortality of >75 yo patients (73.5%) was also observed in other works: it was 61.7% in a Korean series (562 patients) and 71% in a Croatian series (178 patients) [8, 9]. This rate is not that different to the mortality observed in a group of old (75-84 yo) ICU patients who did not receive RRT (63%)[20].
Similarly, the low rate of dialysis dependence among ICU survivors is consistent with previous findings with reported rates around 5% [5, 6]. A higher (23%) rate was reported by Prskalo et al [9], however the follow-up in this study was only four weeks.
Our finding that ICU survivors <75 yo had a similar QOL than the reference population [15], is consistent with data from Finland, where ICU survivors were found to have similar QOL compared to their baseline (pre-ICU) value, 6 months after discharge from ICU. This finding was observed in both AKI and non-AKI patients [19] as well as RRT and non-RRT patients [7]. In these two studies median age was respectively 62 and 65 yo.
However, we observed a lower than predicted QOL in >75 yo survivors which, to the best of our knowledge, had not been described in this setting before. Most studies reporting QOL in >80 yo ICU survivors have suggested a similar to pre-admission QOL [2]. However, among those studies very few patients had received RRT and the majority of those died.
This study has several strengths. We studied all consecutive patients who received RRT for AKI in our ICU during a 2.7 years period. Long-term mortality data were obtained from national statistics bureau. Hence, we are able to report reliable long-term outcomes in all patients. We managed to run the survey with a large proportion of the survivors.
However, our study also has some limitations worth discussing. First, due to our retrospective design, we were not able to record pre-admission QOL. This limitation was, in part, overcome by the ability to compare QOL with predicted values based on local reference population data. Second, this is a single center study. In particular, indications for RRT were not standardized and may not be consistent throughout the study period, in addition to being different to other centers. However, mortality rate and renal recovery rates in our study were similar to those observed in other studies suggesting some form of external validity. Third, the running of the survey over the phone in geriatric patients could be seen as problematic. However, the EQ-5D has been validated for over the phone circumstances and only one patient was excluded due to deafness. Fourth, the number of patients in the >75 yo group was small (15 patients) reflecting the very high mortality in this group. Our results should be confirmed by other studies. Fifth, the lower than predicted QOL in patients >75 yo could have been confounded by our long-term follow-up (> 3 years in more than 60% of patients in this group). Indeed, a faster deterioration has been observed in ICU survivors compared to general population [21]. On the other hand, this long follow-up period might have selected healthier and stronger patients, because they survived a longer period and finally their QOL could be overestimated. Sixth, in the absence of a Swiss calibration, we used the French calibration to compute health utility. This appeared as a logical choice given the geographical, cultural and linguistic proximity of our region to France. Seventh, given the long term follow-up, some patients might have had multiple ICU admissions or other life events that might have altered their survival and QOL. This limitation is common to all long term follow-up studies. Finally, our study might have been underpowered to demonstrate significant difference in terms of mortality or dialysis dependence between our patient groups. Indeed, a trend for higher mortality and dialysis dependence was observed.
The observation of a lower QOL in G3 patients can appear puzzling since those patients had a lower median ICU LOS. This finding might be related to earlier withdrawal of medical care in older patients, but also demonstrates age-related limitation in post-acute illness recovery.
In summary, our study confirms that the population undergoing RRT is at very high risk of in-hospital and post-discharge death. It suggests that unlike their younger counterparts, patients >75 yo who survive to ICU discharge have a lower QOL compared to age-matched population. This, therefore, puts in question the appropriateness of RRT initiation in such a population. Age alone cannot justify limitations of medical therapy and factors, such as frailty [22] or low pre-admission VAS score [20], should be considered before age when discussing such limitations. Age should rather correspond to a modulating factor. In addition, patients' preference accounting for personal, cultural and educational elements must be taken into account. Our data, however, supports the view that such limitations should be discussed with those patients or their relatives either at the time of ICU admission or on RRT initiation.