QJM Advance Access originally published online on July 29, 2005
QJM 2005 98(9):661-666; doi:10.1093/qjmed/hci109
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Severe acute renal failure in adults: place of care, incidence and outcomes
From the 1Department of Renal Medicine, Hope Hospital, Salford, 2Manchester Institute of Nephrology and Transplantation, Central Manchester and Manchester Childrens’ Hospital, Manchester, 3Department of Renal Medicine, Birmingham Heartlands Hospital, Birmingham, and 4Department of Renal Medicine, Kent & Canterbury Hospital, Canterbury, UK
Address correspondence to Dr J. Hegarty, Department of Renal Medicine, Hope Hospital, Stott Lane, Salford, Manchester M6 8HD. email: janet.hegarty{at}srht.nhs.uk
Received 21 December 2004 and in revised form 31 May 2005
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Background: Department of Health guidelines recommend specialist critical care facilities for patients with severe single-organ failure such as acute renal failure (ARF). Prospective studies examining incidence, causes and outcomes of ARF outside of intensive care settings are lacking.
Aim: To determine the incidence, causes, place of care and outcomes of severe single-organ ARF.
Design: Prospective observational study.
Methods: For 6 weeks in June–July 2003, renal physicians were contacted daily, and ICUs on alternate days, to identify cases of severe single-organ ARF in the Greater Manchester area. All patients with serum creatinine 
500 µmol/l and not requiring other organ support were included. Patients with end-stage renal disease were excluded. Survivors were followed up at 90 days and 1 year from admission. Two independent consultant nephrologists assessed each case using anonymized summaries.
Results: Eighty-five patients had multi-organ ARF and 28 had severe single-organ ARF (380 and 125 pmp/year, respectively). Of those with single-organ ARF, 10 (36%) had known pre-existing chronic kidney disease. Renal replacement therapy (RRT) was required in 15 (54%). Total bed occupancy on ICUs relating to single-organ ARF was 59 days (range per patient 1–21). At 90 days, 18 (64%) were alive, and 17 (94%) had independent renal function. At 1 year, 4/18 had died, none receiving RRT at the time of death. Survivors all had independent renal function. In 13 (46%) cases there was an unacceptable delay in patient transfer and in 7 (25%), delays in assessment or commencement of RRT may have adversely affected patient outcome.
Discussion: The incidence of ARF treated with RRT is rising. Delays in transfer to renal services may result in inappropriate ICU bed use, and may adversely affect patient outcomes. There are serious problems regarding the appropriate use of expensive and limited medical resources in the critical care area, and in providing safe and effective treatment of patients with ARF.
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Introduction |
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When acute renal failure (ARF) requires specialist care such as renal replacement therapy (RRT), this entails specific resource allocation and planning. In population studies, the incidence of severe ARF has risen over the last 15 years, e.g. from 50 pmp/year requiring RRT in Grampian in 1989–1990, to 297 pmp/year in Scotland in 2002.1–6 This rise is likely to be multifactorial, including elements such as an increasingly elderly population, increased prevalence of chronic kidney disease (CKD), and improved survivals in ischaemic heart disease and diabetes mellitus.7 In addition, increased interventions in high-risk surgical and medical patients, and changing practices in intensive care medicine, whereby continuous RRT may be instituted early, due to perceived benefits in controlling the metabolic milieu, fluid status and cytokine removal, may also be important.6,8
The Department of Health report ‘Comprehensive Critical Care’ recommended that patients with a single failing organ system requiring observation or intervention should receive Level 2 care, i.e. high dependency care (HDU), while those requiring advanced respiratory support or basic respiratory support plus support of at least two other organ systems should receive level 3 care (intensive care).9 The report acknowledged that failure to provide appropriate level 2 care could lead to inappropriate pressures on level 3 care facilities. A comprehensive population-based assessment of adult critical care cases, demonstrated higher mortality rates when patients were cared for on general wards when the appropriate site of care was HDU.10 UK data collection on critical care facilities does not extend to level 2 facilities outside joint ICU/HDU settings. It has not been possible to separate single-organ failure ARF from multi-organ failure ARF in most previous reports.
The purposes of this study were to determine the incidence, causes and outcomes of severe single-organ ARF and the actual site of care versus the appropriate site of care.
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Methods |
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Patients
Patients in the Greater Manchester Renal Network with serum creatinine concentration
500 µmol/l, or requiring RRT, and not requiring other organ support, including inotropic and/or higher respiratory support, were deemed to have severe single-organ ARF, and were included in the study. Patients with end-stage renal disease receiving RRT were excluded. There are two centres with HDU facilities (six beds in total) for ARF in the Greater Manchester Renal Network covering a population of 2.6 million. This is coterminous with a Critical Care Network involving 13 ICUs and two cardiothoracic intensive care units. All network renal consultants and renal specialist registrars were contacted on a daily basis, and ICU/cardiothoracic ICUs on an alternate-day basis, for a 6-week period in June-July 2003, to identify patients suitable for study inclusion in the Greater Manchester area.
Data
Clinical and laboratory data points were collected at baseline and every 48 h until renal replacement therapy, recovery or death. Co-morbidity scores were generated using Charlson and Wright/Khan indices,11–13 which have been shown to predict long-term outcome in chronic disease. The Wright/Khan index specifically influences survival on renal replacement therapy. Patients were categorized by a senior clinician blinded to outcome on the basis of severity of illness at the time of referral as: A, requiring transfer to specialist critical care services within 24 h; B, requiring transfer to specialist critical care services within 48/72 h; or C, requiring review only. These categories (ABC) were based on an actual clinical priority approach for renal assessment and/or definitive place of care following referral.
Surviving patients were followed up at 90 days from referral and at 1 year. In addition, two independent consultant nephrologists assessed each case through anonymized summary sheets to determine whether, in their judgment, there was an unacceptable delay in transfer of patients to a an appropriate site of care, and whether any delay in assessment or commencement of RRT may have adversely affected outcome. Finally, ICU databases in all participating centres were interrogated for numbers and outcomes of patients receiving RRT as part of 2 organs supported over the same period. The age-related annual incidence of ARF was calculated from 2001 census population data for the Greater Manchester region.
Statistics
Normally distributed variables were summarized as means and standard deviations, with median and range used for skewed data. Analysis of variance and 
2 analysis were used for between-group comparisons of continuous and categorical variables, respectively. Confidence intervals for the incidences were calculated using the Normal approximation to the Poisson distribution.
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Results |
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In the 6-week period, 85 patients were identified as having multi-organ-failure ARF, and 28 had severe single-organ-failure ARF, yielding incidence rates of 380 pmp/year (95%CI 307–471) and 125 pmp/year (95%CI 86–181), respectively. The incidence of severe single-organ ARF was 68 pmp/year (95%CI 38–119) in those aged <65 years, and 351 pmp/year (95%CI 215–572) in those aged
65 years (Figure 1).
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The mean age of patients with severe single-organ ARF was 64.7±17.6 years; 19 (68%) were male and 10 (36%) were known to have pre-existing CKD. The primary reason for hospital admission was medical in 22 (79%) cases, elective surgery in two (7%) and emergency surgery in four (14%). There was a high burden of co-morbid disease, as measured by Charlson and Wright/Khan indices (see Table 1).
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The causes of renal failure are shown in Table 2. In the 6-week study period, a total of 23 patients required transfer to critical care services for single-organ ARF. At the time of referral, 13 (46%) patients were identified as category A (requiring transfer to critical care services within 24 h) and 6 patients (21%) were in category B (requiring transfer within 48/72 h). Nine (32%) patients were judged to require regular review in the first instance (category C); of these, 5 (55%) subsequently recovered renal function, and in the other four (44%), renal function deteriorated, necessitating transfer to critical care services within 48/72 h.
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There were thus in total 23 patients with single-organ-failure ARF requiring specialist renal care. Seven (30%) were transferred to an acute renal centre within the appropriate time interval, 4 (17%) were transferred to an ICU within the appropriate time interval (including one patient transferred to an ICU in another trust) and one patient had recovery of renal function. In total, 11 patients (48%) experienced a delay in transfer, five of whom were subsequently transferred to renal services and a further four transferred to ICU while awaiting specialist renal care. The average delay of transfer to a critical care setting was 6 days (1–12 days). Of the remaining two patients in the delayed transfer group, one had recovery of ARF, and in another renal replacement therapy was deemed inappropriate. At 90 days, there was no observed difference in mortality according to priority of referral: four patients (31%) in category A had died, two (33%) in category B and four (44%) in category C (p>0.05).
Sixteen (57%) patients with severe single-organ ARF required RRT, equating to an incidence of 72 pmp/year (95%CI 44–117). This compared to 380 pmp/year (95%CI 308–471) receiving RRT as part of two or more organs supported in multi-organ failure in an intensive care setting. In the 6-week study period, total bed occupancy on ICU relating to single-organ ARF was 59 days (range per patient 1–21), equivalent to 2.1 ICU days per patient with single-organ ARF requiring RRT. One patient was also intermittently admitted to their local ICU for haemodialysis over a period of 21 days. The mean length of hospital stay was 62.4 ± 45.5 days. No difference in length of stay was observed according to initial category of renal priority or actual time to renal or critical care support. In-patient mortality was 36% for single-organ ARF. This compared to 52% for those with multi-organ failure ARF. Twelve patients with multi-organ failure were transferred out of the Greater Manchester critical care network during the 6-week period of study due to lack of beds. At 90 days, 17/18 survivors of single-organ ARF had independent renal function. At 1 year from study close, four of the remaining 18 had died. None had been receiving RRT at the time of death. All survivors at 1 year had independent renal function.
All cases were anonymized for assessment by two independent consultant nephrologists. There was complete concordance that in 13 (46%) cases there was an unacceptable delay in transfer of the patient, and that in 7 (25%) cases, delays in assessment or commencement of renal replacement therapy may have adversely affected patient outcome. These possible adverse effects included inadequate fluid resuscitation on a general ward, fluid overload, cardiac arrest (n = 2), and failure to obtain diagnostic tests in a timely fashion (e.g. 17 days to renal USS in a patient with an obstructed kidney and contra-lateral small kidney; 12 and 30 days to renal biopsy, thereby delaying immunosuppressive treatment in one of the patients; 19 days to obtain a renal immunology screen).
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Discussion |
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This prospective study found an overall annualized incidence of 505 pmp/year (95%CI 421–609) of severe ARF in adults in the Greater Manchester area. The incidence of severe single-organ ARF was 125 pmp/year, with 72 pmp/year requiring RRT. This figure compares to 380 pmp per year receiving RRT as part of multi-organ support, giving a ratio of over 5.3:1. This overall incidence of 452 pmp/year (95%CI 372–550) requiring RRT for ARF is 50% higher that the last reported UK figure from 2002.6 As the incidence of ARF as part of a multi-organ failure syndrome was more than five times that of single-organ failure, the bulk of the increase in incidence of RRT in our study compared to historical reports is likely to be in multi-organ failure support. This may be partly as a result of changing ICU practice, with intensivists prescribing RRT for extended indications; the commonest reason for initiating RRT in ICUs in the ARF in Scotland study, for instance, was acidosis.6 There is currently no evidence base that using RRT for extended indications in critically-ill patients results in improved outcomes.
Some caution must be exercised around extrapolating these incidences, since the time frame over which data was collected was short, the number of patients small and the confidence intervals wide; in addition, since this study took place in the summer, there may also be seasonal variations in incidence of ARF that have not been captured. Our data are also from a geographical area with its own particular socio-economic and ethnic mix, as well systems of health-care provision. Unlike in previous studies of ARF, our primary goal was to capture details of severe single-organ acute renal failure referred to critical care services. It is widely accepted that there are pressures created by such patients (from general ward level needing to transfer the patient ‘up’ the care network, and from intensive care level where the patient with single organ failure may be ‘bed-blocking’), but this is an area in which it is difficult to get good quality data. In this study, 46% of single-organ ARF patients had some of their care in an ICU setting, despite their requirements being a level 2 setting (or arguably in some instances a ‘renal’ bed rather than a renal HDU bed would have been adequate). The overall ICU bed occupancy was 59 days, greater than full-time occupation of one ICU bed for the duration of the study. Although clearly no cause and effect can be assumed, during the 6-week study period, 12 patients were transferred out of the Greater Manchester critical care network due to lack of ICU beds (Data from the Intensive Care Bed Information Service).
Anecdotally, ‘lack of beds’ is a frequent reason given for misplacement of a patient, but is a term which belies the complex problems underlying the phenomenon. In the case of acute renal facilities, beds can effectively be ‘blocked’ by lack of maintenance out-patient haemodialysis slots, so that patients who fail to recover renal function, or patients with ESRD admitted as acute uraemic emergencies, cannot be discharged to the out-patient programme in a timely fashion. This in turn leads to newly referred patients staying inappropriately on a general ward awaiting transfer, or patients being admitted to ICUs because of lack of haemodialysis capacity in tertiary acute renal facilities. Capacity within maintenance haemodialysis programmes is therefore crucial to effective functioning of both level 2 and level 3 critical care. The 2002 European Renal Registry report demonstrates the much lower prevalence of haemodialysis patients in the UK, with unadjusted figures of 222 pmp on haemodialysis in England, compared with (for example) 634 pmp in Spain or 656 pmp in Germany.14 A study involving all renal units in the UK in 2002 found that most units appeared to be operating at maximum or near-maximum capacity.15
Independent external assessment of our case summaries identified that in almost half the cases there was an unacceptable delay in transfer of the patients—either initially to a critical care bed, or secondarily then in transfer from ICU on to renal services. In a quarter of cases, delays in specialist renal assessment (because of delay/failure to transfer) were judged to have led to a potentially adverse effect on patient outcomes, the most serious being cardiac arrests. It is noteworthy that these delays took place after referral to renal services. Any potential impact of failing to identify patients as requiring referral earlier in their clinical course was beyond the scope of this study. The potentially adverse effects identified by our assessors do not take into account the consequences of a lack of specific renal skills in the multi-professional team caring for the patient (such as dietetics, pharmacy and nursing expertise) or possible psychological stresses on patients and their families of waiting for transfer from ward level to ‘kidney specialists’ for definitive care, sometimes whilst the patients’ condition appears to be deteriorating. We acknowledge there are inherent issues of reliability and validity of assessors making judgements about quality of care. Sub-optimal ward care of more severely unwell patients has been noted to occur in several studies, however, leading to unnecessary ICU admission and higher mortality rates.10,16–18 Data specifically pertaining to acute kidney disease are lacking, but for patients with chronic kidney disease who are referred late for specialist renal assessment, they are less likely to receive interventions that could alter the progression of their kidney disease or reduce its associated co-morbidity, have a worse clinical state at the start of RRT, longer hospitalization and poorer survival.19
Angus and Black, examining ways to improve care and safety of the critically ill, noted that, ‘Even when motivated, we cannot manage what we do not measure’, and called for institutional and health care systems approaches to improve outcomes.20 Although comprehensive datasets are available for intensive care settings, prospective data examining incidence, causes and outcomes of ARF in other care areas are lacking. Developing standardized datasets and systems for their collection outside the ICU setting would be challenging, but a necessary next step forward.
This study demonstrates a continuing rise in the incidence of acute renal failure, with 452 pmp/year requiring renal replacement therapy for ARF in Greater Manchester. It highlights serious problems in the appropriate use of expensive and limited medical resources in the critical care area, and providing safe and effective treatment of patients with ARF.
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Acknowledgments |
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We are very grateful for the support of medical, nursing, IT and admin colleagues in the Renal and Critical Care Networks in Greater Manchester without whose help this study would not have been possible.
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References |
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