Hyponatraemia in cancer patients on an inpatientrehabilitation unit

M. NELSON, MD, ASSISTANT PROFESSOR, Frazier Rehab Institute, University of Louisville, Louisville, KY, J.L. PALMER,PHD, DIRECTOR OF PROGRAMS, American Statistical Association, Alexandria, VA, J. FU, MD, ASSISTANT PROFESSOR, Depart-ment of Palliative Care and Rehabilitation Medicine, The University of Texas M. D. Anderson Cancer Center,Houston, TX, J.L. WILLIAMS, MPH, CCRP, DATA MANAGER, Department of Palliative Care and Rehabilitation Medicine,The University of Texas M. D. Anderson Cancer Center, Houston, TX, R. YADAV, MD, ASSOCIATE PROFESSOR,Department of Palliative Care and Rehabilitation Medicine, The University of Texas M. D. Anderson CancerCenter, Houston, TX, & Y. GUO, MD, ASSOCIATE PROFESSOR, Department of Palliative Care and Rehabilitation

Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA

NELSON M., PALMER J.L., FU J., WILLIAMS J.L., YADAV R. & GUO Y. (2014) European Journal of CancerCare 23, 363–369Hyponatraemia in cancer patients on an inpatient rehabilitation unit

This study identifies the incidence of hyponatraemia in cancer patients on an inpatient rehabilitation unit andexamines the association between admission hyponatraemia and rehabilitation length of stay (LOS), functionaloutcome, and survival. After institutional review committee’s approval, we retrospectively reviewed medicalrecords of 295 consecutive patients who were admitted to this inpatient cancer rehabilitation unit between 27January 2009 through 31 July 2010 in a tertiary cancer centre. The incidence of hyponatraemia in cancerpatients admitted to our inpatient rehabilitation unit was 41.4%. Median rehabilitation LOS for patients withmild (Na 130–134 mEq/L) and moderate–severe (Na < 130 mEq/L) hyponatraemia was 11 and 15 days, respec-tively, which was significantly longer than patients with eunatraemia (10 days; P = 0.03). Functional Inde-pendence Measure gain for ambulation and transfers during inpatient rehabilitation stay was not significantlydifferent between three different patient groups. We concluded that large portion of patients who require acuteinpatient rehabilitation presented with hyponatraemia, which is associated with prolonged rehabilitation LOS.Whether aggressive management of hyponatraemia will shorten rehabilitation stay needs further study.

Keywords: hyponatraemia, cancer, rehabilitation, length of stay, survival, physical function.

INTRODUCTION

Hyponatraemia is the most frequent electrolyte abnormal-ity in hospitalised patients. It occurs in a range of diagno-ses, including pneumonia, septicaemia, heart failure,

diabetes mellitus, acute renal failure, cancer, and others.Hyponatraemia can also be iatrogenic from diuretics, selec-tive serotonin re-uptake inhibitors (SSRIs), and many othercommonly used medications (Berghmans 1996). Manystudies have documented the incidence of hyponatraemiain non-cancer patients at hospital admission, and the rangeis wide (3.7–42%). Doshi et al. (2012) documented a 47%incidence of hyponatraemia (sodium level <135 mEq/L) ina large prospective study of 3357 hospitalised cancerpatients. Growing evidence suggests that hyponatraemia,in both cancer and non-cancer patients, is associatedwith prolonged hospitalisation and increased mortalityrate. Hyponatraemia, even when mild and seemingly

Correspondence address: Ying Guo, Department of Palliative Care andRehabilitation Medicine – Unit 1414, The University of Texas M. D.Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030,USA (e-mail: yguo@mdanderson.org).We certify that there is no conflict of interest with any financial organi-sation regarding the material discussed in the manuscript.

Accepted 6 September 2013DOI: 10.1111/ecc.12140

European Journal of Cancer Care, 2014, 23, 363–369

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Original article

© 2013 John Wiley & Sons Ltd

asymptomatic, has also been recently associated withgait and attention impairments, increased falls, increasedrisk of fractures, and osteoporosis (Renneboog et al. 2006;Gankam Kengne et al. 2008; Kinsella et al. 2010; Verbaliset al. 2010; Hoorn et al. 2011; Tolouian et al. 2012).

For cancer patients who encounter acute loss of function,rehabilitation programmes (Huang & Sliwa 2011) and espe-cially inpatient rehabilitation programmes (Marciniaket al. 1996; Cole et al. 2000; Garrard et al. 2004; Tay et al.2009; Guo et al. 2011) have been shown to improvepatients’ functional status and quality of life. Coexistinghyponatraemia could potentially exacerbate patients’ gaitabnormality, impair their attention, and increase their riskfor fall and fracture, therefore hindering the functional gainof patients during inpatient rehabilitation.

The purposes of this study were to determine the inci-dence of hyponatraemia among patients admitted to aninpatient cancer rehabilitation unit and to assess whetherhyponatraemia is associated with rehabilitation length ofstay (LOS), functional outcomes, and survival duration.This is the first study to assess this question in cancerpatients undergoing inpatient rehabilitation.

METHODS

Study population

The Institutional Review Board at MD Anderson CancerCenter (MDACC) approved this collection of data. Retro-spective data on 300 consecutive patients admitted tothe inpatient rehabilitation unit during the timeframe of27 January 2009 through 31 July 2010 were collectedfrom ClinicStation, the hospital’s electronic database.Five patients were excluded – two of the patients were <18years of age, one patient had hypernatraemia at admissionto rehabilitation (Na 148 mEq/L), and two other patientshad non-neurologic benign pathology (lipoma, benigncecal polyps). The remaining 295 cancer patients werefirst admitted to MDACC with various acute medical/surgical problems and later transferred to the acute inpa-tient rehabilitation unit.

Data collection

Demographic data obtained on each patient includeddate of birth, age at admission to rehabilitation unit, eth-nicity, and gender. Cancer diagnoses were documented andgrouped into either haematological or solid tumour diag-noses for statistical analysis. Known co-morbidities andcancer treatment history which could potentially affectsodium levels were recorded, including metastatic disease

in brain or lungs, prior or concurrent cancer treatment,congestive heart failure, liver dysfunction, renal dysfunc-tion, ascites, and diabetes mellitus requiring medication.Liver dysfunction was defined as a total bilirubin level>2 mg/dL during hospitalisation or 1 month prior to admis-sion, as several patients did not have a level drawn duringtheir hospitalisation. Renal dysfunction was definedas a creatinine level >2 mg/dL during admission andall patients had this laboratory value evaluated duringhospitalisation. Co-morbidities and medical diagnoseswere recorded as present if there was sufficient medicalchart data, including laboratory data, radiological imagingand reports, pathology reports, and physician transcribeddocuments, supporting the diagnosis. Survival times werecalculated from date of rehabilitation admission till death,and documented in weeks. Survival is censored at the dateof last contact in the hospital records at the time of datacollection.

A normal serum sodium concentration at current insti-tution is defined as 135–147 mEq/L. Hyponatraemia, forthis study, is thus defined as Na < 135 mEq/L. We furthercategorised our patients into three groups based upon theirserum sodium concentration at admission to the rehabili-tation unit: moderate–severe hyponatraemia (<130 mEq/L), mild hyponatraemia (130–134 mEq/L), and eunatraemia(135–147 mEq/L). These categories of hyponatraemia werebased upon prior studies using these definitions of mild andmoderate–severe hyponatraemia (Tierney et al. 1986;Chua et al. 2007; Kinsella et al. 2010; Doshi et al. 2012).

Length of stay on the rehabilitation unit was in days fromrehabilitation admission date to discharge date. Functionaloutcomes included Functional Independence Measure(FIM) scores of two criteria: ambulation and transfers (rangefrom 7 as independent to 1 as totally dependent on eachtask). The FIM scores used for this study were obtained atadmission and discharge from the rehabilitation unit. TheFIM ‘ambulation score’ was defined as gait assessment. Allother FIM data were not recorded due to the high rate ofmissing data for other items. FIM change was calculated,which was the sum of admission ambulation and transferscores subtracted from the sum of discharge ambulationand transfer scores. The FIM change was then comparedbetween patients based upon their rehabilitation admis-sion serum sodium level.

Data analysis

The frequency and proportions of the three sodium catego-ries [moderate–severe hyponatraemia (<130 mEq/L), mildhyponatraemia (130–134 mEq/L), and eunatraemia (135–147 mEq/L)] were calculated. We compared differences

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between the three sodium categories using Kruskal–Wallistests, chi-square tests, and Fisher’s Exact tests accordingto sample type and distribution. The Kruskal–Wallis testwas used to compare age, rehabilitation LOS and functionalbetween the groups. Chi-squared tests were used tocompare frequencies of the following variables in the threegroups: gender, ethnicity, diagnosis, each element of priorand current treatment, co-morbid diagnoses, and brain andlung metastases. A Fisher’s Exact test was used to comparepresence of adrenal insufficiency among the three groups.One-way anova test was used to compare FIM scorebetween the 3 patient groups. Non-parametric estimates ofthe survival distribution functions for each serum sodiumcategory were calculated using the method of Kaplan–Meier. The Log-Rank test was used to test for equalityover strata. Statistical analyses were performed usingSAS version 9.2 (SAS Institute, SAS Campus Drive, Cary,NC, USA). A P value <0.05 was considered statisticallysignificant.

RESULTS

Demographic data and cancer diagnoses present in ourpatient population are listed in Table 1.

Table 2 compared the characteristics and rehabilitationLOS in three patient groups. Hyponatraemia (<135 mEq/L)was present in 41.4% of patients admitted to our inpatient

cancer rehabilitation unit. The majority of this percentagewas mild hyponatraemia (35.6% mild versus 5.8%moderate–severe hyponatraemia). All confounders, such asage, cancer diagnosis, co-morbidities were not significantlydifferent between the groups. Patients with mild andmoderate–severe hyponatraemia had median stays of 11and 15 days, respectively, significantly longer than 10 daysfor eunatraemic patients (P = 0.03).

The median FIM change, change of combined ambula-tion and transfer scores from admission to discharge, wascalculated for each sodium category. There was a 2.0median improvement for each group, regardless of theserum sodium level at admission to rehabilitation, andnot statistically significant (P = 0.64). Figure 1 demon-strated the mean FIM (ambulation and transfer combined)at rehabilitation admission and discharge in three patientgroups.

Overall survival were not significantly different amongthe three groups categorised by their admission serumsodium level (P = 0.67). The point estimates of the 25thpercentiles of survival times and their 95% confidencelevels (CIs) were 19.5 weeks (4, 43), 25 weeks (15, 35), and30 weeks (18, 41) for the moderate–severe hyponatraemia,mild hyponatraemia and eunatraemia groups respectively(Fig. 2). Point estimates of the median (50th percentile)survival times of moderate–severe hyponatraemia, mildhyponatraemia and eunatraemia groups were 50 weeks,85 weeks and 90 weeks respectively. However, due tofrequent censoring of the data, we are not able to estimatethe upper 95% CIs for medians in any of the threegroups.

DISCUSSION

Hyponatraemia is a frequent electrolyte abnormality inmany hospitalised patients with non-cancer and cancerdiagnoses. A recent published study (Doshi et al. 2012)from the same institution as the current study showed 47%of hospitalised cancer patients have hyponatraemia(defined as Na < 135 mEq/L) at admission, and this is quitedifferent from a prospective study of cancer patientsby Berghmans (3.7%) (Berghmans, 1996). However,Berghmans’ study (1996) defined hyponatraemia as Na <130 mEq/L. The present study was consistent with both,with 41.4% patients with sodium <135 mEq/L, and 5.8%patient with Na < 130 mEq/L. Based on our current knowl-edge, there is no known study looking at the incidence ofhyponatraemia specifically in the inpatient cancer reha-bilitation setting. We used the same criteria as Doshi et al.(2012) study to define hyponatraemia (Na < 135 mEq/L),and we found 41.4% of our patients admitted to our

Table 1. Patient demographic data (n = 295)

No. of patients (%)

Age 18–30 years 26 (8.8)31–50 years 84 (28.5)51–70 years 123 (41.7)>70 years 62 (21.0)

Male 171 (58.0)Ethnicity Native American 1 (0.3)

Asian 9 (3.1)Black 20 (6.8)Hispanic 30 (10.2)White 224 (75.9)Unknown 11 (3.7)

Cancer type Brain and/or spine 63 (21.4)Breast 9 (3.1)Endocrine 2 (0.7)Gastrointestinal 31 (10.5)Genitourinary 12 (4.1)Gynaecological 1 (0.3)Head and neck 16 (5.4)Haematological 40 (13.6)Lung 18 (6.1)Melanoma 10 (3.4)Other 21 (7.1)Renal cell carcinoma 13 (4.4)Sarcoma 41 (13.9)>1 tumour type 18 (6.1)

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inpatient cancer rehabilitation unit present with hypona-traemia. This incidence is high, and there are variouspotential reasons for this in cancer patients, including sideeffects of some chemotherapeutic agents, certain cancerdiagnoses causing SIADH, cancer-related pain especiallywhen treated with morphine derivatives, hydration proto-cols, and malnutrition can all potentially exacerbateor cause hyponatraemia. Although the majority of thehyponatraemic patients in this study were in the ‘mild’category (Na 130–134 mEq/L), it did impact rehabilitationLOS significantly. Our patients also have a mean age of58 (range 18–87 years), and Hawkins (2003) documentedincreasing age (>30 years) is associated with hospital-associated sodium alterations. In this study, the mean ageof the three groups was not significantly different.

In addition to determining the incidence of hypona-traemia on our inpatient rehabilitation unit, our study’sgoals were to determine if hyponatraemia was associatedwith length of rehabilitation stay, FIM change, and mor-tality. Many studies have documented increased hospitallengths of stay in patients with hyponatraemia (Chuaet al. 2007; Gheorghiade et al. 2007; Zilberberg et al.

Table 2. Patient characteristics (n = 295) and rehabilitation LOS in three patients groups according to serum sodium level

Serum sodium (mEq/L) <130 (n = 17) 130–134 (n = 105) ≥135 (n = 173) P value

Median age [minimum–maximum] 68 [44–81] 61 [18–87] 60 [18–84] 0.08*Gender (%)

Male 14 (82) 64 (61) 93 (54) 0.06Ethnicity (%)

White 13 (76) 76 (72) 135 (78) 0.56Other 4 (24) 29 (28) 38 (22)

Tumour (%)Solid tumour 15 (88) 92 (88) 148 (86) 0.87Haematological 2 (12) 13 (12) 25 (14)

Known metastases (%)Brain 4 (24) 10 (10) 15 (9) 0.14Lung 3 (18) 13 (12) 30 (17) 0.53

Treatment (%)Prior chemotherapy 10 (59) 62 (59) 107 (62) 0.89Concurrent chemotherapy 0 13 (12) 19 (11) 0.31Prior radiation 7 (41) 43 (41) 73 (42) 0.98Concurrent radiation 5 (29) 12 (11) 17 (10) 0.05Prior surgery 13 (76) 86 (82) 152 (88) 0.24

Known co-morbidities (%)CHF 0 7 (7) 10 (6) 0.76Liver dysfunction 0 8 (8) 12 (7) 0.83Renal dysfunction 2 (12) 6 (6) 12 (7) 0.65Ascites 1 (6) 10 (10) 12 (7) 0.70Diabetes mellitus 3 (18) 20 (19) 23 (13) 0.43Adrenal insufficiency 1 (6) 1 (1) 2 (1) 0.23†

Median rehabilitation LOS, in days (range) 15 (4–22) 11 (4–39) 10 (1–31) 0.03*‡

*Kruskal–Wallis tests were used.†Fisher’s Exact test was used. For the rest of the statistical analysis, Chi-squared tests were used.‡Significant result.CHF, congestive heart failure; LOS, length of stay; mEq/L, milliequivalents per litre.

Figure 1. Mean FIM combined scores (ambulation and transfer)for all patients at admission (patterned bar) and at discharge(black bar), based upon their admission serum sodium level. TheFIM changes were not significantly different between the groups(P value = 0.6423). FIM, Functional Independence Measure; Na,serum sodium. , Admission; ■, Discharge.

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2008; Kinsella et al. 2010; Wald et al. 2010; Doshi et al.2012). Doshi et al. (2012) study on cancer patients showedeunatraemic patients had a mean stay of 5.6 (± 5.0) dayscompared with hyponatraemic patients with mean staysof 9.9 (± 9.2), 13.0 (± 14.1), and 11.5 ± 12.6 days basedon whether they had mild (130–134 mEq/L), moderate(120–129 mEq/L), and severe hyponatraemia (<120 mEq/L)respectively. To our knowledge, no other study has inves-tigated rehabilitation unit LOS and serum sodium levels.Our study showed that patients with mild and moderate–severe hyponatraemia had median rehabilitation LOS of11 and 15 days, respectively, compared with 10 days forpatients admitted with eunatraemia.

This information is important because in many caseshyponatraemia is reversible. By realising that admissionhyponatraemia is associated with a longer rehabilitationLOS, physicians can treat hyponatraemia, which couldlead to shorter rehabilitation LOS and lower healthcarecosts; furthermore, normalising the sodium level mayhelp prevent future falls and increase survival duration.Anticipating the rehabilitation LOS not only is important

for the patient and the patient’s family or support groupto adequately prepare for the patient’s discharge but alsois important for the rehabilitation team to plan appropri-ate patient goals and to the hospital and insurance com-pany to estimate overall costs. Reports have stated thathyponatraemia directly increases medical costs, and a2006 article estimated hyponatraemia to cost $1.6 to$3.6 billion annually (Boscoe et al. 2006; Shea et al. 2008).Further studies are needed to determine if treatinghyponatraemia would help decrease hospital and rehabili-tation LOS as well as overall medical costs.

Functional Independence Measure (FIM) is utilised inmost inpatient rehabilitation settings in the United Statesto evaluate a patient’s functional change and hopefulimprovement. The functional change, for the purpose ofthis study, was calculated by subtracting the combinedadmission FIM ambulation and transfer scores from thecombined discharge FIM ambulation and transfer scores.At this time, there is no known study to the authorsdocumenting the association of hyponatraemia with FIMscores in the acute rehabilitation setting. Our study showsno significant difference in functional change (ambulationand transfers) for patients with hyponatraemia versuseunatraemia with median FIM gain of 2.0 points, regard-less of serum sodium level at admission to rehabilitation,though the time needed to achieve the same goal weresignificantly longer in patient with hyponatraemia.

This finding is of particular interest because manyrecent studies have shown that hyponatraemia is associ-ated with gait and attention impairments, increased falls,increased risk of fractures, and osteoporosis (Rennebooget al. 2006; Gankam Kengne et al. 2008; Kinsella et al.2010; Hoorn et al. 2011; Tolouian et al. 2012). InRenneboog et al. (2006) case-control matched study ofhospitalised patients with hyponatraemia (defined as asodium level <132 mEq/L), hyponatraemic patients fellfour times more frequently than their eunatraemic con-trols, regardless of their level of hyponatraemia (sodiumlevel, 115–132 mEq/L). They also compared their resultswith patients with moderate alcohol intake and foundthat hyponatraemic patients demonstrated more attentiondeficits (Renneboog et al. 2006). This study used a stricterdefinition of hyponatraemia than did ours, and Rennebooget al. did not assess patients’ response with participationin a rehabilitation programme. Future studies are neededto determine the fall frequency and the improvement inbalance after rehabilitation interventions for patients withhyponatraemia and eunatraemia. According to our study’sdata, however, patients with lower sodium levels achievedsimilar functional gain with ambulation and transfers aseunatraemic patients after inpatient rehabilitation.

Figure 2. Kaplan–Meier overall survival (in weeks) curve forcancer patients based on serum sodium level at admission torehabilitation (P value = 0.6691). Patients with Na < 130 mEq/Lhave median survival time at 50 weeks (dotted line). Patientswith Na 130–134 mEq/L have median survival time at 85 weeks(grey line). Patients with Na ≥135 mEq/L have median survivaltime at 89 weeks (solid line).Abbreviations: Na, sodium; mEq/L, milliequivalents per litre.

, Na < 130; , Na 130–134; , Na ≥ 135; , Na < 130censored; , Na 130–134 censored; , Na ≥ 135 censored.

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Our study shows patients with hyponatraemia uponadmission to an inpatient rehabilitation unit have anincreased rehabilitation LOS, yet they achieve comparablefunctional gain with ambulation and transfers. Figure 1shows the mean admission and discharge FIM scores forhyponatraemic and eunatraemic patients, and the scoresare fairly equivalent in each serum sodium group with nosignificant difference of the median functional change(2.0 points, P = 0.64). It is possible our patients with lowerserum sodium levels had more subtle gait and attentionimpairments with increased fall risk, as seen in otherstudies, yet the abbreviated FIM scores used in this studywere not able to fully demonstrate this. Subtle deficits notdetectable by FIM score could be the cause of longer reha-bilitation stays for hyponatraemic patients in order forthem to attain a safe discharge functional status. Yet itremains difficult to conclude a direct causal relationship.As Fakhouri et al. (2012) in an editorial and many otherauthors have mentioned, is it the hyponatraemia causingthese effects, or is it the severity of the original diagnoses(such as cancer) and their required inpatient-setting treat-ments causing these findings? This is an ongoing debate,and other studies are needed to evaluate this.

Hyponatraemia has also been associated with increasedin-hospital and post-discharge mortality, even up to 5years after discharge, according to one study (Tierneyet al. 1986; Gheorghiade et al. 2007; Zilberberg et al.2008; Waikar et al. 2009; Elsayem et al. 2010; Wald et al.2010; Doshi et al. 2012). Hyponatraemia can be mild(Waikar et al. 2009), present at admission to the hospital,and/or acquired during hospitalisation (Wald et al. 2010)and still be associated with increased mortality. Althoughour study did not show a significant difference in survivalduration owing to a patient’s serum sodium level at timeof admission to the rehabilitation unit, the trend forsurvival is consistent with previous reports. Our studyshowed that survival duration for the 25th percentileof each group and the 95% confidence intervals forpatients in the moderate–severe hyponatraemia, mildhyponatraemia, and eunatraemia groups were 19.5 weeks(4, 43), 25 weeks (15, 35), and 30 weeks (18, 41) respec-tively (Fig. 2). Survival data for patients with a sodiumlevel <130 mEq/L appear worse; however, owing to thesmall sample in this category (n = 17), not significantlydiffer from that of the other patient groups. Also, our datacollection occurred 20 months after the date of the lastpatient’s admission, and this timeframe may be too trun-cated to observe a significant difference in survival dura-tion among the three serum sodium groups. Other studieshave demonstrated an improvement in survival durationin cancer and non-cancer patients if the hyponatraemia

improves or resolves during hospitalisation (Waikar et al.2009; Doshi et al. 2012). In our study, upon discharge fromthe inpatient rehabilitation unit, only 29% of the patientsstill had hyponatraemia compared with the 41.4% ofpatients with hyponatraemia at admission, and it is pos-sible this improvement in hyponatraemia affectedpatients’ survival curves. Physiatrists should be awarethat evaluating and treating hyponatraemia of any sever-ity is likely to benefit a patient’s future medical course.

Historically, hyponatraemia especially when ‘mild’was thought to be fairly benign, unless the sodium levelchanged drastically and acutely causing demonstrable sideeffects of the central nervous system. Recent literaturesuggests otherwise with hyponatraemia being associatedwith several adverse findings, such as gait and atten-tion impairments, falls, risk of fractures, osteoporosis,increased hospital lengths of stay, healthcare cost andmortality (Tierney et al. 1986; Renneboog et al. 2006;Gankam Kengne et al. 2008; Callahan et al. 2009; Waikaret al. 2009; Kinsella et al. 2010; Wald et al. 2010; Hoornet al. 2011; Doshi et al. 2012; Tolouian et al. 2012).Our study population demonstrates a high incidence ofmild hyponatraemia upon admission to our rehabilitationunit, and it is associated with a small but significantlyincreased rehabilitation LOS. Whether hyponatraemia is adirect cause of these findings or just a sign of the under-lying disease severity remains unclear. However, it isimportant for physiatrists to be aware of these associa-tions, as it may affect their evaluation and treatment ofhyponatraemia, discharge planning for each patient, andeducation for patients and their families, and the impacton the healthcare cost. More prospective studies in reha-bilitation settings are needed to determine if correctinghyponatraemia will help reduce mortality.

Study limitations

This study was limited by its retrospective design.Aetiologies of hyponatraemia were not determined in thisstudy. Another important limitation of our study is thatwe only measured serum sodium concentration at thetime of rehabilitation admission and therefore do notknow whether hyponatraemia was transient or chronic.However, the fact that a single hyponatraemic valuerevealed an association with rehabilitation LOS suggeststhat the association is quite strong. Further studies areneeded to confirm our findings. Specific FIM scores(ambulation and one type of transfer) were evaluated, andother FIM scores were excluded owing to missing func-tional data in our patient charts. FIM scores have inherentceiling and floor effects with broad definitions for each

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FIM score; therefore, subtle ambulation and transferchanges might not have been demonstrated in ourpatients’ scores.

CONCLUSION

To our knowledge, this is the first study to demonstratethe high incidence of hyponatraemia in cancer patients

admitted to an inpatient rehabilitation unit and thesignificant association between hyponatraemia andincreased rehabilitation LOS. The functional gain withambulation and transfer capabilities fortunately does notappear to be affected by a patient’s serum sodium level atadmission to the inpatient rehabilitation unit.

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