Salt and Fluid Restriction Is Effective in Patients With Chronic Heart Failure

Henriette Philipson; Inger Ekman; Heléne B. Forslund; Karl Swedberg; Maria Schaufelberger

Disclosures

Eur J Heart Fail. 2013;15(11):1304-1310. 

In This Article

Methods

Study Design

In a 12-week prospective, randomized, multicentre intervention trial, patients were allocated to either a individualized salt and fluid restriction (intervention group) or information given by the nurse-led heart failure clinics, e.g. be aware not to drink too much and use salt with caution (control group).[1] The patients were stratified according to age (≤70 years) and dose of diuretics (≤80 mg of furosemide or equipotent doses of other diuretics). A separate randomization list was produced for each stratifying variable using block randomization in groups of four. The study was approved by the Regional Ethical Review Board of the University of Gothenburg.

Patients with a history of CHF, in NYHA class II–IV, from the Sahlgrenska University Hospital, Gothenburg and Södra Älvsborg, Hospital Borås were prospectively enrolled. Inclusion criteria were: stable condition; documented LV dysfunction (EF ≤40%, or >40% and a history of hospitalization for heart failure); a history of signs of fluid retention (on chest X-ray or peripheral oedema); on maximum tolerated doses of ACE inhibitors/ARBs and beta-blockers with no change in medication for at least 2 weeks prior to enrolment; and ≥80 mg of furosemide or equipotent doses of others diuretics for patients in NYHA II or ≥40 mg of furosemide for patients in NYHA III–IV. Exclusion criteria were: concomitant liver or renal disorder (serum creatinine >250 μmol/L) causing fluid retention; present fluid retention requiring adjustment of diuretics; other diseases limiting the patients' physical capacity; and lack of ability to follow instructions, e.g. patients with dementia and language problems. The study physician determined the lack of ability to follow instructions.

Outcome on the primary composite endpoint after 12 weeks was defined as follows.

  1. Deterioration. Patients were considered to have deteriorated if they met any of the following criteria: (a) deterioration at least one NYHA class; (b) hospitalization for heart failure; (c) weight gain ≥2 kg; (d) increased leg oedema (≥1 point on a 4-point scale); (e) increased thirst ( ≥2 points on a 10-point scale); or (f) reduced QoL (≥2 points on a 6-point scale). Hence, even if a patient improved in all other criteria, patient was classified as 'deterioration' if only one of the criteria had deteriorated.

  2. Improvement. Patients were considered to have improved if none of the above criteria were met and if they met at least one of the following criteria: (a) improved at least one NYHA class; (b) weight loss ≥2 kg; (c) decreased leg oedema (≥1 point on a 4-point scale); (d) improved QoL ( ≥2 points on a 6-point scale); or (e) decreased dose of diuretics (≥40 mg of furosemide).

  3. Unchanged. Patients were considered unchanged if they did not meet any of the criteria in either (i) or (ii) above.

The physicians taking part in the study (n = 8) all discussed very carefully at the beginning of the study how to assess the different variables so that a consensus was reached. At baseline, the patient's medical history was recorded and a physical examination was performed. Blood samples for analysis of serum sodium, serum potassium, serum creatinine, serum NT-proBNP. and serum haemoglobin were collected from each patient. Height and weight were measured. Thereafter the patients were instructed to collect a 24 h urine sample on three consecutive days. To verify the completeness of the urine collection, the patients were given para-aminobenzoic acid (PABA; 80 mg t.i.d.) on the first day of urine collection.[13,14] Urine collections containing 75–100% of the PABA consumed were classified as complete. Collections containing 50–75% of the PABA were considered incomplete and in such cases urine sodium was estimated by means of linear regression analysis.[15] Urinary collections with <50% of the PABA in any of the samples were excluded from the analysis.[14,15] After urine collection, the patients completed a validated QoL instrument[16] and rated fatigue, thirst, and appetite on 10 cm visual analogue scales (VAS).[17] Diet was registered using the semi-quantitative Food Frequency Questionnaire (FFQ).[18] Meal pattern information was gathered in an food anamnesis and the 24 h dietary recall procedure was used as the instrument for dietary counselling.[19]

Subsequently, patients were randomized into either the intervention group or the control group. The physicians were blinded to the randomization. The patients, family members, study nurses, and dieticians were asked not to reveal the patient's randomization status to the physicians. Baseline investigations were repeated after 12 weeks.

Intervention Group

The dietary recommendations were individualized, taking into consideration the patient's cultural, economic, and social habits, and were based on the results of the 24 h dietary recall and the semi-quantitative FFQ.[18] A registered dietician (RD) or a specially trained registered nurse (RN), coached by a dietician and in continuous dialogue with the dietician about nutritional problems, discussed and gave advice to the patients about how to reduce sodium intake to 2–3 g/day (corresponding to 5 g of salt per day) and to limit fluid intake to a maximum of 1.5 L/day. Patients reported fluid intake as the volume of their own glasses and cups of fluid consumed and there were no restrictions on water content in foods, except for dinner soups and liquid desserts. The importance of maintaining a constant energy level was emphasized. For detailed information, see the pilot study.[12]

Follow-ups were performed at a visit with the study nurse after 4 weeks and by telephone, without prior announcement, by the RD or the specially trained RN every 2–3 weeks. A 24 h dietary recall was used at each contact to follow the patients' adherence to the dietary advice[20] and as a basis for giving additional guidance on how to limit the salt and fluid intake. Patients were encouraged to ask questions about their food choices, cooking, and how to cope with fluid and salt restrictions.

Control Group

The RD or the specially trained RN provided the patients with information given by the nurse-led heart failure clinics, e.g. 'be aware not to drink too much and use salt with caution'.

One-year Follow-up

Patients were contacted by telephone after 10–12 months by a dietician without prior announcement. A 24 h dietary recall interview was performed and patients completed a questionnaire about adherence to the salt and fluid dietary advice given during the study period.

Statistical Analysis

To show a 20% difference in favour of the intervention with 80% power at the 5% significance level, a power calculation generated a need for 97 patients in each group. All analyses were performed with the Predictive Analytics SoftWare (PASW version 18 for Windows, Chicago, IL, USA). Data are presented as mean ± standard deviation (SD) for continuous variables and were analysed according to intention to treat (ITT). All patients who were unchanged in terms of the composite endpoint were considered worse, since the intervention was aimed to show improvement. Comparisons between the groups were made using the two-tailed, independent sample t-test for continuous, normally distributed data, and Mann–Whitney U-test for skewed, continuous variables. Missing data were not imputed.

Pearson's χ2 was used for categorical variables. A two-tailed P < 0.05 was considered significant.

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