Nutritional Assessment of Continuous Ambulatory Peritoneal Dialysis Patients: An International Study

ORIGINAL INVESTIGATIONS

Nutritional Assessment of Continuous Ambulatory Peritoneal Dialysis Patients: An International Study Gerald A. Young, PhD, FRSC, Joel D. Kopple, MD, MPH, Bengt Lindholm, MD, PhD, Edward F. Vonesh, PhD, Amedeo De Vecchi, MD, Antonio Scalamogna, MD, Claudia Castel nova, MD, Dimitrios G. Oreopoulos, MD, PhD, FRCp, G. Harvey Anderson, PhD, Jonas Bergstrom, MD, PhD, Janet DiChiro, RD, MS, Dominic Gentile, MD, Allen Nissenson, MD, Lakhi Sakhrani, MD, Aleck M. Brownjohn, FRCp, Karl D. Nolph, MD, Barbara F. Prowant, RN, MSN, Corrine E. Algrim, RN, BSN, Leo Martis, PhD, and Kenneth D. Serkes, MD • We examined the nutritional status of 224 patients from six centers in Europe and North America to assess the incidence of protein-energy malnutrition. A "subjective nutritional assessment" was made, using 21 variables derived from history and clinical examination, or anthropometry and biochemistry. Eighteen patients (80/0) were severely malnourished, 73 (32.6%) were mildly to moderately malnourished, and 133 (59.4%) did not show evidence for malnutrition. There was a higher incidence of mild to moderate malnutrition in diabetics than in nondiabetics. A statistical analysis identified 12 variables, seven objective and five subjective, that correlated with subjective nutritional assessment. Actual intercenter differences for the incidence of malnutrition were related to patient age, nutritional status at the commencement of continuous ambulatory peritoneal dialysis (CAPO), the length of time on CAPO, and residual renal function. Variables that were most frequently correlated with subjective nutritional assessment and with one another included plasma albumin, mid-arm muscle circumference (MAlv....), weight loss, and the clinical judgement of muscle wasting and loss of subcutaneous fat. Loss of residual renal function correlated with muscle wasting and months on CAPO. Our data identified differences between the two sexes. In women there was a trend for more anorexia, greater weight loss from muscle wasting, and a larger decrease in albumin, whereas in men there was a more gradual decrease in nutritional status. Loss of residual renal function contributed to anorexia and symptoms of severe malnutrition. © 1991 by the National Kidney Foundation, Inc. INDEX WORDS: Continuous ambulatory peritoneal dialysis; nutritional status; protein-energy malnutrition.

N

UTRITIONAL assessment is important in the detection of protein-energy malnutrition, the evaluation of dietary requirements and the development of alternative nutritional therapies. Protein-energy malnutrition occurs in nondialyzed I and dialyzed patients, particularly those undergoing hemodialysis. I-4 During continuous ambulatory peritoneal dialysis (CAPD), the loss of proteins and amino acids into dialysis fluid and peritonitis may increase the likelihood of nutriFrom the General Infirmary at Leeds, Leeds, England; Harbor-UCLA Medical Center and the University of California Los Angeles, Los Angeles, CA; Huddinge University Hospital, Karolinska Institute, Huddinge, Sweden; Baxter Healthcare Corporation, Round Lake, IL; Division of Nephrology and Dialysis, Ospedale Maggiore, Milan, Italy; Toronto Western Hospital and University of Toronto, Toronto, Canada; and the University of Missouri, Columbia, MO. Address reprint requests to Corrine E. Algrim, KN, BSN, Baxter Healthcare Corporation, Roulld Lake, IL 60073. © 1991 by the National Kidney Foundation, Inc. 0272-6386/91/1704-0021$3.00/0 462

tional impairment when there is inadequate protein intake, 5 and such patients may be in negative nitrogen balance with long-term loss of total body nitrogen. 6 .7 Superimposed catabolic illnesses and probably chemical and hormonal abnormalities of renal failure contribute to protein-energy malnutrition. Decreases in some amino acids and proteins in both plasma and muscle may indicate subclinical malnutrition,5 and progressive nitrogen depletion may contribute to a decrease in plasma albumin. 8.9 Frank losses of muscle, fat, and body weight may occur. These clinical features have been assigned ordinal scores by "subjective global assessment"IO and used in an earlier CAPD study. II Most previous studies of nutritional status in CAPD patients have been limited in numbers of patients or in the variety of variables measured, and some used highly specialized techniques that are not widely available, eg, neutron activation for measuring total body nitrogen. 6 The present investigation was designed to (1) assess the protein-

American Journal of Kidney Diseases, Vol XVII, No 4 (April), 1991: pp 462-471

463

NUTRITIONAL ASSESSMENT IN CAPO

energy status of CAPD patients in a more comprehensive and definitive manner by using a wide range of variables, based on history, clinical examination, blood chemistry, and anthropometry, and (2) analyze possible relationships between subjective assessments and objective measurements of nutritional status. The assessment was performed in a cross-sectional study involving 224 patients from six centers in Europe and North America.

pital admission) (Table 2). The probability exists that exclusion for some medical reasons, particularly peritonitis, which occurred in 15 patients, and death, which occurred in eight patients, may have inadvertently excluded a few individuals with mild to moderate or severe malnutrition. However, exclusions for nonmedical reasons were less likely to bias the observed incidence of malnutrition.

Methods Each patient attended their center in a fasting state (8 to 14 hours postprandial) with urine and expended dialysate that had been collected over the preceding 24 hours. A blood sample was taken before the morning exchange. A small number of patients were allowed a light, nonfat breakfast either for medical reasons or because they had long distances to travel; but in each case at least 2 hours elapsed before blood was collected. No medication was given in the morning of the investigation, except to those patients where insulin was essential. A detailed data form was completed for each patient by a clinical investigator, summarizing medical history, current medical state, anthropometry, and biochemical measurements. The cross-sectional evaluation of each patient was based on 21 variables that were derived from the above information. These variables included the following six subjective measurements: the patients' history of weight loss and incidence of anorexia and vomiting, and the physicians' estimate of muscle wasting, edema, and loss of subcutaneous fat. All these variables were graded as 1 = severe, 3 = moderate, 5 = none. Thus, the grading used for a patient's weight loss, based on previous history, would be increased if recent stabilization or weight gain occurred. Anorexia and vomiting would be given the lowest score when these symptoms were severe and persistent. Estimates of muscle wasting, edema, and loss of subcutaneous fat were not pre-

PATIENTS AND METHODS

Patients A total of 224 patients, 132 males and 92 females, ranging in age from 14 to 87 years, were selected from six centers in Europe and North America to participate in this study, as shown in Tables I and 2. All patients had given informed consent, had been maintained on CAPO for more than 3 months, remained free from peritonitis for at least I month before the study, were compliant, and lived within traveling distance of the center. Thirty-two patients had to be excluded on the day of assessment, because 10 had been admitted to hospital for surgery (eg, nephrectomy, hernia repair), 13 had transferred to other forms of treatment (eg, hemodialysis), one was sick, and eight died. As a consequence of these criteria and exclusions, the 224 patients selected represented two thirds of the total CAPO population of the six centers (337). The 113 patients not included consisted of 66 excluded for nonmedical reasons (refusal, noncompliance, < 3 months' treatment, could not be reached, distance from center) and 47 for medical reasons (peritonitis, sickness, death, transfer to other treatment, or hos-

Table 1.

Summary of Primary Renal Disease and Clinical Characteristics in 224 Patients

Primary renal disease Glomerulonephritis Polycystic kidney disease Hypertensive nephrosclerosis Diabetes mellitus Pyelonephritis/interstitial nephritis Other disease Patient characteristics Age (yr) Months on CAPO Height (cm) Weight (kg) Plasma urea (mmol/L) (nitrogen mg/dL) Plasma creatinine (/lmol/L) (mg/dL) RRF (mLlmin) Peritonitis (episodes/yr)

Males (N = 132)

Females (N = 92)

Total (N = 224)

43 (19%) 11 (5%) 17 (8%) 24 (11%) 14 (6%) 23 (10%)

25 (11%) 7 (3%) 10 (4%) 11 (5%) 13 (6%) 26 (12%)

68 (30%) 18 (8%) 27 (12%) 35 (16%) 27 (12%) 49 (22%)

N

Mean

132 132 132 132 132

55.63 30.30 169.49 71.75 22.77 (63.77 1,000 (11.32 1.64 0.37

132 123 132

SD 14.56 23.14 10.36 12.48 5.67 15.88) 294 3.33) 2.33 0.49

N

Mean

92 92 92 92 92

50.08 34.97 160.96 59.90 21.60 (60.50 906 (10.25 0.82 0.44

92 89 92

SD 16.20t 30.96 7.14:1: 11.62:1: 6.77 18.96) 262t 2.96t) 1.27:j: 0.63

Abbreviation: RRF, residual renal function ([creatinine + urea clearance]/2). Mean values significantly different from males: * P < 0.05, tP < 0.01, :l:P < 0.001.

N

Mean

224 224 224 224 224

53.35 32.22 165.99 66.88 22.29 (62.43 962 (10.88 1.30 0.40

224 212 224

SD 15.46 26.67 10.18 13.44 6.14 17.21) 285 3.22) 1.99 0.55

YOUNG ET AL

464

Table 2.

Summary of Patients and Characteristics for Each Center Ospedale Maggiore

Toronto Western

Karolinska Instiutute

(N = 45) (N = 132) (N = 92) (N = 224)

6 (3%) 41 (18%) 22 (10%) 63 (28%)

14 (6%) 31 (14%) 22 (10%) 53 (24%)

10 (4%) 17 (8%) 19 (8%) 36 (16%)

Patients excluded Nonmedical reasons (N = 66) Peritonitis/sick/died (N = 24) Off CAPO/hospital (N = 23) Total (N = 113)

2 (1.8%) 0 (0%) 3(2.7%) 5 (4.4%)

Patients included Diabetes mellitus Males Females Total

Patient characteristics Age (yr) Months on CAPO Height (cm) Weight (kg) Plasma urea (mmoIlL) (nitrogen mg/dL) Plasma creatinine (pmoIlL) (mg/dL) RRF (mUmin) Peritonitis (episodes/yr)

SO

Mean (N = 62)

55.40 32.85 164.36 65.20 22.22 (62.23 942 (10.66 1.08 0.19

9 9 11 29

12.65 24.41 7.76 11.49 5.77 16.16) 199 2.25) 1.28 0.33

(8.0%) (8.0%) (9.7%) (25.7%)

SO

Mean (N = 52)

54.69 25.81 165.28 66.70 21.40 (59.94 874 (9.89 1.77 0.52

1 (0.9%) 5 (4.4%) 3 (2.7%) 9 (8.0%)

17.69 25.20 8.13 13.86 6.48 18.16) 281 3.18) 2.29 0.64

SO

Mean (N = 35)

53.31 35.66 168.22 66.75 21.09 (59.07 974 (11.02 0.65 0.55

13.80 29.63 9.66 12.99 5.44 15.24) 219 2.48) 1.29 0.58

NOTE. The percentages in brackets relate either to the total number included or excluded from the study.

cise, but more a subjective impression and were evaluated as described in detail by Detsky et ai. 10 The investigators made a subjective nutritional assessment of each patient as either (l) normal, (2) mildly to moderately malnourished, or (3) severely malnourished, based not only on the gradings of the subjective measurements as described by Detsky et al, 10 but also from the continuous variables, ie, anthropometrics and biochemical measurements. Consequently, a patient with some degree of malnutrition, on the basis of one or more low-scoring variables and/or low values for continuous variables would be classified in the mild to moderate group, whereas a patient with weight loss in the order of 10% or more with muscle wasting, loss of subcutaneous fat, low plasma albumin, etc, would be classified as severely malnourished. The techniques and limitations of both SUbjective and continuous measurements were discussed by the investigators before the start of the study to minimize variation between centers.

Anthropometric Measurements Weight (after drainage of dialysate) and biceps, triceps, subcapsular, and suprailiac skinfolds were used to calculate body fat. 12 Mid-arm muscle circumference (MAMC) was derived from arm circumference (AC) and triceps skinfold (TSF), where MAMC = AC - 1r(TSF). Percentage of pre-uremic body weight was calculated from values obtained from the medical records.

Biochemical Measurements Measurements were performed at the individual centers' laboratory on plasma or serum. Albumin was measured using bro-

mocresol green. Cholesterol, triglyceride, creatinine, urea nitrogen, and transferrin were measured by standard techniques. Urine and dialysate volumes were measured, and aliquots analyzed for total protein, creatinine, and urea. Residual renal function was defined as the mean of renal urea and creatinine clearances (mLlmin). Urea nitrogen appearance (UNA) was calculated from the total loss of urea nitrogen in dialysate and urine (mmoIld).

Statistical Methods Since the subjective nutritional assessments were made by the physicians in the six centers, it was recognized that either the subject assessment or the characteristics of the patient populations could differ among the centers. However, our primary concern was to investigate the overall relationship of each of the patient characteristics with the subjective nutritional assessment regardless of center. In order to achieve this, a univariate analysis of variance (ANOVA) was used to determine which of the 21 variables was significantly correlated with the subjective nutritional assessment in individual patients. These selected variables were examined using Students' t test for differences between the normal and malnourished groups. Since there are differences between men and women, the analysis was performed separately by sex. The individual variables were investigated further by formulating a matrix of partial correlations. Summary statistics are given in terms of means ± SD. Although some of the variables are ordinal rather than continuous, we found that they did not deviate enough from normality assumptions to warrant alternative analysis such as nonparametric ANOVA. Moreover, the usual ANOVA is relatively

465

NUTRITIONAL ASSESSMENT IN CAPO Table 2.

Summary of Patients and Characteristics for Each Center (Cont'd)

Patients included Oiabetes mellitus Males Females Total

(N = 45) (N = 132) (N = 92) (N = 224)

Patients excluded Nonmedical reasons (N = 66) Peritonitis/sick/died (N = 24) Off CAPO/hospital (N = 23) Total (N = 113) Patient characteristics Age (yr) Months on CAPO Height (cm) Weight (kg) Plasma urea (mmol/L) (nitrogen mg/dL) Plasma creatinine (I'mol/L) (mg/dL) RRF (mUmin) Peritonitis (episodes/yr)

7 20 9 29

4 (2%) 17 (8%) 16 (7%) 33 (15%)

46.03 33.79 166.51 65.20 25.93 (72.64 1,158 (13.09 0.66 0.44

(3%) (9%) (4%) (13%)

4 6 4 10

13 (11.5%) 6 (5.3%) 1 (0.9%) 20 (17.7%)

18 (15.9%) 2 (1.8%) 3 (2.7%) 23 (20.4%) Mean (N = 33)

University of Missouri

Leeds Infirmary

UCLA

SO

Mean (N = 29)

17.93 30.72 14.17 15.10 5.76 16.13) 296 3.35) 1.05 0.72

52.69 30.69 166.57 70.88 22.23 (62.26 947 (10.71 2.46 0.41

23 2 2 27

SO 16.54 20.85 12.43 13.29 6.86 19.21) 402 4.55) 2.97 0.48

(2%) (3%) (2%) (4%)

(20.4%) (1.8%) (1.8%) (23.9%)

Mean (N = 10)

58.40 52.10 168.50 72.89 19.81 (55.50 1,000 (11.31 1.31 0.41

SO

8.44 33.10 10.64 17.85 5.44 15.23) 238 2.69 3.37 0.40

NOTE. The percentages in brackets relate either to the total number included or excluded from the study.

robust to departures from normality. I3 Other variables, such as triglyceride, were transformed to achieve normality and thereby satisfy the assumptions required to perform the ANOVA.

RESULTS

Patient Data

A summary of primary renal disease, age, months on CAPD, height, weight, plasma urea nitrogen, plasma creatinine, residual renal function, and peritonitis, for males and females, is shown in Table 1. Fifty-nine percent of the patients were men. The distribution of primary causes of renal failure was essentially similar in the two sexes. Length of time on CAPD, plasma urea nitrogen, and the incidence of peritonitis were also similar in men and women, but the mean residual renal function (mean of urea and creatinine clearance) in women was half that of men (P = 0.001). Age, height, weight, and plasma creatinine were significantly lower for women. A summary ofthe patient characteristics for each center is shown in Table 2. These are provided solely for descriptive purposes and no statistical analysis has been made because of the large number of comparisons. Most varia-

bles are similar among the centers apart from a lower incidence of peritonitis at Ospedale Maggiore and lower residual renal function at Karolinska Institute and UCLA. Subjective Nutritional Assessment

The classification of patients based on subjective nutritional assessment is shown in Table 3. One hundred and thirty-three patients (59.4%) were classified as normal, 73 (32.6%) mildly to moderately malnourished, and 18 (8%) as severely malnourished. A larger percentage of women were classified in the malnourished groups, but a chisquare analysis failed to show a significant difference (P = 0.147). More diabetic than nondiabetic patients were classified as mildly to moderately malnourished (P < 0.05), but there were no differences for those in the severe group. All but four diabetics were insulin-dependent. Differences among centers are suggested, particularly by the wide variation among the centers in the percentages of patients that were classified as normal and the higher incidence of severe malnutrition in the two centers with the lowest mean residual renal function.

466

YOUNG ET AL

Table 3.

Classification of Patients Based on Subjective Nutritional Assessment Mild to Moderate Malnutrition

Normal N

%

N

%

85 48

64.4 52.2

39 34

29.6 37.0

8 10

6.1 10.9

132 92

22 111

48.9 62.0

21 52

46.7 29.0

2 16

4.4 8.9

45 179

40 41 10 20 14 8

63.5 77.4 27.8 60.6 48.3 80.0

21 11 17 7 15 2

33.3 20.8 47.2 21.2 51.7 20.0

2 1 9 6 0 0

3.2 1.9 25.0 18.2 0 0

63 53 36 33 29 10

133

59.4

73

32.6

18

8.0

224

Sex Male Female

Center Ospedale Maggiore Toronto Western Karolinska Institute UCLA Leeds Infirmary University of Missouri Total

Characteristics of Patients With Malnutrition

A univariate ANOYA was performed for each of the patient response variables to identify signifiTable 4. Correlation Between Nutritional Variables and Subjective Nutritional Assessment Multiple Correlation Coefficient (r) Variable

Male

Objective Plasma albumin (gIL) Plasma urea nitrogen (mmoI/L) Creatinine DIP Dialysate protein (g/d) Plasma transferrin (gIL) Plasma cholesterol (mmoI/L) Plasma triglyceride (mmoI/L) Patient age (yr) Months on CAPD MAMC (cm) UNA (mmol/d) % Body fat % Relative body weight Residual renal function (mLlmin) Peritonitis rate

NS NS NS NS NS NS NS NS 0.34t 0.25* NS 0.29t 0.27* NS NS

0.52:j: NS 0.36t NS NS NS NS NS NS 0.28* 0.33t NS 0.33t NS NS

Subjective Weight loss Anorexia Vomiting Edema Muscle wasting Subcutaneous fat loss

0.35:j: 0.42:j: NS NS 0.57:j: 0.57:j:

0.51:j: 0.43:j: NS 0.33* 0.63:j: 0.48:j:

*P < 0.05. tP < 0.01. :j:P < 0.001.

No. of Patients

%

N

Diabetic status Diabetic Nondiabetic

Severe Malnutrition

Female

cant correlations with subjective nutritional assessment, as listed in Table 4. The means ± SD for the correlated variables together with plasma urea nitrogen, creatinine, and residual renal function are summarized in Table 5. Residual renal function has been listed because it was significantly lower in severe malnutrition for both males (P < 0.001) and females (P < 0.01). Sixteen of 18 patients with severe malnutrition had no residual renal function, compared with 46 of 125 patients with normal nutritional states and 33 of 69 in the mild to moderate category. Mean plasma creatinine was not lower in the severely malnourished category, despite edema and the reduction in muscle mass, indicating uremia in some patients. The lower plasma urea nitrogen in women in this group may be due to their lower protein intake. The characteristics of patients with malnutrition are indicated in Table 5, and the levels of statistical significance are shown for descriptive purposes. Differences Among Centers

Half of the severely malnourished patients were from one center (Karolinska). These nine patients were the oldest in the study, the three men had a mean age of 67.3 years, and the six women averaged 57.5 years of age. All nine patients had been prescribed low protein diets before they commenced CAPD. Six patients in the severe group at UCLA had been on CAPD longer than all other patients, two women had a mean duration of 68 months on CAPD and four men had been treated for a mean of 60 months.

467

NUTRITIONAL ASSESSMENT IN CAPO

Table 5"

Objective and Subjective Variables (mean ± SO), Selected by Univariate ANOVA, in Patients Classified by subjective Nutritional Assessment Mild to Moderate

Normal

Sex: Male Objective Plasma albumin (giL) Creatinine DIP Months on CAPD MAMC (cm) UNA (mmol/d) (g/d) % Body fat % Relative body weight Plasma urea (mmoI/L) (nitrogen mg/dL) Plasma creatinine (pmoI/L) (mg/dL) RRF (mUmin) Subjective Weight loss Anorexia Edema Muscle wasting Subcutaneous fat loss Sex: Female Objective Plasma albumin (giL) Creatinine DIP Months on CAPD MAMC(cm) UNA (mmol/d) (g/d) % Body fat % Relative body weight Plasma urea (mmoI/L) (nitrogen mg/dL) Plasma creatinine (pmoI/L) (mg/dL) RRF (mUmin) Subjective Weight loss

Anorexia Edema Muscle wasting Subcutaneous fat loss

Severe

N

Mean

SD

N

Mean

85 81 85 85 85

4.30 0.17 21.87 3.58 74.76 2.10) 6.20 10.40 5.18 14.50) 323 3.66) 2.17

39 39 39 39 39

79

37.40 0.75 27.12 25.19 232.82 (6.54 23.19 99.60 23.21 (65.02 1,018 (11.52 1.81

36

36.30 0.75 33.23 23.66 198.65 (5.58 21.96 96.39 21.40 (59.94 953 (10.79 1.62

4.40 0.20 23.02 2.88" 60.16" 1.69)" 7.17 9.29 5.93 16.61) 230 2.60) 2.78

85 84 85 84 83

4.61 4.61 4.39 4.43 4.63

0.74 0.71 0.82 0.72 0.60

39 39 39 39 39

3.87 3.54 4.49 3.38 3.51

48 48 48 48 48

4.40 0.19 36.12 3.53 69.78 1.96) 8.40 20.13 7.18 20.10) 246 2.78) 1.39

34 33 34 33 34

46

37.20 0.72 36.90 22.89 187.61 (5.27 31.86 106.37 22.18 (62.14 954 (10.79 1.03

48 48 48 47 48

4.56 4.42 4.52 4.47 4.65

0.92 0.85 0.68 0.65 0.67

85 85 85 85

48 48 48 48

N

Mean

SD

8

33.50 0.65 49.88 22.17 183.70 (5.16 15.38 89.40 24.73 (69.28 1,042 (11.79 0.02

3.9" 0.34 28.27t 3.20" 54.47 1.53) 10.05 13.70 8.18 22.91) 236 2.67) 0.06;

1.13t 1.10; 0.68 0.96; 0.88;

8 8 8 8 8

3.38 3.63 4.75 2.63 3.13

1.69 1.69 0.46 1.19t 1.73"

5.40t 0.27 23.13 2.97 65.50 1.84) 8.15 12.86" 6.64 18.60) 304 3.44) 1.20

10 10 10 10 10

33

34.10 0.80 31.12 22.06 176.93 (4.97 30.07 96.89 21.89 (61.33 855 (9.67 0.74

10

27.00 0.64 38.80 20.40 110.00 (3.09 27.29 86.46 17.79 (49.82 856 (9.68 0.13

5.20; 0.27 28.72 3.02" 43.43t 1.22)t 8.38 16.57t 3.82" 10.71)" 101 1.14) 0.41t

34 34 34 33 33

4.06 3.76 4.41 3.64 3.91

1.07" 1.07t 0.78 1.06; 1.04t

10 10 10 10 10

2.40 2.90 3.90 2.30 3.40

1.35t 1.52" 0.88" 0.82; 1.43"

37 38 39 39

33 34 34 34

SD

8 8 8 7 8 7 8 8

8

9 10 10 10

Mean values significantly different from the normal category: "p < 0.05, t P < 0.01,; P < 0.001.

Differences Between Males and Females

Comparisons for 12 variables between males and females are shown in Figs 1 and 2 and Table 5. Anorexia and weight loss tended to be most marked in the women with severe malnutrition. Women also had a trend for most muscle wasting, lowest plasma albumin, and increased edema. The lower MAMC in the women as compared with the men is similar to the findings in normal individuals. The decrease in UNA in women probably reflects their lower protein intake. In men, many of these variables tended to show more gradual changes, and malnutrition was most clearly related to length of time on CAPD. As in normal individuals, the men in this study had a lower percentage

of body fat than the women. Men also had higher residual renal function, which, like the higher creatinine clearance in normal men, may be due to their greater muscle mass. 14 A matrix of partial correlation coefficients for all the variables selected is shown in Fig 3. Muscle wasting, loss of subcutaneous fat, weight loss, and relative body weight were the most correlated variables for both sexes. The most correlated variables for women were albumin and anorexia, and for men, UNA, loss of subcutaneous fat, MAMC, and months on CAPD. Residual renal function correlated with muscle wasting and also months on CAPD for both men and women, and for men alone, with creatinine DIP (dialysate: plasma or serum), UNA, relative body weight, and loss of subcutaneous fat.

468

YOUNG ET AL

M.A.M.C. (em)

WEIGHT LOSS

ANOREXIA

6

6

40

3

o

~ N

M

~

3

MUSCLE WASTING

o

S

M

N

S

~ N

M

S

M

N

% REL. BODY WEIGHT

U.N.A. (g/day)

150

12.

6

3

~

~ ---I

20

}.~-- T 6

S

~~ ..........

S

allow a few observations. In the CAPD patients without malnutrition (Table 5), MAMC for men (25.2 cm) was reduced compared with the median in normal men (28.7 cm), but the value for women (22.9 cm) was near the median in normal women (22.0 cm). These values were similar to those in hemodialysis patients (men, 25.9 cm; women, 22.8 cm). The two malnourished groups of male

ALBUMIN (g/dl)

6

S

M

N

No direct statistical comparisons between our results on CAPD patients with either normals or hemodialysis patients are possible because of the lack of strictly comparable data. A general comparison between this study and the National Center for Health Statistics' Health and Nutrition Examination Survey (NHANES)IS and also the National Cooperative Dialysis Study (NCDS),3 does

3

Fig 1. Means (± SE) for variables in males (-) and females (- - -) for each category of normal, mild to moderate, and severe malnutrition. RRF, residual renal function.

. . .,1:

M

N

~

75

% BODY FAT

LOSS SUBCUT. FAT

60

~ " ''f

30

6

I----i---_-r

3

~ o

N

M

S

N

Fig 2. Means (± SE) for five variables and the nutritional status score in males (-) and females (- - -) for each category of normal, mild to moderate, and severe malnutrition.

50

o

6

t~ N

M

S

S

EDEMA -

MONTHS ON CAPO

100

M

M

S

RRF

3

M

N

2.4

-~ N

~--

S

f-1.2

N

M

S

469

NUTRITIONAL ASSESSMENT IN CAPO

'!:

I-

.

0 I-

til % I-

z

w u

0 :I

II:

ALBUMIN (g/dO CREATININE DIP

~ *

-.24

MONTHS ON CAPO MAMC (em) UNA (9/day)

**

.32

Fig 3. Matrix of partial correlations for 12 variables and residual renal function (RRF). Some correlations were exclusive to females (broken outline) or males (bold outline) and the others were common to both. 'P < 0.05, "P < 0.01, "'P < 0.001.

EOEMA MUSCLE WASTING LOSS SUB. FAT

z

:I

""

~

I-

0

:>

w w

~

u.

III

til

:> til

:I

,

* *** -.31

*

I"" **

-.17 .22

.~

.18

* .24 ** .23*

l~ **

.26

I I

.24

* -.20 ......

** .29

j

** *** .32

* .21*

.19

*

Assessment of nutritional status has assumed greater importance because of the association of protein-energy malnutrition with increasing morbidity and mortalityY 19 However, it should be emphasized that the increased morbidity and mortality in patients on dialysis 3.9.11 could also be caused by the abnormalities of renal failure that contribute to their poor nutritional intake and status. There are no single variables that respond exclusively to changes in protein balance either in the short or long term. Consequently, in this study we have measured a wide range of variables that have some relevance in CAPD patients or have been

u

-.20

.22

DISCUSSION

I-

~

:I

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CAPD patients (23.7 and 22.2 cm) were below the 25th percentile of normals,16 and females (22.1 and 20.4 cm) were below the median of normals, and all were lower than hemodialysis patients. However, no comparable values for malnourished hemodialysis patients are available. Percentage body fat in all the CAPD groups, except males with severe malnutrition, was higher than for hemodialysis patients (men, 16.9%; women, 27.4 %). Comparable data from NHANES is not available. It may be concluded that malnourished patients on CAPD may show a greater degree of protein rather than energy malnutrition in comparison with those on hemodialysis.

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used previously to identify long-term effects of protein-energy depletion. Six features, weight loss, incidence of anorexia and vomiting, muscle wasting, edema, and loss of subcutaneous fat were derived from medical history and clinical examination, as described in a technique called subjective global assessment.1O The lowest ranked scores were assigned to the most severe abnormalities in these variables. All these features except vomiting correlated with our subjective assessment. Fifteen continuous variables were also included in subjective nutritional assessment, because they are widely used indices that are reproducible and easily measured. Seven of these were found to be significantly associated with subjective nutritional status. Plasma albumin was particularly important for women, and correlated with nutrition, muscle wasting, UNA, and the other nutritional variables. However, albumin is decreased by several factors, including fluid retention, increased vascular permeability, reduction in lymphatic return, increased catabolism, and decreased synthesis. 20 Several of these factors may have been enhanced during CAPD by albumin losses into the peritoneum, the peritoneal glucose load, and uremia per se. Nitrogen balance can be negative intermittently,5.21 or even continuously6.7 in some CAPD patients because of inadequate dietary intake or possibly metabolic and endocrine

470

disturbances. Dietary protein and energy supply can be insufficient to satisfy basal requirements and compensate for protein and amino acid losses into dialysis fluid, whereas uremia, associated with inadequate dialysis might increase catabolism, decrease anabolism, and cause anorexia. 5 Several factors that contribute to protein-energy malnutrition were assessed in this study. Measurement of food intake, although desirable, was not included because of the difficulty of collecting reliable data. 3 A ranked score for anorexia, which was used as an indication of inadequate dietary intake of protein and calories, and UNA, which was an estimate of protein consumed,21 contributed to the subjective assessment. Many factors, including glucose in dialysis fluid,5,9 medication, abdominal distention,21 superimposed acute or chronic illnesses, emotional factors, and possibly zinc deficiency5 may cause anorexia, Since our patients with severe malnutrition had no residual renal function, it is possible that uremic toxicity may have been an important cause of anorexia or wasting. It was notable that loss of residual renal function correlated with the length of time on CAPD and muscle wasting. In patients with anorexia, the protein, amino acid, and peptide losses into dialysis fluid and previously enhanced protein catabolism and peritoneal protein losses due to peritonitis, would be particularly likely to engender malnutrition. These effects probably were small for the majority of patients receiving adequate diets, since neither protein losses nor the incidence of peritonitis correlated with nutritional status. The average length of time on CAPD for patients in this study e)S.ceeded 2112 years, and most were in a normal state of nutrition. However, some degree of malnutrition was seen in all centers and in approximately 40% of patients overall. Some of the variation between centers for the numbers assigned to each category was not subjective. The age and nutritional status of patients at the start of CAPD, residual renal function and the subsequent length of treatment correlated with many of the differences, although other causes, such as geographical location and regional variation in diet, cannot be excluded. It is noteworthy that in maintenance hemodialysis patients, the duration of dialysis treatment does not seem to correlate with the severity of protein-energy malnutrition. 22 The higher incidence of mild to moderate malnutrition in diabetics than for nondiabetics might be due to additional complications such as increased perito-

YOUNG ET AL

neal protein 10sses.23 Diabetes mellitus itself does not seem to be a risk factor for increased malnutrition in patients undergoing maintenance hemodialysis. 24 Our observation that fewer diabetics progressed to severe malnutrition could reflect the lower survival rates for these patients 25 or a tendency for diabetic patients undergoing CAPD to retain residual renal function more effectively. 26 Many features of malnutrition were similar for both males and females; however, there were differences. In women, there was a trend toward more anorexia and greater weight loss from muscle wasting, with a more marked decrease in plasma albumin and increase in edema. In contrast, the men had greater reserves of muscle and a smaller percentage of body fat, with more gradual weight loss, muscle wasting, and decrease in albumin. The progressive decrease in UNA, body weight and fat were all related to the loss of residual renal function. The greater UNA, MAMC, and residual renal function and lower percentage body fat in male as compared with female patients may reflect the normal differences in protein intake, height, weight, and body composition between the two sexes. 12,15 This study has provided the opportunity to assess the nutritional status of 223 CAPD patients in six centers, from a large number of ordinal and continuous variables. Our data suggest that protein-energy malnutrition may occur in CAPD patients. Assuming the patients reported in this study are representative of the general CAPD population, nutritional assessment based on the 12 variables given in Table 5 can be applied to categorize patients. Comparable information for the hemodialysis population is not available. Although this study was not designed to examine the causes of malnutrition, certain tentative conclusions can be made. The marked anorexia and low residual renal function in our patients suggest that inadequate nutrient intake and uremic toxicity may have been important contributors to protein-energy malnutrition. As anorexia itself may be caused by uremic toxicity, it is possible that more effective peritoneal dialysis (increased frequency and/or higher volume exchanges) and greater efforts to maintain good nutritional intake may improve the nutritional status of these patients. ACKNOWLEDGMENT The authors acknowledge the assistance of Juliana K. Dietmeier, Jill Gibson, Shirley M. Hobson, and Mary K. Zentz.

471

NUTRITIONAL ASSESSMENT IN CAPD

REFERENCES 1. Kopple JD: Dietary requirements, in Massry SG, Sellers AL (eds): Clinical Aspects of Uremia and Dialysis. Springfield, IL, Thomas, 1976, pp 453-489 2. Young GA, Swanepoel CR, Croft MR, et al: Anthropometry and plasma valine, amino acids, and proteins in the nutritional assessment of hemodialysis patients. Kidney Int 21 :492499, 1982 3. Schoenfeld PY, Henry RR, Laird NM, et al: Assessment of nutritional status of the National Cooperative Dialysis Study population. Kidney Int 23:S80-S88, 1983 (suppl 13) 4. Marckmann P: Nutritional status of patients on hemodialysis and peritoneal dialysis. Clin NephroI29:75-78, 1988 5. Lindholm B, Bergstrom J: Nutritional aspects of CAPD, in Gokal R (ed): Continuous Ambulatory Peritoneal Dialysis. Edinburgh, UK, Churchill Livingstone, 1986, pp 228-264 6. Williams P, Kay R, Harrison J, et al: Nutritional and anthropometric assessment of patients on CAPD over one year: Contrasting changes in total body nitrogen and potassium. Perit Dial Bull 1:82-87, 1981 7. Heide B, Pierratos A, Khanna R, et al: Nutritional status of patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Perit Dial Bull 3: 138-141, 1983 8. Anderson DH, Farrell PC: Metabolite generation and clearance variation in long-term CAPD, in Moncrief Jw, Popovich RP (eds): CAPD Update. Paris, France, Masson, 1981, pp 75-81 9. Young GA, Young JB, Young SM, et al: Nutrition and delayed hypersensitivity during continuous ambulatory peritoneal dialysis in relation to peritonitis. Nephron 43: 177-186, 1986 10. Detsky AS, McLaughlin JR, Baker Jp, et al: What is subjective global assessment of nutritional status? J Parenter Enterol Nutr 11: 8-13, 1987 11. Fenton SA, Johnson N, Delmore T, et al: Nutritional assessment of continuous ambulatory dialysis patients. Trans Am Soc Artif Intern Organs 33:650-653, 1987 12. Durnin JVGA, Womersley J: Body fat assessed from total body density and its estimation from skinfold thickness: Measurements on 481 men and women aged from 16 to 72 years. Br J Nutr 32:77-96, 1974. 13. Lachenbruch PA: Robustness of the linear discriminant

function, in Discriminate Analysis. New York, NY, Hafner, 1975, pp 41-45 14. Doolan PD, Alpen EL, Thiel GB: A clinical appraisal of the plasma concentration and endogenous clearance of creatinine. Am J Med 32:65-79, 1962 15. Frisancho AR: New standards of weight and body composition by frame size and height for assessment of nutritional status of adults and the elderly. Am J Clin Nutr 40:808-819, 1984 16. Bishop Cw, Bowen PE, Ritchey SJ: Norms for nutritional assessment of American adults by upper arm anthropometry. Am J Clin Nutr 34:2530-2539, 1981 17. Goode AW: The scientific basis of nutritional assessment. Br J Anaesth 53:161-167, 1981 18. Beisel WR: Role of nutrition in immune system diseases. Compr Ther 13: 13-19, 1987 19. Wilson SM, Au FC: Assessing nutritional status in man. Dig Dis 5:212-221, 1987 20. Fleck A: Computer models for metabolic studies on plasma proteins. Ann Clin Biochem 22:33-49, 1985 21. Blumenkrantz MJ, Salusky ill, Schmidt RW: Managing the nutritional concerns of the patient undergoing peritoneal dialysis, in Nolph KD (ed): Peritoneal Dialysis. Boston, MA, Martinus Nijhoff, 1985, pp 345-401 22. Kopple JD, Grosvenor MB, Roberts CE: Nutritional needs for the elderly hemodialysis patient, in Oreopoulos DG (ed): Geriatric Nephrology. Boston, MA, Martinus Nijhoff, 1986, pp 127-134 23. Kriedet RT: Zuyderhoudt FMJ, Boeschoten EW, et al: Peritoneal permeability to proteins in diabetic and non-diabetic continuous ambulatory peritoneal dialysis patients. Nephron 42: 133-140, 1986 24. Kopple JD, Grodstein Gp, Roberts CE, et al: Nutritional status of the diabetic patient with chronic uremia, in Friedman EA, L'Esperance FA Jr (eds): Diabetic Renal-Retinal Syndrome. Philadelphia, PA, Grune & Stratton, 1980, pp 239-252 25. Brunner FP, Broyer M, Brynger H, et al: Survival on renal replacement therapy: Data from the EDTA Registry. Nephrol Dial Transplant 2: 109-122, 1988 26. Rottembourg J, Shahat EL, Agrafiotis A, et al: CAPD in insulin dependent diabetic patients, and a 40 month experience. Kidney Int 23:40-45, 1983