Peritonitis in Continuous Ambulatory Peritoneal Dialysis Patients

ORIGINAL INVESTIGATIONS

Peritonitis in Continuous Ambulatory Peritoneal Dialysis Patients Jack Rubin, M.D., Rice Ray, R.N., Tom Barnes, M.S., Nancy Teal, R.D., Eric Hellems, R.N., Joe Humphries, Ph.D., and John D. Bower, M.D. Peritonitis is the most important complication of continuous ambulatory peritoneal dialysis (CAPO). We reviewed our experience with peritonitis over a 2l h-year period. Our patients spent 4% of their total time on dialysis in hospital due to peritonitis. Thirty-eight percent of the episodes of peritonitis were treated without hospitalization. We evaluated the dialysate bag change technique as commonly performed with currently available devices (extension tubing and titanium Luerlock Tenckhoff catheter adapter). The aseptic techniques described for dialysis extension tubing changes appear adequate (with no increased incidence of peritonitis

P

ERITONITIS is the single most important complication of continuous ambulatory peritoneal dialysis (CAPD). We reviewed our overall experience with peritonitis, focusing upon etiologic agents and morbidity. We then sought to determine demographic factors associated with peritonitis, evaluate the dialysis equipment for possible inadequacies which may predispose to peritonitis, and characterize the influence of peritonitis upon the patients' serum chemistries and upper arm skin fold measurements . MATERIALS AND METHODS This paper reviews our overall experience with peritonitis from the inception of our program, February 1979, to August 1981. All patients entered into CAPD were included. After evaluation of the patients' histories, or renal biopsy where available, etiologic diagnosis of uremia was classified as chronic glomerulonephritis, chronic interstitial nephritis, hypertensive nephrosclerosis, or diabetes mellitus. Patients in whom no conclusive etiologic diagnosis could be ascertained were classified as " no diagnosis." The demographic characteristics of the patients were obtained from the initial evaluation by our social workers. We reviewed each patient 's age; race ; sex ; marital status, defined as married, common law relationship , or not married; total education in years; rural or urban residence, the latter defined From the Department of Medicine, Department of Family and Preventive Medicine, The University of Mississippi Medical Center, Jackson, Miss. Address reprint requests to Jack Rubin, MD , Nephrology Division , Department of Medicine, 250 North State Street, Jackson. MS 39216. © 1983 by the National Kidney Foundation. 1nc. 0272-6386/83/060602-02$01.00/0

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demonstrated shortly after an extension tubing set change). Long-term sterility is maintained at the dialysate bag puncture port and at the orifice of the dialysis catheter adapter (no positive cultures from the bag port and orifice of the titanium adapter) . Etiologic diagnosis of uremia was not a risk factor predisposing to peritonitis. The incidence of peritonitis was greater among patients with less formal education and lower income. Our data suggest that patients with less formal education and of lower economic status be carefully evaluated before commencing CAPO .

as living in a town of greater than 2500 people; income, defined as greater than $10,000 or less than $10,000 (including welfare income) at the start of the dialysis; and whether the patient required a helper to puncture the dialysate bag (an index of infirmity). Peritonitis was defined as the presence of turbid dialysate associated with fever, an elevated dialysate cell count, or positive culture. We diagnosed peritonitis in these instances when turbid dialysate persisted for at least one day whether or not cultures of dialysate yielded organisms. The emphasis was placed on the patients' observation of turbid dialysate, since this determined whether a patient obtained a dialysate culture and commenced antibiotic therapy. Patients were instructed to obtain a dialysate culture and commence antibiotic therapy if turbid dialysate persisted after one or two rapid exchanges of dialysate. Patients administered antibiotics to themselves by instilling antibiotics with their infused dialysate. Patients who failed to improve or were unable to be managed at home were hospitalized.

CULTURE TECHNIQUES

Dialysate cultures were performed routinely at clinic visits. Dialysate was aspirated from the dialysate bag port using sterile technique, placed in a sterile tube, and transported to the University of Mississippi Medical Center laboratory within two hours of sampling. Dialysate cultures obtained in hospital were performed in a similar fashion. Cultures were performed in the following manner. The dialysate was streaked onto blood agar plates with a O.Ol-mL calibrated loop and a thioglycollate broth innoculated with 0.5 to 1 mL of dialysate using a Pasteur pipette. The blood agar plate was incubated in 5% to 10% CO 2 at 35 °C for 48 hours. The thioglycollate broth was incubated at 37°C for 48 hours and subculturedonto American Journal of Kidney Diseases, Vol. II, No.6, May 1983

PERITONITIS IN CAPO PATIENTS

blood agar plates if growth was observed. The blood agar plates contained trypticase peptone 15 giL, phytone peptone 5 giL, sodium chloride 5 gl L, agar 15 giL, and sheep blood, defibrinated 50 mLiL (BBL Microbiology Systems, Cockeysville, MD). Since transportation to the University of Mississippi at the onset of peritonitis could not be guaranteed, we also utilized laboratory facilities in the patients' communities. Patients were instructed to save the bags with the first appearance of turbid dialysate and to bring them to the local hospital laboratory. If they could not transport the dialysate immediately to the laboratory, they were asked to store the bags in the refrigerator. In all, 28 facilities were utilized (see Acknowledgments for listing). All but three facilities streaked the dialysate onto sheep blood agar. One facility utilized old human blood, and two only innoculated the dialysate into thioglycollate broth. All but three facilities incubated blood agar plates in CO 2 at 35 °-37 °C using a candle jar. All but three facilities innoculated the dialysate into thioglycollate broth at 37°C. All cultures were kept for at least 48 hours before being reported as showing no growth. EVALUATION OF DIALYSIS EQUIPMENT

The patients ' dialysis technique was as described by Oreopoulos et al. I Patients generally performed four dialysate exchanges per day. Two patients carried out five exchanges per day and two patients three exchanges. All dialysate was manufactured by 1tavenol Laboratories and contained lactate. The potential for a break in the technique occurs when the system must be opened. These instances occur at the time of dialysate refreshment when new and used bags are substituted, and at the time of change of the extension tubing set. At our institution, changing the tubing set attached to the Tenckhoff catheter via a Luer-Iock device (Travenol Labs) between the extension tubing and dialysis catheter is performed in clinic by the nurses. The adapter is made of titanium and inserted into the Tenkhoff catheter. We evaluated the relationship of the occurrence of peritonitis to changing of the extension tubing attached to the permament dialysis catheter. We cultured the inner aspect of the titanium adapter after disconnecting it from the old tubing and again

603

after a five-minute soak in povidone-iodine prior to replacement of the new tubing set. Swabs were taken from these areas using a Culturette device (Scientific Products, McGraw Park, Ill.). We evaluated the sterility of the spike of the extension tubing and the inner aspect of the dialysate bag port by culturing these areas just after a tubing set change performed during a routine clinic visit. Again, swabs were taken using a Culturette device. During this procedure care was taken so that no povidone-iodine solution came into contact with either of these two areas. The Culturette device contained Stuart's bacterial transport medium, 0.5 mL sodium glycerophosphate 1 %, sodium thioglycollate 0.1 %, and calcium chloride dihydrate 0.01 %. Upon arrival at the University laboratory, the swabs were innoculated as described. SKIN FOLD EVALUATION, CHEMISTRIES

We also measured upper arm skin folds . Evaluation of patients at each clinic visit was performed by one dietician using Lange calipers . The left arm was used unless an access device was present. The same arm was used at each clinic visit. 1ticeps skinfold and mid-arm circumference were obtained and upper arm muscle area calculated,2 using the following formula: Upper arm muscle area (mm2) = (upper arm circumference (mm) 'lr * triceps skin fold (mm» 2/(4 * 'lr)

Patients were weighed in clinic without shoes or overcoats and after dialysate had been removed from them. A creatinine clearance was obtained within 3 months of starting home dialysis. Serum chemistries were obtained at each clinic visit and analyzed at the University of Mississippi Clinical Laboratories using autoanalyzer techniques. * *Technicon Autoanalyzer Methods, Thrrytown , NY. Glucose SG4-0046FH9 Thtal protein SG4-00144FH9 Urea nitrogen SG4-0001FH9 Albumin SG4-0030FH9 Creatinine SG4-0011FH9 Cholesterol SG4-0040FH9 'friglycerides SG4-0023FH9 Uric acid SG4-0054FH9 Alkaline phosphatase Sodium SG4-0033FH9 SG4-0006FH9 SGOT SG4-00lOFH9 Potassium SG4-0034FH9 LOH SG4-0021FH9 Chloride SG4-0005FH9 CPK SG4-OO17FH9 Carbon dioxide SG4-00337FH9 Total bilirubin SG4-OO18FH9 Calcium SG4-OOO3FH9 Direct bilirubin Phosphorus SG4-0004FH9 SG4-OO35FH9

604

RUBIN ET AL

We also evaluated our data for trends over time on dialysis by regressing each patient's hematocrit, body weight, upper arm muscle area, and serum values (including glucose, blood urea nitrogen, creatinine, carbon dioxide content, calcium, phosphorus, total protein, albumin, cholesterol, triglyceride , and alkaline phosphatase) against time on dialysis. We assumed that the changes were linear over time. The slope of the variable regressed against time on dialysis in days for each patient was obtained, and an overall mean slope was derived for each group. These mean values in each group for each parameter were tested to determine whether the group slope was significantly different from 0 (no significant slope) by dividing the overall "mean slope" by the standard error of the mean for the "mean slope ." This yields a t statistic with n-l degrees of freedom. If the slope is not significantly different from 0 there is no group trend over time. If the slope is significant and the overall result is positive, it suggests that the trend is upward for that parameter. If the slope is significant and the overall result is negative, it suggests the group trend is significantly downward. The mean values for each group were also compared for significant differences by Student's (-test. 4

DATA ANALYSIS

We calculated infection rate, defined as the number of infections divided by time on dialysis (the inverse is calculated to obtain a true zero when averaging the infection rate) ; morbidity, defined as the number of days in hospital divided by time on dialysis; morbidity secondary to peritonitis, and group average morbidity. The calculation of the group average morbidity, morbidity due to infection, and infection rate differs from the calculation of overall morbidity. It is possible to spend 20 of 40 total days in hospital, a morbidity of 0.5, and have another patient with 20/100 days for a morbidity of 0.2. The average morbidity is 0.35, the total morbidity 401140 is 0 .285. By defining the patients into groups defined by the population, we sought to isolate demographic risk factors that might be related to peritonitis and morbidity. We separated the patients into groups defined by the dichotomous variables (sex, income, marital status, etc.) . We also analyzed the patients removed from CAPD because of peritonitis versus the remaining population; patients without peritonitis versus those with at least one episode of peritonitis; and patients allocated to CAPD by a physician due to hemodynamic instability on hemodialysis or lack of vascular access versus patients who choose CAPD as a therapy. We then analyzed the demographic characteristics of these subgroups by chi-square with correction for continuity and the morbidity and infection rate data by Student's (-test. 3 We attempted to determine whether peritonitis altered patient serum chemistries by comparing overall mean serum values for patients withdrawn from CAPD due to peritonitis to the rest of the patients . One mean value for each parameter was obtained and the group means compared by Student's (-test. Table 1.

RESULTS

During the period of this study we trained 56 patients for home dialysis. There were 14,283 patient days at risk, of which 1004 days were spent in hospital. Of these 1004 hospital days 57 % were related to peritonitis or 4 % of their total dialysis experience. Thirty-eight percent of the episodes of peritonitis were managed on an outpatient basis. Thble 1 details, by six-month intervals since the inception of our program, the percent age of episodes of peritonitis in which culture revealed

Organisms Encountered During Peritonitis Episodes by Six-Month Intervals Since Inception of our Program Organisms (%)

Time in Six Month Periods

Total No. of Episodes

Gram-Negative

Gram-Positive

1 2 3 4 5

23 19 18 20 37

30 42 39 40 24

43 26 28 25 26

'One episode of Nocardia asteroides peritonitis.

Gram-Negative & Gram-Positive

No Growth on Culture

13 5

9 22 22 35 42

5

'Fungus

5 5 11 3

PERITONITIS IN CAPO PATIENTS

605

gram-positive organisms, gram-negative organisms, both gram-positive and gram-negative organisms, fungus, or no growth from dialysate culture. There has been no marked change in the percent of gram-positive and gram-negative infections. There has been an increase in cultures failing to yield organisms. Peritonitis has been associated with death in two patients. In both instances the deaths were associated with peritonitis secondary to a fungal organism. There were 59 episodes of peritonitis in which cultures were taken to the local hospital, of which 25 yielded gram-positive organisms, 8 gramnegative organisms, 1 a fungus, and 25 no growth. Among the patients with clinical peritonitis in whom dialysate culture at the local facility failed to yield organisms, four patients required hospitalization for persistently turbid dialysate. In two instances we also failed to obtain a positive culture, and in two patients culture subsequently yielded a gram-negative organism and a fungus, respectively. Figure 1 details the probability of first infection for those patients on and off CAPD at the close of the study. These figures were calculated similarly to a survival curve by the method of Kaplan and Meier, except that the end point was the clinical diagnosis of infection. 5 This figure illustrates that patients removed from CAPD often developed peritonitis soon after initiating CAPD. Table 2 details the time to the first clinical episode of peritonitis. It also details the time to the second clinical peritonitis following an initial gram-positive, gram-negative, or no-growth event. Forty-two patients developed a clinical episode of peritonitis within 79 ± 14 (SEM) days of starting CAPD (median 57 days). In 26 patients, a second episode occurred within 69 ± 11 (SEM)

z: .90

~ -BO

c..> ~

.70

:: _60 .:!!. .50

....~

AO

~ .30 ~

20

JO

°0~~~~~BO~~12~0~1~60~~~~~~

540

DAYS ON DIALYSIS

Fig. 1. Probability to the first clinical episode of peritonitis for patients undergoing CAPO at the close of the study and for patients removed from CAPO.

Table 2. Time Between Infections

Time Between Episodes of Peritonitis Patients (N)

Median (Days)

Mean ± SEM (Days)

0& 1st Range

42

57 (6-502)

79 ± 14

1st & 2nd Range

26

47 (8-211)

69± 11

2nd & 3rd Range

15

33 (13-238)

52 ± 14

3rd & 4th Range

12

79 (15-310)

82 ± 24

4th & 5th Range

8

45 (5-409)

103 ± 45

days (median 47 days) of the first infection. In patients who became reinfected and were not removed from dialysis, peritonitis occurred at increasing time intervals. We could not demonstrate a difference in the length of time to the first clinical episode of peritonitis for episodes of peritonitis due to gram-positive, gram-negative, or nogrowth organisms. The mean time from the start ofCAPD to a first infections was 82 ± 16 days for a gram-positive organism, 107 ± 35 days for a gram-negative organism, and 48 ± 12 days for an episode that failed to yield a growth on dialysate culture. Analysis of Patient Subgroups

In our patient population there were 16 patients diagnosed with chronic glomerulonephritis, 9 with chronic interstitial nephritis, 10 with hypertensive nephrosclerosis, 14 with diabetes mellitus, and 7 with either no diagnosis or another diagnosis. Infection rate, morbidity, morbidity related to infection, education, and age were not significantly different between groups of patients with differing etiologic diagnoses of uremia. Analysis of patient subgroups defined by the dichotomous variables revealed that the low-income group of patients as compared to the high-income group had a greater incidence of peritonitis (77 ± 28 days, N = 39 versus 288 ± 46 days, N = 17; P < 0.01), increased overall morbidity (0.09 ± 0.01 versus 0.05 ± 0.01, P < 0.05), and increased morbidity related to peritonitis (0.05 ± 0.01 versus 0.01 ± 0.01; p < 0.01). Furthermore, this group of individuals had less formal education (7.7 ± 0.07 years versus 9.1 ± 1. 1 years; p < 0.05; see Table 3). This is shown again if we analyze the demographic characteristics of patients who had never

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Influence of Residual Renal Function

Table 3. Patient Income Related to Demographic Features and Morbidity

Black White Male Female Married Not married Age (yr) Education (yr) Incidence of peritonitis (days)' Total morbidity' Peritonitis-related morbidity' Time on dialysis (days) Number of patients off CAPO,

Income <$10,000 N; 39

Income >$10,000

29 10 11 28 19 20

4 13 12 5 15 2

N;17

50.0 ± 1.8t 51.0 ± 3.1 7.7 ± 0.7; 9.1 ± 1.1 77 ± 28 .09 ± .01

288 ± 1.1 .05 ± .01

.05 ± .01§ .01 ± .01 250 ± 36 266 ± 51 20

5

'The mean derived from each patient as described in the text. t= X ± SEM. ;= p < 0.05; income < $10,000 versus income> $10,000. § = p < 0.01; income < $10,000 versus income > $10,000. , = income> $10,000; 1 patient transplanted, 1 patient transferred.

had peritonitis during this review period versus patients who had had at least one episode. The noperitonitis group was associated with greater educational achievement (11.9 ± 1.0 years, N = 13 versus 9.2 ± 0.6 years, N = 43; p < 0.01), income (chi-square = 9.82) and more white patients (chi-square = 10.1). This is likely a reflection of income, since there were more black patients in the lower income group (chi-square = 10.97; p < 0.01). Although we expected the group of patients allocated to CAPD to have increased morbidity, we did not find this to be true. Even though this group was significantly older than the other patients (54 ± 2 years, N = 27 versus 40 ± 3 years, N = 29; p < 0.01), the demographic features of the groups (assigned to CAPD or choosing CAPD) were otherwise similar. Furthermore, patients who required a helper to puncture the dialysate bag port were significantly older than those who did not (55.2 ± 4.2 years versus 41.9 ± 2.1 years; p < 0.01), but this group of patients did not have an increased incidence of peritonitis or morbidity. These data suggest that demographic factors are of major importance in determining morbidity.

Evaluation of creatinine clearance, corrected to 1.73 m2 , obtained within three months of starting dialysis, showed that clearance was significantly less in the group of patients withdrawn from CAPD due to peritonitis compared to the rest of the patients (1.46 ± 0.44 mLimin, N = 14 versus 2.91 ± 0.48 mLimin, N = 38; p < 0.025). When we correlated the infection rate of each patient to residual creatinine clearance (x axis) we noted a significant correlation (p < 0.025, r = -0.29, slope = -0.0009, intercept = 0.0128). This was due to two patients with residual clearances of 10 and 13 mLimin, respectively, who had not had peritonitis. When these two patients were removed the curve was not significant (p < 0.07). Trend Analysis

Table 4 shows selected results from the overall mean serum values. Aside from mean serum glucose, which was lower in the peritonitis group, there were no significant differences in the serum chemistries. Trend analysis revealed that the overall trend for blood urea nitrogen was negative (p < 0.05) in both groups of patients. Among patients not removed from CAPD due to peritonitis there was a positive trend for serum bicarbonate (p < 0.05), whereas serum bicarbonate was stable in the group removed from CAPD due to peritonitis. Among patients removed from CAPD due to peritonitis, serum total proteins and albumin demonstrated a negative trend, whereas upper arm area was stable. The remaining patients evidenced stable serum proteins and a positive trend in upper arm area. All other parameters were stable over time on dialysis. Evaluation of Dialysis Procedure and Devices

Cultures were obtained from the exension tubing spike from 21 patients at routine clinic visits. All of these cultures were negative. Following this, 34 cultures were obtained from the dialysate bag port simultaneously with cultures from the extension tubing spike from 30 patients at routine clinic visits. In the latter series all but two cultures were negative. The two positive cultures were derived from both the tubing spike and the bag port. They yielded Acinitobacter anitratus in one instance and Staphylococcus epidermidis in the second instance. These positive cultures were associated

PERITONITIS IN CAPO PATIENTS Table 4.

607 Overall Mean Values and Results of Trend Analysis Patients Withdrawn from CAPD due to Frequent Peritonitis (N = 14)

Glucose (mg/100 mL) BUN (mg/100 mL) Creatinine (mg/100 mL) Bicarbonate (mEq/L) Total proteins (g/100 mL) Albumin (g/100 mL) Hematocrit (vol %); Weight (kg) Upper arm area (mm2) Ccr (1.73 M2) (mLlmin)§ Incidence of peritonitis (days) Time on dialysis (days) *P

All Other CAPD Patients (N = 42)

X

±

SEM

t118 55 13 23 6.0 3.1 28 65 4649

± ± ± ± ± ± ± ± ±

8 5

1.5

±

.4,

2.9

±

.5

54

±

29**

137

±

21

261

±

37

255

±

57

1 .2 .1 2 5 640

X

Slope

.07 - 0 .9 -.01 .01 - .01 - .004 .04 -.01 -2.04

± ± ± ± ± ± ± ± ±

24 .04* .01 .01 .002 .002t .03 .03 5.78

153 59 11 22 6.2 3.3 28 60 3889

±

SEM

± ± ± ± ± ± ± ± ±

12 4 1 .5 .1 .1 1 2 162

Slope

-2.78 - 9 .7 - 0 .6 .15 -.02 -.01 - 0 .4 -.04 2.30

± ± ± ± ± ± ± ± ±

2.35 53* .04 .09* .02 .01 .04 .04

.77

< .05; slope significantly different from O.

* * P < .01 peritonitis withdrawn versus all other patients. t = p < .01; slope significantly different from O. ;Slope N = 12 in peritonitis group. §N = 38 in the group not withdrawn for peritonitis. < .025 peritonitis withdrawl versus all other patients.

,P

with dialysate cell counts of less than 34/mm 3 , and peritonitis did not occur. We evaluated the association of peritonitis with a dialysate tubing set change in 31 patients from 1/3/ 81 to 8/27/81. This included all active patients attending clinic or in training for this period. There were 74 tubing changes (1 to 5 per patient with a mean time between tubing changes of 60 ± 18 days, range 12 to 117 days) and a median time of 56 days. There were 29 episodes of peritonitis in 16 patients during this period . Seven patients had had nine tubing changes in hospital and subsequently developed peritonitis. Since the date of tubing change was unknown to us, the ten episodes of peritonitis occurring to these individuals were deleted from this analysis of the remaining repsodes of peritonitis . Nine patients developed peritonitis 19 times . Eight cultures of dialysate failed to yield organisms , eight cultures yielded grampositive organisms, and three yielded gramnegative organisms. During this period the mean time to peritonitis following tubing change was 26 ± 17 days (range 5 to 69) and the median time 24 days . The titanium adapter is a Luer-lock device to prevent disconnection of the dialysis tubing from the dialysis catheter. We evaluated the titanium adapter device (Travenol Labs) from 9/15/80 to

12/17/80. We cultured the inner lumen of the titanium adapter at disconnection of the old extension tube prior to a five-minute soak in povidone-iodine and after a five-minute soak in povidone-iodine (20 sets of cultures from 13 patients) . All cultures were negative. We were able to evaluate seven patients who had been on CAPD prior to the titanium adapter device and who remained on CAPD after the device became available. We analyzed the number of episodes of peritonitis/days on dialysis before and after titanium adapter insertion. The infection rate was significantly improved in these patients following the insertion of the titanium adapter (p < 0 .05 , paired Students' t-test). There were 21 infections in 1854 days of dialysis prior to the advent of the titanium adapter and 10 in 2730 days after (p < 0.05) . It appears that a device that maintains integrity of the dialysis tubing connection helps prevent infection. DISCUSSION

The incidence of peritonitis in our program is comparable to results reported by some established programs but greater than others. 6 .7 It is not clear why results differ. The incidence of peritonitis among our patients in the high income group is similar to those reported by Fenton et al (demo-

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608

graphic characteristics not reported).7 Our results suggest that demographic characteristics of patients are determinants of the incidence of peritonitis. We have found a higher incidence of gramnegative infections than other reports. 7.8 Aside from demographic differences we do not know why our results differ. 67 We cannot ascribe this to diverticulitis, peptic ulcer disease , or urinary tract infections. In part this may be explained by the number of dialysate cultures failing to yield bacterial growth and thus leading to an underestimation of gram-positive organisms. We are concerned that most of our episodes of peritonitis that failed to yield organisms on dialysate culture were obtained from cultures taken to local facilities. Although the culture techniques among the laboratories appear similar, each individual facility evaluates relatively few dialysate cultures . It is possible that the greater experience in processing dialysate cultures at the University of Mississipi yielded better results. Since the close of this study we have been attempting to centralize our dialysate cultures by asking the patients to mail in a "dipstick" culture device (Total Count Water lester, Millipore Corp., Bedford, Mass.) Our data are too preliminary to report. The devices used to accomplish CAPD appear safe if there is adequate patient dexterity. If a peritonitis episode does occur, the patient may commence treatment at home. The titanium adapter and cultures from the tubing spike did not yield organisms when the patients were reviewed in clinic (after initiating therapy at home). We cannot state conclusively that the orifice was not contamined and then became sterile, since cultures were not obtained from the tubing and adapter when the patients were admitted with peritonitis. Although the advent of a Luer-lock device between the Tenckhoff catheter and extension tubing alleviated the risk of patient disconnection, the system as described still lacks adequate safety. It is too dependent upon the patient performing the technique without significant error. Newer devices such as in-line filters or connections between patient and dialysate still suffer from the fact that the procedure is an open system. We were not able to demonstrate any changes in serum overall mean chemistries when patients withdrawn due to peritonitis were compared to the rest of the CAPD population. This may be related to the insensitivity of the technique of evaluation. Since patients are assessed after an episode of peri-

tonitis, changes if any, may no longer be present. Because of the difficulty in determining short-term changes and since reports have suggested that toofrequent episodes of peritonitis or inadequate dietary intake are associated with loss of lean body mass, we undertook an analysis of trends over time on dialysis. 9 , 10 The increase in upper arm muscle area , stable hematocrit, and serum proteins in patients not removed from CAPD due to peritonitis suggests that these patients are nutritionally stable, whereas the negative trend in serum proteins in the peritonitis group suggests these patients are not. This information , together with the creatinine clearance data suggesting that residual renal function may be an important index of host defense against peritonitis, warrants further evaluation. In our population we initiate home therapy for peritonitis using a combination of intraperitoneal tobramycin sulfate and cephalothin sodium. We do not yet know the long-term risks of excessive aminoglycoside exposure (implications for residual renal function and vestibulo-auditory impairment), but we believe this broad spectrum therapy is necessary because of the high incidence of gram-negative organisms obtained from culture. This therapy may diminish residual renal function in the high-risk patient and , .together with poorer nutritional health , further impair host defense mechanisms . Peritonitis remains the single most important complication of continuous ambulatory peritoneal dialysis. Aside from the patient discomfort when hospitalization is required, it adds significantly to overall costs of dialysis therapy. All our analyses suggest that the most important associations with peritonitis are related to demographic characteristics: poverty and lack of education. The other variables discussed are not as important. We do not believe our results are due to a bias in our home training programs. Our poor patients with a lack of formal education trained for home hemodialysis do not have increased morbidity. 11 Furthermore, the same home-training nurses taught both groups of patients. Since these patients are so difficult to maintain on dialysis, our data suggest that this group of patients be more carefully evaluated prior to undertaking CAPD. ACKNOWLEDGMENTS We wish t o acknowledge the support of the following laboratories, which performed dialysate cultures for our patients: Oktibbeha County Hospital , Starkville, Miss. Columbus Pathology Lab., Columbus, Miss. Field Memorial Community Hos-

PERITONITIS IN CAPD PATIENTS

609

pital, Centreville, Miss. Golden Triangle Regional Medical Center, Columbus, Miss. Hardy Wilson Memorial, Hazelhurst, Miss. Kings' Daughter's Hospital, Greenville, Miss. S. E. Lackey Hospital, Forest, Miss. Jefferson Davis County Hospital, Prentiss, Miss. Jefferson Davis Memorial Hospital, Natchez, Miss. Jones County Community Hospital, Laurel, Miss. Wayne Gen. Hospital, Waynesboro, Miss. Southwest Mississippi Regional Medical Center, McComb, Miss. F. G. Riley Memorial Hospital, Meridian, Miss. South Sunflower County Hospital, Idianola, Miss. Humphreys County Memorial Hospital, Belzoni, Miss. Simpson General Hospital, Mendenhall,

Miss. Walthall General Hospital, Tylertown, Miss. Greenwood/Leflore, Greenwood, Miss. Tallahatchie Hospital, Charleston, Miss. Grenada County Hospital, Grenada, Miss. Vicksburg Hospital, Vicksburg, Miss. Pathology Laboratory of Hattiesburg Clinic, Hattiesburg, Miss. Delhi Clinic, Delhi, La. Chicot Memorial Hospital, Lake Village, Ark. Ivy Memorial Hospital, West Point, Miss. Franklin Parish Hospital, Winnesboro, La. We also wish to acknowledge the support of the 7 West staff, the Home Training staff, and the secretarial support of Jan Izard.

REFERENCES 1. Oreopoulos DG, Robson M, Izatt S, et al: A simple and

safe technique for continuous ambulatory peritoneal dialysis (CAPD). ltans Am Soc Artif Intern Org 24:484-489, 1978 2. Friscancho AR: New norms of upper limb fat and muscle areas for assessment of nutritional status. Am J Clin Nutr 34:540-545, 1981 3. SAS Users Guide, 1979 edition. SAS Institute Inc., Cary, NC, 1979 4. Wallenstein S, Zucker CL, Fleiss JL: Some statistical methods useful in circulation research. Circ Res 47:1-9, 1980 5. Dalbfeisch A, John D, Prentice RL: The statistical analysis of failure time data. New York, Wiley, 1980 6. Nolph KD, Sorkin M, Rubin J, et al: Continuous ambulatory peritoneal dialysis: Three year experience at one center. Ann Intern Med 92(5):609-613, 1980 7. Fenton S, Wu G, Cattran D, et al: Clinical aspects of peri-

tonitis in patients on CAPD. Peritoneal Dialysis Bull 6 (suppl 1):54-57, 1981 8. Rubin J, Rogers W, Taylor H, et al: Peritonitis during continuous ambulatory peritoneal dialysis. Ann Intern Med 92(1):7-13, 1980 9. 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. Peritonal Dialysis Bull 1(6):82-87, 1981 10. Rubin J, Flynn M, Nolph K: Total body potassium-a guide to nutritional health in patients undergoing continuous ambulatory peritoneal dialysis. Am J Clin Nutr 34(1):94-98, 1981 11. Rubin, J, Barnes T, Burns P, et "I: Comparison of home hemodialysis (HHD) to continuous ambulatory peritoneal dialysis (CAPD). Kidney Int 23:51-56, 1983