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Ann Thorac Surg 2004;77:301-305
© 2004 The Society of Thoracic Surgeons
a Nutrition Services, Green Lane Hospital, Auckland, New Zealand
b Pediatric Cardiology Department, Green Lane Hospital, Auckland, New Zealand
c Cardiothoracic Surgical Unit, Green Lane Hospital, Auckland, New Zealand
d Biostatistics Department, Green Lane Hospital, Auckland, New Zealand
Accepted for publication July 1, 2003.
* Address reprint requests to Ms Cormack, Nutrition Services, Green Lane Hospital, Greenlane West, Auckland 1030, New Zealand.
e-mail: bcormack{at}adhb.govt.nz
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Abstract |
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METHODS: A retrospective, single-institution 2-year study of all patients with a diagnosis of postoperative chylothorax was conducted. Chylothorax was diagnosed in 25 patients after a total of 535 cardiac operations in children younger than 10 years, for an incidence of 4.7%. Eighteen patients had been given Monogen, an enteral low long-chain triglyceride formula, as initial treatment. Six had been given total parenteral nutrition. The following variables were related to outcome and response to Monogen: age, sex, weight, underlying condition, type of surgery, interval between surgery and chylothorax diagnosis, duration and daily volume of chyle leak, central venous pressure, residual lesions, and weight loss.
RESULTS: Enteral feeding with Monogen was successful for 14 of 18 patients with a response to treatment evident by the end of the third day. No variables predicted which patients would respond to Monogen. Body weight was maintained or increased in 14 of the 17 surviving patients taking Monogen. A return to normal diet at 4 ± 1 weeks from the day of pleural drain removal did not result in recurrent chylothorax.
CONCLUSIONS: A trial of Monogen is recommended as initial treatment for postoperative chylothorax unless enteral feeding is contraindicated.
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Introduction |
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From May 1999 we began using Monogen (Scientific Hospital Supplies, Liverpool, England) instead of Portagen powder as enteral nutrition support for chylothorax. Monogen is a nutritionally complete, low-fat, whole whey protein, powdered feed containing 93% of fat as MCT. Compared with Portagen, Monogen has a lower level of long-chain triglycerides (LCT; 1.4 g/L) and a higher energy level of 74 kcal/100 mL; thus Monogen was thought to be a better choice (Table 1). The purpose of this study was to audit our use of Monogen for postoperative chylothorax and to formulate treatment guidelines in light of these results.
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Material and methods |
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Data on age, sex, weight, underlying condition, type of surgery, interval between surgery and chylothorax diagnosis, duration (defined as days from chylothorax diagnosis to removal of pleural drains) daily volume of chyle leak, average central venous pressure on day of diagnosis, residual lesions, reoperation, thoracic duct ligation, weight loss, and outcome were collected from medical and dietitians' records. Only postoperative chylothoraces were included. Surgical operations were arbitrarily categorized as neonatal surgery (neonatal arch obstruction, Norwood or arterial switch) (n = 8), tetralogy of Fallot or pulmonary artery surgery (n = 6), bidirectional Glenn or Fontan procedures (n = 6), and left-to-right shunt complete repairs (n = 5). A residual cardiac lesion was diagnosed if the patients had moderate or severe left ventricular impairment, significant residual ventricular septal defect, moderate or severe atrioventricular valve regurgitation, or significant pulmonary artery stenosis. The first day of treatment for chylothorax was defined as day 1.
The diagnosis of chylothorax was based on the presence of a persistent sterile effusion and confirmed by examination of the pleural fluid. Regardless of volume, a noninfectious milky appearance in orally fed patients with persistent chylous pleural effusion was considered diagnostic. A triglyceride level had been measured in 16 of 25 cases, and the concentration was higher than 1.1 mmol/L (> 110 mg/dL). Patients with the largest drain volumes tended not to have their triglyceride levels measured, as the diagnosis was intuitive.
Baseline characteristics were compared between the group who responded to Monogen and Monogen nonresponders. Response to Monogen was defined as recovery from the chylothorax with no further form of treatment (parenteral nutrition or surgery) required. The characteristics of patients who responded to either Monogen or TPN, defined as nutritional treatment, were also compared with those who did not respond to nutritional treatment. Response to nutritional treatment was defined as recovery from the chylothorax with no further surgery required.
Summary statistics have been presented as median and range. Baseline characteristics were compared using a Mann-Whitney U test, which compares the medians of two samples and is the nonparametric equivalent of a two-sample unpaired t test. The Fisher exact test was also used where appropriate. A nonparametric test has been used because of the small, unbalanced sample sizes and uncertainty about the distribution of the population from which the samples were drawn.
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Results |
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Fourteen of the 18 cases (78%) resolved on Monogen. Table 2 shows the baseline characteristics and outcome of the Monogen group. In the Monogen group, a substantial decrease of 17.3 to 6.1 mL/kg per day in median pleural drainage volume signaled a response to treatment by the end of the third day (Fig 1).
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Six patients had TPN as their initial treatment because they were unstable neonates or infants with high pleural drain volumes in the ICU rather than in the cardiac ward. Table 2 shows the baseline characteristics and outcome of the TPN group. Two recovered on TPN after 8 and 9 days, respectively, without further intervention. Two of the 4 who did not resolve underwent thoracic duct ligation. One had revisional surgery for a residual ventricular septal defect. The sixth patient died of irreversible pulmonary hypertension following repair of a Taussig Bing anomaly with hypoplastic right lung. Overall, 18 of the original 24 cases (75%) recovered after treatment with Monogen or TPN without need for further surgical intervention. Fourteen of the surviving 17 Monogen patients gained weight from the day of their surgery to hospital discharge. The remaining 3 cases were discharged weighing less than their weight at surgery, although their weight loss was less than 3%. Most of the group went home with Monogen treatment. The interval from the last pleural drain removal to the change to normal formula/diet varied from 1 to 15 weeks. Fifteen patients (68%) stayed on Monogen for 4 ± 1 weeks, and none of the patients reaccumulated a chylothorax after changing back to their normal diet.
Monogen responders versus nonresponders
A comparison of the 14 Monogen responders with the 4 nonresponders showed no significant difference in age, weight, sex, bilateral pleural effusion, central venous pressure, peak 24-hour volumes, triglyceride concentrations, or days from surgery to diagnosis. Three of the 4 nonresponders had residual lesions, but this difference was not statistically significant (p = 0.5865) All patients who responded to Monogen had decreased 24-hour drain volumes to less than 20 mL/kg by the end of day 4.
Nutritional treatment responders versus nonresponders
A comparison of the 16 nutritional treatment (Monogen or TPN) responders with the 8 nonresponders showed no significant difference in age, weight, sex, bilateral pleural effusion, central venous pressure, peak 24-hour volumes, triglycerides, residual lesions, or days from surgery to diagnosis.
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Comment |
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We have found that Monogen is an effective form of treatment for postoperative chylothorax in children. Chylothoraces had resolved by 3.5 days in 78% of patients. This rapid response with Monogen compares well with other forms of enteral feeding such as Portagen [3, 6, 7], Vivonex [3], and "fat-free formula" [8]. A positive response with reduction of chyle drainage occurred by the end of the third day. Based on our results, in the absence of contraindications to enteral feeding, we believe an initial trial of enteral feeding using Monogen is appropriate.
This study also shows that Monogen provides effective nutritional treatment for chylothorax. Body weight in our Monogen group was well maintained with 82% of our patients discharged weighing more than their preoperative weight. Weight loss was minimal in the other 18% (n = 3), less than 3% of total body weight. More significant weight loss has been seen with other patients with chylothorax when treated with other enteral formulas [7, 9]. Puntis and colleagues [9] reported 8% weight loss in a third of patients. Allen and colleagues [7] reported a higher than 10% weight loss in 22% of their cohort treated with Portagen.
We have not found other published reports on the use of Monogen for management of chylothorax. Previous studies have reported use of Portagen [3, 6, 7]. Table 3 summarizes studies using a variety of enteral and parenteral treatments. Several research groups have agreed that an enteral minimal LCT fat diet is as effective as TPN in controlling lymph leakage in appropriately selected patients [3, 7, 10].
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The rationale in our ICU for using TPN as the initial treatment was that enteral feeding may be poorly absorbed in the sick neonate or infant, resulting in a poorer nutritional status and the risk of precipitating necrotizing enterocolitis. In a few cases severe fluid restriction may necessitate the use of concentrated TPN to meet nutritional requirements. However, TPN has disadvantages, including gut stasis, catheter-related sepsis, and cost.
Our success with Monogen has led us to adjust our initial policy and we now intend to use the formula in ICU patients unless enteral feeding is completely contraindicated. If the pleural drainage is not decreasing by day 5 then TPN should be considered, but investigation for residual cardiac lesions is warranted and early reoperation should be undertaken where appropriate.
Timing of return to normal diet
It is generally recommended that patients stay on the MCT formula or minimal LCT fat diet for 3 to 6 weeks, but there is no clear consensus about this strategy or whether to begin timing the treatment from the date of diagnosis, pleural drain removal, finishing TPN, or discharge from hospital [3, 10, 11]. Staying on this restrictive diet longer than necessary is expensive and may mean breast-feeding is not reestablished.
This study provides some data about the timing of return to normal diet. None of the patients reaccumulated chyle after they were switched to a normal diet within 6 weeks, nor did the 6 patients who received Monogen for less than 4 weeks. This result confirms 6 weeks on the low LCT diet from the day of the last pleural drain removal is long enough to avoid recurrence. We currently recommend 4 weeks for the duration of Monogen or low LCT diet.
An algorithm for the treatment of pediatric postoperative chylothorax based on our findings and review of the literature has now been developed (Fig 2).
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In our study, the mean interval from surgery to diagnosis was 5.9 days in the Monogen group (range 1 to 21 days). This interval is shorter than Le Coultre's reported mean of 9.8 days and Beghetti's mean of 7.3 days for those who recovered quickly and 14 days for those with longstanding chylous losses [10, 12]. Earlier recognition and treatment in our group may also help to explain the apparently higher incidence of chylothorax in our unit. The reported incidence appears to increase as more complex surgery is performed [12]. Additionally, a recent trend has been to start feeding patients earlier after surgery, a strategy that may improve nutritional status but that has an unknown influence on the development of chylothorax.
With 92% survival, our group compares well with other published survival rates as summarized in Table 3.
Conclusions
Monogen is an effective high-energy enteral nutrition treatment for postoperative chylothorax in children. Response is usually rapid within 5 days and body weight is maintained. Treatment can be discontinued after 4 weeks without a recurrence of chylothorax.
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This article has been cited by other articles:
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  S.-y. Chan, W. Lau, W. H.S. Wong, L.-c. Cheng, A. K.T. Chau, and Y.-f. Cheung Chylothorax in Children After Congenital Heart Surgery Ann. Thorac. Surg., November 1, 2006; 82(5): 1650 - 1656. [Abstract] [Full Text] [PDF]
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E. H. Chan, J. L. Russell, W. G. Williams, G. S. Van Arsdell, J. G. Coles, and B. W. McCrindle Postoperative Chylothorax After Cardiothoracic Surgery in Children Ann. Thorac. Surg., November 1, 2005; 80(5): 1864 - 1870. [Abstract] [Full Text] [PDF]
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