chylothorax
Nutritional management of chylothorax patients Chyle passes from the intestinal lymphatics to the cisterna chili and then through the thoracic duct from which it will ultimately enter the venous system1. Chylothorax results in accumulation of lymphatic fluid or chyle in the pleural space following leakage from the thoracic duct. Shona Scott Cardiothoracic Dietitian, Royal Brompton & Harefield NHS Foundation Trust
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Shona Scott works as a Cardiothoracic Dietitian at the Royal Brompton & Harefield NHS Foundation Trust. In her job she treats patients with a variety of cardiac conditions and chronic lung conditions such as Chronic Obstructive Pulmonary Disease. She regularly sees patients with chylothorax following cardiac surgery.
Its aetiology can be traumatic or non-traumatic. Traumatic causes, which are most common, include cardiothoracic surgery, head and neck surgery and radiation, while non-traumatic causes can be cardiac failure, sarcoidosis, benign tumours, amyloidosis and congenital duct abnormalities2. The incidence of a chyle leak after surgery is approximately 1.0-4.0%3 and 0.2-1.0% specifically following cardiothoracic surgery4. There is scope for large amounts of fluid to rapidly accumulate in the pleural cavity as approximately 2.4L of chyle is transported through the lymphatic system every day2. Chyle is an odourless, alkaline fluid, 70% of which is absorbed dietary fat, mainly triglycerides4. In the fasting state, chyle will normally be clear but will have a milky appearance after a fatty meal. Equally, a person’s overall intake of fat, intestinal absorption and degree of physical activity5 will affect the fat content of chyle, but it generally ranges from 5.0-30g/litre4 or, in relation to body weight, will be between 10 Table 14: A detailed biochemical breakdown of chyle. Calories
200kcal/L
Lipids
5-30g/L
Protein
20-30g/L
Lymphocytes
400-6800/mm
Erythrocytes
50-600/mm
Sodium
104-108mmol/L
Potassium
3.8-5.0mmol/L
Chloride
85-130mmol/L
Calcium
3.4-6.0mmol/L
Phosphate
0.8-4.2mmol/L
and >100ml/kg. Chyle has 200kcal/L and a protein content of 20-30g/L6, although some studies state that this can be as high as 60g/L5. In addition, chyle contains lymphocytes, the majority of which are t-lymphocytes, fat-soluble vitamins, electrolytes and enzymes. Table 1 shows a more detailed biochemical breakdown of chyle. Presentation
Generally, chylothorax is asymptomatic until large volumes of fluid accumulate and the severity of the symptoms will be related to the rate at which the fluid accumulates and the amount of fluid in the pleural cavity1. Traumatic chylothorax normally develops within two to 10 days post injury1. The symptoms are typical of those seen with a pleural effusion and include dyspnea, coughing, chest discomfort and tachycardia7. More serious consequences of chylothorax and the most pertinent for this article are malnutrition due to the loss of protein, fats and fat-soluble vitamins4 and dehydration, hyponatraemia and hypocalcaemia due to the loss of electrolytes2. The loss of lymphocytes can lead to immunosuppression and increase the risk of infection, while the loss of large volumes of fluid can also cause hypovolaemia5. Diagnosis
Chylothorax is usually diagnosed by analysing the composition of the pleural fluid or chest drain. A triglyceride level of >110mg/dl is diagnostic of a chyle leak1, 2 and a level <50mg/dl rules out a diagnosis of chylothorax unless the patient has been fasting or is malnourished, in which case lipoprotein lipase analysis can be used4. NHDmag.com August/September 2015 - Issue 107
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