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Welcome back to the tasty morsels of critical care podcast.
Today we’re talking about chylothorax, not something I’ve not had the joy of managing as yet.
Chyle is produced through digestion and absorption of emulsified fats from the small intestine. It consists of triglycerides, white cells, and these wonderful things called chylomicrons.
Chyle is not generally meant to be in the thorax unless it’s simply passing through in the fragile (and frequently mistaken by surgeons) thoracic duct. The chyle makes it way up the thoracic duct to drain into the venous system.
This is all well and good till the thoracic duct is standing on the street corner minding its own business, when it is injured by any number of causes such as:
- surgery (though I’m sure they’ll blame anaesthesia)
- infection (filiariasis and TB)
Clinically you would expect to see a pleural effusion (mainly unilateral) with milky white pleural fluid coming out of it if you decided to drain it. In terms of the timescale related to surgery it’s often a few days lag before the effusion is clinically apparent.
From an exam point of view you might be asked how you might distinguish this white milky fluid from some propofol that had been infusing into the chest for a few days from a misplaced central line (true story!). You could say there would be high triglycerides which would be true but wouldn’t help you to distinguish it from the milk of amnesia, propofol. Trigs can also be low in a fasted patient which these guys suffering from the complications of surgical misadventures often are. The best answer is to get your lab to do electrophoresis on the fluid looking for chylomicrons.
Management wise it seems that if there’s a surgical cause then non operative management is an option and if it’s a non operative cause then surgery might be your fix. There does appear to be a broad variety of surgical and interventional options many of which seem to be basically tying the ends off.
From an ICU perspective we’re going to be more interested in the non surgical options, which are variations on a theme of reducing chyle flow through the injured duct. You can do this by altering their nutrition to focus on medium chain fatty acids which are apparently easier absorbed through the portal venous system and don’t need the thoracic duct. You could skip the gut completely and use TPN. Finally you could try our all purpose secretion drier upper – octreotide.
As you can imagine for a condition so rare there is not a great deal of high level data so don’t be surprised if you don’t see a consistent approach.