Postoperative Chylothorax of Unclear Etiology in a Patient with Right-sided Subclavian Central Venous Catheter Placement.

A young male underwent decompressive craniotomy for an intracerebral bleed. A right-sided subclavian central venous catheter was placed in the operating room after induction of anesthesia. Postoperatively, he was shifted to Intensive Care Unit (ICU) for mechanical ventilation due to low Glasgow coma scale. He had an episode of severe agitation and straining on the tracheal tube in the evening same day. On the 2nd postoperative day in ICU, his airway pressures were high, and chest X-ray revealed massive pleural effusion on right side. Under ultrasound guidance, 1400 milky white fluid was aspirated. It was sent for analysis (triglycerides) that confirmed chyle and hence, chylothorax was made as diagnosis. A duplex scan was done which ruled out thrombosis in subclavian vein. The catheter had normal pressure tracing with free aspiration of blood from all ports. Enteral feeding was continued as it is a controversial matter in the literature and he was monitored clinically and radiologically.

INTRODUCTION

Central venous catheterization (CVC) is routinely done in anesthesia and Intensive Care Units (ICUs). A rare complication after CVC is chylothorax. It is defined as the presence of chylomicrons or a triglyceride level of over 1.24 mmol/L in the pleural fluid. Direct trauma and malignancy remain the most common causes of chylothorax in adults, with reported rates of 50% and 30%, respectively. Central vein thrombosis as a cause of chylothorax in adults is uncommon, with only a few cases reported in the literature, which were mainly related to CVC. We are reporting a case regarding postoperative chylothorax of unclear etiology. He had a CVC placement in the right subclavian vein during surgery and right-sided chylothorax was developed on the 2nd postoperative day (POD) in ICU. We have discussed possible causes and management options regarding chylothorax.

CASE REPORT

A 27-year-old male underwent left parietal decompressive craniotomy and duraplasty for a vein of Galen aneurysmal malformation with left parietal intracranial bleeding with hemorrhage into the left lateral ventricle. After induction of anesthesia, a right subclavian CVC was placed under ultrasound guidance. Due to pre-operative low Glasgow coma scale (GCS), he was transferred to ICU for mechanical ventilation.

Chest X-ray (CXR) on arrival in ICU showed correctly placed CVC and bilateral clear lung fields. His feeding was started through a nasogastric tube. There was no change in CXR [Figure 1] on 1st POD. In the evening during transfer for a computed tomography scan brain, he became agitated and started coughing. After that, he remained sedated comfortably. Overnight, his peak airway pressures increased that were unaffected by suctioning of tracheal tube or nebulization with salbutamol and ipratropium bromide. On examination, breath sounds were diminished and percussion note was dull over the right side of the chest. His CXR [Figure 2] on 2nd POD showed massive pleural effusion on right side and mild on left side. Under ultrasound guidance, about 1400 ml of milky white fluid was aspirated [Figure 3]. Soon after drainage, airway pressures returned to baseline. The fluid was sent for analysis which revealed triglyceride levels of 285 mg/dl which correlates with lymphatic fluid (chyle). Microscopy and culture were negative for infection. Duplex ultrasound was negative for thrombosis in both subclavian veins and superior vena cava. There was normal venous pressure tracing from the catheter and free aspiration of blood from all three ports, but as we suspect chylothorax due to CVC, we removed the catheter. We did not came across such type of case, so we looked at the literature for further management. His enteral feeding was continued and he was observed clinically and radiologically (CXR and ultrasound daily). Due to persistent low GCS, he underwent tracheostomy on the 5th POD. He was discharged from ICU on the 7th POD and from hospital on the 11th POD.

Figure 1

Normal chest X-ray on the 1st postoperative day in Intensive Care Unit

Figure 2

Massive pleural effusion seen on chest X-ray at right side

Figure 3

Large amount of milky white fluid aspirated under ultrasound guidance

DISCUSSION

The thoracic duct or the left lymphatic duct is the largest lymphatic in the body which drains into the left subclavian vein at its junction with the internal jugular vein.[1] Its course and anatomy are variable in 50% of cases. The thoracic duct can duplicate and triplicate, with one draining in the usual course and the other draining into the right subclavian vein.[1] The right lymphatic duct is smaller and it drains the right thorax and arm. All the remaining body is drained by the left lymphatic duct. Lymph also called as chyle contains triglycerides, cholesterol, chylomicrons, lymphocytes, etc.

Chylothorax is the pleural effusion of chyle. Its etiology can be classified as traumatic or nontraumatic. Non-traumatic causes are medical conditions such as lymphomas (most common), cirrhosis, and filariasis. Traumatic causes are usually surgical; cardiothoracic and neck surgeries with the highest risk (4%) after esophageal surgery.[2] It is more common on left side. The pathogenesis is thrombosis resulting in occlusion of the duct opening.[3] “Chylothorax when occurs solely from an indwelling catheter, venous thrombosis is usually present” was remarked by authors in 1980s and also repeated in recent reviews.[4] The risk of venous thrombosis after a CVC is reported as 5%-10%.[5] The diagnosis is confirmed if the triglyceride level of aspirated fluid is >110 mg/dl and content of cholesterol is <200 mg/dl, the sensitivity is 0.99 for chylothorax. Triglyceride levels of <50 mg/dl exclude chylothorax.[6] Diagnosis can also be confirmed by electrophoresis.[7]

We believe that chylothorax in our patient was not due to subclavian CVC. First, chylothorax after a catheter is usually considered due to venous thrombosis and there was no thrombosis detected in veins on duplex ultrasound. Second, there was correct venous pressure tracing and free aspiration of blood from all three ports which suggest that the catheter was working perfectly and not dislodged. Third, chylothorax is more commonly reported with left-sided catheters, but in our case, it was a right-sided catheter. Finally, if the catheter is the cause we expect the effusion to be on the catheter side only, although more on the right, it was also on the other side. Another possibility could be direct injury to the duct during catheter placement, but CXR on 1st POD showed no effusion at all and the symptoms of effusion developed acutely in between the 1st and the 2nd POD.

A rare possibility could be patient agitation during transport resulting in a brief period of raised intrathoracic pressure. Spontaneous chylothorax has also been reported in a young male.[8] No effusion on the 1st POD and the occurrence of effusion contralateral to the catheter side point in favor of it. However, the exact cause remains unclear. The milky white color is characteristic of chylothorax, although it resembles propofol and in a unique case report. Puttagunta et al. reported propofol infusion going into the pleural space through a misplaced CVC.[9] In our case, the aspirate was far more than the amount of propofol used (20 ml of 1% propofol).

Treatment is conservative which involves stopping enteral feed (increases chyle production) and starting parenteral feed (directly absorbed into the portal system).[3] There is no consensus about the optimal regime or its duration.[10] Some authors even consider it ineffective because holding enteral feed in ICU patients has its own harmful effects (stress ulcers, gastrointestinal bleeding, atrophy of intestinal mucosa and translocation of bacteria) and for this reason, we continued enteral feeding.[11]

CONCLUSIONS

Chylothorax is a rare complication, especially on right side. Pleural effusion drainage under ultrasound guidance and biochemical analysis of aspirated fluid are key management steps.

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Conflicts of interest

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