TIPS can cause portopulmonary hypertension

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The association between pulmonary hypertension (PH) and chronic liver disease is well recognized. Portopulmonary hypertension (PPHTN) is a progressive pulmonary vascular disease that occurs in the setting of portal hypertension and is characterized by an elevated mean PAP (mPAP) greater than 20 mm Hg, pulmonary vascular resistance (PVR) greater than 240 dynes/s/cm (or 3 Wood units), and pulmonary artery wedge pressure less than 15 mm Hg. The prevalence of PPHTN ranges from 2% in those with chronic liver disease to 16% in those with end-stage liver disease listed for liver transplant. Although the cause of PPHTN is unknown, numerous theories have been proposed; these include imbalance of vasoconstrictive and vasodilatory mediators, genetic predisposition, thromboembolism from the portal venous system, hyperdynamic pulmonary circulation, and inflammation resulting in vasoconstriction and chronic arterial changes due to endothelial damage. PPHTN is categorized as group 1 pulmonary arterial hypertension (PAH) in the World Health Organization classification and is managed with PAH-specific therapy.

TIPS placement is contraindicated in patients with severe left ventricular dysfunction or severe PH. This patient did not have preexisting PH, although he developed severe hypoxemic respiratory failure owing to acute PH immediately after the TIPS procedure. Creation of a TIPS may critically influence pulmonary circulation. Development of acute PH is due to hemodynamic changes and shunted blood volume, which typically stabilizes over several months. In addition, levels of neurohormonal factors such as endothelin and norepinephrine are elevated in decompensated cirrhosis and can further contribute to the development of PH after a TIPS procedure. The concentration of these substances is hypothesized to be upregulated owing to reduced hepatic clearance and increased secretion after TIPS placement. Authors of case studies have also reported on the transition to, or unmasking of, previously unrecognized PPHTN after TIPS placement.

Although PH is a well-known complication associated with TIPS, the recommendations for treatment are less developed. In view of this, clinicians must extrapolate treatment options from current recommendations for the treatment of PH. Of the choices provided, initiation of inhaled nitric oxide (iNO) is the only therapy that may be beneficial in reducing and stabilizing the elevated pulmonary artery systolic pressure (PASP) and improving oxygenation in this acute setting (choice C is correct). Administration of iNO can be beneficial for patients with PAH, particularly pediatric patients. The vasodilatory and antiproliferative actions of NO make it an attractive tool for pharmacological treatment of PAH, especially in an acute setting in a patient who is critically ill. The pulsed delivery of iNO was shown to be as effective as continuous therapy in reducing mPAP and PVR. This patient's TTE on completion of the TIPS procedure was notable for an enlarged right ventricle and a PASP of 70 mm Hg. These findings were confirmed with a right-sided heart catheterization the results of which showed a right atrial pressure of 5 mm Hg, right ventricular systolic pressure of 88/5 mm Hg, PASP of 88/33 (mPAP of 51 mm Hg), cardiac index of 5.8 L/min/m2, and PVR of 3.7 Wood units. The severity of this patient's PH was surprising given the absence of preexisting PH on the basis of the pre-TIPS TTE. The patient ultimately underwent extubation and later was discharged home on breathing room air. Results of a repeat TTE before discharge showed an elevated PASP of 68 mm Hg, and a TTE 2 months after discharge showed a PASP of 55 mm Hg.

Unlike most forms of PAH, PPHTN can improve with liver transplant. Approximately one-half of patients with PPHTN have posttransplant resolution of PPHTN and are able to discontinue PAH therapy. In the consideration of individuals for liver transplant, PPHTN severity plays an important role in perioperative risk assessment. Because PPHTN can improve with liver transplant, and because waiting list mortality risk is not adequately reflected by an individual's model for end-stage liver disease (MELD) score, selected patients with PPHTN can qualify for a MELD exception with a higher priority transplant waiting list. According to the most recent MELD exception criteria, mPAP must be less than 35 mm Hg after PAH-specific therapy to qualify for a PPHTN MELD exception. Severe PPHTN is considered a contraindication to liver transplant, given increased perioperative mortality risk. Although liver transplant has a role in the treatment of patients with PPHTN, it is not a viable therapeutic option in patients who are acutely hypoxemic who develop severe PH after undergoing TIPS placement (choice A is incorrect).

Initiation of heparin infusion for presumptive acute pulmonary embolism in this setting is not only not indicated because such a diagnosis has not been confirmed, but, even if confirmed, it would pose an unacceptably high risk of hemorrhage in a patient with massive variceal hemorrhage (choice B is incorrect). Applied PEEP, usually at levels of 5 cm H2O or greater, are indicated in most patients with ARDS and other types of hypoxemic respiratory failure. This patient's hypoxemia was secondary to the development of PH after TIPS placement; therefore, applied PEEP would have a limited role improving his oxygenation and may further impair right ventricular function (choice D is incorrect).1

Footnotes

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