Hepatopulmonary Syndrome And Porto Pulmonary Hypertension

Liver pathology has a secondary effect on the lungs. Type 1 hypoxemic respiratory failure (HPS). A higher oxygen gradient in the alveolar arterial system.  Is brought on by pulmonary vasodilation when portal hypertension (non-cirrhotic portal hypertension) or liver disease (ALF) are present.  The pulmonary vasculature's development of vascular shunts.

Diagnostic criteria

• Hypoxia: Alveolar arterial oxygen gradient >15 mmHg or PaO2 <80 mmHg. The patient ought to be seated. The patient need to be breathing in room or surrounding air. Vasodilation of the heart.  Gold standard: Bubble contrast echo or contrast enhanced Echo cardiogram (agitated saline). A radioactive lung perfusion scan with a brain shunt greater than 6% utilizing radiolabeled albumin, .
• Hepatic illness 
• Hypertension in the portals 

Severity Assessment Of HPS

A. On Room air and the patient is in a sitting posture.

Hypoxia (PaO2 FiO2 ratio) determines the following: mild, moderate, severe, >50 and <60 mmHg, >15 mmHg, <50 mmHg,

B.  On 100% FiO2

 Extremely severe; individuals with FiO2 inhaling 100% oxygen had a PaO2 of less than 300 mmHg.

Pathophysiology 

A. CLD or Portal hypertension 

An increase in the liver's synthesis of endothelin 1.  This will affect the pulmonary endothelium's Endothelin 1B receptors.  Increased expression of eNOS (endothelin Nitric oxide synthase)  Increased synthesis of no. The dilatation of the pulmonary blood vessels.

B. Translocation of gut microbiota and Endotoxemia

Equally significant. Modifications to the microbiota in the gut that enter the bloodstream. Enter the lungs and reach the right ventricles. An increase in the lung's macrophage and monocyte accumulation
Higher VEGF α expression → Angiogenesis → Formation of shunts.
TNF alpha plays a significant part. Increased heme oxygenase activation leads to heme breakdown, which increases carbon monoxide. Both NO and CO cause pulmonary vasodilation. Increased expression of Inducible NOS and NO.

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Pathophysiology of HPS

Pulmonary capillary diameter dilation: o Normal: 8–15 mm; o HPS: >15–500 mm;  Vasodilation reduces the transit time through capillaries.
Because angiogenesis shunts blood directly to the left side of the heart, it hinders some blood flow to alveoli.  As a result, the alveolar arterial oxygen gradient rises. Dyspnea is a result of hypoxemia.  No PND (left heart disease) or orthopnea.  No coronary artery disease.

One is dyspnea from exercise.  Dyspnea during rest;  Pneumopnea in opposition to orthopnea;  Regaining upright posture after a reclined position.  The diaphragm is raised.  Reduced lung enlargement.  There is a partial collapse of my lungs.  The recumbent position results in less aeration. 

There is a V/Q match when alveolar air entry reduces, but there is already impaired or exacerbated ventilation perfusion mismatch when there is decreased alveolar ventilation.  Ventilation-perfusion mismatch is observed in upright position. Hypoxia is partially corrected and breathlessness is not observed.

Etiology 

Most prevalent: Hepatic cirrhosis accompanied by portal hypertension.
Hypertension in non-cirrhotic portals.  Uncommon: Severe liver failure. 

Clinical Features

Dyspnea , Platypnea (standing up from a recumbent position),
Orthodeoxia (measure the hypoxia level).  Upon transitioning from a recumbent position to an upright one, PaO2 drops by more than 5% or 4 mmHg.  Results pointing to Wilson's illness and liver disease
Hemochromatosis patients with bronze skin pigmentation.

Diagnosis Of Hps

Most typical: Test for screening: pulse oximetry  Alveolar arterial oxygen gradient; BCG; PaO2; Confirmatory (Gold standard) test; Bubble contrast echo; On room air SpO2 <96% (sitting)  Use a 3-way cannula to inject the patient with agitated saline:  During peripheral administration, microbubbles enter the superior vena cava, travel to the right side of the heart, and are absorbed there.  Nine milliliters of saline and one milliliter of air.  Agitated saline creates microbubbles inside saline when they are more than >10 micrometer in diameter. 

In the left atrium, bubbles normally do not enter. After injection, bubbles in pulmonary vasodilation and shunts arrive in the left atrium four to six cardiac cycles later.  As an alternative: Scan for radio-albumin lung perfusion Over 6% of brain shunts.  Much earlier entry of bubbles into the left side of the heart is possible in cases of interatrial or ventricular septal defects.  <3 Intracardiac shunting is indicated by cardiac cycles.
Intrapulmonary shunting in cardiac cycles 4-6.

Q. Which is better: Transesophageal echo or Transthoracic echo in patients with HPS? 

Ans. Transthoracic echo is better. TEE is theoretically accepted, but practically dangerous .

Management Of Hps

HPS is an extremely lethal illness.  Supplementing with oxygen;  Liver transplantation is advantageous.  Decreases death rates.  Increasing QOL;  Increasing survival rate;  Significant and mostly reversible improvement in symptoms  There are no known advantages to drugs. 

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Porto Pulmonary Hypertension

Pulmonary hypertension based on Mean PAP: >20 mmHg in presence of Portal hypertension. 

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Pathophysiology

Increased Endothelin 1 synthesis from portal hypertension results in pulmonary vasoconstriction. Hypertension is brought on by an increase in pulmonary arterial pressure. Right ventricular failure and hypertension are brought on by POPH.

Clinical Features

No prototypnea; dyspnea; right heart failure 

Management Of Porto Pulmonary Hypertension

Vasodilator; inhaled epoprostenol; potential health benefits of oxygen.
Liver transplantation might be advantageous. 

Hope you found this blog helpful for your NEET SS Pulmonology Preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.