Critical Care Medicine
- 1. Description of the problem
2. Emergency Management
- 3. Diagnosis
Special considerations for nursing and allied health professionals.
What's the evidence?
cirrhosis, esophageal varices, gastric varices, splenomegaly, ascites
1. Description of the problem
What every clinician needs to know
Portal vein is formed by the confluence of splenic vein and the superior mesenteric vein that carry blood from the splanchnic circulation to the liver. Normally, it is a low pressure system with the portal pressure gradient (portal vein pressure minus hepatic vein pressure) of less than 5 mm Hg. A rise in pressure in the portal venous system is termed portal hypertension.
The clinical consequences of portal hypertension develop once portal pressure gradient increases to greater than 12 mmg Hg. Portal hypertension generally results from increased vascular resistance. It is termed intrahepatic, post-hepatic and pre-hepatic, depending on the site of vascular resistance.
Portal hypertension could also be categorized as intrahepatic or extrahepatic. Extraheptic causes include portal or splenic vein thrombosis (also pre-hepatic) and hepatic vein thrombosis (also post-hepatic). Intrahepatic portal hypertension is classified as pre-sinusoidal (schistosomiasis, early primary biliary cirrhosis), sinusoidal (alcoholic cirrhosis) and post-sinusoidal (alcoholic hepatitis, veno-occlusive disease). Cirrhosis is the commonest cause of portal hypertension.
Portal hypertension could be silent and remain undetected for prolonged periods. However, the likelihood of clinical problems increases as portal pressure rises.
Most patients develop ascites and lower extremity edema. In some, ascites accumulates in the pleural space, particularly on the right side, resulting in hepatic hydrothorax. Varices may develop in the esophagus and less commonly in the gastric fundus and rectum. Less frequently, ectopic varices may develop in the gastric antrum, duodenum, small bowel and at anastomotic and ileocolostomy sites and in the retroperitoneum.
Esophageal and gastric variceal rupture results in hematemesis and melena, and possible circulatory collapse. Rupture of a retroperitoneal varix may cause severe back pain and hypotension without overt gastrointestinal bleeding. Many patients have palpable splenomegaly with or without a firm, palpable liver.
Abdominal examination may also reveal dilated anterior abdominal wall veins (caput medusae) and an audible venous hum in the epigastrium. An enlarged spleen may cause hypersplenism resulting in thrombocytopenia, leucopenia and/or anemia.
Key management points
Establish the diagnosis of portal hypertension.
Determine the etiology of portal hypertension.
Evaluate the clinical consequences.
Treat complications related to portal hypertension.
Risk assessment for development of possible complications such as variceal bleeding.
2. Emergency Management
Focus on stabilizing the patient.
Emergency measures are required for life threatening complications related to portal hypertension. Principal among them is gastrointestinal bleeding from variceal rupture. Most patients with portal hypertension who present with acute gastrointestinal bleeding have cirrhosis and esophageal varices.
Presenting symptoms are typically hematemesis and melena and those indicative of circulatory collapse. Patients with cirrhosis may develop confusion and poor responsiveness secondary to hepatic encephalopathy.
Assess hemodynamic status and stabilize by rapid infusion of saline and packed red blood cells. Large-bore venous cannulae are needed.
Perform endotracheal intubation if patient is poorly responsive.
Admit to an intensive care unit.
Perform abdominal ultrasound to assess liver morphology and a Doppler study to evaluate patency of the hepatic vessels.
Perform upper gastrointestinal endoscopy for endoscopic management of variceal bleeding.
If variceal bleeding uncontrolled, place a Blakemore tube, inflate the gastric balloon and place it under traction.
If endoscopic treatment ineffective or bleeding from gastric or ectopic varices, arrange transhepatic portosystemic shunt (TIPS) placement; gastric variceal bleeding could be treated with cyanoacrylate injection if available.
Diagnosis is established by a combination of clinical evaluation and laboratory and imaging studies. Ascites and pedal edema are sometimes the earliest manifestations of portal hypertension. Varices are silent until rupture that causes acute gastrointestinal bleeding. More commonly, varices are found on screening upper endoscopy. Laboratory finding of thrombocytopenia also raises the possibility of portal hypertension.
Abdominal imaging with a Doppler ultrasound or CT/MRI scan with intravenous contrast would outline morphology of the liver and hepatic vessels and thus help establish the presence of portal hypertension. Liver biopsy may show cirrhosis or other changes associated with portal hypertension and transjugular portal pressure gradient measurement would directly establish the diagnosis.
Maintain a high index of suspicion in a patient with abdominal distention or upper gastrointestinal bleeding.
Examine patient for signs of cirrhosis (spider angiomas, palmar erythema) and for consequences of portal hypertension (dilated abdominal wall veins, ascites, peripheral edema, splenomegaly).
Perform laboratory, imaging and pathologic studies to establish diagnosis.
What diagnostic tests should be performed?
Laboratory studies including complete blood counts, liver biochemical profile and renal studies; additional studies to determine underlying etiology of portal hypertension.
Abdominal ultrasound to determine liver morphology and evaluate patency of hepatic vessels and direction of flow; CT or MRI scan triphasic with contrast will provide further details of liver, hepatic veins, portal vein and its tributaries, collaterals and spleen.
If ascites is present, ascites albumin level should be determined to measure serum ascites albumin gradient (SAAG); a level greater or equal to 1.1 favors a diagnosis of portal hypertension.
Liver biopsy is generally definitive in establishing a liver specific etiology of portal hypertension; a transjugular liver biopsy has the additional advantage of determining portal pressure gradient
The portal venous system is located between two capillary beds: the splanchnic capillaries and the hepatic sinusoids. Sinusoids are the specialized liver capillaries and they receive blood both from the portal vein and the hepatic artery. The branches of the portal vein and hepatic artery form the portal triad along with the interlobular bile ducts in the portal tracts. The blood flows in the sinusoid from the portal tract to the central hepatic venule.
The endothelial cells that line the sinusoids are fenestrated and are devoid of a basement membrane. The sinusoids therefore have a unique structure with high permeability that allows direct contact between plasma and hepatocyte surface through the space of Disse. The sinusoidal blood drains into the tributaries of the hepatic veins through the terminal hepatic venules, and subsequently into the inferior vena cava and right atrium.
Portal venous system is a low pressure system. The difference between the hepatic vein and portal vein pressure is termed the portal pressure gradient that is normally less than 5 mm Hg. Portal pressure gradient is the effective intrasinusoidal pressure, and clinical consequences develop once the gradient increases to greater than 12 mm Hg.
Like any flow system, pressure (DP) in the portal venous system is determined by two variables based on Ohm’s law: flow (Q) and resistance (R).
DP = Q x R
The portal pressure increases with increased flow and constant resistance or with increased resistance and constant flow or with both. Although the vascular resistance depends on several factors including the viscosity of blood (h) and the length (l) of the blood vessel, it is determined primarily by the radius (r) of the blood vessel.
R = 8hl / pr4
DP = Q x (8hl / pr4)
At constant flows, small changes in vascular radii result in large changes in pressure. An elevation in portal pressure (portal hypertension) is caused by either increased portal blood inflow or by increased resistance to portal blood flow or both. Normally, increases in portal inflow result in minimal or no increases in portal pressure.
For example, portal blood inflow increases post-prandially but without significant increase in portal pressure. This is due to the passive dilation of the intra- and extra-hepatic blood vessels. However, a massive increase in portal blood inflow such as due to a splenic arteriovenous fistula could cause portal hypertension, but this is a rare occurrence.
Cirrhosis is the commonest cause of portal hypertension. Chronic liver disease is the twelfth leading cause of death in the United States according to the Center for Disease Control. In 2007, age-adjusted death rate from liver disease per 100,000 population was noted to be 9.7. About 50% of patients with cirrhosis develop gastroesophageal varices.
The prevalence of varices is higher among patients with more severe liver disease - 85% in Child's C versus 40% in Child's A disease. Varices develop at a rate of 8% per year among cirrhotics without varices. Bleeding from varices occur at a rate of 5% to 15% per year, the highest risk among those with large varices and/or those with advanced Child's B or Child's C disease. Gastric varices develop in 5% to 33% of patients with portal hypertension.
Special considerations for nursing and allied health professionals.
What's the evidence?
Xu, JQ, Kochanek, KD, Murphy, SL, Tejada-Vera, B. "Deaths: Final datafor 2007". National vital statistics reports. vol. vol 58. National Center for Health Statistics. 2010.
Garcia-Tsao, G, Sanyal, AJ, Grace, ND, Carey, W. "Prevention and management of gastroesophageal varices and variceal hemorrhage incirrhosis". Hepatology. vol. 46. pp. 922-38.
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