Journal of Anesthesia and Surgery | Volume 7 | Issue 1 | 2020-05-09

The impact of cardiac disease and surgery on liver function

Nabil Abdelraouf

Abstract

Liver diseases are common health problem in developing countries. There is a great impact of cardiac diseases and surgery on liver performance. High venous pressures and low cardiac output and hypotension associated with cardiac surgery cause impairment of liver function or even cellular damage. During cardiac surgery, cardiopulmonary bypass initiates inflammatory and hemolytic reactions as well as vasoconstriction in vascular bed that results in impairment of liver function after cardiac surgery. Different strategies are employed to minimize liver infection after cardiac surgery but no one proved to be fully protective.

Keywords: Cardiac disease, Liver infection, CPB, Inflammatory Response, Protective Strategy

Full text

Impairment of liver function after cardiac surgery is known as a rare postoperative complication in developed countries [1] . However in developing countries with endemic liver diseases due to bilharziasis or hepatitis C virus, it represents a serious complication. Postoperative liver dysfunction ranges from transient hyperbilirubinemia to frank liver failure. Liver failure occurs in 4% of open cardiac surgery patients and partial injury in 10% [2,3] . The blood flow to the liver is unique due to the dual supply from the portal vein and hepatic artery. The liver receives 25% of the cardiac output. The hepatic artery supplies 20% to 25% and 75-80% from the portal system. The high oxygen extraction ratio of the liver (95%) and dual blood supply make the liver relatively resistant to necrosis from hypoperfusion. This buffer response is affected by the artificial CPB hemodynamics, this supports the theory that the hepatic stasis is more deleterious than the ischemic reperfusion injury [4] . However anesthesia, extracorporeal circulation, surgery techniques, and postoperative cares showed a great advances recently, hyperbilirubinemia incidence is still high following the surgery. According to previous researches, postoperative jaundice after open cardiac surgery is associated with 25% of deaths [5] . Insignificant rise in liver enzymes is common after cardiac surgery, especially with prolonged CPB. Predictive risk factors include Preoperative right-sided heart failure, tricuspid regurgitation, pulmonary hypertension (>45 mmHg), high preload chronic heart failure, NYHA II to IV, and low ejection fraction [6] . Theories Different explanation theories for the mechanism of postoperative liver dysfunction at the cellular level. CPB exudative effect and the systemic inflammatory response syndrome represent a major contribution for postoperative hepatic injury. Perfusion reduction may cause centrilobular sinusoid ischemia and following reperfusion injury. Medications and perioperative hemodynamic instability may result in disturbed liver function tests [7,8] . Heart Failure and Liver Heart failure is usually associated with pulmonary edema, effusion, high central venous pressure, peripheral edema with low cardiac output. Elevated central venous pressure is transmitted to the hepatic venous system and causes hepatic congestion. Decreased cardiac output leads to impaired liver perfusion and subsequent hepatocellular necrosis [9] . Three fundamental classifications of liver failure are metabolic liver disease (amyliodosis, alpha-one antitrypsin deficiency); cholestatic liver disease (primary biliary cirrhosis, sclerosing cholangitis, autoimmune hepatitis); and noncholestatic cirrhosis (viral hepatitis, alcoholic liver disease) [10] . Sever hypotension and hemodynamic instability can lead to ischemic hepatitis, and it is usually associated with left ventricular dysfunction. The compromised hepatic blood flow leads to a consequent hypoxia/anoxia of hepatocytes histologically characterized by the centrilobular necrosis of zone 3 hepatocytes [11] . Amiodarone is well known to be hepatotoxic especially after long-term oral therapy however, liver injury secondary to a parenteral infusion of amiodarone is uncommon. Surprisingly, hepatotoxicity caused by amiodarone is thought to result from the diluent polysorbate 80 and not the amiodarone itself. Theories suggest an allergic or immunologicresponse leading to alterations in the hepatocellular membrane [12] . Angiotensin converting enzyme inhibitors can cause hepatotoxicity which may result in liver failure. The ACE-inhibitor induced hepatotoxicity is usually of cholestatic nature [13] . CPB and Liver CPB is non physiologic circulation and initiates physiological, immunologic, and metabolic changes within the liver. CPB releases catecholamines which reduce hepatic perfusion and blood flow [14] . Two main pathophysiologic mechanisms were recognized for CPB hepatic injury that includes the systemic inflammatory response syndrome and oxidative stress [15,16] . However, most of these pathophysiologic mechanisms are based on centrilobular sinusoid ischemia and following reperfusion injuries. Another mechanism of coagulation factors consumption during CPB leads to reduced coagulation factors and formation of micro thrombi leading to centrilobular hepatic sinusoids [17] . A prolonged CPB pump time (>100 min) has been associated with an elevated LFTs on the second post-operative day14. Unconjugated bilirubinemia results from CPB induced hemolysis, a mechanical valve friction, or transfusion of hemolysed blood. This unconjugated hyperbilirubinemia usually is transient although cholestasis from ischemic injury impairs digestion and predisposes a patient to cholangitis with accelerated hepatic injury [18] . The pump causes contracted arteries and decreased oxygen consumption in hepatic vascular bed resulting in disturbed hepatic blood flow. That leads to a 50%decrease in hepatic blood flow compared to the normal state; reduced blood circulation is more announced during cooling and warming process during CPB [19,20] . Anesthetic medications cause significant damage of liver cells and enzymes during open heart surgery. This can be explained by the oxidative transformation of anesthetics drugs to toxic metabolites. These metabolites increase intracellular calcium concentration and reduce hepatic blood flow during anesthesia lead to liver blood flow changes. The incidence of hepatotoxicity correlates to the catabolized metabolites of anesthesia by cytochrome P450 2E1 to liver proteins that lead to antigens formation which cause antibody mediated immune response. Blood products transfusion, shock, and other stress response are associated with hepatic inflammation and dysfunction [21] . Liver Protection during Cardiac Surgery Intra operative maintenance with volatile anesthetics appears attractive. The availability of variable modern volatile anesthetics, rose the question of which substance is superior to the others [21] . Historically, isoflurane was considered as liverfriendly [22,23] . Even in few case reports of hazardous effects of volatile anesthetics exist, the use of either one of the modern volatile anesthetics appears comparable until further data are available [24] . Near all opioids undergo hepatic metabolism. The administration of fentanyl or sufentanil as a single dose and continuous application of remifentanil seems well tolerated in liver dysfunction [25] . Ischemic pre conditioning, may help to protect the liver with good choice of anesthetic medications [26] . With respect to human data, some studies have found a certain degree of liver protection, but without a clear trend to a specific anesthetic agent. Short-term exposure to sevoflurane or desflurane lowered postoperative liver enzyme release after hepatectomy [27,28] . Shorten CPB time help effectively in reducing the possibility of hepatic injury during cardiac surgery. Meanwhile maintain organ perfusion pressure and MAP around 60 mmHg is also a fundamental factor in liver protection strategy. Perioperative Care Nutrition Perioperative nutritional supply may reduce the short-term hepatic complications. There is a strong relation between nutritional state and postsurgical outcomes with better outcomes. Milk-based and vegetable-derived proteins are preferred. Branched-chain amino acid formula may also be used as a source of protein. Trace elements and vitamins, such as zinc, magnesium, copper, folate, and vitamin B12, are also recommended [29,30] . Fluid and Electrolytes Avoiding hyponatremia with correction of hypokalemia also helps to decrease liver injury after cardiac surgery [31] . Infections Prevention of post-operative infections and appropriate treatment of infections decrease the possibility of liver injury after cardiac surgery. Currently, prophylactic antibiotics are recommended in every cardiac surgery according to antibiotic protocols [32] . Postoperative Pain Relief Using analgesic medications for postoperative pain management which are safe for liver is a great challenge. Morphine and fentanyl are well tolerated. However, the dose and frequency of opiates should be according to the values of LFT. Patients should be carefully monitored for signs of sedation and encephalopathy, and opioid-induced constipation should be avoided with the use of laxatives [33] . The use of acetaminophen is not contraindicated, but it should be used with caution, and recommended dose is 2 to 3 g/day. Nonsteroidal anti-inflammatory drugs should be avoided because of their potential nephrotoxicity, gastrointestinal bleeding, and platelet dysfunction [33] . Conclusion Liver can be affected by cardiac diseases as a result of venous congestion, hypotension and low COP. During cardiac surgery, CBP initiates inflammatory and hemolytic reactions that cause injury to the Liver. Shorten CPB period with maintain of hepatic perfusion pressure, use hepatic safe medications and those with known hepatic protective effect may reduce the degree of hepatic injury after open cardiac surgery using CPB. References 1. 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