Liver Anesthesia Considerations

Liver Pathophysiology

  • Location: The liver is situated in the RUQ of the abdomen, located between ribs 7-11 along the right mid-axillary line.

  • Structure: The liver is divided into four lobes, and these lobes contain lobules that radiate around central veins. The function of lobules is to filter blood and ultimately empty the filtered blood into the inferior vena cava.

  • Bile Conjugation: The liver conjugates bilirubin from the spleen and empties it via the intestines.

  • Filtration and Breakdown Mechanics: The liver filters and breaks down bacteria through Kupffer cells, which are specialized macrophages, and this waste empties into the lymphatic system.

  • Metabolic Functions:

    • The liver regulates glucose production, storage, and protein synthesis.

    • It is the primary site for insulin clearance

    • It also serves as the site of first-pass metabolism, wherein enzymes metabolize medications, limiting their bioavailability before they enter the systemic circulation. This first-pass effect can impact drug tolerance, leading to both increases and decreases in drug metabolism.

Assessment of Liver Function

  • Key Assessment Parameters:

    • Ammonia levels: Used to assess hepatic function and metabolism.

    • Albumin levels: Indicates overall liver function and protein synthesis capability.

    • AST (Aspartate Aminotransferase) and ALT (Alanine Aminotransferase) levels: Enzymes indicating liver inflammation or damage.

    • Bilirubin levels: Important for assessing liver’s ability to conjugate and excrete bilirubin.

    • Prothrombin Time (PT): Evaluates the liver’s ability to produce coagulation factors, essential for blood clotting.

Causes of Liver Disease

  • Etiological Factors:

    • Viral Hepatitis

    • Alcohol (ETOH) Abuse

    • Medication/Drug Reactions or Overdose

    • Chronic Hepatitis

  • Signs and Symptoms:

    • Jaundice

    • Ascites

    • Petechiae: Small red or purple spots on the body, indicating bleeding.

    • RUQ Pain

    • Fever and Malaise

    • Nausea/Vomiting

    • Altered Mental Status: Related to hepatic encephalopathy or other metabolic disturbances.

    • Dependent Edema

    • Decreased Urinary Output:.

MELD Score

  • Definition:

    • The MELD (Model for End-Stage Liver Disease) Score is used to assess the severity of chronic liver disease. Its primary purpose is to prioritize patients waiting for a liver transplant—the higher the score, the higher the patient's priority on the transplant list.

      • Based on 90-day survival probability of patients with chronic liver disease

  • Calculation:
    MELDScore=(Serum Bilirubin)+(Serum Creatinine)+(PT)MELD Score = (Serum\,Bilirubin) + (Serum\,Creatinine) + (PT)

  • Scoring:

    • >40 score = 71% mortality

    • 30-39 score = 52% mortality

    • 20-29 score = 20% mortality

    • 10-19 score = 6% mortality

    • <9 score = 2% mortality

Anesthetic Planning for Patients with Liver Disease

  • Considerations: Patients with liver disease have an increased risk for morbidity; elective surgeries should be postponed until patients are hemodynamically stable and any acute complications are resolved.

  • Effects of Anesthesia on Liver:

    • General Anesthesia:

      • It decreases hepatic blood flow by 30-50%.

      • First-line agents recommended: Isoflurane or Sevoflurane.

    • Regional Anesthesia:

      • Can lead to hypotension as it affects the sympathetic nervous system, potentially decreasing blood flow to the liver.

    • Mechanical Ventilation:

      • Increases abdominal pressure, potentially decreasing cardiac output and hepatic blood flow.

  • **Utilize large bore IV, central lines, or invasive hemodynamic monitoring to maintain arterial blood pressure (BP) and cardiac output (CO).

  • Coagulopathy may contraindicate the use of nerve blocks due to increased risk of bleeding.

  • Caution with Opioids: It is advised to use opioids very cautiously in patients with compromised liver function to avoid complications.

  • Pre-operative Sedation: Avoid pre-operative sedation in patients with liver dysfunction due to potential risks of respiratory depression and hemodynamic instability.