Anesthesia and the HepatoBiliary System

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Anesthesia and the HepatoBiliary System

• Courtesy of
• Gurdip Bhatia, MD
• Charles E. Smith, MD
• MetroHealth Medical Center
• Case Western Reserve University
• Cleveland, Ohio

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Objectives

• Hepatic Physiology
• Mechanisms of Hepatocellular Injury
• Acute Parenchymal Liver Disease
• Assessment of Liver Function
• Preoperative Considerations
• Intraoperative Considerations

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Objectives

• Chronic Parenchymal Liver Disease
• Preoperative Considerations
• Intraoperative Considerations
• Postoperative Liver Dysfunction
• Anesthetic Considerations

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Hepatic Physiology

• Liver Blood Flow
• 25 of Cardiac output
• Hepatic artery 25 of blood flow
• Portal vein 75 of blood flow
• Hepatic Veins empty into the inferior vena cava

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Splanchnic Circulation Fig 17.1
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Hepatic Microcirculation

• Portal Axis consists of a terminal portal venule,
  a hepatic arteriole and a bile ductule
• Liver Acinus functional microvascular unit
• Zone 1- rich in Oxygen, mitochondria
• Oxidative metabolism, synthesis of glycogen
• Zone 2- transition
• Zone 3- lowest in Oxygen, anaerobic metabolism,
  Cytochrome P-450
• Biotransformation of drugs, chemicals, and toxins
• Most sensitive to damage due to ischemia,
  hypoxia, congestion

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Microvascular Structure Fig 17.3
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Regulation of Liver Blood Flow

• Intrinsic Regulation
• Autoregulation
• Metabolic control
• Hepatic Arterial Buffer Response
• Decreases in portal blood flow causes increased
  hepatic arterial blood flow
• Extrinsic Regulation
• Neural Control
• Hormones
• Effects of Anesthesia

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Regulation of Liver Blood Flow

• Individual anesthetics
• Isoflurane and Sevoflurane preserve Hepatic blood
  flow
• Upper Abdominal Surgery
• Hepatic blood flow reduced by 60
• Regional Subarachnoid Block of T4
• Reduces 20 of Hepatic blood flow

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Functions of the Liver - I

• Metabolic
• Protein Albumin major protein, Coagulation
  factors except Factor VIII
• Carbohydrates Glucose homeostasis via
  gluconeogenesis and glycogenolysis
• Lipids Degraded to Acetylcoenzyme, a key
  molecule in synthesis of ATP, Cholesterol and
  Phospholipids

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Functions of the Liver-II

• Bilirubin conjugation and secretion
• Bile formation
• Hematologic function
• Hematopoiesis 9th to 24th week gestation
• Clears Fibrin Degradation Products and Lactate
• Important in shock and massive blood loss and
  transfusion

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Functions of the Liver-III

• Humoral function
• Insulin degraded 50 in the first pass
• T4 to T3 conversion
• Aldosterone, estrogen, androgen, ADH all are
  inactivated by the liver
• Liver disease thus, results in endocrine
  abnormalities
• Immunologic function
• Kupffer cells phagocytose antigens

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Functions of the Liver-IV

• Drug Biotransformation
• Make drugs more polar for efficient elimination
• Phase I Reaction
• Cytochrome P450 system
• Oxidation/reduction
• Mixed Function Oxidases
• Phase II Reaction
• Conjugation most commonly catalyzed by
  UDP-glucuronyl transferase

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Factors Affecting Hepatic Drug Metabolism

• Drugs with high extraction ratio are affected
  more by changes in HBF
• Propranolol, Lidocaine, Meperedine
• Poorly extracted drugs are more sensitive to
  intrinsic ability of the liver to eliminate a
  drug
• Diazepam, Phenytoin, Coumadin
• Anesthesia
• Ketamine induces its own metabolism, therefore
  rapid tolerance can occur

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Evaluation of Liver Function

• Laboratory Tests
• ALT, AST, Alkaline phosphatase with
  5-nucleotidase
• Serum Albumin, Gamma-globulin
• PT (best estimate of hepatic function)
• Antinuclear Antibody
• Chronic Active Hepatitis 75
• Antimitochondrial antibody
• Primary biliary cirrhosis 100
• Radiologic Techniques
• Cholangiography, Radionuclide and Ultra sound

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Acute Viral Hepatitis

• Postpone elective surgery
• High mortality and morbidity
• Acute encephalopathy, avoid premed sedatives
• Frequent blood glucose monitoring for
  hypoglycemia
• Correction of Coagulopathy with Vit K, FFP and
  platelet transfusion

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Algorithm for Abnormal Transaminase levels fig
54-1A
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Algorithm for Abnormal Transaminase levels fig
54-1B
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Algorithm for Abnormal Transaminase levels fig
54-1C
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Chronic Liver Diseaseor Cirrhosis PreOp
considerations

• Portal hypertension may lead to GI hemorrhage
• Rx Fluid resuscitation
• Must be done carefully to avoid rebleeding of
  varices
• Vasopressin and Octreotide constrict splanchnic
  arteriolar bed

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Chronic Liver Disease PreOp

• Ascites is due to portal hypertension and sodium
  retention that occurs with cirrhosis
• Rx with Sodium and water restriction and
  diuretics
• Diuretics
• Cause hyponatremia and hyperkalemia
• Check and correct electrolytes

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Chronic Liver Disease /PreOp

• Paracentesis of Ascites
• Not exceed 1 Liter/day for a daily weight loss of
  0.5 to 1.0 kg
• 1 liter of ascites fluid contains 10 grams of
  Albumin
• Each liter of ascites removed must be replaced by
  50 ml of 25 Albumin

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Chronic Liver Disease /PreOp

• Hepatorenal syndrome can be precipitated
• By aggressive paracentesis, potent diuretics like
  Zaroxolyn
• Avoid aminoglycosides (contraindicated), NSAIDS,
  renal contrast, volume depletion
• Hepatic Encephalopathy
• Dysarthria, flapping tremor, hyperreflexia
• Avoid long acting benzodiazepines, high dose
  opiates and diuretics

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Chronic Liver Disease /PreOp

• Child-Turcotte-Pugh Classification
• Lab and clinical criteria to predict operative
  survival in patients with Cirrhosis
• Class C, Surgical risk of Mortality rate 50
• Serum bilirubin gt 3 mg/dl
• Albumin lt 3 g/dl
• PT gt 6 sec of control
• Ascites uncontrolled, encephalopathy advanced,
  nutrition poor

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Chronic Liver Disease /IntraOp

• Optimum drugs or techniques are unknown
• Avoid or reduce dose of drugs excreted via the
  liver such as Lidocaine, Meperidine, Morphine
• Succinylcholine acceptable, effects are not
  prolonged significantly
• NDMB may have prolonged duration of action
• Atracurium may be better as it is eliminated by
  Hoffman elimination
• Vecuronium lt 0.6 mg/kg, Atracurium lt 0.15 mg/kg
• Avoid Pancuronium

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Chronic Liver Disease/IntraOp

• Most IV induction agents are metabolized by the
  liver but recovery depends on redistribution.
  Safe to use Propofol, Thiopental
• For Inhalational agents, Isoflurane and
  Sevoflurane are better than Halothane as Hepatic
  Blood Flow is decreased to a lesser degree
• Fentanyl and Sufentanil single dose bolus does
  not change elimination half life
• Remifentanil is a safer choice as it is degraded
  by tissue and RBC Esterases

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Chronic Liver Disease/IntraOp

• Laparotomy with Abdominal Paracentesis of Ascites
  
• Maintain Intravascular volume,
• Rx with Albumin
• Patients with GI hemorrhage
• Receiving blood products may have decreased
  clearance of Citrate which can lead to
  hypocalcemia
• Bleeding diathesis
• Rx with FFP or Prothrombin complex to correct PT
  within 3 secs of normal
• Transfuse if platelets lt 100,000/uL, Rx with
  DDAVP

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PostOp Complications

• Reversible minor changes are common
• PostOp Jaundice may be due to hemolysis of
  transfused blood
• Shock Liver syndrome can occur if prolonged
  hypotension persisted
• Marked by severe hepato-cellular necrosis
• SerumTransaminases levels increased gt 10 fold
• Bleeding, Sepsis, Renal failure

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Summary-I

• Liver functions include
• Protein synthesis
• Drugs, fat and hormone metabolism
• Immunologic function
• Bilirubin formation and excretion
• Glucose homeostasis

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Summary-II

• For Acute Hepatitis
• Postpone all elective procedures as the
  mortality rate is very high
• For unexpected high Transaminase levels
• Repeat LFTs, if stable or decreasing may proceed
  with surgery
• Otherwise GI consult should be obtained

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Summary-III

• In Chronic Liver disease pre-op issues include
• GI hemorrhage
• Ascites, electrolyte imbalances
• Hypoglycemia,
• Coagulopathy and bleeding disorder

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Summary-IV

• In Chronic liver disease intra-operatively
• Avoid or reduce drugs that are eliminated by
  liver
• IV inductions agents are considered safe
• Inhalational agents
• Use Isoflurane, avoid Halothane
• Avoid Sevoflurane if risk of Hepato-Renal
  Syndrome
• Muscle Relaxants all are acceptable
• Vecuronium and Rocuronium have increased duration
  of action

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Summary-V

• In Chronic liver disease intra-operatively
• Opioids can be used
• Maintain Intravascular volume
• Consider replacing 50 mL of 25 Albumin for
  each liter of ascites fluid removed
• Blood products can cause hypocalcemia and Calcium
  need to be replaced

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Summary-VI

• Post-Op Liver dysfunctions
• Reversible minor changes are common
• Post op Jaundice may be due to hemolysis, but
  other causes should be sought
• Shock Liver syndrome presented by hepatocellular
  necrosis can occur due to prolonged hypotension

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References

• Anesthesia, Fifth Edition/ Ronald D. Miller,
  Hepatic Physiology, Chapter 17 Anesthesia and
  the Hepatobiliary System, Chapter 54.
• Anesthesia and Co-Existing Disease, Fourth
  Edition/ Robert K Stoelting, Stephen F. Dierdorf,
  Diseases of the Liver and Biliary Tract, Chapter
  18.
• Clinical Anesthesia, Fourth Edition/ Paul G.
  Barash, et.al., Anesthesia and the Liver, Chapter
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