Liver Anesthesia Considerations Study Guide PDF

- Pre Op Assessment - Risk factor assessment: alcohol and/or illicit drug use, herbal medication use, transfusion history, tattoos, sexual promiscuity, consumption of raw seafood, travel to endemic areas - "looking to diagnose, don't ask your patients all of...

- Pre Op Assessment - Risk factor assessment: alcohol and/or illicit drug use, herbal medication use, transfusion history, tattoos, sexual promiscuity, consumption of raw seafood, travel to endemic areas - "looking to diagnose, don't ask your patients all of this" - Signs & Symptoms: jaundice, fatigue, anorexia, weight loss, N/V, easy bruising, dark-colored urine, biliary colic, abdominal distention, GI bleeding, loss of appetite, fatigue, malaise, difficulty sleeping, subtle cognitive changes, pruritus, easy bruising, changes in color of urine or stool - "this is what you should look for if you know your pt has liver dx" - Physical Exam Findings: Jaundice, Scleral Icterus, Ascites, Spider Angiomas, Xanthelasma, Asterixis, Palmar Erythema - Spider Angiomas: vascular lesions just beneath the skin that result from abnormal dilatation of vasculature - Isolated ones are benign, but multiple ones are characteristic of chronic liver disease (95% specificity) - Also suggest a high likelihood of varices and HPS - Xanthelasma: sharply demarcated yellowish cholesterol deposits under the skin - Considered an ocular manifestation of liver disease - Believed to be due to inflammation - Asterixis: floppy hands or "liver flap" or "hepatic flap" - Lab values: Routine screening LFTs not indicated, Avoid testing in asymptomatic patients - Preop LFTs: - Elevated ALT and AST in asymptomatic patient: proceed if \< 2x normal and normal alk phos, bilirubin, INR - Transaminases \> 2x normal → workup prior to elective surgery (US, CT, liver biopsy) - Both transaminases and INR abnormal → workup prior to elective surgery (US, CT, liver biopsy) - Elevated alk phos and elevated transaminases → suspect biliary disease and workup indicated - Child-Pugh Risk Assessment - "only know what it is, not specifics" - Scoring criteria to assess the severity of liver disease - Based on 5 factors: encephalopathy, ascites, bilirubin, albumin, and INR - Patients can be scored an A, B, or C (C being the worst) - MELD: Model for End-Stage Liver Disease - "just know it's objective, and that it doesn't include the cause of liver disease" - Creatinine, Bilirubin, INR, and Sodium - now whether they're on dialysis or not is included as well - Used to predict 3 month survival in liver disease patients - used to allocated transplants - Optimize Preoperative Status - Least invasive surgical options are preferred! - "the more you're in the abdomen the more you affect your bf to the liver" - Optimize nutritional, renal and cardiac function - Treat ascites - Optimize albumin levels - Correct coagulation and electrolyte disturbances - Treat encephalopathy (lactulose and oral antibiotics) - Maintain cardiac output (to maintain hepatic blood flow!) - Be vigilant for alcohol withdrawal in patients with alcoholic liver disease - Perioperative Management - Altered Pharmacokinetic Considerations - Altered protein binding - reduced albumin levels and other drug-binding proteins - Altered volume of distribution associated with ascites and increased TBW - Reduced metabolism - "decreases doses of systemic medications" - Potentiation of anticoagulants (decreased production of clotting factors) - Altered drug elimination - Altered enzymatic activity - Altered hepatic extraction - Low albumin - Impaired oxidative metabolism - Conjugation relatively unaffected - Biliary excretion depends on degree of intrahepatic shunting - Overall: decrease the doses (50%) in systemic meds - Patients with liver disease commonly have an increased volume of distribution, necessitating an increase in initial dose - However, because the drug metabolism may be reduced, smaller doses are subsequently administered at longer intervals - General - Induction of General Anesthesia - Monitoring (AL, PAC, TEE, TEG or thromboelastography) - Thromboelastography (TEG): evaluating actual function not just specific levels of individual factors - Anticipate increased aspiration risk, rapid desaturation and hypoxemia - preoxygenate and RSI - Propofol, Etomidate and Midazolam do not alter hepatic artery perfusion when given for short procedures - Anticipate increased susceptibility to CNS-depressant effects. - Prolonged infusions of propofol have been associated with (rare) syndrome of lactic acidosis, lipemia, rhabdomyolysis, hyperkalemia, cardiac failure and death - Increased susceptibility to CNS-depressant effects - Induction Agents - Methohexital / Ketamine / Etomidate / Propofol: - Highly lipid-soluble and high hepatic extraction ratios → expect decreased clearance in liver disease - BUT clearance is mostly unaltered in cirrhosis - Increased VD may prolong elimination - Recovery times after propofol infusion in cirrhotic patients may be prolonged - Dexmedetomidine - Liver metabolism primarily with little renal clearance - Decreased clearance and prolonged half-life - Midazolam - Reduced clearance prolongs elimination half-life - Infusion is a bad choice due to prolonged elimination - Benzodiazepines are metabolized in the liver by microsomal oxidation and glucuronidation - Should be used with caution in the elderly - "Use extreme caution in these patients as well" - The potency, onset, and duration of action of benzodiazepines depend on their lipid solubility - Lorazepam undergoes phase II glucuronidation - normal metabolism with liver disease - Propofol, ketamine, and etomidate - high hepatic extraction ratio, pharmacokinetics are unchanged in mild-mod cirrhosis - Although pseudocholinesterase levels are decreased in patients with liver disease, the clinical prolongation of succinylcholine is not significant - still avoid if patient is hyperkalemic - Maintenance of General Anesthesia - Monitoring and IV access - depends on preexisting disease, surgical procedure - Maintain cardiac output and hepatic blood flow - Avoid hypocapnia - Hematologic considerations - perioperative bleeding - Meticulous fluid management (albumin!) - Avoid hypothermia - "increase workload on the heart" - Increased susceptibility to CNS-depressant effects - Nitrous oxide - appears ok as long as not used in the setting of impaired hepatic oxygenation - Vitamin K? Do they need vitamin k administration to help improve their clotting factors? - Platelets? Goal \> 50k - Fibrinogen? - Opioids - "over all cautious dosing, risk of prolonged effect" - Morphine: prolonged half-life in advanced liver disease; exaggerated sedative effects, resp. depression - Meperidine: reduced clearance, half-life is doubled, reduced clearance of normeperidine (active metabolite) - Hydromorphone: prolonged half-life, exaggerated sedative effects and respiratory depression - Fentanyl: Good choice for patients with hepatic disease, elimination not significantly altered in cirrhosis - High lipid solubility with short duration of action; repeated dosing/ infusion may see prolonged effects - Sufentanil: high lipophilicity, highly protein-bound, extensively metabolized by liver, pharmacokinetics not appreciably altered in cirrhosis - Alfentanil: higher free fractions in cirrhosis can prolong action and exaggerate effects - Clearance unaffected by hepatic function - Remifentanil: Ester linkage; metabolism by hydrolysis (tissue and blood esterases), unaffected by hepatic function - Remember to dose long-acting drugs prior to discontinuation of infusion - Antibiotics are low extraction drugs (not affected by hepatic blood flow) - may be affected by decreased protein binding - Additional Considerations: - Maintain hepatic blood flow - Anything that decreases CO will decrease hepatic blood flow - Not just meds and low bp → think PPV, high airway pressure, insufflation, positioning (steep t-berg) - VAs: Decrease MAP = decrease portal blood flow → MAINTAIN MAP! \*\* "was an issue last semester" - assuming this means its a test question\*\* - ISO may actually increase HA blood flow and is preferred vs. Sevo? - Induction agents: Propofol, Thiopental, Etomidate, Methohexital do NOT adversely affect the liver beyond decreased HBF - Benzodiazepines: Prolonged ½ life; reduce dosages! - NMBAs: Prolonged DOA with vecuronium and rocuronium- monitor TOF - Succinylcholine DOA may be prolonged due to decreased plasma cholinesterase (earlier in her notes she says it's not enough to care) - Vec and roc may be prolonged with extrahepatic biliary obstruction - Opioids: Morphine, Meperidine, Alfentanil metabolism is decreased - Effects can be prolonged and contribute to post op respiratory depression - Vasopressors: Reduced responsiveness to pressors and catecholamines - Extraction ratio is the amount of drug that is eliminated during a single pass through the liver. - If no drug is eliminated on the first pass, the extraction ratio is 0 - If all of the drug is eliminated on the first pass, extraction rate is 1 - What factors do you think determine the hepatic extraction ratio? - Hepatic blood flow, Fraction of unbound (free) drug, and ability of hepatocytes to metabolize a drug - Drugs with high extraction ratios are rapidly cleared and **clearance is highly dependent on hepatic blood flow** (Propofol, Fentanyl, Morphine, Labetalol, Propranolol) → reduce dose but not frequency - Neuraxial - May be contraindicated due to existing coagulopathy and/or thrombocytopenia - Reduce doses in advanced liver disease - Epidural anesthesia can be used in lower abdominal and limb surgeries - Avoid hypotension - need to maintain hepatic perfusion - Avoid high neuraxial block (T-5) - associated with decreased hepatic blood flow - Peripheral Nerve Blockade - No negative effects on HBF or liver function - Remember some LAs are metabolized by the liver - Esters - hydrolysis by pseudocholinesterase in plasma - Amides - biotransformation in the liver - Procedural Considerations - **Liver biopsy** is the method of choice to determine whether liver damage is due to necrosis, inflammation, steatosis, or fibrosis - Coagulopathy or thrombocytopenia contraindicates percutaneous liver biopsy - TIPS: Transjugular Intrahepatic Portosystemic Shunt Procedure - [she read the name like 3x so idk what that means] - Interventional encephalopathy procedure - Hepatic vein is accessed via internal jugular vein and shunt is placed between hepatic vein and portal vein (bypasses liver) - Used primarily to treat bleeding esophageal varices and refractory ascites - Risks: hemoperitoneum, inadvertent formation of shunt between hepatic artery or bile ducts and portal vein, worsening encephalopathy - Dr. Schlesinger's Notes: - TIPS is done for patients with ascites and esophageal varices - SHUNT PLACED to bypass the liver (portal vein to hepatic vein) - Hepatic Resection - Major hepatectomy : resection of 3 or more segments - Complications: - Bleeding - Vasopressors can decrease blood loss (by decreasing splanchnic pressure) - Portal triad clamping of afferent vessels - Total vascular occlusion (portal triad plus IVC) - Ischemic preconditioning (occlusion, reperfusion, clamping) - Air Embolism - Increased risk if tumor is near vena cava or involves portal vessels - Postop: Pleural Effusions, Biliary leakage, Wound dehiscence, Ascites, Abdominal abscess - Alcoholism and Anesthesia - Malnutrition and dehydration - Decreased resistance to infection, delayed wound healing - Liver Damage: Monitor labs to assess severity, use scoring systems - Pulmonary Complications: many alcohol abusers also smoke, may have COPD or HPS - Cardiomyopathy: arrhythmias common - Renal disease: may have glomerulonephritis or HRS - Neurological disease: neuropathy, DTs, or acute intoxication - **Cross tolerance to medications is common!** - Benzodiazepines and other sedatives stimulate the same receptors as many of our anesthetics - Patients with ESLD may be more sensitive to our medications if the liver is not able to eliminate the medication - Chronic alcoholics may have cardiomyopathy and dysrhythmias, may be predisposed to aspiration, and may have diminished pulmonary function - They may have impaired synthetic liver function - important screening tests are albumin and prothrombin time - Alcohol withdrawal may cause seizures - "may start as tachycardia then lead to seizures" - Acute ETOH Intoxication - Acutely intoxicated - Decreased MAC - Aspiration d/t decreased gastric emptying and decreased LES tone - Alcoholic (not acutely intoxicated) - Increased MAC - Alcohol withdrawal syndrome - Tachycardia, agitation, increased SNS tone 48-72 hours after last alcohol intake - Tremulousness and hallucinations, hyperpyrexia, cardiac dysrhythmias - grand mal seizures - Severe withdrawal (Delirium Tremens) is a medical emergency - Porphyrias - Rare genetic aberrations in heme production - Heme production required 8 different enzymes - genetic deficiency in one of these results in porphyria - Accumulation of porphyrins in tissues leads to porphyrias - Due to a buildup of naturally occurring chemicals that are necessary for the function of hemoglobin - Acute Intermittent Porphyria: - Incidence: 1:10,1000 in general population (most common) - S&S: recurrent serious neurologic reactions, abdominal pain, dark urine, HTN - Can be life-threatening - Triggers: barbiturates, sex hormones, glucocorticoids, cigarettes, other meds (ketorolac, phenytoin, birth control pills, sulfonamides, benzodiazepines (possibly), ketamine (possibly)) - Cutaneous Porphyria: porphyrins build up in skin - Symptoms occur skin is exposed to sunlight