Anesthesia and Hepatic Function

1
Anesthesia and Hepatic Function

• Scott F. MacKinnon, M.D.

2
35 yo male with chronic Hep c presents for lumbar
laminectomy
3
66 yo homeless male with extensive etoh abuse
history presents for pelvic exenteration
4
32 yo gravida2 para1 for emergent c-section.
Severe RUQ pain, ALTgt6000
5
Anatomy

• Largest Gland 1.8kg/1.4kg M/F
• Glissons Capsule(except porta hepatis)
• Capsular Peritoneum support
• Lobes vs segments
• Contains 10-15 of TBV

6
(No Transcript)
7
Vascular Supply

• 25 of total CO 120ml/min/100gm
• Hepatic Artery(2550DO2)
• Portal Vein(7550DO2)
• Portal Vein nutrients, multiple tributaries

8
(No Transcript)
9
Regulation of Hepatic Blood Flow

• Dual Supply
• One primarily for oxygenation, substrates
• One for providing vital services
• Watershed regions
• Intrinsic vs Extrinsic

10
Intrinsic Modulation

• Hepatic Arterial buffer response
• Modulated by adenosine
• More Evident in Post-prandial state

11
Extrinsic Modulation

• Catecholamines
• Hormones
• vasopressin

12
Major Physiologic functions of Liver

• Blood Reservoir-500ml may be expelled
• Anesthetics may suppress this
• Vasoconstrictor response impaired of abscent in
  cirrhotics

13
Regulator of Blood coagulation

• All factors from liver except vwbf
• Vitamin K precursors(2,7,9,10)
• Bile enables absorption of vitamin K
• Thrombopoietin
• Also clears activated factors

14
Endocrine Functions of Liver

• IGF-1, Angiotensinogin, Thrombo
• T4-T3, TBG
• Corticosteroids, aldosterone, estrogen,
  insulin-all are deactivated by liver

15
LFTs

• Hepatocellular damage
• Obstruction
• Synthetic function
• Uptake/conjugation/excretion
• Other

16
Indices of Hepatocellular Damage

• AST(formerly SGOT) ALT(formerly SGPT) both
  indicators of cell damage
• ALT just liver AST other tissues
• Degree of elevation-no correlation with prognosis
• Glutathion S-transferase(iso-B) short half
  life(1/2 hour)-good monitor

17
ALT/AST

• lt3 fold elevation fatty liver, non etoh,chronic
  viral
• 3-22 fold Acute Hepatitis, alcoholic
• gt22 fold-Severe toxin, necrosis
• AST/ALTgt2ETOH
• AST/ALTlt1-viral

18
Synthetic Function

• Late finding
• Albumin-many factors make it not accurate
• PT-short half life of factor 7

19
Hepatic Diseases

• Parenchymal
• Cholestatic
• 10 American pop
• Hep B,C-5 mil

20
Parenchymal Hepatic Disease

• Viral accounts for vast majority of AH
• HepA(30), HepB(50), HepC(20)
• HepA highly contagious, fecal oral, resolves
• HepA, if superimposed on other Hepatitis-may be
  fatal

21
Viral Hepatitis

• HepA 4 wk incubation
• HepB 12wk incubation
• HepC 7 wk incubation
• Anorrhexia, N/V, fever,jaundice(1/2)
• Serologic testing

22
Non-Viral Hepatitis

• Ingestion, Inhalation,IV
• Ccl4, Acetaminophen, alpha aminitin
• Histological pattern similar, reproducible
• 1-2 days after exposure

23
Uncommon causes of Cirrhosis

• Wilsons disease
• Heredetary Hemochromatosis
• Primary Biliary Cirrhosis
• Alpha-1-Antitrypsin deficiency
• Budd-Chiari syndrome

24
National Halothane Study

• 85k anesthetics
• Fulminant hepatic necrosis 135k
• Non-fatal 13k
• Not dose dependent
• Previous exposureImmunologic?

25
Immunologic postulate

• Previous Exposure70-95 of jaundice patients
• Idiosyncratic
• Not dose dependent
• Peripheral eosinophilia, immune complexes

26
(No Transcript)
27
Cirrhosis Endstage parenchymal Disease

• gt3 million americans
• Twelfth leading cause of death
• Chronic HepC, alcoholism
• Alters nearly every organ system

28
Hepatic Circulatory Dysfunction

• Portal Hypertension-hallmark of cirrhosis
• Increased vascular resistance in sinusoids
• Increased portal flow from dilated splanchnic
  arterioles
• Hepatic arterial flow unchanged

29
Hepatic Circulatory Dysfunction

• Net Result is decreased portal Flow
• Formation of collateralsalready dilated
  collaterals reverse flow to bypass liver
• Splanchnic, high pressure blood travels to low
  pressure azygouscalled varices
• 40-60 of cirrhotics, 13 will bleed

30
Treatment of Portal hypertension

• Pharmacologic Non-selective B-blocker,
  somatostatin, octreotide.
• May reduce bleeding up to 80
• Band ligation, sclerotherapy, TIPS
• Portocaval Shunt

31
Cardiovascular changes

• Decreases SVR
• AV malformations
• Decreased responsiveness to catecholamines(glucago
  n)
• Remember cardiomyopathy

32
Pulmonary Changes in Cirrhosis

• Impaired HPV
• V/Q mismatching
• Decreased FRC
• Av malformations in pulmonary circ.
• Interstitial edema secondary to fluid retention

33
Other Organ Systems

• Renal
• Neurologic encephalopathy, post columns
• Endocrine
• Heme/coagulation

34
Risk Stratification

• Child-Pugh Score
• Model of End-Stage Liver Disease Score(MELD)

35
Child-Turcotte-Pugh

• MM for pts undergoing intra-abd surgery
• Incorporates three biochemical(PT, albumin,
  bilirubin)
• Incorporates three clinical features(Nutrition,
  /-ascites, encephalopathy

36
(No Transcript)
37
MELD SCORE

• Created in 1999 to predict 3 month mortality in
  pts with chronic dz.
• Prioritizes those on transplat list
• Looks at bilirubin,INR,and serum creatinine

38
(No Transcript)
39
MELD SCORE

• gt8 predictive of poor outcome(some type of
  morbiditys/s 91/77)
• gt24 qualifies for transplantation

40
Pre-Operative Assessment

• Initial HP(hx of hepatitis, tatoos, tansfusion,
  etoh)
• AST, ALT, bilirubin, PT
• What the procedure is
• Anyone with unexplained elevation of
  LFTs-postpone
• Test only those you suspect

41
Anesthesia

• Effective serum concentration
• Effective clearance slower conjugation, less
  perfusion, less binding
• Halothane, Enflurane reduce hepatic perfusion the
  most
• Coagulopathy

42
Physiology of Anesthesia

• Markedly reduced SVR
• Markedly reduced FRC
• Markedly increased Aa gradient
• Markedly reduced responsiveness to catecholamines
• Less Responsive liver