TY  - CHAP
M1  - Book, Section
TI  - Hepatic Physiology & Anesthesia
A1  - Ramsay, Michael
A2  - Butterworth IV, John F.
A2  - Mackey, David C.
A2  - Wasnick, John D.
PY  - 2022
T2  - Morgan & Mikhail’s Clinical Anesthesiology, 7e
AB  - KEY  CONCEPTS  The  hepatic  artery,  coming  directly  off  the  celiac  trunk,  supplies  approximately  30%  of  the  blood  supply  and  50%  to  70%  of  the  liver’s  oxygen  requirements,  and  the  portal  vein  supplies  70%  of  the  blood  supply  and  the  remaining  50%  or  less  of  oxygen  requirements.  All  coagulation  factors,  with  the  exception  of  factor  VIII  and  von  Willebrand  factor,  are  produced  by  the  liver.  Vitamin  K  is  a  necessary  cofactor  in  the  synthesis  of  prothrombin  (factor  II)  and  factors  VII,  IX,  and  X.  Many  “liver  function”  tests,  such  as  serum  transaminase  measurements,  reflect  hepatocellular  necroinflammatory  activity  more  than  hepatic  function.  Liver  tests  that  measure  hepatic  synthetic  function  include  serum  albumin,  prothrombin  time  (PT)  or  international  normalized  ratio  (INR),  serum  cholesterol,  and  plasma  pseudocholinesterase.  Serum  bilirubin  reflects  liver  excretory  function.  Albumin  values  less  than  2.5  g/dL  are  generally  indicative  of  chronic  liver  disease,  acute  stress,  or  severe  malnutrition.  Increased  losses  of  albumin  in  the  urine  (nephrotic  syndrome)  or  the  gastrointestinal  tract  (protein-losing  enteropathy)  can  also  produce  hypoalbuminemia.  The  PT,  which  normally  ranges  between  11  and  14  s,  depending  on  the  control  value,  measures  the  activity  of  fibrinogen,  prothrombin,  and  factors  V,  VII,  and  X.  A  prolonged  INR  reflects  a  dysfunctional  liver.  The  effect  on  coagulation  will  depend  on  the  balance  between  coagulation  and  anticoagulation  factors.  If  production  of  protein  C,  protein  S,  and  antithrombin  3  are  affected  more  than  the  coagulation  factors,  a  normal  or  hypercoagulable  state  might  exist.  The  INR  was  developed  to  monitor  the  effect  of  warfarin,  which  only  affects  clotting  factors  made  in  the  liver,  not  hepatic-synthetized  anticoagulant  factors.  So  if  a  patient  has  an  INR  of  3  and  is  not  taking  warfarin,  the  liver  clotting  mechanism  is  dysfunctional.  Such  a  patient  could  have  a  potential  bleeding  tendency,  as  most  will  have,  but  some  will  have  an  increased  clotting  potential.  This  is  because  the  pro-coagulation  factors  may  not  be  impeded  as  much  as  the  anticoagulation  factors,  so  additional  assessment  should  be  done  in  this  situation  before  withholding  venous  thromboembolism  (VTE)  prophylaxis  or  administering  fresh  frozen  plasma.  Operative  procedures  near  the  liver  can  reduce  hepatic  blood  flow  up  to  60%.  Although  the  mechanisms  are  not  clear,  they  most  likely  involve  sympathetic  activation,  local  reflexes,  and  direct  compression  of  vessels  in  the  portal  and  hepatic  circulations.  The  neuroendocrine  stress  response  to  surgery  and  trauma  is  characterized  by  elevated  circulating  levels  of  catecholamines,  glucagon,  and  cortisol  and  results  in  the  mobilization  of  carbohydrate  stores  and  proteins,  causing  hyperglycemia  and  a  negative  nitrogen  balance  (catabolism).  All  opioids  can  potentially  cause  spasm  of  the  sphincter  of  Oddi  and  increase  biliary  pressure.  When  liver  tests  are  abnormal  postoperatively,  the  usual  cause  is  underlying  liver  disease  or  the  surgical  procedure  itself.  Liver  cirrhosis  may  result  in  portal  hypertension,  bleeding  varices,  and  major  organ  dysfunction.  
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessanesthesiology.mhmedical.com/content.aspx?aid=1190607925
ER  -