RT Book, Section
A1 Butterworth IV, John F.
A1 Mackey, David C.
A1 Wasnick, John D.
SR Print(0)
ID 1190611009
T1 Acid–Base Management
T2 Morgan & Mikhail’s Clinical Anesthesiology, 7e
YR 2022
FD 2022
PB McGraw-Hill Education
PP New York, NY
SN 9781260473797
LK accessanesthesiology.mhmedical.com/content.aspx?aid=1190611009
RD 2023/11/28
AB KEY  CONCEPTS  The  strong  ion  difference,  PaCO2,  and  total  weak  acid  concentration  best  explain  acid–base  balance  in  physiological  systems.  The  bicarbonate  buffer  is  effective  against  metabolic,  but  not  respiratory,  acid–base  disturbances.  In  contrast  to  the  bicarbonate  buffer,  hemoglobin  is  capable  of  buffering  both  carbonic  (CO2)  and  noncarbonic  (nonvolatile)  acids.  As  a  general  rule,  PaCO2  can  be  expected  to  increase  0.25  to  1  mm  Hg  for  each  1  mEq/L  increase  in  [HCO3–].  The  renal  response  to  acidemia  is  three-fold:  (1)  increased  reabsorption  of  filtered  [HCO3–],  (2)  increased  excretion  of  titratable  acids,  and  (3)  increased  production  of  ammonia.  With  chronic  respiratory  acidosis,  plasma  [HCO3–]  increases  approximately  4  mEq/L  for  each  10  mm  Hg  increase  in  PaCO2  above  40  mm  Hg.  Diarrhea  is  a  common  cause  of  hyperchloremic  metabolic  acidosis.  The  distinction  between  acute  and  chronic  respiratory  alkalosis  is  not  always  made  because  the  compensatory  response  to  chronic  respiratory  alkalosis  is  quite  variable:  Plasma  [HCO3–]  decreases  2  to  5  mEq/L  for  each  10  mm  Hg  decrease  in  PaCO2  below  40  mm  Hg.  Vomiting  or  continuous  loss  of  gastric  fluid  by  gastric  drainage  (nasogastric  suctioning)  can  result  in  marked  metabolic  alkalosis,  extracellular  volume  depletion,  and  hypokalemia.  The  combination  of  alkalemia  and  hypokalemia  can  precipitate  severe  atrial  and  ventricular  arrhythmias.  Changes  in  temperature  affect  PaCO2,  PaO2  and  pH.  Both  PaCO2  and  PaO2  decrease  during  hypothermia,  but  pH  increases  because  temperature  does  not  appreciably  alter  [HCO3–]  and  the  dissociation  of  water  decreases  (decreasing  H+  and  increasing  pH).