Causes of metabolic acidosis in canine hemorrhagic shock: role of unmeasured ions.
BACKGROUND
Metabolic acidosis during hemorrhagic shock is common and conventionally considered to be due to hyperlactatemia. There is increasing awareness, however, that other nonlactate, unmeasured anions contribute to this type of acidosis.


METHODS
Eleven anesthetized dogs were hemorrhaged to a mean arterial pressure of 45 mm Hg and were kept at this level until a metabolic oxygen debt of 120 mLO2/kg body weight had evolved. Blood pH, partial pressure of carbon dioxide, and concentrations of sodium, potassium, magnesium, calcium, chloride, lactate, albumin, and phosphate were measured at baseline, in shock, and during 3 hours post-therapy. Strong ion difference and the amount of weak plasma acid were calculated. To detect the presence of unmeasured anions, anion gap and strong ion gap were determined. Capillary electrophoresis was used to identify potential contributors to unmeasured anions.


RESULTS
During induction of shock, pH decreased significantly from 7.41 to 7.19. The transient increase in lactate concentration from 1.5 to 5.5 mEq/L during shock was not sufficient to explain the transient increases in anion gap (+11.0 mEq/L) and strong ion gap (+7.1 mEq/L), suggesting that substantial amounts of unmeasured anions must have been generated. Capillary electrophoresis revealed increases in serum concentration of acetate (2.2 mEq/L), citrate (2.2 mEq/L), alpha-ketoglutarate (35.3 microEq/L), fumarate (6.2 microEq/L), sulfate (0.1 mEq/L), and urate (55.9 microEq/L) after shock induction.


CONCLUSIONS
Large amounts of unmeasured anions were generated after hemorrhage in this highly standardized model of hemorrhagic shock. Capillary electrophoresis suggested that the hitherto unmeasured anions citrate and acetate, but not sulfate, contributed significantly to the changes in strong ion gap associated with induction of shock.
Bruegger
Dirk
D
Clinic of Anesthesiology, Ludwig-Maximilians-University, Marchioninistrasse 15, 81377 Munich, Germany. dirk.bruegger@med.uni-muenchen.de
Kemming
Gregor I
GI
Jacob
Matthias
M
Meisner
Franz G
FG
Wojtczyk
Christoph J
CJ
Packert
Kristian B
KB
Keipert
Peter E
PE
Faithfull
N Simon
NS
Habler
Oliver P
OP
Becker
Bernhard F
BF
Rehm
Markus
M
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000138:Acidosis / Q000097:blood* / Q000209:etiology; D000818:Animals; D000838:Anions / Q000097:blood; D001784:Blood Gas Analysis / Q000379:methods; D004285:Dogs; D019075:Electrophoresis, Capillary / Q000379:methods; D005260:Female; D008297:Male; D012771:Shock, Hemorrhagic / Q000097:blood* / Q000150:complications
D000838:Anions