Bicarbonate attenuates intracellular acidosis.
BACKGROUND
This study was prompted by concern that administration of bicarbonate for correction of lactate acidosis aggravates a low intracellular pH (pHi). In healthy subjects we evaluated skeletal muscle pHi using 31P-magnetic resonance spectroscopy during 5-minute rhythmic handgrip to provoke intracellular acidosis.


METHODS
Subjects were randomized to treatment with bicarbonate or saline infused intravenously in a cross-over study design with 1 h between trials.


RESULTS
In response to rhythmic handgrip, muscle venous O(2) hemoglobin saturation decreased from 51 +/- 4% to 36 +/- 2% and lactate increased from 1.0 +/- 0.1 to 4.9 +/- 0.5 mmol/l with a reduction in pH from 7.43 +/- 0.01-7.23 +/- 0.01 (P<0.05). pHi decreased from 7.06 +/- 0.02-6.36 +/- 0.08 (P<0.05). Infusion of bicarbonate increased the arterial blood concentration from 26 +/- 1 to 39 +/- 1 mmol/l (P<0.05). The arterial CO(2) partial pressure decreased from 5.6 +/- 0.2 to 5.2 +/- 0.3 kPa during rhythmic handgrip, whereas it increased to 5.9 +/- 0.2 kPa (P<0.05) during infusion of bicarbonate. Bicarbonate treatment also increased pH of arterial and venous blood (7.55 +/- 0.01 vs. 7.44 +/- 0.02 and 7.31 +/- 0.01 vs. 7.23 +/- 0.02, respectively; P<0.05). In the last min of rhythmic handgrip the decrease in pHi was attenuated by the administration of bicarbonate (6.60 +/- 0.11 vs. 6.40 +/- 0.12; P<0.05).


CONCLUSIONS
During exercise-induced metabolic acidosis, intravenous administration of bicarbonate increased the buffering capacity of blood and attenuated the decrease in intracellular muscle pH, although there was a small increase in the arterial carbon dioxide pressure.
Nielsen
H B
HB
Copenhagen Muscle Research Center, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Denmark. h.bay@dadlnet.dk
Hein
L
L
Svendsen
L B
LB
Secher
N H
NH
Quistorff
B
B
D000138:Acidosis / Q000188:drug therapy* / Q000503:physiopathology; D000328:Adult; D001639:Bicarbonates / Q000627:therapeutic use*; D001784:Blood Gas Analysis; D002021:Buffers; D002245:Carbon Dioxide / Q000097:blood; D015444:Exercise / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction / Q000502:physiology
D001639:Bicarbonates; D002021:Buffers; D002245:Carbon Dioxide