Bicarbonate attenuates arterial desaturation during maximal exercise in humans.
The contribution of pH to exercise-induced arterial O2 desaturation was evaluated by intravenous infusion of sodium bicarbonate (Bic, 1 M; 200-350 ml) or an equal volume of saline (Sal; 1 M) at a constant infusion rate during a "2,000-m" maximal ergometer row in five male oarsmen. Blood-gas variables were corrected to the increase in blood temperature from 36.5 +/- 0.3 to 38.9 +/- 0.1 degrees C (P < 0.05; means +/- SE), which was established in a pilot study. During Sal exercise, pH decreased from 7.42 +/- 0.01 at rest to 7.07 +/- 0.02 but only to 7.34 +/- 0.02 (P < 0.05) during the Bic trial. Arterial PO2 was reduced from 103.1 +/- 0.7 to 88.2 +/- 1.3 Torr during exercise with Sal, and this reduction was not significantly affected by Bic. Arterial O2 saturation was 97.5 +/- 0.2% at rest and decreased to 89.0 +/- 0.7% during Sal exercise but only to 94.1 +/- 1% with Bic (P < 0.05). Arterial PCO2 was not significantly changed from resting values in the last minute of Sal exercise, but in the Bic trial it increased from 40.5 +/- 0.5 to 45.9 +/- 2.0 Torr (P < 0.05). Pulmonary ventilation was lowered during exercise with Bic (155 +/- 14 vs. 142 +/- 13 l/min; P < 0.05), but the exercise-induced increase in the difference between the end-tidal O2 pressure and arterial PO2 was similar in the two trials. Also, pulmonary O2 uptake and changes in muscle oxygenation as determined by near-infrared spectrophotometry during exercise were similar. The enlarged blood-buffering capacity after infusion of Bic attenuated acidosis and in turn arterial desaturation during maximal exercise.
The Copenhagen Muscle Research Center, Department of Anesthesia, Rigshospitalet, DK-2100 Copenhagen, Denmark. h.bay@dadlnet.dk
Henning B
HB
Nielsen
Per P
PP
Bredmose
Morten
M
Strømstad
Stefanos
S
Volianitis
Bjørn
B
Quistorff
Niels H
NH
Secher
D000138:Acidosis / Q000188:drug therapy / Q000503:physiopathology*; D000328:Adult; D002245:Carbon Dioxide / Q000097:blood*; D006339:Heart Rate; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration; D017693:Sodium Bicarbonate / Q000008:administration & dosage* / Q000097:blood; D019265:Spectroscopy, Near-Infrared
D002245:Carbon Dioxide; D019344:Lactic Acid; D017693:Sodium Bicarbonate; D010100:Oxygen