Effect of adenosine infusion on oxygen induced carbon dioxide retention in severe chronic obstructive pulmonary disease.
BACKGROUND
In normal subjects intravenous adenosine infusion has been shown to stimulate ventilation with a consequent fall in arterial partial pressure of carbon dioxide (Paco2), probably by an action on the carotid bodies. The objective of this study was to determine whether the increase in Paco2 seen when patients with ventilatory failure secondary to chronic obstructive pulmonary disease (COPD) are given a high concentration of oxygen to breathe might be ameliorated by an intravenous infusion of adenosine.


METHODS
Eight subjects with chronic stable ventilatory failure secondary to COPD were studied. Their mean (SE) forced expiratory volume in one second (FEV1) was 0.63 (0.12) 1 with forced vital capacity (FVC) of 1.63 (0.21) 1. They received continuous intravenous infusions of saline and adenosine in random order, double blind. The infusions were administered for two minutes at 20 micrograms/kg/min, increasing in increments of 20 micrograms/kg/min every two minutes to a maximum infusion rate of 80 micrograms/kg/min adenosine (or an equivalent saline infusion rate), or until side effects supervened. The infusions were continued at that rate for five minutes, after which the fractional inspired oxygen (FIO2) was raised to 0.50 during a further 20 minutes of the infusion at that rate. Haemoglobin oxygen saturation (SaO2) and transcutaneous PCO2 (PtcCO2) were monitored throughout the procedure. Spirometric tests were performed before and after each infusion.


RESULTS
Adenosine infusion was accompanied by a fall in PtcCO2 from a mean (SE) of 7.29 (0.42) kPa to 6.95 (0.48) kPa: mean difference -0.34 (95% confidence interval, -0.56 to -0.11) kPa. During saline infusion oxygen administration resulted in an increase in transcutaneous PtcCO2 from 7.35 (0.34) kPa to 7.88 (0.28) kPa: mean difference 0.53 (95% CI 0.20 to 0.85) kPa. PtcCO2 did not rise above baseline levels when oxygen was administered during the adenosine infusion. A small fall in FVC was seen following adenosine infusion.


CONCLUSIONS
The increase in PtcCO2 seen when patients with stable ventilatory failure secondary to severe COPD are given a high concentration of oxygen to breathe is counteracted by a continuous intravenous infusion of adenosine.
Griffiths
T L
TL
Division of Physiological Medicine, St George's Hospital Medical School, London, UK.
Fernando
S S
SS
Saunders
K B
KB
D000241:Adenosine / Q000627:therapeutic use*; D002245:Carbon Dioxide / Q000097:blood; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000209:etiology / Q000517:prevention & control*; D007262:Infusions, Intravenous; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000628:therapy*; D008297:Male; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy / Q000009:adverse effects*; D010313:Partial Pressure
D002245:Carbon Dioxide; D000241:Adenosine; D010100:Oxygen