Short papers Cardiovascular side eVects of inhaled salbutamol in hypoxic asthmatic patients

Background—Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and â2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the eVect of hypoxia on the systemic vascular eVects of salbutamol in patients with asthma who are hypoxic by assessing forearm blood flow (FBF) as a measure of peripheral vasodilatation. Methods—Eight men with mild asthma underwentthefollowingtreatments:normoxia + placebo (NP), normoxia + salbutamol (NS), hypoxia + placebo (HP), and hypoxia + salbutamol (HS). The period of mask breathing started at t=0 minutes, lasted for 60 minutes, and at 30 minutes 800 μg salbutamol was inhaled. The experiment was completed 30 minutes after the inhalation (t=60 minutes). For the hypoxia treatment the SpO2 level was 82%. DiVerences between treatments were sought using factorial ANOVA on percentage change from the pretreatment value. Results—There were no significant diVerences in blood pressure and potassium levels between the treatments. After 60 minutes the increase in FBF was 13% (95% CI –12 to 39) more for HP treatment than for NP, 21% (95% CI –5 to 46) more for NS than for NP, and 32% (95% CI 7 to 58) more for HS than for HP (p=0.016). The inhalation of salbutamol during hypoxia resulted in a significant increase in FBF of 45% (95% CI 20 to 71) compared with NP (p=0.001). Conclusion—Patients with asthma who are hypoxic and inhale â2 agonists have serious systemic vascular side eVects which may be an additional explanation for the association between asthma treatment and sudden death. (Thorax 2001;56:567–569)