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Salbutamol decreases potassium concentration during heavy rowing exercise but not immediately following recovery

T. Atanasovska,1 A.C. Petersen,1 R. Smith,1,2 A. Tobin3 and M.J. McKenna,1 1Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Footscray, VIC 3011, Australia, 2Department of Anaesthesia & Pain Management, Western Hospital, Footscray, VIC 3011, Australia and 3Specialist Intensive Care Unit, St. Vincent Hospital, Fitzroy, VIC 3065, Australia.

Intense exercise causes pronounced increases in plasma potassium (K+), and often results in transient hypokalaemia during recovery. Skeletal muscle Na+,K+-ATPase plays a essential role in maintaining potassium homeostasis. Salbutamol has an stimulatory effect on skeletal muscle Na+,K+-ATPase and may thus affect potassium dynamics during exercise and in recovery. We investigated whether salbutamol lowered arterial plasma K+ concentration ([K+]a) during intense exercise and in recovery. Radial plasma [K+]a was measured during intense rowing exercise for 3 min in 11 healthy adults (age 30.6 ± 6.5 yr, height 1.81 ± 0.72 m, body mass 86.17 ± 10.90 kg, mean±SD) in a single-blinded randomised trial, either with or without 1000 μg salbutamol inhalation. Blood was sampled at baseline, during rowing exercise and for 60 min post-exercise and analysed for [K+], other electrolytes and acid-base.

Plasma [K+]a revealed significant effects for time and condition (salbutamol) and time by condition interaction (P < 0.05). Arterial [K+] increased during exercise from baseline (-20 min) and pre-exercise (−2 min) reaching 7.06 ±0.61 mM at end exercise in placebo. In recovery, plasma [K+]a decreased rapidly, falling below baseline (P < 0.01) and pre-exercise (P < 0.001) by 3 min. Salbutamol lowered plasma [K+]a at rest by 0.45 mM and was increased to 6.92 ± 0.50 mM at end exercise in salbutamol (P < 0.05, The Figure). Following exercise plasma [K+]a reached a nadir of 3.06 ± 0.31 mM by 3 min (P < 0.05) in salbutamol. In recovery, salbutamol inhalation did not further lower plasma [K+]a immediately following exercise. At end-exercise, blood [lactate]a reached 12.52 ± 1.62 mM (placebo) and 11.99 ± 1.96 mM (salbutamol) (P < 0.05), pHa decreased to 7.13 ± 0.07 (placebo) and 7.16 ± 0.07 (salbutamol) (P < 0.05).

Figure 1

The pronounced and sustained arterial [K+] during rowing reflects the high intensity exercise and large contracting muscle mass with the post-exercise decline in plasma [K+]a to below baseline during recovery, likely due to continued Na+,K+-ATPase activity (Atanasovska, 2014). The lowering effect of plasma [K+]a with salbutamol likely reflects increased skeletal muscle Na+-K+-ATPase activity due to beta-agonist stimulation, but this was not more pronounced immediately following exercise with salbutamol. This suggests no additive effects of salbutamol beyond normal exercise induced plasma K+ lowering which may be a protective mechanism to prevent plasma [K+]a falling to dangerous levels.

Atanasovska T, Petersen AC, Rouffet DM, Billaut F, Ng I, McKenna MJ. (2014) Plasma K+ dynamics and implications during and following intense rowing exercise. Journal of Applied Physiology 117, 60-68.