A number of drugs have been used to treat
asphyxia in new-born calves and the aim of the current study was to investigate the effect of commonly-used stimulant drugs on ventilation, arterial blood gas and
acid base variables. A group (n=18) of new-born (3-15 h old) calves were treated in a randomised sequence with
doxapram (40 mg, IV),
lobeline (5mg, IV) or
prethcamide (5 mL, consisting of 375 mg
crotethamide and 375 mg
cropropamide, buccally). Blood and spirometric measurements, using an ultrasonic spirometer, were collected prior to and 1, 5, 15, 30, 60, 90 min after administration of each
drug.
Doxapram caused a significant increase in the respiratory rate, peak inspiratory and expiratory flow and minute volume (V(min)) during the 90-min post-treatment study period, although maximum values occurred 1 min
after treatment. The V(min) increased from 13.8 ± 5.0 L to 28.5 ± 12.3 L.
Prethcamide, but not
lobeline, also caused significant increases in inspiratory and expiratory volumes. The effects of
doxapram on ventilation were accompanied by an increase in arterial partial pressure of
oxygen (P(a)O(2)) (77.7 ± 18.8 mm Hg to 93.2 ± 23.7 mm Hg), a decrease in arterial partial pressure of
carbon dioxide (P(a)CO(2)) (42.6 ± 4.9 mm Hg to 33.1 ± 6.6mm Hg), a significant increase in pH and a decrease in
bicarbonate concentration and base excess 1 min
after treatment.
Prethcamide caused a gradual increase in P(a)O(2) and decrease in P(a)CO(2) over 90 min, whereas
lobeline had no measurable effect on the investigated variables. Of the three treatments, only
doxapram had a distinct stimulatory effect on respiration in healthy neonatal calves and may therefore be useful in the treatment of calf
asphyxia.