Effects of doxapram, prethcamide and lobeline on spirometric, blood gas and acid–base variables in healthy new-born calves

Bleul, U.; Bylang, T.

Effects of doxapram, prethcamide and lobeline on spirometric, blood gas and acid–base variables in healthy new-born calves

2012

Bleul, U. | Bylang, T.

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 (3–15h old) calves were treated in a randomised sequence with doxapram (40mg, IV), lobeline (5mg, IV) or prethcamide (5mL, consisting of 375mg crotethamide and 375mg cropropamide, buccally). Blood and spirometric measurements, using an ultrasonic spirometer, were collected prior to and 1, 5, 15, 30, 60, 90min after administration of each drug. Doxapram caused a significant increase in the respiratory rate, peak inspiratory and expiratory flow and minute volume (Vₘᵢₙ) during the 90-min post-treatment study period, although maximum values occurred 1min after treatment. The Vₘᵢₙ increased from 13.8±5.0L to 28.5±12.3L. 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 (PₐO₂) (77.7±18.8mm Hg to 93.2±23.7mm Hg), a decrease in arterial partial pressure of carbon dioxide (PₐCO₂) (42.6±4.9mm Hg to 33.1±6.6mm Hg), a significant increase in pH and a decrease in bicarbonate concentration and base excess 1min after treatment. Prethcamide caused a gradual increase in PₐO₂ and decrease in PₐCO₂ over 90min, 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.

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