Induction of a Serotonin-S2 Receptor Blockade During Early or Late Stage of Acute Respiratory Distress Syndrome in Double-Muscled Calves: A Comparative Study

Ninety-four Belgian White and Blue double-muscled calves were involved in this study which aimed to compare the efficacy of a serotonin-S2 receptor blockade at two different stages of an acute respiratory distress syndrome (ARDS), i.e. at the occurrence of first clinical signs or when another anti-inflammatory compound was clinically shown to be ineffective. Metrenperone, a 5-hydroxytryptamine (5-HT2) blocker, was injected (intramuscularly, 5 times, at 12 hourly intervals, dose rate: 0.1 mg/kg) to (1) 58 calves referred to our laboratory after a treatment (group I) which lasted from 3 to 5 days and which did not improve the clinical status of the animals and (2) 36 calves investigated as soon as first clinical signs occurred (group II). Following the severity of the ARDS, the animals from group I needed to be classified into 2 groups: group IA (moderate ARDS - n = 45) and group IB (severe ARDS - n = 13). For animals in group I, the antibacterial compound previously used was maintained and administered during 4 more days whilst the previous anti-inflammatory drug was suppressed and replaced by metrenperone administered as mentioned above. In group II, each animal was treated with ceftiofur sodium as an antibacterial agent. A clinical score and a breathing score were calculated at each step of the investigation period, i.e. before (T0) and 1 hour (T1) after the first treatment, during the interval 12H-48H (T2) which followed this treatment and 168 H (T3) after this treatment. Four clinical parameters were also taken into account separately: rectal and cutaneous temperatures, respiratory and heart rates.(ABSTRACT TRUNCATED AT 250 WORDS)