• catheterisation;
  • cephalic vein;
  • dogs;
  • serial blood samples

Objective  To determine the reliability of collecting serial 4-mL blood samples over 13 h using a 20-gauge, cephalic catheter in conscious dogs.

Design  Prospective, observational study.

Animals  Twelve (6 males, 6 females) healthy, neutered, lean dogs.

Procedure  Percutaneous placement of a 20-gauge, 1.1 × 30 mm intravenous over-the-needle catheter into the cephalic vein was performed in each dog on three occasions. Catheter patency was maintained by intermittent flushing with 0.9% saline and 1 IU/mL heparinised saline solutions. Blood samples (4 mL) were obtained at 10 time-points over 13 h, with close monitoring of the dogs and the indwelling catheters. Blood volume, resistance on aspirating blood sample (minimal or marked resistance) and the methods used to improve blood flow were recorded.

Results  A high proportion (93%) of blood sample collections achieved the required 4-mL volume, and the remaining samples were greater than 1.5 mL. Of the 358 collections via the cephalic catheter, 311 (87%) were obtained with ‘minimal resistance’. The remaining collections had ‘marked resistance’ (n=47) and were associated with a loose catheter in 11% (5/47) and of unknown cause in 89% (42/47). After ‘marked resistance’ had been encountered and the catheter was flushed with saline and heparin solutions, subsequent sampling with ‘minimal resistance’ was frequently possible from the same catheter.

Conclusion  Use of a percutaneous, 20-gauge intravenous cephalic catheter allowed reliable serial collection of 4-mL blood samples over 13 h in conscious dogs.