Brightness of venous blood in South American camelids: implications for jugular catheterization

Objective  To compare the brightness of South American camelid venous blood to that of Equidae.
Study design  Prospective clinical evaluation.
Animals  Twelve South American camelids (eight llamas, four alpacas), eight horses and ponies (control group).
Methods  Appropriately sized catheters were placed in the jugular vein of each animal under local anaesthesia. The blood spilt before the catheter was capped was caught on a white tile. A sample of blood was drawn for blood-gas analysis. The brightness of the blood (both on the tile and in the syringe) was matched to a colour chart (1 = darkest red, 8 = brightest red) by a single observer under bright light conditions. Packed cell volume (PCV) and partial pressure of oxygen (PvO₂) in the blood were also measured on the syringe blood. Normally distributed data were compared using a two tailed t -test, and non-normally distributed data were compared using a Mann–Whitney U -test. Significance was set at p  < 0.05.
Results  Camelid venous blood was significantly brighter red than that of horses and ponies both on the white tile ( p  = 0.0003) and in the syringe ( p  = 0.0001). PCV was significantly lower in camelids (32 ± 4%) compared with horses (37 ± 5%). Partial pressure of oxygen values were similar between groups.
Conclusions and clinical relevance  Jugular venous blood in alpacas and llamas is significantly brighter red than that of horses. Colour should not be used as a sole determinant of venous or arterial catheterization in this species.