Plasma colloid osmotic pressure and total protein in horses during colic surgery.
OBJECTIVE
To assess the changes in colloid osmotic pressure (COP) in horses undergoing surgery for colic.


METHODS
Prospective clinical evaluation.


METHODS
Twenty-nine adult horses presented for emergency laparotomy.


METHODS
Horses were premedicated with intravenous (IV) xylazine and anesthesia was induced with ketamine, diazepam and guaifenesin and was maintained with isoflurane as required. Lactated Ringer's solution (LRS) was given to all horses during anesthesia. Blood was collected in heparin before, and every 30 minutes during, anesthesia to measure COP, total protein concentration (TP), osmolality, packed cell volume, electrolytes, glucose and lactate. In addition, COP was estimated using different formulas previously described for horses.


RESULTS
Before anesthesia, COP and TP were 18.7 +/- 2.2 mmHg (2.49 +/- 0.29 kPa) and 6.3 +/- 0.7 g dL(-1), respectively. The horses received a mean +/- SD of 19.5 +/- 3.9 mL kg(-1) hour(-1) (range 15-25 mL kg(-1)hour(-1)) of LRS during anesthesia. The COP and TP decreased linearly (R(2) = 0.99, p < 0.01) during anesthesia and reached the lowest point at the end of anesthesia with a COP of 11.6 +/- 1.6 mmHg (1.55 +/- 0.21 kPa) and TP of 4.4 +/- 0.4 g dL(-1). The Pearson correlation coefficient for COP versus TP was r(2) = 0.78. Calculation of COP from TP concentrations showed that two formulas could predict COP to within 1 mmHg (0.13 kPa) (Thomas & Brown 1992; Boscan et al. 2007).


CONCLUSIONS
Colloid osmotic pressure, like TP, decreased greatly over the course of crystalloid fluid infusion during anesthesia for laparotomy in horses with colic. This change may predispose the animal to tissue edema with subsequent morbidity.
Boscan
Pedro
P
Veterinary Medical Teaching Hospital, University of California, Davis, CA, USA. pboscan@colostate.edu
Steffey
Eugene P
EP
D000758:Anesthesia / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D003085:Colic / Q000601:surgery / Q000662:veterinary; D003102:Colloids / Q000378:metabolism*; D006734:Horse Diseases / Q000097:blood / Q000601:surgery; D006736:Horses / Q000097:blood*; D007262:Infusions, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D007552:Isotonic Solutions / Q000008:administration & dosage; D007813:Laparotomy / Q000662:veterinary; D009997:Osmotic Pressure / Q000187:drug effects*; D011446:Prospective Studies; D000077325:Ringer's Lactate
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D001798:Blood Proteins; D003102:Colloids; D007552:Isotonic Solutions; D000077325:Ringer's Lactate; D007530:Isoflurane