Osteocalcin, but not deoxypyridinoline, increases in response to isoflurane-induced anaesthesia in young female guinea pigs.

Abstract

The effect of the inhaled anaesthetic isoflurane was investigated on bone biomarkers, both during maturation and on minerals and glucose postpartum. Female guinea pigs (n=10) were anaesthetized during maturation (5 and 9weeks) and postpartum (26weeks of age) with isoflurane during dual-energy X-ray absorptiometry scanning. Blood collection was performed at all ages before and after anaesthesia for measurement of plasma osteocalcin (OC), total deoxypyridinoline (tDPD), and cortisol. Postpartum measurements also included: blood ions, acid-base parameters and glucose, plasma minerals, total alkaline phosphatase (tALP), and albumin. Plasma OC concentration almost doubled after exposure to isoflurane at 5weeks (30.1±5.0-57.9±11.2nmol/L, p<0.001) and at 9weeks (29.1±7.5-62.9±15.9nmol/L, p<0.001), but did not change postpartum (3.7±3.3-4.3±3.9nmol/L, p=0.88). There was no effect of isoflurane exposure on plasma tDPD at any age. Plasma cortisol increased after exposure to isoflurane at 9weeks (1859.6±383.2-2748.0±235.3nmol/L, p<0.01) and postpartum (3376.7±322.2-4091.6±195.6nmol/L, p<0.001) but not at 5weeks (2088.3±326.4-2464.1±538.0nmol/L, p>0.05). Blood ionized Ca(2+), Na(+) and plasma total Ca did not change, whereas plasma albumin decreased, and inorganic phosphate (PO4) and Cl(-) increased upon exposure to isoflurane. Isoflurane decreased tALP (43.2±6.6-40.2±5.9IU/L, p=0.01) and increased glucose (7.5±0.6-10.9±1.7mmol/L, p<0.0001) postpartum. Isoflurane inflates the assessment of a bone-derived biomarker, OC, during rapid growth, but not following pregnancy when formation is very low. Measurements prior to anaesthesia are recommended to reflect normal metabolism.