Total serum and ionized magnesium concentrations in healthy and hospitalized dogs

To determine if an association between ionized magnesium (iMg) and total magnesium (tMg) exists in healthy and hospitalized dogs admitted through an emergency service and to assess the associations between iMg and tMg with total protein, albumin, ionized calcium, and total calcium.

Prospective cohort study.

Veterinary teaching hospital.

Sixty-nine dogs were enrolled. The healthy control group (group 1) included 24 dogs, and the hospitalized group (group 2) included 45 dogs.

None.

For both groups, signalment, a venous blood gas, and serum biochemistry were obtained. In addition, the presumptive diagnosis was recorded for group 2. Blood was obtained prior to any therapeutic interventions. Group 1 tMg was within the reference interval (RI), and the values for iMg were used to provide a healthy group range (HGR) of 0.44-0.50 mmol/L. Group 2 tMg was within the RI, but iMg was below the calculated HGR range (group 2 median iMg = 0.4 mmol/L; range = 0.27-0.70). There was a significant positive correlation between iMg and tMg in each group (group 1: r = 0.6713, P = 0.0003; group 2: r = 0.5312, P = 0.0002). Ionized Mg and tMg were not significantly associated with any of the other evaluated variables in either group.

Ionized Mg and tMg were significantly associated in both healthy and hospitalized dogs, but the relationship was weaker in the hospitalized dogs compared with the healthy population. For hospitalized dogs, the relationship was weak enough to question the validity of using iMg and tMg interchangeably to track magnesium status.