Validation of the Hartford nomogram in trauma surgery patients

OBJECTIVE: TO validate the Hartford nomogram for once-daily aminoglycoside dosing in trauma surgery patients. METHODS: A chart review was performed in trauma surgery patients who were started on once-daily aminoglycoside therapy. A peak aminoglycoside concentration was drawn 30 minutes after the end of the first or second infusion, and a random concentration was drawn approximately 10 hours after the dose. The 10-hour random concentration was used to validate the Hartford nomogram by predicting the actual dosing interval (determined by extrapolating the peak and random concentrations to achieve a trough concentration <1 mg/L). The percentage of intervals accurately predicted by the nomogram was determined. RESULTS: Forty-nine patients (34 men and 15 women), age 43.0 +/- 15.9 y, total body weight 81.3 +/- 24.5 kg, ideal body weight 68.1 +/- 10.7 kg, dosing body weight (DBW) 72.0 +/- 14.4 kg, and estimated creatinine clearance (Cl-er) 89.5 +/- 20.6 mL/min/1.73 m(2) were evaluated Patients received 505 +/- 105 mg (7.0 +/- 0.4 mg/kg) of either gentamicin or tobramycin per dose. The concentration 30 minutes after the infusion was 22.4 +/- 5.9 mg/L, the concentration at the end of the dosing interval was 0.20 +/- 0.46 mg/L, the 10-hour random concentration was 2.6 +/- 1.8 mg/L, the elimination rate constant was 0.26 +/- 0.08 h(-1), the elimination half-life was 3.0 +/- 1.2 hours, and the volume of distribution was 19.9 +/- 7.9 L (0.28 +/- 0.09 L/kg of DBW). Ninety-eight percent (48/49) of the intervals were accurately predicted by the nomogram. CONCLUSION'S: In trauma surgery patients with Cl-er of more than 60 ml/min/1.73 m(2), the Hartford nomogram using a single random aminoglycoside concentration accurately predicted the same once-daily aminoglycoside intervals as determined by two concentrations. Less aggressive therapeutic drug monitoring in this patient subpopulation can lead to significant cost savings.