Diastolic blood pressure in patients with tibia fractures under anaesthesia: Implications for the diagnosis of compartment syndrome

OBJECTIVE: In the treatment of tibia fractures, is the intraoperative diastolic blood pressure (DBP) less than pre- and postoperative DBP, and how does this relate to the diagnosis of compartment syndrome using ΔP (diastolic blood pressure [DBP] - intracompartmental pressure)? DESIGN, SETTING, AND PATIENTS: This was a prospective cohort study in a level 1 trauma center, with a consecutive series of 242 patients with a tibia fracture. INTERVENTION: Intramedullary nail fixation of tibia fractures under general anesthesia. MAIN OUTCOME MEASURES: Patient demographics, type and location of fracture, injury severity score, and blood pressures preoperatively, intraoperatively, and postoperatively. RESULTS: There were 187 male and 55 female patients, whose ages ranged from 16 to 87 years (average, 39 years). There were 123 open and 119 closed tibia fractures. The average injury severity score was 14.7 (range: 9-41). Anesthetized patients had a significant decrease in their DBP and systolic blood pressure (SBP) compared with their preoperative, postanesthesia care unit and postoperative floor measurements. The mean DBP in the operating room was 18 ± 13 mm Hg lower than the preoperative measurement (P < 0.05), whereas the difference in the preoperative and postoperative mean DBP was only 2 ± 13 mm Hg. CONCLUSIONS: There is a predictable response of DBP in patients with tibia fractures treated with intramedullary (IM) nailing under general anesthesia. The preoperative DBP is a good indicator of the postoperative DBP, and the intraoperative DBP is significantly lower (average 18 mm Hg; P < 0.05). The surgeon should recognize that intraoperative ΔP may be lower than ΔP once the patient is awakened in deciding whether to perform a fasciotomy or awaken the patient and perform serial examinations and or compartment pressure measurements. Intraoperative ΔP may be spuriously low compared with that after the patient is awakened.