When temperature was examined as a binary variable (≤36.5°C), patients with hypothermic T
max had less total blood loss than those without (–151 mL [95% CI, –284 to –19 mL];
P=.03) (
Table 2). Evidence was not statistically significant for intraoperative blood loss and net blood loss (
P=.08 and
P=.06, respectively). Conversely, patients with hypothermic T
min had more blood loss in all 3 parameters (all
P≤.05). On further investigation, 18 patients recorded both T
max and Tmin greater than 36.5°C (group 1), and 64 patients had T
max greater than 36.5°C but T
min less than or equal to 36.5°C (group 2). The remaining 86 patients had both T
max and T
min less than or equal to 36.5°C (group 3). When T
min was greater than 36.5°C, these differences in intraoperative, total, and net blood loss between group 1 and group 2 were negative, and group 1 had lower but not significant levels of blood loss (
P=.17,
P=.25, and
P=.45, respectively). When T
min was less than or equal to 36.5°C, differences between group 2 and group 3 were positive, and group 2 had significantly greater levels of blood loss (130 mL [95% CI, 19-222 mL], 242 mL [95% CI, 106-377 mL], and 148 mL [95% CI, 44-251 mL];
P=.02,
P<.001, and
P=.01, respectively). Owing to the larger sample size of group 2, the main effect of groups 1 and 2 vs group 3 was positive, which is not useful in the presence of an interaction. There was no significant difference between group 1 and group 3 in intraoperative, total, or net blood loss (
P=.35,
P=.25, and
P=.45, respectively). Hypothermic T
a had no correlation with any of the blood loss parameters (all
P≥.89).