Table 2.

Plasma total and unbound cefazolin concentrations measured at different points during cardiothoracic surgery with cardiopulmonary bypass (CPB)

	Sampling time
	Before skin incision (n = 27)	At initiation of CPB or trough before CPB (n = 29)	During CPB (n = 89)	At wound closure (n = 54)
Total concentration (μg mL−1)	79 [55‐134]	71 [29‐134]	159 [89‐232]	140 [60‐230]
% below target threshold (40 μg mL−1)	0	1a	0	0
Unbound concentration (μg mL−1)	17 [11‐35]	15 [6‐45.8]	70 [21‐137]	44 [13‐127]
% below 8 μg mL−1	0	1b	0	0
% below 2 μg mL−1	0	0	0	0

Data are shown as medians and ranges in the brackets.

^aA patient with an irregular surgical course showed total and unbound plasma cefazolin concentrations of 35.4 and 8.3 μg mL⁻¹, and ^banother patient showed total and unbound plasma cefazolin concentrations of 40.4 and 6.0 μg mL⁻¹, respectively. After receiving the first dose of cefazolin (1 g) before skin incision, initiation of CPB was delayed until 366 min from the first dose due to difficulties in operation, and he received the second dose of cefazolin before the initiation of CPB. The total and unbound plasma trough concentrations obtained immediately before the second dose (at 270 min from the first dose) were 40.4 and 6.0 μg mL⁻¹, respectively. Total and unbound plasma drug concentrations measured at the initiation of CPB were higher than the respective target concentrations.