Severe respiratory variations of systolic arterial and central venous pressure (CVP) may increase the risk of embolic event in orthopedic patient. As airway obstruction during sedation can cause this respiratory variation, we evaluated the degree of variations of systolic blood (SBP) and CVP during airway obstruction period.

Fifteen females who had obstructed airway during total knee replacement (TKR) were included for the study. After regional anesthesia were established, SBP and CVP variations were analyzed according to the three periods; baseline, obstruction, and airway, respectively. Calculated CVP variables were similar to SBP variables as below: ΔSBP = Exp_max (maximal value at expiration) - Insp_nadir (minimal value at inspiration), %ΔSBP = (ΔSBP/ Exp_max) × 100. The frequencies of pulsus paradoxus (PP) and negative inspiratory CVP (NIC) were also measured.

At obstruction period, ΔSBP was 21.7 mmHg and 93.3% of patient had PP. Also, ΔCVP was 19.3 mmHg and 100% of patient showed NIC. %ΔCVP (140%) was larger than %ΔSBP (16%). And ΔCVP was inversely correlated with baseline and obstruction SBP and %ΔCVP was also inversely correlated with baseline CVP at obstruction period.

During airway obstruction in sedated TKR patients, variations of CVP are larger than those of SBP. So we have to monitor CVP continuously as well as SBP so as not to increase the possible risk of respiratory of variation.