Comparison of Arterial and End-Tidal CO2 Tension by Position and Time Changes during Hip Replacement Arthroplasty in Elderly Patients

Kim, Chun SooK; Chung, Jin Hun; Chai, Won SeoK; Lee, Sun HaK; Kwon, Jin Hyung; KwaK, Soo Dal; Ahn, Ki Ryang; ParK, WooK

Abstract

BACKGROUND: Hip replacement arthroplasty (HRA) is highly traumatic and performed in a lateral position for several hours and dead-space ventilation may increase. So, the difference between arterial and end-tidal PCO2 was investigated depending on the changes in the patient's posture during HRA in elderly patients.
METHODS
Forty-three patients scheduled for a HRA were divided into two groups; Adult Group (n = 21, A-Group) and Elderly Group (n = 22, E-Group). Mean arterial pressure (MAP), heart rate (HR), PaO2, PaCO2, and end-tidal carbon dioxide tension (P(ET)CO2) were simultaneously measured at 10 min after anesthesia in a supine position (S[10]), at 30 min intervals from 30 min (L[30]) to 180 min (L[180]) in a lateral position and at 10 min in a supine position after the end of surgery (ES[10]) in both groups. The PaCO2-P(ET)CO2 gradient (P[a-ET]CO2) and dead space ventilation (Vd/ Vt) were calculated.
RESULTS
At S(10), P(a-ET)CO2 in the A- and E-Groups was 7.0 +/- 5.0 and 7.2 +/- 3.3 mmHg respectively. From L(30) to ES(10), the P(a-ET)CO2 and the ratio of Vd/Vt in both groups increased significantly and progressively (P < 0.05 vs the control value) and the slope in the E-Group rose two times as compared to that in the A-Group. The correlation coefficient between P(a)CO2 and P(ET)CO2 was very significant from S(10) to L(90) and ES(10) in the A-Group, and from S(10) to L (60) in the E-Group (P < 0.01).
CONCLUSIONS
For maintaining adequate ventilation of the elderly patient during HRA, PaCO2 should be measured intermittently along with the position changes after anesthesia in addition to the constant monitoring of PETCO2.