Variation in Arterial to End-Tidal CO2 Tension Differences During Anesthesia in the ???Kidney Rest??? Lateral Decubitus Position

Abstract

The course of arterial to end-tidal carbon dioxide tension difference [P(a-ET)CO2] was evaluated during general anesthesia in 25 patients scheduled for renal surgery performed in the "kidney position." The difference between arterial PCO2 (PaCO2) corrected to body temperature, and end-tidal PCO2 (PETCO2) measured by mass spectrometry was assessed after induction of anesthesia, after placement in the lateral decubitus position with back arched over a kidney bridge ("kidney position"), and every 20 min until the patients were replaced in the supine position at the end of the surgical procedure. Heart rate, arterial blood pressure, and esophageal temperature were simultaneously recorded. After induction of anesthesia, when the patients were lying supine (T1), P(a-ET)CO2 was 4.8 +/- 3.9 mm Hg (mean +/- SD). Placing the patients in the kidney position (T2) induced a significant increase in P(a-ET)CO2 (to 7.9 +/- 3.5 mm Hg; P less than 0.01). These alterations occurred without any significant change in mean arterial blood pressure or heart rate. A progressive increase in mean P(a-ET)CO2 occurred with maintenance of anesthesia; P(a-ET)CO2 reached 8.8 +/- 4.1 mm Hg (P less than 0.05 vs T2) and 8.9 +/- 4.4 mm Hg (P less than 0.05 vs T2) at 65 and 85 min, respectively, after lateral decubitus positioning. Large variations between and within patients were observed. Although stable mean arterial pressure was maintained, these changes were associated with a significant decrease in body temperature. These results demonstrate that P(a-ET)CO2 increases when patients are placed in the kidney position and may vary with the prolongation of anesthesia in this situation.(ABSTRACT TRUNCATED AT 250 WORDS)

Deep Breathing Improves End-Tidal Carbon Dioxide Monitoring of an Oxygen Nasal Cannula-Based Capnometry Device in Subjects Extubated After Abdominal Surgery

“…These values appear somewhat greater than the reported differences between P ETCO 2 and P aCO 2 in intubated subjects, which average 5 mm Hg but can be as high as 15 mm Hg. 16,17 However, they compare favorably with those measured with the previously investigated oxygen mask-based capnometry, 11 for which we reported that the differences were 12.6 and 9.1 mm Hg during resting breathing (regardless of the mouth condition) and deep breathing, respectively. Interestingly, the difference between the P aCO 2 and P ETCO 2 gradually decreased from resting breathing to mouth closed breathing to deep breathing.…”

Noninvasive monitoring of PaCO2 during one-lung ventilation and minimal access surgery in adults: End-tidal versus transcutaneous techniques

“…[13] Patient positioning has also been shown to have an impact on the accuracy of ET-CO 2 monitoring. [23] With patients undergoing renal or upper ureteral surgery in the supine position, Pansard et al reported that the ET-CO 2 to PaCO 2 difference was 4.8 ± 3.9 mmHg 10 min after induction and increased to 7.9 ± 3.5 mmHg ( P <0.01) 5 min after placement of the patients into the lateral decubitus ‘kidney rest’ position. Similar results were reported by Grenier et al in a cohort of patients undergoing neurosurgical procedures in the lateral decubitus position.…”

Transcutaneous carbon dioxide monitoring in infants and children

“…Despite these applications, the correlation of ET‐CO 2 with P a CO 2 may be affected by several patient or monitor related factors such as patient positioning and alterations in ventilation–perfusion ratios (4–7). Other factors which may affect the accuracy of ET‐CO 2 monitoring include the smaller tidal volumes routinely used in infants and children, the site of ET‐CO 2 sampling, differences in the type of mechanical ventilation (intermittent vs continuous gas flow), and congenital heart disease with right‐to‐left extrapulmonary shunting (8,9).…”