Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler

Abstract

BACKGROUND: 

The objective of this study was to compare esophageal Doppler cardiac output (CO_EDM) against the reference method effective pulmonary blood flow cardiac output (CO_EPBF), for agreement of absolute values and ability to detect change in cardiac output (CO) in pediatric surgical patients. Furthermore, the relationship between these 2 methods and noninvasive blood pressure (NIBP) parameters was evaluated.

METHODS: 

Fifteen children American Society of Anesthesiology (ASA) I and II (median age, 8 months; median weight, 9 kg) scheduled for surgery were investigated in this prospective observational cohort study. Baseline CO_EPBF/CO_EDM/NIBP measurements were made at positive end-expiratory pressure (PEEP) 3 cm H₂O. PEEP was increased to 10 cm H₂O and CO_EPBF/CO_EDM/NIBP was recorded after 1 and 3 minutes. PEEP was then lowered to 3 cm H₂O, and all measurements were repeated after 3 minutes. Finally, 20-µg kg⁻¹ intravenous atropine was given with the intent to increase CO, and all measurements were recorded again after 5 minutes. Paired recordings of CO_EDM and CO_EPBF were examined for agreement and trending ability, and all parameters were analyzed for their responses to the hemodynamic challenges.

RESULTS: 

Bias between CO_EDM and CO_EPBF (CO_EDM − CO_EPBF) was −17 mL kg⁻¹ min⁻¹ (limits of agreement, −67 to +33 mL kg⁻¹ min⁻¹) with a mean percentage error of 32% (95% confidence interval [CI], 25–37) and a concordance rate of 71% (95% CI, 63–80). The hemodynamic interventions caused by PEEP manipulations resulted in significant decrease in CO_EPBF absolute numbers (155 mL kg⁻¹ min⁻¹ [95% CI, 151–159] to 127 mL kg⁻¹ min⁻¹ [95% CI, 113–141]) and a corresponding relative decrease of 18% (95% CI, 14–22) 3 minutes after application of PEEP 10. No corresponding decreases were detected by CO_EDM. Mean arterial pressure showed a relative decrease with 5 (95% CI, 2–8) and 6% (95% CI, 2–10) 1 and 3 minutes after the application of PEEP 10, respectively. Systolic arterial pressure showed a relative decrease of 5% (95% CI, 2–10) 3 minutes after application of PEEP 10. None of the recorded parameters responded to atropine administration except for heart rate that showed a 4% relative increase (95% CI, 1–7, P = .02) 5 minutes after atropine.

CONCLUSIONS: 

CO_EDM was unable to detect the reduction of CO cause by increased PEEP, whereas CO_EPBF and to a minimal extent NIBP detected these changes in CO. The ability of CO_EPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that CO_EPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children.