The effects of the oxygen flow rate on heart rate variability in the PACU after TIVA

ABSTRACT

BACKGROUND: Oxygen increases the cardiac vagal tone, blood pressure, systemic vascular resistance and vascular tone in healthy adults.This study assessed the autonomic tone according to different oxygen flow rates via different types of masks with using the heart rate variability (HRV) in the PACU after total intravenous anesthesia (TIVA). METHODS: We prospectively studied 27 patients after TIVA in the PACU.The 5 L group received oxygen via a simple mask with an oxygen rate of 5 L/min and the 10 L group received oxygen via a mask with a reservoir bag at a rate of 10 L/min in the PACU. We evaluated the HRV at the point of stabilization before anesthesia (BL), 5 min in the PACU (PACU 5), 30 min in the PACU (PACU 30) and 60 min in the PACU (PACU 60). RESULTS: In the 5 L group, the nuHF was increased to 42.4 +/- 24.2 at 60 min in the PACU as compared with 27.1 +/- 19.1 at 5 min in the PACU.In the 5 L group, the LFHFr was decreased to 2.3 +/- 2.1 at PACU 60 as compared with 6.6 +/- 9.7 at PACU 5 and the nuLF was decreased to 56.9 +/- 23.2 at PACU 60 as compared with 72.9 +/- 19.0 at PACU 5.There were no significant changes between the two groups at PACU 5, PACU 30 and PACU 60.The oxygen saturation was increased at PACU 60 compared with PACU 5 in the two groups. CONCLUSIONS: These finding indicates that 1 h of oxygen administration with 5 L/min during emergence from anesthesia increased the relative vagal tone, and the arterial blood pressure is stable irrespective of the oxygen flow rate.