Assessment of short-term blood pressure variability in anesthetized children: a comparative study between...

Continuous blood pressure (BP) measurement provides instantaneous information on hemodynamic status, and allows for assessment of sympathetic modulation of vasomotor tone using spectral analysis. As an alternative to intraarterial blood pressure (IABP) measurement, the Finapres, a photoplethysmographic device, allows for non-invasive continuous measurement of finger blood pressure (FBP). This study was designed to evaluate the accuracy of spectral measurements of FBP variability in children during anesthesia and recovery. For this purpose, reliability of BP measurement and short-term BP variability assessed by FBP were calculated and compared with IABP.

Finger blood pressure was compared with IABP from the ipsilateral radial artery, in 14 children undergoing major surgery. Sixty-seven simultaneous recordings of both signals were performed during anesthesia and 32 during recovery period. The accuracy of the FBP was determined by measuring its bias and precision according to the Bland and Altman method. To assess the ability of the FBP to follow short term BP variability, bias of total spectral power and bias of the 3 main spectral components (LF, MF, HF) were calculated. Transfer functions between invasive and non-invasive signals were calculated.

The average bias of SBP measurement was 3.8 +/- 7.4 mmHg during anesthesia and 2.2 +/- 6.7 mmHg during recovery. During anesthesia overall variability and spectral components of FBP and IABP were similar with both techniques; while during recovery, a selective amplification of the low frequencies (< 0.15 Hz) of FBP was observed. Frequency response analysis of the pressure waveform, showed a high coherence between both signal with a gain of 0.96 +/- 0.52 mmHg FBP/ mmHg IABP under anesthesia, and of 0.74 mmHg FBP/ mmHg IABP during recovery.

The differences evidenced between FBP and IABP spectral profiles might result from specific physiological properties of digital arteries, which are sympathetic effectors. This study supports the use of FBP in children to assess non-invasively the vascular sympathetic component of the autonomic nervous system during anesthesia and recovery.