Photoplethysmographic measurement of changes in total and pulsatile tissue blood volume, following sympathetic blockade

Abstract

Epidural anaesthesia, used for pain relief, is based on blocking the sensory and the sympathetic nerves in the lower part of the body. Since the sympathetic nervous system regulates blood vessel diameter, the sympathetic block is also associated with several haemodynamic changes. In the current study photoplethysmography (PPG) was measured on toes and fingers of patients undergoing epidural anaesthesia. Three parameters, which are related to the change in total and pulsatile tissue blood volume, were derived from the PPG baseline and amplitude. All parameters showed statistically significant increase in the toes after the sympathetic block, indicating higher arterial and venous blood volume and higher pulsatile increase in the arterial blood volume (higher arterial compliance) in the toe. These haemodynamic changes originate from the lower tonus of the arterial and venous wall muscles after the sympathetic block. In the fingers the PPG parameters based on the change in PPG amplitude decreased after the sympathetic block, indicating lower compliance. The measurement of the haemodynamic changes by PPG enables the assessment of the depth of anaesthesia, and can help control the adverse effects of the blockade on the vascular system.

Sympathectomy-mediated vasodilatation: a randomized concentration ranging study of epidural bupivacaine

“…16 Previous reports from our group suggest that the PI is a more reliable and a more sensitive marker of sympathectomyrelated vasodilatation than either blood pressure changes or cutaneous temperature changes. 18,19 The PPG sensor in this study was a pulse oximetry sensor probe (N-25 oxisensor II, Nelcor Puritan Bennett Inc., Pleasanton, CA, USA), wherein we only used the infrared light source and the photo detector. The PPG waveform was measured on the patient's second toe and on the index finger.…”

Long-lasting effect of subliminal processes on cardiovascular responses and performance

“…Pulse transit time has been shown to shorten during difficult tasks (e.g., Duschek et al, 2009;Kemper et al, 2008;Tomaka et al, 1993). Finally, pulse wave amplitude is mainly influenced by the sympathetic nervous system (see Babchenko et al, 2001; for a review of pharmacological demonstrations) without influence of the parasympathetic nervous system and reflects mainly α-adrenergic activity (Gayton, 1977). A decrease of pulse wave amplitude (i.e., peripheral vasoconstriction) has been reported in performing difficult tasks (Iani et al, 2004;.…”

Photoplethysmographic signals to predict the success of lumbar sympathetic blockade for lower extremity pain

“…After initiation of LSB, blood volume increases as a consequence of vasodilatation in both arteries and veins. 34 The time between the initiation of AC signal change and temperature change was $180 s in the present study.…”

“…35 The findings of the current study suggest that PPG AC signals may be used as an early indicator of successful LSB. 34,36 The slowly varying PPG DC signals in the 0.01-0.40 Hz range are related to sympathetic nervous system activities, including relative vascularization and blood pooling within the sampling site.…”