Time-Dependent Changes in Pulse Wave Transit Time Following Infraclavicular Block: A Non-Invasive Assessment of Sympathetic Blockade

Regional anesthesia success is traditionally assessed using sensory and motor block evaluation methods that rely on patient cooperation and subjective responses to external stimuli. However, these methods may be difficult to apply in sedated, uncooperative, or communication-impaired patients. Therefore, objective and non-invasive indicators of sympathetic blockade have gained increasing interest in regional anesthesia practice.

Pulse Wave Transit Time (PWTT) is defined as the time interval between the R-wave on the electrocardiogram and the arrival of the corresponding pulse wave detected by a peripheral pulse oximeter. PWTT reflects vascular tone, arterial compliance, and hemodynamic status. Sympathetic blockade induced by peripheral nerve blocks results in vasodilation and reduced vascular resistance, potentially leading to measurable changes in PWTT. Previous studies have demonstrated the utility of objective parameters such as perfusion index, skin temperature, blood flow measurements, and PWTT in assessing block success. However, data regarding the temporal changes of PWTT following infraclavicular brachial plexus block remain limited.

The primary objective of this prospective observational study is to investigate the time-dependent changes in PWTT after ultrasound-guided infraclavicular brachial plexus block. The study will be conducted in patients undergoing upper extremity surgery under infraclavicular block at Sakarya Training and Research Hospital.

Patients scheduled to receive infraclavicular block as part of their routine clinical care will be enrolled after providing informed consent. The block procedure is not performed for research purposes and represents standard clinical practice. Following block administration, PWTT values will be recorded from the blocked extremity using standard monitoring equipment. Measurements will be obtained before block placement and at 0, 5, 10, 15, and 20 minutes after block completion. Baseline PWTT measurements will also be obtained from the contralateral upper extremity.

Secondary outcome measures will include perfusion index, skin temperature of both upper extremities, heart rate, non-invasive blood pressure, respiratory rate, and oxygen saturation. Demographic and clinical data will also be recorded.