This prospective multicenter observational study aims to investigate the relationship between palpable peripheral pulses and simultaneously measured arterial blood pressure in adult patients with circulatory shock or impending circulatory failure. Peripheral pulse palpation is routinely used in emergency medicine, trauma care, critical care, and cardiopulmonary resuscitation as a rapid clinical assessment of circulation. However, the association between palpable pulses and actual arterial blood pressure remains poorly validated.

Patients treated in emergency departments, intensive care units, operating rooms, and other acute care settings will undergo routine pulse palpation at predefined anatomical locations including carotid, femoral, and radial arteries. Simultaneously measured non-invasive and/or invasive arterial blood pressure values will be recorded from routine clinical monitoring systems. Additional clinical variables relevant to circulatory status will also be collected.

The study seeks to define blood pressure thresholds associated with pulse palpability and evaluate the agreement between invasive and non-invasive blood pressure measurements in patients with circulatory shock.

The presence or absence of palpable peripheral pulses is widely used as a rapid bedside indicator of circulatory status during trauma care, emergency medicine, intensive care, and cardiopulmonary resuscitation. Advanced Trauma Life Support (ATLS) teaching traditionally assumes that palpable pulses at different anatomical sites correspond to specific systolic blood pressure thresholds. However, these assumptions are based on limited evidence from small observational studies.

This international multicenter prospective observational cohort study aims to investigate the relationship between palpable carotid, femoral, and radial pulses and simultaneously measured arterial blood pressure in adult patients with circulatory shock or impending circulatory failure.

Patients receiving routine hemodynamic monitoring with non-invasive blood pressure (NIBP) and/or invasive arterial blood pressure (IBP) monitoring will be included. Pulse palpation will be performed during routine clinical care without altering treatment or management.

The primary objective is to determine the association between pulse palpability and measured systolic blood pressure. Secondary objectives include identifying blood pressure thresholds associated with pulse palpability, evaluating agreement between invasive and non-invasive blood pressure measurements, and assessing whether patient factors such as vascular disease or vasoactive medication use influence pulse palpability.

Inclusion Criteria:

• Clinical signs of circulatory shock or impending circulatory failure
• Availability of non-invasive and/or invasive arterial blood pressure monitoring
• Pulse palpation possible without interfering with emergency care

Exclusion Criteria:

• Peripheral vascular conditions preventing reliable pulse palpation
• Major extremity amputation affecting assessment sites
• Clinical situations where study procedures interfere with life-saving treatment

Adult patients with circulatory shock or impending circulatory failure treated in emergency departments, intensive care units, operating rooms, trauma centers, and other acute care settings.

Data sharing plans are currently undecided due to ongoing considerations regarding ethical approvals, multicenter collaboration agreements, and data protection regulations.