Applied physiology at the bedside: using invasive blood pressure as a true monitoring tool

Invasive arterial blood pressure (BP) monitoring is a cornerstone of hemodynamic assessment in critically ill patients. This review explores how the individual components of BP-systolic arterial (SAP), diastolic arterial (DAP), mean arterial (MAP), and pulse pressure (PP)-offer valuable insights into cardiovascular physiology and can be leveraged as real-time therapeutic tools in intensive care settings. A strong emphasis is placed on the technical requirements for accurate BP waveform interpretation and the physiological meaning of each BP component. PP is examined as a surrogate for stroke volume and a dynamic marker of fluid responsiveness, particularly in mechanically ventilated patients. DAP is discussed as a reflection of vasomotor tone, with clinical implications for guiding the initiation of vasopressors. The concept of diastolic shock index (DSI) and the newly proposed VNERi ratio (DAP/[Heart rate × norepinephrine dose]) are introduced as potentially superior markers for assessing vascular tone and vasopressor responsiveness, respectively. These indices may facilitate earlier identification of patients requiring escalation of vasopressor therapy, including the initiation of vasopressin in addition to norepinephrine. The review advocates for a physiology-driven, individualized approach to hemodynamic management, using invasive BP not merely as a safety parameter but as an actionable guide for precision resuscitation.