Pulse pressure
Formal Definition
The arithmetic difference between systolic and diastolic blood pressure (systolic − diastolic), reflecting stroke volume and arterial compliance; a narrow pulse pressure (<25 mmHg) suggests low cardiac output, while a widened pulse pressure (>60 mmHg) suggests aortic regurgitation, septic shock, or thyrotoxicosis.
How It's Used on the Ward
"Pulse pressure is narrow" — often mentioned during shock assessment. A narrowing pulse pressure with tachycardia is an early warning of impending hemodynamic collapse.
Example
""Trauma bay: BP 100/80 with HR 130. Pulse pressure 20 — that's narrow. Classic early hemorrhagic shock: vasoconstriction maintaining diastolic while systolic falls. Two large-bore IVs, type and cross, activate massive transfusion protocol.""
Clinical Context
Pulse pressure narrows before systolic BP drops significantly in early shock — the body compensates by vasoconstriction, which raises diastolic and narrows the gap. A patient with BP 100/80 is in worse shape than BP 100/60. Widened pulse pressure: septic shock (vasodilation drops diastolic), aortic regurgitation (diastolic leak), hyperthyroidism, severe anemia, AV fistula. Knowing this helps recognize shock earlier.