Systolic Blood Pressure Variation and Causes
Systolic pressure variation is a non-invasive way to determine volume status and fluid responsiveness. Systolic pressure variation (SPV) is defined as the difference between the maximum and minimum values of systolic blood pressure following a single positive pressure breath. An increase in the SPV is known to occur clinically during hypovolemia. Systolic blood pressure fluctuates with spontaneously breathing, normally by 5-10 mmHg. Pulses paradoxes are a phenomenon in which the difference in systolic blood pressure (BP) between inspiration and expiration is more than 10 mmHg.
Pulse pressure variation (PPV) and systolic pressure variation (SPV) are reliable predictors of fluid responsiveness in patients undergoing controlled mechanical ventilation.
The systolic blood pressure normally increases at least to greater than 140 mm Hg with maximal exercise. The double product (maximal HR × maximal SBP) normally exceeds 20,000. A systolic blood pressure that does not exceed 140 mm Hg and a double product that does not exceed 10,000 suggest a poor prognosis. A drop in systolic blood pressure greater than 10 mm Hg after an initial rise indicates a very poor prognosis. One must however be aware of a pseudo drop in systolic blood pressure in the case of an anxious patient whose systolic blood pressure was excessively elevated at rest but “settled down” once the test began.43,70 An excessive increase in systolic blood pressure above 220 mm Hg suggests hypertension that has previously gone undiagnosed.
Systolic blood pressure rises during exercise. Diastolic blood pressure generally falls, or is unchanged. Age, gender, and racial differences in blood pressure are found in the general population. Using appropriate normal values is essential, therefore, when assessing the response of blood pressure response. As a general rule, it is uncommon for systolic blood pressure to exceed 200 mm Hg in healthy children. In the evaluation of children with suspected hypertension and a structurally normal heart, systolic blood pressure in excess of 250 mm Hg is usually grounds for terminating the test. Abnormal responses during exercise are seen with certain cardiac lesions. A blunted rise or fall in systolic blood pressure may indicate severe obstruction of the left ventricular outflow tract, or pulmonary hypertension.
CAUSES OF INCREASED SYSTOLIC PRESSURE VARIATION
- Constrictive pericarditis
- LV dysfunction
- Massive PE
- Dynamic hyperinflation
- Raised intrathoracic pressure
- Raised intra-abdominal pressure
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