Comparison of intra-arterial and indirect blood pressures at rest and during isometric exercise in hypertensive patients before and after metoprolol.

1. Blood pressure was measured both directly and indirectly in seven hypertensive patients before and after a single oral dose of 100 mg metoprolol, at rest and during sustained handgrip. 2. Intra-arterially measured systolic and diastolic blood pressure increased linearly with time during sustained handgrip at 50% of maximal voluntary contraction. This linearity persisted for 60 s or more in most cases. Heart rate increased linearly for the first 30 s. 3. Indirectly measured blood pressure using an observer bias minimizing Auto-Manometer, under-read systolic and over-read diastolic pressure both at rest and during handgrip. 4. By exact timing of recorded values during handgrip and linear extrapolation (or interpolation) from base-line readings, mean values at 30 and 60 s of handgrip were calculated. The relationship between direct and indirect values remained the same at base-line and 30 s of handgrip. At 60 s of handgrip, this was true only for diastolic pressure. For systolic pressure, indirect and direct values almost coincided. 5. After metoprolol, directly recorded pressure fell slightly (7--12 mm Hg, 0.02 less than P less than 0.10), both at rest and during handgrip, and heart rate fell by 15--18 beats/min (P less than 0.01). The systolic blood pressure and heart rate effect of metoprolol at 1 min handgrip correlated with peak plasma drug levels. Indirectly measured blood pressure did not change significantly. 6. The rate of rise in heart rate and blood pressure from base-line to 60 s handgrip was not significantly influenced by metoprolol.