| Abstract | [Abstract] Hemodynamic changes during controlled hypotension after administration of nitroglycerin (TNG) differ from the changes after nicardipine (NIC), but no previous investigations have analyzed the differences in waveforms. This study examined hemodynamic differences from radial artery wave contours obtained noninvasively by using tonometry. Twenty patients scheduled for elective surgery, 10 who received TNG and 10 who received NIC, were studied during general anesthesia under controlled hypotension with mean arterial pressure (MAP) maintained at approximately 60mmHg. We monitored the waveforms and recorded systolic arterial pressure (SAP), MAP and diastolic arterial pressure (DAP) and simultaneously measured central venous pressure (CVP) invasively. The LSW ratio (peak pressure of late systolic wave-DAP/SAP-DAP), EDW ratio (peak pressure of early diastolic wave-DAP/SAP-DAP), %MAP (MAP-DAP/ SAP-DAP × 100) and SVI (stroke volume index determined by tonometry using the modified Warner method)1) were calculated during five phases : phase 1 (stable point after incision) as a control, phase 2 (10 min after the start of hypotension), phase 3 (30 min after the start of hypotension), phase 4 (60 min after the start of hypotension), and phase 5 (30 min after the hypotension period), the recovery period. Hemodynamic changes showed that DAP was higher in phase 2, 3 and 4, CVP was lower in phase 2, 3, 4 and 5 and SVI was lower in phase 3 and 4 in the TNG group than in the NIC group. With regard to the waveforms, the LSW ratio was lower in phase 2, 3 and 4 and %MAP was lower in phase 2, 3, 4 and 5 in the TNG group, but there were no differences in the EDW ratio. It was concluded that the hemodynamic difference could be explained by the fact that, the wave contour difference after administering TNG was sharper due to reduction in the late systolic wave, possibly consequent to lower SVI, decreased velocity of the reflection wave, and the difference in the dilating action sites. |
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