Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2001
Clinical TrialThe relationship between plasma concentration of mature adrenomedullin and jugular venous oxygen saturation during and after cardiopulmonary bypass.
Adrenomedullin (AM), a vasodilatory peptide, increases during cardiac surgery. However, the physiological role of AM during cardiac surgery remains unclear. AM dilates cerebral arterioles and increases cerebral blood flow in rats. Therefore, we investigated whether AM is related to cerebral oxygen balance during cardiac surgery. In nine patients undergoing coronary artery bypass grafts, plasma concentrations of mature AM from the radial artery (mAMa) and jugular bulb (mAMj) were measured, and jugular venous oxygen saturation was obtained before surgery (baseline), before aortic cross-clamp (preclamp), after aortic declamp (postclamp), and 20 min after weaning from the cardiopulmonary bypass (post-CPB). Plasma concentrations of mAMa and mAMj were significantly increased at postclamp (P < 0.01 for both) and post-CPB (P < 0.01 for both) compared with baseline values. SjO(2) correlated with plasma mAMj concentrations at preclamp (r = 0.79, P < 0.01), postclamp (r = 0.71, P < 0.05), and post-CPB (r = 0.72, P < 0.05), as well as with mAMa concentrations at preclamp (r = 0.79, P < 0.01) and postclamp (r = 0.72, P < 0.05). This suggests a relationship between AM and cerebral oxygen balance during cardiac surgery. ⋯ Plasma concentrations of mature-form adrenomedullin, a vasodilatory peptide, was correlated with jugular venous oxygen saturation during cardiac surgery. This suggests a relationship between adrenomedullin and cerebral oxygen balance during cardiac surgery.
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Anesthesia and analgesia · Apr 2001
Comparative StudyVentilatory support by continuous positive airway pressure breathing improves gas exchange as compared with partial ventilatory support with airway pressure release ventilation.
In acute lung injury, airway pressure release ventilation (APRV) with superimposed spontaneous breathing improves gas exchange compared with controlled mechanical ventilation. However, the release of airway pressure below the continuous positive airway pressure (CPAP) level may provoke lung collapse. Therefore, we compared gas exchange and hemodynamics using a crossover design in nine pigs with oleic acid-induced lung injury during CPAP breathing and APRV with a release pressure level of 0 and 5 cm H(2)O. At an identical minute ventilation (V(E) 8 L/min) spontaneous breathing averaged 55%, 67%, and 100% of V(E) during the two APRV modes and CPAP, respectively. Because of the concept of APRV, mean airway pressure was highest during CPAP and lowest during APRV with a release pressure of 0 cm H(2)O. Shunt was reduced to almost half during CPAP (6.6% of Q(t)) compared with both APRV-modes (13.0% of Q(t)). Cardiac output and oxygen consumption, in contrast, were similar during all three ventilatory settings. Thus, in our lung injury model, CPAP was superior to partial ventilatory support using APRV with and without positive end-expiratory pressure. This may be attributable to beneficial effects of spontaneous breathing on gas exchange as well as to rapid lung collapse during the phases of airway pressure release below the CPAP level. These findings may suggest that the amount of mechanical ventilatory support using the APRV mode should be kept at the necessary minimum. ⋯ Oxygenation is better with continuous positive airway pressure breathing than with partial mechanical ventilatory support using airway pressure release ventilation. Therefore, mechanical ventilatory support achieved by a cyclic release of airway pressure during APRV should be kept at the minimum level that enables enough ventilatory support for patients to avoid respiratory muscle fatigue.