科研之友
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摘要
We investigated whether head up tilt (HUT) with and without simultaneous epinephrine infusion modulate plasma adrenomedullin. We studied eight healthy male volunteers, using two 5 min 70A degrees HUT trials: control (saline infusion) and intervention (epinephrine infusion, titrated to a dose which increased supine systolic pressure by 20% above resting values). Protocols were randomized and separated by 2 weeks. Cardiac function and systolic time intervals, recorded using a phonocardiograph microphone, included left ventricular ejection time (LVET), pre-ejection period (PEP), PEP/LVET and electromechanical systole (QS2). Compared to saline infusion, epinephrine increased supine adrenomedullin (3.2 +/- A 0.8 pmol/l, i.e., mean +/- A SEM, respectively), heart rate (HR) (+11.3 +/- A 2.6 bpm), systolic pressure (+18.4 +/- A 2.6 mmHg) but decreased supine LVET, LVET corrected for HR (LVETi) and QS2-time (all p = 0.004). Despite similar HUT induced thoracic fluid shifts, reflected by similar thoracic impedance changes, HUT-induced adrenomedullin increases were minimal in epinephrine-supplemented men in comparison to controls (+8% vs. 42%). During HUT, epinephrine infusion decreased only the LVET (p = 0.039). Our findings confirm that short-term HUT increases plasma adrenomedullin. They further suggest that with increased supine epinephrine levels (epinephrine infusion clamping systolic arterial pressure at 120% control level), supine cardiac performance rises to a level similar to that during HUT, while adrenomedullin is still elevated with HUT. This might be in accordance with a 'dampening' role of adrenomedullin during catecholaminergic cardiovascular stimulation. As epinephrine is used as a drug to treat cardiac arrest and ventricular arrhythmias, our results may have important clinical/emergency resuscitation applications.
- 出版日期2011-3
