The Journal of surgical research
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Extravascular lung water (EVLW) can be measured using the double indicator dilution technique (DD). However, because this method is highly invasive and complicated, its clinical used has been limited. In theory, changes in thoracic conductivity, or bioimpedance (BI), can reflect changes in EVLW. ⋯ In early sepsis (30 min), BI overestimated EVLW when compared with DD (P less than 0.05). However, at 1, 2, and 4 hr there was no significant difference between the two methods. In conclusion, the use of bioimpedance and a volumetric catheter may provide a relatively simple and reliable method for continuously monitoring changes in EVLW in the intensive care setting.
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Management of major blood loss utilizing protein-free fluids for volume replacement frequently results in plasma protein depletion and plasma volume expansion. These factors can increase pulmonary transvascular fluid filtration which may lead to life-threatening pulmonary edema. We studied the combined effects of plasma protein depletion and plasma volume expansion on lung lymph flow (QL) in awake sheep prepared with chronic lung lymph fistulae. ⋯ We did not observe this with LR infusion, or in previous studies employing intravenous infusion of plasma protein. Thus, the oncotic pressure of Hespan appears to significantly limit pulmonary fluid filtration during hypoproteinemia compared to LR. We do not believe that these effects are the results of any changes in microvascular porosity.
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The use of hypothermia in cardiac and neurologic surgery is well established, but its use in treating hemorrhagic shock is controversial. Using a modified Wiggers hemorrhagic shock model, we examined the effects of hypothermia (group 1, 33 degrees C, N = 7; group 2, 28 degrees C, N = 12) after inducing hemorrhagic shock. In group 3, N = 6, dogs were maintained at body temperature in hemorrhagic shock and throughout resuscitation (normothermic shock). ⋯ Left ventricular end-diastolic pressure was lower in the severely hypothermic dogs while stroke volume was higher in this group. Rewarming ablated all differences in cardiovascular performance and acid-base balance. Our data show that moderate hypothermia during hemorrhagic shock increased coronary perfusion, enhanced cardiac contractile performance, and significantly reduced myocardial oxygen requirements.(ABSTRACT TRUNCATED AT 250 WORDS)
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Currently, accurate measurements of extravascular lung water (EVLW) are obtained using the double dye dilution technique (DD). However, this method is invasive and complicated and has limited its clinical use. The purpose of this study was to develop a noninvasive method for determining changes in EVLW using bioimpedance (BI) and compare these measurements with DD in a model of acute pulmonary injury. ⋯ There was no difference in computed EVLW using DD and BI at 15, 30, and 60 min following oleic acid infusion (P greater than 0.35). CO was significantly correlated using DD and BI (r = 0.81, P less than 0.05). In summary, bioimpedance may hold promise as a noninvasive and continuous means for estimation of EVLW in the critical care setting.
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Phenylephrine is frequently used to increase systemic arterial pressure during carotid endarterectomy. However, little is known of its effect on collateral cerebral perfusion pressure, particularly in patients with high collateral cerebral vascular resistance who are at increased risk of cerebral ischemia during carotid clamping. We tested the hypothesis that this subset of patients can have collateral perfusion pressure, and hence collateral cerebral blood flow, increased in a predictable way by elevating systemic arterial pressure. ⋯ Unchanged were Pv = 8.2 +/- 4.1 (5%) and Rc/Rh = 3.5 +/- 1.30 (3%) (P greater than 0.8). The latter two findings indicate that cerebral perfusion pressure and mean systemic arterial pressure are linearly related according to the fluid mechanics equation governing these parameters: Pa = P(Rc/Rh + 1) + Pv. These results support the use of phenylephrine to increase collateral blood flow during carotid endarterectomy in patients with low cerebral perfusion pressure.