Circulation research
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Circulation research · Oct 1989
Air trapping in the lungs during cardiopulmonary resuscitation in dogs. A mechanism for generating changes in intrathoracic pressure.
To test the hypothesis that during cardiopulmonary resuscitation, chest compression with an unobstructed trachea raises and maintains intrathoracic pressure by collapsing airways and trapping air in the lung, we studied 11 dogs (20-32 kg). An inflatable vest compressed the thorax after induction of ventricular fibrillation. First, tracheal airflow was measured by a pneumotachometer during vest inflation and deflation in nine of the dogs. ⋯ The change in right atrial pressure was higher on cycles after ventilation than on cycles without prior ventilation (79 +/- 12 vs. 67 +/- 12 mm Hg [mean +/- SEM], p less than 0.005), and lung volume was higher on cycles after ventilation (p less than 0.001). Next, a 5-Fr micromanometer was advanced down the airway in eight of the dogs. With the tip of the micromanometer 5-8 cm distal to the carina, a zone of high pressure was noted in seven dogs; this high pressure suggested a zone of airway collapse distal to the carina.(ABSTRACT TRUNCATED AT 250 WORDS)
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To investigate coupling between the heart and arterial system in normal subjects and cardiac patients, we determined both the slope of the left ventricular end-systolic pressure-volume relation (ventricular elastance) and the slope of the arterial end-systolic pressure-stroke volume relation (effective arterial elastance) in three groups of subjects: group A, 12 subjects with ejection fraction of 60% or more; group B, seven patients with ejection fraction of 40-59%; and group C, nine patients with ejection fraction of less than 40%. We also determined the left ventricular stroke work, end-systolic potential energy, and the ventricular work efficiency defined as stroke work per pressure-volume area (stroke work + potential energy). In group A, ventricular elastance was nearly twice as large as arterial elastance. ⋯ In group C, ventricular elastance was less than one half of arterial elastance, which resulted in increased potential energy and decreased work efficiency. Thus, the present study suggests that ventriculoarterial coupling is normally set toward higher left ventricular work efficiency, whereas in patients with moderate cardiac dysfunction, ventricular and arterial properties are so matched as to maximize stroke work at the expense of the work efficiency. Neither the stroke work nor the work efficiency is near maximum for patients with severe cardiac dysfunction.
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Circulation research · Jul 1988
Opiate receptor-mediated decrease in renal nerve activity during hypotensive hemorrhage in conscious rabbits.
Effects of hemorrhage on renal nerve activity and of subsequent opiate receptor blockade with naloxone were studied in conscious rabbits. Mean arterial pressure remained constant at 77 +/- 2 mm Hg through 17 +/- 2 ml/kg hemorrhage, while renal nerve activity increased by 159 +/- 16%. After 25 +/- 1 ml/kg hemorrhage, mean arterial pressure fell by 42 +/- 3 mm Hg, and renal nerve activity decreased below the prehemorrhagic control level by 41 +/- 15%. ⋯ To further examine the blocking effects of naloxone on changes in mean arterial pressure and renal nerve activity induced by exogenous opiate peptides, methionine-enkephalin was injected both in the control state and after treatment with naloxone. A bolus injection of methionine-enkephalin (10 micrograms/kg) decreased mean arterial pressure (-8.1 +/- 2.0 mm Hg) and renal nerve activity (-95 +/- 1%). Pretreatment with naloxone (0.5 mg/kg) effectively blocked this depressor effect and reduction in renal nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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Circulation research · Nov 1987
Comparative StudyGroup B streptococcal sepsis in the piglet: effects of fluid therapy on venous return, organ edema, and organ blood flow.
We investigated the physiologic effects of normal saline versus 5% albuminated saline fluid resuscitation on 10-12-day-old piglets infected with group B streptococci for four hours. After intravenously receiving 1 X 10(10) bacteria/kg over 45 minutes, one group was untreated while the two fluid-treated groups received enough intravenous fluid to maintain the baseline cardiac output. An increase in the resistance to venous blood return was the major limitation to cardiac output. ⋯ Organ edema formation (ileum, pancreas, kidney, adrenal gland, lung) occurred only in the saline-treated animals. We conclude that increased resistance to venous return was the primary cause of shock in our model and that this can be effectively treated by giving enough intravenous fluid to elevate the mean circulatory pressure. However, if the plasma protein oncotic pressure is also lowered (saline group), organ edema results.
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Circulation research · Oct 1987
Affinity purification of antibodies specific for 1,4-dihydropyridine Ca2+ channel blockers.
High-affinity antibodies specific for the 1,4-dihydropyridine Ca2+ channel blockers have been produced in sheep and affinity purified using a dihydropyridine-Sepharose affinity column. Dihydropyridine-Sepharose affinity matrix was synthesized by reaction of aminohexyl-Sepharose with an affinity analogue of nifedipine, dimethyl 1,4-dihydro-2,6-dimethyl-4-(2-isothiocyanatophenyl)-3,5-pyridine-dicarbo xylate. Residual amine groups were then blocked by carbodiimide-catalyzed acetylation. [3H]Nitrendipine-binding activity in serum was specifically absorbed by the dihydropyridine-Sepharose affinity column. ⋯ Thirty-six milligrams of highly pure IgG antibody, as demonstrated by sodium dodecyl sulfate-gel electrophoresis, was isolated from 50 ml hyperimmune sheep serum. The affinity-purified anti-dihydropyridine antibodies have been shown to have high affinity (Kd approximately 0.1 nM) and specificity for the 1,4-dihydropyridine Ca2+ channel blockers and, therefore, exhibit dihydropyridine-binding properties similar to the membrane receptor for the 1,4-dihydropyridine Ca2+ channel blockers. Immunoblot staining of an azidopine-bovine serum albumin conjugate with affinity-purified antidihydropyridine antibodies demonstrated that the anti-dihydropyridine antibodies recognize the 1,4-dihydropyridine Ca2+ channel blockers when covalently coupled to protein and, therefore, should be useful in the identification and purification of receptors covalently labelled with 1,4-dihydropyridine Ca2+ channel blockers.