摘要:

Bronchocutaneous fistula (BCF) can originate at different levels, from the major airways to the peripheral lung. Little is published on the influence of the fistula origin or the ventilatory effect of the airleak. This study evaluates relative CO2elimination via fistulas of various size and how different ventilatory modes influence both the quantity and quality, i.e., oxygen and CO2content, of the airleak. We created BCF with five polyethylene tubings of different diameters (tube 1, 3.0 mm; tube 2, 4.0 mm; tube 3, 5.1 mm; tube 4, 6.4 mm; tube 5, 9.8 mm) in nine dogs. Six modes of ventilation were used with each tubing: spontaneous breathing (SB), pressure support (PS), high frequency (HF), assisted controlled with inspiration set at 20% (AC20) and at 67% (AC67) of the respiratory cycle, and AC20 with an end-expiratory pressure of +10 cm H2O (PEEP). For each ventilatory mode, the fistula air flow (Vf), CO2, and oxygen partial pressure of fistula air (Pfco2and Pfo2) and arterial blood were measured. Vf was measured for all tubes, while gas analysis was done for tubes 1, 3, and 5 only. As expected, VF increased with tubing size. Vf was higher with AC67 and PEEP than with the other ventilatory modes. Pfco2was not significantly influenced by the tube size and Vf. Fistula air alveolization was increased only with HF ventilation. Air leaked via the fistula contributed significantly to gas exchange: even when expiration was totally via the fistula, the arterial gases remained unchanged. We conclude that: a) ventilatory modes which increase airway pressures, such as PEEP and AC67, increase the fistula air flow; b) the airway level of a fistula does not influence its major contribution to gas exchange; and c) HF ventilation may increase the alveolization of air leaked through a fistula.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We studied the effect of iv administration of biodegradable macromolecules on microvascular permeability after ischemia-reperfusion injury in a rat gastrocnemius model. After 2 h of tourniquet ischemia of the rats' hind limb, groups of animals were given iv lactated Ringer's solution (RL), serum albumin 5%, or varying MW fractions of biodegradable macromolecules of hydroxyethyl starch (HES), glycogen, and dextran. At the conclusion of the 24-h reperfusion period, the rat gastrocnemius muscles were collected. Water and K+differences between the ischemic and control muscles were compared. Rats given a 100,000 to 300,000-dalton fraction of HES had significantly decreased water content (5.1 ± 3.4%) when compared to rats receiving RL (8.3 ± 2.2,p< .01). <100,000 dalton HES (8.3 ± 3.2,p< .05), <300,000 glycogen (7.9 ± 2.5,p< .01), or dextran 150,000 (8.3 ± 1.5,p< .05). Rats given 100,000 to 300,000-dalton HES also had significantly higher ischemic muscle K+content as compared to the nontourniquet control (difference 14.2 ± 9.7 mEq/g) than rats receiving any of the other solutions (range 32.5 to 39.5) except the 300,000 to 1,000,000-dalton fraction of HES. Regression analysis comparison of K+difference to the histologic evaluation of the muscles on the criteria of polymorphonuclear infiltration and interstitial edema (0, best; 3, worst) had a Pearson correlation coefficient of r = .73. Reduction of abnormally increased microvascular permeability may be accomplished by the iv use of appropriate sized biodegradable macromolecules.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Previous studies have indicated that methoxamine (an α adrenergic receptor agonist) may provide an advantage compared to epinephrine (a mixed α and β adrenergic agonist) during cardiac arrest and CPR. To test this theory, we compared the effects of bolus injections of epinephrine vs. methoxamine on survival, hemo-dynamic variables, blood gases, and blood lactate concentrations during ventricular fibrillation and CPR in 12 dogs. Each dog underwent a 3-min fibrillatory arrest followed by 10 min of fibrillation and CPR, at which time the animals were defibrillated. Epinephrine (0.05 mg/kg, n = 6) or methoxamine (2 mg/kg, n = 6) was administered at the start of CPR. Both epinephrine and methoxamine produced identical survival rates (5/6) with no differences in coronary perfusion pressure gradients or blood gases (aortic, venous, or great cardiac venous pH, Pao2, or Paco2) during CPR. Also, there were no differences between the two study groups in myocardial lactate or oxygen extraction ratios during CPR. We conclude that in the dosages tested in our experimental model, epinephrine and methoxamine produce similar results in the variables which we measured.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The aim of the present study was to determine possible effects ofEscherichia coliendotoxin on peripheral vascular compliance and relate them to concomitant central hemodynamic disturbances. Endotoxin was infused at 0.25 μg/kg-min during 2 h in six anesthetized dogs, while six additional animals served as controls. Vascular compliance of the systemic circulation was calculated in intact animals from the changes in CVP after known changes in systemic blood volume. In control dogs, vascular compliance averaged 2.3 ml/mm Hg-kg body weight. During slow endotoxin infusion, cardiovascular effects were measurable only after a certain period of time had elapsed from the start of endotoxin insult and consisted of hypotension associated with systemic vasodilation. Systemic BP decreased gradually from 124 to 68 mm Hg while vascular compliance was finally increased by 100%, when compared to control values. This latter rise was responsible for a reduction in the cardiac preloads. Pulmonary wedge pressure and CVP were decreased from 7.1 to 3.4 and from 4.5 to 2.6 mm Hg, respectively. However, parallel to the decrease in left ventricular preload, endotoxin induced a progressive decrease in left ventricular afterload. Because of the balance in ventricular loading, cardiac output remained almost unchanged. After volume loading (dextran 30 ml/kg), cardiac output was remarkably increased from 3.28 to 6.24 L/min-m2while peripheral vasodilation was not affected by this maneuver.It is concluded that low dose endotoxin infusion induces in dogs a hemodynamic pattern similar to human sepsis. The left ventricular loading changes are related to an enhanced systemic vascular compliance from 2.3 to 4.5 ml/mm Hg-kg. High flow shock slate is encountered provided peripheral blood pooling is compensated by adequate volume replacement.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effects of iv sodium bicarbonate (NaHCO3) and Carbicarb®, an experimental buffer, were compared in a rat model of lactic acidosis induced by controlled hemorrhage and asphyxia. Although both NaHCO3and Carbicarb were effective at alkalinizing the arterial blood in this model, NaHCO3administration resulted in a rise in Paco2where Carbicarb did not (+9 ± 2 vs. +2 ± 2 torr at 2 min after infusion,p< .01). Moreover, NaHCO3resulted in a small decrease in intracellular brain pH as measured with P-31 nuclear magnetic resonance where Carbicarb afforded intracellular brain alkalinization (-0.03 ± 0.01 vs. +0.08 ± 0.02 pH units at 2 min,p< .01). If these data are confirmed clinically. Carbicarb may offer advantages over NaHCO3under conditions of fixed or limited ventilation.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We studied the inotropic effect of the α-agonist phenylephrine on human and rat myocardium in relation to age. Strips of human atrial myocardium, discarded during cardiac surgery, were obtained from pediatric (2 to 18 months) and adult (40 to 60 yr) patients, and their electrically driven contractions were studied. The inotropic response of pediatric myocardium to phenylephrine was five times larger than that of the adult myocardium (p< .05). The β-agonist, isoproterenol, was also administered to the same myocardial specimens, and the average pediatric myocardial response was three times larger than that of the adult myocardium (p< .05). Strips of right ventricular myocardium were obtained from four age groups of rats: 14 days, 3 months, 6 months, and 18 months, and exposed to phenylephrine. We demonstrated two age-related phenomena: a) a biphasic response with an early short negative inotropic effect preceding a sustained positive inotropic effect was registered in most of the rats aged 3 months and older, but in none of the youngest age group, b) A high mean positive inotropic response (211% of basal response) was generated in the youngest age group, whereas the oldest age group of rats showed only a slight response (8% of basal response,p< .05). We conclude that loss of myocardial responsiveness to α and β-agonist with increasing age is a prominent feature. The pattern of the ventricular responsiveness to phenylephrine also changes during aging as it turns from monophasic to biphasic.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Current methods of assessing cerebral blood flow (CBF) are limited in their ability to provide data at the bedside in a timely, inexpensive, and continuous fashion. Since the palpebral conjunctiva is perfused by branches of the internal carotid artery, perfusion of this tissue may reflect global CBF. Conjunctival oxygen tension (Pcjo2). Pao2, Paco2, and pH were measured in ten healthy subjects during normal ventilation and active hyperventilation. CBF was measured simultaneously using positron emission tomography. CBF decreased from an average of 64.3 ± 15.1 ml × 100 g−1× min−1during baseline measurements to 33.2 ± 8.4 ml × 100 g−1× min−1during hyperventilation. The ratio of Pcjo2to Pao2(the Pcjo2/Pao2index) decreased from 0.53 ± 0.07 to 0.35 ± 0.09 in the same time period. The Pcjo2/Pao2index was significantly correlated with CBF (r = .78,p< .001). We conclude that the Pcjo2/Pao2index may reflect the reduction in CBF induced by hyperventilation in normal humans, and should be investigated further as a method of assessing CBF in other settings which can result in globally reduced cerebral perfusion.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Studies in adults suggest a possible association between pulmonary nosocomial infection and bacterial adherence to endotracheal tubes (ETT). Some strains of coagulase-negative Staphylococcus produce a mucoid extracellular material known as slime or glycocalyx that helps bacteria adhere to the surface of biomaterials. We examined by scanning and transmission electron microscope the surface of 29 polyvinyl ETT removed from neonatal patients, and ten unused ETT. Multiple surface irregularities were found in the unused tubes. These irregularities were most prominent in the tip and around the side hole. Amorphous material containing slime-producing bacteria was found on 29 ETT removed from patients. Tubes in place for longer times had greater areas of surface covered; the amorphous material was more concentrated in the areas where surface irregularities were most prominent. No clinical correlation with pulmonary noscomial infection was established.

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1989

数据来源: OVID