摘要:

Objective:To evaluate the effect of acute hypercapnia on regional myocardial blood flow in a swine model of chronic, single-vessel coronary artery obstruction. Permissive hypercapnia is being used frequently in critical care settings. One possible detrimental effect of hypercapnia is the initiation of coronary "steal" in patients with coronary artery disease. The effects of hypercapnia on collateral coronary blood flow in the setting of coronary obstruction have not been defined.Design:Prospective controlled experimental study.Setting:Institutional animal research facility.Subjects:Eight juvenile swine weighing 25-30 kg.Interventions:Collateral coronary circulation was induced in eight piglets by banding the proximal left anterior descending coronary artery for 8-10 wks followed by total ligation. Graded hypercapnia (mean PaCO2, 81 torr [10.80 kPa; PaCO2= 81 torr] and 127 torr [16.93 kPa; PaCO2= 127 torr]) was induced by increasing inspiratory carbon dioxide under isoflurane anesthesia (1 minimum alveolar concentration).Measurements and Main Results:Animals were attached to instruments to measure pulmonary and systemic hemodynamics, regional myocardial blood flow, and cardiac output. Regional myocardial blood flow was determined using radiolabeled microspheres. Cardiac output, mean arterial pressure, and coronary perfusion pressure were unchanged at both levels of hypercapnia compared with baseline values. Heart rate was increased at PaCO2 [HI](p< .05). Regional blood flow was increased at both levels of hypercapnia in the collateral-dependent and normally perfused myocardium (p< .05; as high as 56% for subendocardium and as high as 106% for subepicardium at PaCO2 [HI]). The intercoronary blood flow ratio remained unaltered. The transmural flow ratio was reduced at PaCO2 [HI](p< .05). During hypercapnia, regional lactate extraction remained unaltered, and regional oxygen extraction was unchanged or reduced despite the increase in oxygen consumption.Conclusions:In this swine model of chronic single-vessel coronary artery obstruction, acute hypercapnia does not induce coronary steal from collateral-dependent myocardium, but it does increase global coronary blood flow.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To compare the vascular reactivity of the renal circulation in control and septic conditions.Design:Prospective, randomized, controlled animal study.Setting:University research laboratory.Subjects:Anesthetized pigs (n = 17).Interventions:Ten pigs received a continuous intravenous infusion of endotoxin fromEscherichia coli(160 ng·kg−1·hr−1) during 18 hrs, whereas seven control animals received a saline infusion. To test the vascular reactivity, norepinephrine (NE) (1 μg·kg−1), acetylcholine (10 μg·kg−1), and sodium nitroprusside (10 μg·kg−1) were intravenously injected for 20 secs and changes of mean arterial pressure and renal blood flow were observed during the 200 secs after the drug administration. To compare the evolution of the vascular reactivity over time, three tests were performed 5 hrs, 11 hrs, and 17 hrs after initial endotoxin or saline administration.Measurements and Main Results:Endotoxin infusion induced a hypotensive and hypokinetic syndrome with renal hypoperfusion. The mean arterial pressure increase after NE injection and the mean arterial pressure decrease after acetylcholine and nitroprusside were lower in endotoxin than in control pigs. In the renal circulation, the increase of resistance after NE injection and the decrease of renal resistance after acetylcholine and nitroprusside injections were lower in endotoxin than in control pigs.Conclusions:This study shows a hyporesponsiveness of the renal circulation to vasoactive agents during endotoxemia. Vasoconstriction to NE, endothelium-dependent as well as endothelium-independent relaxations are altered during endotoxemia but not abolished, and despite the continuous infusion of endotoxin for 18 hrs, no recovery was observed over time.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To determine whether partial liquid ventilation (PLV) affects the risk of nosocomial pneumonia.Study Design:To assessin vitrobacterial adhesion and viability after liquid perfluorocarbon exposure and to assess bacterial recovery after partial liquid ventilationin vivoin rabbits.Setting:University animal research facility.Subjects:Thirty-six New Zealand White rabbits.Interventions:To assess adhesions, radiolabeledEscherichia coliwere exposed to perfluorocarbon, incubated against artificial biosurfaces, and compared with nonexposed controls. Bacterial viabilityin vitrowas assessed by exposing broth suspensions ofPasteurella multocidato perflubron for various times. Controls were run in parallel without exposure. Quantitative cultures were performed to determine viability. We undertook short-term and recoveryin vivoinvestigations. The lungs of treated animals were filled with perflubron (∼18 mL/kg), and the control rabbits were ventilated without perflubron in an identical fashion. Cryopreserved aliquots ofP. multocidawere administered via an endotracheal tube. The short-term study animals were ventilated for 6 hrs before being killed. The recovery animals were ventilated for 2-4 hrs, extubated, and killed 20 hrs later. The lungs were removed, aseptically minced, and homogenized. Serial dilutions of the homogenate were quantitatively cultured by manual counting of colonies on agar plates. The recovered organisms were typed for species by the clinical microbiology laboratory.Measurements and Main Results:The adhesion of bacteria to immobilized bronchoalveolar lavage and human saliva, respectively, was reduced by 65% ± 7% and 66% ± 1% (p< .05; n = 5) after exposure to perflubron and by 63% ± 9% and 68% ± 6% after exposure to FC-77 (p< .05; n = 5); however, adhesion was not affected by exposure to Rimar. There was no difference in bacterial viability between the control and perflubron-exposed bacteria (n = 5). Thein vivostudy demonstrated a ten-fold or greater reduction in the number of recovered bacteria in the partial liquid ventilated group compared with the control group.Conclusions:This study suggests that different perfluorocarbons affect adhesions differently. Perflubron and FC-77 appear to decrease bacterial adhesion, whereas Rimar does not. Rerflubron does not have a direct bactericidal effect. Furthermore, PLV with perflubron decreased the number of viable bacteria per gram of tissue after an intentional inoculation of the airway, suggesting that the risk of nosocomial pneumonia is unlikely to be increased during PLV and may, in fact, be reduced in patients supported with PLV.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To compare the efficacy of intravenous and endotracheal epinephrine administration, and intravenous administration above and below the diaphragm, during cardiopulmonary resuscitation in newborn piglets.Design:Prospective, randomized, experimental laboratory protocol.Setting:Perinatal cardiovascular research laboratory at a university school of medicine.Subjects:Forty newborn piglets (Sus domesticus).Interventions:After cardiac arrest by ventricular fibrillation, cardiopulmonary resuscitation was begun. Radiolabeled epinephrine or placebo (0.9% sodium chloride) was administered into the right atrium, femoral vein, or endotracheal tube. Chest compressions and ventilation were continued for 10 mins.Measurements and Main Results:After epinephrine or placebo administration, samples were obtained from the systemic arterial circulation for measurement of radioisotope activity and plasma epinephrine concentrations. Mean carotid arterial blood pressure, right atrial, and inferior vena caval pressures were measured continuously. Epinephrine administration via the right atrium and femoral vein resulted in significant increases in plasma epinephrine concentration, percent of radioisotope recovery, and mean carotid arterial blood pressure, whereas endotracheal epinephrine administration did not. Placebo administered into the femoral vein resulted in a significant increase in percent radioisotope recovery, but not in plasma epinephrine concentration or carotid arterial blood pressure. Endotracheal administration of placebo did not result in significant increases in plasma epinephrine concentration, percent radioisotope recovery, or carotid arterial blood pressure. There were no significant differences between right atrial or inferior vena caval pressures among the groups.Conclusions:During cardiopulmonary resuscitation in newborn piglets, intravenous administration of epinephrine is more efficacious than endotracheal administration. Furthermore, efficacy is similar between femoral venous and right atrial administration.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:In this study, we evaluated the spasmolytic effect of intravenous prostaglandin (PG) E1on histamine-induced bronchoconstriction with a direct visualization method using a superfine fiberoptic bronchoscope.Setting:A university research laboratory.Subjects:Mongrel dogs.Interventions:The bronchial cross-sectional area (BCA) of mongrel dogs was measured by a direct visualization method using a superfine fiberoptic bronchoscope. Bronchoconstriction was elicited with histamine (H) infusion: 10 μg/kg iv bolus + 500 μg/kg/h continuous iv. The first protocol (n = 7) was designed to determine the effects of intravenous bolus of PGE1: 0 (saline), 0.01, 0.1, 1.0 and 10 μg/kg on H-induced bronchoconstriction. BCA was assessed before and 30 min after starting the H infusion and 5 min after each dose of intravenous PGE1. The second protocol was designed to determine whether continuous intravenous infusion of PGE1reverses H-induced bronchoconstriction. In the PG group (n = 6), PGE1was continuously infused at 0.1 μg/kg/min (20 mL/hr). In the control group (n = 6), saline was administered at a rate of 20 mL/hr iv. BCA was assessed before and 30 min after starting the H-infusion and at 5, 10, 30 and 60 min after commencing the PGE1or saline infusion. Arterial blood was obtained simultaneously for measurement of plasma concentrations of epinephrine and norepinephrine by gas chromatography mass spectrometry.Measurements and Main Results:In the first protocol, PGE1produced a dose-dependent increase in the percentage of BCA and 10 μg/kg of PGE1almost fully reversed the H-induced bronchoconstriction. Plasma catecholamines did not change significantly. In the second protocol, continuous infusion of PGE1produced a time-dependent reversal of H-induced bronchoconstriction (percentage of BCA increased to 80.0 ± 9.0% 60 min after the start of PGE1infusion), whereas saline infusion did not reverse the bronchoconstriction. Plasma catecholamines did not change significantly in either group.Conclusions:Both intravenous bolus and continuous intravenous infusion of PGE1reversed the H-induced bronchoconstriction. PGE1may be used safely for patients with the hyperreactive airway and might be useful as a therapeutic agent for these patients.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objectives:By accounting for influences of systemic acid-base disturbances, gut mucosal-arterial PCO2gradient (PiCO2- PaCO2) has been increasingly advocated as a more specific marker of splanchnic perfusion than PiCO2alone. We examined the stability of the PiCO2- PaCO2gradient compared with raw PiCO2measurements during induced systemic hypo- and hypercapnia.Design:A prospective animal study.Settings:A university research laboratory.Subjects:Twenty anesthetized, paralyzed, and mechanically ventilated mongrel dogs.Interventions:After a baseline period during which PaCO2was maintained near 40 torr, the animals were divided into four groups. Minute ventilation was then altered by adjusting tidal volume, frequency, or both to achieve group PaCO2values of 15, 20, 60, and 80 torr for groups 1 through 4, respectively. Portal blood flow was monitored and maintained near baseline levels by infusion of intravenous fluids. Intestinal PiCO2was measured continuously by using capnometric recirculating gas tonometry.Measurements and Main Results:Mean (± SE) aggregate baseline PiCO2- PaCO2was 16.9 ± 3.3 torr. After 60 mins of hypoventilation, PiCO2- PaCO2decreased to 14.2 ± 1.1 and to 13.7 ± 2.7 torr in groups 3 and 4, respectively (p= NS, compared with baseline for both). On the other hand, after 60 mins of hyperventilation, PiCO2- PaCO2increased to 37.9 ± 3.6 and 28.0 ± 6.3 torr in groups 1 and 2, respectively (p< .0001, compared with baseline for both).Conclusions:In this model of maintained portal blood flow, PiCO2- PaCO2remained essentially stable after hypoventilation but increased significantly after inducing hyperventilation. Our findings warrant cautious interpretation of PiCO2- PaCO2as an indicator of splanchnic perfusion during systemic hypocapnia.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:To investigate the role of the vasodilator systems heme oxygenase-1/heat shock protein 32 (HO-1/HSP32) and nitric oxide synthase-II (NOS-II), generating carbon monoxide and nitric oxide respectively, as modulators of liver injury in an experimental model of reversible hemorrhagic shock.Design:Prospective controlled laboratory study.Setting:University research laboratory.Subjects:Male Sprague-Dawley rats weighing 250-350 g.Interventions:Animals were anesthetized and assigned to a hemorrhagic shock (mean arterial pressure, 35-40 mmHg for 60 mins) or a sham protocol. On the basis of the time course of gene expression, HO-1/HSP32 or NOS-II was blocked 5 hrs after onset of resuscitation. To assess the role of the antioxidative properties of the heme oxygenase (HO) pathway in additional experiments, Trolox, a potent antioxidant, was administered at the time of blockade of HO. Liver injury was assessed morphometrically and by plasma α-glutathione-S-transferase (α-GST) release 11 hours after onset of resuscitation.Measurements and Main Results:Hemorrhage and resuscitation increased HO-1/HSP32 messenger RNA and protein primarily in parenchymal cells, and a faint induction of NOS-II, restricted to nonparenchymal cells, was observed. Inhibition of the HO pathway with tin protoporphyrin-IX (SnPP-IX) increased the incidence of pericentral necrosis (intact acini: shock/vehicle 68.8%; shock/SnPP-IX 42.6%) and α-GST levels (sham 94 ± 24 μg/L; shock/vehicle 377 ± 139 μg/L; shock/SnPP-IX 1708 ± 833 μg/L), whereas blockade of NOS-II with S-methylisothiourea did not affect liver injury. Coadministration of Trolox failed to attenuate the aggravation of necrosis associated with blockade of HO, whereas α-GST levels were reduced (intact acini: shock/vehicle/Trolox 82.1%, shock/SnPP-IX/Trolox 42.7%; α-GST: shock/vehicle/Trolox 202 ± 55 μg/L; shock/SnPP-IX/Trolox 236 ± 61 μg/L).Conclusions:These data suggest that HO-1/HSP32, but not the alternative cyclic guanosine monophosphate-generating enzyme NOS-II, is induced after hemorrhage and resuscitation and protects against hepatocellular injury. Both metabolites generated by the heme oxygenase pathway, e.g., carbon monoxide (a vasodilator) and biliverdin (an antioxidant) seem to contribute to the salutary effects of induction of HO-1/HSP32.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:In patients with severe head injuries, brain damage occurs not only from the primary trauma but also secondarily from a reduction in cerebral oxygenation as a result of brain swelling, ischemia, and elevated intracranial pressure (ICP). However, routine interventions designed to maintain oxygenation, such as endotracheal suctioning (ETS), also may negatively affect the cerebrovascular status by increasing the ICP. The purpose of this study was to determine whether ETS influences cerebral oxygenation in patients with traumatic brain injury.Design:Descriptive, prospective, with repeated assessments within each patient.Setting:Ten-bed trauma intensive care unit in a university Level I trauma center.Subjects:Nineteen patients who were 16 yrs or older, had acute head injury, a Glasgow Coma Scale score ≤8, external ventricular drain and arterial pressure devices in place, and were intubated and mechanically ventilated.Interventions:ETS protocol consisting of administration of four ventilator-delivered breaths at 135% of the patients' actual tidal volume, 100% FIO2, before and after suctioning with a standardized catheter at a 16-L flow rate.Measurements and Main Results:This study examined cerebrovascular responses as measured by the traditional measures of ICP and cerebral perfusion pressure, as well as middle cerebral artery velocity and jugular venous oxygen tension that occurred during ETS in head-injured adults. The results of this study show that both ICP and cerebral perfusion pressure are increased during ETS. In the majority of patients (84%), the ICP returned to baseline values within 2 mins.Conclusions:The increase in jugular venous oxygen tension associated with increases in middle cerebral artery velocity and mean arterial pressure suggests that cerebral oxygen delivery was maintained during ETS. Cerebral changes associated with ETS using the described protocol are consistent with the preservation of cerebral oxygenation.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective:Aminophylline has not been studied as an adjunct diuretic in critically ill children. Our purpose was to evaluate its use in the treatment of fluid overload in these patients.Design:Open, controlled clinical trial.Setting:Pediatric intensive care unit.Patients:Study subjects ranged from 2-46 months of age, were fluid overloaded, and were receiving a continuous infusion of furosemide (≥6 mg/kg/day). Patients with hemodynamic instability or liver dysfunction were excluded.Interventions:A single dose of aminophylline (6 mg/kg) was given after establishing baseline values. There were no additional diuretics or changes in vasoactive agents during the study.Measurements and Main Results:Urine output, creatinine clearance, and sodium and potassium excretion were measured before and after administration of the aminophylline bolus. Heart rate and mean arterial pressure (mm Hg) were recorded hourly. Urine output increased by >80% (p< .01) during the first 2 hrs after administration of the aminophylline bolus and then returned to baseline by 4 to 6 hrs. The change in urine output is consistent with the pharmacokinetics of aminophylline. Heart rate and mean arterial pressure exhibited a change of <10% from baseline.Conclusions:These results suggest that aminophylline is an effective adjunct to furosemide in increasing diuresis in critically ill children with fluid overload. The increased diuresis can be accomplished without increased risk if drug levels are adequately monitored.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objectives:To evaluate the efficacy of a single dose of ketorolac compared with morphine for the relief of pain in children, and to determine the safety of ketorolac.Setting:Tertiary pediatric intensive care unit in a university-affiliated hospital.Design:Prospective, randomized, double-blind, parallel, single-dose, positive control study.Patients:Children admitted to the intensive care unit with postoperative pain.Interventions:Patients received a single dose of either morphine or ketorolac as the first postoperative analgesic when the pain score indicated significant pain. Blood pressure, heart rate, and urine output were recorded, as well as blood urea nitrogen, creatinine, bleeding time, hematuria or proteinuria, and aspartate aminotransferase. Side effects such as nausea and vomiting were noted. Morphine was used for rescue treatment if the patient continued to have significant pain ≥30 mins after study drug administration.Measurements and Main Results:Of the 102 children studied, 48 received morphine and 54 received ketorolac. The percentage of patients reporting pain relief in the first and second hours after drug administration was not different between groups. Likewise, the proportion of patients who met the criteria for pain relief during the entire evaluation period was not different between groups. There was a trend toward fewer patients who received ketorolac requiring remedication in the first 4 hrs compared with those who received morphine, but this trend did not reach statistical significance. More patients in the morphine group failed to achieve pain relief at any time after the dose compared with those who received ketorolac. There were no differences between the two groups in physiologic or laboratory variables. Vomiting was more common in patients who received ketorolac.Conclusion:Ketorolac is comparable to morphine in relief of postoperative pain in children. A single dose of ketorolac does not result in abnormal postoperative bleeding or alter renal function. However, ketorolac may cause nausea and vomiting in some patients.

ISSN:0090-3493    

出版商:OVID    

年代:1999

数据来源: OVID