摘要:

ObjectiveTo evaluate the relationship between the mixed venous (S&OV0456;o2), hepatic, and femoral venous oxygen saturations before and during sympathomimetic drug infusions.DesignCase series.SettingTertiary care center.PatientsTwenty-four ICU patients: postoperative open-heart surgery patients (n = 12), patients with septic shock (n = 8), and patients with acute respiratory failure (n = 4).InterventionsIn postoperative open-heart surgery patients and patients with respiratory failure, cardiac output was increased by at least 25% following therapy with either dobutamine or dopamine. Patients with septic shock were treated with either dopamine or norepinephrine to correct hypotension.Measurements and Main ResultsVasoactive drug infusions increased cardiac index and oxygen delivery by 34% and oxygen consumption by 8%. S&OV0456;o2increased (62.6 ± 6.7% vs. 69.5 ± 6.0%,p< .001). Although cardiac index was the most important determinant of S&OV0456;o2, the correlation between cardiac index and S&OV0456;o2was weak (r2= .32). The hepatic and femoral venous saturations also increased (49.0 ± 12.1% vs. 59.4 ± 9.8%,p< .01, and 51.9 ± 16.6% vs. 63.4 ± 9.8%,p< .001, respectively) in response to vasoactive treatment. The mean gradient between S&OV0456;o2and hepatic venous saturation was 11.9 ± 8.7% and was independent of the clinical condition and baseline S&OV0456;o2. The hepatic venous oxygen saturation increased in parallel with S&OV0456;o2regardless of the initial S&OV0456;o2value.ConclusionsThe individual values of S&OV0456;o2have no predictive value concerning regional oxygen transport. The parallel increase in S&OV0456;o2and hepatic venous oxygen saturation suggests that the vasoactive treatment did not compromise splanchnic oxygenation.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveTo investigate: a) the relationship between humidifier temperature and inspired gas humidity and b) the effect of insulating the inspiratory tube on “rainout” (condensate).DesignObservational study.SettingRegional neonatal unit in a university hospital.PatientsForty-eight infants receiving assisted ventilation, of whom 31 infants were nursed in incubators and 17 under radiant heaters.Measurements and Main ResultsDespite always maintaining humidifier temperature <34.7°C, inspired gas humidity decreased below the American National Standards Institution minimum of 30 mg H2O/L on 35 of 479 occasions. At a humidifier temperature of 36°C, inspired gas humidity varied between 17 and 43 mg H2O/L. In incubators set at a temperature of 34.1 ± 1.3 (SD) °C, inspired gas humidity was linearly related to humidifier temperature, but with wide scatter (p< .001, r2= .28). In cooler incubators set at 32.9 ± 1.8°C, inspired gas humidity varied inversely with humidifier temperature. This variation was attributed to condensate due to inspired gas cooling within the incubator. Insulation of the inspiratory tubing reduced condensate by only 15%.ConclusionsInspired gas humidity cannot be predicted reliably from humidifier temperature. Accurate control will require a new generation of humidifiers that measure inspired gas humidity.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectivesTo assess the prognostic reliability of multimodality-evoked potentials and to evaluate the diagnostic implications and define the limits of these evoked potentials.SettingAn ICU in a university hospital.DesignProspective clinical study.PatientsSeventy-three severely head-injured patients aged 10 to 75 yrs.MethodsSerial recording of brainstem auditory-evoked potentials and somatosensory-evoked potentials between days 1 and 21 after trauma. Comparison between evoked potential findings and prognosis, along with clinical data.ResultsConsidering the single recordings of both brainstem auditory-evoked potentials and somatosensory-evoked potentials, the accuracy of prognostication in predicting a bad outcome was good only for severely abnormal brainstem auditory-evoked potentials. Serial brainstem auditory-evoked potential recordings and simultaneous recordings of brainstem auditory-evoked potentials and somatosensory-evoked potentials proved to be good prognostic indices in predicting a favorable outcome. Brainstem auditory-evoked potentials correlated well with brainstem reflexes and with pupil asymmetries but did not correlate with Glasgow Coma Scale scores.ConclusionsSerial recording and the use of a multimodality approach provided the best prognostic capabilities. The main diagnostic implications were: a) the possibility of detecting brainstem compression by means of brainstem auditory-evoked potentials before the appearance of pupil abnormalities; b) the usefulness of brainstem auditory-evoked potentials in monitoring brainstem function in patients undergoing high-dose barbiturate therapy.The main limitations of evoked potentials were the occurrence of peripheral acoustic damage, the electromagnetic sources of artifacts in the ICU, and the administration of ototoxic drugs.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveThe waveform of the first derivative of thoracic electrical bioimpedance was used to calculate systolic time intervals of the cardiac cycle, preejection period/left ventricular ejection time ratio, and diastolic time intervals, isovolumic relaxation period/filling time ratio.DesignProspective clinical study. Waveforms were examined from 913 normal and abnormal tracings from a thoracic electrical bioimpedance monitor. This monitor was coupled to a two-channel strip-chart recorder that identified preejection period/LV ejection time and isovolumic relaxation period/filling time in 86% of the tracings.SettingTwo university-affiliated hospitals and one community hospital.PatientsWe assessed 100 subjects (ranging in age from 17 to 93 yrs) under various conditions.Measurements and Main ResultsData from 15 normal subjects were used as a reference series to define normative values. Preejection period/left ventricular ejection time ratio was 0.35 ± 0.1 (SD) and was consistent with data from systolic time intervals derived from simultaneous study of the ECG recording, carotid artery tracing, and phonocardiography. The diastolic time ratio (isovolumic relaxation period/filling time) was 0.4 ± 0.2, in agreement with normal values derived by echocardiography and angiography.In a subgroup of 17 critically ill patients, a correlative study of simultaneously measured thoracic electrical bioimpedance, nuclear stethoscope, and radionuclide ventriculography was conducted. Systolic functions were compared by the ejection fraction derived by preejection period/left ventricular ejection time ratio displayed on the thoracic electrical bioimpedance monitor and by the radionuclide technique, and were found to be 57 ± 13.8% and 58 ± 8.6%, respectively (r2= .49; y = 4.06x + 0.94;p< .02; n = 17). Increased diastolic time ratios with normal or near-normal systolic time intervals were documented in nine (53%) of 17 critically ill patients with low systolic index.ConclusionBoth systolic and diastolic time intervals can be investigated noninvasively at the bedside by the thoracic electrical bioimpedance technique to provide a better understanding of left heart function.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveTo document the efficacy of continuous arteriovenous hemofiltration with dialysis following renal failure, without protein restriction, and to explore the magnitude and clinical applications of total daily urea clearance.DesignA noncomparative, descriptive account of a case series. Data were collected prospectively and analyzed retrospectively.SettingA tertiary care facility in a statewide emergency medical services system.PatientsTwenty-eight patients with renal failure were supported by continuous arteriovenous hemofiltration with dialysis in a critical care unit during a 14-month period (21 patients with multitrauma; three patients with soft tissue infections; and four patients with multisystem organ failure who had been transferred from other hospitals). Renal failure was most commonly due to multisystem organ failure or associated with adult respiratory distress syndrome.ResultsContinuous arteriovenous hemofiltration with dialysis days totaled 308 (mean 10.9). All patients received full protein alimentation (mean protein load 131 g/day). The blood urea nitrogen concentration was controlled, generally to 40 to 75 mg/dL (14.3 to 26.7 mmol/L) within 3 to 5 days. Total daily urea clearance ranged from 15 to 21 g/day. Five (18%) of the 28 patients survived.ConclusionContinuous arteriovenous hemofiltration with dialysis appears to be effective for the control of blood urea nitrogen and clearance of urea. This modality also permits full protein alimentation. Total daily urea clearance can be calculated easily and may have important clinical uses and implications.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveTo evaluate the use of the selective α1-adrenergic receptor agonist phenylephrine in the hemodynamic support of patients with septic shock.DesignRetrospective analysis of clinical use of phenylephrine.SettingSurgical ICU in a university hospital.PatientsThirteen patients with septic shock (diagnosed by defined criteria) requiring pharmacologie support for the treatment of hypotension.Interventions and Main ResultsAll patients underwent invasive hemodynamic monitoring followed by volume resuscitation and inotropic support to reverse flow-dependent oxygen consumption and lactic acidosis. Patients with persistent hypotension (mean arterial pressure [MAP] <65 mm Hg) and vasodilation (systemic vascular resistance index [SVRI] <1500 dyne-sec/cm5-m2received phenylephrine at iv infusion rates of 0.5 to 9 μg/kg·min to maintain MAP >70 mm Hg. MAP, SVRI, left ventricular stroke work index, and stroke volume index were significantly (p < .05) increased after phenylephrine administration and at the time of highest oxygen consumption (&OV0312;o2). Cardiac index was unchanged initially but increased at the time of highest &OV0312;o2(p< .05). Pulmonary artery occlusion pressure and heart rate were unchanged. Average baseline &OV0312;o2increased from 145 to 200 mL/min·m2and oxygen delivery (&U1E0A;o2) increased from 447 to 597 mL/min-m2during phenylephrine treatment (p< .05). Blood lactate concentrations decreased and urine output increased significantly (p< .05), while serum creatinine concentrations remained unchanged during phenylephrine therapy.ConclusionsTreatment with phenylephrine was associated with beneficial hemodynamic effects when used to maintain perfusion, while increasing &U1E0A;o2and &OV0312;o2in patients with septic shock.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveTo compare measurement of oxygen consumption (&OV0312;o2) by spirometry and the reversed Fick method.DesignWithin-patient comparison using simultaneous measurements by the two methods, one previously calibrated on a metabolic simulator.PatientsTwenty sets of observations on eight patients (57 to 83 yrs) requiring mechanical ventilation in a critical care unit.InterventionsNone during or immediately before the measurements.Measurements and Main ResultsDuplicate pairs of measurements of &OV0312;o2were made with a previously validated spirometric technique and the reversed Fick method (&OV0422;t[Cao2– C&OV0456;o2]), where &OV0422;t is cardiac output, Cao2is arterial oxygen content, and C&OV0456;o2is mixed venous oxygen content. The coefficient of variation of the difference between duplicate measurements by the former technique was only 2.53% compared with 10.4% for the latter. The mean &OV0312;o2measurement by the spirometric method was 285.7 ± 40.7 (SD) mL/min standard temperature and pressure, dry (STPD) and for the reversed Fick method, the mean &OV0312;o2measurement was 249.3 ± 38.5 mL/min STPD. The mean difference was 36.4 ± 28.5 mL/min STPD (p<.001).ConclusionsThe repeatability of the spirometric method was four times better than the reversed Fick method. The latter gave a significantly lower value that probably, in part, reflects the &OV0312;o2of the lung, which is included in the spirometric method but not in the reversed Fickmeasurement.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Background and MethodsWe determined derived pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance in chronically instrumented sheep with inhalation injury by using analysis of pressure decay curves after pulmonary artery occlusion.ResultsThere was an increase in derived pulmonary capillary pressure and an increase in the lung lymph flow after smoke inhalation. The pulmonary vascular, arterial, and venous resistances increased significantly in the inhalation group. Pulmonary venous resistance increased proportionately more than pulmonary arterial resistance in the inhalation group. The plasma osmotic pressure-derived pulmonary capillary pressure gradient decreased to a greater extent in the inhalation group than in the control group.ConclusionsThe present experiments suggest that the estimates of derived pulmonary capillary pressure can predict filtration pressure better than pulmonary artery occlusion pressure. The derived pulmonary capillary pressure can be measured easily in man with a pulmonary arterial catheter.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

ObjectiveTo determine whether regional hypoperfusion of the interventricular septum occurs during ventilation with positive end-expiratory pressure.DesignAnimal study.AnimalsAnesthetized, closed chest dogs (n = 8).InterventionsInduction of experimental adult respiratory distress syndrome (ARDS) and then ventilation with 10,15, and 20 cm H2O of positive end-expiratory pressure.Measurements and Main ResultsCardiac output and regional interventricular septum blood flow ‘were assessed at control, at induction of experimental ARDS, and at each level of positive end-expiratory pressure. Ventilation with 20 cm H2O of positive end-expiratory pressure decreased cardiac output (-32% vs. control,p<.05), and did not change absolute, but increased relative (to cardiac output) interventricular septum blood flow. During experimental ARDS and ventilation at 20 cm H2O end-expiratory pressure, there was a redistribution of flow toward the right ventricular free wall (+93%,p< .001) and the right ventricular part of the interventricular septum (+68%,p< .01), while flow to the left ventricular interventricular septum and to the left ventricular free wall remained unchanged. Locally hypoperfused interventricular septum areas or findings indicative of interventricular septum ischemia were not observed during positive end-expiratory pressure.ConclusionsThe decrease in cardiac output during positive end-expiratory pressure is not caused by impaired interventricular septum blood supply. The preferential perfusion of the right ventricular interventricular septum indicates increased local right ventricular interventricular septum oxygen-demand and suggests that during positive end-expiratory pressure, this part of the interventricular septum functionally dissociates from the left ventricular interventricular septum and the left ventricular free wall to support the stressed right ventricle.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Background and MethodsAlthough it is useful in certain clinical situations for manual resuscitator units to be used with spontaneously ventilating patients, there are few data regarding their performance in these settings. We measured the percent-delivered oxygen from 13 adult manual resuscitator, units during simulated spontaneous ventilation in the range of respiratory frequency, tidal volume, and oxygen supply in which manual resuscitator units might be used with patients. We also measured the resistive pressure developed during simulated ventilation and at constant inspiratory flow of 50 L/min.ResultsOxygen supply, tidal volume, minute ventilation, and reservoir volume all influenced percent-delivered oxygen, but the most important determinant of percent-delivered oxygen was valve design. Valves incorporating a “disc” element to prevent air entrainment from the expiratory port gave the most efficient oxygen delivery, while “duck-bill” valves did not reliably prevent air entrainment. Only two of the manual resuscitator units tested developed high resistive pressure.ConclusionReliable administration of high percent-delivered oxygen to spontaneously ventilating patients, while retaining the capability to manually ventilate them, is best achieved by a manual resuscitator unit with a valve of low resistance, incorporating a disc to prevent air entrainment. We recommend that manufacturers indicate on the product information sheet the degree (and confidence limits) to which their manual resuscitator unit presents resistance and delivers oxygen to a spontaneously ventilating subject.

ISSN:0090-3493    

出版商:OVID    

年代:1991

数据来源: OVID