Intensive care medicine
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Intensive care medicine · Jan 1989
Comparative StudyA randomized comparison of total extracorporeal CO2 removal with conventional mechanical ventilation in experimental hyaline membrane disease.
Apnoeic oxygenation (AO) combined with extracorporeal CO2 removal (ECCO2R), using venovenous perfusion across a membrane area of 0.1 m2 has been shown to be feasible in six healthy anaesthetized rabbits. In a further twelve rabbits, ECCO2R has been randomly compared with conventional mechanical ventilation (CMV) following saline lavage to induce respiratory failure. Blood gases were maintained for up to 6 h within the same range (PaO2 = 8-20 kPa, PaCO2 = 4-6 kPa) in two groups of six by varying airway pressures and the oxygen fraction delivered either to the membrane lung (ECCO2R group) or to the ventilator (CMV group). ⋯ CMV subjects deteriorated and had 80% mortality. Hyaline membranes were absent from ECCO2R subjects and present in all CMV subjects. The response to SI suggests that a lung volume recruitment is maintained during AO for up to 1 h but is ineffective during CMV.
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Intensive care medicine · Jan 1989
Comparative StudyTransthoracic electrical bioimpedance versus thermodilution technique for cardiac output measurement during mechanical ventilation.
To study the possible influence of mechanical ventilation on the accuracy of thoracic electrical bioimpedance (TEI) in the measurement of cardiac output, we determined cardiac output concurrently by TEI using Kubicek's equation and by thermodilution in 8 acutely ill patients who were mechanically ventilated (assist/control mode) but who had no underlying respiratory failure. Cardiac outputs were lower with TEI than with thermodilution (3.97 +/- 0.80 vs 4.83 +/- 1.16 l/min p = 0.004) and there was poor correlation between the values (r = 0.41). Although there is a need to develop non-invasive techniques to measure cardiac output, the present study indicates that TEI is not reliable in mechanically ventilated patients.
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Intensive care medicine · Jan 1989
Diazepam does not improve the mechanical performance of rat cardiac papillary muscle exposed to chloroquine in vitro.
Diazepam has been reported to decrease the cardiac toxicity of chloroquine but the precise mechanism involved remains unknown. Left ventricular papillary muscles from adult Wistar rats were exposed to 10(-4) M chloroquine and assigned to three groups: group I (n = 10) exposed to chloroquine alone; group II (n = 8) exposed to chloroquine and 10(-5) M diazepam; group III (n = 8) exposed to chloroquine and 10(-4) M diazepam. The main mechanical parameters measured were: maximum unloaded shortening velocity (Vmax), maximum lengthening velocity (maxVr), active force normalized per cross-sectional area (AF/s), contraction-relaxation coupling under low load (R1), load sensitivity of relaxation (Isot. ⋯ A/Isom. A (113 +/- 9, 108 +/- 3, 109 +/- 7), or Emax (75 +/- 10, 81 +/- 12, 72 +/- 16). Chloroquine was shown to be a negative inotropic agent since it decreased Vmax, AF/s and Emax, but diazepam did not restore the intrinsic mechanical performance of rat cardiac papillary muscle exposed to chloroquine, therefore 1) the protective cardiovascular effects of diazepam in chloroquine poisoning are not related to an improvement in intrinsic cardiac mechanical properties; 2) inotropic agents are therefore necessary in combination with diazepam for the treatment of severe chloroquine poisoning.
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Intensive care medicine · Jan 1989
Reflection of differential pulmonary perfusion in polytrauma patients on differential lung ventilation (DLV). A comparison of two CO2-derived methods.
Seventeen polytrauma patients with asymmetric pulmonary contusion were treated with differential lung ventilation (DLV). The ratios of differential values of end-tidal CO2 concentration (ETCO2) and CO2 excretion ml/min (VCO2) were compared as indirect parameters for differential pulmonary perfusion. Both CO2-derived methods indicated asymmetry after starting DLV suggesting asymmetric pulmonary perfusion as a consequence of contusion. ⋯ In two patients with very severe contusion who underwent bilobectomies a marked difference between the ratios of ETCO2 and VCO2 was observed. It is concluded that differential measurement of CO2-derived variables may be useful in indicating differential perfusion in clinical practice on DLV. In very severe asymmetric contusion ETCO2 ratios may underestimate the differential perfusion ratio.