Resuscitation
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Comparative Study
Effects of arterial and venous volume infusion on coronary perfusion pressures during canine CPR.
Intraarterial (IA) volume infusion has been reported to be more effective than intravenous (IV) infusion in treating cardiac arrest due to exsanguination. A rapid IA infusion was felt to raise intraaortic pressure and improve coronary perfusion pressure (CPP). The purpose of this study was to determine if IA or IV volume infusion could augment the effect of epinephrine on CPP during CPR in the canine model. ⋯ The changes in CPP from baseline induced by EPI, EPI/IV and EPI/IA were 20.6 +/- 3.7, 22.8 +/- 4.2 and 22.2 +/- 2.4 mmHg, respectively. Volume loading did not augment the effect of therapeutic EPI dosing. By increasing both preload and afterload, volume administration may in fact be detrimental during CPR.
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Seventeen cynomolgus monkeys under N2O analgesia and sedation were subjected to severe volume-controlled hemorrhagic shock (shed blood volume of 21 or 27 ml/kg). In 12 monkeys, resuscitation was started after increasing periods of hemorrhagic shock from 30 min to 5 h. In five additional monkeys, volume-controlled hemorrhage was modified at hemorrhagic shock 30 min to control MAP at 30 mmHg: resuscitation was started at hemorrhagic shock of 2 h. ⋯ None of the monkeys developed pulmonary dysfunction or functional or morphologic evidence of cerebral damage. This study establishes a new hemorrhagic shock-resuscitation model simulating field-to-hospital life support. Severe hemorrhagic shock with MAP 30-40 mmHg for 90-120 min (without trauma or sepsis) can lead to complete functional recovery after transient malfunction of liver and kidneys.
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We investigated the effects of inversed ratio ventilation by altering the inspiratory:expiratory (I:E) ratio and assessing the time course changes in the intrapulmonary shunting (Qs/Qt) in 14 patients with acute respiratory failure. Stepwise prolongation of the I:E ratio from 1:1.9 to 2:1 and then to 2.6 or 4:1 was applied when PEEP failed to raise the PaO2 above 80 mmHg while breathing oxygen. ⋯ There were no significant changes in hemodynamics, PaCO2, or peak inspiratory pressure during IRV. This ventilatory pattern may be indicated when PEEP fails to improve PaO2, but prolongation of the inspiratory time above an I:E ratio of 2:1 did not produce a greater improvement in Qs/Qt and further increases in PaO2 did not occur after more than 10 h of IRV in our 14 patients.
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Recent studies in swine have suggested that estimating the duration of ventricular fibrillation (VF) could have important implications regarding the selection of the best therapeutic intervention during cardiopulmonary resuscitation (CPR). Successful defibrillation resulting in a pulsatile rhythm is more likely with VF of short duration, whereas VF of longer duration may require interventions designed to augment myocardial blood flow prior to defibrillation. Duration of VF has been estimated in a swine model by modelling the median frequency (FM) of the VF ECG signal. ⋯ The human data revealed an FM which had two peaks with subsequent gradual decline. The data in swine revealed an FM during VF which decreased initially then increased to a peak followed by a gradual decline. Our preliminary results demonstrate that a characteristic median frequency exists in humans which could be used to estimate the duration of VF.