RESUMO
Total oxygen delivery (cardiac output X arterial oxygen content) and oxygen consumption were determined in 22 patients undergoing one-lung ventilation (OLV) during thoracotomy. In 11 patients, anaesthesia was maintained with halothane-oxygen and in another 11 patients with nitrous oxide-oxygen-analgesic combination (FIO2 0.5). During OLV, oxygen delivery was greater in the halothane group and these patients tended to show a decrease in oxygen consumption compared with the patients of the nitrous oxide group. Therefore, as far as total oxygen balance (oxygen delivery/oxygen consumption) during OLV is concerned, halothane-oxygen maintenance provides a greater margin of safety than nitrous oxide-oxygen-analgesic combination. However, in spite of occasional hypoxaemic episodes, none of our patients receiving 50% nitrous oxide in oxygen showed an oxygen delivery coefficient (oxygen delivery/oxygen consumption) significantly smaller than the predicted normal value for an unanaesthetized patient. This finding may explain why this anaesthetic technique has been used without apparent harm during OLV in patients with unimpaired cardiovascular function.
Assuntos
Anestesia/métodos , Halotano , Óxido Nitroso , Oxigênio/administração & dosagem , Respiração Artificial/métodos , Cirurgia Torácica , Brônquios , Débito Cardíaco , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Consumo de OxigênioRESUMO
In an experimental study on dogs, effects of intra-aortic balloon pumping (IABP) on acute myocardial ischaemia without marked cardiac failure were analyzed. With the use of epicardial ST-segment recording IABP was shown to significantly reduce ischaemia when pumping was initiated 10 minutes after left anterior descending coronary artery ligation. Prior to coronary ligation the mean ST-segment height was 6.4 +/- 0.8 mV (mean +/- SE) and 10 minutes after the ligation it was 21.5 +/- 4.6 mV. During pumping ST-segment elevation increased to 6.9 +/- 0.7 mV. A dual-chambered intra-aortic balloon was used, and six dogs were treated with IABP. In the control dog no tendency to spontaneous ST-segment decrease was seen.
Assuntos
Circulação Assistida , Infarto do Miocárdio/prevenção & controle , Choque Cardiogênico/terapia , Doença Aguda , Animais , Pressão Sanguínea , Vasos Coronários/cirurgia , Cães , Frequência Cardíaca , Lactatos/sangue , Miocárdio/metabolismo , Fatores de TempoRESUMO
Previous studies have shown that, in patients undergoing thoracic surgery, a relatively high positive end-expiratory pressure (PEEP of 10 cmH2O = PEEP10) has no beneficial effect on oxygenation during one-lung ventilation (OLV). In the present investigation, cardiorespiratory function was examined in 11 patients intubated endobronchially and undergoing thoracotomy. Comparison was made between two-lung ventilation (TLV) and OLV and between zero end-expiratory pressure and PEEP5 during OLV. Cardiac output was determined to obtain information of the total oxygen delivery (cardiac output times arterial O2 content. The change from TLV to OLV was accompanied by a marked fall in PaO2 and a marked rise in shunt, whereas no significant change was observed in mean cardiac output. Oxygen delivery also remained unchanged due to relatively small decrease in SaO2 (arterial oxygen saturation) and maintenance of cardiac output. The application of PEEP5 during OLV produced no significant changes in these parameters. The findings in individual patients demonstrated the relative importance of cardiac output in determining oxygen delivery during OLV. A significant negative correlation was found between inspiratory airway pressure and cardiac index during OLV.
