Alveolar recruitment strategy improves arterial oxygenation after cardiopulmonary bypass

Abstract

SummaryAtelectasis occurs during general anaesthesia. This is partly responsible for the impairment of gas exchange that occurs peri-operatively. During cardiopulmonary bypass, this atelectasis is exacerbated by the physical collapse of the lungs. As a result, poor arterial oxygenation is often seen postoperatively. We tested the effect of an Ôalveolar recruitment strategyÕ on arterial oxygenation in a prospective randomised study of 78 patients undergoing cardiopulmonary bypass. Patients were divided equally into three groups of 26. Group Ôno PEEPÕ received a standard post bypass manual lung inflation, and no positive end-expiratory pressure was applied until arrival at intensive care unit. Group Ô5 PEEPÕ received a standard post bypass manual inflation, and then 5 cmH 2 O of positive end-expiratory pressure was applied and maintained until extubation on intensive care. The third group, Ôrecruitment groupÕ, received a pressure-controlled stepwise increase in positive end-expiratory pressure up to 15 cmH 2 O and tidal volumes of up to 18 ml.kg )1 until a peak inspiratory pressure of 40 cmH 2 O was reached. This was maintained for 10 cycles; the positive end-expiratory pressure of 5 cmH 2 O was maintained until extubation on intensive care. There was a significantly better oxygenation in the recruitment group at 30 min and 1 h post bypass when compared with the no PEEP and 5 PEEP groups. There was no significant difference in any of the groups beyond 1 h. Application of 5 cmH 2 O positive end-expiratory pressure alone had no significant effect on oxygenation. No complications due to the alveolar recruitment manoeuvre occurred. We conclude that the application of an alveolar recruitment strategy improves arterial oxygenation after cardiopulmonary bypass surgery.

Manobra de recrutamento alveolar na contusão pulmonar: relato de caso e revisão da literatura

“…(22) To monitor the effects of ARM, most authors assessed improvement of arterial oxygenation, a method commonly used in clinical practice, where the PaO 2 values and the ratio PaO 2 /FiO 2 are analyzed. (23,24) PaO 2 values higher than 450 mmHg would indicate a recruited lung. Valente Barbas, in a study evaluated results of the maneuver by summing of PaO 2 and of PaCO 2 , defining the complete recruitment as PaO 2 +PaCO 2 higher than 400mmHg (25) Another method described to assess efficacy of alveolar recruitment is computerized tomography, capable of quantifying the recruited lung tissue.…”

Manobra de recrutamento alveolar na reversão da hipoxemia no pós-operatório imediato em cirurgia cardíaca

“…Esse aumento na oxigenação depois da MRA também sugere um melhor acoplamento entre a ventilação e a perfusão pulmonar. Há alguma controvérsia quanto a maior ou menor efetividade da MRA para corrigir a hipoxemia, quando aplicada de forma isolada ou em conjunto com a PEEP ou a PEEP de maneira isolada em procedimentos cirúrgicos cardíacos e pulmonares 5,11,15,16 . Em investigação pregressa, também em pacientes no pós-operatório de intervenção cirúrgica cardíaca, demonstrou-se que a aplicação progressiva da PEEP até 15 cm de H 2 O foi efetiva em aumentar a oxigenação com mínimos efeitos hemodinâ-micos negativos 5 .…”

“…This increased in oxygenation after ARM also suggests an improvement in the ratio between ventilation and pulmonary perfusion. There are controversies regarding the degree of effectiveness of ARM used by itself, associated with PEEP, or PEEP alone to correct hypoxemia after cardiac and pulmonary surgeries 5,11,15,16 . A prior study, also with patients in the postoperative period of cardiac surgery, demonstrated that the progressive use of PEEP until 15 cmH 2 O increased oxygenation with minimal negative hemodynamic effects 5 .…”

“…Similar results were reported in patients in the postoperative period of cardiac surgery with the use of alveolar recruitment with CPAP with 45 cmH 2 O of airways pressure associated with PEEP of 12 cm H 2 O 11 . Claxton et al 15 studied a similar population and period of follow-up, but with PEEP of 15 cmH 2 O, allowing for a peak inspiratory pressure of 40 cmH 2 O. There was a significant improvement in oxygenation, demonstrated by the Pa 2 O/FIO 2 , in the group undergoing alveolar recruitment, 30 minutes and 1 hour after the maneuvers when compared to the group without PEEP and with PEEP of 5 cmH 2 O. Valta et al 13 and Michalopoulos et al 14 , studying the effects of PEEP on oxygenation after cardiac surgery, demonstrated that values below 10 cmH 2 O are not effective in opening collapsed alveolar units.…”

Recrutamento alveolar em pacientes no pós-operatório imediato de cirurgia cardíaca

“…The hypoxemia conditions in these patients occurs due to intrapulmonary shunt fraction caused by collapsed alveoli [21,22]. According to Neves et al [19], ARM is particularly indicated in clinical situations that can cause alveolar collapse, such as anesthesia, sedation and neuromuscular blockade, as well as to disconnect the patient from the mechanical ventilation.…”