Acute hemodynamic changes during lung recruitment in lavage and endotoxin-induced ALI

Intensive Care Med (2005) 31:112–120 DOI 10.1007/s00134-004-2496-x Helena Odenstedt Anders
neman Sigurbergur Krason Ola Stenqvist Stefan Lundin Received: 6 June 2003 Accepted: 21 October 2004 Published online: 17 December 2004
Springer-Verlag 2004 H. Odenstedt ()) · A. neman · O. Stenqvist · S. Lundin Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, 41345 Gteborg, Sweden e-mail: Tel.: +46-31-3421000 Fax: +46-31-413862 S. Krason Department of Anaesthesia and Intensive Care, Landspitali University Hospital, Reykjavik, Iceland EXPERIMENTAL Acute hemodynamic changes during lung recruitment in lavage and endotoxin-induced ALI Abstract Objective: To assess acute cardiorespiratory effects of recruitment manoeuvres in experimental acute lung injury. Design: Experimental study in animal models of acute lung injury. Setting: Experimental laboratory at a University Medical Centre. Animals: Ten pigs with bronchoalveolar lavage and eight pigs with endotoxin-induced ALI. Interventions: Two kinds of recruitment manoeuvres during 1 min; a) vital capacity manoeuvres (ViCM) consisting in a sustained inflation at 30 cmH2O and 40 cmH2O; b) manoeuvres obtained during ongoing pressure-controlled ventilation (PCRM) with peak airway pressure 30 cmH2O, positive end-expiratory pressure (PEEP) 15 and peak airway pressure 40, PEEP 20. Recruitment manoeuvres were repeated after volume expansion (dextran 8 ml/kg). Oxygenation, mean arterial, and pulmonary artery pressures, aortic, mesenteric, and renal blood flow were monitored. Measurements and results: Lower pressure recruitment manoeuvres (ViCM30 and PCRM30/ 15) did not significantly improve Introduction Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are accompanied by atelectasis formation, increasing venous admixture, and arterial hypoxemia [1, 2]. Different recruitment manoeuvres (RMs), as proposed by the “open lung concept”, have been used oxygenation. With ViCM and PCRM at peak airway pressure 40 cmH2O, PaO2 increased to similar levels in both lavage and endotoxin groups. Aortic blood flow was reduced from baseline during PCRM40/20 and ViCM40 by 57€3% and 61€6% in the lavage group and by 57€8% and 82€7% (P<0.05 vs PCRM40/20) in endotoxin group. The decrease in blood pressure was less pronounced. Prior volume expansion attenuated circulatory impairment. After cessation of recruitment hemodynamic parameters were restored within 3 min. Conclusion: Effective recruitment resulted in systemic hypotension, pulmonary hypertension, and decrease in aortic blood flow especially in endotoxinemic animals. Circulatory depression may be attenuated using recruitment manoeuvres during ongoing pressure-controlled ventilation and by prior volume expansion. Keywords Acute lung injury · Lung recruitment · Bronchoalveolar lavage · Endotoxin · Hemodynamics · Oxygen delivery to expand lung volume and to improve gas exchange [3]. Application of a vital capacity manoeuvre, where the lungs are inflated to 40 cmH2O during 15 s in healthy anesthetised subjects [4] and for 40 s in ARDS patients [5] has been used. RMs have also been performed in pressure-controlled ventilation using PEEP levels of 15– 25 cmH2O and increasing peak airway pressures (PAP) up 113 to 45–60 cmH2O [6]. The optimal way of performing RMs is, however, still debated. It is known that increased airway pressure and PEEP may have pronounced extrapulmonary effects [7]. The application of PEEP decreases cardiac output by reducing right ventricular preload and by increasing right ventricular afterload [8, 9]. The splanchnic organs are sensitive to the effects of increased PEEP due to decreased cardiac output, increased venous outflow pressure, pooling of blood, and organ compression [8, 10, 11, 12]. PEEP is known to influence renal function [13] by reduced renal blood flow, elevated renal venous pressure [14, 15], and hormonal responses [16, 17, 18]. In this study the acute effects of different RMs on arterial oxygenation, aortic, mesenteric and renal blood flow, and oxygen delivery were assessed in two experimental ALI models. In one group ALI was achieved by repeated bronchoalveolar lavage (BAL) with isotonic saline causing a lung injury with surfactant depletion [19, 20]. In the other group ALI was induced by infusion of endotoxin (ET) [21]. Two RMs were studied; a vital capacity manoeuvre (ViCM) with a sustained inflation and an RM during ongoing pressure-controlled ventilation (PCRM). Effects of RMs were studied in normovolemic animals and repeated after volume expansion. Material and methods The study was approved by the Committee for Ethical Review of Animal Experiments at Gteborg University and performed in accordance with NIH guidelines. Ten pigs (24–26 kg) were included in the BAL group and eight animals (28–33 kg) in the ET group. Anaesthesia Induction was performed using ketamine (Ketalar, Park-Davis, Sweden) 30 mg/kg and azaperon (Stresnil, Janssen-Cilag, Pharma, Austria) 80 mg intramuscularly. Anaesthesia was maintained by infusion of pentobarbitalnatrium (Apoteksbolaget, Sweden) 6 mg·kg·h and fentanyl (Fentanyl Pharmalink, Pharmalink, Sweden) 0.2 mg/h. Muscle relaxation was achieved by a bolus of pancuronium (Pavulon, Organon, Sweden) 0.1 mg/kg, followed by infusion 0.3 mg·kg·h. The pigs were tracheotomised and mechanically ventilated through an 8-mm endotracheal tube using a Servo 300 or 900C ventilator (Siemens-Elema, Sweden), volume-controlled ventilation (VC), tidal volume (TV) 8 ml/kg, respiratory rate (RR) 20/min, positive end-expiratory pressure (PEEP) 5 cmH2O, inspiration-to-expiration ratio (I:E) 1:2 and FiO2 0.5. Normovolemia was maintained by infusion of Ringer’s solution with 2.5% glucose, 10 ml·kg·h, increased to 20 ml·kg·h after laparotomy. Anticoagulation was achieved by 2500 IE heparin (Heparin Leo, Leo Pharma, Sweden) intravenously, repeated after 4 h. pressure (MAP), mean pulmonary artery pressure (MPAP), and mixed venous oxygen saturation (SvO2) were monitored. Oxygen saturation (SpO2) was recorded from the tail of the pig. A femoral artery and vein were cannulated and connected using silicon tubings. An on-line PaO2 monitor (Polytrode pO2 sensor, Polystan, Denmark, response time 20 s) was inserted in the circuit. Descending aortic blood flow (ABF) was determined using a transoesophageal echo-Doppler (Dynemo 3000, Sometec, France) positioned in the oesophagus. Ultrasonic flowmeter probes (Transsonic Systems, N.Y., USA) were placed around the portal vein and a renal artery to monitor mesenteric blood flow (QPV) and renal artery blood flow (QRA). The animals were placed in supine position. Respiratory rate, volumes, and pressures were measured using side stream spirometry. Inspiratory and expiratory fractions of oxygen and carbon dioxide (FiO2, FETO2, FiCO2, FETCO2) were measured with paramagnetic and infrared technology respectively (AS/3, Datex-Ohmeda, Finland). Experimental procedure for B (...truncated)