Effects of acute hemorrhage on intrapulmonary shunt in a pig model of acute respiratory distress-like syndrome.
BACKGROUND
In acute respiratory distress syndrome (ARDS), gas exchange and respiratory system mechanics (compliance) are severely impaired. Besides ventilatory parameters, the degree of respiratory abnormality can be influenced by the circulatory state. This study investigated the influence of acute hypovolemia on the respiratory system.


METHODS
We performed a secondary analysis of a previous study including 8 pigs with ARDS-like syndrome induced by lung lavage and surfactant depletion method (ARDS group) and 10 mechanically ventilated pigs with no intervention (CTRL group). Animals of both groups were subjected to hemorrhage and retransfusion successively. We reanalyzed the effect of acute blood volume variations on intrapulmonary shunt (shunt), arterial oxygenation (PaO2:FiO2), global oxygen delivery (DO2) and respiratory system compliance (Crs).


RESULTS
In the ARDS group, after hemorrhage, shunt decreased (-28 +/- 3.5 % (p < 0.001)), respiratory system compliance (Crs) increased (+5.1 +/- 1.0 ml/cm H2O (p < 0.001)) moreover, there was a concurrent increase in PaO2:FiO2 (+113 +/- 19.1 mmHg; p < 0.001) but this did not prevent a reduction in DO2 (-317 +/- 49.8 ml/min; p < 0.001). Following retransfusion, shunt and Crs return towards pre-hemorrhage values. Similar changes, but of smaller magnitude were observed in the CTRL group, except that no significant changes in oxygenation occurred.


CONCLUSIONS
The present analysis suggests that an acute decrease in blood volume results in a decrease in shunt with a parallel improvement in arterial oxygenation and an increase in Crs during ARDS-like syndrome. Our results strengthen the importance to integrate the circulatory condition in the analysis of the state of the respiratory system. However, the translation of this physiological model in a clinical perspective is not straightforward because our model of acute and severe hemorrhage is not strictly equivalent to a progressive hypovolemia, as could be obtained in ICU by diuretic. Furthermore, the present model does not consider the impact of blood loss induced decrease of DO2 on other vital organs function.


BACKGROUND
'Not applicable'.
Intensive Care Unit, University Hospitals of Geneva, Geneva, Switzerland.|University of Geneva, University Medical Center, Geneva, Switzerland.
Nils
N
Siegenthaler
Intensive Care Unit, University Hospitals of Geneva, Geneva, Switzerland.|University of Geneva, University Medical Center, Geneva, Switzerland.
Raphael
R
Giraud
Division of Clinical Epidemiology (Biostatistics), University Hospitals of Geneva, Geneva, Switzerland.
Delphine S
DS
Courvoisier
Department of Physiology and Pharmacology, Division of Anaesthesiology and Intensive Care, Karolinska Institute, Stockholm, Sweden.
Claes U
CU
Wiklund
Intensive Care Unit, University Hospitals of Geneva, Geneva, Switzerland. karim.bendjelid@hcuge.ch.|University of Geneva, University Medical Center, Geneva, Switzerland. karim.bendjelid@hcuge.ch.|Geneva Hemodynamic Research Group, Geneva, Switzerland. karim.bendjelid@hcuge.ch.|Department of Anesthesiology, Pharmacology and Intensive Care, Service of Adult Intensive Care, Geneva University Hospital, Rue Gabrielle-Perret-Gentil 4, 1205, Genève, Switzerland. karim.bendjelid@hcuge.ch.
Karim
K
Bendjelid
D000818:Animals; D001784:Blood Gas Analysis; D004195:Disease Models, Animal; D006470:Hemorrhage / Q000150:complications* / Q000503:physiopathology; D020896:Hypovolemia / Q000150:complications* / Q000503:physiopathology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine
Admission; Lung compliance; Transpulmonary blood flow