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Pulmonary electrical impedance tomography changes in a model of hemorrhagic shock with endotoxemia and resuscitation

Introduction

Electrical impedance tomography (EIT) is a promising bedside device with the potential to assess changes in regional ventilation and lung blood flow [1]. The purpose of our study was to monitor lung images and changes in impedance by EIT in a model of hemorrhagic shock with endotoxemia followed by fluid resuscitation.

Methods

Twelve anesthetized, mechanically ventilated, supine pigs were submitted to hemorrhagic shock (50% blood volume) and endotoxin infusion. Animals were randomly allocated to control (n = 6) or a treatment group with lactated Ringer's (n = 6). The mean arterial pressure (MAP), central venous pressure (CVP), blood gas, extravascular lung water index (EVLWI), intrathoracic blood volume index (ITBVI), lung compliance and pulmonary EIT (Dräger, Germany) were measured before shock (Tbasal), 60 minutes after hemorrhagic shock (Tshock) and hourly in the treatment period (T1, T2 and T3). Statistical analysis was based on one-way ANOVA (P < 0.05).

Results

In Tshock there was a significant decrease in MAP, CVP, SvO2, lung compliance, cardiac index, EVLWI and ITBVI and an increase in lactate (P < 0.05). Fifty percent of control animals died between T2 and T3. In treated animals, at T3 the EVLWI reached values near those of Tbasal whereas ITBVI remained below baseline (P < 0.05) and above Tshock (P < 0.05). There was sensible change in functional EIT images (Figure 1) and significant differences in impedance along time. Significant global impedance change occurred in T2 relative to Tshock (P < 0.05). Most of the EIT changes were attributable to the ventral lobes (local1), which showed significant differences in T2 and T3 relative to Tbasal (P < 0.05) and of T1, T2 and T3 relative to Tshock (P < 0.05).

Figure 1
figure1

Functional EIT images along timepoints.

Conclusion

Pulmonary impedance changes induced by the proposed model of shock and resuscitation were monitored successfully with the EIT device. Changes were suggestive of alterations in regional ventilation and ventilation–perfusion mismatch.

References

  1. 1.

    Putensen C, et al.: Curr Opin Crit Care. 2007, 13: 344-350. 10.1097/MCC.0b013e328136c1e2

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Acknowledgements

Grants from FAPESP 08/50063-0, 08/50062-4 and LIM08/FMUSP.

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Keywords

  • Mean Arterial Pressure
  • Central Venous Pressure
  • Hemorrhagic Shock
  • Electrical Impedance Tomography
  • Lung Compliance