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Microdialysis and tissue oxygenation predicts safe arterial blood flow during cerebral perfusion
Institutionen för kirurgiska vetenskaper.
(English)Article in journal (Refereed) Submitted
Abstract [en]

Background

The optimal blood flow level for selective antegrade cerebral perfusion (SACP) has not been established. Based on experimental data, an arterial flow below 6 mL/kg/min may be associated with ischemia at 20 °C. To evaluate this possible ischemic threshold, cerebral metabolism was evaluated using microdialysis from the cerebral parenchyma and sagittal sinus at SACP levels of 4 and 6 mL/kg/min.

Methods

Pigs on 20 °C cardiopulmonary bypass (CPB) were assigned to Groups 1-3. In Group 1, SACP was initiated at 4 mL/kg/min and followed by 6 mL/kg/min for 60 + 60 min, respectively. In Group 2, the order was reversed from 6 to 4 mL/kg/min. Group 3 continued on CPB as controls. Cerebral near-infrared spectroscopy was measured continuously while cerebral and sagittal sinus microdialysis samples were analyzed every 30 min.

Results

The tissue oxygenation index was significantly lower in Group 1 compared with Groups 2 and 3 at 90-120 min (p=0.007) and the cerebral lactate/pyruvate ratio was significantly greater at 120 minutes in Group 1 compared to Groups 2 and 3 (p=0.008). Glycerol in the sagittal sinus blood was significantly elevated at 120 min in Groups 1 and 2 compared to the control (p<0.0001). There was no agreement between microdialysis biomarker levels in the brain parenchyma and sagittal sinus blood.

Conclusions

SACP at 6 mL/kg/min preserved metabolism in the present model, whereas at 4 mL/kg/min early signs of disturbed energy metabolism were seen. Microdialysis from the sagittal sinus is feasible but no agreement with parenchymal measurements could be demonstrated.

Keyword [en]
cerebral perfusion
National Category
Physiology
Research subject
Thorax Surgery
Identifiers
URN: urn:nbn:se:uu:diva-147481OAI: oai:DiVA.org:uu-147481DiVA: diva2:400453
Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2011-03-30
In thesis
1. Cerebral Perfusion and Metabolism during Experimental Extracorporeal Circulation
Open this publication in new window or tab >>Cerebral Perfusion and Metabolism during Experimental Extracorporeal Circulation
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Neurologic injuries are major causes of mortality and morbidity after cardiac surgery. This thesis aimed to investigate cerebral metabolism and perfusion abnormalities in pigs during hypothermic circulatory arrest, selective antegrade cerebral perfusion (SACP) and extracorporeal circulation following progressive venous stasis.

Hypothermic circulatory arrest induced a metabolic pattern consistent with overt ischaemia, which was absent following SACP. In contrast, metabolism during SACP was influenced by the perfusate temperature, where a colder perfusate (20 °C) preserved cellular metabolism and membrane integrity better than a warmer perfusate (28 °C).

The minimum SACP flow required to maintain metabolism during hypothermia at 20 °C was investigated with magnetic resonance imaging, protein S100β, near infrared spectroscopy and microdialysis. The findings suggested an ischaemic threshold close to 6 ml/kg/min in the present models. Furthermore, regional differences in perfusion with a hemispheric distribution were apparent at all flow levels and differed from earlier studies where the differences were uniform and followed a neuranatomical pattern.

Venus stasis following superior vena cava congestion produced measurable signs of impaired cerebral perfusion and patterns of cerebral ischaemia were evident in individual animals. As venous pressure increased, the mean arterial pressure stayed more or less unchanged, generating reduced cerebral perfusion pressure and consequently an increased risk of ischaemia, which may impair cerebral perfusion, especially in cases of compromised arterial flow during extracorporeal circulation.

In conclusion, cerebral metabolism and perfusion are influenced by temperature, SACP flow levels and venous congestion. In clinical practice, the regional differences in perfusion during SACP may be of pathogenic importance in focal cerebral ischaemia. Furthermore, the reduced superior vena cava cannula flow may pass undetected during bicaval cardiopulmonary bypass if the superior vena cava flow is not specifically monitored.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 85 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 649
Keyword
cerebral perfusion
National Category
Physiology
Research subject
Thorax Surgery
Identifiers
urn:nbn:se:uu:diva-147486 (URN)978-91-554-8016-5 (ISBN)
Public defence
2011-04-08, Enghovssalen, Hus 50,, Thoraxkliniken, Akademiska Sjukuset, 17185, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2011-03-17 Created: 2011-02-25 Last updated: 2011-05-04Bibliographically approved

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