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Cerebral perfusion during cardiopulmonary bypass with special reference to blood flow
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiopulmonary bypass (CPB) is an important method that enables open heart surgery. There is a risk of neurological complications, and efforts to minimize those include optimization of the cerebral perfusion during CPB. This thesis focuses on such optimization of flow conditions in case of obstructed venous drainage, carotid stenosis and during selective antegrade cerebral perfusion (SACP).

In a pig model of impaired venous drainage from the superior vena cava (SVC), stepwise obstruction increased the central venous pressure (CVP) and caused impaired oxygenation. Cerebral micro-dialysis revealed ischemic responses in some but not all of the pigs.

Further experiments, using the same model, aimed to restore cerebral perfusion pressure (CPP) reduced by 75% superior venous obstruction. Both vasopressor treatment and increased venous drainage were effective in normalizing the CPP and improving the cerebral oxygenation. The intracranial pressure was elevated in the vasopressor group, but no signs of brain damage were observed.

The arterial flow during CPB can be altered between pulsatile and non-pulsatile profiles. Switching between these modes was performed during CPB in 20 patients with or without carotid stenosis. The effects on cerebral oxygenation and mean arterial pressure (MAP) were examined. The MAP was significantly lowered by pulsatile flow, but the flow profile did not affect the cerebral oxygenation. No differences were seen between patients with or without carotid stenosis.

SACP is used to ensure the cerebral perfusion during deep hypothermic circulatory arrest (HCA). The cerebral blood flow (CBF) was examined using positron-emission tomography (PET) technique in 8 pigs divided into HCA and HCA+SACP groups. The CBF was downregulated by 70% to 0.10 ml/cm3/min by 20°C hypothermia. A pump flow of 6 ml/kg/min preserved the CBF level without signs of cerebral desaturation. The fluorodeoxyglucose (FDG) uptake after re-warming to 37°C was similar after SACP compared with HCA alone.

In conclusion, experimental SVC obstruction may impair the cerebral perfusion. Vasopressors can restore the CPP during SVC obstruction and improve cerebral oxygenation. In patients, pulsatile flow can lower the MAP in absence of effects on the cerebral oxygenation. During experimental HCA, SACP at 6 ml/kg/min can preserve the CBF at 0.10 ml/cm3/min.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1108
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:uu:diva-248686ISBN: 978-91-554-9257-1 (print)OAI: oai:DiVA.org:uu-248686DiVA: diva2:806653
Public defence
2015-06-11, Robergsalen, Ingång 40, 4 tr, Akademiska sjukhuset, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2015-05-21 Created: 2015-04-07 Last updated: 2015-07-07Bibliographically approved
List of papers
1. Venous obstruction and cerebral perfusion during experimental cardiopulmonary bypass
Open this publication in new window or tab >>Venous obstruction and cerebral perfusion during experimental cardiopulmonary bypass
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2010 (English)In: Interactive Cardiovascular and Thoracic Surgery, ISSN 1569-9293, E-ISSN 1569-9285, Vol. 11, no 5, 561-566 p.Article in journal (Refereed) Published
Abstract [en]

To investigate the effects on cerebral perfusion by experimental venous congestion of the superior vena cava (SVC) during bicaval cardiopulmonary bypass (CPB) at 34 °C, pigs were subjected to SVC obstruction at levels of 75%, 50%, 25% and 0% of baseline SVC flow at two arterial flow levels (low, LQ, high, HQ). The cerebral perfusion was examined with near-infrared spectroscopy (NIRS), cerebral microdialysis and blood gas analysis. SVC obstruction caused significant decreases in the NIRS tissue oxygenation index (TOI) and in SVC oxygen saturations (P<0.05, both groups), while the mixed venous saturation was decreased only in the LQ group. Sagittal sinus venous saturations were measured in the HQ group and found significantly reduced in response to venous congestion (P<0.05). No microdialysis changes were seen at the group level, however, individual ischemic patterns in terms of concomitant venous desaturation, decreased TOI and increased lactate/pyruvate occurred in both groups. The total venous drainage remained stabile throughout the experiment, indicating increased flow in the inferior vena cava cannula. The results indicate that SVC congestion may impair cerebral perfusion especially in the case of compromised arterial flow during CPB. Reduced SVC cannula flow may pass undetected during bicaval CPB, if SVC flow is not specifically monitored.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-140803 (URN)10.1510/icvts.2010.238535 (DOI)000208483300014 ()20696750 (PubMedID)
Available from: 2011-01-10 Created: 2011-01-10 Last updated: 2017-12-11Bibliographically approved
2. Experimental treatment of superior venous congestion during cardiopulmonary bypass
Open this publication in new window or tab >>Experimental treatment of superior venous congestion during cardiopulmonary bypass
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2013 (English)In: European Journal of Cardio-Thoracic Surgery, ISSN 1010-7940, E-ISSN 1873-734X, Vol. 44, no 3, E239-E244 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES:

Superior venous outflow obstruction affects cerebral perfusion negatively by reducing cerebral perfusion pressure (CPP). We present a randomized study designed to compare two alternative strategies to preserve the CPP during superior vena cava (SVC) congestion and cardiopulmonary bypass (CPB).

METHODS:

Fourteen pigs on bi-caval CPB were subjected to 75% occlusion of the SVC flow. CPP was restored either by vasopressor treatment (VP, n = 7) or by partial relief (PR) of the congestion (n = 7). The cerebral effects of the interventions were studied for 60 min with intracranial pressure (ICP) monitoring, cerebral blood flow measurement, the near-infrared light spectroscopy tissue oxygen saturation index (StO2), arterial and venous blood gas analyses and serial measurements of the glial cell damage marker protein S100β.

RESULTS:

Both strategies restored the CPP to baseline levels and no signs of severe ischaemia were observed. In the PR group, the venous and ICPs were normalized in response to the intervention, while in the VP group those parameters remained elevated throughout the experiment. The haemoglobin oxygen saturation in the sagittal sinus (SsagO2) was increased by both VP and PR, while significant improvement in the StO2 was observed only in the PR group. The S100β concentrations were similar in the two groups.

CONCLUSIONS:

Experimental SVC obstruction during CPB may reduce the CPP, resulting in impaired cerebral perfusion. Both vasopressor treatment and improved venous drainage can, in the short term, individually restore the CPP during these circumstances.

Keyword
cerebral protection, cardiopulmonary bypass, venous obstruction
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-199823 (URN)10.1093/ejcts/ezt311 (DOI)000323350400018 ()23766424 (PubMedID)
Available from: 2013-05-15 Created: 2013-05-15 Last updated: 2017-12-06Bibliographically approved
3. Cerebral oxygen saturation during pulsatile and non-pulsatile cardiopulmonary bypass in patients with carotid stenosis
Open this publication in new window or tab >>Cerebral oxygen saturation during pulsatile and non-pulsatile cardiopulmonary bypass in patients with carotid stenosis
2015 (English)In: Perfusion, ISSN 0267-6591, E-ISSN 1477-111XArticle in journal (Refereed) Published
Keyword
Cardiopulmonary bypass, carotid stenosis, pulsatile CPB flow, NIRS
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-248678 (URN)
Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2017-12-04
4. Blood flow and metabolism during selective cerebral perfusion - a PET study
Open this publication in new window or tab >>Blood flow and metabolism during selective cerebral perfusion - a PET study
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(English)Manuscript (preprint) (Other academic)
Keyword
Selective antegrade cerebral perfusion, Cardiopulmonary bypass, Cerebral autoregulation, PET
National Category
Anesthesiology and Intensive Care Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-248682 (URN)
Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2015-09-24

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