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Cerebral Perfusion during Cardiopulmonary Bypass
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Impaired superior vena cava (SVC) cannula outflow during cardiopulmonary bypass (CPB) is a frequent issue, often manifested by only marginal changes in routine monitoring parameters. Nevertheless, significant impact on cerebral perfusion may result. When detected, remedial actions involve cannula repositioning, raising the operating table, increasing the mean arterial pressure (MAP) and adding vacuum-assisted venous drainage to the CPB system. Increased venous outflow enables increased arterial flow and thereby also increased MAP and cerebral perfusion pressure (CPP). Although representing a common clinical problem, controlled studies on SVC obstruction are few and the phenomenon has not been satisfactorily characterized. This licentiate thesis is based on two animal studies. The first (I) study describes the effects on cerebral perfusion and oxygen saturation by stepwise SVC cannula obstruction in increments of 25% until fully occluded. The second (II) study describes the effects on CPP and cerebral perfusion of two different strategies for dealing with restricted cerebral venous outflow. In Study I, ten pigs during 34 ºC CPB were examined. The animals were divided into two groups receiving either low CPB blood flow (LQ), or normal CPB blood flow (HQ). Cerebral perfusion and oxygen saturation were monitored by blood gases, near-infrared light spectroscopy (NIRS) of tissue oxygen saturation (TOI), and cerebral micro-dialysis. SVC obstruction caused increased CVP and deteriorated cerebral oxygen saturation parameters, but no metabolic effects were detectable at the group level by the micro-dialysis. However, four of ten animals showed a combined pattern of decreased TOI and SVC oxygen saturation along with increased lactate/pyruvate ratio. The phenomenon appeared in both groups and in connection with both obstruction and release of obstruction, indicating the presence of individual sensitivity to impaired cerebral perfusion. CPB tubing flow measurements revealed that the total venous drainage was preserved even with the SVC completely clamped, indicating that the drainage, but not the CVP elevation, could be fully compensated by the inferior vena cava. In Study II, intracranial pressure monitoring, NIRS, and cerebral laser-Doppler flow measurements were used for surveillance along with blood gases and analysis of the glial cellmarker S100ß in sagittal sinus blood. A SVC obstruction of 75% was applied in order to achieve a distinct CPP reduction in fourteen pigs subjected to 34 ºC CPB. Two randomly assigned strategies for restoration of the CPP were examined; vasopressor treatment (VP)and partial release of obstruction (PR) mimicking a successful repositioning of the SVC cannula. Both strategies successfully restored the CPP to baseline levels, without immediate signs of severe ischemia, although intracranial and central pressures remained elevated in the VP group throughout the experiments. The analysis of S100ß showed no signs of brain damage. In conclusion, SVC congestion may impair cerebral perfusion during CPB. Reduced SVC cannula flow may pass undetected during bi-caval CPB due to a compensatory increase in IVC flow. Experimental SVC obstruction during CPB may reduce the CPP, resulting in impaired cerebral perfusion. Both vasopressor therapy and improved venous drainage can in the short term individually restore the CPP during these circumstances.

Place, publisher, year, edition, pages
Uppsala: Uppsala University, Department of Surgical Sciences , 2013.
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:uu:diva-204734OAI: oai:DiVA.org:uu-204734DiVA: diva2:640414
Presentation
2013-08-27, Klassrummet, Inst f kir vet, Akademiska sjukhuset, ing 70, Uppsala, 14:00 (Swedish)
Supervisors
Available from: 2013-08-14 Created: 2013-08-09 Last updated: 2014-07-24Bibliographically approved
List of papers
1. 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
2. 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

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