The effects of cardiopulmonary bypass and deep hypothermic circulatory arrest on blood viscoelasticity and cerebral blood flow in a neonatal piglet model

Perfusion ◽  
2000 ◽  
Vol 15 (2) ◽  
pp. 121-128 ◽  
Author(s):  
Akif Ündar ◽  
William K Vaughn ◽  
John H Calhoon
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Regional Cerebral Blood Flow ◽  
Circulatory Arrest ◽  
Deep Hypothermic Circulatory Arrest ◽  
Hypothermic Circulatory Arrest ◽  
Regional Cerebral Blood ◽  
Neonatal Piglet ◽  
Arterial Blood

The purpose of this study is to determine the effects of cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) on the viscoelasticity (viscosity and elasticity) of blood and global and regional cerebral blood flow (CBF) in a neonatal piglet model. After initiation of CPB, all animals ( n = 3) were subjected to core cooling for 20 min to reduce the piglets’ nasopharyngeal temperatures to 18°C. This was followed by 60 min of DHCA, then 45 min of rewarming. During cooling and rewarming, the alpha-stat technique was used. Arterial blood samples were taken for viscoelasticity measurements and differently labeled microspheres were injected at pre-CPB, pre- and post-DHCA, 30 and 60 min after CPB for global and regional cerebral blood flow calculations. Viscosity and elasticity were measured at 2 Hz, 22°C and at a strain of 0.2, 1, and 5 using a Vilastic-3 Viscoelasticity Analyzer. Elasticity of blood at a strain = 1 decreased to 32%, 83%, 57%, and 61% ( p = 0.01, ANOVA) while the viscosity diminished 8.4%, 38%, 22%, 26% compared to the baseline values ( p = 0.01, ANOVA) at pre-DHCA, post-DHCA, 30 and 60 min after CPB, respectively. The viscoelasticity of blood at a strain of 0.2 and 5 also had similar statistically significant drops ( p < 0.05). Global and regional cerebral blood flow were also decreased 30%, 66%, 64% and 63% at the same experimental stages ( p < 0.05, ANOVA). CPB procedure with 60 min of DHCA significantly alters the blood viscoelasticity, global and regional cerebral blood flow. These large changes in viscoelasticity may have a significant impact on organ blood flow, particularly in the brain.

Global and regional cerebral blood flow in neonatal piglets undergoing pulsatile cardiopulmonary bypass with continuous perfusion at 25°C and circulatory arrest at 18°C

Perfusion ◽  
2001 ◽  
Vol 16 (6) ◽  
pp. 503-510 ◽  
Author(s):  
Akif Ündar ◽  
Takafumi Masai ◽  
Shuang-Qiang Yang ◽  
Harald C Eichstaedt ◽  
Mary Claire McGarry ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Regional Cerebral Blood Flow ◽  
Negative Impact ◽  
Circulatory Arrest ◽  
Deep Hypothermic Circulatory Arrest ◽  
Regional Cerebral Blood ◽  
Neonatal Piglets ◽  
The Right

To investigate the influence of hypothermic cardiopulmonary bypass (HCPB) at 25°C and circulatory arrest at 18°C on the global and regional cerebral blood flow (CBF) during pulsatile perfusion, we performed the following studies in a neonatal piglet model. Using a pediatric physiologic pulsatile pump, we subjected six piglets to deep hypothermic circulatory arrest (DHCA) and six other piglets to HCPB. The DHCA group underwent hypothermia for 25 min, DHCA for 60min, cold reperfusion for 10 min, and rewarming for 40 min. The HCPB group underwent 15 min of cooling, followed by 60 min of HCPB, 10min of cold reperfusion, and 30 min of rewarming. The following variables remained constant in both groups: pump flow (150 ml/kg/min), pump rate (150 bpm), and stroke volume (1 ml/kg). During the 60-min aortic crossclamp period, the temperature was kept at 18°C for DHCA and at 25°C for HCPB. The global and regional CBF (ml/100g/min) was assessed with radiolabeled microspheres. The CBF was 48% lower during deep hypothermia at 18°C (before DHCA) than during hypothermia at 25°C (55.2± 14.3 ml/100 g/min vs 106.4±19.7 ml/100 g/min; p < 0.05). After rewarming, the global CBF was 45% lower in the DHCA group than in the HCPB group 48.3±18.1 ml/100 g/min vs (87±35.9 ml/100 g/min; p<0.05). Fifteen minutes after the termination of CPB, the global CBF was only 25% lower in the DHCA group than in the HCPB group (42.2±20.7 ml/100 g/min vs 56.4±25.8 ml/100 g/min; p=NS). In the right and left hemispheres, cerebellum, basal ganglia, and brain stem, blood flow resembled the global CBF. In conclusion, both HCPB and DHCA significantly decrease the regional and global CBF during CPB. Unlike HCPB, DHCA has a continued negative impact on the CBF after rewarming. However, 15 min after the end of CPB, there are no significant intergroup differences in the CBF.

Continuous monitoring of regional cerebral blood flow: experimental and clinical validation of a novel thermal diffusion microprobe

2000 ◽  
Vol 93 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Peter Vajkoczy ◽  
Harry Roth ◽  
Peter Horn ◽  
Thomas Lucke ◽  
Claudius Thomé ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Thermal Diffusion ◽  
Regional Cerebral Blood Flow ◽  
Linear Regression Analysis ◽  
Secondary Brain Injury ◽  
Regional Cerebral Blood ◽  
Content Type ◽  
Arterial Blood ◽  
Fine Print

Object. Current clinical neuromonitoring techniques lack adequate surveillance of cerebral perfusion. In this article, a novel thermal diffusion (TD) microprobe is evaluated for the continuous and quantitative assessment of intraparenchymal regional cerebral blood flow (rCBF).Methods. To characterize the temporal resolution of this new technique, rCBF measured using the TD microprobe (TD-rCBF) was compared with rCBF levels measured by laser Doppler (LD) flowmetry during standardized variations of CBF in a sheep model. For validation of absolute values, the microprobe was implanted subcortically (20 mm below the level of dura) into 16 brain-injured patients, and TD-rCBF was compared with simultaneous rCBF measurements obtained using stable xenon-enhanced computerized tomography scanning (sXe-rCBF). The two techniques were compared using linear regression analysis as well as the Bland and Altman method.Stable TD-rCBF measurements could be obtained throughout all 3- to 5-hour sheep experiments. During hypercapnia, TD-rCBF increased from 49.3 ± 15.8 ml/100 g/min (mean ± standard deviation) to 119.6 ± 47.3 ml/100 g/min, whereas hypocapnia produced a decline in TD-rCBF from 51.2 ± 12.8 ml/100 g/min to 39.3 ± 5.6 ml/100 g/min. Variations in mean arterial blood pressure revealed an intact autoregulation with pressure limits of approximately 65 mm Hg and approximately 170 mm Hg. After cardiac arrest TD-rCBF declined rapidly to 0 ml/100 g/min. The dynamics of changes in TD-rCBF corresponded well to the dynamics of the LD readings. A comparison of TD-rCBF and sXe-rCBF revealed a good correlation (r = 0.89; p <0.0001) and a mean difference of 1.1 ± 5.2 ml/100 g/min between the two techniques.Conclusions. The novel TD microprobe provides a sensitive, continuous, and real-time assessment of intraparenchymal rCBF in absolute flow values that are in good agreement with sXe-rCBF measurements. This study provides the basis for the integration of TD-rCBF into multimodal monitoring of patients who are at risk for secondary brain injury.

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