Selective brain cooling: role of angularis oculi vein and nasal thermoreception

1997 ◽  
Vol 273 (3) ◽  
pp. R1108-R1116 ◽  
Author(s):  
S. K. Maloney ◽  
G. Mitchell
Keyword(s):  
Blood Flow ◽  
Carotid Artery ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Jugular Veins ◽  
Hypothalamic Temperature ◽  
Blood Flows ◽  
Thermoregulatory Responses

We have measured blood flows in the angularis oculi (AOV), facial, and jugular veins and temperatures in the carotid artery and near the hypothalamus in three lightly anesthetized sheep while body and nasal mucosal (Tnm) temperatures were varied independently. Above a threshold hypothalamic temperature (Thyp) of 39 degrees C both selective brain cooling (SBC) and AOV blood flow increased. For a given Thyp, the increase in AOV flow and SBC was inversely proportional to Tnm: low Tnm resulted in high AOV flow and SBC, whereas increasing Tnm attenuated both AOV flow and SBC. This decrease in AOV flow results in submaximal SBC, which does not concur with the hypothesis that SBC functions to protect a thermally vulnerable brain. The trigger for these changes in AOV blood flow was Tnm. Occlusion of the AOV during SBC showed that AOV flow accounted for over 80% of SBC. We conclude that SBC is not only a mechanism for reducing brain temperature but may also be a means of adjusting Thyp to facilitate the appropriate thermoregulatory responses.

Selective brain cooling increases cortical cerebral blood flow in rats

1993 ◽  
Vol 265 (3) ◽  
pp. H824-H827 ◽  
Author(s):  
J. W. Kuluz ◽  
R. Prado ◽  
J. Chang ◽  
M. D. Ginsberg ◽  
C. L. Schleien ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Rectal Temperature ◽  
High Speed ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Adult Rats ◽  
Doppler Flowmetry ◽  
Cortical Cerebral Blood Flow

To evaluate the effect of selective brain cooling on cortical cerebral blood flow, we reduced brain temperature in nitrous oxide anesthetized adult rats using a high speed fan while keeping rectal temperature at 37-38 degrees C. During selective brain cooling, cortical cerebral blood flow, as measured by laser-Doppler flowmetry, increased to 215 +/- 26% (mean +/- SE) of baseline at a cortical brain temperature of 30.9 +/- 0.5 degrees C and a rectal temperature of 37.5 +/- 0.1 degrees C. During rewarming, as brain temperature increased, cortical cerebral blood flow decreased. The cerebral vasodilatory response to hypothermia may explain its protective effects during and after cerebral ischemia.

Angularis oculi vein blood flow modulates the magnitude but not the control of selective brain cooling in sheep

2011 ◽  
Vol 300 (6) ◽  
pp. R1409-R1417 ◽  
Author(s):  
Andrea Fuller ◽  
Robyn S. Hetem ◽  
Leith C. R. Meyer ◽  
Shane K. Maloney
Keyword(s):  
Water Deprivation ◽  
Brain Temperature ◽  
Heat Exposure ◽  
Venous Drainage ◽  
Threshold Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Before And After

To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep were housed outdoors at 21–22°C and were exposed in a climatic chamber to daytime heat (40°C) and water deprivation for 5 days. In sheep outdoors, SBC was significantly lower after the AOV had been cut, with its 24-h mean reduced from 0.25 to 0.01°C ( t5 = 3.06, P = 0.03). Carotid blood temperature also was lower (by 0.28°C) at all times of day ( t5 = 3.68, P = 0.01), but the pattern of brain temperature was unchanged. The mean threshold temperature for SBC was not different before (38.85 ± 0.28°C) and after (38.85 ± 0.39°C) AOV surgery ( t5 =0.00, P = 1.00), but above the threshold, SBC magnitude was about twofold less after surgery. SBC after AOV surgery also was less during heat exposure and water deprivation. However, SBC increased progressively by the same magnitude (0.4°C) over the period of water deprivation, and return of drinking water led to rapid cessation of SBC in sheep before and after AOV surgery. We conclude that the AOV is not the only conduit for venous drainage contributing to SBC in sheep and that, contrary to widely held opinion, control of SBC does not involve changes in the vasomotor state of the AOV.

scholarly journals Dual role of cerebral blood flow in regional brain temperature control in the healthy newborn infant

2014 ◽  
Vol 37 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sachiko Iwata ◽  
Ilias Tachtsidis ◽  
Sachio Takashima ◽  
Toyojiro Matsuishi ◽  
Nicola J. Robertson ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Newborn Infant ◽  
Temperature Control ◽  
Brain Temperature ◽  
Dual Role ◽  
Healthy Newborn ◽  
Regional Brain

Role of renal medullary adenosine in the control of blood flow and sodium excretion

1999 ◽  
Vol 276 (3) ◽  
pp. R790-R798 ◽  
Author(s):  
Ai-Ping Zou ◽  
Kasem Nithipatikom ◽  
Pin-Lan Li ◽  
Allen W. Cowley
Keyword(s):  
Blood Flow ◽  
Sodium Excretion ◽  
Renal Medulla ◽  
Urine Flow ◽  
Doppler Flowmetry ◽  
Blood Flows ◽  
Medullary Blood Flow ◽  
Adenosine Concentration ◽  
Interstitial Infusion

This study determined the levels of adenosine in the renal medullary interstitium using microdialysis and fluorescence HPLC techniques and examined the role of endogenous adenosine in the control of medullary blood flow and sodium excretion by infusing the specific adenosine receptor antagonists or agonists into the renal medulla of anesthetized Sprague-Dawley rats. Renal cortical and medullary blood flows were measured using laser-Doppler flowmetry. Analysis of microdialyzed samples showed that the adenosine concentration in the renal medullary interstitial dialysate averaged 212 ± 5.2 nM, which was significantly higher than 55.6 ± 5.3 nM in the renal cortex ( n = 9). Renal medullary interstitial infusion of a selective A1antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 300 pmol ⋅ kg−1 ⋅ min−1, n = 8), did not alter renal blood flows, but increased urine flow by 37% and sodium excretion by 42%. In contrast, renal medullary infusion of the selective A2 receptor blocker 3,7-dimethyl-1-propargylxanthine (DMPX; 150 pmol ⋅ kg−1 ⋅ min−1, n = 9) decreased outer medullary blood flow (OMBF) by 28%, inner medullary blood flows (IMBF) by 21%, and sodium excretion by 35%. Renal medullary interstitial infusion of adenosine produced a dose-dependent increase in OMBF, IMBF, urine flow, and sodium excretion at doses from 3 to 300 pmol ⋅ kg−1 ⋅ min−1( n = 7). These effects of adenosine were markedly attenuated by the pretreatment of DMPX, but unaltered by DPCPX. Infusion of a selective A3receptor agonist, N 6-benzyl-5′-( N-ethylcarbonxamido)adenosine (300 pmol ⋅ kg−1 ⋅ min−1, n = 6) into the renal medulla had no effect on medullary blood flows or renal function. Glomerular filtration rate and arterial pressure were not changed by medullary infusion of any drugs. Our results indicate that endogenous medullary adenosine at physiological concentrations serves to dilate medullary vessels via A2 receptors, resulting in a natriuretic response that overrides the tubular A1 receptor-mediated antinatriuretic effects.

scholarly journals Blood Flow Distribution during Heat Stress: Cerebral and Systemic Blood Flow

2013 ◽  
Vol 33 (12) ◽  
pp. 1915-1920 ◽  
Author(s):  
Shigehiko Ogoh ◽  
Kohei Sato ◽  
Kazunobu Okazaki ◽  
Tadayoshi Miyamoto ◽  
Ai Hirasawa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Carotid Artery ◽  
Flow Distribution ◽  
Systemic Circulation ◽  
External Carotid Artery ◽  
Whole Body ◽  
External Carotid ◽  
Blood Flows ◽  
Induced Changes

The purpose of the present study was to assess the effect of heat stress-induced changes in systemic circulation on intra- and extracranial blood flows and its distribution. Twelve healthy subjects with a mean age of 22±2 (s.d.) years dressed in a tube-lined suit and rested in a supine position. Cardiac output (Q), internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) blood flows were measured by ultrasonography before and during whole body heating. Esophageal temperature increased from 37.0±0.2°C to 38.4±0.2°C during whole body heating. Despite an increase in Q (59±31%, P<0.001), ICA and VA decreased to 83±15% ( P=0.001) and 87±8% ( P=0.002), respectively, whereas ECA blood flow gradually increased from 188±72 to 422±189 mL/minute (+135%, P<0.001). These findings indicate that heat stress modified the effect of Q on blood flows at each artery; the increased Q due to heat stress was redistributed to extracranial vascular beds.

Abstract 2044: Selective Head Cooling Initiated during Cpr Induces Post-Resuscitation Carotid Artery Dilation and Increases in Carotid Artery Flow and Cerebral Cortical Microcirculation

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Giuseppe Ristagno ◽  
Jun H Cho ◽  
Tao Yu ◽  
Shijie Sun ◽  
Max H Weil ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Common Carotid Artery ◽  
Brain Temperature ◽  
Capillary Density ◽  
Dark Field ◽  
Sidestream Dark Field ◽  
Blood Flows ◽  
Dark Field Imaging ◽  
Head Cooling ◽  
Artery Flow

Introduction. We have previously reported that selective head cooling initiated during CPR prevented increases in brain temperature and improved neurological outcome. In the present study, we explored the relationship between head cooling during CPR and cerebral blood flows. We hypothesized that head cooling during CPR would yield carotid artery dilation with consequent increases in carotid flows and cerebral cortical microcirculation. Methods. Eight pigs weighing 37 ± 1 kg were intubated and mechanically ventilated. The common carotid artery was isolated and a parietal craniotomy was created. Ventricular fibrillation was electrically induced and untreated for 4 min. Animals were then randomized to head cooling or control. Head cooling was initiated with the aid of the RinoChill device (BeneChill Inc) at the beginning of CPR. CPR was performed for 4 min prior to defibrillation. Common carotid artery diameter and flow were assessed with a Doppler transducer. Cerebral cortical capillary density, representing the number of perfused capillaries, was assessed with Sidestream Dark Field imaging (MicroVisionMedical Inc). Brain temperature was measured with a needle sensor inserted in the cerebral cortex. Results. All the animals were resuscitated. After resuscitation, the brain temperature was significantly decreased in animals subjected to head cooling. Significantly greater carotid artery diameters and flows were observed in animals subjected to selective head cooling compared to the control animals. These increases in carotid blood flows were accompanied by significantly greater numbers of perfused capillaries in the cerebral cortices. No differences in cardiac output were observed between the two groups (Table ). Conclusion. Early selective head cooling induces carotid artery dilation and increases in carotid flows and cerebral cortical microcirculation after resuscitation.

Rectal temperature measurement results in artifactual evidence of selective brain cooling

2001 ◽  
Vol 281 (1) ◽  
pp. R108-R114 ◽  
Author(s):  
Shane K. Maloney ◽  
Andrea Fuller ◽  
Graham Mitchell ◽  
Duncan Mitchell
Keyword(s):  
Rectal Temperature ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Arterial Blood ◽  
The Status ◽  
Conscious Sheep ◽  
Surrogate Measures ◽  
Arterial Blood Temperature

Selective brain cooling (SBC) is defined as a brain temperature cooler than the temperature of arterial blood from the trunk. Surrogate measures of arterial blood temperature have been used in many published studies on SBC. The use of a surrogate for arterial blood temperature has the potential to confound proper identification of SBC. We have measured brain, carotid blood, and rectal temperatures in conscious sheep exposed to 40, 22, and 5°C. Rectal temperature was consistently higher than arterial blood temperature. Brain temperature was consistently cooler than rectal temperature during all exposures. Brain temperature only fell below carotid blood temperature during the final few hours of 40°C exposure and not at all during the 5°C exposure. Consequently, using rectal temperature as a surrogate for arterial blood temperature does not provide a reliable indication of the status of the SBC effector. We also show that rapid suppression of SBC can result if the animals are disturbed.

Segment stroke work and metabolism depend on coronary blood flow in the pig

1978 ◽  
Vol 234 (5) ◽  
pp. H597-H607 ◽  
Author(s):  
D. F. Stowe ◽  
D. G. Mathey ◽  
W. Y. Moores ◽  
S. A. Glantz ◽  
R. M. Townsend ◽  
...  
Keyword(s):  
Blood Flow ◽  
Carotid Artery ◽  
Myocardial Ischemia ◽  
Mechanical Performance ◽  
Venous Blood ◽  
Lactate Production ◽  
Blood Gases ◽  
Metabolic Effects ◽  
Stroke Work ◽  
Blood Flows

We determined the mechanical and metabolic effects of graded myocardial ischemia in 23 open-chest, anesthetized pigs. By connecting the midportion of the left anterior descending artery (LAD) to the carotid artery via a constant volume, calibrated pump, we reduced the flow in the LAD to 0, 25, 50, and 75% of control rates for periods of 1 h. Flows of 100% and 150% were also examined. Using pairs of ultrasonic crystals to measure segment dimensions, we calculated segment shortening and thickening, and total and systolic stroke work in the ischemic and normally perfused segments. Blood gases, pH, and lactate and inosine balances were determined from the regional coronary venous blood. At coronary blood flows of 0, 25, 50, and 75% of normal resting flow, total segment work was 8 +/- 8, 25 +/- 4, 51 +/- 5, and 80 +/- 6% of control, respectively, while systolic segment work was -2 +/- 5, -10 +/- 5, 40 +/- 5, and 86 +/- 7% of control, respectively (means +/- SE). Thus, the decrease in total segment stroke work is proportional to the decrease in flow over the range 0-100%. However, no useful work (i.e., systolic work) is done until flow exceeds 25%. Segment shortening and thickening are significantly depressed with flows diminished by only 25%. Segmental inosine production correlates with lactate production and parallels decreased mechanical performance.

Integration of jugular venous return and circle of Willis in a theoretical human model of selective brain cooling

2007 ◽  
Vol 103 (5) ◽  
pp. 1837-1847 ◽  
Author(s):  
Matthew A. Neimark ◽  
Angelos-Aristeidis Konstas ◽  
Andrew F. Laine ◽  
John Pile-Spellman
Keyword(s):  
Venous Return ◽  
Mild Hypothermia ◽  
Brain Temperature ◽  
Circle Of Willis ◽  
Human Model ◽  
Anterior Communicating Artery ◽  
Moderate Hypothermia ◽  
Brain Cooling ◽  
Bioheat Equation ◽  
Selective Brain Cooling

A three-dimensional mathematical model was developed to examine the induction of selective brain cooling (SBC) in the human brain by intracarotid cold (2.8°C) saline infusion (ICSI) at 30 ml/min. The Pennes bioheat equation was used to propagate brain temperature. The effect of cooled jugular venous return was investigated, along with the effect of the circle of Willis (CoW) on the intracerebral temperature distribution. The complete CoW, missing A1 variant (mA1), and fetal P1 variant (fP1) were simulated. ICSI induced moderate hypothermia (defined as 32–34°C) in the internal carotid artery (ICA) territory within 5 min. Incorporation of the complete CoW resulted in a similar level of hypothermia in the ICA territory. In addition, the anterior communicating artery and ipsilateral posterior communicating artery distributed cool blood to the contralateral anterior and ipsilateral posterior territories, respectively, imparting mild hypothermia (35 and 35.5°C respectively). The mA1 and fP1 variants allowed for sufficient cooling of the middle cerebral territory (30–32°C). The simulations suggest that ICSI is feasible and may be the fastest method of inducing hypothermia. Moreover, the effect of convective heat transfer via the complete CoW and its variants underlies the important role of CoW anatomy in intracerebral temperature distributions during SBC.

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