Cerebrovascular physiology – article alert #61

Circulation arrest and the brain

305- Cerebral blood flow autoregulation is preserved after hypothermic circulatory arrest – Ono et al.

Hypertension and the brain

306- Assessment of cerebral oxygenation oscillations in subjects with hypertension – Li et al.

Brain monitoring

307- Using bispectral index and cerebral oximetry to guide hemodynamic therapy in high-risk surgical patients – Bidd et al.

Energy drinks and the brain

308- Cardio- and cerebrovascular responses to the energy drink Red Bull in young adults: a randomized cross-over study – Grasser et al.

Spinal cord injury and the brain

309- Regional neurovascular coupling and cognitive performance in those with low blood pressure secondary to high-level spinal cord injury: improved by alpha-1 agonist midodrine hydrochloride – Phillips et al.

News from our research topic on cerebral oxygenation #4

Another update regarding our research topic on cerebral oxygenation.

A fifth paper now available at Frontiers in Physiology !

Effects of aging on the association between cerebrovascular responses to visual stimulation, hypercapnia and arterial stiffness by Daniela Flück, Andrew E Beaudin, Craig D Steinback, Gopukumar Kumarpillai, Nandavar Shobha, Cheryl R McCreary, Stefano Peca, Eric Smith, Marc J Poulin

Go have a look !

Cerebrovascular physiology – article alert #60

Nitrates and the brain

297- Effects of dietary nitrates on systemic and cerebrovascular hemodynamics –  Bond et al.

Brain monitoring

298- Transcranial Doppler Ultrasound: A Review of the Physical Principles and Major Applications in Critical Care – Naqvi et al.

Chronic kidney disease and the brain

299- Cognitive impairment in chronic kidney disease: clinical findings, risk factors and consequences for patient care – Hermann et al.

Exercise and the brain

300- rain the vessel, gain the brain: physical activity and vessel function and the impact on stroke prevention and outcome in cerebrovascular disease – Schmidt et al.

Altitude and the brain

301- AltitudeOmics: Exercise-induced supraspinal fatigue is attenuated in healthy humans after acclimatisation to high altitude – Goodall et al.

Diabetes and the brain

302- Structural and Functional Brain Changes in Middle-Aged Type 2 Diabetic Patients: A Cross-Sectional Study – Garcia-Casares et al.

Aging and the brain

303- Total cerebral blood flow and mortality in old age: a 12-year follow-up study – Sabayan et al.

Spinal cord injury and the brain

304- Perturbed and spontaneous regional cerebral blood flow responses to changes in blood pressure after high level spinal cord injury: the effect of midodrine – Phillips et al.

 

Cerebrovascular physiology – article alert #59

Exercise and the brain

292- Impact of a single bout of aerobic exercise on regional brain perfusion and activation responses in healthy young adults – Macintosh et al.

Obesity and the brain

293- Relationship of obesity and insulin resistance with the cerebrovascular reactivity: a case control study – Rodriguez-Flores et al.

Subarachnoid hemorrhage and the brain

294- Impaired Cerebral Autoregulation Is Associated With Vasospasm and Delayed Cerebral Ischemia in Subarachnoid Hemorrhage – Otite et al.

Fontan circulation and the brain

295- Cerebral Circulation in Patients With Fontan Circulation: Assessment by Carotid Arterial Wave Intensity and Stiffness – Saike et al.

Alzheimer’s disease and the brain

296- Cerebral blood flow is an earlier indicator of perfusion abnormalities than cerebral blood volume in Alzheimer’s disease – Lacalle-Aurioles et al.

Cerebrovascular physiology – article alert #58

Regulation of brain blood flow

285- Integrative regulation of human brain blood flow – Willie et al.

Altitude and the brain

286- AltitudeOmics: Cerebral autoregulation during ascent, acclimatization, and re-exposure to high altitude and its relation with acute mountain sickness – Subhudi et al.

287- AltitudeOmics: Enhanced cerebrovascular reactivity and ventilatory response to CO2 with high altitude acclimatisation and re-exposure – Fan et al.

Syncope and the brain

288- Cerebral blood flow of children with vasovagal syncope – Tugba et al.

Exercise and the brain

289- Cerebrovascular Perfusion among Older Adults is Moderated by Strength Training and Gender – Xu et al.

Insulin resistance and the brain

290- Cerebral blood flow links insulin resistance and baroreflex sensitivity – Ryan et al.

Diabetes and the brain

291- Cerebral Hemodynamics and Systemic Endothelial Function Are Already Impaired in Well-Controlled Type 2 Diabetic Patients, with Short-Term Disease – Palazzo et al.

Utilization of norepinephrine and phenylephrine during cardiopulmonary bypass in diabetics: What is the impact on brain oxygenation ?

Regular readers will remember my interest in the influence of specific vasopressors on cerebral oxygenation. You can have a look at my postdoc work here and posts related to that topic here, here, here, here and here.

We have just published a new study regarding that issue, this time in diabetics undergoing cardiac surgery.  A potential reduction in brain oxygenation following administration of norepinephrine or phenylephrine could elevate the risk of cerebral ischemia in these patients, a clinical population already at risk for the development of vascular cognitive impairments, transient ischemic attack and stroke. Still, we did not know to date the influence of norepinephrine and phenylephrine on cerebral oxygenation measured by near-infrared spectroscopy during cardiopulmonary bypass in diabetics.

Accordingly, we decided to quantify changes in cerebral oxygenation during administration of norepinephrine and phenylephrine during cardiopulmonary bypass in diabetics and non-diabetics (our goal was not to compare the two vasopressors).

To do so, norepinephrine (6 diabetics; 8 non-diabetics) or phenylephrine (8 diabetics; 9 non-diabetics) was administered intravenously to maintain mean arterial pressure above 60 mmHg during cardiopulmonary bypass.

Mean arterial pressure, venous temperature, arterial oxygenation, and cerebral oxygenation were recorded before anesthesia induction (baseline) and continuously during cardiopulmonary bypass.

Interestingly, cerebral oxygenation was lowered to a greater extent in diabetics vs. non-diabetics with the administration of norepinephrine (-14±13% vs. 3±12%; p<0.05), and tended to be lowered to a greater extent in diabetics vs. non-diabetics with the administration of phenylephrine [-12±8% vs. -6±7%; p=0.1] during cardiopulmonary bypass.

Basically, the results of our study suggest that administration of norepinephrine to restore mean arterial pressure during cardiopulmonary bypass is associated with a reduction in cerebral oxygenation (measured by near-infrared spectroscopy) in diabetics but not in non-diabetics. Administration of phenylephrine is associated with a trend towards a greater reduction in cerebral oxygenation in diabetics compared to non-diabetics.

Although these findings are really interesting, we have highlighted some issues in our discussion:

1) Further studies are necessary in order to support our findings while strictly controlling for potential confounders;

2) Further studies are necessary in order to investigate which mechanism is responsible for the reduction in cerebral oxygenation during cardiopulmonary bypass with the utilization of norepinephrine and phenylephrine in these patients;

3) The small number of subjects precludes the generalization of these findings to the whole population of diabetics undergoing cardiac surgery;

4) 60 mmHg is not necessarily the lower limit of cerebral autoregulation for all patients undergoing cardiac surgery. Accordingly, maintaining mean arterial pressure at 60 mmHg represents a potential limitation of this study, since brain blood flow could be (or not) autoregulated at this mean arterial pressure in these patients;

5) The lowering in cerebral oxygenation, measured by near-infrared spectrocopy, following administration of norepinephrine, could partly be explained by changes in skin blood flow.

Reference

Brassard P, Pelletier C, Martin M, Gagné N, Poirier P, Ainslie PN, Caouette M, Bussières JS. Influence of norepinephrine and phenylephrine on frontal lobe oxygenation during cardiopulmonary bypass in patients with diabetes. J Cardiothorac Vasc Anesth. 2013 Dec 17. pii: S1053-0770(13)00513-2. doi: 10.1053/j.jvca.2013.09.006. [Epub ahead of print]