J Astrup

Blood flow and ischemia within traumatic cerebral contusions

OBJECTIVE To provide evidence of irreversible ischemia in cerebral contusions among patients with severe traumatic brain injuries and to clarify the potential viability of tissue in the pericontusional zone, quantitative regional cerebral blood flow (rCBF) measurements obtained with the xenon-enhanced computed tomographic method were correlated with the areas of contusions, by using image fusion. METHODS rCBF measurements obtained during the acute phase (mean, 2 d after injury; range, 0–10 d) were statistically correlated with the extent of tissue necrosis identified as focal atrophy on late follow-up computed tomographic scans (mean time after the xenon-enhanced computed tomographic cerebral blood flow investigation, 265 d; range, 30–1047 d). RESULTS Seventeen patients exhibited 26 traumatic contusions. All contusions progressed to late focal atrophic areas on the follow-up computed tomographic scans. The rCBF values within the traumatic contusions ranged from 0.5 to 22.0 ml/100 g/min, with a mean of 5.9 ± 5.9 ml/100 g/min. The contusions exhibited a specific rCBF profile, presenting as a core of severe lethal ischemia surrounded by variable but gradually increasing perfusion with increasing distance from the ischemic core. CONCLUSION The ischemic profile of the contusions, with a pericontusional zone of low rCBF, presents the potential risk of secondary ischemic insults, similar to the risk in the ischemic penumbral zones surrounding areas of acute ischemic stroke.

In vivo estimation of cerebral blood flow, oxygen consumption and glucose metabolism in the pig by [15O]water injection, [15O]oxygen inhalation and dual injections of [18F]fluorodeoxyglucose

There is a need for suitable non-primate laboratory animals for studies of brain function by positron emission tomography (PET). To provide a comparative index of the circulatory physiology of the pig, we have applied novel PET tracer methodology to seven anaesthetized pigs, and measured cerebral regional oxygen consumption (CMR[O2]), cerebral blood flow (CBF), and cerebral glucose metabolism (CMR[glc]). Blood flow and flow-metabolism couple were estimated for selected cerebral regions of interest. We found an average hemispheric CMR(O2) of 171 +/- 18 micromol/100 cm3/min. Individual hemispheric CBF measurements varied between 33 and 41 ml/100 cm3/min, with an average of 37 +/- 3 ml/100 cm3/min at an average PaCO2 of 4.3 +/- 0.9 kPa. The blood flow dependency on arterial PCO2 was calculated from the results of the carbon dioxide response in two pigs in which the CBF measurements obeyed the equation CBF (ml/100 cm3/min) = 8.9 PaCO2 (kPa). In each pig, CMR(glc) was studied twice with a double-injection FDG method. In the first session, the values of CMR(glc) averaged 27 +/- 3 and 23 +/- 4 micromol/100 cm3/min, estimated by multilinear and linear regression analysis, respectively. In the second session, the corresponding averages were 27 +/- 3 and 24 +/- 3 micromol/100 cm3/min, respectively. The average oxygen extraction fraction was 0.46 +/- 0.09 and the oxygen-glucose ratio was 6.1 +/- 0.8. The findings indicate that the pig is suitable for PET studies of cerebral blood flow, cerebral oxygen consumption and glucose metabolism.

Ultrasound detection in fish—a parallel to the sonar-mediated detection of bats by ultrasound-sensitive insects?

Most bats use ultrasonic sonar signals, or cries, to locate prey. Many of their insect prey species have evolved an ability to hear and respond to these signals, and studies clearly demonstrate the survival value associated with this ability. Like bats, toothed whales locate prey by emitting ultrasonic sonar signals, or clicks. As a parallel to the insect prey of bats, it would seem obvious to assume that some fish species likewise are capable of sensing the ultrasonic clicks of their odontocete predators. As judged from classical fish audiometry literature, this seems not to be the case, however, and although in recent years some fishes have been proven responsive to ultrasound, examination of ecological and acoustic differences reveals that conclusions on ultrasound-mediated insect escape behavior are not immediately applicable to fish. This has the consequence that future experiments on fish ultrasound detection should not be looking for observations directly parallel to those observed in the bat-insect interactions.

No influence of the endothelin receptor antagonist bosentan on basal and indomethacin-induced reduction of cerebral blood flow in pigs

Background: The mechanism behind indomethacin‐induced cerebral vasoconstriction is incompletely understood. We tested the hypothesis that the mixed endothelin‐1 receptor antagonist bosentan would modify or prevent indomethacin‐induced reduction of CBF in the anaesthetized pig. Furthermore, we investigated the effect of bosentan on resting CBF and CMRO2.