Cerebral vascular effects of non-invasive laserneedles measured by transorbital and transtemporal Doppler sonography

. Laserneedles represent a new non-invasive optical stimulation method which is described for the first time in this paper. We investigated 27 healthy volunteers (mean age±SD: 25.15±4.12 years; range: 21–38 years; 14 female, 13 male) in a randomised cross-over trial to study differences between laserneedle acupuncture and manual needle acupuncture in specific cerebral parameters. Mean blood flow velocity (v _m) showed specific and significant increases in the ophthalmic artery during laserneedle stimulation (p=0.01) and during manual needle stimulation (p<0.001) at vision-related acupoints. At the same time insignificant alterations in v _m were found in the middle cerebral artery for both acupuncture methods. The eight laserneedles used in this study were arranged at the end of the optical fibres. Each fibre was connected to a semiconductor laser diode emitting at 685 nm with a primary output power of about 55 mW. Optical stimulation using properly adjusted laserneedles has the advantage that the stimulation can hardly be felt by the patient and the operator may also be unaware of whether the laserneedle system is active, and therefore true double blind studies in acupuncture research can be performed. Paper received 18 March 2002; accepted after revision 2 May 2002. Correspondence to: Prof. G. Litscher, Department of Biomedical Engineering and Research in Anesthesia and Critical Care, University of Graz, Auenbruggerplatz 29, LKH, A-8036 Graz/Austria. Tel.: +43 316 385-3907, -83907; Fax: +43 316 385-3908; e-mail: gerhard.litscher@uni-graz.at     

Acupuncture using laser needles modulates brain function: first evidence from functional transcranial Doppler sonography and functional magnetic resonance imaging

Acupuncture using laser needles is a new totally painless stimulation method which has been described for the first time. This paper presents an experimental double-blind study in acupuncture research in healthy volunteers using a new optical stimulation method. We investigated 18 healthy volunteers (mean age±SD: 25.4±4.3 years; range: 21–30 years; 11 female, 7 male) in a randomized controlled cross-over trial using functional multidirectional transcranial ultrasound Doppler sonography (fTCD; n=17) and performed functional magnetic resonance imaging (fMRI) in one volunteer. Stimulation of vision-related acupoints resulted in an increase of mean blood flow velocity in the posterior cerebral artery measured by fTCD [before stimulation (mean±SE): 42.2±2.5; during stimulation: 44.2±2.6; after stimulation: 42.3±2.4 cm/s, n.s.]. Mean blood flow velocity in the middle cerebral artery decreased insignificantly. Significant changes (p<0.05) of brain activity were demonstrated in the occipital and frontal gyrus by fMRI. Optical stimulation using properly adjusted laser needles has the advantage that the stimulation cannot be felt by the patient (painless and no tactile stimulation) and the operator may also be unaware of whether the stimulation system is active. Therefore true double-blind studies in acupuncture research can be performed.     

Laser Doppler flowmetry of focal ischaemia and reperfusion in deep brain structures in rats

Summary Monitoring cerebral blood flow during focal ischaemia and reperfusion with established techniques such as hydrogen clearance and autoradiography is difficult. Laser Doppler flowmetry is a new technique, it allows one to continuously measure blood flow in small tissue samples. The objective of this study was to compare laser Doppler flowmetry with hydrogen clearance using a new single fiber probe to obtain measurements in deep brain structures and then to show the temporal profile of cerebral blood flow during focal ischaemia and after reperfusion.First, the single fiber laser Doppler method was compared with the hydrogen clearance method in ten Wistar rats.Second, focal cerebral ischaemia was induced in fifteen Wistar rats using a model of middle cerebral artery occlusion based on the intravascular insertion of a nylon suture; reperfusion occurred after withdrawal of the suture. The laser Doppler probe was placed in the lateral caudatoputamen, and local cerebral blood flow was measured continuously before and during occlusion as well as after reperfusion.The relative blood flow values obtained by the laser Doppler method and the hydrogen clearance method showed a good correlation (r=0.76) and a linear relationship. A rapid decrease in laser Doppler flowmetry to 42±16% of former baseline values was seen with occlusion of the middle cerebral artery; during occlusion cerebral blood flow remained at this level. Reperfusion resulted in a heterogeneous pattern of cerebral blood flow as laser Doppler flowmetry values ranged from 25% to 134% of baseline values.The effects of middle cerebral artery occlusion and reperfusion on cerebral blood flow can be monitored on-line with laser Doppler flowmetry. Our findings suggest that this method, with the high spatial and temporal resolution characteristics of its new single fiber probe, allows one to continuously measure microcirculatory blood flow in deep brain structures.Supported in part by the Deutsche Forschungsgemeinschaft (Ku 294/18-1) and by Schering AG, Berlin, Federal Republic of Germany.     

Laser acupuncture induced specific cerebral cortical and subcortical activations in humans

As recent studies demonstrated, acupuncture can elicit activity in specific brain areas. This study aims to explore further the central effect using laser acupuncture. We investigated the cerebral effects of laser acupuncture at both acupoints GB43 with functional magnetic resonance imaging (fMRI). As a control condition the laser was mounted at the same acupoints but without application of laser stimulation. The group results showed significant brain activations within the thalamus, nucleus subthalamicus, nucleus ruber, the brainstem, and the Brodmann areas 40 and 22 for the acupuncture condition. No significant brain activations were observed within the placebo condition. The activations we observed were laser acupuncture-specific and predominantly ipsilateral. This supports the assumption that acupuncture is mediated by meridians, since meridians do not cross to the other side. Furthermore, we could show that laser acupuncture allows one to design a pure placebo condition.     

Transcranial laser stimulation improves human cerebral oxygenation

Background and Objective

Transcranial laser stimulation of the brain with near‐infrared light is a novel form of non‐invasive photobiomodulation or low‐level laser therapy (LLLT) that has shown therapeutic potential in a variety of neurological and psychological conditions. Understanding of its neurophysiological effects is essential for mechanistic study and treatment evaluation. This study investigated how transcranial laser stimulation influences cerebral hemodynamics and oxygenation in the human brain in vivo using functional near‐infrared spectroscopy (fNIRS).

Materials and Methods

Two separate experiments were conducted in which 1,064‐nm laser stimulation was administered at (1) the center and (2) the right side of the forehead, respectively. The laser emitted at a power of 3.4 W and in an area of 13.6 cm², corresponding to 0.25 W/cm² irradiance. Stimulation duration was 10 minutes. Nine healthy male and female human participants of any ethnic background, in an age range of 18–40 years old were included in each experiment.

Results

In both experiments, transcranial laser stimulation induced an increase of oxygenated hemoglobin concentration (Δ[HbO₂]) and a decrease of deoxygenated hemoglobin concentration (Δ[Hb]) in both cerebral hemispheres. Improvements in cerebral oxygenation were indicated by a significant increase of differential hemoglobin concentration (Δ[HbD] = Δ[HbO₂] ? Δ[Hb]). These effects increased in a dose‐dependent manner over time during laser stimulation (10 minutes) and persisted after laser stimulation (6 minutes). The total hemoglobin concentration (Δ[HbT] = Δ[HbO2] + Δ[Hb]) remained nearly unchanged in most cases.

Conclusion

Near‐infrared laser stimulation applied to the forehead can transcranially improve cerebral oxygenation in healthy humans. Lasers Surg. Med. 48:343–349, 2016. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

     

Laser doppler flowmetry in combined needle acupuncture and moxibustion: a pilot study in healthy adults

Laser Doppler flowmetry (LDF) (DRT 4/Moor Instruments Ltd, Devon, UK) was used in this pilot study for monitoring the effects of an invariable acupuncture pattern on microcirculation of the skin before, during, and after combined needle acupuncture and moxibustion in 12 healthy volunteers (mean age 35.2±4.4 years, range 26–41 years, four female and eight male). According to the standards of traditional Chinese medicine (TCM), this acupuncture pattern is assumed to be unspecific and non-therapeutic. Flux decreased during the treatment period (p<0.05) compared to the control phase before combined needle acupuncture and moxibustion. After the removal of the needles, flux did not return to the initial control value. No significant differences between mean arterial blood pressure, heart rate, skin temperature or gender were detected. A prediction of individual incidences and kinds of acupuncture effects in our healthy volunteers was not possible. Modern monitoring techniques like LDF could be a method to separate responders from non-responders to acupuncture in peripheral microcirculatory disorders. Further studies on patients with peripheral microcirculatory disorders are necessary in order to demonstrate the value of LDF in detecting responders/non-responders in combination with therapeutic acupuncture patterns according to TCM. Paper received 13 September 2000; accepted after revision 2 October 2000.     

皮层扩散性抑制预处理对大鼠脑缺血性损伤的保护作用

目的研究KCl诱导皮层扩散性抑制（CSD）预处理对大鼠大脑中动脉阻塞后脑血流灌注和梗死体积的影响，验证CSD对脑缺血性损伤的保护作用。方法24只SD大鼠分为实验组和对照组，各12只，试验组用5mol／L KCl大鼠大脑皮层诱发CSD，3d后插线法栓塞大脑中动脉制备大鼠局灶性脑缺血模型，利用激光散斑衬比光学成像技术监测缺血2h大脑血流动力学变化，并测定大脑梗死病灶体积。对照组用NaCl代替KCl，其余相同。比较血流动力学变化和大脑梗死灶体积的大小。结果经CSD预处理后3d再缺血时，实验组缺血病灶血液灌注水平高于对照组，实验组总梗死体积及皮层梗死体积均小于对照组，皮层下梗死体积与对照组差异无统计学意义（P〉0．05）。结论利用激光散斑衬比光学成像技术可以在体检测脑血流的变化，同时验证了CSD预处理可提高缺血病灶皮层的血液灌注水平，减少总梗死体积和皮层梗死体积，可以减轻脑缺血后的脑功能损害程度。     

Changed Skin Blood Perfusion in the Fingertip Following Acupuncture Needle Introduction as Evaluated by Laser Doppler Perfusion Imaging

Rapidly repeated imaging of the left middle fingertip skin blood perfusion was performed in 51 healthy volunteers (mean age±SD: 25.3±7.6 years) prior to, immediately after and in the early reperfusion phase following introduction of an acupuncture needle at the Neiguan point (Pe. 6) and at a placebo point respectively, using a Laser Doppler Perfusion Imager (LDPI). The average skin perfusion of the fingertip was calculated for each image and used as an indicator of the microvascular response to the acupuncture needle introduction. The results of this randomised, placebo-controlled, cross-over study showed significant differences (p≤0.001) in the immediate skin blood perfusion response when needling is performed in an acupuncture point (Neiguan) and a placebo point, with a more pronounced reduction in skin blood perfusion when needling the acupuncture point. In the early reperfusion phase, however, a substantial increase in skin perfusion was observed that amounted to about 18% of the level prior to needle introduction, irrespective of the site of needle application. In a single individual it was demonstrated that the vasodilatation following needling in the acupuncture point persisted for a more extended time period. These results suggest that the LDPI technology may be useful in visualising and quantifying the peripheral vascular effects of acupuncture on the microcirculation. Paper received 10 July 2001; accepted after revision 24 August 2001.     

Effect of controlled blood pressure increase on cerebral blood flow velocity and oxygenation in patients with subarachnoid haemorrhage

Background

Patients with aneurysmal subarachnoid haemorrhage (SAH) might have impaired cerebral autoregulation, that is, CBF – and thereby oxygen delivery – passively increase with an increase in CPP. This physiological study aimed to investigate the cerebral haemodynamic effects of controlled blood pressure increase in the early phase after SAH before any signs of delayed cerebral ischaemia (DCI) occurred.

Methods

The study was carried out within 5 days after ictus. Data were recorded at baseline and after 20 min of noradrenaline infusion to increase mean arterial blood pressure (MAP) by a maximum of 30 mmHg and to an absolute level of no more than 130 mmHg. The primary outcome was the difference in middle cerebral artery blood flow velocity (MCAv) measured by transcranial Doppler (TCD), while differences in intracranial pressure (ICP), brain tissue oxygen tension (PbtO₂), and microdialysis markers of cerebral oxidative metabolism and cell injury were assessed as exploratory outcomes. Data were analysed using Wilcoxon signed-rank test with correction for multiplicity for the exploratory outcomes using the Benjamini-Hochberg correction.

Results

Thirty-six participants underwent the intervention 4 (median, IQR: 3–4.75) days after ictus. MAP was increased from 82 (IQR: 76–85) to 95 (IQR: 88–98) mmHg (p-value: <.001). MCAv remained stable (baseline, median 57, IQR: 46–70 cm/s; controlled blood pressure increase, median: 55, IQR: 48–71 cm/s; p-value: .054), whereas PbtO₂ increased significantly (baseline, median: 24, 95%CI: 19–31 mmHg; controlled blood pressure increase, median: 27, 95%CI: 24–33 mmHg; p-value <.001). The remaining exploratory outcomes were unchanged.

Conclusion

In this study of patients with SAH, MCAv was not significantly affected by a brief course of controlled blood pressure increase; despite this, PbtO₂ increased. This suggests that autoregulation might not be impaired in these patients or other mechanisms could mediate the increase in brain oxygenation. Alternatively, a CBF increase did occur that, in turn, increased cerebral oxygenation, but was not detected by TCD. Trial registration: clinicaltrials.gov (NCT03987139; 14 June 2019).     

Alterations of Norepinephrine Levels in Plasma and CSF of Patients After Traumatic Brain Injury in Relation to Disruption of the Blood-Brain Barrier

Summary  Background. In injured brain tissue with a disrupted blood-brain barrier (BBB) catecholamines such as norepinephrine (NE) are known to enhance glucose consumption and cerebral blood flow but may lead to an energy depletion increasing the risk of ischemia. Therefore it is of great interest whether the exogenous administration of NE used mainly to maintain an adequate cerebral perfusion pressure influences CSF NE levels or not, and whether elevated plasma or CSF leves of NE can influence the actual clinical condition. We addressed this issue by measuring the levels of NE in CSF and plasma and correlating them with the actual clinical condition of the patients.  Methods. In 29 patients with severe TBI (<8 points on the Glasgow Coma cale, GCS) NE levels were analysed by high performance liquid chromatography (HPLC) in paired blood and CSF specimens which were collected from days 1 to 14 after severe TBI (total number of pairs=121). The integrity of the BBB was evaluated by determining the CSF/serum albumin ratio. The clinical condition of the patients was assessed by GCS.  Results. Elevated plasma and CSF NE levels were observed in 50% of all samples, most consistently in patients treated with NE. NE elevation in CSF was independent of whether or not the BBB remained intact. There was no correlation between GCS and the levls of NE in CSF or plasma either in samples from the treated or the untreated group.  Interpretation. Exogenous administration of NE seems to increase NE levels in plasma and CSF. However, in this group of patients with severe TBI there was no clincal evidence that exogenous administration of NE was detrimental to the traumatized patients.     

Influence of external cardiac pacing on cerebral oxygenation measured by near‐infrared spectroscopy in children after cardiac surgery

Background: The brain of children in the early period after repair of congenital heart defects with cardiopulmonary bypass (CPB) may be more vulnerable to hemodynamic changes because of impaired cerebral autoregulation. During postoperative testing of the external temporary safety pacer, we performed desynchronizing ventricular pacing (VVI) while monitoring cerebral oxygenation using near‐infrared spectroscopy (NIRS). Methods: We prospectively investigated 11 children (6 girls, 5 boys). Mean age was 6.1 months (±3.8 months) and mean weight: 5.3 kg (±1.5 kg). We performed measurements at four study steps: baseline I, VVI pacing, baseline II and atrial pacing (AOO) to exclude effects of higher heart rate. We continuously measured the effects on hemodynamic and respiratory parameters as well as on cerebral tissue oxygenation index (TOI). Hemoglobin difference (HbD) was calculated as a parameter for cerebral blood flow (CBF). Results: Ventricular pacing leads to a significant decrease in arterial blood pressure and central venous saturation accompanied by an immediate and significant decrease in TOI (63.3% ± 7.6% to 61.5% ± 8.4% [P < 0.05]) and HbD (0.51 ± 1.8 μmol·l⁻¹ to −2.9 ± 4.7 μmol·l⁻¹ [P < 0.05]). Conclusion: Cardiac desynchronization after CPB seems to reduce CBF and cerebral oxygenation in children.     

The Application of Transcranial Doppler Sonography in Patients with Chronic Subdural Haematoma

Summary  The aim of this study was to evaluate the haemodynamic changes of the middle cerebral artery (MCA) and their clinical significance before and after surgical aspiration in patients with chronic subdural haematoma (CSDH).  Nineteen patients with CSDH (17 unilateral and 2 bilateral) received transcranial Doppler sonography (TCD) examinations for cerebral blood flow velocity (CBFv) of the MCA prior to and 5 days after neurosurgical treatment. A total of 21 lesion and 10 non-lesion hemispheres were included. Cranial computerized tomography (CT) and clinical assessments were performed before and 3 months following surgery.  The preoperative TCD study revealed that the lesion hemisphere had a modest decrease in CBFv in the MCA as compared to the non-lesion hemisphere. Postoperatively, the CBFv significantly improved in the lesion hemisphere, but not in the non-lesion hemisphere, compared to the preoperative data (P<0.005). The improvement in CBFv showed no significant correlation with brain shift and haematoma volume of the initial cranial CT. Additionally, two patients, who were proved to have a postoperative complication of subdural pneumocephalus, failed to attend follow-up examinations of TCD.  Our results support TCD as an alternative follow-up examination for patients with CSDH, although it may not be sensitive enough as a preoperative screening tool. Postoperatively, improvements in the CBFv of the lesion hemisphere are characteristic. An unexplained difficulty of accessing cerebral basal arteries in follow-up TCD examinations should suggest pneumocephalus in the primary differential diagnosis.     

Adrenomedullin Reduces Ischemic Brain Injury after Transient Middle Cerebral Artery Occlusion in Rats

Summary  Background. The effect of adrenomedullin, a vasodilatory peptide on transient middle cerebral artery (MCA) occlusion was investigated in rats.  Methods. Transient MCA occlusion for 2 hours was made by using the intra-arterial suture method, followed by reperfusion.  Findings. An intravenous infusion of adrenomedullin (1 μ g/kg/min) from one hour before ischemia to one hour after ischemia significantly reduced the infarct size and improved neurological deficits (p<0.05), without affecting systemic blood pressure or other physiological parameters. The infarct size was reduced with adrenomedullin by 25.4±12.7%, 31.3±5.8%, 31.6±6.1% respectively at the coronal level 6, 8 and 10 mm posterior from the frontal pole. Adrenomedullin also significantly inhibited the increase in myeloperoxidase (MPO) activity in the MCA area of the ischemic hemisphere after 22-hour reperfusion (control: 0.205±0.054 unit/g wet tissue, adrenomedullin group: 0.047±0.009 unit/g wet tissue, p<0.0001).  Interpretation. These data suggest that adrenomedullin reduces acute ischemic brain injury and one of is neuroprotective mechanisms may be derived from inhibition of the infiltration of neutrophils into the ischemic tissue.     

Leflunomide prevents vasospasm secondary to subarachnoid haemorrhage

Summary Background. Though cerebral vasospasm is one of the most serious complications of subarachnoid haemorrhage (SAH), its complex pathogenesis is poorly understood and available clinical treatment options are unsatisfactory. This study was designed to examine the efficacy of leflunomide, an immunomodulatory agent with inhibitory properties, on vascular smooth muscle cell proliferation and inflammation in a rabbit cerebral vasospasm model. Methods. Twenty-two adult New-Zealand rabbits were assigned to 4 groups: control, SAH, SAH plus vehicle, SAH plus leflunomide. Subarachnoid haemorrhage was induced by administration of 1 ml of fresh unheparinised autologous arterial blood into the cisterna magna. Oral leflunomide (2 mg/kg) or vehicle treatment was started 12 h after the induction of subarachnoid haemorrhage and administered once a day. Three days later, the animals were sacrificed and the basilar artery was examined histologically for the lumen area and the thickness of the vessel wall. Inflammatory reaction was also examined by counting white blood cells within the vessel wall by means of light microscopic examination using haematoxylin and eosin staining. Findings. Severe and moderate vasospasms were detected in the basilar artery of the SAH and SAH plus vehicle treated groups, respectively. Leflunomide effectively reduced the vasospasm of the basilar artery. Compared to the vehicle treated group, leflunomide significantly reduced the lumen area (p < 0.01) and hyperplasia of the vessel wall (p < 0.01). Although inflammatory response within the vessel wall was reduced in the leflunomide treated group, no statistical significance was found between groups (p = 0.07). Conclusion. This study demonstrates for the first time that leflunomide treatment attenuates cerebral vasospasm in a rabbit SAH model while inflammatory reaction in the vessel wall is not affected. Although further studies are needed to reveal its molecular mechanisms in relieving vasospasm, leflunomide may provide a therapeutic potential for human cerebral vasospasm induced by SAH.     

Myocardial revascularization in patients with end-stage renal disease: Comparison of percutaneous transluminal coronary angioplasty and coronary artery bypass grafting

Background: Ischemic heart disease is the major cause of death inpatients with end-stage renal disease. The high prevalence of coronary artery disease results in a rising number of dialysis patients requiring myocardial revascularisation. Objective: The objective of this study was to compare the outcomes of recurrent angina, myocardial infarction, rate of reinterventions and cardiovascular death following percutaneous coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) inpatients with end-stage renal disease. Patients and methods: In a retrospective investigation 40 patients with chronic renal failure undergoing primarily PTCA and 65 patients undergoing CABG were included. Both groups were comparable for gender, duration on dialysis and the number of cardiovascular risk factors per patient. Patients undergoing PTCA were younger (53 ± 12 years vs. 57 ± 8 years; p < 0.05) and more often diabetics (30% vs. 14%; p < 0.05). Results: Most patients in both groups had a multi-vessel disease (95% in the CABG group vs. 74% in the PTCA group), in the CABG group there were significantly more patients with a triple-vessel disease (62% with vs. 40%in the PTCA group; p < 0.01), PTCA was primarily successful in 95% of the patients while complete revascularization was achieved in 88% of patients undergoing CABG. The perioperative mortality after CABG was 4.8% as compared to none after interventional revascularisation. The cumulative freedom of angina after 6, 12 and 24 months after intervention was significantly lower after PTCA (54%, 40%, 29%) than after bypass grafting (97%, 94%, 90%, p < 0.001). The frequency of reinterventions following PTCA was significantly higher compared to patients following CABG (p < 0.001). After PTCA 15 patients needed further revascularisations, 8 of them underwent CABG, whereas after CABG only two patients required additional myocardial revascularisation. There was no significant difference in the overall mortality between both groups; the survival rate after 12 and 24 months was 95% and 82% after PTCA and 93% and 86% after CABG, respectively. Condition: Although patients receiving CABG had a more severe coronary artery disease the overall mortality was comparable and clinical and functional outcome was improved compared to patients after coronary angioplasty. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phase shift and correlation coefficient measurement of cerebral autoregulation during deep breathing in traumatic brain injury (TBI)

Summary Background. Impairment of cerebral autoregulation is known to adversely affect outcome following traumatic brain injury (TBI). The phase shift (PS) method of cerebral autoregulation (CA) assessment describes the time lag between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in the middle cerebral artery. An alternative method (Mx-ABP) is based on the statistical correlation between ABP and CBFV waveforms over time. We compared these two indices in a cohort of severely head injured patients undergoing controlled, 6-breaths-per-minute ventilation. Methods. PS and Mx-ABP were calculated from 33 recordings of CBFV and MAP in 22 patients with TBI. Spearman’s correlation coefficient was used to assess the agreement between PS and Mx-ABP. The relationship between ICP slow wave amplitude, MAP slow wave amplitude and mean ICP was also examined. Findings. Mean values for Mx-ABP and PS were 0.44 ± 0.27, and 49 ± 26 (degrees), respectively. PS correlated significantly with Mx-ABP (r = −0.648, p < 0.001). A Bland-Altman plot of normalised Mx-ABP and Phase Shift values showed no significant bias or relationship (mean difference = 0.0004, r = −0.037, p = 0.852). During the test procedure, ICP fluctuated in an approximately sinusoidal fashion, with a mean amplitude of 4.96 ± 2.72 mmHg (peak to peak). The magnitude of ICP fluctuation during deep breathing correlated weakly but significantly with mean ICP (r = 0.391, p < 0.05) and with the amplitude of ABP fluctuations (r = 0.625, p < 0.0005). Conclusions. Phase shift and Mx-ABP in TBI are well correlated. Deep breathing presents as an effective tool with which to assess autoregulation using the phase shift method. Correspondence: Philip M. Lewis, BappSc, Scientific Officer, Department of Neurosurgery, Alfred Hospital, P.O. Box 315, Prahran, VIC 3181, Australia.     

Cerebral blood oxygenation changes induced by bypass blood flow in moyamoya disease and non-moyamoya cerebral ischaemic disease

Summary Background. Superficial temporal artery–middle cerebral artery (STA–MCA) anastomosis has been used to prevent stroke in patients with moyamoya disease (MD) and non-moyamoya ischaemic disease (non-MD). However, little is yet known regarding the difference between these groups of patients in the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO), or the temporal changes after surgery. In the present study, we evaluated the CBO changes induced by bypass blood flow in patients with MD and non-MD during the peri-operative periods employing optical spectroscopy. Methods. We investigated 13 patients who underwent STA–MCA anastomosis, including 5 MD and 8 non-MD patients. We evaluated the effects of STA blood flow on the CBO in the MCA territory on the anastomosis side, employing visual light spectroscopy during surgery and near infrared spectroscopy (NIRS) at one week after surgery. Findings. In 4 MD patients and one non-MD patient, the STA blood flow increased the oxyhaemoglobin and cortical oxygen saturation (CoSO₂), indicating that the bypass supplied blood flow to the ischaemic brain; the CBO changes were observed more frequently in MD than in non-MD patients (p < 0.02). The pre-anastomosis CoSO₂ (65.4 ± 5.4%) in MD was significantly lower than that (72.8 ± 7.6%) in non-MD (p < 0.05). Postoperative NIRS demonstrated that the bypass began to supply blood flow to the brain in 5 non-MD patients whose bypass did not supply blood flow during surgery. Conclusions. Although MD has vessels of small diameter as compared to non-MD, the bypass begins to supply blood flow to the ischaemic brain earlier in MD than in non-MD after anastomosis. The fact that the CoSO₂ in MD was lower than that in non-MD suggested that the perfusion pressure in MD was lower than that in non-MD, and this might account for the difference in the bypass blood supply after anastomosis between MD and non-MD. Our data suggest that, even if the bypass does not supply blood to the brain during surgery in non-MD, the bypass blood flow gradually increases after surgery.     

Decrease in Intraoperative Brain Surface Temperature in Patients with Subarachnoid Haemorrhage

Summary  Background. Recent experimental and clinical evidence of hypothermic protection against neuronal injury creates new interests regarding human brain temperature. However, very little information is available for the brain temperature under certain pathological conditions. In this study, intra-operative brain temperature in patients with subarachnoid haemorrhage (SAH) is particularly addressed.  Methods. Brain surface temperature and oxygen saturation of jugular bulb (SjO₂) were monitored during early surgery undergone within 48 hours after the onset in patients with SAH (n=16). Those were also measured in patients with unruptured aneurysms during elective surgery as control (n=15).  Findings. The brain surface temperature was significantly lower in SAH than control (35.3±0.8 vs. 36.1±0.5°C, P<0.01). The reduction in brain surface temperature was correlated with the severity of the Hunt and Kosnik's aneurysmal grade (r=0.837, P<0.01). SjO₂ was significantly lower in SAH than control (51.5±7.3 vs. 68.5±7.6%, P<0.01), and was positively correlated with brain surface temperature (r=0.642, P<0.01).  Interpretation. These results suggest that the brain temperature and/or the temperature gradient within the brain may be altered in an early period after SAH. Since brain temperature is determined by cerebral blood flow (CBF), metabolism, temperature of both circulating blood and surrounding environment, the brain surface temperature reduction may be explained by depressed CBF and metabolism in SAH.     

Normal values of volume flow in the internal carotid artery measured by a new angle-independant Doppler technique for evaluating cerebral perfusion

Summary Background. Cerebral blood flow is an important parameter when monitoring critically ill patients. Blood flow volume within the internal carotid artery (ICA) was shown to be correlated with the cerebral blood flow. The aim of our study was to provide normal values of the internal carotid artery volume flow using this new technology (QuantixND, Cardiosonix Ltd., Israel).Method. The QuantixND System is an angle-independant Doppler system that employs two digital high resolution ultrasound heads within one probe in an defined angle to each other. Thus several flow velocities within the vessel and the vessel diameter can be measured. 77 healthy patients (41 women, 36 men) were included and divided into age groups of ten-year intervals (mean age 48.9 years). Internal carotid artery flow was evaluated as well as physiological and hematological parameters (hematocrit, arterial blood pressure etc).Findings. We found that the blood flow volume in the ICA decreased significantly with age. No side-to-side effects as well as no gender-related differences could be observed. There was no influence of hemoglobin, hematocrit and blood pressure in this healthy population.Conclusions. There is an age-related decrease in blood flow volume with age that can be easily and exactly determined by the use of the new angle-independant doppler technique.