Continuous monitoring of jugular bulb oxygen saturation as a measure of the shunt flow of cerebral arteriovenous malformations

Role of Multimodal Cerebral Oximetry Monitoring in the Anesthetic Management of a Patient With High-Grade Intracranial Arteriovenous Malformation: A Case Report

Near-infrared spectroscopy (NIRS) is a noninvasive monitor of regional brain tissue oxygenation, and jugular venous oximetry (SjvO2) is a monitor of global cerebral oxygenation. We report the role of intraoperative multimodal monitoring of cerebral oxygenation in the anesthetic management of a patient with grade III intracranial arteriovenous malformation (AVM) presenting for surgical excision. Real-time monitoring of cerebral oxygenation is of much relevance in high-grade AVMs where anesthetic management is focused on neuroprotection and prevention of cerebral hypoxia. Besides, it also helps in prediction, early detection, and judicious management of perioperative complications, which are commonly encountered in high-grade AVMs.

Susceptibility-Based Neuroimaging: Standard Methods, Clinical Applications, and Future Directions

The evaluation of neuropathologies using MRI methods that leverage tissue susceptibility have become standard practice, especially to detect blood products or mineralization. Additionally, emerging MRI techniques have the ability to provide new information based on tissue susceptibility properties in a robust and quantitative manner. This paper discusses these advanced susceptibility imaging techniques and their clinical applications.

Anesthesia considerations and intraoperative monitoring during surgery for arteriovenous malformations and dural arteriovenous fistulas

The anesthetic considerations for surgical resection of arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs) incorporate many principles that are common to craniotomies for other indications. However, a high-flow, low-resistance shunt results in chronic hypoperfusion of adjacent brain tissue that is vulnerable to ischemia and at high risk for hyperemia and hemorrhage as resection of the lesion redirects blood flow. A comprehensive understanding of AVM pathophysiology and rapidly titratable anesthetic and vasoactive agents allow the anesthesiologist to alter blood pressure targets as resection evolves for optimal patient outcome. Intensive management is continued post-operatively as the brain acclimatizes to new parameters.

Spinal arteriovenous malformation: evaluation of change in venous oxygenation with susceptibility-weighted MR imaging after treatment

PURPOSE

To evaluate the efficacy of susceptibility-weighted (SW) magnetic resonance (MR) imaging for the assessment of the posttreatment change in oxygen saturation in the draining vein in patients with spinal arteriovenous malformation (AVM).

MATERIALS AND METHODS

The study protocol was approved by the institutional review board, and written informed consent was obtained from all subjects. SW imaging was performed in 11 patients with spinal AVM before and after surgical or endovascular treatment. Eleven healthy subjects were included as a control group. A four-grade response scale was used for the visual assessment of the anterior spinal vein (ASV). For quantitative analysis, the phase value of the ASV was measured and oxygen saturation was calculated. Nonparametric multigroup comparison for visual assessment and one-way analysis of variance for quantitative measurement of oxygen saturation were used as statistical tests for comparison among three groups (pretreatment patients, posttreatment patients, and control subjects).

RESULTS

Complete shunt occlusion in all patients was confirmed by using conventional angiography. For visual assessment, the average score of the pretreatment group was significantly less than that of the posttreatment and control groups. For quantitative analysis, the average oxygen saturation of the pretreatment group was significantly higher than that of the posttreatment and control groups, while no significant difference was observed between the posttreatment and control groups.

CONCLUSION

After treatment, normalization of increased oxygen saturation was noninvasively observed by using SW imaging in patients with spinal AVM. SW imaging can be a useful tool for the assessment of treatment efficacy in patients with spinal AVM. (c) RSNA, 2010.

Detection of normal spinal veins by using susceptibility-weighted imaging

PURPOSE

To evaluate the visualization of the spinal veins using susceptibility-weighted imaging (SWI).

MATERIALS AND METHODS

A 1.5-T magnet equipped with a spine matrix coil was used. Axial SWI scans of 20 healthy volunteers were obtained with a three-dimensional fast low-angle shot (3D-FLASH) sequence. Maximum intensity projection (MIP) of the phase images were reconstructed and five MIP images (at the levels of T11, T11/12, T12, T12/L1, and L1) were selected for the evaluation. The anterior median vein (AMV), posterior median vein (PMV), anterior radiculomedullary vein (ARV), posterior radiculomedullary vein (PRV), and sulcal vein (SV) were evaluated using a 4-grade scale (0, none; 1, weak; 2, moderate; and 3, prominent).

RESULTS

The AMV was detected in all the subjects (100%). The detection rates of the other veins were lower: PMV, 65%; right ARV, 45%; left ARV, 15%; right PRV, 10%; left PRV, 30%; and SV, 0%. The average scores for AMV, PMV, right ARV, left ARV, right PRV, left PRV, and SV were 0.98, 0.24, 0.20, 0.08, 0.08, 0.14, and 0, respectively.

CONCLUSION

SWI of the spine is feasible. The extrinsic spinal veins can be visualized by SWI without using contrast materials.

Anesthetic considerations for intraoperative management of cerebrovascular disease in neurovascular surgical procedures

Despite new surgical methods and interventions a considerable number of patients who undergo neurovascular procedures emergently or electively have substantial mortality, morbidity, and disability. Sound knowledge of pathophysiology of cerebral hypoperfusion, reliable and timely information from monitoring devices, and appropriate choice of therapeutic intervention is essential for successful anesthetic management of these patients. The management of perioperative vasospasm and temporary ischemia during aneurysm clipping require an understanding of cerebral vascular pathophysiology and neuroprotective measures.

[Intraoperative detection of ischemic brain hypoxia using oxygen tissue pressure microprobes]

OBJECTIVE AND IMPORTANCE

Detection of intraoperative ischemic events could lead to the resolution of their cause and to the prevention of the definitive establishment of a postoperative infarct. We want to illustrate the possibilities that intraoperative monitoring of oxygen tissue pressure (PtiO2) in critical areas during a neurosurgical vascular procedure offers, enhancing its reliability and immediacy in obtaining information about tissue oxygenation status as a marker of ischemia in the vascular territory at risk.

CLINICAL PRESENTATION

We report the case of a 32 year-old male with a deep arteriovenous malformation (AVM) localised in the insular region. The patient had been previously treated with radiosurgery without achieving a satisfactory result.

INTERVENTION

AVM removal was performed through a transylvian transinsular approach. PtiO2 was monitorised at the temporal pole (reference area) and at the posterior temporal region (risk area). Both probes maintained close tissue oxygenation levels until the last stage of the AVM resection when, during the coagulation of a supposed afferent vessel, a brisk fall of the oxygen tissue pressure in the posterior temporal region was detected. An ischemic infarct in this area was observed postoperatively.

CONCLUSIONS

PtiO2 monitoring has a high reliability in the detection of intraoperative tissue hypoxia. Data obtained could lead to early identification of these events and, whatever possible, to resolve this situation preventing the definitive establishment of an ischemic infarct.

Intracerebral steal phenomenon associated with global hyperemia in moyamoya disease during revascularization surgery

OBJECT

The collateral vessels in moyamoya disease appear to retain their ability to constrict during hypocapnia but not to dilate during hypercapnia. It has been claimed that hypercapnia, as well as hypocapnia, decreases the blood flow in regions perfused by collateral vessels, presumably because of intracerebral steal. If this holds true, the decrease in blood flow may be proportional to the global hyperemia in the brain. To establish appropriate hemodynamic control during revascularization surgery, the authors monitored the jugular bulb oxygen saturation (SjO2) intraoperatively, a method that could sensitively detect global hyperemia.

METHODS

A total of 17 patients, most of whom presented with transient ischemic attacks or fluctuating neurological deficits, underwent intraoperative monitoring of their SjO2 and end-tidal carbon dioxide (ETCO2) after a state of anesthesia had been induced with isoflurane (Group 1) or propofol (Group 2). In eight of these patients, the regional cerebral blood flow (rCBF) of the collateral vessel territory was also monitored by laser Doppler flowmetry during the period of cortical exposure, and a total of 113 data sets (averaged values during 2.5-minute intervals) was collected. There was fluctuation in the ETCO2 levels ranging from 36 to 44 mm Hg. The mean SjO2 level was clearly greater (p < 0.01) in Group 1 (71.8 +/- 2.2%) than in Group 2 (63.3 +/- 2.1%). An episodic fall in rCBF was observed in association with a transient increase in SjO2. Such an event was not uncommon in Group 1 and there was a greater risk of rCBF decreasing when SjO2 exceeded a cutoff level of 76% (p < 0.01). This level could sometimes be reached at a broad range of ETCO2 readings (37-44 mm Hg). In Group 2, similar events sometimes occurred when SjO2 increased beyond 70%. However, this level could be reached only with a higher ETCO2 (42-44 mm Hg). The rCBF level was negatively correlated to SjO2 (p < 0.01), but not always to ETCO2, indicating that the episodic fall in rCBF was closely related to global hyperemia rather than the absolute level of hypercapnia.

CONCLUSIONS

The observed association between a fall in rCBF and global hyperemia supports the intracerebral steal hypothesis and indicates that it is prudent to avoid excessive global hyperemia. The optimal range of CO2 for isoflurane is more restricted than that for propofol, presumably because isoflurane induces hyperemia by itself. Monitoring of SjO2 appears to represent the most practical technique for detecting global hyperemia as well as global ischemia, both of which may cause ischemic complications in moyamoya disease.

Intraoperative monitoring of jugular bulb oxygen saturation in patients with moyamoya disease

The jugular bulb oxygen saturation (SjO2) and end-tidal carbon dioxide (ETCO2) were monitored continuously during surgery in six cases of Moyamoya disease who had demonstrated multiple episodes of transient ischemic attacks (TIAs) and/or fluctuating neurological deficits preoperatively. The arterial carbon dioxide tension (PaCO2) levels were also measured repeatedly at predetermined interval. In two cases (group H), the ETCO2 was controlled at hypercapnic levels during surgery (45.5 +/- 1.5 mmHg) and the remaining four (group N) were operated on in a normocapnic state (39.0 +/- 2.0 mmHg). The group H patients demonstrated high levels of SjO2 ranging from 72 to 85%, indicative of excessive hyperemia. One of the group H patients demonstrated mild and transient motor weakness postoperatively. The group N patients demonstrated normal levels of SjO2 ranging from 66 to 78%. All the patients in both groups demonstrated fluctuations in SjO2 levels in clear positive correlation with spontaneous changes in PaCO2 levels. The present findings indicated that: (1) Global carbon dioxide reactivity of cerebral perfusion is well preserved in patients with Moyamoya disease; and (2) hypercapnia in these patients often causes excessive hyperemia. The occurrence of postoperative neurological deficits in association with such an excessive hyperemia suggests that hyperapnia during surgery is not always beneficial. Intraoperative monitoring of SjO2 is useful for maintaining cerebral perfusion within the optimum range.

Brain tissue gases and pH during arteriovenous malformation resection

OBJECTIVE

The purpose of this study was to determine whether baseline partial pressure of oxygen (PO2), partial carbon dioxide pressure (PCO2), and pH in brain tissue adjacent to arteriovenous malformations (AVMs) are different from those in control patients. In addition, PO2, PCO2, and pH changes were measured during resection of the AVMs.

METHODS

Two groups were studied. Group 1 (n = 8) was composed of nonischemic patients scheduled for cerebral aneurysm clipping. Group 2 (n = 13) was composed of patients undergoing neurosurgery for resection of AVMs. After the craniotomy, the dura was retracted and a combined PO2, PCO2, and pH sensor was inserted into nonischemic brain tissue in Group 1. In Group 2, the sensor was inserted into tissue 2 to 3 cm from the margin of the AVMs, within the same arterial blood supply. After equilibration of the sensor, tissue gases and pH were measured during steady-state anesthetic conditions in Group 1 and during resection of AVMs in Group 2.

RESULTS

Under baseline conditions before the start of surgery, tissue PO2 was decreased in patients with AVMs compared with control patients, but PCO2 and pH were not changed. During resection of the AVMs, PO2 and pH increased and PCO2 decreased compared with baseline measurements. These parameters did not change in control patients during a similar time period.

CONCLUSION

The results suggest that cerebrovascular or metabolic adaptation occurs in patients with AVMs with decreased tissue perfusion pressure as an adjustment for decreased oxygen delivery. During resection of AVMs, this adaptation produces a relative hyperemic environment with tissue hyperoxia, hypocapnia, and alkalosis that is not corrected by the end of surgery.

Monitoring of cerebral hemodynamics with jugular bulb catheters

Jugular venous oxygen saturation (SjvO2) monitoring is useful for detecting episodes of cerebral hypoxia/ischemia in patients with head injury, patients undergoing neurosurgical procedures, and patients undergoing cardiopulmonary bypass. The use of SjvO2 monitoring can direct the treatment of ischemic episodes and identify the optimal level of cerebral perfusion pressure and PCO2 for the individual patient.

Brain tissue response to CO2 in patients with arteriovenous malformation

We tested whether cerebral arteriovenous malformations (AVM) alter brain tissue oxygen pressure, PO2, carbon dioxide pressure PCO2, and pH before, during, and after hypercapnia. A craniotomy was performed and a sensor inserted into normal brain tissue (control) (n = 7) or into tissue adjacent to an AVM (n = 9). Under baseline conditions, tissue PO2 was 80% lower in AVM compared to control patients, but PCO2 and pH were normal. During a 10 mm Hg increase in PaCO2, tissue PO2 increased only in AVM patients, PCO2 increased in both groups, and pH decreased only in controls. When hypercapnia was reversed, tissue PCO2 decreased below baseline and pH increased in AVM patients. Results suggest that tissue CO2 washout and elevated pH result from increases in blood flow during hypercapnia. This response may be related to symptoms of hyperperfusion during AVM resection.

Clinical cerebrovascular applications of arterial ultrasound volume flow rate estimates

A variety of disorders affect cerebral hemodynamics. Volume flow rate (VFR) estimates now allow accurate quantification of the effect of cerebrovascular lesions on the conduit vessels, with excellent in vivo and in vitro correlation. Four selected cases with VFR data and angiographic correlation are presented to illustrate potential clinical uses of this method. The VFR estimates were obtained with a color M-mode-based velocity imaging technique, which uses time-domain processing (P-700 Color Velocity Imaging System, Philips Ultrasound International, Irvine, CA). In a patient awaiting coronary artery surgery, with unilateral internal carotid artery occlusion and contralateral angiographic stenosis (50-80%, reader variation), the baseline and acetazolamide-challenged common carotid artery VFRs showed excellent conduit function ipsilateral to this stenosis. Thus, the angiographic stenosis did not have significant hemodynamic effects and endarterectomy was avoided. In a patient with an arteriovenous malformation fed by the left vertebral and left external carotid arteries, high in the left cervical region, VFR estimates of two to three times normal predicted the feeding vessels, influenced management, and proved helpful in follow-up. In a patient with subclavian steal syndrome, VFR estimates quantified the steal after brachial hyperemia. Finally, in a patient with delayed vasoconstriction after subarachnoid hemorrhage, very low VFR estimates preceded clinical deterioration. Quantification of hemodynamic changes with VFR estimates was useful for the diagnosis, management, and follow-up of these patients with four types of cerebrovascular disease, and should be applicable in many others.