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Evaluation of extracranial-intracranial arterial bypass function by using near-infrared spectroscopy
Yoshihiro Murata1, Yoichi Katayama, Kaoru Sakatani
1Department of Neurological Surgery, Nihon University School of Medicine, Tokyo, Japan. ymcooper@med.nihon-u.ac.jp
Insights
Extracranial-intracranial (EC-IC) arterial bypass surgery can maintain cerebral blood oxygenation (CBO) in stroke patients, particularly when preoperative regional cerebral blood flow (rCBF) is low. Bypass function is critical for CBO maintenance within one year post-surgery for select patients.
Area of Science:
- Neurosurgery
- Neurology
- Vascular Surgery
Background:
- Extracranial-intracranial (EC-IC) arterial bypass surgery is used to prevent stroke in patients with hemodynamic compromise.
- The role of EC-IC bypass in maintaining cerebral blood oxygenation (CBO) and its temporal changes post-surgery requires further investigation.
Purpose of the Study:
- To evaluate the functional contribution of EC-IC bypass to maintaining CBO using near-infrared spectroscopy (NIRS).
- To assess the temporal changes in CBO following EC-IC bypass surgery.
Main Methods:
- Thirty patients undergoing EC-IC bypass surgery were studied.
- Cerebral blood oxygenation (CBO) was monitored using NIRS, assessing changes during superficial temporal artery (STA) compression.
- Preoperative regional cerebral blood flow (rCBF) was measured using single-photon emission computerized tomography (SPECT).
Main Results:
- EC-IC bypass maintained CBO immediately post-surgery in 36.7% of patients and within one year in 43.3%.
- Twenty percent of patients did not maintain CBO throughout the follow-up period.
- Preoperative rCBF below 24.5-25 ml/100 g/min predicted successful CBO maintenance by the bypass.
Conclusions:
- EC-IC bypass surgery can maintain CBO post-surgery in patients with low preoperative rCBF (< 24.5-25 ml/100 g/min).
- Bypass flow is crucial for adequate CBO when preoperative rCBF is below 22.2-24 ml/100 g/min.
Object:
It has been reported that extracranial-intracranial (EC-IC) arterial bypass surgery can be useful in preventing stroke in patients with hemodynamic compromise. Little is yet known, however, regarding the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO) and its temporal changes following surgery. The authors evaluated bypass function repeatedly by using near-infrared spectroscopy (NIRS) after surgery.
Methods:
The authors investigated 30 patients who had undergone EC-IC bypass surgery. Single-photon emission computerized tomography revealed a decrease in regional cerebral blood flow (rCBF) and a lowered rCBF response to acetazolamide. Changes in CBO were evaluated in the sensorimotor cortex during compression of the anastomosed superficial temporal artery (STA). When decreases in oxyhemoglobin (HbO2) and total hemoglobin (Hb) concentrations were observed, the bypass was considered to have maintained CBO in the sensorimotor cortex given that decreases in HbO2 and total Hb indicate cerebral ischemic changes. The bypass maintained CBO immediately after surgery in 36.7% of patients (Group I, 11 patients) and at some time after surgery, mostly within 1 year, in 43.3% of patients (Group II, 13 patients); however, it did not maintain it throughout the follow-up period in 20% of patients (Group III, six patients). Note that the preoperative rCBF in patients in Groups I and II was lower than that in patients in Group III (p < 0.004). In fact, the preoperative rCBF predicted whether a bypass would maintain CBO at a cutoff value of 24.5 to 25 ml/100 g/min. Among Groups I and II, 18 patients demonstrated an increase in deoxyhemoglobin during STA compression. The preoperative rCBF in these cases was lower than that in the six remaining patients (p < 0.006). Note that the preoperative rCBF predicted the postoperative deoxyhemoglobin response at a cutoff value of 22.2 to 24 ml/100 g/min.
Conclusions:
The EC-IC bypass surgery can maintain CBO immediately after surgery or gradually within 1 year when the preoperative rCBF is below 24.5 to 25 ml/100 g/min. Furthermore, bypass flow plays a critical role in maintaining an adequate CBO when preoperative rCBF is below 22.2 to 24 ml/100 g/min.