Intraoperative cerebral hemodynamic monitoring during carotid endarterectomy via diffuse correlation spectroscopy and near-infrared spectroscopy

Objective: This pilot study aims to show the feasibility of noninvasive and real-time cerebral hemodynamic monitoring during carotid endarterectomy (CEA) via diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS). Methods: Cerebral blood flow index (CBFi) was measured unilaterally in seven patients and bilaterally in seventeen patients via DCS. In fourteen patients, hemoglobin oxygenation changes were measured bilaterally and simultaneously via NIRS. Cerebral autoregulation (CAR) and cerebrovascular resistance (CVR) were estimated using CBFi and arterial blood pressure data. Further, compensatory responses to the ipsilateral hemisphere were investigated at different contralateral stenosis levels. Results: Clamping of carotid arteries caused a sharp increase of CVR (~70%) and a marked decrease of ipsilateral CBFi (57%). From the initial drop, we observed partial recovery in CBFi, an increase of blood volume, and a reduction in CVR in the ipsilateral hemisphere. There were no significant changes in compensatory responses between different contralateral stenosis levels as CAR was intact in both hemispheres throughout the CEA phase. A comparison between hemispheric CBFi showed lower ipsilateral levels during the CEA and post-CEA phases (p &lt; 0.001, 0.03). Conclusion: DCS alone or combined with NIRS is a useful monitoring technique for real-time assessment of cerebral hemodynamic changes and allows individualized strategies to improve cerebral perfusion during CEA by identifying different hemodynamic metrics.</p

What is new in microcirculation and tissue oxygenation monitoring?

Ensuring and maintaining adequate tissue oxygenation at the microcirculatory level might be considered the holy grail of optimal hemodynamic patient management. However, in clinical practice we usually focus on macro-hemodynamic variables such as blood pressure, heart rate, and sometimes cardiac output. Other macro-hemodynamic variables like pulse pressure or stroke volume variation are additionally used as markers of fluid responsiveness. In recent years, an increasing number of technological devices assessing tissue oxygenation or microcirculatory blood flow have been developed and validated, and some of them have already been incorporated into clinical practice. In this review, we will summarize recent research findings on this topic as published in the last 2 years in the Journal of Clinical Monitoring and Computing (JCMC). While some techniques are already currently used as routine monitoring (e.g. cerebral oxygenation using near-infrared spectroscopy (NIRS)), others still have to find their way into clinical practice. Therefore, further research is needed, particularly regarding outcome measures and cost-effectiveness, since introducing new technology is always expensive and should be balanced by downstream savings. The JCMC is glad to provide a platform for such research

Is Near-Infrared Spectroscopy a Reliable Method to Evaluate Clamping Ischemia during Carotid Surgery?

Guidelines do not include cerebral oximetry among monitoring for carotid endarterectomy (CEA). The purpose of this study was to evaluate the reliability of near-infrared spectroscopy (NIRS) in the detection of clamping ischemia and in the prevention of clamping-related neurologic deficits using, as a cutoff for shunting, a 20% regional cerebral oxygen saturation (rSO2) decrease if persistent more than 4 minutes, otherwise a 25% rSO2 decrease. Bilateral rSO2 was monitored continuously in patients undergoing CEA under general anesthesia (GA). Data was recorded after clamping, declamping, during shunting and lowest values achieved. Preoperative neurologic, CT-scan, and vascular lesions were recorded. We reviewed 473 cases: 305 males (64.5%) mean age 73.3 ± 7.3. Three patients presented transient ischemic deficits at awakening, no perioperative stroke or death; 41 (8.7%) required shunting: 30 based on the initial rSO2 value and 11 due to a decrease during surgery. Using the ROC curve analysis we found, for a >25% reduction from baseline value, a sensitivity of 100% and a specificity of 90.6%. Reliability, PPV, and NPV were 95.38%, 9%, and 100%, respectively. In conclusion, this study indicates the potential reliability of NIRS monitoring during CEA under GA, using a cutoff of 25% or a cutoff of 20% for prolonged hypoperfusion

Anesthesia for carotid endarterectomy: where do we stand at present?

Carotid endarterectomy (CEA) is a surgical procedure performed to reduce the incidence of embolic and thrombotic stroke. Although only a preventive procedure, CEA carries the risk of perioperative complications. There is constant searching for an optimal anesthetic technique. There are pros and cons for both anesthetic techniques used: regional (RA) and general anesthesia (GA). A large number of studies have compared RA and GA techniques in CEA surgery patients. The primary outcome was the proportion of patients with stroke, myocardial infarction, or death. However, neither the GALA trial nor the pooled analysis was adequately powered to reliably detect an effect of type of anesthesia on mortality. It may therefore be appropriate to consider other additional parameters (stress response, incidence of postoperative delirium and cognitive impairment, functional recovery, total surgery time, intensive care unit requirement, hospital stay, hospital costs and patients satisfaction) when comparing the outcomes of the two techniques. Although, the debate continues as to whether regional anesthesia or general anesthesia is safer, the choice of anesthetic technique is a complex decision and surgical teams should be able to offer both RA and GA. The individual approach is the ideal choice and should be determined at the discretion of the surgeon, anesthetist and patient depending on the clinical situation and own preferences

Assessment of cerebral oxygen supply-demand balance by near-infrared spectroscopy during induction of anesthesia in patients undergoing coronary artery bypass graft surgery

Dept. of Medicine/석사[한글] 본 연구는 근적외선 뇌산소포화도 측정기(Near-infrared spectroscopy, NIRS)를 이용하여 뇌산소포화도를 지속적으로 측정함으로써 midazolam의 뇌산소 전달 및 소모 균형(cerebral oxygen supply-demand balance)에 대한 효과를 알아보고자 하였다. 근적외선 뇌산소포화도 측정기는 비침습적으로 뇌산소포화도를 지속적으로 측정하는 장치로 뇌산소 전달 및 소모 균형의 작은 변화도 잘 반영하는 것으로 알려져 있다.2006년 8월부터 2007년 3월까지 체외순환없는 관상 동맥 우회로술(off-pump coronary artery bypass graft surgery, OPCAB)을 시행하는 60명의 환자를 대상으로 하고 무작위로 마취유도시 midazolam을 투여 받는 군(n = 30명)과 propofol을 투여 받는 군(n = 30명)으로 나누어 연구를 진행하였다. 뇌산소포화도는 기준값으로 대기 중에서 호흡하는 동안 측정하고 (T1), 100% 산소 마스크를 통해 탈질소화를 시행한 후(T2), midazolam 또는 propofol을 정주한 후(T3), sufentanil을 정주한 후(T4), 그리고 기관내삽관을 시행한 5분 후(T5) 각각 기록하였다. 각 시점에서 두 군의 뇌산소포화도의 값은 차이를 보이지 않았다. 각 군에서 100% 산소로 탈질소화 후(T2) 뇌산소포화도값이 기준값(T1)에 비해 의미있게 증가한 후 midazolam 또는 propofol 그리고 sufentanil을 투여 후에 추가적인 증가는 없었다. 기관삽관 후 5분 후의 값은 각 군에서 기준값을 포함한 어느 시점에 값과 비교하여도 통계학적인 의미를 가지지 않았다.본 연구를 통해서 midazolam이 propofol과 비슷한 정도로 뇌산소 전달 및 소모 균형을 유지하는 데 효과가 있음을 마취 유도하는 동안 뇌산소포화도 측정을 통해 확인할 수 있었다. 뇌산소포화도 측정기는 뇌산소 전달 및 소모 균형의 변화를 평가하는 간단한 장치로 앞으로 뇌산소포화도에 영향을 미치는 인자에 대한 연구가 더 필요할 것으로 생각된다. [영문] We evaluated the effect of midazolam on cerebral oxygen supply-demand balance by continuous monitoring of regional cerebral oxygen saturation (rSO2) through near-infrared spectroscopy (NIRS). Near-infrared spectroscopy continuously measures regional cerebral oxygen saturation noninvasively and has been shown to detect even small changes in cerebral oxygen supply-demand balance.60 patients scheduled for isolated off-pump coronary artery bypass graft surgery (OPCAB) between August 2006 and March 2007 were studied. Patients were randomly allocated into either midazolam (n = 30) or propofol (n = 30) group. Regional cerebral oxygen saturation was recorded before induction while patients were breathing room air as baseline (T1), after pre-oxygenation with 100% oxygen (T2), after administration of either midazolam or propofol (T3), after completion of administration of sufentanil (T4) and after tracheal intubation (T5). The rSO2 scores were similar between the groups throughout the study period. After pre-oxygenation at T2, rSO2 scores were significantly increased compared to baseline scores at T1 in each group, and did not show any additional increase after administration of either midazolam or propofol and sufentanil in both groups. The rSO2 scores at T5, 5 min after tracheal intubation showed no statistical significance compared to values of all other time points including baseline value in both groups.We demonstrated midazolam preserves cerebral oxygen supply-demand balance to a similar degree to propofol which could be assessed by NIRS during induction of anaesthesia. NIRS is a simple monitoring device able to detect changes in cerebral oxygen supply-demand balance and further studies regarding identification of factors closely correlating with changes in rSO2 scores are warranted.ope