Intra-operative monitoring of brain tissue O2 (PtiO2) during aneurysm surgery

BACKGROUND: Regional cerebral blood flow may be compromised during aneurysm surgery. This may occur during vessel occlusion by temporary cliping or result from the malposition of an aneurysm clip. In this report we monitored intra-operatively the brain tissue oxygen concentration (PtiO2) to visualize regional ischaemic events. METHOD: During surgery of 10 intracranial aneurysms, monitoring of PtiO2 was performed using a polarographic microcatheter (Licox, GMS-Kiel-Germany), which was placed in the vascular territory of the artery harboring the aneurysm. FINDINGS: No complications were observed after implantation of Licox electrodes. In 6 patients PtiO2 decreased during transient clipping. In two patients PtiO2 decreased below 2 mmHg without morphological or clinical signs cerebral ischemia. In four patients, without incidence during surgery, only minor oscillations were observed. CONCLUSION: Intra-operative monitoring of PtiO2 is a complimentary procedure to monitor cerebral perfusion and detect episodes of ischaemia. Given the rapid detection of these events, therapeutic intervention may be initiated before irreversible neuronal damage occurs.     

近红外分光仪在婴幼儿体外循环脑功能监测中的应用

目的 在不同体外循环(CPB)模式下，探讨近红外分光仪(NIRS)在脑氧合功能监测方面的价值。方法 室间隔缺损(VSD))合并肺动脉高压(PH)行心内直视手术患者24例，用随机数字表法分为3组，中度低温体外循环(MHCPB)组(n=6)，深低温低流量体外循环(DHLF)组(n=6)和深低温停循环(DHCA)组(n=12)，应用：NIRS测定脑组织氧合血红蛋白(HbO2)、还原血红蛋白(HbD)、细胞色素aa3(CytOx)和氧合血红蛋白最低点持续时间(HbO2-NT)，CPB后2分钟、降温末、复温末和术后6小时分别抽颈静脉球血测定乳酸值(Lact)和特异性神经源性烯醇化酶(NSE)，术前、术后测定脑电图各1次，并对它们之间的关系进行相关分析。结果 MHCPB组和DHLF组NIRS测定的指标与生化指标和脑电图之间无显著相关关系；而DHCA组：HbO2、CytOx的最小值和HbO2-NT与复温末Lact和NSE值显著相关，HbO2-NT小于35分钟的患者均无脑功能损伤表现。结论 DHCA组NIRS测定指标中的HbO2、CytOx最小值和HhO2-NT与反映脑损伤的其它指标显著相关，HbO2-NT是预测停循环安全时限的有效指标。     

Monitoring of cerebral oxygenation status with near-infrared spectroscopy during inferior vena caval reconstruction under extracorporeal circulation

We report two cases of anesthetic management with monitoring by near-infrared spectroscopy in patients with renal cell carcinoma and with adrenal cortical carcinoma, who had tumor thrombus invading into the inferior vena cava. In inferior vena caval reconstruction, extracorporeal circulation such as veno-veno bypass or cardiopulmonary bypass is frequently required. The hemodynamic unstability under extracorporeal circulation may lead to severe cerebral damage, especially in elderly patients. We monitored cerebral oxygenation state during reconstruction of the vena cava by near-infrared spectroscopy. One patient underwent surgery with veno-veno bypass and another patient with partial cardiopulmonary bypass. Oxygenated hemoglobin decreased during extracorporeal circulation, especially during the use of partial cardiopulmonary bypass compared with veno-veno bypass. However, these decreased oxygenated hemoglobin was restored rapidly at the end of extracorporeal circulation. Both patients showed no post-operative neurological complication. We concluded that near-infrared spectroscopy, which is continuous and non-invasive monitoring of cerebral oxygenation status, is one of the useful monitors during extracorporeal circulation.     

Monitoring cerebral oxygenation in a pediatric patient undergoing surgery for vascular ring

Regional cerebral oxygenation can be monitored using near-infrared spectroscopy (NIRS). Inadequacy of collateral cerebral circulation and regional cerebral ischemia during cardiac and vascular surgery may be detected by the use of NIRS monitoring. We report a 2-year-old child who underwent surgical repair of vascular ring and subclavian reimplantation, where use of NIRS helped in early detection and timely intervention to prevent prolonged cerebral ischemia.     

Monitors of cerebral oxygenation

None of the monitors of cerebral oxygenation discussed above has proven to be effective enough to have become a standard of care in any given area of medical treatment. As described above, each has specific and well-defined shortcomings that prevent its widespread use. These shortcomings may not be so much a failure of technology as an acknowledgement of the complexity of our goal: a monitor that can divide the entire brain into small, focal, and discrete areas and accurately measure the oxygen tension in each one. Because we are asking for the functional equivalent of 30 or 40 simultaneous PbtO2 probes, it is small wonder that we are not yet satisfied. Of the three monitors discussed here, the greatest potential may lie with the transcranial cerebral oximetry. The cerebral oximeter has the biggest potential for improvement because it holds the most potential for technical advancement. Although, for instance, jugular venous bulb oximetric catheters may become somewhat more accurate, the biggest drawbacks in that monitor's usefulness lie in human anatomy and intracerebral blood mixing, not catheter accuracy. PbtO2 probes, also, have little room for improvement. Although every technology can be refined, the PbtO2 probes are already accurate. The fact that they are an invasive monitor, and a regional one at that, will relegate them to a limited number of cases. Cerebral oximeters hold more potential. Their greatest limitations lie in technical aspects that can be, and hopefully will be, improved upon in terms of computer technology as well as algorithm accuracy. The fact that cerebral oximeters can be used on any patient, at any time, on almost any case, makes it, potentially, truly an ideal monitor for anesthesiologists and intensivists alike. There is no certainty that any of these limitations will be surmounted, at least to the degree necessary to achieve desired accuracy. But there is much to anticipate.     

Extracorporeal membrane oxygenation (ECMO) as lung or heart assist

Extracorporeal membrane oxygenation (ECMO) may serve as extracorporeal lung assist (ECLA) in patients with acute respiratory failure (ARF) or as extracorporeal heart assist (ECHA) in patients with low output syndrome (LOS) after open heart surgery. From 1988 to 1992 seven patients underwent ECMO in our hospital; four suffered from ARF and three from LOS. Various bypass techniques were employed. Two ARF patients, aged 58 and 18 years, had veno-venous bypass; in the latter, ECMO was reinstituted as a veno-arterial bypass one week after weaning. In a three-year-old boy, the ECMO outflow tubing was primarily connected to the pulmonary artery, and shortly afterwards relocated to the common carotid artery. In a 31-year-old man with ARF, and three LOS patients, a 56-year-old woman, and two men aged 68 and 70 years, ECMO was veno-arterial with direct access to the ascending aorta. A heparin-coated system was used, and all but one patient, who was treated with warfarin, received a daily low dose of heparin, which was withdrawn after from one to nine days.
Six patients were weaned off ECMO after 4.5 to 21 days. Three ARF patients recovered completely; the child died. In one LOS patient, ECMO was withdrawn due to a poor general condition. Two others were weaned off ECMO and the intra-aortic balloon pump, and the inotropic support was significantly reduced, but both died of multiple system organ failure. Although no firm conclusions can be drawn from these few case reports, the heparin-coated system used as ECLA appears promising, whereas ECHA seems to imply a poor prognosis in patients who are not candidates for cardiac transplantation.     

Invasive monitoring of cerebral oxygenation

Despite medical and technological advances in neurosurgical intensive care, severe traumatic brain injury still carries a poor prognosis. Invasive monitoring of cerebral oxygenation has recently been proposed as a means for the detection and prevention of cerebral ischemia in comatose patients; however, it has not proven to influence the patient’s outcome after severe brain injury. Eight recent reports selected from the literature are reviewed, and the authors’ own clinical experience is presented in order to define the indications, usefulness, limitations, and potential complications of the available methodology for the invasive monitoring of cerebral interstitial oxygen saturation.     

Monitoring of cerebral oxygenation with near infrared spectroscopy and tissue oxygen partial pressure during cardiopulmonary resuscitation in pigs

BACKGROUND AND OBJECTIVE: The present study was designed to compare cerebral oxygenation measured with near infrared spectroscopy and local brain tissue oxygen partial pressure, respectively, in pigs during cardiopulmonary resuscitation. Since tissue overlying the brain may have an impact on near infrared spectroscopy readings, we tested whether optode placement on intact skin or on the skull yielded comparable results. METHODS: Twelve healthy pigs were anaesthetized and subjected to continuous haemodynamic, near infrared spectroscopy and brain tissue oxygen partial pressure monitoring. After 4 min of untreated ventricular fibrillation, cardiopulmonary resuscitation was started and arginine vasopressin was administered repeatedly three times. Near infrared spectroscopy values recorded were both the tissue oxygenation index and the tissue haemoglobin index as well as relative changes of chromophores (haemoglobin and cytochrome oxidase). Four animals served as control and were measured with both near infrared spectroscopy optodes mounted on the intact skin of the forehead, while in the remaining eight animals, one near infrared spectroscopy optode was implanted directly on the skull. RESULTS: Near infrared spectroscopy readings at the skin or at the skull differed consistently throughout the study period. After arginine vasopressin administration, near infrared spectroscopy values at the different locations showed a transient dissociation. In contrast to near infrared spectroscopy measured on intact skin, near infrared spectroscopy readings obtained from skull showed a significant correlation to brain tissue oxygen partial pressure values (r = 0.67, P < 0.001). CONCLUSION: Near infrared spectroscopy readings obtained from skin and skull differed largely after vasopressor administration. Near infrared spectroscopy optode placement therefore may have an important influence on the tissue region investigated.     

Focal cerebral oxygenation and neurological outcome with or without brain tissue oxygen-guided therapy in patients with traumatic brain injury

Background  

In patients with severe traumatic brain injury (TBI), the depth and duration of cerebral hypoxia are independent predictors of outcome. This study aimed to evaluate the efficacy of brain oxygen-guided therapy in improving cerebral oxygenation and neurological outcome in severe TBI patients.     

Comparison of different near-infrared spectroscopic cerebral oxygenation indices with central venous and jugular venous oxygenation saturation in children

BACKGROUND: We compared two different near-infrared spectrophotometers: cerebral tissue oxygenation index (TOI) measured by NIRO 200 and regional cerebral oxygenation index (rSO(2)) measured by INVOS 5100 with venous oxygen saturation in the jugular bulb (SjO(2)) and central SvO(2) from the superior caval vein (SVC) during elective cardiac catheterization in children. METHODS: A prospective observational clinical study in 31 children with congenital heart defects in a catheterization laboratory was undertaken. TOI was compared with SjO(2) in the left jugular bulb and with SvO(2). rSO(2) was compared with SjO(2) from the right jugular bulb and SvO(2). Linear regression analysis and Pearson's correlation coefficient were calculated and Bland-Altman analyses were performed. RESULTS: Cerebral TOI and SjO(2) were significantly correlated (r = 0.56, P < 0.0001), as well as TOI and SvO(2) with r = 0.74 (P < 0.0001). Bland-Altman plots showed a mean bias of -4.3% with limits of agreement of 15.7% and -24.3% for TOI and SjO(2) and a mean bias of -4.9% with limits of agreement of 10.3% and -20.1% for TOI and SvO(2). Cerebral rSO(2) and SjO(2) showed a significant correlation (r = 0.83, P < 0.0001) and rSO(2) and SvO(2) showed excellent correlation with r = 0.93 (P < 0.0001). Bland-Altman plots showed a mean bias of -5.2% with limits of agreement of between 8.4% and -18.8% for rSO(2) and SjO(2) and a mean bias of 5.6% with limits of agreement of 13.4% and -2.2% for rSO(2) and SvO(2). CONCLUSIONS: Both near-infrared spectroscopy devices demonstrate a significant correlation with SjO(2) and SvO(2) values; nevertheless both devices demonstrate a substantial bias of the measurements to both SjO(2) and SvO(2).