New quantitative method for non-invasive monitoring of tissue blood oxygenation by near infrared spectrophotometry

The near infrared absorption spectra was measured with the transmitted light through rat brain under the various condition. The absorbance changes below 780 nm were attributable to hemoglobin (Hb) in the brain tissue, whereas those above 780 nm were associated with both Hb and cytochrome oxidase. To eliminate possible interference from cyt. oxidase, two wavelengths, 750 nm and 780 nm, were used to measure Hb oxygenation in the tissue. The absorbance changes in human blood cell suspensions were measured with changes in hematocrit values in the optical cuvette. At two wavelengths 750 nm and 780 nm, there was a linear relationship between absorbance changes and hematocrit values. Through these in vitro studies, the following equation (1) and (2) were obtained to monitor quantitatively the changes of oxy-Hb content (delta Hb O2) and total-Hb content (delta Hb Vol.) in the living tissue. These are (1) delta Hb O2 = -1.15 delta A 750 + 1.39 delta A 780, (2) delta Hb Vol. = -0.29 delta A 750 + 0.59 delta A 780. The studies using these equations showed that the oxy-Hb content in the brain was decreased as the O2 concentration in inspired gas was lowered with a half of Hb deoxygenated at 7% O2. The reliability of these equations was examined under the various conditions in situ such as CO2 inhalation, intravenous injection of Ca2+-blocker nicardipine, hemorrhage and retransfusion. These results confirmed that these equations derived from in vitro studies, were successfully applied to the in situ measurements of the oxygenation state of Hb in the living tissues.     

Good correlation between cerebral oxygenation measured using near infrared spectroscopy and stump pressure during carotid clamping.

AIM: Intraoperative hypoperfusion ischemia is one factor that leads to perioperative stroke during carotid endarterectomy. Selective shunting is one way to reduce intraoperative hypoperfusion, but to shunt selectively needs a sensitive and simple monitoring system together with the rules for insertion. Near infrared spectroscopy (NIRS) is a monitoring system that can be used throughout the operation, and reflects the cerebral oxygenation instantly, but its value in insertion of shunt tubes is still controversial. The aim of this study was to determine criteria that can be used to insert shunt tubes. METHODS: Forty-three consecutive patients with severe carotid stenosis undergoing carotid artery surgery with NIRS monitoring were enrolled in the study. Under general anesthesia, the optodes of NIRS were placed bilaterally on the forehead. Throughout the operation, regional saturation of the frontal lobe (SdO2) was monitored every 5 s. RESULTS: All operations were performed without any perioperative deaths. NIRS showed that SdO2 fell rapidly as soon as the artery was cross-clamped, and reached the lowest level after 60 s. SdO2 change at 60 s and the stump pressure showed good correlation (r=0.65), and stump pressure of 40 mmHg was almost equivalent to 5% SdO2 decrease in NIRS. CONCLUSION: NIRS monitoring is suitable for monitoring during carotid endarterectomy for selective shunting, because it can be used throughout the operation and shows the immediate change in oxygenation. There is a possibility that a decrease of 5% can be used as a decisive value for shunt insertion.     

Rewarming and cardiac surgery: a review

Patients undergoing cardiac surgery are mildly hypothermic by the completion of the surgical procedure. They need to return to a normothermic state if enzymatic functions are to proceed in their normal manner. The body can produce heat by elevating metabolic rate or by activating the shivering mechanism. Metabolic rate peaks shortly after separation of the patient from cardiopulmonary bypass, and therefore contributes to heat production. Because of the effects of neuromuscular blockage administered both during and after surgery; these patients may be unable to generate heat by shivering, and shivering is usually undesirable. This eliminates the major heat production mechanism available to the body. Therefore, heat must be transferred down its gradient by means of convection and conduction. External and internal methods accomplish these goals. External methods, which minimize additional heat loss, include the use of warming lights, elevation of room temperature, and the use of blankets. Internal methods, which transfer heat by convection, may be used to help actively reverse hypothermia. Such techniques include warmed inhalation gases and intravenous fluids, warmed nasogastric lavage fluid, and warmed peritoneal dialysis fluid for patients with end-stage renal failure with severe electrolyte disorders after surgery.     

Pulmonary protection during cardiac surgery: systematic literature review

Ischemia-reperfusion injury occurs during heart surgery in which cardiopulmonary bypass is used. Current knowledge of the factors contributing to postoperative pulmonary dysfunction and the measures to avoid it are reviewed.     

Corticosteroids and cardiopulmonary bypass : a review of clinical investigations

Traditionally, corticosteroids have been administered to patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) to ward off detrimental physiologic alterations associated with activation of the systemic inflammatory response, yet few well-controlled investigations exist, and use of these drugs in this setting remains controversial. This review article critically examines the results of clinical investigations in this area, and certain conclusions are suggested. The constellation of findings indicate that corticosteroids offer no clinical benefits to patients undergoing cardiac surgery with CPB and in fact may be detrimental. Further directions for clinical research in this area are also suggested.     

Extra corporeal membrane oxygenation after pediatric cardiac surgery: a 10 year experience

Indications for extra corporeal membrane oxygenation (ECMO) after pediatric cardiac surgery have been increasing despite the absence of encouraging survival statistics. Modification of ECMO circuit led to the development of integrated ECMO cardiopulmonary bypass (CPB) circuit at the author's institute, for children undergoing repair of transposition of great arteries among other congenital heart diseases (CHD). In this report, they analyzed the outcome of children with CHD, undergoing surgical repair and administered ECMO support in the last 10 years. The outcome was analyzed with reference to the timing of intervention, use of integrated ECMO-CPB circuit, indication for ECMO support, duration of ECMO run and the underlying CHD. The results reveal a significantly improved survival rate with the use of integrated ECMO-CPB circuit and early time of intervention rather than using ECMO as a last resort in the management. The patients with reactive pulmonary artery hypertension respond favorably to ECMO support. In all scenarios, early intervention is the key to survival.     

Management of massive air embolism during open-heart surgery with retrograde perfusion of the cerebral vessels and hyperbaric oxygenation

Retrograde perfusion through the superior vena cava was used in 2 patients who were injured by massive air embolism occurring during open-heart surgery. They underwent hyperbaric treatment immediately following completion of the intracardiac repair. Both patients made complete recovery and were discharged, with no defects attributable to the incident.     

The pulse oximeter: a non-invasive monitor of oxygenation during thoracic surgery

The pulse oximeter continuously and non-invasively measures arterial saturation. The objective of the current study was to assess the value of this monitor during thoracic surgery with one-lung ventilation. A total of 108 pulse oximeter saturation readings (SaO2[O]) were compared with PaO2 and calculated saturation (SaO2[C]) values. Hypoxia (PaO2 less than 70 mmHg) always resulted in a SaO2 (O) value below 95%. For the detection of hypoxia, the pulse oximeter had a sensitivity of 100%, a specificity of 91% and a predictability of 70%. The correlation between SaO2(C) and SaO2(O) was good (r = 0.895). In the samples with a PaO2 below 100 mmHg the correlation between SaO2(C) and SaO2(O) was significantly better when the temperature was at least 36 degrees C (r = 0.956 vs. r = 0.706; p less than 0.005) or when the cardiac index was greater than 2.5 l/min/m2 (r = 0.896 vs r = 0.417; p less than 0.01).     

Sirolimus-eluting stents: a review of experimental and clinical findings

Sirolimus (rapamycin), a macrolide antibiotic with known potent immunosuppressive properties, acts in the first phase (G1) of the cell cycle, blocking its further progression to the phase of DNA synthesis (S). In experimental models, rapamycin is effective in inhibiting smooth muscle cell proliferation and migration after vessel wall injury with balloon angioplasty. These results lead to the clinical application of sirolimus-eluting stents in 45 patients in Sao Paulo and Rotterdam (FIM Registry) and 238 patients in a randomized, European multicenter trial (RAVEL). These trials showed, by angiography and intravascular ultrasound, almost complete abolition of in-stent late hyperplasia up to one year after the procedure. In this review, we describe the experimental and clinical results of sirolimus-eluting stents including our experience of 26 stents implanted in 17 patients. In elective de novo lesions has shown remarkably clear lumens at follow-up angiography and intravascular ultrasound within the stented segments were observed with no lesion progression at the stent margins or thrombosis after a 2 month regimen of aspirin, and ticlopodine or clopidogrel. New large-scale ongoing clinical trials will investigate the efficacy of sirolimus-eluting stents in lesions that are traditionally associated with high restenosis rates after stent implantation, such as long lesions, bifurcations and instent restenosis.     

Current status of cardiac surgery: a 40 year review

Cardiac surgery has undergone dramatic advancements during the past 3 decades. The introduction of cardiopulmonary bypass and cardioplegic arrest ushered in the true era of open heart surgery. Bioprostheses and mechanical valves as well as techniques for valve reconstruction permit routine repair or replacement of stenotic and regurgitant native valves. Progress in the disciplines of mechanical and electrical engineering has led to the development of pocket watch-sized, physiologically responsive pacemakers as well as a variety of circulatory assist devices that include the intraaortic balloon pump, ventricular assist device and total artificial heart. The synthesis of cardiotonic and vasoactive drugs and advancements in anesthetic management, postoperative monitoring and nursing care greatly facilitate perioperative patient management. This summary of state of the art cardiac surgery begins with a brief historical background followed by a review of recent advances in six main categories: coronary artery disease, acquired valvular heart disease, congenital cardiac disease, cardiac transplantation, myocardial preservation and mechanical circulatory assistance. In conducting the review of recent literature, particular attention was directed to large clinical series that document the results of contemporary surgical procedures, novel therapeutic approaches to current clinical problems and unresolved controversies in the field of cardiac surgery. The abundance of surgical literature and constraints on the length of this article do not permit an exhaustive review. Apologies are extended to clinicians and laboratory investigators whose important contributions to the understanding and treatment of cardiac disease are not included herein.     

Liver tissue tolerance for irradiation: experimental and clinical investigations

Radiation treatment of the liver for malignant disease has gained renewed interest due to newly developed treatment modalities. Still limited specific knowledge is available concerning liver damage following irradiation. Inconsistencies between reported animal experimental studies are largely due to differences in irradiation techniques and to varying observation periods. Following the introduction of Megavoltage irradiation and the development of more sophisticated irradiation techniques, clinical reports concerning more reliable studies became available. The reaction of the liver to irradiation depends specifically on parameters as type of irradiation, dose, dose rate, fractionation schedule, and irradiated volume. Also the use of cytotoxic agents and liver surgery are of importance for the ultimate therapeutic result. Radiation hepatitis in humans may develop following high-dose liver irradiation resulting in clinical and histopathological disorders resembling a veno-occlusive disease-like syndrome. These disorders may either totally or partially recover or be progressive in time resulting in hepatic failure. It is concluded that depending on the variables mentioned, ionizing radiation up to 35 Gy to the human liver, given to a limited volume, can be applied without major liver function disturbances.     

尼莫地平控制性降压对颅内动脉瘤夹闭术中脑氧代谢的影响

目的观察颅内动脉瘤夹闭术中应用尼莫地平控制性降压对脑氧代谢的影响。方法选择颅内动脉瘤夹闭术患者30例,根据控制降压药随机分为2组:硝酸甘油组(A组,n=15)和尼莫地平组(B组,n=15),于不同时间段行动静脉血气分析和血乳酸含量测定。结果(1)A组的心率在降压中的两时间点明显快于降压前,差异有统计学意义(P<0.05),在降压30min和夹闭后两时间点上,B组的HR明显较A组慢,差异有统计学意义(P<0.05)。(2)B组的D(a-jv)O2和D(jv-a)BG在降压30min、夹闭后及停降压30min时3个时间点明显少于A组,差异有统计学意义(P<0.01);与降压前比较,B组的D(a-jv)O2和D(jv-a)BG在降压30min和夹闭后两时间点明显下降,差异有统计学意义(P<0.01)。结论尼莫地平可安全用于动脉瘤夹闭术中控制性降压,降低脑氧代谢和改善脑氧合,有较好的脑保护作用。     

电生理监测在颅内动脉瘤夹闭术中的应用及临床意义

目的研究开颅夹闭颅内动脉瘤手术对脑干听觉诱发电位（BAEP）、躯体感觉诱发电位（SEP）和脑电图3项电生理指标的影响及临床意义.方法在25例颅内动脉瘤患者的开颅夹闭术中,进行BAEP、SEP和脑电图实时监测,观察手术操作对神经电生理指标的影响.结果手术操作均不同程度引起BAEP、SEP及脑电图的变化.其中BAEP的Ⅰ、Ⅲ、Ⅴ波的潜伏期延长0.8～1.0ms,Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期延长0.3～0.5 ms,Ⅰ、Ⅴ波幅电位较术前降低50%左右;SEP的N20、P25潜伏期延长3～5 ms,波幅较术前降低50%.结论术中动态监测BAEP Ⅰ、Ⅲ、Ⅴ波的潜伏期、Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期及Ⅰ、Ⅴ波电位变化,SEP的N20、P25潜伏期、电位变化、脑电图波幅和频率电生理的敏感变化,对了解术中有无脑缺血,灵活调整断流时间及手术方式具有重要的指导意义.