Measurement of tissue perfusion by oxygen transport patterns in experimental shock and in high-risk surgical patients

Survivors of high-risk general (noncardiac) surgery were observed to have cardiac index (CI) values averaging 4.5 l/min·m², oxygen delivery (\(\dot D\)O₂) of >600 ml/min·m², and oxygen consumption (\(\dot V\)O₂) of 170 ml/min·m². In contrast, these values were relatively normal in patients who subsequently died. A very early predictive index based on these observations was found to predict outcome in 94% of high-risk patients. The hypotheses that increased-\(\dot D\)O₂ and\(\dot V\)O₂ in the survivors represent compensatory physiologic responses and that these values were appropriate therapeutic goals were tested in prospective randomized clinical trials and found to reduce mortality and morbidity significantly. The optimal goals were more easily attained with colloids, red cells, dobutamine, and vasodilators, according to their capacity to improve tissue perfusion, as reflected by increased flow and oxygen transport. The extremely complex interactions between-\(\dot D\)O₂ and\(\dot V\)O₂ are reviewed.     

Practical points in the application of oxygen transport principles

Application of the principles of oxygen transport in the management of critically ill patients can influence the frequency of organ failure and outcome. Adequate tissue oxygen consumption in these patients may depend on a supranormal level of oxygen delivery. The equations used for calculating oxygen delivery and consumption are provided, and it is noted that clinicians should have a clear understanding of the limitations of each of the measurements included in the equations. The methods used to perform the measurements are reviewed. Widespread acceptance and use of oxygen transport protocols in treatment is only possible if the measurements on which they are based are accurate and properly interpreted.     

Splanchnic oxygen transport after cardiac surgery: evidence for inadequate tissue perfusion after stabilization of hemodynamics

Objective To evaluate the adequacy of visceral oxygen transport and gastric pH_i after open heart surgery in patients with stable hemodynamics.Design Nonrandomized control trial.Setting A general intensive care unit in a tertiary care center.Patients Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics.Interventions The effect of dobutamine infusion (6 g kg^–1 min^–1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pH_i by gastric tonometer.Measurements and results Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2±0.6 vs 4.4±0.7l· min^–1·m^–2;P<0.05), splanchnic blood flow (0.68±0.28 vs 0.91±0.281· min^–1·m^–2;p<0.05) and femoral blood flow (0.25±0.08 vs 0.32±0.11l·min^–1·m^–2;p<0.05). Changes in splanchnic oxygen delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pH_i did not change (7.30±0.08 vs 7.31±0.06; NS), while in the control group, gastric pH_i tended to decrease (7.32±0.04 vs 7.28±0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141±11 vs 149±11 ml· min^–1·m^–2;P<0.05) but did not change in the control group.Conclusions We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.This study was supported in part by the senior researcher's grant no. 1945/3015/92 to Dr. Takala from the Academy of Finland     

PEEP对急性呼吸衰竭病人全身氧供给的影响

目的探讨呼气末正压（ＰＥＥＰ）通气对急性呼吸衰竭病人全身氧供给（ＤＯ２）的影响。方法选择２０例急性呼吸衰竭机械通气病人,放置Ｓｗａｎ－Ｇａｎｚ导管,依次调节ＰＥＥＰ为０、０４９ｋＰａ、０９８ｋＰａ、１４７ｋＰａ四种压力水平,分别测定气体交换功能及氧动力学指标。结果ＰＥＥＰ为０４８ｋＰａ时动脉血氧分压（ＰａＯ２）即开始明显升高（Ｐ＜０５）,心脏指数（ＣＩ）却出现降低（Ｐ＜００５）,随着ＰＥＥＰ增加,ＣＩ逐渐下降。ＤＯ２在ＰＥＥＰ为０９８ｋＰａ以下时变化不显著,在１４７ｋＰａ时出现显著下降（Ｐ＜００５）,而氧摄取率（ＥｘｔＯ２）则有所增加（Ｐ＜００５）。结论ＰＥＥＰ使用不能明显提高ＤＯ２,高水平的ＰＥＥＰ可以降低ＤＯ２,必须采取措施提高ＣＩ才能使ＤＯ２增加。     

特利加压素对脓毒性休克患者心肺损伤组织灌注及氧代谢指标的影响

目的分析特利加压素对脓毒性休克患者心肺损伤、组织灌注及氧代谢指标的影响.方法所选120例脓毒性休克患者均为华中科技大学协和江北医院2017年3月至2019年3月收治,通过数字随机方法将其分成对照组与试验组(每组各60例);入院后两组患者均根据《成人脓毒性休克的血流动力学监测和支持指南》开展集束化治疗和早期监测,对照组给予去甲肾上腺素静脉持续泵入,试验组则给予去甲肾上腺素与特利加压素静脉持续泵入;观察分析患者的心肺损伤、组织灌注及氧代谢指标变化情况.结果与入组前比较,两组患者入组后96 h的氧合指数(oxygen index,OI)水平明显提高(P<0.05),肌酸激酶同工酶(creatine kinase isoenzyme,CK-MB)、心肌肌钙蛋白I(cardiac troponin I,cTnI)、氨基末端B型利钠肽前体(N-terminal pro-brainnatriuretic peptide,NT-proBNP)水平则明显降低(P<0.05);而且入组后96 h试验组的CK-MB、cTnT、NT-proBNP水平明显低于对照组(t=2.524、4.719、9.031,P=0.013、0.001、0.001<0.05),OI水平明显高于对照组(t=5.666,P=0.000l).与入组前比较,两组入组后96 h的血乳酸(lactic acid,Lae)水平明显降低(P<0.05),中心静脉血氧饱和度(central venous oxygensaturation,ScvO2)、平均动脉压(average arterial pressure,MAP)、灌注指数(perfusion index,PI)水平明显提高(P<0.05);与对照组比较,试验组入组后96 h血Lac水平明显降低(P<0.05),而ScvO2、MAP及PI水平则明显上升(P<0.05).与对照组比较,试验组的机械通气时间、去甲肾上腺素使用时间、ICU住院时间均明显缩短(t=4.529、3.474、7.841,P=0.001、0.001、0.001),24h补液量明显减少(t=2.107,P=0.037).两组的临床病死率、不良反应发生率比较差异有统计学意义(P<0.05).结论选择特利加压素治疗脓毒性休克患者,能改善氧代谢障碍和组织低灌注,有效保护器官功能,明显缩短ICU住院时间和机械通气时间,值得临床推广.     

The influence of different levels of PEEP on peripheral tissue perfusion measured by subcutaneous and transcutaneous oxygen tension

Objective To compare subcutaneous (PscO₂) and transcutaneous (PtcO₂) oxygen tension measurements in relation to hemodynamic variables at different levels of PEEP, and to evaluate the usefulness of these measurements as monitors of peripheral tissue perfusion.Design Prospective trial.Setting Intensive care unit in a university hospital.Patients Seven patients with gastric cancer who where undergoing total gastrectomy.Interventions Silicone catheter was placed in the upper arm and transcutaneous oxygen monitor was placed on the upper part of the chest. A pulmonary artery catheter was placed in the right pulmonary artery.Measurements and results PscO₂ and PtcO₂ together with hemodynamic variables were measured at different levels of PEEP. Progressive increase of PEEP reduced cardiac index (CI) (p<0.05) with a concomitant decrease of PscO₂ (p<0.05) and oxygen delivery (DO₂) (p<0.05). Changes in PtcO₂ parallelled changes in arterial oxygen tension (PaO₂), but no correlation was found between PtcO₂, CI and DO₂.Conclusion PscO₂ is a sensitive indicator of subcutaneous tissue perfusion, which can be used to identify the PEEP level, with optimum peripheral perfusion. PscO₂ seems to be a more reliable indicafor of tissue perfusion than PtcO₂.This study was supported by Tore Nilsons Fund for Medical Research. Lundgrens Stiftelse, Medical Faculty, University of Lund and by the Swedish Medical Research Council Projecr no. B88-17x-00640-24B     

The effects of low-dose dopamine on splanchnic blood flow and oxygen uptake in patients with septic shock

Objective: To assess the effects of low-dose dopamine on splanchnic blood flow and splanchnic oxygen uptake in patients with septic shock. Design: Prospective, controlled trial. Setting: University hospital intensive care unit Patients: 11 patients with septic shock, diagnosed according the criteria of the 1992 American College of Chest Physicians/Society of Critical Care Medicine consensus conference, who required treatment with norepinephrine. Measurements and main results: Systemic and splanchnic hemodynamics and oxygen transport were measured before and during addition of low-dose dopamine (3 μg/kg per min). Low-dose dopamine had a marked effect on total body hemodynamics and oxygen transport. The fractional splanchnic flow at baseline ranged from 0.15 to 0.57. In 7 patients with a fractional splanchnic flow less than 0.30, low-dose dopamine increased splanchnic flow and splanchnic oxygen delivery and oxygen consumption. In 4 patients with a fractional splanchnic flow above 0.30, low-dose dopamine did not appear to change splanchnic blood flow. Conclusion: Low-dose dopamine has a potential beneficial effect on splanchnic blood flow and oxygen consumption in patients with septic shock, provided the fractional splanchnic flow is not already high before treatment. Received: 19 September 1995 Accepted: 21 September 1996     

Delivery dependent oxygen consumption in patients with septic shock: Daily variations,relationship with outcome and the sick-euthyroid syndrome

Delivery dependent oxygen consumption (DDOC) is observed in patients with sepsis and vital organ dysfunction, and has been related to outcome. Similarly the sick-euthyroid syndrome is associated with a high mortality. We examined the daily variations of DDOC and its relation to hormonal changes, particularly those of the thyroid. In 22 patients, 14 with septic shock and 8 post-operative controls, oxygen delivery was increased by increasing cardiac output with vasodilation by phentolamine, during a total of 207 days. DDOC varied markedly between consecutive days in individual patients with sepsis, in both survivors and non-survivors. DDOC was related to severity of illness, assessed by APACHE II score (r=0.50,p=0.017), and plasma levels of triiodothyronine (T₃),r=–0.49,p=0.011, and thyroxine (T₄),r=–0.53,p=0.012. No correlation was observed between DDOC and outcome, nor blood levels of lactate, epinephrine, norepinephrine, dopamine or cortisol. In conclusion, we observed a marked disturbance of systemic oxygen uptake autoregulation in patients with septic shock which varied during the clinical course and was related to the sick-euthyroid syndrome.With the technical assistance of J. Lopez     

Continuous monitoring of mixed venous oxygen saturation in septic shock

Fiberoptic pulmonary artery catheters provide a practical method for continuously measuring the amount of oxygen in mixed venous blood. To characterize the usefulness of mixed venous oxygen saturation in managing patients with sepsis, we performed serial hemodynamic measurements on 20 patients with documented septic shock. There was a highly significant positive correlation between increases or decreases of 5% or more in mixed venous oxygen saturation and corresponding changes in oxygen delivery (r = 0.95) and oxygen consumption (r = 0.96). Mixed venous oxygen saturation less than 65% was clinically unacceptable in patients with sepsis and was associated with a poor prognosis. In this study, measurement of mixed venous oxygen saturation was a valuable predictor of survival in patients with septic shock and provided a means of continuously monitoring the status of tissue oxygenation.     

Evaluation of oxygen uptake and delivery in critically ill patients: A statistical reappraisal

Objective The evaluation of oxygen consumption (VO₂) and oxygen delivery (DO₂) has gained increasing importance in the monitoring of critically ill patients. They can be obtained from either direct measurements or by indirect calculations based on the Fick principle. However the choice between these two approaches remains controversial. The aim of the study was to investigate whether these 2 methods provide similar results, and if not, to define the best one in terms of reproducibility. Design Oxygen delivery and oxygen consumption were prospectively analyzed in 171 consecutive critically ill patients. Metabolic data were obtained simultaneously. Setting The study was completed in the intensive care unit as part of the management of the patients studied. Patients A first “group” of 279 evaluations was carried out in 73 consecutive critically ill patients. The results were subsequently validated by 423 observations performed in the 98 following patients. Interventions Before and during each evaluation, the patients were kept in stable hemodynamic and metabolic conditions. All were mechanically ventilated. Measurements and results VO₂ was evaluated by calculation (Fick principle) and direct measurement using indirect calorimetry. Cardiac output was both measured by the thermodilution technique and calculated (Fick principle) and the data were used for the evaluation of the directly measured and indirectly calculated DO₂. For both VO₂ and DO₂ the agreement between direct and indirect evaluations was not satisfactory. Differences as great as 55 ml/min·m² and 267 ml/min·m² between simultaneously measured and calculated VO₂ and DO₂ respectively may be expected. Finally, the indirect calculated methods were less reproducible than the measured ones. These observations resulted mainly from the cumulative effects of the random errors in the metabolic data entering into the calculation of VO₂ and DO₂. Conclusions Our data suggested that the indirect calculation (Fick equation) and the direct measurement (indirect calorimetry, thermodilution) of both VO₂ and DO₂ did not provide similar results. Direct measurements are more reproducible methods and must be preferred.     

Influence of tissue perfusion on the outcome of surgical patients who need blood transfusion

Purpose

The aim this study was to evaluate the clinical outcome of patients needing intra-operative blood transfusion by tissue perfusion markers.

Methods

A prospective single center cohort study. Adult patients needing blood transfusion during the intra-operative period were recruited.

Results

This study included 61 patients. At the time of blood transfusion the hemoglobin level was 8.4±1.8 g/dL. Scv02 has been the best tissue perfusion marker to determine mortality, compared with hematemetric values and other tissue perfusion markers, with a cut-off point at ROC curve equal to 80% (AUC=0.75; sensitivity=80%; specificity=65.2%). Patients who received blood transfusion and had Scv02 ≤80% (N=29), in comparison to those with Scv02>80% (N=32), had lower mortality rates (12.5% vs. 47.1%; p=0.008) and lower incidence of postoperative complications (58.9% vs. 72.9%; p=0.06). Blood transfusion with a Scv02 ≤80% was also associated with reduced use of vasopressors (5.9% vs. 36.8%; p=0.009). Lower incidence of hypoperfusion (17.6% vs. 52.6%; p=0.009), and lower incidence of infection (23.5% vs. 52.6%; p=0.038) in the postoperative period.

Conclusions

In major surgeries, Scv02 appears to be an important variable to be taken into consideration to decide for or against blood transfusion, since blood transfusion with adequte perfusion, reflected by Scv02>80%, are associated with worse clinical outcomes.     

A cost analysis of a treatment policy of a deliberate perioperative increase in oxygen delivery in high risk surgical patients

Objective: To investigate the cost implications of a treatment policy of a deliberate perioperative increase of oxygen delivery in high risk surgical patients. Design: A cost-effectiveness analysis comparing ‘protocol’ high risk surgical patients in whom oxygen delivery was specifically targeted towards 600 ml/min/m² with ‘control’ patients. Interventions: In a randomised, controlled clinical trial we previously demonstrated a significant reduction in mortality (5.7% vs 22.2%, p=0.015) and morbidity (0.68±0.16 complications vs 1.35±0.20, p=0.008) in ‘protocol’ high risk surgical patients in whom oxygen delivery was specifically targeted towards 600 ml/min per m² compared with ‘control’ patients. This current study retrospectively analysed the medical care and National Health Service resource use of each patient in the trial. Departmental purchasing records and business managers were consulted to identify M28.9nthe unit cost of these resources, and thereby the cost of treating each patient was calculated. Results: The median cost of treating a protocol patient was lower than for a control patient (￡6,525 vs ￡7,784) and this reduction was due mainly to a decrease in the cost of treating postoperative complications (median ￡213 vs ￡668). The cost of obtaining a survivor was 31% lower in the protocol group. Conclusion: Perioperative increase of oxygen delivery in high risk surgical patients not only improves survival, but also provides an actual and relative cost saving. This may have important implications for the management of these patients and the funding of intensive care. Received: 29 February 1996 Accepted: 2 September 1996     

Increased lactate/pyruvate ratio with normal b-hydroxybutyrate/acetoacetate ratio and lack of oxygen supply dependency in a patient with fatal septic shock

We report a case of fatal septic shock, with hyperlactatemia and blood cultures positive for Streptococcus pneumoniae, in a 70-year-old patient. On two occasions (5 days, and 2 days before the patient‘s death), the relationship between oxygen delivery (D˙O₂) and consumption (V˙O₂) was examined in conjunction with two presumed markers of tissue oxygenation: the lactate/pyruvate ratio (L/P), and the β-hydroxybutyrate acetoacetate ratio (βOHB/AcAc). Increasing D˙O₂ by about 30% (“oxygen flux test”) failed to increase V˙O₂. The βOHB/AcAc ratio remained within normal limits, thus suggesting uncompromised tissue oxygenation at the hepatic level. The L/P ratio remained persistently above normal limits, thus suggesting actual organ or regional hypoxia. This case shows that during an overwhelming septic shock, the “oxygen flux test” can be negative, despite the presence of hyperlactatemia and of an increased L/P ratio suggestive of impaired tissue oxygenation. Received: 7 December 1995 Accepted: 2 September 1996     

冠状动脉旁路移植术后氧代谢监测的初步探讨

目的:探讨冠状动脉旁路移植(CABG)术后氧代谢的变化及临床意义.方法:回顾性分析45例CABG患者,监测术后1、4、12、24、48 h氧供(DO2)、氧耗(VO2)、氧摄取值(ERO2).结果:CABG术后1 h DO2最低,为362.7 mL/(min·m2),术后4、12 h分别为395.8 mL/(min·m2)、433.3 mL/(min·m2),低于术后24 h的467.3mL/(min·m2),术后24 h后基本稳定.术后12 h VO2最高,为144.3 mL/(min·m2).术后1 h ERO2最高,为35.1%,术后12 h ERO2为33.3%,略低于术后1 h时,术后24 h降低为31.4%.结论:CABG术后1～4 h时组织处于缺氧状态,应加强氧供.术后存在病理性氧供依赖现象,氧供临界值为362.7～395.8 mL/(min·m2).CABG术后早期机体处于相对缺氧状态,此时应采用综合措施保证供氧和降低氧耗.     

体外循环中空气法胃粘膜pH值与氧供 氧耗的变化

目的观察体外循环（CPB）中空气法胃粘膜pH值与氧供、氧耗的变化了解体外循环期间胃粘膜的血流灌注。方法选择择期行体外循环心脏手术30例，麻醉后置入TONO胃管通过空气法胃粘膜张力模块自动持续监测胃粘膜二氧化碳分压（PgCO2），在监护仪中输入麻醉诱导后30min、体外循环30min、60min、停体外循环后30min和60min时间点的动脉和混合静脉血气分析结果，计算获得各时点的胃粘膜pH值（pHi）、氧供（DO2）和氧耗（VO2）等数据。结果PgCO2在CPB期间明显低于术前（P〈0．01），停CPB后恢复到术前水平；pHi的变化体外环循期间显著升高（P〈0．01），停CPB后恢复术前水平；DO2和VO2变化：CPB期间明显低于术前（P〈0．01），停CPB后明显高于CPB期间（P〈0．01），停CPB 60min后明显高于术前（P〈0．01）。结论本研究中的病例在低温体外循环期间未存在胃肠粘膜血流灌注不足。     

动脉血和混合静脉血的氧监测在心脏术后中的应用

目的　研究 37例心脏术后病人的动脉血和混合静脉血的氧监测的临床意义。方法　 37例病人分别于术后入ICU时 (术后Ⅰ组 )、术后 6～ 18h(术后Ⅱ组 )及术后 8～ 2 4h(术后Ⅲ组 ) ,测定动脉血pH值、氧分压 (PaO2 )、氧饱和度 (SaO2 )和混合静脉血pHv值、氧分压 (PvO2 )、氧饱和度 (SvO2 )及计算出氧利用率 (O2 ER)。结果　心脏术后病人的氧耗明显增加 (P <0 0 1) ,SvO2 与O2 ER呈明显的负相关 ,术后Ⅰ组、术后Ⅱ组及术后Ⅲ组的r值分别为 - 0 9198、- 0 92 6 0及 - 0 916 6 (P值均 <0 0 0 1)。结论　SvO2 是衡量心脏术后病人组织氧供需平衡的良好指标。     

脓毒性休克时大鼠全身氧供给与氧消耗关系的变化

目的：观察脓毒性休克时全身氧供给（ＤＯ２）与氧消耗（ＶＯ２）关系的变化。方法：以改良的盲肠结扎穿孔（ＣＬＰ）方法制备大鼠脓毒性休克模型，观察大鼠休克过程中ＤＯ２、ＶＯ２、氧摄取率（ＥＲＯ２）等变化。结果：ＣＬＰ后５小时已出现平均动脉压明显下降（Ｐ＜０．０５）。在休克早期，ＤＯ２即进行性下降，ＥＲＯ２出现代偿性升高，ＶＯ２维持相对不变，呈非氧供依赖关系；当ＤＯ２降至３４．６０ｍｌ·ｋｇ－１／ｍｉｎ后，ＶＯ２随ＤＯ２线性降低（ｒ＝０．７３３，Ｐ＜０．０１），即呈病理性氧供依赖关系。结论：脓毒性休克时ＤＯ２与ＶＯ２间呈双相变化关系，病理性氧供依赖的出现与组织氧摄取和氧利用功能障碍有关。     

低血容量性休克大鼠全身氧动力学的变化研究

目的：研究低血容量性休克时全身氧动力学的变化特点。方法：按４ｍｌ／ｋｇ,每隔０．５分次从静脉放血,观察大鼠休克过程中全身氧供给（ＤＯ２）,氧消耗（ＶＯ２）和氧摄取率（ＥｘｔＯ２）的变化。结果：失血后１．５小时血红蛋白浓度开始显著降低,心率明显加快,失血２．０小时平均动脉压明显下降,此时ＤＯ２亦开始进行性下降,由于ＥｘｔＯ２出现代偿升高,ＶＯ２维持相对不变;     

Adrenaline in treatment of septic shock: Effects on haemodynamics and oxygen transport

The effects of adrenaline on haemodynamics and oxygen transport were studied in 13 patients with septic shock persisting after optimal fluid loading. adrenaline was administered by intravenous infusion at an increasing dose until no further benefit was seen. There were significant increases in mean arterial pressure, cardiac index, left ventricular stroke work index and oxygen delivery index. There was no significant change in oxygen consumption although the trend was towards an increase. There was a significant reduction in oxygen extraction ratio, but no change in shunt fraction. Adrenaline would appear to have beneficial haemodynamic effects in septic shock.