High myocardial lactate concentration is associated with poor myocardial function prior to cardiopulmonary bypass

AIM: This study was designed to analyse the relationship between myocardial lactate--determined by microdialysis--and hemodynamics during coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). METHODS: Twenty consecutive patients with coronary artery disease were enrolled for this prospective, observational study. Microdialysis measurements were performed in the apical region of the heart during periods of 15 to 20 min before, during, and after CPB; hemodynamics and plasma lactate concentrations were determined correspondingly. Correlation analysis revealed a relationship between myocardial lactate concentration and right ventricular ejection fraction at baseline (Spearman's r: 0.6; P=0.02). Patients were thus grouped according to the myocardial lactate concentration at baseline into a high-lactate group (2.5+/-0.7 mmol.l(-1), n=10) and low-lactate group (0.9+/-0.5 mmol.l(-1), n=10). RESULTS: Preoperative left ventricular ejection fraction was not different between the groups (high-lactate group: 53+/-16%; low-lactate group: 57+/-15%; P=n.s.) Patients in the high-lactate-group had a lower stroke volume index (P=0.005) and right ventricular ejection fraction (P=0.04) before, and higher central venous and pulmonary artery pressures (P<0.01) after CPB. Plasma lactate was significantly higher during CPB in the high-lactate-group (P<0.05). No correlation was observed between myocardial and plasma lactate. Six patients in the high-lactate but none in the low-lactate-group needed inotropic support after weaning from CPB (P=0.01). CONCLUSIONS: These data are suggestive of an association between subtle myocardial ischemia--detected by microdialysis--and perioperative myocardial dysfunction in patients undergoing CABG. The microdialysis technique may be a valuable adjunct for monitoring myocardial metabolism during cardiac surgery.     

Neurochemical monitoring using intracerebral microdialysis during systemic haemorrhage

Summary Background. Intracerebral microdialysis is a sensitive tool to analyse tissue biochemistry, but the value of this technique to monitor cerebral metabolism during systemic haemorrhage is unknown. The present study was designed to assess changes of intracerebral microdialysis parameters both during systemic haemorrhage and after initiation of therapy. Methods. Following approval of the Animal Investigational Committee, 18 healthy pigs underwent a penetrating liver trauma. Following haemodynamic decompensation, all animals received a hypertonic-hyperoncotic solution and either norepinephrine or arginine vasopressin, and bleeding was subsequently controlled. Extracellular cerebral concentrations of glucose (Glu), lactate (La), glycerol (Gly), and the lactate/pyruvate ratio (La/Py ratio) were assessed by microdialysis. Cerebral venous protein S-100B was determined. Haemodynamic data, blood gases, S-100B, and microdialysis variables were determined at baseline, at haemodynamic decompensation, and repeated after drug administration. Results. Microdialysis measurements showed an increase of La, Gly, and La/Py ratio at BL Th compared to BL (mean ± SEM; La 2.4 ± 0.2 vs. 1.4 ± 0.2 mmol · l⁻¹, p < 0.01; Gly 37 ± 7 vs. 27 ± 6 μmol · l⁻¹, n.s.; La/Py ratio 50 ± 8 vs. 30 ± 4, p < 0.01), followed by a further increase during the therapy phase (La 3.4 ± 0.3 mmol · l⁻¹; Gly 69 ± 10 μmol · l⁻¹; La/Py ratio 58 ± 8; p < 0.001, respectively). Cerebral venous protein S-100B increased at decompensation and after therapy, but decreased close to baseline values after 90 min of therapy. Conclusions. In this model of systemic haemorrhage, changes of cerebral energy metabolism detected by intracerebral microdialysis indicated anaerobic glycolysis and degradation of cellular membranes throughout the study period.     

Mesenteric complications after hypothermic cardiopulmonary bypass with cardiac arrest: underlying mechanisms

The aim of this study was to determine the pathophysiological mechanisms of postcardiopulmonary bypass (CPB) intestinal dysfunction using an in vivo canine model of extracorporeal circulation. Six dogs underwent a 90 min hypothermic CPB with continuous monitoring of mean arterial blood pressure (MAP) and mesenteric blood flow (MBF). Reactive hyperemia and vasodilator responses of the superior mesenteric artery to acetylcholine and sodium nitroprusside were determined before and after CPB. Mesenteric lactate production, glucose consumption, creatine kinase (CK) release and venous free radicals were determined. CPB induced a significant fall (p < 0.05) in MAP and MBF. After CPB, reactive hyperemia (-26 +/- 15% versus -53 +/- 2%, p < 0.05) and the response to acetylcholine (-42 +/- 9 versus -55 +/- 6%, p < 0.05) were significantly decreased. Reperfusion increased lactate production (0.8 +/- 0.09 mmol/L versus 0.4 +/- 0.18, p < 0.05) and the CK release (446 +/- 98 U/L versus 5 +/- 19 U/L, p < 0.01). Endothelial dysfunction, conversion from aerobic to anaerobic metabolism, and intestinal cell necrosis seem to be responsible for intestinal complications associated with CPB.     

Myocardial metabolic monitoring with the microdialysis technique during and after open heart surgery

BACKGROUND: Post-operative ischemia after coronary artery bypass grafting (CABG) is well described but effective intervention requires immediate diagnosis. One possible way of increasing efficacy of peri-operative myocardial monitoring is using the microdialysis technique. METHODS: In 30 patients undergoing routine CABG, a microdialysis catheter was inserted in the left heart in an area of abnormal ventricular contraction. A second catheter was placed in normal tissue of the right ventricle. Microdialysis measurements were performed at time intervals before, during and 24 h after cardiopulmonary bypass (CPB) and retrospectively compared with standard clinical monitoring and clinical course. RESULTS: During CPB, both ventricles showed signs of poor tissue oxygenation. Glycerol was significantly higher in the left myocardium (146 +/- 67 vs. 72 +/- 36 micromol/l) and the glucose/lactate ratio (GLR), as a marker of nutritional disorder of the right ventricle (41 +/- 15% vs. 67 +/- 17%, P < 0.05), had significantly better values at this time point. Myocardial lactate concentrations were significantly higher in the dyskinetic segments (2.82 +/- 0.81 vs. 1.5 +/- 0.81 microM). During this period, no abnormal clinical standard monitoring results were observed. Post-operative significantly increased lactate/pyruvate ratios of three patients were clinically associated with peri-operative myocardial infarction (108 +/- 67 vs. 38 +/- 9, P < 0.05). The lactate/pyruvate ratio started rising before any other standard monitoring tools showed abnormal values. CONCLUSIONS: Peri-operative microdialytic measurements of parameters related to ischemia can be safely performed in a clinical setting, resulting in faster and more reliable detection of ongoing or new ischemia.     

Assessment of peripheral blood perfusion during open heart surgery with sublingual PCO2 measured by ISFET-PCO2 sensor

Sublingual tissue PCO2 (PSLCO2) was continuously monitored with an ISFET-based PCO2 sensor during and after the open-heart surgery under cardiopulmonary bypass (CPB) in order to study the effect of CPB on the peripheral blood perfusion. In addition, PSLCO2 monitoring was carried out in several cases of off-pump CABG. In the cases of open-heart surgery with CPB, PSLCO2 increased from 35.0 +/- 5.6 mmHg at the induction of anesthesia to the maximum value of 55.7 +/- 6.0 mmHg during CPB. After declamping of the aorta, PSLCO2 decreased gradually to 49.0 +/- 4.0 mm Hg 6 hr after the admission to ICU. The value of arterial lactate as another index of peripheral blood perfusion also increased gradually after the start of CPB, reaching to the maximum value of 8.8 +/- 1.1 mmol.l-1 just after being admitted into ICU. In the case of off-pump CABG, PSLCO2 and arterial lactate showed a slight increase during the later part of the surgery, but the change was not so significant as in the case of open-heart surgery under CPB. Through this study, typical changing pattern of PSLCO2 during the open-heart surgery was recognized. The change of PSLCO2 always preceded that of arterial lactate. We also experienced one case in which early stage of hypoperfusion was detected through the monitoring of PSLCO2. These results suggest clinical advantages of PSLCO2 monitoring.     

Splanchnic oxygen transport, hepatic function and gastrointestinal barrier after normothermic cardiopulmonary bypass

BACKGROUND: The effect of non-pulsatile, normothermic cardiopulmonary-bypass (CPB) on the splanchnic blood-flow and oxygen-transport, the hepatic function and the gastrointestinal barrier were observed in a prospective observational study in 31 adults undergoing cardiac valve replacement surgery. METHODS: The splanchnic (i.e. hepatic) blood-flow (HBF) was measured by the constant infusion of indocyanine-green (ICG) using a hepatic-venous catheter. Liver function was examined by calculation of lactate uptake, ICG extraction and the monoethylglycinexylidide (MEGX) test. A day before and after surgery the gastrioduodenal and intestinal permeability was measured by determination of sucrose and lactulose/mannitol excretion. RESULTS: Splanchnic blood flow and oxygen delivery did not decrease during and after surgery while splanchnic oxygen consumption (P < 0.0125) and arterial lactate concentrations increased. The splanchnic lactate uptake paralleled the lactate concentration. After but not during CPB an increase of systemic oxygen consumption was observed. The MEGX test values decreased on the first day after surgery. The ICG extraction was attenuated during the operation. The gastroduodenal and the intestinal permeability increased significantly postoperatively (P < 0.002, respectively, P < 0.001). There was no correlation between these findings and the duration of CPB. There was a significant correlation of the intestinal permeability but not of the gastroduodenal permeability between the prior and after surgery values (P < 0.001). CONCLUSION: Increased oxygen consumption during CPB may indicate an inflammatory reaction due to the pump beginning in the splanchnic area or a redistribution of the splanchinc blood flow during the CPB. Normothermic CPB does not lead to a significant or prolonged reduction of liver function. Normothermic CPB causes an increase of gastrointestinal permeability. The intestinal barrier function prior to surgery was accountable for the degree of loss of intestinal barrier function following surgery.     

Clinical experience in continuous graft monitoring with microdialysis early after liver transplantation

BACKGROUND: Early detection of impaired graft function after transplantation is essential. Microdialysis permits continuous monitoring of metabolic changes by mimicking the passive function of a capillary blood vessel by perfusion of a tubular semipermeable membrane introduced into the tissue. Based on the results of animal experiments, a clinical pilot study was undertaken. METHODS: Ten consecutive patients undergoing whole-organ orthotopic liver transplantation were studied. Intrahepatic implantation of a microdialysis catheter was performed at the end of the operation. A reference catheter was placed in the subcutaneous tissue over the right pectoral area immediately after abdominal closure. Consecutive serial samples were collected at 1-h intervals for 3 days after the operation. Glucose, lactate, pyruvate and glycerol concentrations were measured. RESULTS: During the first 24 h, the glucose level was higher in the liver than in reference tissue. Initially, increased mean(s.e.m.) levels of lactate (7.0(1.9) mmol/l) were observed in the liver, with a rapid decrease (to 2.7(0.3) mmol/l) over 24 h. A decrease in, and later stabilization of, the lactate : pyruvate ratio in the liver, from 18.7(4.2) to 10.0(1.1), was observed within 24 h after transplantation. Liver glycerol levels decreased from 62.3(7.4) to 24.3(7.5) micro mol/l within the first 16 h after reperfusion and remained stable thereafter. CONCLUSION: Microdialysis allows continuous monitoring of tissue metabolism in the transplanted liver. The procedure is easy to perform and safe. The specific detection and monitoring of pathological changes in the liver graft (e.g. arterial and portal vein thrombosis, or early rejection) with microdialysis should be addressed in further studies.     

Perioperative changes in cerebral ischemic markers in the cerebrospinal fluid after preoperative nimodipine treatment

BACKGROUND: Elderly patients with previous organ damage are at risk for minor neurologic deficits after major surgery. Spinal catheter analgesia is used whenever possible in this group and enables regular cerebrospinal fluid (CSF) sampling. Nimodipine, a calcium blocker, may have neuroprotective effects. We examined whether preoperative treatment with nimodipine affects ischemic markers in the CSF during extracranial surgery. METHODS: We performed a prospective, randomized, placebo-controlled, double-blind study in patients (ASA III or IV, 65-85 years) that underwent elective implantation surgery of the hip joint with intrathecal catheter anesthesia. Starting 15 h before surgery, patients received either 30 microg x kg(-1) h(-1) of nimodipine (n = 20) or 0.9% saline solution (placebo, n = 23) as a central venous infusion. The concentrations of neuron-specific enolase, hypoxanthine, creatine-kinase, lactate and pH in the CSF were determined before and immediately after surgery as well as 6 and 24 h after surgery. RESULTS: Before surgery, the baseline CSF pH was normal in all patients. Immediately after surgery it fell significantly to 7.08 +/- 0.29 in the placebo group and non-significantly to 7.27 +/- 0.38 in the treatment group; all values were normalized at 6 and 24 h after surgery in both groups. In the placebo group, lactate levels rose significantly from 1.48 +/- 0.28 mmol l(-1) before surgery to 1.77 +/- 0.27 mmol l(-1) immediately after surgery, and to 2.03 +/- 0.32 mmol l(-1) 24 h after surgery. In the treatment group, lactate concentrations remained stable up to 6 h after surgery (1.55-1.62 mmol l-1), while an increase to 2.10 +/- 0.48 mmol l(-1) was observed 24 h after the operation. Neuron-specific enolase, hypo-xanthine and creatine-kinase showed no change in either group. CONCLUSION: In conclusion, preoperative nimodipine treatment reduced intraoperative CSF acidosis and delayed surgery-related increases in lactate concentration in the CSF by several hours in elderly, comorbid patients at risk for minor postoperative neurologic deficits.     

Cerebral microdialysis monitoring: determination of normal and ischemic cerebral metabolisms in patients with aneurysmal subarachnoid hemorrhage

OBJECT: The success of treatment for delayed cerebral ischemia is time dependent, and neuronal monitoring methods that can detect early subclinical levels of cerebral ischemia may improve overall treatment results. Cerebral microdialysis may represent such a method. The authors' goal was to characterize patterns of markers of energy metabolism (glucose, pyruvate, and lactate) and neuronal injury (glutamate and glycerol) in patients with subarachnoid hemorrhage (SAH), in whom ischemia was or was not suspected. METHODS: By using low-flow intracerebral microdialysis monitoring, central nervous system extracellular fluid concentrations of glucose, pyruvate, lactate, glutamate, and glycerol were determined in 46 patients suffering from poor-grade SAH. The results in two subgroups were analyzed: those patients with no clinical or radiological signs of cerebral ischemia (14 patients) and those who succumbed to brain death (five patients). Significantly lower levels of energy substrates and significantly higher levels of lactate and neuronal injury markers were observed in patients with severe and complete ischemia when compared with patients without symptoms of ischemia (glucose 0 compared with 2.12+/-0.15 mmol/L; pyruvate 0 compared with 151+/-11.5 micromol; lactate 6.57+/-1.07 compared with 3.06+/-0.32 mmol/L; glycerol 639+/-91 compared with 81.6+/-12.4 micromol; and glutamate 339+/-53.4 compared with 14+/-3.33 micromol). Immediately after catheter placement, glutamate concentrations declined over the first 4 to 6 hours to reach stable values. The remaining parameters exhibited stable values after 1 to 2 hours. CONCLUSIONS: The results confirm that intracerebral microdialysis monitoring of patients with SAH can be used to detect patterns of cerebral ischemia. The wide range from normal to severe ischemic values calls for additional studies to characterize further incomplete and possible subclinical levels of ischemia.     

Peripheral tissue metabolism during off-pump versus on-pump coronary artery bypass graft surgery: the microdialysis study

Objective: The aim of this study was to monitor and compare metabolic changes in the skeletal muscle during coronary artery bypass grafting surgery with and without cardiopulmonary bypass (CPB) by means of interstitial microdialysis. Glucose, lactate, pyruvate and glycerol were assessed as markers of basic metabolism and tissue perfusion. Methods: Twenty patients undergoing surgical myocardial revascularization were enrolled in this pilot study. Ten patients were operated on without CPB (group A, off-pump) and 10 patients using normothermic CPB (group B, on-pump). Interstitial microdialysis was performed by a CMA 60 (CMA/Microdialysis AB, Sweden) probe, inserted into the patient's left deltoid muscle. Microdialysis measurements were performed at 30 min intervals. Glucose, lactate, pyruvate and glycerol were measured in samples using a CMA 600 Analyser (CMA/Microdialysis AB, Sweden). Results in both groups were statistically processed and the groups were compared. Results: Both groups were similar with regards to preoperative characteristics. Dynamic changes of interstitial concentrations of the measured analytes were found in off-pump (group A) and on-pump (group B) patients during the operation. There were no significant differences in dialysate concentrations of glucose and lactate between the groups. Significant differences were detected in pyruvate concentrations, lactate–pyruvate ratio and glycerol concentrations between off-pump versus on-pump patients. Pyruvate concentrations were higher in the off-pump group (p < 0.05), the lactate–pyruvate ratios indicating the aerobic/anaerobic metabolism status were lower in the off-pump group (p < 0.01) and the values of the concentrations of glycerol were lower in the off-pump group (p < 0.01). Conclusion: Dynamic changes in the interstitial concentrations of the glucose, glycerol, pyruvate and lactate were found in both groups of patients (off-pump and on-pump). The presented preliminary results suggest that extracorporeal circulation during cardiac operations could compromise skeletal muscle energy metabolism.     

Paradoxical increase in arterial hydrogen ion concentration in patients with hepatorenal failure given lactate-based fluids

We have investigated lactate intolerance in nine patients with acute hepatorenal failure during 21 machine haemofiltration treatments using a lactate based replacement solution. In all cases hyperlactataemia occurred, the mean arterial lactate increased from 1 +/- 0.2 mmol/l (mean +/- SEM) prior to treatment to 3.2 +/- 0.3 mmol/l at 1 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 2 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 3 h (P less than 0.01) and 3.9 +/- 0.4 mmol/l (P less than 0.01) post-treatment. There were correlations between the maximum increase in blood lactate and both the change in arterial hydrogen ion concentration (r = 0.71, P = 0.001) and the mean arterial blood pressure prior to starting treatment (r = -0.57, P = 0.007). During eight of the treatments (38%), the arterial hydrogen ion concentration increased. This group showed increased lactate intolerance in association with a lesser pretreatment mean arterial pressure. The administration of exogenous lactate to patients with hepatorenal failure who are at, or near to, the threshold of their own endogenous lactate metabolism can result in an increase in hydrogen ion concentration rather than the expected decrease, and therefore lactate-based dialysate solutions are best avoided.     

Small-dose epoprostenol decreases systemic oxygen consumption and splanchnic oxygen extraction during normothermic cardiopulmonary bypass

Normothermic, nonpulsatile cardiopulmonary bypass (CPB) impairs systemic and splanchnic oxygen transport and increases gastrointestinal permeability. It is an important therapeutic goal to avoid splanchnic dysoxia during CPB. Small-dose prostacyclin therapy improves splanchnic oxygen transport and microcirculation in septic patients. In this study, we sought to determine if during cardiac surgery, the prostacyclin analog epoprostenol improves the balance of systemic and splanchnic oxygen transport. Eighteen patients undergoing cardiac valve replacement were randomized to receive either epoprostenol (3 ng x kg(-1) x min(-1)) or placebo during, and for 1 hour after, surgery. Systemic and splanchnic oxygen delivery, consumption, and extraction and arterial, mixed venous, and hepato-venous lactate concentrations were measured before, during, and after CPB. Gastrointestinal permeability was measured 1 day before and 1 day after surgery using the triple sugar permeability test. During CPB, the epoprostenol group had decreased systemic oxygen consumption and splanchnic oxygen extraction (P = 0.024). These effects were not present 1 hour after the end of epoprostenol infusion. The study was not adequately powered to determine whether epoprostenol altered the trend towards increased lactate metabolism and increased postoperative gastrointestinal permeability, nor could we demonstrate any differences between groups in clinically relevant end-points. In conclusion, these findings suggest that during normothermic CPB, small-dose epoprostenol therapy may reduce systemic oxygen consumption and splanchnic oxygen extraction.     

Myocardial preservation during coronary surgery with and without cardiopulmonary bypass

BACKGROUND: There is increased interest in coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB), although the preservation of the myocardium under such circumstances has not been properly investigated. The aim of this randomized study was to compare the changes in myocardial metabolism during CABG with and without CPB. METHODS: Myocardial energy metabolism and tissue injury during CABG was monitored in a series of 22 patients (11 with and 11 without CPB). RESULTS: The maximum myocardial lactate production was significantly higher (p = 0.02) in the group operated with CPB (0.56 mmol/L) than without it (0.17 mmol/L). A similar phenomenon was seen in the transcardiac pH differences (0.085 and 0.034 with and without CPB, p = 0.007). The postoperative peak values of creatine kinase-MB mass (15.1 vs 6.3 microg/L) and troponin I (13.8 vs 5.2 microg/L) were significantly higher (p < 0.001 and p = 0.008) with than without CPB. CONCLUSIONS: CABG on a beating heart is associated with better myocardial energy preservation and less myocardial damage compared with conventional CABG with CPB and intermittent antegrade mild hypothermic blood cardioplegia.     

库存红细胞清洗在新生儿及小婴儿体外循环手术中的应用

目的 对比体外循环(CPB)心脏手术中接受洗涤及未洗涤的库存红细胞(PRBC)对血清钾离子浓度(K+)及乳酸浓度(LAC)的影响.方法 选取复杂先天性心脏病(先心病)行CPB心脏手术的新生儿及小婴儿为研究对象,排除术前血乳酸大于3.0mmol/L的病婴.对照组(15例)接受未洗涤的PRBC进行CPB预充及术中添加,试验组(15例)接受用血液回收机(Medtronic Autolog)洗涤过的PRBC.在CPB前、CPB 3、15min、CPB复温、停止CPB前、术毕、术后4、24h比较血K+及LAC浓度.结果 洗涤PRBC显著降低供血中K+浓度[从(19.3±0.9)mmol/L降至(1.1±0.3)mmol/L,p<0.001]及IAC浓度[从>15mmol/L降至(7.8±1.2)mmol/L,P<0.001].对照组预充液的K+及ILAC浓度显著高于试验组[K+(9.0±0.5)rranol/L对(2.6±0.1)mmol/L,P<0.001;LAC浓度(9.5±0.5)mmol/L对(4.7±1.1)nrml/L,P<0.001].CPB 3min、CPB复温时对照组血清K+浓度显著高于试验组[CPB 3 min(5.6±0.9)mmol/L对(3.5±0.4)mmol/L,P<0.01;CPB复温时(4.8±0.7)mmol/L对(3.7±0.6)mmol/L,P<0.01];其余时点对照组K+浓度高于试验组,差异无统计学意义.CPB 3、15 min、CPB复温、停止CPB前、术毕、术后4 h对照组IAC浓度高于试验组,但差异无统计学意义.结论 洗涤PRBC降低血清钾及乳酸负荷,可预防cPB中高血钾.在新生儿及小婴儿复杂先心病CPB手术中应考虑应用清洗PRBC.     

Lack of utility of arteriojugular venous differences of lactate as a reliable indicator of increased brain anaerobic metabolism in traumatic brain injury

OBJECT: Ischemic lesions are highly prevalent in patients with traumatic brain injuries (TBIs) and are the single most important cause of secondary brain damage. The prevention and early treatment of these lesions is the primary aim in the modem treatment of these patients. One of the most widely used monitoring techniques at the bedside is quantification of brain extracellular level of lactate by using arteriojugular venous differences of lactate (AVDL). The purpose of this study was to determine the sensitivity, specificity, and predictive value of AVDL as an indicator of increases in brain lactate production in patients with TBIs. METHODS: Arteriojugular venous differences of lactate were calculated every 6 hours using samples obtained though a catheter placed in the jugular bulb in 45 patients with diffuse head injuries (57.8%) or evacuated brain lesions (42.2%). Cerebral lactate concentration obtained with a 20-kD microdialysis catheter implanted in undamaged tissue was used as the de facto gold standard. Six hundred seventy-three AVDL determinations and cerebral microdialysis samples were obtained simultaneously; 543 microdialysis samples (81%) showed lactate values greater than 2 mmol/L, but only 21 AVDL determinations (3.1%) showed an increase in brain lactate. No correlation was found between AVDL and cerebral lactate concentration (p = 0.014, p = 0.719). Arteriojugular venous differences of lactate had a sensitivity and specificity of 3.3 and 97.7%, respectively, with a false-negative rate of 96.7% and a false-positive rate of 2.3%. CONCLUSIONS: Arteriojugular venous differences of lactate do not reliably reflect increased cerebral lactate production and consequently are not reliable in ruling out brain ischemia in patients with TBIs. The clinical use of this monitoring method in neurocritical care should be reconsidered.     

High intratendinous lactate levels in painful chronic Achilles tendinosis. An investigation using microdialysis technique.

In this investigation the microdialysis technique was used to study the concentrations of lactate in Achilles tendons with painful chronic tendinosis and in normal pain-free tendons. In four patients (mean age 40.7 years) with a painful thickening localized at the 2-6 cm level in the Achilles tendon (chronic Achilles tendinosis) and in five controls (mean age 37.2 years) with normal Achilles tendons the local concentrations of lactate were registered under resting conditions. All tendons were examined using ultrasonography. In the tendons with tendinosis the painful thickening corresponded to a widened tendon and structural tendinosis changes. Normal tendons showed no widening and a normal structure. A standard microdialysis catheter was inserted into the Achilles tendon under local anesthesia. Samplings were done every 15 min during a 4 h period. The results showed significantly higher mean concentrations of lactate in tendons with tendinosis compared to normal tendons (2.15 mmol/l vs. 1.14 mmol/l). The lactate concentrations in the tendons with tendinosis were stable, and approximately twofold higher than in the normal tendons during the whole 4 h investigation period. In conclusion, the higher concentrations of lactate in Achilles tendons with painful tendinosis indicate that there are anaerobic conditions in the area with tendinosis. The importance of this finding for the pathogenesis and pain mechanisms in this chronic condition needs to be further investigated.     

Red blood cell energy metabolism during cardiopulmonary bypass

BACKGROUND: During cardiopulmonary bypass (CPB) an intracellular ATP deficit could theoretically play a role in changes of erythrocyte shape and deformability caused by mechanical trauma. We therefore studied erythrocyte energy metabolism in 12 patients undergoing normothermic CPB for myocardial revascularization. METHODS: Blood samples were collected prior to and 45 minutes after CPB beginning and analyzed for erythrocyte ATP, ADP, and AMP and their metabolites, erythrocyte NAD and NADP, plasma and whole blood lactate (Lact(p) and Lact(b) respectively), and whole blood pyruvate (Pyr(b)). RESULTS: Values were expressed as mean +/- standard deviation or median (lower and higher quartiles) on the ground of a test for normality. During CPB erythrocyte nucleotides and their metabolites did not change significantly (ATP: 60.2+/-12.1 vs. 68.3+/-13.0; ADP: 12.2+/-3.6 vs. 12.0+/-3.1; AMP: 0.43+/-24 vs. 0.44+/-0.26; adenosine: 0.063 (0.034-0.203) vs. 0.77 (0.032-0.221); inosine: 0.064 (0.023-0.072) vs. 0.075 (0.025-0.111); hypoxanthine: 0.330+/-0.272 vs. 0.367+/-0.223; xanthine: 0.193+/-0.090 vs. 0.220+/-0.095; NAD: 3.149+/-0.743 vs. 3.358+/-0.851; values in microM/mM packed red blood cell hemoglobin) while NADP increased (2.110+/-0.390 vs. 2.433+/-0.288 microM/mM packed red blood cell hemoglobin; p<0.05). Ringer lactate, with which the extracorporeal circuit was primed, caused Lact(p) to increase (1.87+/-0.81 vs. 3.27+/-1.15 mM/l; p<0.01). Some lactate entered erythrocytes since Lact(p)/Lact(b) ratio did not change (1.09+/-0.25 vs. 1.07+/-0.23) and some was transformed into pyruvate since Pyr(b) increased [62.9 (30.3-73.3) vs. 100.5 (61.0-146.9) microM/l; p<0.01]. Lact(b)/Pyr(b) ratio did not change significantly [22.6 (16.1-40.5) vs. 27.9 (17.5-35.2)] so that NAD/NADH ratio and, consequently, the rate of glycolysis were unlikely to change too. CONCLUSIONS: Erythrocyte energy metabolism is not affected by CPB, at least during the period of time taken into account in this study.     

Washing of irradiated red blood cells prevents hyperkalaemia during cardiopulmonary bypass in neonates and infants undergoing surgery for complex congenital heart disease.

OBJECTIVE: High concentrations of potassium and lactate in irradiated red cells transfused during cardiopulmonary bypass may have detrimental effects on infants and neonates undergoing cardiac surgery. The effects of receiving washed and unwashed irradiated red cells from the cardiopulmonary circuit on serum potassium and lactate concentrations were compared. METHODS: The study population included neonates and infants undergoing heart surgery for complex congenital heart disease. A control group (n=11) received unwashed irradiated red cells and the study group (n=11) received irradiated red cells washed in a cell saver (Dideco Electa) using 900ml of 0.9% saline prior to pump priming. Potassium and lactate concentrations were compared before, during and after bypass. RESULTS: Washing irradiated red cells reduced donor blood [potassium] from>20 to 0.8+/-0.1mmol/l, and [lactate] from 13.7+/-0.5 to 5.0+/-0.3mmol/l (p<0.001). The resulting prime had significantly lower [potassium] and [lactate] than the unwashed group (potassium 2.6+/-0.1 vs 8.1+/-0.4mmol/l, p<0.001; lactate 2.6+/-0.2 vs 4.6+/-0.3mmol/l, p<0.001). Peak [potassium] in the unwashed group occurred 3 minutes after going on bypass (4.9+/-0.3mmol/l) and during rewarming (4.9+/-0.4mmol/l). These were significantly higher than the washed group (3.1+/-0.1, p<0.001 and 3.0+/-0.1mmol/l, p<0.001). The [potassium] was greater than 6.0mmol/l for 4 out of these 11 unwashed patients compared with none of the washed group. Immediately post-bypass the washed group had significantly lower serum [potassium] (3.2+/-0.1 vs 4.2+/-0.2mmol/l, p=0.002). There was no significant difference in [lactate] between groups during and after cardiopulmonary bypass. CONCLUSIONS: The washing of irradiated red cells reduces potassium and lactate loads and prevents hyperkalaemia during cardiopulmonary bypass. The washing of irradiated red cells should be considered in neonates and infants undergoing cardiac surgery for complex congenital heart disease.     

Myocardial lactate metabolism in relation to preoperative regional wall motion and to early functional recovery after coronary revascularization

OBJECTIVE: To evaluate myocardial lactate metabolism as a marker of functional status after surgical coronary revascularization. DESIGN: Single-center, prospective, cohort study. SETTING: Tertiary care teaching hospital. PARTICIPANTS: Fifty patients with stable angina, ejection fraction >0.40, undergoing coronary artery bypass surgery for multiple-vessel disease. MEASUREMENTS AND MAIN RESULTS: Before (T1) and 30 minutes (T2) after coronary artery bypass grafting, the authors simultaneously sampled blood from artery and coronary sinus to determine myocardial lactate dynamics and performed transesophageal echocardiography (TEE) to assess segmental wall motion. Wall motion score index (WMSI) was calculated with an online/offline comparison. At T2, WMSI improved from 1.40 +/- 0.31 to 1.17 +/- 0.23 (p = 0.0001). Preoperatively, 2 patterns of lactate balance were found: 39 patients were lactate extractors (17% +/- 10%) and 11 were lactate producers (-11% +/- 11%). At T2, lactate metabolism was shifted towards a pattern opposite to the baseline: delta lactate extraction was -8% +/- 16% in extractors at T1 versus 7% +/- 9% in producers at T1 (p = 0.003). Changes in WMSI were not correlated with changes in lactate utilization. No single preoperative variable predicted postoperative WMSI or its changes from baseline. Cardiopulmonary bypass (CPB) time was the only significant predictor of postoperative lactate extraction by multivariate regression (r = -0.46, p = 0.001): at T2, patients in the highest CPB time quartile showed frank lactate production (-6% +/- 13%) when compared with those in the lowest quartile (15% +/- 11%, p = 0.005). However, postoperative WMSI was similar in different CPB time groups. CONCLUSIONS: Myocardial lactate metabolism pattern is not associated with functional status before and early after successful coronary revascularization. CPB time was the only significant predictor of postoperative lactate extraction. Measurement of lactate does not appear to be a valuable tool to assess the coupling of myocardial regional function and metabolism in the setting of coronary artery surgery and mild-to-moderate functional impairment.     

Effects of temperature strategy during cardiopulmonary bypass on cerebral oxygen balance

BACKGROUND: Cerebral injury is the most serious complication of cardiopulmonary perfusion (CPB). With the advent of warm heart surgery, the effect of temperature strategy during perfusion and its effect on cerebral oxygen balance needs further study. METHODS: Three groups of patients (n=8, each) undergoing coronary artery bypass graft (CABG) surgery were studied. Group H, M and N underwent CPB at 28 degrees C, 32 degrees C and normothermia (>36 degrees C), respectively. The extracorporeal circuit was primed with Hartmann's solution 2.5 l and flow of 1.8 l min(-1) m(-2) at 28 degrees C, and 2.4 1 min-1 m(-2) at 32 degrees C and normothermia. All patients had a 4F oximetry catheter (Opticath, Oximetrix, Abbott Laboratories) inserted in the right jugular bulb for continuous measurement of jugular venous oxygen saturation (sjvO2). Data was collected at six specific times: T1- within 5 min before initiation of CPB, T2 - within the first minute after CPB, T3 - during stable temperature on CPB (28 degrees C, 32 degrees C, >36 degrees C), T4 - during rewarming at 34 degrees C in groups H and M, 15 min before coming off CPB in group N, T5 - 15 min after CPB, T6 - skin closure. At each time mean arterial pressure (MAP) and sjvO2 were recorded. Arterial blood and jugular venous blood were sampled for measurement of arterial oxygen saturation (saO2) and jugular venous lactate (sjv(lactate)), respectively. RESULTS: SjvO2 values decreased at times T2, T3 and T4 when compared to baseline (p<0.05) but there were no significant group differences at any time. Cerebral arteriovenous oxygen saturation (a-jvO2) differences mirrored sjvO2 changes. Sjv(lactate) values increased from baseline following CPB but fell consistently with time - there were no significant group differences at each time point. SjvO2 and a-jvO2 values were not significantly correlated with sjv(lactate). CONCLUSION: During pump flows employed in this study, cerebral oxygen balance and perfusion appear unaffected by temperature.