Protective effect of dexmedetomidine on perioperative myocardial injury in patients with Stanford type-A aortic dissection

OBJECTIVE

To investigate the protective effect and mechanism of dexmedetomidine (Dex) on perioperative myocardial injury in patients with Stanford type-A aortic dissection (AD).

METHODS

Eighty-six patients with Stanford type-A AD were randomly divided into Dex and control groups, with 43 cases in each group. During the surgery, the control group received the routine anesthesia, and the Dex group received Dex treatment based on routine anesthesia. The heart rate (HR) and mean arterial pressure (MAP) were recorded before Dex loading (t0), 10 min after Dex loading (t1), at the skin incision (t2), sternum sawing (t3), before cardiopulmonary bypass (t4), at the extubation (t5), and at end of surgery (t6). The blood indexes were determined before anesthesia induction (T0) and postoperatively after 12h (T1), 24h (T2), 48h (T3), and 72h (T4).

RESULTS

At t2 and t3, the HR and MAP in the Dex group were lower than in the control group (P < 0.05). Compared with the control group, in the Dex group at T1, T2, and T3, the serum creatine kinase-MB, cardiac troponin-I, C-reactive protein, and tumor necrosis factor-α levels were decreased, and the interleukin-10 level, the serum total superoxide dismutase, and total anti-oxidant capability increased, while the myeloperoxidase and malondialdehyde levels decreased (all P < 0.05).

CONCLUSIONS

Dex treatment may alleviate perioperative myocardial injury in patients with Stanford type-A AD by resisting inflammatory response and oxidative stress.

Evaluation in an emergency department of rapid separator tubes containing thrombin for serum preparation prior to hs-cTnT and CK-MB analyses

Background

In our emergency department, we collect blood in Rapid Serum Tubes (RSTs; Becton Dickinson, Franklin Lakes, NJ), in which clotting times are reduced. We investigated the influence of RST use on cardiac troponin T (hs-cTnT) and creatine kinase-MB (CK-MB) test results, in comparison with the use of tubes featuring a separator gel containing a clotting activator (SSTs; Green-vac, Yongin, Korea).

Methods

Samples from 60 patients were divided into equal aliquots and placed into RSTs and SSTs; hs-cTnT and CK-MB concentrations were determined using an autoanalyzer (Elecsys 2010) running commercial assays (Roche Diagnostics, Penzberg, Germany). Between-tube differences in CK-MB and hs-cTnT values were compared using the paired t-test, and correlations among variables were evaluated by calculation of Spearman correlation coefficients (r values). Deming regression analysis was performed and Bland-Altman plots were constructed.

Results

The hs-cTnT and CK-MB test results obtained from samples placed into RSTs and SSTs did not differ (p > 0.1). The correlations between the concentrations of hs-cTnT and CK-MB in samples placed into RSTs and SSTs were good; both r values were unity (p < 0.001). Deming regression analysis yielded the equation: RST [hs-cTnT] = 0.98 SST [hs-cTnT] + 0.69 pg/ml; and RST [CK-MB] = 0.95 SST [CK-MB]–0.09 ng/ml. The biases of 1.4 pg/ml (95% CI: minus 8.1–10.7 pg/ml) for hs-cTnT levels and 0.249 ng/ml (95% CI: minus 0.682–1.681 ng/ml) for CK-MB levels assayed using either tube was acceptable.

Conclusion

The hs-cTnT and CK-MB test results did not significantly differ when either tube was used. RST tube use was associated with a short clotting time; this was an advantage in an emergency laboratory setting.

A clinical prediction rule for early discharge of patients with chest pain

STUDY OBJECTIVE

Current risk stratification tools do not identify very-low-risk patients who can be safely discharged without prolonged emergency department (ED) observation, expensive rule-out protocols, or provocative testing. We seek to develop a clinical prediction rule applicable within 2 hours of ED arrival that would miss fewer than 2% of acute coronary syndrome patients and allow discharge within 2 to 3 hours for at least 30% of patients without acute coronary syndrome.

METHODS

This prospective, cohort study enrolled consenting eligible subjects at least 25 years old at a single site. At 30 days, investigators assigned a diagnosis of acute coronary syndrome or no acute coronary syndrome according to predefined explicit definitions. A recursive partitioning model included risk factors, pain characteristics, physical and ECG findings, and cardiac marker results.

RESULTS

Of 769 patients studied, 77 (10.0%) had acute myocardial infarction and 88 (11.4%) definite unstable angina. We derived a clinical prediction rule that was 98.8% sensitive and 32.5% specific. Patients have very low risk of acute coronary syndrome if they have a normal initial ECG, no previous ischemic chest pain, and age younger than 40 years. In addition, patients at least 40 years old and with a normal ECG result, no previous ischemic chest pain, and low-risk pain characteristics have very low risk if they have an initial creatine kinase-MB (CK-MB) less than 3.0 microg/L or an initial CK-MB greater than or equal to 3.0 microg/L but no ECG or serum-marker increase at 2 hours.

CONCLUSION

The Vancouver Chest Pain Rule for early discharge defines a group of patients who can be safely discharged after a brief evaluation in the ED. Prospective validation is needed.

A continuous displacement immunoassay for human heart-type fatty acid-binding protein in plasma

Human heart-type fatty acid-binding protein (FABP) is suggested as an early plasma marker of acute myocardial infarction (AMI), and several studies have proved that, for early diagnosis of AMI, FABP performs better than myoglobin, which is a more often used early marker protein. Because serial measurement of biochemical markers in plasma is now universally accepted as an important determinant in AMI diagnosis, a rapid and continuous measuring method for FABP would be desirable. The aim of the present study was to develop an immunoassay based on the principle of displacement and using a column for rapid and continuous measurement of FABP in plasma. Glass columns filled with Sepharose-bound FABP were loaded with a horseradish peroxidase (HRP)-labeled antibody (Ab) and equilibrated with human plasma. After reaching a stable baseline, human plasma spiked with FABP or plasma from AMI patients was added. The Ab-HRP complex dissociated due to the presence of FABP in the plasma and was subsequently quantified. For plasma from AMI patients (n=5), the Ab-HRP level thus measured correlated with the corresponding plasma FABP concentration (R=0.96). The results of this study show the feasibility of a sensor for continuous monitoring of FABP in plasma.

Comparison of cardiac troponin I and creatine kinase ratios in the detection of myocardial injury after aortic surgery

BACKGROUND

Perioperative myocardial infarction may not be diagnosed correctly because World Health Organization criteria are often not met and creatinine kinase myocardial fraction (creatinine kinase/creatinine kinase MB isoenzyme; CK/CK-MB) ratios can be difficult to interpret. Cardiac troponin (cTn) I and cTnT are the most sensitive and specific markers of myocardial cell necrosis currently available but are not widely used in surgical practice. The aim was to compare cTnI and CK/CK-MB ratios in the detection of myocardial injury following aortic surgery.

METHODS

This was a prospective study of 59 patients undergoing elective (n = 28) or ruptured (n = 24) abdominal aortic aneurysm repair or elective aortofemoral bypass (n = 7). cTnI level was measured before operation and at 6, 24 and 48 h after surgery. The CK/CK-MB ratio was measured where cTnI was detectable.

RESULTS

Some 14 of 24 emergency and ten of 35 elective patients had detectable cTnI (greater than 0.5 ng/ml) at one or more time-points. The CK/CK-MB ratio was greater than 5 per cent in only four of 24 patients having an emergency operation and in none of the elective patients with detectable cTnI.

CONCLUSION

Over half of patients undergoing emergency operation and more than a quarter of those having elective aortic surgery suffered myocardial necrosis as determined by detectable cTnI levels. This was accompanied by a raised CK/CK-MB ratio in less than one-fifth of patients.

Certification of the mass concentration of creatine kinase isoenzyme 2 (CK-MB) in the reference material BCR 608

We describe the certification of a mass concentration value in the already prepared creatine kinase-2 reference material (BCR 608). Creatine kinase-2 was purified from human heart. The purified enzyme was diluted in order to measure its protein concentration by the Doetsch method. A protein concentration value of 124.30+/-13.17 mg/l was assigned to the stock solution of purified creatine kinase-2. This stock solution was diluted in 25 mmol/l piperazine-N,N'-bis[2-ethanesulfonic acid] (PIPES) pH 7.2, containing 2 mmol/l ADP, 5 mmol/l 2-mercaptoethanol, 154 mmol/l sodium chloride and 50 g/l human albumin to obtain a stable liquid standard of known creatine kinase-2 mass concentration (80.36 microg/l). This standard was then used to recalculate the creatine kinase-2 mass concentration measured in the BCR 608 material by immunoassay. The mass concentration of creatine kinase-2 in samples of reconstituted BCR 608 was certified to be 93.30+/-9.65 microg/l.

Soluble transferrin receptor (sTfR) concentration quantified using two sTfR kits: analytical and clinical performance characteristics

We compared the analytical and clinical performance characteristics of the Ramco and R&D Systems enzyme-linked immunosorbent assays (ELISAs) for quantifying serum levels of soluble transferrin receptor (sTfR). In addition, we determined both the number of samples required to determine the true individual mean sTfR concentration for a single individual and the critical difference (CD) between serial measurements that indicates a statistically significant change in sTfR concentration. sTfR concentration was determined in 127 serum samples selected retrospectively from males (n=32) and non-pregnant (n=40) and pregnant women (n=55). Intra- and inter-assay precision for both methods was good (CV values 5--10%) to excellent (CV values <5%) over a wide range of sTfR concentrations. Correlation between these methods was good (r=0.93); however, sTfR values by the R&D kit were approximately 2.9 times higher than values obtained using the Ramco kit on the same serum samples. Nevertheless, receiver-operator characteristic (ROC) curve analysis demonstrated that the diagnostic accuracy of both assays in discriminating between patients with iron-deficiency anemia (IDA) or anemia of chronic disease (ACD) was high (area-under-the-curve (AUC) values >0.95) and not significantly different (P=0.480). We determined that a minimum of 8 samples are required to determine an individual's true sTfR concentration, while a >40% difference between serial sTfR measurements would be required to indicate a statistically significant change in sTfR concentration. We concluded that both the Ramco and R&D Systems sTfR methods have similar analytical and clinical performance characteristics and were likely to be equally useful in discriminating between patients with biochemically defined IDA or ACD.

Comparison between strategies using creatine kinase-MB(mass), myoglobin, and troponin T in the early detection or exclusion of acute myocardial infarction in patients with chest pain and a nondiagnostic electrocardiogram

Different strategies using creatine kinase-MB(mass), myoglobin, and troponin T were compared in 738 patients admitted because of chest pain and an electrocardiogram not diagnostic of acute myocardial infarction. We conclude that a combination of creatine kinase-MB and troponin T during the first 6 hours enables early detection or exclusion of acute myocardial infarction in this population.

Creatine kinase 2 mass measurement: methods comparison and study of the matrix effect

Five different commercial immunoassays for the measurement of creatine kinase isoenzyme 2 mass concentration were compared using human plasma samples covering a wide range of creatine kinase 2 concentrations. The immunoassays studied differ in the detection systems, in the specificity of the antibodies and in the calibrators used. Intermethod comparison by regression analysis showed differences in the results of creatine kinase 2 mass concentration. The following ratios were deduced from the obtained equations: Elecsys=1.10xImmulite=1.20xIMx=1.26xACS:180= 1.33 x Stratus. The commutability of different materials prepared by diluting purified human creatine kinase 2 in biological and synthetic matrices was studied using the different immunoassays in comparison with human plasma specimens. Almost all the materials tested were not commutable.

Clinical evaluation of the CARDIAC STATus, a rapid immunochromatographic assay for simultaneous detection of elevated concentrations of CK-MB and myoglobin in whole blood

We studied the performance of the CARDIAC STATus, a new rapid, easy to perform qualitative whole blood bedside test for detection of elevated CK-MB and myoglobin in the emergency room. Blood samples from 182 consecutive patients with chest pain were drawn on admission and at five and seven hours after the onset of symptoms. The CARDIAC STATus tests were performed by coronary care unit nurses and, independently, by a trained laboratory technician. The results were compared with quantitative assays for CK-MB mass and myoglobin. At the end of the study, a second test series using a new lot number of cartridges was performed on the same blood samples because of possible elution buffer contamination. Nurses produced more false negative results than the technician (CK-MB 43 vs. 27 %, p=0.01, myoglobin 31 vs. 13%, p<0.0001), but the technician produced more false positive myoglobin results (9.3 vs. 5.5%, p=0.0001). In the second test series, the nurses produced significantly fewer false negative tests both for CK-MB (19%, p<0.0001) and myoglobin (13%, p=0.0002). The false negative rate for the technician was not different between the first and the second test series. The CARDIAC STATus yields a substantial number of false negative results both for CK-MB and myoglobin when compared to a quantitative assay, and therefore at present has limited value for ruling out an acute myocardial infarction.

Biological variation of cardiac markers: analytical and clinical considerations

The analytical, within-subject and between-subject components of variation were estimated for serum total creatine kinase (TCK) activity, CK-MB (creatine kinase-MB) activity, CK-MB mass, ratios of CK-MB activity and CK-MB mass to TCK activity and myoglobin concentration in a cohort of 16 apparently healthy subjects over 5 days. Analytical goals based on biological variation showed that, for all quantities except CK-MB mass, methodological improvement is warranted. All cardiac markers showed marked individuality which casts doubt on the utility of conventional population-based reference values as interpretative criteria. The critical differences required for significance of changes in serial results differ markedly from marker to marker and the data allow generation of objective criteria for monitoring individuals.