Acute heart failure after non-cardiac surgery: incidence, phenotypes, determinants and outcomes

Background

Primary acute heart failure (AHF) is an established and common cause of hospitalization. AHF may also develop secondarily, e.g. postoperatively (pAHF). Little is known about pAHF.

Purpose

To assess the incidence, phenotypes, determinants and outcomes of pAHF following non-cardiac surgery.

Methods

We prospectively included 9,164 consecutive patients at high cardiovascular risk undergoing 11,262 non-cardiac surgeries. The incidence, phenotypes, determinants and outcome of pAHF, centrally adjudicated by independent cardiologists, was determined. Logistic regression models identified the risk factors for pAHF. Cox regression analysis compared mortality and AHF readmission within 1 year in patients with and without pAHF. External validation was performed using a prospective cohort multicenter study of 1250 patients.

Results

The incidence of pAHF was 2.5% (95% confidence interval [CI] 2.2–2.8%). pAHF most often occurred on postoperative day 2 (median day 4). About half of pAHF (51%) occurred in patients without known HF (de novo pAHF), and 49% in patients with chronic HF. Preserved left ventricular ejection fraction (LVEF) was the dominant phenotype among de novo pAHF (72%), while reduced LVEF was dominant among pAHF in chronic HF (43%). Age, coronary artery disease, peripheral artery disease, diabetes, urgent/emergent surgery, chronic HF, atrial fibrillation, chronic obstructive pulmonary disease, anemia, and chronic myocardial injury were independent predictors of pAHF. Patients with pAHF had significantly higher all-cause mortality (44% vs. 11%, p<0.001) and AHF readmission (15% vs. 2%, p<0.001) within 1 year than patients without pAHF. pAHF was an independent predictor of all-cause mortality (adjusted hazard ratio [aHR] 1.7 [95% CI 1.3–2.2]; P<0.001) and AHF readmission (aHR 2.7 [95% CI 1.7–4.2]; P<0.001) within 1 year. Findings were confirmed in an external validation cohort of 1250 patients, e.g. incidence of pAHF 2.4% (95% CI, 1.6–3.3%).

Conclusions

pAHF frequent developed following non-cardiac surgery, being de novo in about half of cases, and associated with an unacceptable high mortality. Strategies focusing on early detection and treatment of pAHF seem warranted.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science FoundationSwiss Heart Foundation

Risk stratification of perioperative myocardial infarction/injury following noncardiac surgery in high risk patients

Background

Perioperative myocardial infarction/injury (PMI) screening is increasingly recommended by current guidelines. PMI is often caused by type 2 myocardial infarction, and risk stratification tools for these patients are lacking.

Purpose

To derive and internally validate a risk prognostication model for PMI of likely type 2 infarction (lT2MI)

Methods

We included consecutive high-risk patients undergoing noncardiac surgery into this prospective multicenter study. Patients received a systematic routine PMI screening with pre- and postoperative measurement of cardiac troponin (cTn). PMI was prospectively defined as an absolute increase of cTn above the preoperative value. PMI etiology was centrally adjudicated and hierarchically classified by 2 independent physicians based on all clinical information obtained during index hospitalization and selected those with lT2MI for further analyses. To identify risk factors and allow risk stratification in lT2MI, we prespecified that only perioperative variables should be included into the model. We constructed a logistic binary regression model for major adverse cardiac events (MACE) within 120 days, including variables available at time of clinical evaluation: additional symptoms or ECG-criteria required according to the Universal Definition of Myocardial Infarction, absolute increase in cTn (categorized according to level of absolute increase 1–<2 times the 99th percentile, ≥2 to <4 times, and ≥4 times), urgency of procedure, perioperative bleeding (drop in haemoglobin >30g/L or deemed relevant for PMI by adjudicator), and ESC/ESA surgery risk (low, medium, high risk of cardiac events). Variables were omitted from the final model if the p-value was >0.05. Variable levels with similar odds ratios were grouped for simplification of the prognostic model. We constructed a calibration plot and calculated the area under the receiver-operating characteristics curve (AUC) and Brier Score. For internal validation we calculated the predicted probabilities and classified patients into low-risk (predicted event rate <10%), intermediate range (10–20%), and high-risk (>20%), and compared the predicted with the observed event rate.

Results

PMI occurred in 1016/7754 patients (13.1%) of which 750/1016 (73.8%) were adjudicated as lT2MI. MACE within 120 days occurred in 118/750 (15.7%) patients. The initial and final logistic prognostic model for 120-day MACE or death is shown in the table. Internal validation found a good fit of predicted and observed event rate following bootstrapping of 1000 iterations (Figure 1), a good AUC of 0.71 and a Brier score of 0.12.

Conclusion

The derived risk prognostication model for PMI of lT2MI can aid in the stratification of patients and support clinical decision making following noncardiac surgery.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Swiss National Science FoundationSwiss Heart Foundation

Renal failure: a non-cardiac source of high sensitivity cardiac troponin T

Background

Circulating high sensitivity cardiac troponin T (hs-cTnT) levels are frequently elevated in patients with end-stage renal disease (ESRD). The underlying pathophysiology is largely unknown. Currently, accumulation of hs-cTnT due to impaired renal clearance, as well as increased production caused by chronic cardiomyocyte injury is being discussed.

Purpose

The aim of this study was to assess the relative contribution of impaired renal clearance as a non-cardiac source of elevated hs-cTnT concentrations, using renal transplantation as an in vivo model of rapidly improved renal function and on a short-term basis rather unchanged cardiac pathology.

Methods

This single-centre study was a secondary analysis within a prospective active surveillance study program for perioperative myocardial infarction/injury (PMI). 42 consecutive high-risk patients undergoing renal transplantation without evidence of PMI were included. Serial creatinine and hs-cTnT (Elecsys, Roche) measurements were performed pre-transplant (baseline) and post-transplant on day (d) 1, between d2 and d5, and between d14 and d180. The effect of time and creatinine on hs-cTnT was estimated with a log-level non-linear mixed-effects model, where time and creatinine were treated as the fixed effects and subject as the random effect. Natural cubic splines were used to account for nonlinearity in the fixed effects.

Results

Baseline median serum creatinine concentration was 616 umol/L [interquartile range (IQR) 477–825], and significantly fell to 425 umol/L (IQR 313–619) on d1, 285 umol/L (IQR 194–509) on day2–5, and 116 umol/L (IQR 100–166) on d14–180 (p<0.001, p<0.001, and p=0.043, respectively; Figure 1A).

Pre-transplant hs-cTnT concentrations were above the 99th percentile (14ng/L) in all patients, median hs-cTnT concentration was 50 ng/L (IQR 35–70). In parallel to the fall in serum creatinine from baseline to d1, hs-cTnT concentrations significantly fell to 28 ng/L (IQR 15–40) on d1 (p<0.001), and then remained constant on d2–5 (27 ng/L (IQR 18–35)), and on d14–180 (24 ng/L (IQR 19–28); Figure 1B).

The mixed-effect model showed a significant decrease of hs-cTnT between baseline and d1 (p<0.001), whereas no significant change between d1 and d2 (p=0.82) occurred (Figure 2).

Conclusion

In contrast to the continuously falling serum creatinine levels, hs-cTnT concentrations reduced by about 50% only within the first 24 hours with a functional graft and then remained elevated above the 99th percentile. This suggests, that ESRD is a non-cardiac source of elevated circulating hs-cTnT concentrations, which contributes about 50%, while the other 50% seem related to chronic cardiomyocyte injury. Further studies assessing the long-term effect of renal transplantation on hs-cTnT levels and cardiac function are needed.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Swiss National Science FoundationSwiss Heart Foundation

Long term outcomes in different aetiologies of perioperative myocardial infarction/injury after noncardiac surgery

Background

Perioperative myocardial infarction/injury (PMI) occurring in the first 48h following noncardiac surgery is a frequent cardiac complication. Better understanding of the underlying aetiologies is urgently needed.

Aim

To explore the association of different aetiologies of PMI with long term outcomes.

Methods

In this prospective multicenter observational study, PMI aetiology was centrally adjudicated and hierarchically classified by two independent physicians based on all information obtained during clinically-indicated PMI work-up including cardiac imaging among consecutive high-risk patients undergoing major noncardiac surgery. PMI aetiology was classified into “extracardiac” if caused by a primarily extracardiac disease such as severe sepsis or pulmonary embolism; and “cardiac”, further subtyped into type 1 myocardial infarction (T1MI), tachyarrhythmia, acute heart failure (AHF), or likely type 2 myocardial infarction (lT2MI). Major adverse cardiac events (MACE) including T1MI, AHF (both only from day 3 to avoid inclusion bias), life-threatening arrhythmia, and cardiovascular death as well as all-cause death were assessed during 365-days follow-up.

Results

PMI occurred in 1016/7754 patients (13.1%). At least one MACE occurred in 684/7754 patients (8.8%) and 818/7754 patients died (10.5%) within 365 days. MACE and all-cause death occurred in 51% (95% CI 31–60) and 38% (95% CI 29–47), 41% (95% CI 28–51) and 27% (95% CI 16–34), 57% (95% CI 41–69) and 40% (95% CI 25–53), 64% (95% CI 45–76) and 49% (95% CI 30–62), as well as 25% (95% CI 22–28%) and 17% (95% CI 14–20) of patients with extracardiac PMI, T1MI, tachyarrhythmia, AHF, and lT2MI, respectively. These associations were confirmed in multivariable analysis.

Conclusion

At 365 days, most PMI aetiologies have unacceptably high rates of MACE and all-cause death, highlighting the urgent need for more intensive treatments.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Swiss National Science FoundationRoche Diagnostics

Direct comparison of the accuracy of preoperative high-sensitivity cardiac troponin T to predict mortality, acute heart failure and perioperative myocardial infarction/injury after non-cardiac surgery

Background

Death, acute heart failure (AHF) and perioperative myocardial infarction/injury (PMI) are the most relevant cardiovascular complications following non-cardiac surgery. Unfortunately, the incidence of these complications are higher than expected. Currently available tools to predict these complications have only modest accuracy.

Purpose

To determine the accuracy of preoperative high-sensitivity cardiac troponin T (hs-cTnT) concentrations for prediction of mortality, AHF and PMI after non-cardiac surgery.

Methods

We prospectively included 4,709 patients at high cardiovascular risk undergoing non-cardiac surgery. Hs-cTnT concentrations were measured before surgery and, daily after surgery, for two days. PMI was defined as an absolute increase of 14ng/L (the 99th percentile of the assay used) from hs-cTnT baseline values. The primary endpoint was the diagnostic accuracy of preoperative hs-cTnT concentration to predict death, AHF and PMI within 30 days, as quantified by the area under the receiving-operating curve (AUC). Multivariate logistic regression analysis was performed to test the association between preoperative hs-cTnT and each endpoint.

Results

All-cause mortality occurred in 133 (3%), AHF in 84 (2%) and PMI in 742 (16%) patients. Preoperative hs-cTnT concentrations had good accuracy for prediction of death, AHF and PMI (AUC = 0.75 [95% CI, 0.71–0.79], 0.72 [95% CI, 0.67–0.77] and 0.73 [95% CI, 0.71–0.75], respectively). After adjusting for confounders, hs-cTnT remained an independent predictor for death with an adjusted odds ratio (aOR) of 2.1 (95% CI, 1.7–2.7, P<0.001) and for PMI (aOR 2.2, 95% CI, 1.9–2.4, P<0.001), but not for AHF (aOR 1.0, 95% CI, 0.7–1.4, P=0.99). An hs-cTnT concentration below 5ng/L was found in 526 (11%) patients, and this cut-off yielded a negative predictive value of 99.6% for the occurrence of death, 99.2% for AHF and 95.6% for PMI.

Conclusion

The preoperative hs-cTnT concentration has a good accuracy to predict mortality, AHF and PMI after non-cardiac surgery, but is an independent predictor only for mortality and PMI. A cut-off value of 5ng/L identifies a subgroup of patients at low risk for these complications.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Swiss National Foundation, Swiss Herat Foundation

A European consensus statement on the use of four-factor prothrombin complex concentrate for cardiac and non-cardiac surgical patients

Modern four-factor prothrombin complex concentrate was designed originally for rapid targeted replacement of the coagulation factors II, VII, IX and X. Dosing strategies for the approved indication of vitamin K antagonist-related bleeding vary greatly. They include INR and bodyweight-related protocols as well as fixed dose regimens. Particularly in the massively bleeding trauma and cardiac surgery patient, four-factor prothrombin complex concentrate is used increasingly for haemostatic resuscitation. Members of the Transfusion and Haemostasis Subcommittee of the European Association of Cardiothoracic Anaesthesiology performed a systematic literature review on four-factor prothrombin complex concentrate. The available evidence has been summarised for dosing, efficacy, drug safety and monitoring strategies in different scenarios. Whereas there is evidence for the efficacy of four-factor prothrombin concentrate for a variety of bleeding scenarios, convincing safety data are clearly missing. In the massively bleeding patient with coagulopathy, our group recommends the administration of an initial bolus of 25 IU.kg^-1 . This applies for: the acute reversal of vitamin K antagonist therapy; haemostatic resuscitation, particularly in trauma; and the reversal of direct oral anticoagulants when no specific antidote is available. In patients with a high risk for thromboembolic complications, e.g. cardiac surgery, the administration of an initial half-dose bolus (12.5 IU.kg^-1 ) should be considered. A second bolus may be indicated if coagulopathy and microvascular bleeding persists and other reasons for bleeding are largely ruled out. Tissue-factor-activated, factor VII-dependent and heparin insensitive point-of-care tests may be used for peri-operative monitoring and guiding of prothrombin complex concentrate therapy.

P2532Incidence and outcome of perioperative myocardial infarction/injury after non-cardiac surgeries diagnosed by high-sensitivity cardiac troponin I

Background

In order to differentiate perioperative myocardial infarction/injury (PMI) after non-cardiac surgery from preexisting cardiomyocyte injury from chronic disorders, recent studies have shown the importance of using an acute absolute increase as a criterion for PMI. For high-sensitivity troponin T (hs-cTnT), PMI defined as an absolute increase of 14ng/L (the 99th percentile) has been shown to be strongly associated with 30-day mortality. Until now, no data on hs-cTnI are available. This is a major unmet clinical need, as relevant differences between hs-cTnT and hs-cTnI have recently been identified and, as worldwide hs-cTnI is more commonly used as compared to hs-cTnT. We hypothesized that applying the same criterion to hs-cTnI, would reveal a similar association with outcomes.

Purpose

To evaluate the incidence and outcome of PMI diagnosed by hs-cTnI after non-cardiac surgery.

Methods

We included prospectively consecutive high cardiovascular risk patients undergoing non-cardiac surgery. Hs-cTnI concentrations were measured before surgery and, daily after surgery, for three days. PMI was defined as an absolute rise of ≥26ng/L (the 99th percentile of the assay studied) from baseline values. The primary outcome was major adverse cardiovascular events (MACE), a composite of cardiovascular death, myocardial infarction, acute heart failure and arrhythmias, and the secondary outcome was all-cause mortality, within 30 days and one year.

Results

We included 2,018 patients submitted to 2,551 surgeries. Patients had median age of 73 years (IQR 68–79) and 56% were male. After surgery, 231 patients (9%, 95% CI 8–10%) fulfilled PMI diagnostic criterion. Patients with PMI had higher rates of MACE than patients without PMI, at 30 days (13% vs. 2%; P<0.001) and, at one-year follow-up (25% vs. 8%; P<0.001). All-cause mortality was also higher in PMI patients within 30 days and one year (9% vs. 1.5% and, 22% vs. 8%, respectively; P<0.001). In multivariate cox regression analysis, PMI showed a hazard ratio (HR) of 4.7 (95% CI, 2.9–7.6; P<0.001) within 30 days, and a HR of 2.7 (95% CI, 2.0–3.7; P<0.001) within one year for the occurrence of MACE. For total mortality, PMI showed a HR of 3.8 (95% CI, 2.1–6.8; P<0.001) within 30 days and a HR of 2.0 (95% CI, 1.4–2.7; P<0.001) after one year.

Conclusion

PMI is frequent and associated with high rates of MACE and mortality in short- and long-term follow-up after non-cardiac surgery, regardless of the high-sensitivity troponin assay used for diagnosis.

Acknowledgement/Funding

Swiss Heart Foundation, University basel, Abbott, Astra zeneca, Forschungsfond Kantonsspital Aarau, Cardiovascular Research Foundation Basel, FAPESP

P5980Etiology of perioperative myocardial injuries after non-cardiac surgery and associated outcomes

Background

Perioperative myocardial injuries (PMI) are a common complication following non-cardiac surgery associated with significantly increased postoperative mortality. Due to its mostly asymptomatic presentation it is currently often missed in clinical routine. With the advent of routine screening PMI will be an increasingly recognised. Therefore, a more detailed understanding of the different etiologies causing PMI is needed to guide management.

Methods

We included consecutive high-risk patients (defined as known cardiovascular disease or aged ≥65 years) undergoing major non-cardiac surgery at two hospitals into this prospective multicenter observational study. All patients received a systematic screening using cardiac troponin (cTn) in clinical routine for detection of PMI, defined as an absolute cTn-rise from baseline values within 3 days of surgery. Patients were contacted to assess occurrence of major adverse events (MACE) including all-cause death at 30-days. First, we identified preoperative existing comorbidities as well as perioperative factors associated with PMI by multivariable regression analysis. Second, PMI were centrally adjudicated to identify predefined subtypes (“type I myocardial infarction (T1MI)”, “acute heart failure” (AHF), “tachyarrhythmia”, “extra-cardiac” triggers, “unknown”) by two independent reviewers using all clinical information available, and subtypes tested for association with 30-day (MACE).

Results

From 2014 to 2016 we enrolled 4250 patients undergoing 5375 surgeries. PMI occurred after 785 (14,5%) surgeries. Occurrence of PMI was more frequent with older age and cardiovascular comorbidities, especially insulin-dependent diabetes mellitus and chronic kidney disease. Perioperatively multiple known type II triggers (hypotension, bleeding, hypoxemia, tachycardia, length of surgery) were associated with PMI. Only 5,0% of PMI were adjudicated as “T1MI”, 4,3% as “AHF”, 4,3% as “tachyarrhythmia”, 12,0% “extra-cardiac” and the majority of 74,4% as “unknown”. The subtypes were associated increased MACE-rates (24% for T1MI, 40% for “AHF”, 22% for “tachyarrhythmia”, 24% for “extra-cardiac”, 7,1% for “unknown”) compared to non-PMI patients (1,8%, p<0,001 see Figure).

MACE within 30 days following surgery

Conclusion

PMI occurs more likely in patients with preoperative existing comorbidities, PMI are associated with type II triggers in the intra- as well as postoperative period. We identified subtypes allowing a risk-stratification to identify high-risk types and guide clinical management.

Acknowledgement/Funding

Swiss National Science Foundation, Swiss Heart Foundation, Cardiovascular Research Foundation Basel, Roche

[Hereditary heterozygous factor VII deficiency in patients undergoing surgery : Clinical relevance]

BACKGROUND

A hereditary deficiency in coagulation factor VII (FVII) may affect the international normalized ratio (INR) value. However, FVII deficiency is occasionally associated with a tendency to bleed spontaneously. We hypothesized that perioperative substitution with coagulation factor concentrates might not be indicated in most patients.

METHODS

In this retrospective data analysis, we included all patients with hereditary heterozygous FVII deficiency who underwent surgical procedures at the University Hospital Basel between December 2010 and November 2015. In addition, by searching the literature, we identified publications reporting patients with FVII deficiency undergoing surgical procedures without perioperative substitution.

RESULTS

We identified 22 patients undergoing 46 surgical procedures, resulting in a prevalence of 1:1500-2000. Coagulation factor concentrates were administered during the perioperative period in 15 procedures (33 %), whereas in the other 31 procedures (66 %), FVII deficiency was not substituted. No postoperative bleeding or thromboembolic events were reported. In addition, we found no differences in pre- and postoperative hemoglobin and coagulation parameters, with the exception of an improved postoperative INR value in the substituted group. In the literature review, we identified five publications, including 125 patients with FVII deficiency, undergoing 213 surgical procedures with no perioperative substitution.

DISCUSSION

Preoperative substitution using coagulation factor concentrates does not seem to be mandatory in patients with an FVII level ≥15 %. For decision-making on preoperative substitution, patient history of an increased tendency to bleed may be more important than the FVII level or increased INR value.

Evaluation of a novel flow chamber system to assess clot formation in factor VIII-deficient mouse and anti-factor IXa-treated human blood

Blood flow properties play important roles in the regulation and formation of thrombus. To evaluate the influence of blood flow on thrombus formation in haemophilia, whole blood samples were obtained from FVIII-deficient (FVIII(-/-) ) and wild-type (FVIII(+/+) ) mice (n = 6 respectively), and from six human volunteers. Anti-FIXa aptamer was added to human blood to model acquired haemophilia B. Recalcified whole blood samples containing corn trypsin inhibitor and danaproid were perfused over the microchip coated with collagen and tissue thromboplastin at shear rates of 1100 and 110 s(-1) . Thrombus formation in the capillary was quantified by monitoring flow pressure changes. The intervals to 5 kPa (T(5) ) and 40 k Pa (T(40) ) reflect the onset and growth of thrombus formation respectively. Furthermore, fibrin and platelets in thrombi were quantified by immunostaining. T(5) at both shear rates were similar in FVIII(-/-) and FVIII(+/+) mice. T(40) of FVIII(-/-) mice (1569 ± 565 s) was significantly delayed compared with FVIII(+/+) mice (339 ± 78 s) at 110 s(-1) (P < 0.05), but not at 1100 s(-1) . The delay was normalized by adding human FVIII (2 IU mL(-1) ). Similarly, adding anti-FIXa aptamer to human blood prolonged T(40) at 110 s(-1) (P < 0.01), but not at 1100 s(-1) . Impaired production of fibrin due to anti-FIXa aptamer at 110 s(-1) was shown in the immunostained thrombus. Our perfusion experiments demonstrated that shear rates influence thrombus formation patterns in haemophilia, and that reduced activity of intrinsic tenase (FIXa-FVIIIa) becomes evident under venous shear rates.

Impact of loss of high-molecular-weight von Willebrand factor multimers on blood loss after aortic valve replacement

BACKGROUND

Severe aortic stenosis is associated with loss of the largest von Willebrand factor (vWF) multimers, which could affect primary haemostasis. We hypothesized that the altered multimer structure with the loss of the largest multimers increases postoperative bleeding in patients undergoing aortic valve replacement.

METHODS

We prospectively included 60 subjects with severe aortic stenosis. Before and after aortic valve replacement, vWF antigen, activity, and multimer structure were determined and platelet function was measured by impedance aggregometry. Blood loss from mediastinal drainage and the use of blood and haemostatic products were evaluated perioperatively.

RESULTS

Before operation, the altered multimer structure was present in 48 subjects (80%). Baseline characteristics and laboratory data were similar in all subjects. The median blood loss after 6 h was 250 (105-400) and 145 (85-240) ml in the groups with the altered and normal multimer structures, respectively (P=0.182). After 24 h, the cumulative loss was 495 (270-650) and 375 (310-600) ml in the groups with the altered and normal multimer structures, respectively (P=0.713). Multivariable analysis revealed no significant influence of multimer structure and platelet function on bleeding volumes after 6 and 24 h. After 24 h, there was no obvious difference in vWF antigen, activity, and multimer structure in subjects with and without the altered multimer structure before operation or in subjects with and without perioperative plasma transfusion.

CONCLUSIONS

The altered vWF multimer structure before operation was not associated with increased bleeding after aortic valve replacement. Our findings might be explained by perioperative release of vWF and rapid recovery of the largest vWF multimers.

Haemodilution-induced profibrinolytic state is mitigated by fresh-frozen plasma: implications for early haemostatic intervention in massive haemorrhage

BACKGROUND

Fibrinolysis contributes to coagulopathy after major trauma and surgery. We hypothesized that progressive haemodilution is responsible, at least in part, for increased fibrinolytic tendency of blood clot.

METHODS

The study was performed in two parts. First, whole blood (WB) samples collected from six healthy, consented volunteers were diluted in vitro with either saline or fresh-frozen plasma (FFP) to 40% and 15% of baseline. We quantified factor levels related to coagulation and fibrinolysis, and measured endogenous thrombin generation in undiluted control plasma samples and in samples diluted with saline or FFP. Additionally, thromboelastometry was used to assess susceptibility to fibrinolysis after adding tissue plasminogen activator in undiluted WB samples and in samples diluted with saline before and after substitution of fibrinogen or FFP. Secondly, as a model of in vivo haemodilution, we evaluated the same parameters before and after operation in nine consented patients undergoing off-pump coronary artery bypass surgery.

RESULTS

The dilution with saline caused dose-dependent decreases in plasma levels of coagulation and antifibrinolytic factors, and in thrombin generation. In FFP-supplemented samples, factor levels and thrombin generation were maintained within normal ranges. Fibrinolytic tendency was significantly higher after haemodilution with saline independent of fibrinogen substitution compared with FFP. Similarly, increased tendency for fibrinolysis was also observed in the in vivo haemodilution.

CONCLUSIONS

We demonstrated in vitro and in vivo that progressive haemodilution decreases endogenous antifibrinolytic proteins including alpha(2)-antiplasmin and thrombin-activatable fibrinolysis inhibitor, resulting in increased fibrinolytic tendency. Therefore, early fluid replacement therapy with FFP might be advantageous after massive haemorrhage.

Thrombin generation and fibrinolysis in anti-factor IX treated blood and plasma spiked with factor VIII inhibitor bypassing activity or recombinant factor VIIa

Activated prothrombin complex concentrates (aPCC) and recombinant activated factor VIIa (rFVIIa) are two important therapies in haemophilia patients with inhibitors and improve clot stability. We hypothesized that potential differences in procoagulant and fibrinolytic actions of aPCC and rFVIIa may lie in the clot stability against fibrinolytic activation. We used thrombin generation, fluorescence detection and thromboelastometry in anti-factor IXa (FIXa) aptamer-treated whole blood (WB) and plasma to evaluate: (i) generation of thrombin and activated factor X (FXa) and (ii) viscoelastic properties of blood clots in the presence of tissue plasminogen activator (tPA) after addition of aPCC (0.4 U mL(-1)) or rFVIIa (60 nm). Peak thrombin generation increased from 85 +/- 19 nm in aptamer-treated plasma to 276 +/- 83 nm and 119 +/- 22 nm after addition of aPCC and rFVIIa respectively (P < 0.001). FXa activity increased within 20 min by 87 +/- 6% and by 660 +/- 97% after addition of aPCC and rFVIIa respectively (P < 0.001). TPA-induced lysis time increased from 458 +/- 378 s in aptamer-treated WB to 1597 +/- 366 s (P = 0.001) and 1132 +/- 214 s (P = 0.075), after addition of aPCC and rFVIIa respectively. In this haemophilia model using the anti-FIXa aptamer, the larger amount of thrombin was generated with aPCC compared with rFVIIa, while FXa generation was more rapidly increased in the presence of rFVIIa. Furthermore, clot formation in anti-FIXa aptamer-treated WB was less susceptible to tPA-induced fibrinolysis after adding aPCC compared with rFVIIa.

Finding the optimal concentration range for fibrinogen replacement after severe haemodilution: an in vitro model

BACKGROUND

Replacement of fibrinogen is presumably the key step in managing dilutional coagulopathy. We performed an in vitro study hypothesizing that there is a minimal fibrinogen concentration in diluted whole blood above which the rate of clot formation approaches normal.

METHODS

Blood samples from six healthy volunteers were diluted 1:5 v/v with saline keeping haematocrit at 24% using red cell concentrates. We measured coagulation factors and thrombin generation in plasma at baseline and after dilution. Thromboelastometry was used to evaluate (i) speed and quality of clot formation in diluted samples supplemented with fibrinogen 50-300 mg dl(-1) and (ii) clot resistance to fibrinolysis. Diluted and undiluted samples with no added fibrinogen served as controls.

RESULTS

Coagulation parameters and platelets were reduced by 74-85% after dilution. Peak thrombin generation was reduced by 56%. Adding fibrinogen led to a concentration-dependent improvement of all thromboelastometric parameters. The half maximal effective concentration (EC50) for fibrinogen replacement in haemodiluted blood was calculated to be 125 mg dl(-1). Adding tissue plasminogen activator, 0.15 microg ml(-1), led to a decrease of clot firmness and lysis time.

CONCLUSIONS

The target plasma concentration for fibrinogen replacement was predicted by these in vitro results to be greater than 200 mg dl(-1) as only these concentrations optimized the rate of clot formation. This concentration is twice the level suggested by the current transfusion guidelines. Although improved, clots were prone to fibrinolysis indicating that the efficacy of fibrinogen therapy may be influenced by co-existing fibrinolytic tendency occurring during dilutional coagulopathy.

Randomized clinical trial of moxonidine in patients undergoing major vascular surgery

Background

Myocardial ischaemia is the leading cause of perioperative morbidity and mortality after surgery in patients with coronary artery disease. The aim of this study was to evaluate the effects of moxonidine, a centrally acting sympatholytic agent, on perioperative myocardial ischaemia and 1-year mortality in patients undergoing major vascular surgery.

Methods

In this double-blind, placebo-controlled two-centre trial, 141 patients were randomly assigned to receive moxonidine or placebo on the morning before surgery and on the following 4 days. Levels of cardiac troponin I (cTnI) were analysed before surgery and on days 1, 2, 3 and 7 thereafter. Holter electrocardiograms were recorded for 48 h starting before the administration of the study drug. Patients were followed daily during admission and by telephone interview 12 months after surgery.

Results

The incidence of raised perioperative cTnI levels or alteration in the ST segment in the Holter electrocardiogram or both was 40 per cent in the moxonidine group and 37 per cent in the placebo group (P = 0·694). All-cause mortality rates within 12 months were 10 per cent in the moxonidine group and 11 per cent in the placebo group (P = 0·870).

Conclusion

Small oral doses of moxonidine did not reduce the incidence of perioperative myocardial ischaemia and had no effect on mortality in patients undergoing vascular surgery. Registration number: NCT00244504 (http://www.clinicaltrials.gov).

The accuracy of non-invasive carbon dioxide monitoring: a clinical evaluation of two transcutaneous systems

We determined the accuracy of two transcutaneous carbon dioxide monitoring systems (SenTec Digital Monitor with V-Sign Sensor and TOSCA 500 with TOSCA Sensor 92) for the measurement of single values and trends in the arterial partial pressure of carbon dioxide in 122 adult patients during major surgery and in 50 adult patients in the intensive care unit. One or several paired measurements were performed in each patient. The first measurement was used to determine the accuracy of a single value of transcutaneous carbon dioxide; the difference between the first and the last measurements was used to analyse the accuracy and to track trends. We defined a 95% limit of agreement of <or=1 kPa as being clinically useful. There was insufficient agreement between transcutaneous carbon dioxide partial pressure values derived from the two systems and arterial carbon dioxide values for both single values and trends as defined by our suggested limit of agreement. We conclude that these systems cannot replace conventional blood gas analysis in the clinical setting studied.