High mortality associated with intracardiac and intrapulmonary thromboses after cardiopulmonary bypass

The Case of the "Disappearing Ventricle": A Report

Embolization of entrapped intracardiac air represents a significant risk to the patient undergoing open-heart surgery. Entrapment of as little as 0.5 mL of gas in the heart can cause temporary myocardial dysfunction, cardiac arrhythmias, and systemic emboli. In contrast, larger emboli can disrupt the evaluation of heart function by limiting visualization during echocardiography. We present the case of a 67-year-old male who presented with dizziness, nausea, and chest pain. A left heart catheterization revealed multi-vessel disease. Undergoing general anesthesia, the patient received three-vessel coronary artery bypass grafting, mitral valve repair, ring annuloplasty, and left atrial appendage closure. Upon aortic unclamping, transgastric echocardiography showed significant gas almost wholly obscuring the left heart chambers despite de-airing maneuvers. Successful resolution relied upon higher mean blood pressure and time, demonstrating the importance of intraoperative imaging and interdisciplinary collaboration.

Left Ventricular Unloading With Impella Versus IABP in Patients With VA-ECMO: A Systematic Review and Meta-Analysis

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) use for circulatory support in cardiogenic shock results in increased left ventricular (LV) afterload. The use of concomitant Impella or intra-aortic balloon pump (IABP) have been proposed as adjunct devices for LV unloading. The authors sought to compare head-to-head efficacy and safety outcomes between the 2 LV unloading strategies. We conducted a search of Medline, EMBASE, and Cochrane databases to identify studies comparing the use of Impella to IABP in patients on VA-ECMO. The primary outcome of interest was in-hospital mortality. The secondary outcomes included transition to durable LV assist devices/cardiac transplantation, stroke, limb ischemia, need for continuous renal replacement therapy, major bleeding, and hemolysis. Pooled risk ratios (RRs) with 95% confidence interval and heterogeneity statistic I2 were calculated using a random-effects model. A total of 7 observational studies with 698 patients were included. Patients on VA-ECMO unloaded with Impella vs IABP had similar risk of short-term all-cause mortality, defined as either 30-day or in-hospital mortality- 60.8% vs 64.9% (RR 0.93 [0.71 to 1.21], I2 = 71%). No significant difference was observed in transition to durable LV assist devices/cardiac transplantation, continuous renal replacement therapy initiation, stroke, or limb ischemia between the 2 strategies. However, the use of VA-ECMO with Impella was associated with increased risk of major bleeding (57.2% vs 39.7%) (RR 1.66 [1.12 to 2.44], I2 = 82%) and hemolysis (31% vs 7%) (RR 4.61 [1.24 to 17.17], I2 = 66%) compared with VA-ECMO, along with IABP. In conclusion, in patients requiring VA-ECMO for circulatory support, the concomitant use of Impella or IABP had comparable short-term mortality. However, Impella use was associated with increased risk of major bleeding and hemolysis.

Intracannula Thrombus Formation Associated With Dual Lumen ProtekDuo Cannula in Extracorporeal Membrane Oxygenation (ECMO)

Extracorporeal membrane oxygenation (ECMO) is used in cases of severe respiratory failure refractory to medical management. Use of ECMO is increasing, along with new cannulation strategies including oxygenated right ventricular assist devices (oxy-RVADs). Multiple dual lumen cannulas are now available, which increase the potential for patient mobility and decrease the number of vascular access sites. However, dual lumen, single cannula flow can be limited by adequate inflow, requiring the need for an additional inflow cannula to meet patient demands. This cannula configuration may result in differential flows in the inflow and outflow limbs and altered flow dynamics, increasing the risk of intracannula thrombus. We describe a series of four patients treated with oxy-RVAD for COVID-19-associated respiratory failure complicated by dual lumen ProtekDuo intracannula thrombus.

Successful treatment of veno-arterial extracorporeal membrane oxygenation complicated with left ventricular thrombus by intravenous thrombolysis: A case report

BACKGROUND

Left ventricular thrombus is a rare condition, for which appropriate treatments are not extensively studied. Although it can be treated by thrombectomy, such surgery can be difficult and risky, and not every patient can tolerate the surgery.

CASE SUMMARY

We report a case of a middle-aged man receiving veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for acute myocardial infarction who developed left ventricular thrombus despite systemic anticoagulation. After systemic thrombolysis with urokinase, the left ventricular thrombus disappeared, ECMO was successfully withdrawn 9 days later, and the patient recovered and was discharged from hospital.

CONCLUSION

Systemic thrombolysis is a treatment option for left ventricular thrombus in addition to anticoagulation and thrombectomy.

New intra-conduit thrombus detected using transesophageal echocardiography immediately after weaning from cardiopulmonary bypass during the Fontan procedure: a case report

This study reports a case wherein a new thrombus was detected by transesophageal echocardiography in the conduit during extracardiac conduit Fontan procedure. Immediately after weaning from the cardiopulmonary bypass and administration of protamine, a thrombus was noted in the conduit by transesophageal echocardiography. Since the patient was hemodynamically stable, anticoagulation therapy was initiated after admission to the intensive care unit. One week post-surgery, imaging results showed residual thrombus, but the patient was safely discharged. Even during Fontan procedure, careful observation with transesophageal echocardiography is important because of the possibility of thrombus formation in the conduit.

Temporary Mechanical Circulatory Support: Left, Right, and Biventricular Devices

Temporary mechanical circulatory support (MCS) encompasses a wide array of invasive devices, which provide short-term hemodynamic support for multiple clinical indications. Although initially developed for the management of cardiogenic shock, indications for MCS have expanded to include prophylactic insertion prior to high-risk percutaneous coronary intervention, treatment of acute circulatory failure following cardiac surgery, and bridging of end-stage heart failure patients to more definitive therapies, such as left ventricular assist devices and cardiac transplantation. A wide variety of devices are available to provide left ventricular, right ventricular, or biventricular support. The choice of a temporary MCS device requires consideration of the clinical scenario, patient characteristics, institution protocols, and provider familiarity and training. In this review, the most common forms of left, right, and biventricular temporary MCS are discussed, along with their indications, contraindications, complications, cannulations, hemodynamic effects, and available clinical data.

ECMO in Cardiac Arrest: A Narrative Review of the Literature

Cardiac arrest (CA) is a frequent cause of death and a major public health issue. To date, conventional cardiopulmonary resuscitation (CPR) is the only efficient method of resuscitation available that positively impacts prognosis. Extracorporeal membrane oxygenation (ECMO) is a complex and costly technique that requires technical expertise. It is not considered standard of care in all hospitals and should be applied only in high-volume facilities. ECMO combined with CPR is known as ECPR (extracorporeal cardiopulmonary resuscitation) and permits hemodynamic and respiratory stabilization of patients with CA refractory to conventional CPR. This technique allows the parallel treatment of the underlying etiology of CA while maintaining organ perfusion. However, current evidence does not support the routine use of ECPR in all patients with refractory CA. Therefore, an appropriate selection of patients who may benefit from this procedure is key. Reducing the duration of low blood flow by means of performing high-quality CPR and promoting access to ECPR, may improve the survival rate of the patients presenting with refractory CA. Indeed, patients who benefit from ECPR seem to carry better neurological outcomes. The aim of this present narrative review is to present the most recent literature available on ECPR and to clarify its potential therapeutic role, as well as to provide an in-depth explanation of equipment and its set up, the patient selection process, and the patient management post-ECPR.

Prognostic Impact of Active Mechanical Circulatory Support in Cardiogenic Shock Complicating Acute Myocardial Infarction, Results from the Culprit-Shock Trial

OBJECTIVES

To analyze the use and prognostic impact of active mechanical circulatory support (MCS) devices in a large prospective contemporary cohort of patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI).

BACKGROUND

Although increasingly used in clinical practice, data on the efficacy and safety of active MCS devices in patients with CS complicating AMI are limited.

METHODS

This is a predefined subanalysis of the CULPRIT-SHOCK randomized trial and prospective registry. Patients with CS, AMI and multivessel coronary artery disease were categorized in two groups: (1) use of at least one active MCS device vs. (2) no active MCS or use of intra-aortic balloon pump (IABP) only. The primary endpoint was a composite of all-cause death or renal replacement therapy at 30 days.

RESULTS

Two hundred of 1055 (19%) patients received at least one active MCS device (n = 112 Impella^®; n = 95 extracorporeal membrane oxygenation (ECMO); n = 6 other devices). The primary endpoint occurred significantly more often in patients treated with active MCS devices compared with those without active MCS devices (142 of 197, 72% vs. 374 of 827, 45%; p < 0.001). All-cause mortality and bleeding rates were significantly higher in the active MCS group (all p < 0.001). After multivariable adjustment, the use of active MCS was significantly associated with the primary endpoint (odds ratio (OR) 4.0, 95% confidence interval (CI) 2.7-5.9; p < 0.001).

CONCLUSIONS

In the CULPRIT-SHOCK trial, active MCS devices were used in approximately one fifth of patients. Patients treated with active MCS devices showed worse outcome at 30 days and 1 year.

Application of goal-directed therapy for the use of concentrated antithrombin for heparin resistance during cardiac surgery

The maintenance of anticoagulation in adult patients undergoing cardiopulmonary bypass is dependent upon a number of factors, including heparin concentration and adequate antithrombin activity. Inadequate anticoagulation increases the risk of thrombosis and jeopardizes both vascular and extracorporeal circuit integrity. The purpose of this study was to evaluate a goal-directed approach for the use of antithrombin in patients who were resistant to heparin. Following institutional review board approval, data were obtained from quality improvement records. A goal-directed protocol for antithrombin was established based upon heparin dosing (400 IU kg^-1 body weight) and achieving an activated clotting time of ⩾500 seconds prior to cardiopulmonary bypass. Two groups of patients were identified as those receiving antithrombin and those not receiving antithrombin. Outcome measures included activated clotting time values and transfusion rates. Consecutive patients (n = 140) were included in the study with 10 (7.1%) in the antithrombin group. The average antithrombin dose was 1,029.0 ± 164.5 IU and all patients had restoration to the activated clotting time levels. Patients in the antithrombin group were on preoperative heparin therapy (80.0% vs. 24.6%, p = 0.001). Prior to cardiopulmonary bypass the activated clotting time values were lower in the antithrombin group (417.7 ± 56.1 seconds vs. 581.1 ± 169.8 seconds, p = 0.003). Antithrombin patients had a lower heparin sensitivity index (0.55 ± 0.17 vs. 1.05 ± 0.44 seconds heparin^-1 IU kg^-1, p = 0.001), received more total heparin (961.3 ± 158.5 IU kg^-1 vs. 677.5 ± 199.0 IU kg^-1, p = 0.001), more cardiopulmonary bypass heparin (22,500 ± 10,300 IU vs. 12,100 ± 13,200 IU, p = 0.016), and more protamine (5.4 ± 1.2 vs. 4.1 ± 1.1 mg kg^-1, p = 0.003). The intraoperative transfusion rate was higher in the antithrombin group (70.0% vs. 35.4%, p = 0.035), but no differences were seen postoperatively. Utilization of a goal-directed algorithm for the administration of antithrombin for the treatment of heparin resistance is effective in patients undergoing cardiac surgery.

Simultaneous Venoarterial Extracorporeal Membrane Oxygenation and Percutaneous Left Ventricular Decompression Therapy with Impella Is Associated with Improved Outcomes in Refractory Cardiogenic Shock

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been used for refractory cardiogenic shock; however, it is associated with increased left ventricular afterload. Outcomes associated with the combination of a percutaneous left ventricular assist device (Impella) and VA-ECMO remains largely unknown. We retrospectively reviewed patients treated for refractory cardiogenic shock with VA-ECMO (2014-2016). The primary outcome was all-cause mortality within 30 days of VA-ECMO implantation. Secondary outcomes included duration of support, stroke, major bleeding, hemolysis, inotropic score, and cardiac recovery. Outcomes were compared between the VA-ECMO cohort and VA-ECMO + Impella (ECPELLA cohort). Sixty-six patients were identified: 36 VA-ECMO and 30 ECPELLA. Fifty-eight percent of VA-ECMO patients (n = 21) had surgical venting, as compared to 100% of the ECPELLA cohort (n = 30) which had Impella (±surgical vent). Both cohorts demonstrated relatively similar baseline characteristics except for higher incidence of ST-elevation myocardial infarction (STEMI) and percutaneous coronary intervention (PCI) in the ECPELLA cohort. Thirty-day all-cause mortality was significantly lower in the ECPELLA cohort (57% vs. 78%; hazard ratio [HR] 0.51 [0.28-0.94], log rank p = 0.02), and this difference remained intact after correcting for STEMI and PCI. No difference between secondary outcomes was observed, except for the inotrope score which was greater in VA-ECMO group by day 2 (11 vs. 0; p = 0.001). In the largest US-based retrospective study, the addition of Impella to VA-ECMO for patients with refractory cardiogenic shock was associated with lower all-cause 30 day mortality, lower inotrope use, and comparable safety profiles as compared with VA-ECMO alone.

An urgent open surgical approach for left ventricle venting during peripheral veno-arterial extracorporeal membrane oxygenation for refractory cardiac arrest: case report

The objective of the study is to describe an emergency procedure for left ventricle venting during veno-arterial extracorporeal life support for refractory cardiac arrest. Veno-arterial extracorporeal membrane oxygenation is widely used in refractory cardiac arrest but is characterized by an increase in left ventricle afterload, which may impair cardiac contractility improvement. Different left ventricle venting techniques are available. We report the use of a surgical approach with sternotomy for left ventricle venting in a 21-year-old patient who was placed under veno-arterial extracorporeal membrane oxygenation for refractory cardiac arrest with severe pulmonary edema, respiratory failure, and left ventricle stasis. A 21-year-old woman was admitted for laparoscopic sleeve gastrectomy. In the recovery room, she developed a refractory circulatory shock. Transthoracic echocardiography revealed a dilated cardiomyopathy with severe left ventricle systolic dysfunction (left ventricle ejection fraction at 20%). Coronary angiogram was normal. On day 2, she underwent laparotomy for sepsis and she presented cardiac arrest secondary to ventricular tachycardia. We proceeded to peripheral veno-arterial extracorporeal membrane oxygenation as the cardiac arrest was refractory. A miniaturized veno-arterial extracorporeal membrane oxygenation system was implanted into the right femoral vessels onsite .The low flow duration was 40 minutes. Veno-arterial extracorporeal membrane oxygenation blood flow was set to 3 L min^-1, resulting in a closed aortic valve and a massive pulmonary edema. Transesophageal echocardiography showed left ventricular ejection fraction at 5% without aortic valve opening. We first implanted an intra-aortic balloon pump without clinical improvement. Transesophageal echocardiography revealed massive thrombus formation into the aortic root. We decided to perform an open surgical approach for left ventricle unload using a transmitral cannula (22 Fr) via the right superior pulmonary vein connected to the inflow tube of the veno-arterial extracorporeal membrane oxygenation with Y connection. Transesophageal echocardiography showed a full opening of aortic valve and elimination of valve aortic thrombus. Chest radiography showed a significant decrease of pulmonary congestion. We were able to withdraw extracorporeal life support organization on day 10 and discharged on day 54. Clinical explorations reveal a fulminant rocuronium-related hypersensitivity myocarditis. This salvage surgical technique using a modified central veno-arterial extracorporeal membrane oxygenation cannulation technique has efficiently decreased blood stasis and permitted rapid recovery.

Prohemostatic Activity of Factor X in Combination With Activated Factor VII in Dilutional Coagulopathy

BACKGROUND

Recombinant activated factor VII (rFVIIa) concentrate reduces allogeneic blood transfusions, but it may increase thromboembolic complications in complex cardiac surgery. The mixture of activated factor VII (FVIIa) and factor X (FX) (FVIIa/FX) (FVIIa:FX = 1:10) is a novel bypassing agent for hemophilia patients. We hypothesized that the combination of FX and FVIIa could improve thrombin generation (TG) in acquired multifactorial coagulation defects such as seen in cardiac surgery and conducted in vitro evaluation of FVIIa/FX in parallel with other coagulation factor concentrates using in vitro and in vivo diluted plasma samples.

METHODS

Plasma samples were collected from 9 healthy volunteers and 12 cardiac surgical patients. We measured TG (Thrombinoscope) using in vitro 50% dilution plasma and in vivo dilution plasma after cardiopulmonary bypass, in parallel with thromboelastometry (ROTEM) and standard coagulation assays. In vitro additions of FVIIa/FX (0.35, 0.7, and 1.4 μg/mL, based on the FVIIa level), rFVIIa (1.4, 2.8, and 6.4 μg/mL), prothrombin complex concentrate (0.3 international unit), and 20% plasma replacement were evaluated.

RESULTS

In diluted plasma, the addition of either FVIIa/FX or rFVIIa shortened the lag time and increased the peak TG, but the effect in lag time of FVIIa/FX at 0.35 μg/mL was more extensive than rFVIIa at 6.4 μg/mL. Prothrombin complex concentrate increased peak TG by increasing the prothrombin level but failed to shorten the lag time. No improvement in any of the TG variables was observed after 20% volume replacement with plasma. The addition of factor concentrates normalized prothrombin time/international normalized ratio but not with plasma replacement. In cardiac patients, similar patterns were observed on TG in post-cardiopulmonary bypass samples. FVIIa/FX shortened clotting time (CT) in a concentration-dependent manner on CT on thromboelastometry. Plasma replacement did not improve CT, but a combination of plasma and FVIIa/FX (0.35 μg/mL) more effectively shortened CT than FVIIa/FX alone.

CONCLUSIONS

The combination of FVIIa and FX improved TG more efficiently than rFVIIa alone or plasma in dilutional coagulopathy models. The required FVIIa dose in FVIIa/FX was considerably lower than those reported during bypassing therapy in hemophilia patients (1.4-2.8 μg/mL). The combination of plasma could restore coagulation more efficiently compared to FVIIa/FX alone. Lesser FVIIa requirement to exert procoagulant activity may be favorable in terms of reducing systemic thromboembolic complications.

Ipsilateral pulmonary infarction after major lung resection

Background

Lung infarction is a rare complication of lung resection, developing mainly because of technical errors. In some cases, a specific reason cannot be identified. This study aimed to investigate the occurrence, characteristics, and outcome of this pathology in a series of patients.

Methods

The medical records of patients who underwent reoperation for lung infarction without an apparent cause (based on imaging, reoperation findings, and histopathology) after major lung resection at our institution from 2006 to 2015, were investigated.

Results

Seven patients were identified. The mean age was 62.2 years (range 51–75 years), and 5 were male. Copious dissection or adverse events during surgery were recorded in all but 2 cases. The main presenting symptom was unsettling frank hemoptysis (4 cases) with a variable time of onset of symptoms (4–164 h). All reoperations necessitated further lung resection (4 patients had a further lobectomy and 3 had a completion pneumonectomy). During reoperation, all vessels and bronchi were intact. No apparent cause of infarction could be identified according to the histopathology report. Morbidity after reoperation was atrial fibrillation in 3 cases and bronchopleural fistula in 2, one of which required a transsternal pneumonectomy and this was the only mortality. Length of stay ranged from 8 to 90 days.

Conclusion

Ipsilateral lung infarction after lobectomy is a rare complication and the reason may not be identifiable. Treatment usually requires reoperation. Extensive manipulation or adverse events during surgery could induce this rare complication.

Peripheral VA-ECMO with direct biventricular decompression for refractory cardiogenic shock

Cardiogenic shock and cardiac arrest are life-threatening emergencies that result in high mortality rates. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) via peripheral cannulation is an option for patients who do not respond to conventional therapies. Left ventricular (LV) distention is a major limitation with peripheral VA-ECMO and is thought to contribute to poor recovery and the inability to wean off VA-ECMO. We report on a novel technique that combines peripheral VA-ECMO with off-pump insertion of a trans-apical LV venting cannula and a right ventricular decompression cannula.

Effects of nanotopography on the in vitro hemocompatibility of nanocrystalline diamond coatings

Nanocrystalline diamond (NCD) coatings have been investigated for improved wear resistance and enhanced hemocompatibility of cardiovascular devices. The goal of this study was to evaluate the effects of NCD surface nanotopography on in vitro hemocompatibility. NCD coatings with small (NCD-S) and large (NCD-L) grain sizes were deposited using microwave plasma chemical vapor deposition and characterized using scanning electron microscopy, atomic force microscopy, contact angle testing, and Raman spectroscopy. NCD-S coatings exhibited average grain sizes of 50-80 nm (RMS 5.8 nm), while NCD-L coatings exhibited average grain sizes of 200-280 nm (RMS 23.1 nm). In vitro hemocompatibility testing using human blood included protein adsorption, hemolysis, nonactivated partial thromboplastin time, platelet adhesion, and platelet activation. Both NCD coatings demonstrated low protein adsorption, a nonhemolytic response, and minimal activation of the plasma coagulation cascade. Furthermore, the NCD coatings exhibited low thrombogenicity with minimal platelet adhesion and aggregation, and similar morphological changes to surface-bound platelets (i.e., activation) in comparison to the HDPE negative control material. For all assays, there were no significant differences in the blood-material interactions of NCD-S versus NCD-L. The two tested NCD coatings, regardless of nanotopography, had similar hemocompatibility profiles compared to the negative control material (HDPE) and should be further evaluated for use in blood-contacting medical devices. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 253-264, 2017.

Novel approaches in management of perioperative coagulopathy

PURPOSE OF REVIEW

The recent advances in hemostatic monitoring, and discussion of the clinical implications of hemostatic therapies based on different blood components and factor concentrates.

RECENT FINDINGS

Implementing suitable laboratory tests and transfusion protocols is highly recommended because the laboratory test guided, protocol-driven transfusion approach reduces blood component utilization, and possibly leads to improved outcomes. Timely assessment of coagulation has been difficult using conventional coagulation tests, but thrombocytopenia, fibrin polymerization defects, and fibrinolysis can be quickly assessed on thromboelastometry. The latter testing can be applied to guide the dosing of fibrinogen and prothrombin complex concentrate, which are selectively used to correct fibrinogen deficiency, and improve thrombin generation in acquired coagulopathy. These therapeutic approaches are novel, and potentially effective in reducing the exposure to allogeneic components (e.g., plasma and platelets) and side-effects of transfusion. Although the accessibility of different therapies among different countries, tranexamic acid is widely available, and is an effective blood conservation measure with a good safety profile in various surgical settings.

SUMMARY

Our understanding of perioperative coagulopathy, diagnostic tools, and therapeutic approaches has evolved in recent years. Additional multidisciplinary efforts are required to understand the optimal combinations, cost-effectiveness, and safety profiles of allogeneic components, and available factor concentrates.

Impella to unload the left ventricle during peripheral extracorporeal membrane oxygenation

Peripheral venoarterial extracorporeal membrane oxygenation (VA ECMO) for acute cardiac failure reestablishes normal oxygen delivery and perfusion. However, VA ECMO can be limited by insufficient ventricular unloading, resulting in thrombus formation and pulmonary edema. Impella 2.5 has been used to unload the left ventricle and provide hemodynamic support during acute heart failure. We present our experience of the Impella 2.5 as an adjunct for left ventricular unloading during peripheral VA ECMO support and as a bridge for the HeartMate II left ventricular assist device (LVAD). An Impella 2.5 was placed in patients who were on peripheral VA ECMO with evidence of left ventricular distension. Patients who were candidates for heart transplant were transitioned to the HeartMate II LVAD. Five patients on VA ECMO with ventricular distension underwent Impella 2.5 implantation, resulting in a decreased left ventricular end-diastolic diameter as measured by echocardiography (7.8 ± 1.4 vs. 6.2 ± 0.8 cm, p = 0.001). Four patients were subsequently transitioned to the HeartMate II LVAD after restoration of end-organ function. Impella 2.5 is a safe means to unload the left ventricle while on peripheral VA ECMO to prevent left ventricle thrombus formation and worsening pulmonary edema in patients transitioning to a HeartMate II LVAD.

Incidence of inferior vena cava thrombosis detected by transthoracic echocardiography in the immediate postoperative period after adult cardiac and general surgery

Venous thromboembolism is an important complication after general and cardiac surgery. Using transthoracic echocardiography, this study assessed the incidence of inferior vena cava (IVC) thrombosis among a total of 395 and 289 cardiac surgical and major surgical patients in the immediate postoperative period after cardiac and major surgery, respectively. All transthoracic echocardiography was performed by a specialist intensivist within 24 hours after surgery with special emphasis on using the subcostal view in the supine position to visualise the IVC. Of the 395 cardiac surgical patients studied, the IVC was successfully visualised using the subcostal view in 315 patients (79.8%) and eight of these patients (2.5%) had a partially obstructive thrombosis in the IVC. In 250 out of 289 (85%) general surgical patients, the IVC was also clearly visualised, but only one patient (0.4%) had an IVC thrombosis (2.5 vs 0.4%, P <0.05). In summary, visualisation of the IVC was feasible in most patients in the immediate postoperative period after both adult cardiac and major surgery. IVC thrombosis appeared to be more common after adult cardiac surgery than general surgery. A large prospective cohort study is needed to define the risk factors for IVC thrombus and whether early thromboprophylaxis can reduce the incidence of IVC thrombus after adult cardiac surgery.

In vitro shear stress-induced platelet activation: sensitivity of human and bovine blood

As platelet activation plays a critical role in physiological hemostasis and pathological thrombosis, it is important in the overall hemocompatibility evaluation of new medical devices and biomaterials to assess their effects on platelet function. However, there are currently no widely accepted in vitro test methods to perform this assessment. In an effort to develop effective platelet tests for potential use in medical device evaluation, this study compared the sensitivity of platelet responses to shear stress stimulation of human and bovine blood using multiple platelet activation markers. Fresh whole blood samples anticoagulated with heparin or anticoagulant citrate dextrose, solution A (ACDA) were exposed to shear stresses up to 40 Pa for 2 min using a cone-and-plate rheometer model. Platelet activation was characterized by platelet counts, platelet surface P-selectin expression, and serotonin release into blood plasma. The results indicated that exposure to shear stresses above 20 Pa caused significant changes in all three of the platelet markers for human blood and that the changes were usually greater with ACDA anticoagulation than with heparin. In contrast, for bovine blood, the markers did not change with shear stress stimulation except for plasma serotonin in heparin anticoagulated blood. The differences observed between human and bovine platelet responses suggest that the value of using bovine blood for in vitro platelet testing to evaluate devices may be limited.