Pulmonary Embolism in the Critically Ill

Peripherally inserted central catheter (PICC)-related thrombosis in critically ill patients

BACKGROUND

Peripherally inserted central catheters (PICC) are being increasingly used in critical care setting. However, PICCs are associated with a number of complications, particularly upper extremity venous thrombosis (UEVT), leading to post-thrombotic syndrome, pulmonary embolism and increased risk of catheter-related infection.

OBJECTIVE

To review the literature surrounding PICCs and highlight the epidemiology, pathophysiology, diagnosis and management of PICC-related thrombosis in critically ill patients.

DATA SOURCES AND EXTRACTION

We performed an electronic literature search of the databases PubMed, EMBASE and Google scholar using set search terms, from their commencement date to the end of January 2014.

SUMMARY OF REVIEW

It has been shown that PICCs may double the risk of deep venous thrombosis compared with centrally inserted venous catheters, in critically ill patients. However, the incidence of PICC-related thrombosis in critically ill patients has not been quantified. Ultrasonography is the preferred diagnostic imaging modality. There are no randomized controlled trials (RCTs) on the best treatment of PICC-related thrombosis in the intensive care unit (ICU) setting and in most cohort studies, anticoagulation strategies with or without PICC removal have been used.

CONCLUSIONS

Decision to insert a PICC should be taken after careful risk stratification. There is lack of high-quality evidence assessing prevention strategies and management of PICC-related thrombosis in the ICU. Well-designed RCTs are required to estimate the prevalence of UEVT in ICU patients with PICCs and evaluate the efficacy and magnitude of clinical benefit and cost-effectiveness of therapeutic strategies.

Pulmonary Embolism in the Mechanically-Ventilated Critically Ill Patient: Is it Different?

Pulmonary embolism (PE) confers significant in-hospital morbidity and mortality, and critically ill patients remain at risk for venous thromboembolism despite thromboprophylaxis. Recognition of the clinical manifestations and immediate management of PE are of paramount importance. Despite diagnostic advances, PE is often undiagnosed and untreated in patients receiving mechanical ventilation, as these patients do not exhibit the common clinical features of the condition, making the diagnosis very challenging. Computed tomographic pulmonary angiography is probably the reference standard for the diagnosis of acute PE in the haemodynamically stable, ventilated patient. In the setting of circulatory collapse, bedside echocardiography may be used to risk stratify these patients, based on the presence or absence of right ventricular dysfunction, and guide further management. Treatment options include anticoagulation alone, anticoagulation plus thrombolysis, surgical or catheter embolectomy. Inotropes, vasopressors and pulmonary artery vasodilators may be considered after initial resuscitation of the right ventricle. Few studies have focused on estimating the prevalence of PE among mechanically-ventilated intensive care unit (ICU) patients and there is notable lack of data assessing predictive factors, prevention, diagnostic strategy and management of PE in the ICU setting.

Acute lung failure

Lung failure is the most common organ failure seen in the intensive care unit. The pathogenesis of acute respiratory failure (ARF) can be classified as (1) neuromuscular in origin, (2) secondary to acute and chronic obstructive airway diseases, (3) alveolar processes such as cardiogenic and noncardiogenic pulmonary edema and pneumonia, and (4) vascular diseases such as acute or chronic pulmonary embolism. This article reviews the more common causes of ARF from each group, including the pathological mechanisms and the principles of critical care management, focusing on the supportive, specific, and adjunctive therapies for each condition.

Diagnosis and management of life-threatening pulmonary embolism

Pulmonary embolus (PE) is estimated to cause 200 000 to 300 000 deaths annually. Many deaths occur in hemodynamically unstable patients and the estimated mortality for inpatients with hemodynamic instability is between 15% and 25%. The diagnosis of PE in the critically ill is often challenging because the presentation is nonspecific. Computed tomographic pulmonary angiography appears to be the most useful study for diagnosis of PE in the critically ill. For patients with renal insufficiency and contrast allergy, the ventilation perfusion scan provides an alternative. For patients too unstable to travel, echocardiography (especially transesophageal echocardiography) is another option. A positive result on lower extremity Doppler ultrasound can also aid in the decision to treat. The choice of treatment in PE depends on the estimated risk of poor outcome. The presence of hypotension is the most significant predictor of poor outcome and defines those with massive PE. Normotensive patients with evidence of right ventricular (RV) dysfunction, as assessed by echocardiography, comprise the sub-massive category and are at intermediate risk of poor outcomes. Clinically, those with sub-massive PE are difficult to distinguish from those with low-risk PE. Cardiac troponin, brain natriuretic peptide, and computed tomographic pulmonary angiography can raise the suspicion that a patient has sub-massive PE, but the echocardiogram remains the primary means of identifying RV dysfunction. The initial therapy for patients with PE is anticoagulation. Use of vasopressors, inotropes, pulmonary artery (PA) vasodilators and mechanical ventilation can stabilize critically ill patients. The recommended definitive treatment for patients with massive PE is thrombolysis (in addition to anticoagulation). In massive PE, thrombolytics reduce the risk of recurrent PE, cause rapid improvement in hemodynamics, and probably reduce mortality compared with anticoagulation alone. For patients with a contraindication to anticoagulation and thrombolytic therapy, surgical embolectomy and catheter-based therapies are options. Thrombolytic therapy in sub-massive PE results in improved pulmonary perfusion, reduced PA pressures, and a less complicated hospital course. No survival benefit has been documented, however. If one is considering the use of thrombolytic therapy in sub-massive PE, the limited documented benefit must be weighed against the increased risk of life-threatening hemorrhage. The role of surgical embolectomy and catheter-based therapies in this population is unclear. Evidence suggests that sub-massive PE is a heterogeneous group with respect to risk. It is possible that those at highest risk may benefit from thrombolysis, but existing studies do not identify subgroups within the sub-massive category. The role of inferior vena cava (IVC) filters, catheter-based interventions, and surgical embolectomy in life-threatening PE has yet to be completely defined.

Pulmonary embolism in critically ill patients receiving antithrombotic prophylaxis: a clinical-pathologic study

PURPOSE

The true incidence of pulmonary embolism (PE) in critically ill adult patients receiving antithrombotic prophylaxis is unknown, as well as the impact on the outcome. The aim of this study was to assess the incidence of PE in a surgical and medical intensive care unit and to evaluate the presence of risk factors that could be helpful in identifying patients at higher risk of missed diagnosis.

MATERIALS AND METHODS

We retrospectively reviewed the autopsies and clinical data of all patients who died in our intensive care unit from 1996 to 2007. All patients received prophylaxis with subcutaneous low-molecular weight heparin.

RESULTS

Among the 600 autopsies, the clinical diagnosis of PE was confirmed in 13 patients (true positives) and not confirmed in 20 patients; in 73 patients, the PE was discovered only at the autopsy (false negatives [FNs]). The overall incidence of PE in our patients was 14.3%. Pulmonary embolism was considered the cause of death in 45% of FNs and 77% of true positives. Among all comorbidities, only a recent abdominal surgery and the presence of acute renal failure were associated with a higher risk of missed diagnosis. In the FN group, there was a significantly higher frequency of cases of septic shock.

CONCLUSIONS

Despite thromboprophylaxis, critically ill patients remain at risk for PE; and because of the difficulty in diagnosing it clinically, the death certificate diagnosis of PE underestimates the problem.

Assessment of right ventricular function in acute pulmonary embolism using ECG-synchronized MDCT

OBJECTIVE

The purpose of this article is to determine the independent predictors of right ventricular (RV) dysfunction in patients with acute pulmonary embolism (PE) and to assess the relationship between RV ejection fraction (EF) and PE load.

SUBJECTS AND METHODS

Breath-hold CT of the chest was performed for 64 patients with PE (33 men and 31 women; mean [± SD] age, 58.6 ± 16.5 years). In addition, ECG-synchronized cardiac CT was performed to determine the RV and left ventricular (LV) EFs. PE load was determined using the Qanadli obstruction index. Multivariable regression analysis was performed to determine independent predictors of RV dysfunction (defined as EF < 35%). In addition, the relationship between RV EF and PE load was assessed by receiver operating characteristic (ROC) curves.

RESULTS

RV dysfunction was independently predicted by a PE load greater than 50% (odds ratio, 40.17; 95% CI, 4.22-382.67) and an LV EF less than 45% (odds ratio, 31.18; 95% CI, 2.00-487.09; p < 0.05 for both). Curve analysis revealed that a PE load greater than 50% had a sensitivity of 82% and a specificity of 85% to identify an RV EF less than 35%. Conversely, an RV EF less than 35% had a sensitivity of 93% and a specificity of 67% to predict a PE load greater than 50%.

CONCLUSION

RV dysfunction (defined as RV EF < 35%) in patients with acute PE is highly sensitive to define a PE load greater than 50%. Furthermore, RV dysfunction is independently predicted by an obstruction index greater than 50% or an LV EF less than 45%. Assessment of RV function by ECG-synchronized CT may become useful for guiding therapy.

Acute respiratory failure in the patient with cancer: diagnostic and management strategies

Acute respiratory failure (ARF) remains the major reason for admission to the intensive care unit (ICU) in patients with cancer and is often associated with high mortality, especially in those who require mechanical ventilation. The diagnosis and management of ARF in patients who have cancer pose unique challenges to the intensivist. This article reviews the most common causes of ARF in patients with cancer and discusses recent advances in the diagnostic and management approaches of these disorders. Timely diagnosis and treatment of reversible causes of respiratory failure, including earlier use of noninvasive ventilation and judicious ventilator and fluid management in patients with acute lung injury, are essential to achieve an optimal outcome. Close collaboration between oncologists and intensivists helps ensure that clear goals, including direction of treatment and quality of life, are established for every patient with cancer who requires mechanical ventilation for ARF.

[Pulmonary embolism]

The annual incidence of pulmonary embolism (PE) in western industrial nations is about 1 to 1.5 cases per 1,000 citizens. For the prognosis of the patients it is important to consider PE early as a differential diagnosis. The clinical disorders are non-specific and varied. The most frequent clinical signs of PE are dyspnoea, tachypnoea, tachycardia and chest pain. Diagnostic algorithms are available for the diagnosis of PE. There is a cardinal difference in diagnostic procedure between clinically stable and instable patients. The criteria for stability are mainly hemodynamic values. In hemodynamically instable patients echocardiography is the most important diagnostic tool. Therapeutical goals depend on the severity of PE and include hemodynamic stabilisation, prevention of the growth of the thrombus, recanalisation of pulmonal arterial vessels, removal of hypoxemia, and prophylaxis of recurrence. Anticoagulation is the only therapy of choice in stable patient of risk classification I. Interventions like thrombolysis and embolectomy are mainly indicated in hemodynamically instable patients.