Bedside clinical and ultrasound-based approaches to the management of hemodynamic instability--part I: focus on the clinical approach: continuing professional development

New Developments in Continuous Hemodynamic Monitoring of the Critically Ill Patient

Hemodynamic monitoring is a cornerstone in the assessment of patients with circulatory shock. Timely recognition of hemodynamic compromise and proper optimisation is essential to ensure adequate tissue perfusion and maintain renal, hepatic, abdominal, and cerebral functions. Hemodynamic monitoring has significantly evolved since the first inception of the pulmonary artery catheter more than 50 years ago. Bedside echocardiography, when combined with noninvasive and minimally invasive technologies, provides tools to monitor and quantify the cardiac output to promptly react and improve hemodynamic management in an acute care setting. Commonly used technologies include noninvasive pulse-wave analysis, pulse-wave transit time, thoracic bioimpedance and bioreactance, esophageal Doppler, minimally invasive pulse-wave analysis, transpulmonary thermodilution, and pulmonary artery catheter. These monitoring strategies are reviewed here, along with detailed analysis of their operating mode, particularities, and limitations. The use of artificial intelligence to enhance performance and effectiveness of hemodynamic monitoring is reviewed to apprehend future possibilities.

Whole body ultrasound in the operating room and intensive care unit

Whole body ultrasound can be used to improve the speed and accuracy of evaluation of an increasing number of organ systems in the critically ill. Cardiac and abdominal ultrasound can be used to identify the mechanisms and etiology of hemodynamic instability. In hypoxemia or hypercarbia, lung ultrasound can rapidly identify the etiology of the condition with an accuracy that is equivalent to that of computed tomography. For encephalopathy, ocular ultrasound and transcranial Doppler can identify elevated intracranial pressure and midline shift. Renal and bladder ultrasound can identify the mechanisms and etiology of renal failure. Ultrasound can also improve the accuracy and safety of percutaneous procedures and should be currently used routinely for central vein catheterization and percutaneous tracheostomy.

Synopsis of the point-of-care ultrasound assessment for perioperative emergencies

This module will introduce the concept of a point-of-care ultrasound (POCUS) examination for perioperative clinicians. A focused cardiac examination of ventricular filling and function is presented. An examination of the inferior vena cava is also reviewed as a tool to assess volume status. Finally, a brief examination of the lung and pleura is explored to aid the clinician in situations of patient hypoxia and difficult ventilation. Limited ultrasound cardiorespiratory examinations can be performed by non-cardiologists and non-radiologists. Information drawn from POCUS may aid in diagnosis and early rescue in perioperative care. Point-of-care ultrasound is likely to become standard of care for anesthesiologists in the same way that stethoscopy is presently.

The Role of Point-of-Care Ultrasound Monitoring in Cardiac Surgical Patients With Acute Kidney Injury

The approach to the patient with acute kidney injury (AKI) after cardiac surgery involves multiple aspects. These include the rapid recognition of reversible causes, the accurate identification of patients who will progress to severe stages of AKI, and the subsequent management of complications resulting from severe renal dysfunction. Unfortunately, the inherent limitations of physical examination and laboratory parameter results are often responsible for suboptimal clinical management. In this review article, the authors explore how point-of-care ultrasound, including renal and extrarenal ultrasound, can be used to complement all aspects of the care of cardiac surgery patients with AKI, from the initial approach of early AKI to fluid balance management during renal replacement therapy. The current evidence is reviewed, including knowledge gaps and future areas of research.

Ultrasound findings in critical care patients: the "liver sign" and other abnormal abdominal air patterns

In critical care patients, point of care abdominal ultrasound examination, although it has been practiced for over 30 years, is not as widespread as its cardiac or pulmonary counterparts. We report two cases in which detection of air during abdominal ultrasound allowed the early detection of life-threatening pathologies. In the first case, a patient with severe Clostridium difficile was found to have portal venous gas but its significance was confounded by a recent surgery. Serial ultrasonographic exams triggered a surgical intervention. In the second case, we report what we call the "liver sign" a finding in patients with pneumoperitoneum. These findings, all obtained prior to conventional abdominal imaging, had immediate clinical impact and avoided unnecessary delays and radiation. Detection of abdominal air should be part of the routine-focused ultrasonographic exam and for critically ill patients an algorithm is proposed.

Extracardiac Signs of Fluid Overload in the Critically Ill Cardiac Patient: A Focused Evaluation Using Bedside Ultrasound

Fluid balance management is of great importance in the critically ill cardiac patient. Although intravenous fluids are a cornerstone therapy in the management of unstable patients, excessive administration coupled with cardiac dysfunction leads to elevation in central venous pressure and end-organ venous congestion. Fluid overload is known to have a detrimental effect on organ function and is responsible for significant morbidity in critically ill patients. Multisystem bedside point of care ultrasound imaging can be used to assess signs of fluid overload and venous congestion in critically ill patients. In this review we describe the ultrasonographic extracardiac signs of fluid overload and how they can be used to complement clinical evaluation to individualize patient management.

Right Ventricular Depression After Cardiopulmonary Bypass for Valvular Surgery

OBJECTIVE

To assess if right ventricular (RV) dysfunction is associated with increased mortality after cardiac surgery.

DESIGN

Post-hoc analysis of a single-center double-blind randomized controlled trial.

SETTING

University hospital.

PARTICIPANTS

A total of 120 patients undergoing simple or complex valvular surgery.

INTERVENTIONS

Patients were randomized to receive intravenous amiodarone or placebo intraoperatively. As secondary analysis, patients were divided into those requiring or not requiring postoperative inotropic agents.

MEASUREMENTS AND MAIN RESULTS

After cardiopulmonary bypass (CPB), there were significant increases in heart rate, cardiac index, systolic and mean arterial pressures, central venous pressure and pulmonary capillary wedge pressure with reduction in systemic vascular resistance (p<0.05). Right ventricular end-systolic area became larger in those without inotropes and tricuspid annular plane systolic excursion was reduced in all patients; mitral annular systolic velocities were higher in patients receiving inotropes. Both right- and left-sided Doppler signals were altered significantly after CPB, which may be attributed to increased filling pressure. Inotropic agents were required in 56 patients after CPB (47%). The use of inotropic agents was associated with increased left and right atrial velocities (p<0.05). There were no differences in postoperative complications between groups; however, the number of deaths at 6 years was increased in patients who received inotropes after CPB (p = 0.0247).

CONCLUSIONS

The increases in right-sided dimensions after CPB are associated with reduction in RV function and increased biventricular filling pressure, suggesting worsening biventricular function and interventricular dependence. Inotropic medications were associated with unaltered RV dimensions and increased biatrial activity.