Perioperative Point-of-Care Ultrasonography

In this issue of Anesthesia & Analgesia, Daurat et al.1 describe a simple and accurate method for diagnosing postoperative urinary retention with the use of point-of-care ultrasound bladder measurement. This study adds to the growing body of evidence supporting the benefits of point-of-care ultrasound in the perioperative setting. By using an inexpensive handheld ultrasound device (GE Vscan; General Electrics, Madison, WI), the authors demonstrated the ability to reliably diagnose postoperative urinary retention using a rapid, single-view examination. At a cost similar to that of a bladder scanner, the point-of-care ultrasound device used in this study provides similar information, while having the flexibility to perform other patient assessments. This study highlights the growing importance of ultrasound in perioperative medicine and strongly suggests that anesthesiologists should be proficient users of ultrasound technology in areas beyond regional anesthesia and central vascular access. As anesthesiologists are increasingly engaged in management outside of the operating room, part of the emerging Perioperative Surgical Home initiative, we will soon be expected to diagnose cardiopulmonary disorders and optimize hemodynamic condition in the preoperative or postoperative period. Other relevant topics, including assessment of gastric volume, estimation of intracranial pressure (ICP), and endotracheal tube location, are areas in which point-of-care ultrasound can provide valuable assistance to the perioperative physician. CARDIOPULMONARY ASSESSMENT Because the condition of patients undergoing surgery becomes increasingly complicated, anesthesiologists require methods to expeditiously diagnose and manage cardiopulmonary disease. Transthoracic examination of the heart and lungs using bedside point-of-care ultrasound is a reliable tool compared with formal echocardiography.2 Assessments of global left ventricular function, abdominal aorta size, presence of pleural or pericardial effusions, right ventricular function, and valvular function (excluding aortic stenosis) (r > 0.81) are all readily available using point-of-care ultrasound.2 Not surprisingly, different protocols have emerged for rapid bedside cardiac point-of-care ultrasound examination.3–6 In addition, the ability to train noncardiologists to perform and interpret a limited transthoracic examination that focused on assessment of left ventricular function has been demonstrated,7,8 and guidelines have been published for point-of-care cardiac ultrasound by noncardiologists in the intensive care setting.8 Volume status and volume responsiveness are another area in which point-of-care ultrasound can assist the perioperative physicians. Specifically, monitoring for the collapsibility of the inferior vena cava has been shown to be an effective measurement of reduced filling pressures.9 Another modality that helps identify filling pressures of the patient’s cardiovascular system involves the direct measurement of left ventricular end-diastolic area. Several studies have shown the utility of point-of-care ultrasound in helping to predict preload status.10 Similar to cardiac point-of-care ultrasound, pulmonary point-of-care ultrasound has proven to be a valuable tool for the detection of pneumothorax11 even when used by recently trained inexperienced personnel.12 Ultrasonography has been shown to be more accurate than auscultation or chest radiography for the detection of pleural effusion, consolidation, and alveolar interstitial syndrome in the critical care setting13 when performed by nonradiologists.14 BEYOND CARDIOPULMONARY ASSESSMENT Emerging areas of point-of-care ultrasound relevant for the perioperative physician include assessment of gastric volume, estimations of ICP, and location of the endotracheal tube. A grading system, based exclusively on qualitative sonographic assessment of the gastric antrum, has shown strong correlation with predicted gastric volume.15 Anesthesiologists have demonstrated the ability to achieve a 95% success rate with appropriate training and supervision,16 and its potential for widespread adoption has been suggested.17 Evaluation of elevated ICP, via assessment of the diameter of the optic nerve sheath, is another modality for which point-of-care ultrasound has proven to be useful.18 This technique may assist patient risk stratification in the perioperative setting. Finally, detection of unrecognized malposition of the endotracheal tube is of upmost importance to anesthesiologists. The use of ultrasound for adjunct confirmation of tracheal versus esophageal intubation has been demonstrated.19 One study also showed the successful ability of point-of-care ultrasound to verify the correct position of the endotracheal tube in the trachea in a cadaver model.20 These studies suggest the opportunity to apply point-of-care ultrasound for airway management in the operating room. A CALL FOR PERIOPERATIVE POINT-OF-CARE ULTRASOUND EDUCATION Until 2001, point-of-care ultrasound had been a modality for cardiologists and obstetricians.21 This brief review highlights the utility of point-of-care ultrasound for perioperative medicine and indicates the need for anesthesiologists to expand their use of point-of-care ultrasound beyond vascular access and regional anesthesia. As the critical care physicians of the perioperative arena, point-of-care ultrasound, when used appropriately, may benefit the anesthesiologist and his/her patients throughout the preoperative evaluation, medical management in the operating room, and managing patients after surgery. We suggest the development of a comprehensive point-of-care ultrasound curriculum to help the anesthesiologist learn how to use point-of-care ultrasound throughout the perioperative period. We have designed a curriculum, termed Focused, PeriOperative, Risk, Evaluation, Sonography, Involving, Gastro-Abdominal, Hemodynamic, and Trans-Thoracic ultrasound (FORESIGHT) to teach residents the essentials of ultrasound examination. This curriculum is currently being taught and evaluated at the University of California Irvine. Our institution has been identified as a leading center for point-of-care ultrasound education for medical students.22 Preliminary evaluations of the FORESIGHT curriculum have demonstrated educational utility.23 Along with the potential benefit of anesthesiologists being able to perform and interpret point-of-care ultrasound studies, there is a risk of mismanagement secondary to image misinterpretation.24 Johnson and Oren-Grinberg24 stated that it is worthwhile to recall that, a few years ago, intraoperative transesophageal echocardiography, ultrasound for vascular access, and ultrasound for regional anesthesia were considered controversial modalities. All of these have become standard training for anesthesiology residents. As new technologies become available, our residents need to quickly adopt competence to provide optimal patient care. This requires that new technology be given high priority in residency training. Anesthesiologists have demonstrated a strong level of involvement in point-of-care ultrasound.24 As point-of-care ultrasound has become more readily available, and with growing demand for our skills throughout perioperative care, anesthesiologists need to embrace training and widespread adoption of perioperative point-of-care ultrasound. DISCLOSURES Name: Davinder Ramsingh, MD. Contribution: This author helped design the study, write the manuscript, and review the literature. Attestation: Davinder Ramsingh approved the final manuscript. Conflicts of Interest: Davinder Ramsingh is a recipient of a Foundation for Anesthesia Education and Research Grant for Research in Education on the topic of point-of-care ultrasound. Name: John Christian Fox, MD. Contribution: This author helped write the manuscript. Attestation: John Christian Fox approved the final manuscript. Conflicts of Interest: John Christian Fox reports the following conflicts of interest: SonoSite: Consultant, Equipment Loan; SonoSim: Consultant, Shares. Name: William C. Wilson, MD, MA. Contribution: This author helped write the manuscript. Attestation: William C. Wilson approved the final manuscript. Conflicts of Interest: This author has no conflicts of interest to declare. This manuscript was handled by: Steven L. Shafer, MD.