Adam C. Adler

Perioperative Anesthesiology UltraSonographic Evaluation (PAUSE): A Guided Approach to Perioperative Bedside Ultrasound

BEDSIDE, OR POINT OF CARE, ultrasonography is emerging as a tool for real-time diagnostic assessment in addition to standard physical examination in the emergency department, intensive care unit, and now in the perioperative period as ultrasound didactics are being incorporated into residency training programs. Even though anesthesiologists have embraced the use of bedside ultrasound as a procedural tool, diagnostic use of this technology is underutilized, with the exception of transesophageal echocardiography. Diagnostic use of surface ultrasound techniques, such as transthoracic echocardiography (TTE) and lung ultrasonography, have been proposed in the cardiology, emergency medicine, and critical care medicine literature. These approaches (eg, Focused Assessment with Sonography for Trauma [FAST], FATE, and FoCUS) have proven useful as a guide for clinicians providing care to patients with unstable conditions and those who are acutely ill. However, these approaches recommend imaging that is not necessarily relevant to the perioperative patient (FAST) or exclude scanning of the lungs/pleura for pulmonary pathologic conditions (FATE/FoCUS), which may be important, especially during or after the administration of anesthesia. Few studies describing the diagnostic use of TTE or lung ultrasound by the general anesthesiologist exist, and to date, there are no systematic approaches for applying these techniques to the care of perioperative patients. Despite the wellaccepted diagnostic value of point-of-care ultrasound, adoption by anesthesia providers and incorporation into residency training curriculum have lagged. The use of point-of-care/bedside TTE/ultrasonography by non-cardiologists has been well-validated in emergency medicine and intensive care unit settings and in the preoperative evaluation of cardiac murmurs. Multiple studies have demonstrated that with just 1 day of ultrasound didactics, novice providers are able to identify clinically significant pathologic conditions. The Hemodynamic Echocardiography Assessment in Real Time (HART) course evaluated the ability of anesthesiologists and critical care/emergency medicine physicians to identify major abnormalities using limited TTE views. When judged by expert cardiologists, the providers’ determination of TTE findings was in agreement 90% to 99% of the time, with most disagreement related to false-positive interpretations. Canty et al demonstrated a 54% change in anesthetic management when bedside ultrasound was used in the preoperative evaluation of patients with symptoms of cardiac disease or those believed to be at risk for cardiac disease. Using perioperative TTE, Cowie identified a change in management for 82% of cases. In the Cowie cohort, use of TTE led to escalation or de-escalation of invasive monitoring strategies, procedure location changes or cancellations, fluid boluses or restrictions, or alteration in anesthetic management, and 20% of patients were referred for formal cardiology evaluation. Using bedside TTE in 99 patients with known or suspected cardiac disease, Canty et al found a significant number of patients with aortic stenosis, cardiac failure, tamponade, or significant intravascular volume depletion, leading to a change in management in 36% of patients. Applying focused cardiac ultrasound, Gerlach et al identified a previously unrecognized cardiac tamponade preoperatively while attempting to assess the patient’s overall cardiac function. This article reviews some clinical scenarios in which pointof-care ultrasonography might prove efficacious in the perioperative setting. The goal is to provide a structured approach to using bedside ultrasound as a physical examination adjunct and diagnostic tool that can be learned and performed by the general anesthesiologist. The Perioperative Anesthesiology UltraSonographic Evaluation (PAUSE) approach is a tool for the anesthesiologist to pause at various times during perioperative management and use bedside ultrasonography to assess the patient, extending the information provided by physical examination or vital sign monitoring. This approach to the use of ultrasound is described along with recommendations for how providers, new to the use of ultrasound for diagnostic imaging, can learn and properly apply these skills.

Misleading indexed hemodynamic parameters: the clinical importance of discordant BMI and BSA at extremes of weight

The widespread availability of minimally invasive hemodynamic monitors, encourages evaluation of cardiac output and stroke volume and are integral to algorithm based treatment plans. Patients with extremes of BSA are at risk of having their indices erroneously evaluated despite adequate non-indexed values. We evaluated the use of BMI in this population and identified a discordance of BSA and BMI values at extreme weights. We recommend un-indexed values in these patients when deciding treatment options.

Utility of Functional Hemodynamics and Echocardiography to Aid Diagnosis and Management of Shock.

ABSTRACT The utility of functional hemodynamics and bedside ultrasonography is increasingly recognized as advantageous for both improved diagnosis and management of shock states. In contrast to conventional “static” measures, “dynamic” hemodynamic measures and bedside imaging modalities enhance pathophysiology-based comprehensive understanding of shock states and the response to therapy. The current editions of major textbooks in the primary specialties – in which clinicians routinely encounter patients in shock – including surgery, anesthesia, emergency medicine, and internal medicine continue to incorporate traditional (conventional) descriptions of shock that use well-described (but potentially misleading) intravascular pressures to classify shock states. Reliance on such intravascular pressure measurements is not as helpful as newer “dynamic” functional measures including ultrasonography to both better assess volume responsiveness and biventricular cardiac function. This review thus emphasizes the application of current functional hemodynamics and ultrasonography to the diagnosis and management of shock as a contrast to conventional “static” pressure-based measures.

Effects of Body Surface Area-Indexed Calculations in the Morbidly Obese: A Mathematical Analysis

OBJECTIVE Cardiac and stroke indices routinely are used to communicate the adequacy of circulation, especially by cardiac anesthesiologists. However, indexed values may be distorted when derived using conventional formulae on morbidly obese patients. In extreme cases, distortion of the raw value by the indexed value may suggest inappropriate therapeutic interventions. This study attempted to highlight threshold values of body surface area (BSA) that place morbidly obese patients at risk of being overtreated. DESIGN Mathematical analysis. PARTICIPANTS Simulated patients. INTERVENTIONS BSA was derived using the commonly used Mosteller and Dubois and Dubois formulae on a range of simulated patients. These simulated BSAs then were applied to normal cardiac output (CO) and stroke volume (SV) values to identify the threshold at which BSA-indexed values result in a change in classification to abnormal. Additionally, the effects of 7 different published BSA formulae were examined, using a range of height-weight combinations. MEASUREMENTS AND MAIN RESULTS Critical thresholds at which BSA calculations would classify normal CO and SV as abnormal are presented in a tabular form. Among the 7 BSA formulae, there was substantial variation in predicted BSA at a given height-weight combination when values typically associated with morbid obesity are used. CONCLUSION In morbidly obese patients, cardiac and stroke indices can be misleading relative to the underlying raw values (CO and SV) as a result of distortion by widely used BSA formulae. The authors caution against relying on threshold cardiac and stroke indices as triggers for the initiation of hemodynamic therapies in the morbidly obese. Further research on what BSA formula should be used on patients with very extreme body types is warranted.

Heart rate response to a caudal block in children anesthetized with sevoflurane after ultrasound confirmation of placement

Previous studies identified decreasing heart rate (HR) as a predictor of successful caudal placement in children using halothane and isoflurane. No changes were found in HR in the one study using sevoflurane. We documented HR changes in children following a caudal block during sevoflurane anesthesia utilizing ultrasound to confirm successful caudal placement.

Use of transesophageal echocardiography for CorMatrix®-based tricuspid valve repair in a patient with recurrent endocarditis.

January 2015 • Volume 120 • Number 1 A 42-year-old female with a longstanding history of heroin use and polymicrobial endocarditis arrived with shortness of breath and a feeling of choking while supine. A transthoracic echocardiogram revealed right atrial enlargement, right ventricle (RV) dilatation, leftward bowing of the interatrial septum, and severe tricuspid regurgitation (TR). Over the preceding 18 months, she had multiple episodes of endocarditis with tricuspid valve (TV) vegetations, resulting in wide-open TR from leaflet malcoaptation. She was noncompliant with antibiotic therapy and was lost to follow-up. Written consent was obtained from the patient for publication of this report. Due to the patient’s history of drug use and risk for valvular reinfection, the surgical plan was for reconstruction of the TV using CorMatrix® (CorMatrix Cardiovascular Inc., Roswell, GA to facilitate native tissue regrowth. After induction of anesthesia and tracheal intubation, a transesophageal echocardiogram (TEE) was performed (X7-2t transducer; Philips Healthcare, Andover, MA). The 2-dimensional midesophageal (ME) 4-chamber view with rightward probe rotation revealed right atrial and RV dilatation with malcoaptation of the TV leaflets, severe TR (vena contracta 1.4 cm), and leftward bowing of the interatrial septum (Video 1, Supplemental Digital Content 1, http://links.lww.com/ AA/B20). The remainder of the TEE examination was unremarkable. Before incision, the surgical team requested measurements of the native valve to be performed. Using the 2-dimensional ME 4-chamber view with right rotation, we measured the TV annular diameter (38 mm), and distance from the lateral annulus to the papillary muscle in diastole (43 mm) (Fig. 1). The surgeon used these measurements to construct the flat CorMatrix sheet into a 3-dimensional, conical shape accounting for the patient’s annular diameter and distance from the annulus to the papillary muscle base. The surgeon used the diastolic annular diameter to calculate the TV circumference as 2π(diameter/2) or 119.4 mm. Circumference was divided by 3 to create the horizontal dimensions of the trifold corresponding to the anterior, posterior, and septal leaflets. The CorMatrix sheet

Technical communication: inhaled anesthetic agent-vaporizer mismatch: management in settings with limited resources: don't try this at home.

Agent-specific vaporizers minimize opportunities for error and evidence our specialty’s commitment to patient safety as a general principle. End-tidal anesthetic gas concentration monitoring is a useful adjunct whenever inhaled anesthetics are used in operating rooms. Due to their expense and required maintenance, end-tidal anesthetic gas monitors are not commonly used in developing nations. Unfortunately, in resource-constrained environments, situations may arise in which inhaled anesthetic agent-vaporizer mismatch may be necessary in the absence of end-tidal anesthetic gas monitoring. Rather than merely censure such practice as a threat to safety, we believe that certain anesthetic agent-vaporizer mismatch situations can be safely managed providing patients with predictable inspired anesthetic gas concentrations while minimizing errors. We present an approach based on mathematical models and tested in an artificial lung model. Mismatching of inhaled agent and vaporizer is a dangerous practice and should not be performed unless it is absolutely necessary. Such situations may arise in remote locations where neither end-tidal anesthetic gas monitoring nor vaporizer-specific agent is available. We hope our article provides guidance in such situations.