Training residents using simulation technology: experience with ultrasound for trauma

BACKGROUND

The need for surgeons to become proficient in performing and interpreting ultrasound examinations has been well recognized in recent years, but providing standardized training remains a significant challenge. The UltraSim (MedSim, Ft. Lauderdale, Fla) ultrasound simulator is a modified ultrasound machine that stores patient data in three-dimensional images. By scanning on the UltraSim mannequin, the student can reconstruct these images in real-time, eliminating the need for finding normal and abnormal models, while providing an objective method of both teaching and testing. The objective of this study was to compare the posttest results between residents trained on a real-time ultrasound simulator versus those trained in a traditional hands-on patient format. We hypothesized that both methods of teaching would yield similar results as judged by performance on the interpretive portion of a standardized posttest. It is designed as a prospective, cohort study from two university trauma centers involving residents at the beginning of their first or second postgraduate year of training. The main outcome measure was performance on a standardized posttest, which included interpretation of ultrasound cases recorded on videotape.

METHODS

Students first took a written pretest to evaluate their baseline knowledge of ultrasound physics as well as their ability to interpret basic ultrasound images. The didactic portion of the course used the same teaching materials for all residents and included lectures on ultrasound physics, ultrasound use in trauma/critical care, and a series of instructional videos. This didactic session was followed by 1 hour for each student of hands-on training on medical models/medical patients (group I) or by training on the ultrasound simulator (group II). The pretest was repeated at the completion of the course (posttest). Data were stratified by postgraduate year, i.e., PG1 or PG2.

RESULTS

A total of 74 residents were trained and tested in this study (PG1 = 48, PG2 = 26). All residents showed significant improvement in their pretest and posttest scores (p = 0.00) in both their knowledge of ultrasound physics and in their interpretation of ultrasound images. Importantly, we could not demonstrate any significant difference between groups trained on models/patients (group I) versus those trained on the simulator (group II) when comparing their posttest interpretation of ultrasound images presented on videotapes (PG1, group I mean score 6.9 +/- 1.4 vs. PG1, group II mean score 6.5 +/- 1.6, p = 0.32; PG2, group I mean score 7.7 +/- 1.4 vs. PG2, group II mean score 7.9 +/- 1.2, p = 0.70).

CONCLUSION

The use of a simulator is a convenient and objective method of introducing ultrasound to surgery residents and compares favorably with the experience gained with traditional hands-on patient models.

Use of an Objective Structured Clinical Examination (OSCE) for the assessment of physician performance in the ultrasound evaluation of trauma

BACKGROUND

A reliable means of assessing physician competency in performing ultrasound (US) is critical for training and credentialing. Objective Structured Clinical Examinations (OSCE) have been used successfully to assess clinical competency in other areas of surgical education but have not been applied previously to trauma ultrasound training. The objectives of this study were to assess physician performance in the focused abdominal sonography in trauma (FAST) examination by using a specifically designed OSCE, and to determine whether the OSCE detects differences in two determinants of competency (knowledge acquisition and clinical interpretation skills).

METHODS

Eighty-two physicians in surgery (n = 49) and emergency medicine (n = 33) at a Level I trauma center were evaluated. All participated in a FAST course consisting of didactic sessions on US physics, indications, and technique, FAST examination videos, and a hands-on session with human models. The OSCE consisted of two parts: written examination that assessed factual knowledge, and videotape of real-time US examinations that assessed interpretation skills. The OSCE was administered before and after the FAST course.

RESULTS

Significant improvements in postcourse OSCE scores were observed for factual knowledge (52.5 +/- 2.0 vs. 87.5 +/- 1.1, p < 0.001) and interpretation skills (27.2 +/- 1.4 vs. 62.9 +/- 1.3, p < 0.007). Scores for US interpretation were significantly lower than those for factual knowledge at both precourse (27.2 +/- 1.4 vs. 52.5 - 2.0, p < 0.001) and postcourse (62.9 +/- 1.3 vs. 87.5 +/- 1.1, p < 0.01). No performance differences were observed between surgeons and emergency medicine physicians and no effect of training level on test scores was observed.

CONCLUSION

Knowledge acquisition and US interpretation skills can be assessed reliably with a specifically designed OSCE. Although both skills improved after participation in a FAST course, US interpretation scores were consistently lower than those for factual knowledge. This study supports the use of the objective structured clinical examination in both the design of ultrasound teaching programs and the assessment of physician competency.

Decrease in mucosal alkaline phosphatase: a potential marker of intestinal reperfusion injury

Intestinal ischemia necessitates rapid re-establishment of blood flow to prevent irreversible anoxic tissue damage. However, reperfusion results in additional injury as a consequence of the generation of oxygen free radicals. To date, no clear-cut marker to differentiate between ischemia versus reperfusion injury is available. In this regard, previous studies from our laboratory utilizing a rat in vitro lipid peroxidation model demonstrated that the generation of free radicals resulted in the inactivation of only the intestinal brush border alkaline phosphatase enzyme, with no effect on other membrane-bound digestive enzymes. Current studies were designed to assess the possibility of alkaline phosphatase being a specific marker of the reperfusion injury in canine and human ex vivo ischemia/reperfusion models. Small bowels harvested from canines and organ donors were subjected to ischemia followed by reperfusion. Brush border membrane enzymes, alkaline phosphatase, sucrase, maltase, and gamma-glutamyl transpeptidase were assayed in mucosal extracts from intestines with ischemia versus reperfusion. In both experimental models, there was no change in any enzyme activity with warm ischemia alone. In contrast, alkaline phosphatase activity was significantly decreased in both the canine and human reperfusion models, with no change in specific activities of sucrase, maltase, and gamma-glutamyl transpeptidase. Our data indicate that the alkaline phosphatase enzyme activity may represent a potential marker of intestinal reperfusion injury and may permit quantitative assessments of therapeutic interventions in human intestinal reperfusion injury.

The surgeon's use of transesophageal echocardiography

Transesophageal echocardiography has become an instrumental diagnostic modality for the accurate evaluation of cardiac and aortic anatomy and function. Multiplanar technology has facilitated improved visualization of structures and enhanced TEE over TTE in many situations. Care of the trauma patient and critically ill patient is improved with the appropriate and timely performance of TEE. Education, certification, credentialing, and determination of competency are areas that need to be addressed continually in the future.

Rapid detection of traumatic effusion using surgeon-performed ultrasonography

BACKGROUND

In the injured patient, rapid assessment of the thorax can yield critical information for patient management and triage.

OBJECTIVES

The objectives of this prospective study were (1) to determine if experienced surgeon sonographers could successfully use a focused thoracic ultrasonographic examination to detect traumatic effusion, and (2) to compare the accuracy and efficiency of ultrasonography with supine portable chest radiography.

METHODS

Surgeon-sonographers performed thoracic ultrasonographic examinations on patients with blunt and penetrating torso injuries during the Advanced Trauma Life Support secondary survey. All patients also underwent portable chest radiography. Performance times for ultrasonography and chest radiography were recorded. Comparisons were made of the performance times and accuracy of both tests in detecting traumatic effusion.

RESULTS

In 360 patients, there were 40 effusions, 39 of which were detected by ultrasonography and 37 of which were detected by chest radiography. The 97.5% sensitivity and 99.7% specificity observed for thoracic ultrasonography were similar to the 92.5% sensitivity and 99.7% specificity for portable chest radiography. Performance time for ultrasonography was significantly faster than that for chest radiography (1.30 +/- 0.08 vs. 14.18 +/- 0.91 minutes, p < 0.0001).

CONCLUSION

Surgeons can accurately perform and interpret a focused thoracic ultrasonographic examination to detect traumatic effusion. Surgeon-performed thoracic ultrasonography is as accurate but is significantly faster than supine portable chest radiography for the detection of traumatic effusion.

The role of surgeon-performed ultrasound in patients with possible cardiac wounds

OBJECTIVE

The authors evaluate surgeon-performed ultrasound in determining the need for operation in patients with possible cardiac wounds.

BACKGROUND DATA

Ultrasound quickly is becoming part of the surgeon's diagnostic armamentarium; however, its role for the patient with penetrating injury is less well-defined. Although accurate for the detection of hemopericardium, the lack of immediate availability of the cardiologist to perform the test may delay the diagnosis, adversely affecting patient outcome. To be an effective diagnostic test in trauma centers, ultrasound must be immediately available in the resuscitation area and performed and interpreted by surgeons.

METHODS

Surgeons performed pericardial ultrasound examinations on patients with penetrating truncal wounds but no immediate indication for operation. The subcostal view detected hemopericardium, and patients with positive examinations underwent immediate operation by the same surgeon. Vital signs, base deficit, time from examination to operation, operative findings, treatment, and outcome were recorded.

RESULTS

During 13 months, 247 patients had surgeon-performed ultrasound. There were 236 true-negative and 10 true-positive results, and no false-negative or false-positive results; however, the pericardial region could not be visualized in one patient. Sensitivity, specificity, and accuracy were 100%; mean examination time was 0.8 minute (246 patients). Of the ten true-positive examinations, three were hypotensive. The mean time (8 patients) from ultrasound to operation was 12.1 minutes; all survived. Operative findings (site of cardiac wounds) were: left ventricle (4), right ventricle (3), right atrium (2), right atrium/superior vena cava (1), and right atrium/inferior vena cava (1).

CONCLUSIONS

Surgeon-performed ultrasound is a rapid and accurate technique for diagnosing hemopericardium. Delay times from admission to operating room are minimized when the surgeon performs the ultrasound examination.

Defining the critical limit of oxygen extraction in the human small intestine

Although animal models have been used to characterize the relation between oxygen consumption and blood flow, reliable data have not been generated in the human small intestine. We perfused segments of human small intestine by using an ex vivo perfusion circuit that allowed precise manipulation of blood flow and perfusion pressure. Our goal was to define the critical level of intestinal blood flow necessary to maintain the metabolic needs of the tissue. Human small intestine (n = 5) tissue obtained at transplantation harvest was transported on ice to the laboratory. A 40-cm mid-jejunal segment was selected for perfusion, and appropriate inflow and outflow vessels were identified and cannulated. Perfusion with an autologous blood solution was initiated through an extracorporeal membrane oxygenation circuit. After a 30-minute equilibration period, arterial and venous blood gases were measured at varying flow rates while maintaining a constant hematocrit level. Arterial and venous oxygen content, arteriovenous oxygen difference (A-VO2 diff), and oxygen consumption (VO2) were then calculated. Our results demonstrated that at blood flows > 30 ml/min/100 g, VO2 is independent of blood flow (1.6 +/- 0.06 ml/min/100 g), and oxygen extraction is inversely related to flow. Below this blood flow rate of 30 ml/min/100 g, oxygen extraction does not increase further (6.3 +/- 0.3 vol%), and VO2 becomes flow dependent. This ex vivo preparation defines for the first time a threshold value of blood flow for small intestine below which oxygen consumption decreases (30 ml/min/100 g). Previous animal studies have correlated such a decrease in oxygen consumption with functional and histologic evidence of tissue injury. This "critical" flow rate in human intestine is similar to that found previously in canine and feline intestine, but lower than that of rodent species.

Neutrophil depletion attenuates human intestinal reperfusion injury

Intestinal ischemia/reperfusion injury (I/R) results from reactive oxygen metabolites generated by the xanthine oxidase system and activated neutrophils (PMN). In animal models, removing PMN from initial reperfusate has consistently decreased tissue injury. This experiment was designed to test this potential clinical treatment in human bowel subjected to I/R. The extent of reperfusion injury was assessed by measuring the activity of mucosal alkaline phosphatase (A phi), which is a specific marker of reperfusion injury. Human small intestine (n = 13) obtained at the time of organ harvest for transplantation was perfused for 60 min on an ex vivo perfusion circuit. Reperfusate consisted of autologous blood passed through a leukocyte filter (n = 6) or unfiltered blood (n = 7). Control intestine was sampled at harvest, after transport to the lab on ice (cold ischemia), and after 60 min warm ischemia. Mucosa was homogenized and assayed for A phi activity by cleavage of p-nitrophenyl phosphate. A phi activity (nmole/mg/min) was not decreased after either cold (774 +/- 37) or warm (753 +/- 40) ischemia compared to freshly harvested bowel (770 +/- 51). Both reperfused segments showed a significant decrease in A phi activity compared to controls (P < 0.05); however, reperfusion with leukocyte-filtered blood attenuated the decrease in enzyme activity compared to unfiltered blood (327 +/- 30 vs 506 +/- 25, P < 0.05), constituting an apparent reduction in injury of 35%. The observation that the severity of reperfusion injury was decreased by removal of PMN from the reperfusate demonstrates the efficacy of this strategy in human intestine for the first time.

Chemosensory properties of sour tastants

In Experiment 1, a taste quality fractionation procedure was used to establish the degree to which sour and non-sour taste sensations are elicited by six concentrations of each of seven acids: citric, hydrochloric, sulfuric, lactic, malic, phosphoric and tartaric. In general, the acids differed significantly in their ability to elicit sour, salty and bitter sensations, with sulfuric and hydrochloric acids producing the smallest proportions of perceived sourness. Bitterness was found to be the largest non-sour sensation produced, followed by saltiness. The perceived taste qualities of the acids were stable across a wide range of concentrations. In Experiment 2 the extent to which the vapors of these test acids produce detectable intranasal non-gustatory sensations at concentration levels used in many human taste experiments was examined. All acids induced clear intranasal sensations at concentration levels used in some suprathreshold taste paradigms. The results suggest that a number of measures of sour taste sensation may be confounded by non-sour chemosensory factors, including intranasal stimulation.