Mark W. Bowyer

Hypertonic saline: intraosseous infusion causes myonecrosis in a dehydrated swine model of uncontrolled hemorrhagic shock

BACKGROUND The Institute of Medicine has recommended intraosseous (IO) infusion of 7.5% hypertonic saline (HTS) for combat casualties in shock. We tested the safety and efficacy of this recommendation in a long-term survival model of uncontrolled hemorrhagic shock using dehydrated swine. METHODS Fourteen dehydrated Yorkshire swine had placement of a 12G needle in the right anterior tibia under isoflurane anesthesia. Uncontrolled hemorrhage was induced via left iliac artery and vein injury. Animals were kept in shock for 2 hours and then resuscitated over 2 hours with 5 mL/kg of 7.5% HTS given either as 10 small boluses (group I, n = 4) or two large boluses (group II, n = 6) to compare the physiologic response and blood loss. Control animals (group III, n = 4) received an equal volume of 0.9% saline IO and additional intravenous saline to equalize the salt load in all groups. RESULTS The three groups had similar physiologic responses, with no increase in blood loss following HTS resuscitation. However, between the second and fifth postresuscitation days, the 7.5% HTS resuscitated animals developed soft tissue necrosis or bone marrow necrosis of the right hind leg (group I, 100%; group II, 66.6%; group III, 0%). CONCLUSION HTS resuscitation effectively restored hemodynamic stability in dehydrated swine without increased bleeding from an uncontrolled vascular injury. However, IO infusion of HTS in this model was associated with a very high rate of local complications. Further investigations should be undertaken before IO use of 7.5% HTS in humans.

Teaching Breaking Bad News Using Mixed Reality Simulation

BACKGROUND Our novel teaching approach involved having students actively participate in an unsuccessful resuscitation of a high fidelity human patient simulator with a gun shot wound to the chest, followed immediately by breaking bad news (BBN) to a standardized patient wife (SPW) portrayed by an actress. METHODS Brief education interventions to include viewing a brief video on the SPIKES protocol on how to break bad news, a didactic lecture plus a demonstration, or both, was compared to no pretraining by dividing 553 students into four groups prior to their BBN to the SPW. The students then self-assessed their abilities, and were also evaluated by the SPW on 21 items related to appearance, communication skills, and emotional affect. All received cross-over training. RESULTS Groups were equal in prior training (2 h) and belief that this was an important skill to be learned. Students rated the experience highly, and demonstrated marked improvement of self-assessed skills over baseline, which was maintained for the duration of the 12-wk clerkship. Additionally, students who received any of the above training prior to BBN were rated superior to those who had no training on several communication skills, and the observation of the video seemed to offer the most efficient way of teaching this skill in a time delimited curriculum. CONCLUSION This novel approach was well received and resulted in improvement over baseline. Lessons learned from this study have enhanced our curricular approach to this vital component of medical education.

Advanced surgical skills for exposure in trauma: a new surgical skills cadaver course for surgery residents and fellows.

BACKGROUND Surgical education is changing owing to workforce and economic demands. Simulation and other technical teaching methods are used to acquire skills transferable to the operating room. Operative management of traumatic injuries has declined, making it difficult to acquire and maintain competence. The ASSET course was developed by the Committee on Trauma’s Surgical Skills Committee to fill a surgical skills need in resident and fellow education. Using a human cadaver, standardized rapid exposure of vital structures in the extremities, neck, thorax, abdomen, retroperitoneum, and pelvis is taught. METHODS A retrospective analysis of 79 participants in four ASSET courses was performed. Operative experience data were collected, and self-efficacy questionnaires (SEQs) were administered before and after the course. Course evaluations and instructor evaluation data were analyzed. Student’s and paired samples t tests as well as analysis of variance and Spearman &rgr; correlation coefficient analysis were performed using &agr; at p < 0.05. We hypothesized that the ASSET course would teach new surgical techniques and that learner self-assessed ability would improve. RESULTS Participants included 27 PGY-4, 20 PGY-5, 24 PGY-6 or PGY-7 and PGY-8 at other levels of training. Self-assessed confidence improved in all body regions (p < 0.001), with the greatest increase in upper extremity and chest. Pre- and post-SEQ scores correlated with trauma operative experience. Precourse SEQ scores differed by level of training. Instructor evaluations correlated with previous experience on a trauma service. Program evaluations averaged 4.73 on a 5-point scale, with gaining new knowledge rated at 4.8 and learning new techniques at 4.72. CONCLUSION A standardized cadaver-based surgical exposures course offered to senior surgical residents adds new surgical skills and improves participant self-assessed ability to perform emergent surgical exposure of vital structures.

A Study on the Perception of Haptics in Surgical Simulation

Physically accurate modeling of human soft-tissue is an active research area in surgical simulation. The challenge is compounded by the need for real-time feedback. A good understanding of human haptic interaction can facilitate tissue modeling research, as achieving accuracy beyond perception may be counterproductive. This paper studies human sensitivity to haptic feedback. Specifically, the ability of individuals to consistently recall specific haptic experience, and their ability to perceive latency in haptic feedback. Results suggest that individual performance varies widely, and that this ability is not correlated with clinical experience. A surprising result was the apparent insensitivity of test subjects to significant latency in haptic feedback. The implications of our findings to the design and development of surgical simulators are discussed.

Surgical pathology of colorectal cancer in filipinos: implications for clinical practice

BACKGROUND A number of studies published in the Philippine literature have demonstrated certain peculiar clinicopathologic characteristics of colorectal cancer among Filipinos. This study presents the latest data and analyzes their implications for clinical practice. STUDY DESIGN The pathology reports of all patients who underwent operation for colorectal cancer at the Philippine General Hospital over a period of 7 years were reviewed. RESULTS One thousand two hundred seventy-seven patients were included. The male to female ratio was almost 1:1. The majority of patients were in the sixth and seventh decades of life, with a mean age of 55.3 years. Patients 40 years of age and younger made up 17% of the total. The site of cancer in order of frequency was rectum (49.8%), left colon (27.9%), and right colon (21.4%). Cancers of the right colon were more common in women, and rectal cancers were more frequent in men. Seventy-six percent of the tumors were well to moderately differentiated adenocarcinomas, and 6.7% were poorly differentiated. Mucinous and signet ring carcinomas were found in 11% and 1% of cases, respectively. Forty-four percent of patients had localized disease at the time of operation, 54% had regional disease, and 2% had disseminated disease. Associated predisposing conditions noted were polyps (4.7%), schistosomiasis (3%), and tuberculosis (1.5%). CONCLUSIONS Colorectal cancer in Filipinos exhibits a number of unique clinicopathologic features, such as a higher proportion of early age of onset tumors, more advanced stage at presentation, an association with chronic granulomatous diseases, and relatively rare occurrence with polyps. This might suggest the possibility of a different pathway for tumor development of colorectal cancer in this population of patients. Also, current screening guidelines advocated for the Western population might not be appropriate for Filipinos.

Is Tension Pneumothorax a Threat in Trauma Laparoscopy

BACKGROUND Tension pneumothorax is a reported risk with pneumoperitoneum in the presence of diaphragmatic injuries. A goat model with and without diaphragmatic injury was used to determine if varying levels of intra-abdominal pressure (IAP) result in tension pneumothorax. METHODS Twenty-four goats were divided equally into four groups: (1) 5 mm Hg IAP control, (2) 15 mm Hg IAP control, (3) 5 mm Hg IAP with diaphragmatic injury, (4) 15 mm Hg IAP with diaphragmatic injury. Chest x-ray films were made and heart rate (HR), mean arterial pressure, central venous pressure (CVP), arterial blood gases, and airway pressure (AP) were measured at 10-minute intervals up to 30 minutes. Significant changes were determined by using the one-way analysis of variance and Mann-Whitney test with alpha set at p < 0.05. RESULTS In group 4, 100% (all six goats) developed radiographic evidence of tension pneumothorax by 10 minutes. Mean changes from baseline at 20 minutes for the following parameters were all significantly different from controls: HR (p < 0.05), CVP (p < 0.0001), PaO2 (p < 0.001), and AP (p < 0.004). Mortality was 67% (four of six) at 25 minutes. In group 3, 100% (all six goats) of the animals developed radiographic evidence of a simple pneumothorax without mediastinal shift. In this group, there were significant changes in PaO2 (p < 0.003), AP (p < 0.04), and HR (p < 0.05). Mortality was 16% (one of six) at 25 minutes. CONCLUSION In this goat model of diaphragmatic injury, tension pneumothorax is a significant threat when pneumoperitoneum is maintained at 15 mm Hg IAP. Pneumoperitoneum at 5 mm Hg IAP leads to simple pneumothorax with deleterious effects on oxygenation. Changes in AP, CVP, HR, and PaO2 provide early clues to the development of the problem.

Development and Validation of Trauma Surgical Skills Metrics: Preliminary Assessment of Performance after Training

BACKGROUND Maintaining trauma-specific surgical skills is an ongoing challenge for surgical training programs. An objective assessment of surgical skills is needed. We hypothesized that a validated surgical performance assessment tool could detect differences following a training intervention. METHODS We developed surgical performance assessment metrics based on discussion with expert trauma surgeons, video review of 10 experts and 10 novice surgeons performing three vascular exposure procedures and lower extremity fasciotomy on cadavers, and validated the metrics with interrater reliability testing by five reviewers blinded to level of expertise and a consensus conference. We tested these performance metrics in 12 surgical residents (Year 3–7) before and 2 weeks after vascular exposure skills training in the Advanced Surgical Skills for Exposure in Trauma (ASSET) course. Performance was assessed in three areas as follows: knowledge (anatomic, management), procedure steps, and technical skills. Time to completion of procedures was recorded, and these metrics were combined into a single performance score, the Trauma Readiness Index (TRI). Wilcoxon matched-pairs signed-ranks test compared pretraining/posttraining effects. RESULTS Mean time to complete procedures decreased by 4.3 minutes (from 13.4 minutes to 9.1 minutes). The performance component most improved by the 1-day skills training was procedure steps, completion of which increased by 21%. Technical skill scores improved by 12%. Overall knowledge improved by 3%, with 18% improvement in anatomic knowledge. TRI increased significantly from 50% to 64% with ASSET training. Interrater reliability of the surgical performance assessment metrics was validated with single intraclass correlation coefficient of 0.7 to 0.98. CONCLUSION A trauma-relevant surgical performance assessment detected improvements in specific procedure steps and anatomic knowledge taught during a 1-day course, quantified by the TRI. ASSET training reduced time to complete vascular control by one third. Future applications include assessing specific skills in a larger surgeon cohort, assessing military surgical readiness, and quantifying skill degradation with time since training.

Using an Individual Procedure Score Before and After the Advanced Surgical Skills Exposure for Trauma Course Training to Benchmark a Hemorrhage-Control Performance Metric

OBJECTIVE Test with an individual procedure score (IPS) to assess whether an unpreserved cadaver trauma training course, including upper and lower limb vascular exposure, improves correct identification of surgical landmarks, underlying anatomy, and shortens time to vascular control. DESIGN Prospective study of performance of 3 vascular exposure and control procedures (axillary, brachial, and femoral arteries) using IPS metrics by 2 colocated and trained evaluators before and after training with the Advanced Surgical Skills Exposure for Trauma (ASSET) course. IPS, including identification of anatomical landmarks, incisions, underlying structures, and time to completion of each procedure was compared before and after training using repeated measurement models. SETTING Audio-video instrumented cadaver laboratory at University of Maryland School of Medicine. PARTICIPANTS A total of 41 second to sixth year surgical residents from surgical programs throughout Mid-Atlantic States who had not previously taken the ASSET course were enrolled, 40 completed the pre- and post-ASSET performance evaluations. RESULTS After ASSET training, all components of IPS increased and time shortened for each of the 3 artery exposures. Procedure steps performed correctly increased 57%, anatomical knowledge increased 43% and skin incision to passage of a vessel loop twice around the correct vessel decreased by a mean of 2.5 minutes. An overall vascular trauma readiness index, a comprehensive IPS score for 3 procedures increased 28% with ASSET Training. CONCLUSIONS Improved knowledge of surface landmarks and underlying anatomy is associated with increased IPS, faster procedures, more accurate incision placement, and successful vascular control. Structural recognition during specific procedural steps and anatomical knowledge were key points learned during the ASSET course. Such training may accelerate acquisition of specific trauma surgery skills to compensate for shortened training hours, infrequent exposure to major vascular injuries, or when just-in-time training is necessary. IPS is a benchmark for competence in extremity vascular control.

Measurement of Intracellular ?-Interferon, Interleukin-4, and Interleukin-10 Levels in Patients Following Laparoscopic Cholecystectomy

(2000). Measurement of Intracellular ?-Interferon, Interleukin-4, and Interleukin-10 Levels in Patients Following Laparoscopic Cholecystectomy. Journal of Investigative Surgery: Vol. 13, No. 3, pp. 161-167.

Clinical and molecular biologic characteristics of early-onset versus late-onset colorectal carcinoma in Filipinos

A case-control study of Filipino patients who underwent surgical resection for colorectal cancer (CRC) during a 1-year period was undertaken. Thirty-five patients under age 40 years were identified. Paraffin blocks of these and 35 randomly selected patients over age 40 underwent histologic and immunohistochemical evaluation. Markers chosen for evaluation included the apoptosis-associated gene products (p53 and bcl-2), a tumor proliferation activity-related factor (Ki-67), and the markers (MLH1 and MSH2) of DNA microsatellite instability (MSI). Results were correlated with age and the stage and location of the tumor. The average age of the early-onset group was 30.7 years compared to the late-onset group at 67.0 years; and the male/female ratio was equivalent. The younger patients had a significantly higher Dukes’ stage, the tumors were more poorly differentiated, and they were more frequently of the mucinous and signet ring cell histopathologic type. Expression of p53 was higher in the younger patients (p < 0.001) and was independent of the degree of differentiation or the stage of the tumor. No differences of expression were noted for the other markers measured. The increased frequency of CRC in Filipino patients less than 40 years of age offers a unique opportunity to gain a better understanding of carcinogenesis, which might be exploited during diagnosis and management. The differences noted between the early- and late-onset CRC are provocative and provide an impetus for increased screening in Filipinos.RésuméCette étude cas-témoin concerne des patients philippins ayant eu une résection chirurgicale pour cancer colorectal pendant une période d’observation d’un an. Trente cinq patients de moins de 40 ans ont été identifiés. L’examen histologique et immunohistochimique après fixation à la paraffine a intéressé ces pièces de résections et comparé à ceux de 35 autres patients sélectionnés au hasard. Les marqueurs choisis pour évaluation comprenaient les produits génétiques associés à l’apoptose (p53 et bcl-2), un facteur d’activité de prolifération tumorale (Ki-67), et les marqueurs (MLH1 et MSH2) de l’instabilité microsatellite d’ADN (MSI). Les résultats ont été corrélés avec l’âge, le stade et la localisation de la tumeur. L’âge moyen du groupe porteur de cancer d’apparition précoce a été de 30.7 ans comparé à celui du groupe d’apparition tardive qui a été de 67 ans; le sexe ratio a été de 1. Les patients les plus jeunes avaient un stade de Dukes significativement plus avancé, des cancers plus indifférenciés, et étaient plus souvent mucineux ou contenant des cellules à bague de chaton. L’expression P53 était plus forte chez les patients plus jeunes (p < 0.001), indépendamment du degré de dédifférenciation ou du stade de la tumeur. On n’a retrouvé aucune différence dans l’expression des autres marqueurs tumoraux mesurés. L’incidence plus élevée de cancer colorectal chez les patients philippins de moins de 40 ans est une situation unique pour pourvoir mieux comprendre la carcinogenèse et qui pourrait être exploitée pour améliorer le diagnostic et la prise en charge. Les différences notées entre les cancers d’apparition précoce et tardive sont provocatrices et nous incitent à proposer un programme accéléré de dépistage.ResumenSe realizó un estudio de control de casos de pacientes filipinos sometidos a resección por cancer colo-rectal (CCR) en un periodo de un año. Treinta y cinco pacientes menores de 40 años fueron identificados. Se hizo el estudio histológico e inmunohistoquímico de éstos y de otros 40 pacientes mayores de 40 años seleccionados al azar. Los marcadores escogidos para la evaluatión incluyeron los productos del gen asociado con la apoptosis (p53 y bel-2); un factor relacionado con la actividad tumoral (Ki-67); y los marcadores (M1H1) y MSH2) de inestabilidad microsatelital de ADN (MSI). Los resultados fueron correlacionados con la edad, el estado y la ubicación del tumor. La edad promedio de los pacientes con presentación temprana de la enfermedad fue 30.7 anos, en tanto que la edad promedio del grupo con presentatión tardía fue 67 años; la relatión masculino a femenino fue equivalente. Los pacientes más jóvenes mostraron un estado de Duke más alto, sus tumores eran más pobremente diferenciados y más comúnmente del tipo histopatológico mucinoso y en anillo de sello. La expresion de P53 aparetió más alta en el grupo de pacientes más jóvenes (p < 0.001) e independiente del grado de diferenciación del tumor. No se encontraron diferencias en la expresión de los otros marcadores. La mayor frecuencia de CCR en los pacientes filipinos menores de 40 años ofrece una oportunidad única para lograr una mejor comprensión del proceso de carcinogenesis que podría ser explotada tanto en el diagnóstico como en el manejo de la neoplasia. Las diferencias observadas entre los grupos de menor y mayor edad en cuanto a la presentatión del CCR son provocativas y dan fundamento a incrementar el tamizaje en los filipinos.