Christoph Kaufmann

A survey of surgical simulation: applications, technology, and education

Surgical simulation for medical education is increasingly perceived as a valuable addition to traditional teaching methods. Simulators provide a structured learning experience, permitting practice without danger to patients, and simulators facilitate the teaching of rare or unusual cases. Simulators can also be used to provide an objective assessment of skills. This paper is a survey of current surgical simulator systems. The components of a simulator are described, current research directions are discussed, and key research questions are identified.

Lactated Ringer's solution resuscitation causes neutrophil activation after hemorrhagic shock

PURPOSE To determine the degree of neutrophil activation caused by hemorrhagic shock and resuscitation. METHODS Awake swine underwent 15-minute 40% blood volume hemorrhage, and a 1-hour shock period, followed by resuscitation with: group I, lactated Ringers solution (LR); group II, shed blood; and group III, 7.5% hypertonic saline (HTS). Group IV underwent sham hemorrhage and LR infusion. Neutrophil activation was measured in whole blood using flow cytometry to detect intracellular superoxide burst activity. RESULTS Neutrophil activation increased significantly immediately after hemorrhage, but it was greatest after resuscitation with LR (group I, 273 vs. 102%; p < 0.05). Animals that received shed blood (group II) and HTS (group III) had neutrophil activity return to baseline state after resuscitation. Group IV animals had an increase in neutrophil activation (259 vs. 129%; p < 0.05). CONCLUSION Neutrophil activation occurring after LR resuscitation and LR infusion without hemorrhage, but not after resuscitation with shed blood or HTS, suggests that the neutrophil activation may be caused by LR and not by reperfusion.

Controlled resuscitation for uncontrolled hemorrhagic shock.

OBJECTIVE To test the hypothesis that controlled resuscitation can lead to improved survival in otherwise fatal uncontrolled hemorrhage. METHODS Uncontrolled hemorrhage was induced in 86 rats with a 25-gauge needle puncture to the infrarenal aorta. Resuscitation 5 minutes after injury was continued for 2 hours with lactated Ringers solution (LR), 7.3% hypertonic saline in 6% hetastarch (HH), or no fluid (NF). Fluids infused at 2 mL x kg(-1) x min(-1) were turned on or off to maintain a mean arterial pressure (MAP) of 40, 80, or 100 mm Hg in six groups: NF, LR 40, LR 80, LR 100, HH 40, and HH 80. Blood loss was measured before and after 1 hour of resuscitation. RESULTS Survival was improved with fluids. Preresuscitation blood loss was similar in all groups. NF rats did not survive 4 hours. After 72 hours, LR 80 rats (80%) and HH 40 rats (67%) showed improved survival over NF rats (0%) (p < 0.05). Rebleeding increased with MAP. Attempts to restore normal MAP (LR 100) led to increased blood loss and mortality. CONCLUSION Controlled resuscitation leads to increased survival compared with no fluids or standard resuscitation. Fluid type affects results. Controlled fluid use should be considered when surgical care is not readily available.

Lactated ringer's solution and hetastarch but not plasma resuscitation after rat hemorrhagic shock is associated with immediate lung apoptosis by the up-regulation of the Bax protein.

BACKGROUND We previously demonstrated that the type of resuscitation fluid used in hemorrhagic shock affects apoptosis. Unlike crystalloid, whole blood seems to attenuate programmed cell death. The purpose of this study was to determine whether the acellular components of whole blood (plasma, albumin) attenuated apoptosis and to determine whether this process involved the Bax protein pathway. METHODS Rats were hemorrhaged 27.5 mL/kg, kept in hypovolemic shock for 75 minutes, then resuscitated over 1 hour (n = 44). Control animals underwent anesthesia only (sham, n = 7). Treatment animals were bled then randomly assigned to the following resuscitation groups: no resuscitation (n = 6), whole blood (n = 6), plasma (n = 6), 5% human albumin (n = 6), 6% hetastarch (n = 7), and lactated Ringers solution (LR, n = 6). Hetastarch was used to control for any colloid effect. LR was used as positive control. Immediately after resuscitation, the lung was collected and evaluated for apoptosis by using two methods. TUNEL stain was used to determine general DNA damage, and Bax protein was used to specifically determine intrinsic pathway involvement. RESULTS LR and hetastarch treatment resulted in significantly increased apoptosis in the lung as determined by both TUNEL and Bax expression (p < 0.05). Plasma infusion resulted in significantly less apoptosis than LR and hetastarch resuscitation. Multiple cell types (epithelium, endothelium, smooth muscle, monocytes) underwent apoptosis in the lung as demonstrated by the TUNEL stain, whereas Bax expression was limited to cells residing in the perivascular and peribronchial spaces. CONCLUSION Apoptosis after volume resuscitation of hemorrhagic shock can be affected by the type of resuscitation fluid used. Manufactured fluids such as lactated Ringers solution and 6% hetastarch resuscitation resulted in the highest degree of lung apoptosis. The plasma component of whole blood resulted in the least apoptosis. The process of apoptosis after hemorrhagic shock resuscitation involves the Bax protein.

Penetrating cardiac injuries: a population-based study.

BACKGROUND Wide variances exist in reports of survival rates after penetrating cardiac injuries because most are hospital-based reports and thus are affected by the local trauma system. The objective of this study was to report population-based, as well as hospital-based, survival rates after penetrating cardiac injury. METHODS Retrospective cohort analysis was performed during a 7-year period of 20,181 consecutive trauma admissions to a regional Level I trauma center and 6,492 medical examiners reports. A meta-analysis was performed comparing survival rates with available population-based reports. RESULTS There were 212 penetrating cardiac injuries identified, for an incidence of approximately 1 per 100,000 man years and 1 per 210 admissions. The overall survival rate was 19.3% (41 of 212) for the population studied, with survival rates of 9.7% (12 of 123) for gunshot wounds and 32.6% (29 of 89) for stab wounds. Ninety-six of the 212 patients were transported to the trauma center for treatment, resulting in an overall hospital survival rate of 42.7% (41 of 96), with a hospital survival rate of 29.3% (12 of 41) for gunshot wounds and 52.7% (29 of 55) for stab wounds. CONCLUSION Review of population-based studies indicates that there has been only a minor improvement in the survival rates for the treatment of penetrating cardiac injuries.

New simulation technologies for surgical training and certification: Current status and future projections

Computer-based virtual reality technology has evolved to the point at which medical simulation can be incorporated into medical education and into the eventual objective evaluation of surgical competence. Flight simulation provides a model for examining the role of computer-based simulation in medical training and certification. The plan by which medical simulators are being designed and validated for surgical training is presented, as is a description of the current state of medical simulation and the limitations of the technology. A realistic argument for adoption is suggested that takes into account lower price constraints, technological limitations, and professional barriers to the implementation of simulator-based training and accreditation.1

An Architecture for Simulating Needle-Based Surgical Procedures

Many surgical procedures use cannulas, guidewires, and catheters in the treatment of life threatening conditions (e.g. cardiac tamponade and tension pneumothorax), or for diagnosis (e.g. diagnostic peritoneal lavage). Simulator development is costly in time and resources. Most computer-based trainers are procedure-specific. Each trainer uses a different hardware configuration. The cost of using multiple simulators for teaching is prohibitive. A result is decreased acceptance of simulation for teaching. A generalized software architecture has been developed that simplifies the process of constructing trainers for needle-based surgical procedures. Different procedures can use the same hardware platform. The architecture has been used to develop two trauma simulators. A third simulator is currently being developed using this architecture.

Effect of hydroxyethyl starch on coagulopathy in a swine model of hemorrhagic shock resuscitation.

BACKGROUND Hydroxyethyl starch (HES) has a known dose-dependant effect on coagulopathy. The purpose of this study was to determine the effect of HES on coagulopathy after a period of hemorrhagic shock. METHODS Anesthetized swine underwent a 15-minute, 40% blood volume hemorrhage (28 mL/kg) and a 1-hour shock period, followed by resuscitation with sham resuscitation (group I); 6% HES, 15 mL/kg (group II); 5% albumin, 15 mL/kg (group III); lactated Ringers solution, 39 mL/kg, and 6% HES, 15 mL/kg (group IV); and lactated Ringers solution, 39 mL/kg, and 5% albumin, 15 mL/kg (group V). Coagulation function was measured by bleeding time, prothrombin time, partial thromboplastin time, fibrinogen, platelet count, and thromboelastography. RESULTS Platelet counts decreased significantly (p < 0.05) in all resuscitation groups except the sham resuscitation group. A significant decrease in platelets, fibrinogen levels, and maximum amplitude on thromboelastography was related to a dilutional effect of the fluid given and not a result of HES at the dose tested. CONCLUSION The linear dose-related coagulopathic effects of HES when given at moderate doses does not seem to be worsened by prolonged periods of hemorrhagic shock. The coagulopathy seen during resuscitation from hemorrhagic shock seems to be a dilutional effect.

Telepresence surgery system enhances medical student surgery training.

The telepresence surgery system (TeSS) permits the surgeon to operate on a patient across distances. This is achieved through real-time 3D video vision, stereo audio, and remote instrument control with haptic feedback. Telepresence surgery has been proposed to be useful in providing specialist operative consultation to remote areas. Remotely mentoring medical students with no surgical experience through complex procedures provides an even greater challenge. Third-year medical students with no prior operative experience were mentored exclusively through use of TeSS during a standard surgical skills lab. This two-day laboratory includes abdominal procedures and thoracic procedures. The medical students were alone in the operating room and the teaching surgeon was in an entirely separate room. Anatomy, surgical principles, and adjunct techniques were taught to the students. The students felt the experience was better than standard because of the enhanced learning secondary to the required verbal accuracy in describing the procedures. In addition, they felt they had better visibility since the instructor was not standing in the way. The telepresence surgery system can be successfully used to remotely mentor and enhance introductory surgical training for inexperienced medical students.

First Steps in Eliminating the Need for Animals and Cadavers in Advanced Trauma Life Support

The Advanced Trauma Life Support® course is designed to provide for optimal initial resuscitation of the seriously injured patient. The surgical skills component of this course requires the use of cadavers or anesthetized animals. Significant anatomical differences and ethical issues limit the utility of animals. The cost and difficulty in procuring cadavers makes widespread use of this option impractical. A combination of mannequin and computer-based surgical simulators is being developed to replace these animals and cadavers. The first of these simulators, a pericardiocentesis trainer, is complete.