Effect of prior clinical experience on students' knowledge and performance in surgery.

Approaches to designing an optimal surgical curriculum and studies of validity and reliability of students' evaluations have neglected the potential effect of prior clinical experience, although this admittedly increases greatly from those entering surgery as the first clinical clerkship to those taking surgery after completion of all other clinical rotations. The present study assesses students' knowledge on entering the surgery clerkship, reevaluates knowledge, assesses performance on completion of the surgery clerkship, and determines the effect of prior clinical experience on both knowledge and performance. Four hundred fifty consecutive students were evaluated during 2 academic years with a 100-question multiple-choice pretest, posttest, two oral examinations, and three subjective evaluations by surgical faculty members and housestaff. Reliability of the multiple choice examinations averaged 0.70 as determined by the KR-21 coefficient. Both mean pretest and posttest scores decreased with increasing clinical experience, mainly due to loss of preclinical knowledge. Nevertheless, scores on subjective evaluations increased. Regression analysis demonstrated positive intercorrelation among the subjective evaluations but no correlation to the objective forms of evaluation. It is suggested that multiple-choice examinations lack the ability to assess clinical competence and decision-making skills, qualities that are better evaluated by faculty members. The efficiency of teaching methods and the fairness of final grades may benefit from recognition of the effects of prior clinical rotations.

Repair of growing vessels. Continuous absorbable or interrupted nonabsorbable suture?

Twenty 1-month-old piglets were subjected to aortic transection and primary repair either with a posterior-running, anterior-interrupted nonabsorbable suture (group 1) or a circumferential continuous absorbable suture (group 2) technique. Mean piglet weight increased by 886% at six months and 1,184% at nine months. Aortic cross-sectional areas increased by 243% and 340%, respectively. Grossly visible, though minimal, stricture formation was noted in three pigs from group 1 and was associated with an overall 5.8% average anastomotic stricture at six months and 3.5% at nine months in group 1, compared with 0.2% and -0.1%, respectively, in group 2. Adhesion formation, fibrosis, and foreign-body reaction were common in group 1 but negligible in group 2. This corresponded to a mean wall thickness measured at nine months of 2.0 +/- 0.9 mm in group 1 and of 1.0 +/- 0.4 mm in group 2.

Skin staples in potentially contaminated wounds.

In potentially contaminated surgical procedures, wound infection is more likely when percutaneous sutures are used rather than skin tapes. Our reluctance to use tapes routinely because of variability in their adhesive properties prompted this evaluation of the ability of skin staples to resist abscess formation after contamination of the subcutaneous space. In each of 180 mice, a predetermined quantity of Staphylococcus aureus was injected into the subcutaneous space of a fresh skin incision. Closure with the skin stapler was most resistant to abscess formation. Presumably, percutaneous sutures provide a nidus for bacterial growth in the relatively avascular subcutaneous space. This problem is avoided by the use of skin tapes or staples. For those who are insecure about the strength of a closure with skin tapes, the skin stapler should provide an alternative in potentially contaminated cases where delayed primary closure is not elected.

Validity of multiple-choice examinations in surgery.

The difficulty of creating new, unambiguous, pertinent multiple-choice questions of a level appropriate to medical students implies that examinations must be compiled from a limited number of items. Furthermore, it is impossible to keep used questions inaccessible to all subsequent students. This study was undertaken to determine if these realities are compatible with examinations that are both valid and reliable. A pool of 480 multiple-choice questions was distributed to 232 students during the surgical clerkship. At the conclusion of each quarter, a 120-item multiple-choice examination that consisted of entirely new questions was administered (group I). These 960 questions were then made available to the next group of 218 students; each subsequent examination consisted of 50% new questions and 50% questions repeated verbatim from the publicized pool (group II). With the available pool now increased to 1200, the next examination consisted of 20% new and 80% repeat questions (group III). Reliability (internal consistency) was measured by the Kuder-Richardson-21 formula. Validity was measured by correlation between the multiple-choice examination and the average score of evaluations of each student by two oral examinations and five faculty members. Despite the expected increase in mean examination score, there is loss of neither reliability nor validity by inclusion of even 80% of items repeated from a large pool of multiple-choice questions that have been distributed to the students. Hence, instead of adding irrelevant, trivial, or inappropriate items or trying in vain to hide old examinations from new students, simple preparation of examinations from a large pool of questions is recommended. To insure fairness to all students, this pool should be made public knowledge.

Pitfalls in evaluating the surgical student.

One hundred five students in our surgical clerkship were evaluated independently by two faculty members, a chief resident, a written multiple-choice examination, and two oral examinations. Faculty and chief resident evaluations included a written explanation and a score from 1 (honors) to 5 (failing). Oral and written examination scores were adjusted to the same numerical scale. Correlation coefficients (r) and probabilities (P) by the t test were calculated to determine validity of the components of the students' grades. In comparison with the oral examination, written examination, and final mean score, the chief residents' evaluations exhibited a validity significantly lower than that of both faculty groups (P less than 0.01). This finding was associated with the following differences in content of associated written evaluations. Residents were more likely to mention "skills" or "technique" (P less than 0.001) and less likely to comment on "logic," "judgment," or "reasoning" (P less than 0.001). Comments concerning "appearance," "enthusiasm," "diligence," and "motivation" were not significantly different among these groups. Experience gained as a member of a surgical teaching faculty or by an affiliation with a teaching program resulted in a greater tendency to focus on thought processes and less emphasis on technical factors in the evaluation of the student on a surgical rotation. Education of surgical house staff must include elucidation of appropriate criteria by which students should be judged. A welcome by-product might be a shift in emphasis in surgical education from a myriad of technical details to a logical approach to diagnosis and treatment.

Determining the content of a surgical curriculum.

The purpose of undergraduate surgical education is to prepare the student for both the residency and eventual practice of medicine. To help determine the surgical knowledge and skills that would eventually the useful to the student, we conducted a survey of residents in training, physicians in practice, and surgical educators (department chairpersons and clerkship directors). Members of the Curriculum Committee of the Association for Surgical Education developed a questionnaire in which the respondents were asked to grade the functional importance of 84 areas of knowledge and 46 skills (0 = unnecessary, 3 = proficiency necessary). Using a modified Delphi technique to collect information, we sent the questionnaire to eight medical school graduation classes of 1975 (730 persons) and 1980 (776 persons) and all department chairpersons and/or clerkship directors (179). The results of the survey (46% response) revealed considerable agreement about the importance of certain skills and areas of knowledge, enabling us to rank order skills and knowledge based on mean responses (0.0 to 3.0). Physicians in practice, residents, and educators believed that certain areas of knowledge (e.g., acute abdominal problems, appendicitis, shock, cancer of the breasts) and skills (e.g., history taking and physical examination, gowning, suture removal) were very important (greater than 2.250, while other areas of knowledge (e.g., transplantation, liver abscess, soft tissue sarcomas) and skills (e.g., insertion of Swan-Ganz catheter, abdominal paracentesis, cricothyroidotomy) were less important (less than 1.3). This approach allows us to assign priorities to areas of knowledge and skills when determining curriculum content and to include functional criteria when developing educational objectives.

Effects of hypoxia and hyperoxia on progression of intimal healing.

To assess the effect of changes in inspired oxygen concentration on intimal healing, the aorta was stripped by a single passage of an inflated embolectomy catheter in 34 rabbits. Each then was maintained in a controlled-atmosphere cage with a normobaric oxygen concentration of 14%, 21%, or 40% for up to ten days. Although after six months all animals showed nearly normal aortic healing, the progression of healing was considerably different. Hypoxia appears to result in prolonged platelet adherence, exaggerated medial proliferation, and aberrant migration. Hyperoxia appears to allow a more orderly intimalization. An aberrant healing process secondary to tissue hypoxia when combined with exacerbating factors may be important in producing the unfavorable result in vascular surgery.

Evaluation of the student: improving validity of the oral examination.

Medical students completing a surgical clerkship were scored independently by faculty members, a chief resident and a written multiple-choice examination. In group I, an oral examination was administered by two faculty members together in one room, while in group II, the examiners were in separate rooms. The average oral examination grade correlated with none of the other facets of the student evaluation in group I, but did so for most parameters in group II. The correlation coefficient between the oral examination and mean grade became significant, however, for oral examinations in which five or more core topics were covered. It is concluded that even with limited professional resources, changes in the method of administering an oral examination can increase its validity.

A clinical experience with the NCGT graft.

A comparison of 130 grafts done in 101 patients included 47 veins, 25 Johnson & Johnson dialdehyde-starch-tanned collagen prostheses, and 58 NCGT grafts that had been followed for a 40-month period. This study had documented the fact that in spite of frequent poor runoff, a useful result is provided by the NCGT graft apparently due in part to its built-in nonthrombogenic structure providing a cumulative patency of 73%. The patency rate was even superior with venous bypasses. Therefore, we still feel that the autogenous vein provides the most useful bypass conduit available in vascular reconstruction. In situations where a vein could not be used or was not available the NCGT graft offers an equally useful nonthrombogenic surface to maintain prolonged patency. Thus, collagen appropriately modified can provide a useful prosthesis in vascular reconstruction.

Skin wound closure. The effect of various wound closure methods on susceptibility to infection.

A continuous subcuticular polyglycolic acid suture with buried knots protected by a paint-on plastic dressing is shown to be resistant to surface contamination with Staphylococcus aureus in mice and is suggested to be superior to percutaneous skin sutures in infectability and to a tape closure in security.

Alleviation of autotransfusion-induced haematological damage by corticosteroids.

Thrombocytopenia and haemolysis in intraoperative autotransfusion result mainly from extravascular tissue contact and therefore are not correctable by mechanical improvements in the autotransfusion apparatus. Instead, attention must be directed towards prevention of blood 'recognition' of extravascular tissue or stabilization of blood components against this damage. Methylprednisolone is shown to be effective in alleviating red cell and platelet damage induced by intraoperative autotransfusion in the canine model.

In vitro and in vivo evaluations of dacron velour and knit prostheses.

Dacron velour and knit prostheses were compared with respect to long-term patency when used as canine aortic implants. These grafts were rated, according to the average numerical value of six equally weighted criteria, in decreasing order of performance: velour I, velour II, circular knit III, velour IV, circular knit V, warp-knit VI, warp-knit VII and VIII, warp-knit IX and warp-knit X. In general, compacting and crimping methods using halogenated hydrocarbons produced the least successful grafts. Grafts of identical brand but compacted and crimped by different methods exhibited different patencies. No true healing of the grafts was observed. Layered deposits of inner fibrous capsule were formed at rates and thicknesses characteristic for each type of graft employed. A functioning Dacron femoral-popliteal bypass removed from a human after 9 months exhibited inner and outer fibrous capsules similar to those from canine implants.

Results of renal transplantation using pediatric cadaver donors.

In order to determine the results of transplantation using pediatric cadaver donors, a retrospective analysis of a series of 502 renal transplant recipients was carried out. Methods of procurement, preservation, recipient selection, and immunosuppressive regimen were similar for all patients. Sixty-five recipients were approximately equally divided into three groups whose donors were younger than 5 years of age, 6 to 10 years old, and 11 to 15 years. These three groups then were compared with each other and to a randomly selected representative group of recipients whose donors were adults (16 years or older) for the following parameters: actuarial graft and patient survival, causes of graft failure and patient death, level of serum creatinine in currently functioning grafts, and recipient age. There were no statistically significant differences between groups for any parameter except that the mean age of recipients was approximately 16 years for the donors up to 5 years of age and was between 31 and 36 years for the other donor age groups (P = 0.01). These results support the contention that brain-dead pediatric patients of any age should be considered to be potential cadaveric kidney donors. Exclusion of these patients is very wasteful and also is unnecessary since results of transplantation equal to those obtained with adult donors can be expected. Technical graft failures should not be more frequent than with adult kidneys, and there is no need to modify the basic surgical technique for small kidneys in order to achieve this.

A suggested classification and reappraisal of mortality statistics for ruptured atherosclerotic infrarenal aortic aneurysms.

A retrospective review of 80 ruptured infrarenal abdominal aortic aneurysms with classification of the patients into clinical groups based upon the findings at laparotomy was undertaken. Patients with small hematomas confined to the area of rupture were uniformly salvaged. Those with free intraperitoneal blood almost invariably died. Intermediate groups had mortalities od 37.5 and 62.5 per cent. It is concluded that operative mortality is related to the clinical group to which the patient belongs. Attention must be focused upon the potentially salvageable intermediate groups, with regard to early laparotomy and prompt, effective proximal and distal control of the aorta before entering the retroperitoneal hematoma. Major improvements in survival have occurred with smaller ruptures but little has been achieved with larger ruptures during the past 25 years.

Etiology of catheter-associated sepsis. Correlation with thrombogenicity.

A series of 94 central venous catheters was observed at removal for gross evidence of intraluminal or surface thrombus deposition. All those that were later found to have positive cultures had been noted to display thrombus formation, while catheters having negative cultures were usually free of thrombus. Devices made of a relatively nonthrombogenic material (ethylene acrylic acid) were also relatively free of bacterial contamination.

Intramural lymphatic cyst of bovine heterograft.

An intramural lymphatic cyst of a bovine heterograft is described. This previously unreported complication presented as a pulsatile mass in the thigh of an 84-year-old woman who had undergone vascular reconstruction 12 months previously. The clinical presentation, operative findings, and pathological findings are described, and the management of the case is discussed.