Hans Troidl

Probability of adverse events that have not yet occurred: a statistical reminder.

The probability of adverse and undesirable events during and after operations that have not yet occurred in a finite number of patients (n) can be estimated with Hanleys simple formula, which gives the upper limit of the 95% confidence interval of the probability of such an event: upper limit of 95% confidence interval = maximum risk = 3/n (for n > 30). Doctors and surgeons should keep this simple rule in mind when complication rates of zero are reported in the literature and when they have not (yet) experienced a disastrous complication in a procedure.

Unacceptable results of the Mayo procedure for repair of abdominal incisional hernias

OBJECTIVE To evaluate the current practice of incisional hernia repair in Germany and analysis of the results of the Mayo duplication technique done in our hospital over a 10-year period. DESIGN Nationwide survey, retrospective analysis. SETTING University department, Germany. SUBJECTS Survey of most surgical departments and of 114 patients with 135 incisional hernias in our unit. INTERVENTION Mayo duplication repair incisional hernias. MAIN OUTCOME MEASURES Common practice, recurrence rates, quality of life. RESULTS The Mayo overlap is the preferred technique in most surgical departments. The estimated failure rates (12% or less) in general practice are grossly underestimated. In our hospital the recurrence rate after Mayo duplication repair was 61/114 (54%) during a follow up time of 5.7 years with a follow-up-rate of 84%. Univariate and multivariate analyses failed to identify any predisposing factors. All patients with incisional hernias had limitations their physical function. CONCLUSIONS The widely used Mayo procedure leads to unacceptable results for repair of incisional hernias and other techniques should be evaluated and used more often. Repair of an incisional hernia does not improve overall quality of life.

Laparoscopic Cholecystectomy for Acute Cholecystitis: Is It Really Safe?

Abstract. The prospectively collected data from 530 cholecystectomies performed in a university clinic from October 1989 to March 1991 were analyzed after 1 to 3 years of follow-up. The aim of this study was to compare the results of laparoscopic cholecystectomy (LC) for acute cholecystitis with that for routine symptomatic gallbladders. The preoperative, intraoperative, and postoperative parameters of 424 routine (noninflamed) LCs and 54 LCs for acutely inflamed gallbladders were compared under the “intention to treat” principle. Operating time was longer in the inflamed group (median 97 minutes versus 75 minutes;p < 0.0001). Significantly more adhesions (20% versus 8%), more blood loss (48% versus 19%), a higher incidence of bile spillage (28% versus 12%), and lost stones (19% versus 8%) were encountered in patients with acute cholecystitis. Common bile duct (CBD) injuries were also more frequent in that group (5.5% versus 0.2%;p = 0.005). The rate of conversion to open surgery was higher than with routine LCs (13% versus 4%). There were two deaths in the routine LC group and none in the acutely inflamed group. There was no difference in postoperative pain intensity or postoperative fatigue according to visual analog scale measurements. Patients with acute cholecystitis stayed only 1 day longer (median 4 days versus 3 days) in hospital. The quality of life scores indicate return to almost normal values by the 14th postoperative day. Long-term follow-up (1–3 years) did not reveal any delayed clinical adverse effects. In summary, LC for inflamed gallbladders has a higher conversion rate than LC for routine symptomatic gallbladders. If successfully performed, it has definite benefit for the patient in terms of better postoperative recovery. The trade-off is that the risk of CBD injury is significantly higher.

Mental Training in Surgical Education: A Randomized Controlled Trial

Objective:To evaluate the impact of a cognitive training method on the performance of simulated laparoscopic cholecystectomy in laparoscopic training courses. Summary Background Data:Surgeons are like professional sportsmen in that they have to be able to perform complicated, fine-motor movements under stressful conditions. Mental training, systematically and repeatedly imagining a movements performance, is a well-established technique in sports science, and this study aimed to determine its value in training surgeons. Methods:A total of 98 surgeons undergoing basic laparoscopic training participated in a randomized controlled trial; 31 received additional mental training, 32 additional practical training, and 35 received no additional training (control group). All used a Pelvi-Trainer simulator to perform laparoscopic cholecystectomy at baseline and follow-up, after any additional intervention. We used a modified Objective Structured Assessment of Technical Skills (OSATS) instrument to assess performance. Principle outcome variables were the OSATS task-specific checklist (11 procedural steps, scored as correctly [1] or wrongly [0] performed) and the global rating scale (an overall performance evaluation, scored 1–5). Results:Improvement in the task-specific checklist score between baseline and follow-up differed significantly between groups (P = 0.046 on ANOVA). Least significant difference tests yielded differences between the mental and practical training groups (P = 0.024) and between the mental training and control groups (P = 0.040), but not between the practical training and control groups (P = 0.789). Paired Student t test showed that performance at follow-up was significantly better in the mental training and control groups (mental training group, P = 0.001; control group, P = 0.018) but not the practical training group (P = 0.342). There were no significant intergroup differences in global rating scale results. Conclusion:Additional mental training is an effective way of optimizing the outcomes of further training for laparoscopic cholecystectomy. It is associated with fewer costs and with better outcomes in some crucial assessment scales than additional practical training.

Trauma score systems: Cologne Validation Study

BACKGROUND Most standard trauma score systems have been developed and validated in the United States. However, trauma differs between the United States and Germany. This prospective study tested the validity of eight current trauma scoring systems (Glasgow Coma Scale, Trauma Score, Revised Trauma Score, Injury Severity Score, TRISSTS, TRISSRTS, Prehospital Index, Polytraumaschluessel) in 612 patients in Cologne. METHODS Between January 1, 1987, and December 31, 1987, 2,136 trauma related emergencies were seen by emergency physicians in the field. All trauma patients with a Trauma Score below 16 and a random sample of 10% of patients with a Trauma Score of 16 were included in the study (n = 625). Follow-up was successfully completed for 612 patients (97%). Their hospital outcome was correlated with their individual score result. RESULTS All trauma score systems under study showed high accuracy rates. TRISSRTS and TRISSTS performed best with values of above 0.97 for the area under the receiver operating characteristics curve. CONCLUSION We conclude that the standard trauma score systems are valid tools for patient classification and support TRISSRTS as the international reference score system for the assessment of injury severity. This validation will allow comparisons between different trauma care systems.

Protective effect of heat shock pretreatment with heat shock protein induction before hepatic warm ischemic injury caused by Pringle's maneuver

BACKGROUND Induction of heat shock proteins is thought to have a > cytoprotective effect against environmental stress and to result in a better ischemic tolerance. The protective ability of heat exposure and heat shock protein 72 (HSP 72) induction before warm ischemia caused by Pringles maneuver was evaluated in rats. METHODS Heat exposed rats (HS) were compared with control animals (C). The gene expression (messenger RNA) of HSP 72 and HSP 72 were detected by Northern and Western blot analyses. During 40 minutes of in situ reperfusion, liver energy metabolism and levels of standard liver enzymes were evaluated. The survival rate was determined after postoperative day 7. RESULTS After heat exposure and recovery, messenger RNA of HSP 72 and HSP 72 can be detected strongly in HS group but not in C group. During reperfusion HS group exhibited a significantly (p < 0.01) improved energy metabolism, and the release of liver enzymes was significantly (p < 0.001) reduced compared with C group. Seven-day survival rate was 100% in HS group but at 50% was significantly impaired (p < 0.05) in C group. CONCLUSIONS Heat exposure associated with HSP induction has a significant protective effect against warm ischemic liver injury, which results in a relevant improvement of survival rate.

Second Step: Testing—Outcome Measurements

Despite worldwide enthusiasm for endoscopic surgery, this new technology is now on the top of McKinlays “product life circle curve.” Critical questions are being asked about its benefits and burdens, but the concepts applied and the methodologies used for technology assessment are in a similar position as endoscopic surgery and need a critical evaluation. (1) There are incorrect and outdated concepts for the scientific basis of surgery (surgical theory) including the basic sciences involved; biomedicine still dominates, but assessment of outcome after operations is no longer possible without clinical epidemiology and social psychology. (2) Based on an outdated scientific theory for surgery, an outdated concept of disease is still propagated. It is denoted as mechanical and is based solely on biomedicine. Human subjects are reduced to biologic machines, and outcomes measurement excludes most dimensions of functioning and well-being. To achieve a valid result for outcome measures, a hermeneutic approach must be combined with the mechanical approach. (3) Based on an outdated model of disease, the outcomes used in endoscopic surgery rely too much on traditional measures, such as mortality rate, complication rate, hospital stay, and especially an endless list of biochemical mediators. Their alterations during the perioperative period have not yet been shown to be related to clinical or hermeneutic outcomes. A new method of assessment for clinical trials in endoscopic surgery and for other surgical problems is outlined, such as for surgical infections and for surgical oncology. It includes an index of recovery and objective health status assessed by the doctor, a quality-of-life self-report by the patient, and the true endpoint concept as a critical weighting of both types of outcome by patients and doctors.

Color Duplex Sonography: Diagnostic Tool in the Differentiation of Inguinal Hernias

We investigated the accuracy of combined physical and color duplex sonographic examination in the preoperative distinction of direct inguinal hernias. After a learning period (with 15 male patients) 50 consecutive male patients who underwent surgery in our department for small inguinal hernias between July 1995 and April 1996 were examined. On color duplex examination the relationship between the hernial sac and the inferior epigastric artery was determined. Intraoperative results were then compared with the data obtained preoperatively. The sensitivity of our physical examination for direct inguinal hernia was 75% with a specificity and a positive predictive value of 100% and a negative predictive value of 80%. The identification of the IEA as well as the hernial sac was successful on every color duplex sonographic study. The sensitivity of color duplex sonography for direct inguinal hernias amounted to 90%, the specificity was 86%, the positive predictive value was 78%, and the negative predictive value was 89%. Both combined hernias found intraoperatively had not been detected either by physical examination or by color duplex examination. Correspondence of results obtained by physical examination and color duplex examination leads to high accuracy in the diagnosis of direct inguinal hernias.

CO2 Pneumoperitoneum: What We Know and What We Need to Know

The development of the laparoscopic technique in surgery was so overwhelming that scientific evaluation could not keep in step. While investigators were still discussing the effects of the pneumoperitoneum on the healthy organism, laparoscopy was already performed in patients with an acute abdomen due to trauma or disease. Therefore, there is an urgent need of further experimental and clinical studies with relevant endpoints to gain external evidence concerning the benefits of diagnostic or therapeutic laparoscopy for critically ill patients. In experiments with pigs we have shown that even in a healthy organism perfusion and energy metabolism of the small bowel is impaired by a pneumoperitoneum with carbon dioxide. Under the conditions of a systemic inflammatory response syndrome induced by infusion of endotoxin, the negative effects of the pneumoperitoneum were significantly amplified. Furthermore, we found that the increased intracranial pressure as caused by a head injury was further enhanced during a pneumoperitoneum but not by the alternative method of mechanical wall retraction. The current literature dealing with the effects of a pneumoperitoneum in critically ill patients is still controversial. Our data support the results of those authors who hold the opinion that creating a pneumoperitoneum in patients with acute abdominal problems means an additional serious burden that in single cases may lead to a disaster. As evidence is lacking, the current extension of laparoscopy into the field of intensive care medicine is still a human experiment that must be performed with high responsibility, extensive monitoring, and according to the rules of a clinical study.

Biomechanical and morphological types of the linea alba and its possible role in the pathogenesis of midline incisional hernia.

OBJECTIVE To review the tensile strength of the different histological types of fibres in the linea alba and correlate the anatomical features of the anterior abdominal wall with the tensile strength of the linea alba to see whether the tensile strength of the linea alba might contribute to the development of midline incisional hernias. DESIGN Laboratory study. SETTING University hospital, Germany. SUBJECTS 46 cadavers in part one, and 9 freshly frozen and 38 formalin-fixed cadavers in part two. INTERVENTIONS In the first part of the study the histological examination was by binocular dissection microscopy, magnification x10, but this was not sufficiently reproducible so in the second part we used an Olympus BX50 microscope, magnification x20, and Optimas 5.22 picture processing software. Tensile strength was measured using a Loosenhausen ZHP 1-6 tensiometer. MAIN OUTCOME MEASURES Correlation between anatomical features and tensile strength. RESULTS The method used in part one of the study failed to differentiate between the three types of fibres in the linea alba (weak, intermediate, and compact). In the second part of the study we found that the fibres were irregular, with no systematic crossing of the fibres of the aponeurosis. There was a significant correlation between the thickness and density of fibres in the linea alba and its tensile strength (r = 0.9). The thickness of fibres ranged from 21.9-38.2 microm and the density from 48% to 90%. The tensile strength ranged from 3-25 kp. CONCLUSION A combination of low density and thin fibres in the linea alba could be a predisposing factor for development of midline incisional hernias