Christopher W. Snyder

The relationship of blood product ratio to mortality: survival benefit or survival bias?

BACKGROUND Recent studies show an apparent survival advantage associated with the administration of higher cumulative ratios of fresh frozen plasma (FFP) to packed red blood cells (PRBC). It remains unclear how temporal factors and survival bias may influence these results. The objective of this study was to evaluate the temporal relationship between blood product ratios and mortality in massively transfused trauma patients. METHODS Patients requiring massive transfusion (>10 units of PRBC within 24 hours of admission) between 2005 and 2007 were identified (n = 134). In-hospital mortality was compared between patients receiving high (>1:2) versus low (<1:2) FFP:PRBC ratios with a regression model, using the FFP:PRBC ratio as a fixed value at 24 hours (method I) and as a time-varying covariate (method II). RESULTS The FFP:PRBC ratio for all patients was low early and increased over time. Sixty-eight percent of total blood products were given and 54% of deaths occurred during the first 6 hours. Using method I, patients receiving a high FFP:PRBC ratio (mean, 1:1.3) by 24 hours had a 63% lower risk of death (RR, 0.37; 95% CI, 0.22-0.64) compared with those receiving a low ratio (mean, 1:3.7). However, this association was no longer statistically significant (RR, 0.84; 95% CI, 0.47-1.50) when the timing of component product transfusion was taken into account (method II). CONCLUSIONS Similar to previous studies, an association between higher FFP:PRBC ratios at 24 hours and improved survival was observed. However, after adjustment for survival bias in the analysis, the association was no longer statistically significant. Prospective trials are necessary to evaluate whether hemostatic resuscitation is clinically beneficial.

Long-Term Follow-Up of Technical Outcomes for Incisional Hernia Repair

BACKGROUND Incisional hernia repair (IHR) is plagued by high recurrence rates and lack of long-term outcomes data to guide repair technique. Mesh repair reduces recurrence rates but lacks standardization of technique. We investigated long-term outcomes of elective IHR, focusing on technical predictors of recurrence. STUDY DESIGN This retrospective multicenter cohort study included elective IHR performed at 16 Veterans Affairs hospitals between 1997 and 2002. Hernia characteristics and operative details were abstracted from operative notes, and chart review was performed to identify recurrence and complications. Kaplan-Meier curves and Cox regression models were used to evaluate the effects of hernia characteristics and operative technique on recurrence. RESULTS There were 1,346 elective IHRs, of which 22% were recurrent hernias. Repair technique was primary suture in 31%, open inlay or onlay mesh in 30%, open underlay in 30%, and laparoscopic in 9%. At median follow-up of 73.4 months, there were 383 recurrences (28.5%), 23 mesh removals (1.7%), and 7 enterocutaneous fistulas (ECF) (0.5%). On Cox regression modeling with adjustment for hernia and Veterans Affairs site characteristics, the effectiveness of mesh varied by position. Compared with suture repair, laparoscopic (hazard ratio = 0.49; 95% CI, 0.28-0.84) and open underlay mesh repair (hazard ratio = 0.72; 95% CI, 0.53-0.98) substantially reduced the recurrence risk, but onlay or inlay mesh repair did not. Mesh position did not affect mesh removal or ECF rates. CONCLUSIONS Underlay technique, either laparoscopic or open, for mesh implantation during elective IHR substantially reduces the risk of recurrence, without increasing the risk of serious mesh infection or ECF.

Predictors of mesh explantation after incisional hernia repair

BACKGROUND Prosthetic mesh used for incisional hernia repair (IHR) reduces hernia recurrence. Mesh infection results in significant morbidity and challenges for subsequent abdominal wall reconstruction. The risk factors that lead to mesh explantation are not well known. METHODS This is a multisite cohort study of patients undergoing IHR at 16 Veterans Affairs hospitals from 1998 to 2002. RESULTS Of the 1,071 mesh repairs, 55 (5.1%) had subsequent mesh explantation at a median of 7.3 months (interquartile range 1.4-22.2) after IHR with permanent mesh prosthesis. Infection was the most common reason for explantation (69%). No differences were observed by the type of repair. Adjusting for covariates, same-site concomitant surgery (hazard ratio [HR] = 6.3) and postoperative surgical site infection (HR = 6.5) were associated with mesh explantation. CONCLUSIONS Patients undergoing IHR with concomitant intra-abdominal procedures have a greater than 6-fold increased hazard of subsequent mesh explantation. Permanent prosthetic mesh should be used with caution in this setting.

Multiple Preoperative Endoscopic Interventions Are Associated with Worse Outcomes After Laparoscopic Heller Myotomy for Achalasia

BackgroundThe effect of preoperative pneumatic dilation or botulinum toxin injection on outcomes after laparoscopic Heller myotomy (LHM) for achalasia is unclear. We compared outcomes in patients with and without multiple preoperative endoscopic interventions.MethodsThis cohort study categorized achalasia patients undergoing first-time LHM by the number of preoperative endoscopic interventions: zero or one intervention vs. two or more interventions. Outcomes of interest included surgical failure (defined as the need for re-intervention), gastrointestinal symptoms, and health-related quality of life. Logistic regression modeling was performed to determine the independent effect of multiple preoperative endoscopic interventions on the likelihood of surgical failure.ResultsOne hundred thirty-four patients were included; 88 (66%) had zero to one preoperative intervention, and 46 (34%) had multiple (more than one) interventions. The incidence of surgical failure was 7% in the zero to one intervention group and 28% in the more than one intervention group (p < 0.01). Greater improvements in gastrointestinal symptoms and health-related quality of life were seen in the zero to one intervention group. On logistic regression modeling, the likelihood of surgical failure was significantly higher in the more than one intervention group (odds ratio = 5.1, 95% confidence interval 1.6–15.8, p = 0.005).ConclusionsMultiple endoscopic treatments are associated with poorer outcomes and should be limited to achalasia patients who fail surgical therapy.

Proficiency-Based Laparoscopic and Endoscopic Training With Virtual Reality Simulators: A Comparison of Proctored and Independent Approaches

BACKGROUND Virtual reality (VR) simulators for laparoscopy and endoscopy may be valuable tools for resident education. However, the cost of such training in terms of trainee and instructor time may vary depending upon whether an independent or proctored approach is employed. METHODS We performed a randomized controlled trial to compare independent and proctored methods of proficiency-based VR simulator training. Medical students were randomized to independent or proctored training groups. Groups were compared with respect to the number of training hours and task repetitions required to achieve expert level proficiency on laparoscopic and endoscopic simulators. Cox regression modeling was used to compare time to proficiency between groups, with adjustment for appropriate covariates. RESULTS Thirty-six medical students (18 independent, 18 proctored) were enrolled. Achievement of overall simulator proficiency required a median of 11 hours of training (range, 6-21 hours). Laparoscopic and endoscopic proficiency were achieved after a median of 11 (range, 6-32) and 10 (range, 5-27) task repetitions, respectively. The number of repetitions required to achieve proficiency was similar between groups. After adjustment for covariates, trainees in the independent group achieved simulator proficiency with significantly fewer hours of training (hazard ratio, 2.62; 95% confidence interval, 1.01-6.85; p = 0.048). CONCLUSIONS Our study quantifies the cost, in instructor and trainee hours, of proficiency-based laparoscopic and endoscopic VR simulator training, and suggests that proctored instruction does not offer any advantages to trainees. The independent approach may be preferable for surgical residency programs desiring to implement VR simulator training.

Effect of Mesh Type and Position on Subsequent Abdominal Operations after Incisional Hernia Repair

BACKGROUND The frequency of subsequent abdominal operations (SAO) and complications attributable to earlier ventral incisional hernia repair (VIHR) are unknown. We examined the effect of repair type and technique on the difficulty and complications of subsequent surgery. STUDY DESIGN A cohort of VIHRs at 16 Veterans Affairs hospitals between 1998 and 2002 was examined for postrepair abdominal operation by chart review. The primary independent variable was type and technique of the index VIHR: suture or mesh repair stratified by mesh type and position in relation to abdominal wall musculature. Subsequent surgery characteristics including operative time, inadvertent enterotomy, mesh removal, and length of postoperative stay were determined by chart review. Regression modeling was used to adjust for potential confounding variables. RESULTS At a median of 80 months after VIHR in 1,444 patients, 366 (25.3%) experienced SAO. Nearly two-thirds of these involved rerepair of the VIHR with or without a concomitant procedure. Mesh removal was significantly more likely in expanded polytetrafluoroethylene repairs as compared with polypropylene repairs, regardless of technique (odds ratio = 3.6; p = 0.01). On multivariable regression modeling, polypropylene underlay (p = 0.03) and inlay (p = 0.001) and absorbable/biologic mesh (p = 0.05) significantly increased operative time for SAO. Repair type, mesh type, or position had no significant effect on risk of inadvertent enterotomy during the SAO (p≥0.27). CONCLUSIONS Subsequent abdominal operations after VIHR are common. Underlay or inlay polypropylene mesh increases SAO operative time, but there was no increased risk of intestinal injury. Earlier repair with expanded polytetrafluoroethylene did not increase operative time, but there was equivalent risk for intestinal injury and increased risk for mesh removal.

Primary sternal plating to prevent sternal wound complications after cardiac surgery: early experience and patterns of failure.

Sternal closure with rigid titanium plates (primary sternal plating) may reduce sternal wound complications in high-risk patients. We began performing primary sternal plating for the following indications: obesity, manual laborer, osteoporotic sternum, or intraoperative transverse sternal fracture. Patients receiving plate closure were compared to a risk-matched control group receiving wire closure. Outcomes of interest were postoperative length of stay and sternal wound complications [sterile dehiscence or deep sternal wound infection (DSWI)]. Wound complications were classified by time of occurrence as early (<or=30 days postoperation) or late (>30 days postoperation). Of 445 total cardiac cases during the 5-year study period, 129 (29%) met inclusion criteria. The plate group (n=30) and wire group (n=99) were generally well-matched in terms of risk factors. Postoperative length of stay was significantly shorter in the plate group (median 7 vs. 8 days, P=0.023). No early sternal wound complications occurred in the plate group, compared to 12 (12%) in the wire group (P=0.067). The incidence of late sternal wound complications was 10% in both groups (P=1.0). Primary sternal plating appears to provide benefits over wire closure during the early postoperative period, but may not prevent late wound complications in patients with osteoporosis or extreme obesity.

Hospital-level variability in incisional hernia repair technique affects patient outcomes.

BACKGROUND Mesh placement during ventral incisional hernia repair has been shown to result in superior outcomes; however, significant variation persists in the adoption of this technique. We performed a multi-institutional study to understand how variation in surgical technique influences outcomes. METHODS This study is a retrospective, facility-level analysis of incisional hernia repairs performed at 16 veterans administration medical centers between 1997 and 2002. Operative notes and a postoperative course were physician-abstracted from the medical record. Hospital rates for the type of hernia repair, mesh placement, and recurrence were calculated. Spearmans correlation and generalized linear models were performed. RESULTS A total of 1,612 incisional hernia repairs with a median follow-up of 66.2 months were included in the study. The mean rate of mesh implantation was 63.7% but ranged from 37.5% to 90%. The 5-year recurrence rate was 25.6% and ranged from 16.0% to 38.4%. The rate of mesh use for the incisional hernia repair at the hospital level was associated significantly with the hospital recurrence rate for all cases (R(2) = .27; P = .04) and elective cases (R(2) = .31; P = .02). For every 10% increase in the rate of mesh placement, a corresponding 3.1% decrease was noted in the recurrence rates (P = .001). The hospital rate of mesh use was not associated significantly with rates of complications or patient satisfaction. CONCLUSION Hospitals that adopted a higher rate of mesh repair for incisional hernia repairs had lower recurrence rates. These data support that the efficacy of mesh repair previously proven in clinical trials is highly translatable to effective practice in the field. Continued studies on the attributable risk of complications to mesh placement are ongoing.

A meta-analysis of B-mode ultrasound, Doppler ultrasound, and computed tomography to diagnose pediatric ovarian torsion.

PURPOSE Ovarian torsion (OT) is a true surgical emergency that requires prompt diagnosis and therapy. There are conflicting reports on the accuracy of different imaging modalities for OT. In this study, we performed a meta-analysis of all the published studies on B-mode ultrasound (US, morphological criteria), Doppler US (DUS, flow criteria), and computed tomography (CT) for the diagnosis of OT. Methods: The medical literature from 1987 to 2013 was searched for studies that evaluated US, DUS, CT, or combination of these techniques to diagnose OT in children using PubMed/MEDLINE database. The studies were screened and included if the quality criteria were met. Data were extracted using a standardized form. Reported sensitivities and specificities were pooled with 95% confidence intervals using a RevMan version 5.1 software (The Cochrane Collaboration, Oxford, United Kingdom). RESULTS A total of 18 US studies with 716 combined patients were included, along with 15 DUS studies comprising of 1,021 patients, and 5 CT studies with a total of 107 patients. All studies reported sensitivities, while only few selected studies also reported specificities. Using morphological criteria on B-mode US (including absolute or relative ovarian size, echotexture, location, and configuration) yielded high sensitivity and specificity (average 92 and 96%, respectively); DUS was highly specific, but lacked sensitivity, while CT was the least sensitive test. CT specificities could not be calculated from the available data. CONCLUSION This study found considerable variability of the reported sensitivities and specificities for the diagnosis of OT across all evaluated imaging modalities. Interestingly, B-mode US was the most sensitive and specific examination to detect OT. Some authors reported high diagnostic accuracy of DUS as well, but these findings have not been universally reproduced. CT had low overall sensitivity and is not recommended for the workup of suspected OT.

Paediatric trauma on the Last Frontier: an 11-year review of injury mechanisms, high-risk injury patterns and outcomes in Alaskan children

Background Paediatric trauma system development in Alaska is complicated by a vast geographic coverage area, wide regional variations in environment and culture, and a lack of available published data. Objective To provide a detailed description of paediatric trauma mechanisms, high-risk injury patterns and outcomes in Alaska. Design This retrospective study included all children aged 17 years or younger in the State of Alaska Trauma Registry database admitted with traumatic injury between 2001 and 2011. Each injury record was reviewed individually and assigned a mechanism based on Centers for Disease Control E-codes. Geographic definitions were based on existing Emergency Medical Services regions. Mechanisms were compared by geographic region, patient demographics, injury characteristics and outcome. Subgroup analysis of fatal injuries was performed to identify causes of death. Results Of 5,547 patients meeting inclusion criteria, the most common mechanisms of injury were falls (39%), motor vehicle collisions (10%) and all-terrain vehicle (ATV) accidents (9%). The overall case fatality rate was 2%. Mechanisms with the greatest risk of death were gunshot wounds (21%), pedestrians struck by motorized vehicles (9%) and motor vehicle collisions (5%). These 3 mechanisms accounted for 15% of injuries but 60% of deaths in the overall cohort. Injury patterns involving combined central nervous system (CNS) and torso injuries were unusual but especially lethal, occurring in 3% of patients but carrying a case fatality rate of 18%. Although the distribution of mechanisms was generally similar for each geographic region, ATV and snowmobile injuries were significantly more common in remote areas (23% remote vs. 7% non-remote, p < 0.0001). Conclusions Mechanisms of paediatric trauma in Alaska have widely varying impacts on outcome and show some variation by region. Highest-risk mechanisms include gunshot wounds and motorized vehicle-related accidents. Prevention efforts should give special attention to CNS injury prevention, ATV and snowmobile safety in remote areas, and optimization of management of multisystem trauma. Further studies should investigate predictors of outcome in greater detail.