Biomedical subjects

J Wayne Meredith

Publications and source records attributed to J Wayne Meredith.

30 records · Page 2Linked to original sources

PubMed2003

Complex blunt aortic injury or repair: beneficial effects of cardiopulmonary bypass use.

OBJECTIVE: To compare the outcomes and associated morbidity in patients with blunt aortic injury (BAI) repaired using cardiopulmonary bypass versus no bypass. Special consideration is given to the influence of bypass in the outcome of complex injuries or repair circumstances. SUMMARY BACKGROUND DATA: There are conflicting data concerning the utility of bypass techniques in the operative management of BAI, and controversy over the subject persists. During the last decade, surgeons at the authors' institution have undergone a change in philosophy concerning management of these injuries and began almost exclusively using cardiopulmonary bypass for the repair in 1996. This project explores the effects of this change in the management of BAI. METHODS: The records of all patients with BAI admitted to a level 1 trauma center over a period of 12 years were reviewed for demographics, injury characteristics, operative technique, and outcome. The bypass group was compared to the no bypass group with respect to morbidity and mortality. Those with a complex injury or repair (CI/R) were examined as a subgroup. CI/R was defined as the presence of an injury with extension proximal to the subclavian artery, involvement of branch vessels, or requirement of maneuvers interfering with anastomosis construction, such as cardiac massage. RESULTS: From January 1, 1990, to December 31, 2001, 91 patients were admitted to Wake Forest University Baptist Medical Center with BAI. Sixty-five of these underwent operative repair. Sixty (32 no bypass, 28 bypass) survived to the immediate postoperative period. Injury Severity Score was similar (33 no bypass, 31 bypass, P =.48), as was admission base deficit (-9.2 m Eq/L no bypass vs. -7.0 mEq/L B, P =.13). Paraplegia occurred in four (12%) of the no bypass group as opposed to 0 of the bypass group (P =.05). No patient in the bypass group experienced complications related to heparinization, and two (7%) experienced bypass-related complications (cerebral edema, femoral vein laceration). Mean clamp time for the entire group was 27 minutes. Examination of the 10 patients with CI/R who survived the operating room showed markedly longer clamp times (59 minutes vs. 22 minutes, P <.0001) and a higher rate of paraplegia/paresis (30% vs. 2%, P =.01) as compared to those without CI/R. Logistic regression demonstrated a significant relationship between increasing clamp time and the CI/R classification (P =.007). All three (100%) of the CI/R patients repaired via clamp-and-sew technique developed paraplegia, while none of the seven CI/R patients repaired on bypass developed neurologic changes (P =.008). CONCLUSIONS: With the use of cardiopulmonary bypass in the repair of BAI, the incidence of paraplegia/paresis has fallen. While patients with typical injuries and uncomplicated repair can expect good results with either technique, cardiopulmonary bypass provides significant advantages in the repair of those with CI/R. With the use of bypass, no CI/R patient developed paraplegia, while all CI/R patients experienced paraplegia before bypass use. Although others have reported the importance of clamp time, in this series clamp time appeared largely to be a surrogate variable for complexity of injury.

Adult↗

PubMed2003

External fixation or arteriogram in bleeding pelvic fracture: initial therapy guided by markers of arterial hemorrhage.

BACKGROUND: Bleeding pelvic fractures (BPF) carry mortality as high as 60%, yet controversy remains over optimal initial management. Some base initial intervention on fracture pattern, with immediate external fixation (EX FIX) in amenable fractures aimed at controlling venous bleeding. Others feel ongoing hemodynamic instability indicates arterial bleeding, and prefer early angiography (ANGIO) before EX-FIX. Our aim was to evaluate markers of arterial bleeding in patients with BPF, thus identifying patients requiring early ANGIO regardless of fracture pattern. METHODS: Patients with pelvis fracture were identified from a Level I trauma center registry over a 7-year period and records reviewed. From this group, two subsets were analyzed: those with initial hypotension related to pelvic fracture, and those without hypotension who underwent pelvic ANGIO. Data included hemodynamics, response to resuscitation, presence of contrast blush on CT, fracture treatment and outcome. Adequate response to initial resuscitation (R) was defined as a sustained (>2 hours) improvement of systolic blood pressure to >90 mm Hg systolic after the administration of < or = 2 units packed red blood cells. Those with repeated episodes of hypotension despite resuscitation were classified as non-responders (NR) RESULTS: From 1/94-1/01, 1171 patients were admitted with pelvic ring fracture. Thirty-five (0.3%) had hypotension attributable to pelvis fracture. 28 fell into the NR group, and 26 of these underwent ANGIO. Nineteen (73%) showed arterial bleeding while 3 resuscitation response patients underwent ANGIO with none demonstrating bleeding (p = 0.03). Sensitivity and specificity of inadequate response to initial resuscitation for predicting the presence of arterial bleeding on ANGIO were 100% and 30% respectively while negative and positive predictive value were 100% and 73%. In patients with fractures amenable to external fixation (n = 16), 44% had arterial bleeding on ANGIO, and all were in the NR group. An additional 17 patients without hypotension also underwent ANGIO. Contrast blush on admission CT was seen in 4, 3 of which had arterial bleeding seen on ANGIO (75%). Sensitivity and specificity for contrast blush in predicting bleeding on ANGIO were 60% and 92% with positive and negative predictive value being 75% and 85%. CONCLUSIONS: In patients with hypotension and pelvic fracture, therapy selection based on initial response to resuscitation in BPF yields a 73% positive ANGIO rate in NR patients. Delay in ANGIO for EX FIX in patients with amenable fractures would have delayed embolization in the face of ongoing arterial bleeding in 44% of patients. In stable patients with pelvic fracture, contrast blush also indicates a high likelihood of arterial injury and ANGIO is indicated. Optimal therapy in the face of BPF requires early determination of the presence of arterial bleeding so that ANGIO can be rapidly obtained, and response to initial resuscitation as well as the presence of contrast blush aid in this decision.

Adult↗

PubMed2003

Improving the Glasgow Coma Scale score: motor score alone is a better predictor.

BACKGROUND: The Glasgow Coma Scale (GCS) has served as an assessment tool in head trauma and as a measure of physiologic derangement in outcome models (e.g., TRISS and Acute Physiology and Chronic Health Evaluation), but it has not been rigorously examined as a predictor of outcome. METHODS: Using a large trauma data set (National Trauma Data Bank, N = 204,181), we compared the predictive power (pseudo R2, receiver operating characteristic [ROC]) and calibration of the GCS to its components. RESULTS: The GCS is actually a collection of 120 different combinations of its 3 predictors grouped into 12 different scores by simple addition (motor [m] + verbal [v] + eye [e] = GCS score). Problematically, different combinations summing to a single GCS score may actually have very different mortalities. For example, the GCS score of 4 can represent any of three mve combinations: 2/1/1 (survival = 0.52), 1/2/1 (survival = 0.73), or 1/1/2 (survival = 0.81). In addition, the relationship between GCS score and survival is not linear, and furthermore, a logistic model based on GCS score is poorly calibrated even after fractional polynomial transformation. The m component of the GCS, by contrast, is not only linearly related to survival, but preserves almost all the predictive power of the GCS (ROC(GCS) = 0.89, ROC(m) = 0.87; pseudo R2(GCS) = 0.42, pseudo R2(m) = 0.40) and has a better calibrated logistic model. CONCLUSION: Because the motor component of the GCS contains virtually all the information of the GCS itself, can be measured in intubated patients, and is much better behaved statistically than the GCS, we believe that the motor component of the GCS should replace the GCS in outcome prediction models. Because the m component is nonlinear in the log odds of survival, however, it should be mathematically transformed before its inclusion in broader outcome prediction models.

Algorithms↗

PubMed2003

Optimal threshold for diagnosis of ventilator-associated pneumonia using bronchoalveolar lavage.

UNLABELLED: BACKGROUND Identification of ventilator-associated pneumonia (VAP) with invasive methods such as bronchoalveolar lavage (BAL) paired with treatment is associated with improved mortality. Inappropriate antibiotic use, however, is known to increase bacterial resistance, making future treatment problematic. Thus, the diagnostic threshold for VAP in BAL must yield adequate sensitivity while limiting exposure of patients to unnecessary antibiotics. Our institution uses a cutoff of > or = 10(5) colony-forming units (CFUs)/mL, but the optimal cutoff remains an area of debate. In this project, the effects of lower diagnostic cutoffs on VAP diagnosis and unnecessary antibiotic use are examined. METHODS: Records of all patients admitted to the trauma intensive care unit over a 2-year period requiring > 48 hours of mechanical ventilation were reviewed. Number of BALs, quantity of organism on each BAL, and presence of VAP (> or = 10(5) CFUs/mL) were noted. Indication for BAL was pulmonary infiltrate, sepsis syndrome, and C-reactive protein > 17 microg/dL at > or = 48 hours after admission. RESULTS: From January 1, 2000, to December 31, 2001, 563 patients were admitted to the trauma intensive care unit. Two hundred fifty-seven required > 48 hours of mechanical ventilation, and 257 BALs were performed in 168 (65%) of these patients. One hundred thirty-nine episodes of VAP occurred in 109 (42%) patients. Subdiagnostic quantities of bacteria (> or = 10(2) but < 10(5) CFUs/mL) were seen in 98 BALs. Of these, only 16 (16%) episodes of VAP with the same organism were seen later during hospitalization. At a threshold of > or = 10(4) CFUs/mL, 4 of 28 (14%) patients went on to develop pneumonia. A similar pattern was seen at diagnostic thresholds of > or = 10(3) CFUs/mL (10 of 72 [14%]) and > or = 10(2) CFUs/mL (16 of 98 [16%]). CONCLUSION: A threshold of > or = 10(5) CFUs/mL for VAP diagnosis carries a low false-negative rate. Over 80% of additional patients who would have been treated had a threshold of > or = 10(4) CFUs/mL been used recovered without treatment and thus would have undergone unnecessary antibiotic exposure. A similar pattern is seen at all lower thresholds. Lower diagnostic thresholds would lead to marginal increase in sensitivity, and many would receive unnecessary VAP treatment with potential for increasing bacterial resistance.

Adult↗

PubMed2003

A fresh set of survival risk ratios derived from incidents in the National Trauma Data Bank from which the ICISS may be calculated.

BACKGROUND: Survival risk ratios (SRRs) are database-specific point estimates of survival associated with each injury International Classification of Diseases, Ninth Revision (ICD-9) code. They are derived for each injury code by dividing the number of patients who survive the code by the total number of patients that display the code. SRRs are used to measure injury severity and distribution and are most prominently featured in the ICD-9 Injury Severity Score (ICISS), which is the product of a patient's SRRs. Because SRRs are important for trauma scoring, it is important that they be derived from a representative trauma population. The purpose of this study was to compare a new set of SRRs derived from the National Trauma Data Bank (NTDB) with SRRs derived years ago from the North Carolina Hospital Discharge Database (NCHDD). METHODS: Tests for differences of proportions were applied to determine which ICD-9 codes have significantly different SRRs in an attempt to characterize the database differences. Two different ICISSs were calculated for 170,853 eligible patients using the two different sets of SRRs, NCHDD and NTDB. The NTDB SRRs were calculated and applied using a 10-fold cross-validation to avoid bias in estimation. Estimates of discrimination for both ICISSs were calculated using the area under the receiver-operating characteristic curve. R2 and Akaike information criterion statistics were compared. RESULTS: A modest statistical case is made for using the NTDB SRRs rather than the NCHDD SRRs. CONCLUSION: Researchers should begin using the NTDB SRRs for their outcome modeling and for ICISS calculation.

Databases as Topic↗

PubMed2003

Independently derived survival risk ratios yield better estimates of survival than traditional survival risk ratios when using the ICISS.

BACKGROUND: The International Classification of Diseases, Ninth Revision Injury Severity Score (ICISS) is criticized because it relies on survival risk ratios (SRRs) that are contaminated by incidents with multiple injuries. An SRR for an International Classification of Diseases, Ninth Revision code is the number of patients who survive the injury divided by the number who display it. The ICISS is the product of SRRs that correspond to a patient's injuries. Traditional SRRs are derived from databases that include patients with multiple injuries and are biased toward mortality, making them nonindependent. Independent SRRs are derived from incidents where patients sustained only an isolated injury. The objective of this study is to compare the mortality prediction abilities of independent and traditional SRRs via the ICISS. METHODS: A 10-fold cross-validation design was used to estimate independent and traditional SRRs and their resulting ICISSs from 192,347 National Trauma Data Bank patients. Logistic regression modeled the scores as a function of mortality. The area under the receiver operating characteristic curve measured discrimination. Model fit was measured with the Akaike information criterion, a deviance statistic (lower is better). R2 values were compared to determine which score explained the most variance. RESULTS: The independent ICISS statistically outperforms the traditional ICISS. CONCLUSION: Traditional SRRs used by the ICISS produce less accurate estimates of mortality than independent SRRs. The ICISS can be calculated in 97.9% of incidents using independent SRRs.

Databases as Topic↗

PubMed2002

The vacuum assisted closure device: a method of securing skin grafts and improving graft survival.

HYPOTHESIS: Use of the vacuum assisted closure device (VAC) for securing split-thickness skin grafts (STSGs) is associated with improved wound outcomes compared with bolster dressings. DESIGN: Consecutive case series. PATIENTS AND SETTING: Consecutive patients at a level I trauma center requiring STSG due to traumatic or thermal tissue loss during an 18-month period. MAIN OUTCOME MEASURE: Repeated skin grafting due to failure of the initial graft. Secondary outcome measures included dressing-associated complications, percentage of graft take, and length of hospital stay. RESULTS: Sixty-one patients underwent STSG placement. Indications for STSG were burn injury (n = 32), soft tissue loss (n = 27), and fasciotomy-site coverage (n = 2). Patients were treated with the VAC (n = 34) or the bolster dressing (n = 27). The VAC group required significantly fewer repeated STSGs (1 [3%] vs 5 [19%]; P =.04). Two additional graft failures occurred in the no-VAC group, but repeated STSGs were refused by these patients. No difference was seen between the groups in age, percentage of graft take, or hospital length of stay. The no-VAC group had significantly larger grafts (mean +/- SD, 984 +/- 996 vs 386 +/- 573 cm(2); P =.006). The patients requiring repeated STSGs (n = 6) did not have significantly larger grafts than those not requiring repeated STSGs (mean +/- SD, 617 +/- 717 vs 658 +/- 857 cm(2); P =.62). No dressing-associated complications occurred in the VAC group. CONCLUSIONS: The VAC provides a safe and effective method for securing STSGs and is associated with improved graft survival as measured by a reduction in number of repeated STSGs.

Adult↗

PubMed2002

A comparison of the abilities of nine scoring algorithms in predicting mortality.

OBJECTIVE: The purpose of this study was to compare the abilities of nine Abbreviated Injury Scale (AIS)- and (ICD-9)-based scoring algorithms in predicting mortality. METHODS: The scores collected on 76,871 incidents consist of four AIS-based algorithms (Injury Severity Score [ISS], New Injury Severity Score, Anatomic Profile Score [APS], and maximum AIS [maxAIS]), their four ICD to AIS mapped counterparts, and the ICD-9-based ISS (ICISS). A 10-fold cross-validation was performed and area under the receiver operating characteristic curve was used to determine algorithm discrimination. Hosmer-Lemeshow statistics were computed to gauge goodness-of-fit, and model refinement measured variance of predicted probabilities. RESULTS: Overall, the ICISS has the best discrimination and model refinement, whereas the APS has the best Hosmer-Lemeshow performance. ICD-9 to AIS mapped scores have worse discrimination than their AIS-based counterparts, but still show moderate performance. CONCLUSION: Differences in performance were relatively small. Complex scores such as the ICISS and the APS provide improvement in discrimination relative to the maxAIS and the ISS. Trauma registries should move to include the ICISS and the APS. The ISS and maxAIS perform moderately well and have bedside benefits.

Abbreviated Injury Scale↗

PubMed2002

Improving ventricular-arterial coupling during resuscitation from shock: effects on cardiovascular function and systemic perfusion.

BACKGROUND: Efficacy of circulation depends on interactions between the heart and the vascular system. Ventricular-arterial coupling (VAC) has been described as an important determinant of cardiovascular function during resuscitation from shock. However, no prospective studies examining VAC and systemic perfusion have been performed. VAC is measured by the ratio of afterload (aortic input impedance [E ]) to contractility (end-systolic elastance [E ]). Lowering E /E is associated with better VAC and improved myocardial work efficiency. Our hypothesis was that optimizing VAC during resuscitation results in improved myocardial work efficiency while simultaneously improving systemic perfusion. METHODS: This was a prospective study in a consecutive series of critically injured patients. Hemodynamic variables, including E, E, and myocardial work efficiency were evaluated by constructing ventricular pressure-volume loops at the bedside during resuscitation. After pulmonary artery catheterization and adequate fluid resuscitation, left ventricular power output and E /E were optimized with inotropic agents and/or afterload reduction. Efficiency was calculated as stroke work/total left ventricular energy expenditure. Tissue perfusion was estimated by calculating base deficit clearance per hour. RESULTS: Twenty-three patients were studied over a 9-month period. Fifteen patients required inotropic support or afterload reduction. Improvements were seen in E /E (from 1.0 +/- 0.4 to 0.6 +/- 0.2 mm Hg/mL/m, p = 0.0004), and left ventricular power output (from 280 +/- 77 to 350 +/- 81 L/min/m. mm Hg, p = 0.003) with resuscitation. A concomitant improvement in myocardial efficiency (from 70% +/- 8.0% to 77% +/- 5.0%, p = 0.0001) and base deficit clearance (from 0.1 +/- 0.4 to -0.2 +/- 0.1 mEq/L/h, p = 0.006) was seen. CONCLUSION: Improved ventricular-arterial coupling during resuscitation is associated with improved myocardial efficiency and systemic tissue perfusion. Perfusion can be improved at lower energy cost to the heart by focusing on thermodynamic principles during resuscitation.

Acid-Base Equilibrium↗

PubMed2002

Late fascial closure in lieu of ventral hernia: the next step in open abdomen management.

BACKGROUND: The use of open abdomen techniques in damage control laparotomy and abdominal compartment syndrome has led to development of several methods of temporary abdominal closure. All of these methods require creation of a planned hernia with later reconstruction in patients unable to undergo fascial closure in the early postoperative period. We review a method of late primary fascial closure, thus eliminating the need for delayed reconstruction in some patients. METHODS: The records of all patients managed with open abdomens over a 5-year period at a Level I trauma center were reviewed for injury characteristics, operative treatment, final abdominal closure type and timing, and outcome. Patients requiring open abdomen who were unable to undergo fascial closure in the early postoperative period were managed with a vacuum-assisted fascial closure (VAFC) technique. This allows for constant tension on the wound edges and facilitates late fascial closure. Patients managed with planned hernia (HERNIA group) were compared with those undergoing fascial closure > or = 9 days after initial laparotomy (LATE group) for injury severity, fistula rate, and mortality. All patients in the LATE group underwent VAFC. RESULTS: From September 1996 to October 2001, 148 patients required management with an open abdomen. Fifty-nine underwent fascial closure, 37 of these before postoperative day 9 and 22 on or after day 9. Mean time to closure in the LATE group was 21 days (range, 9-49 days). Injury Severity Scores were similar in the HERNIA and LATE groups (26 vs. 30, p = 0.28), as were admission base deficit (-8.8 vs. -9.5, p = 0.71), number of fistulas (1 vs. 0, p = 0.99), and mortality (17% vs. 14%, p = 0.99). CONCLUSION: VAFC enables late fascial closure in open abdomen patients up to a month after initial laparotomy. Complication rates do not differ from patients with planned hernia, and the need for future abdominal wall reconstruction is avoided.

Abdominal Injuries↗

PubMed2002

Elevated admission white blood cell count in pregnant trauma patients: an indicator of ongoing placental abruption.

Placental abruption (PA) is a common cause of fetal demise in pregnant trauma patients. Diagnosis of PA may be difficult, and multiple diagnostic clues are currently used including uterine/abdominal pain and tenderness, bleeding, maternal hemodynamic instability, and evidence of PA by ultrasonography or other fetal monitoring. Although diagnosis may be problematic fetal and maternal survival are dependent on early diagnosis and intervention. The purpose of this study is to determine predictive factors present at admission associated with PA in trauma victims. Records of all pregnant trauma patients admitted to Wake Forest University Baptist Medical Center over a 5-year period were reviewed for injury characteristics and outcome. Inclusion criteria included a confirmed pregnancy and fetal disposition. Specific admission parameters evaluated included temperature, heart rate, systolic blood pressure, partial pressure of CO2 in arterial blood, total white blood cell count (WBC) and differential, hematocrit, base deficit, and lactic acid. PA is defined as a spontaneous abortion in the first trimester or abruptio placenta in the second or third trimester. Between April 1, 1996 and October 30, 2000, 30 patients met study criteria. Six of 30 patients were found to have PA (20%). Of the studied parameters WBC was significantly elevated in PA patients (27 +/- 4.6 vs 17 +/- 7.8 WBC x 10(3)/mm3; P = 0.005) as was band count (10 +/- 6.6% vs 4 +/- 6.1%; P = 0.03). Hematocrit was lower in the PA group (27 +/- 4.3% vs 32 +/- 5.4%; P = 0.04). Within this group of variables which differed on univariate analysis, WBC was the best discriminator between patients with and without PA (sensitivity 100%, specificity 79%, negative predictive value 100%, and positive predictive value 54%). In pregnant trauma patients WBC >20,000/mm3 on admission should raise suspicion of the possibility of PA, and close monitoring is warranted. Conversely WBC <20,000/mm3 rules out PA in the pregnant trauma patient (negative predictive value of 100%).

Abruptio Placentae↗

PubMedDate not supplied

The effect of burn nursing units on burn wound infections.

Temporary closure of our burn unit allowed evaluation of the effect of a closed unit on infection rates. During renovations, burned patients were treated either in private ward rooms or in the intensive care unit by burn unit nursing staff using the same wound care practices as used in the burn unit. Data regarding burn severity and outcome were collected and compared for all patients treated before (Group A), during (Group B), and after (Group C) renovations. Burned surface area, average age, and hospital stay were statistically similar for each group. Incidence of infection differed significantly (P < 0.005) with 47% of Group B developing infection compared with 11 and 23% for Groups A and C respectively. Mortality rates were not significantly different. Despite consistent wound care the incidence of infection increased nearly two-fold to four-fold when patients were treated out of the unit. We recommend a temporary isolation unit during renovations if possible.

Adolescent↗