Surgical correction of burn scar contractures of the foot in children

The results of reconstructive procedures for the treatment of burn scar contractures of the feet in 55 children undergoing 90 operations were reviewed. The patients were treated in all but one case by release of the contracture band with placement of a skin graft in the resulting defect. There was an overall recurrence rate of 15 per cent that was not affected by the use of split-thickness versus full-thickness grafts. The time delay from the thermal injury to the reconstructive procedure was also found not to affect the outcome. Postoperative immobilization by the use of either a dynamic or an adynamic splint was found to be important both for preventing graft loss and for decreasing the rate of contracture recurrence.     

Selective Embolization of Glomus Jugulare Tumors

Four patients with grade C or D₁ glomus jugulare tumors who underwent preoperative highly selective embolization followed by infratemporal fossa removal of their tumors were compared to three patients undergoing surgery alone with respect to intraoperative blood loss, operative time, cranial nerve palsy, length of hospitalization, and perioperative complications. Embolized patients demonstrated a marked reduction in blood loss (650 vs 1375 cc) compared with the nonembolized group. Operative time was shortened (by 51 minutes). Facial nerve function did not appear related to embolization but was directly related to intraoperative nerve manipulation. Hospital stay, perioperative complications, and lower cranial nerve palsies were not related to embolization.     

Dr. Tom Chalmers, 1917-1995: the trials of a randomizer

Dr. Thomas Chalmers, an American physician who played a pivotal role in the scientific development of the randomized control trial and meta-analysis, died late last year. Shortly before Chalmers' death, Dr. Malcolm Maclure of the British Columbia Ministry of Health conducted a wideranging interview with him about his life and the past and future of clinical trials and evidence-based medicine. The first part is published below; the second part will appear in the Oct. 1 issue of CMAJ.     

Assessment of the Severity of Asthma in a Family Practice

The objective of this study was to evaluate clinical history and self-perception of severity as predictors of asthma severity. A short-term longitudinal study was conducted in a family practice in Melbourne, Australia, utilizing peak flow monitoring, medication diary, and self-administered asthma severity questionnaire. Seventy-two asthmatic subjects with a positive bronchodilator or exercise test, aged between 6 and 79 years, were studied. Symptom and treatment items were correlated with peak flow variability and minimal peak expiratory flow rate (PEFR). An asthma severity scale was generated using the partial credit version of Item Response Theory and the participants' severity scores were validated against lung function tests and medication usage. Quantitative modeling procedures were used to investigate the interrelationships of factors associated with peak flow variability. Severity scores demonstrated significant relationships with peak flow variability (partial r = 0.34) and treatment items. Self-perceived severity of asthma in the preceding 2 weeks showed significant association with peak flow variability (partial rho = 0.46) and minimal PEFR (rho = -0.41). The severity module of the Monash Respiratory Questionnaire is a valid and reliable instrument. The most important symptoms appear to be the frequency of use of bronchodilator and frequency of nocturnal attacks. A carefully structured clinical history in conjunction with the peak flow criteria of variability and minimal peak flow rate would be appropriate in the evaluation of asthma severity. Patients' self-perception of the severity of their asthma needs further evaluation.     

Conservatively Treated Breast Cancer: Outcome by Histologic Subtype

Abstract: Between 1970 and 1990, 1,008 patients with early-stage breast cancer were treated by conservative surgery without axillary dissection followed by radiation therapy to the intact breast in the Department of Therapeutic Radiology at Yale-New Haven Hospital. The patient population, broken down by histologic subtype, was as follows: 761 patients presented with infiltrating ductal carcinoma, 70 patients with pure intraductal, 38 intraductal with focal invasion, 54 infiltrating lobular, 21 tubular, 17 medullary, 16 mucinous, and 29 with other various histologic subtypes. Patients were followed on a regular basis by the referring physicians and radiation oncologists. Diagnostic studies for distant metastases were performed as clinically indicated. Annual mammography was a routine component of the follow-up program. As of 3/96, with a median follow-up of 10.5 years, 83 patients developed an ipsilateral breast tumor recurrence, and 109 patients developed distant metastases resulting in an overall 10-year breast recurrence-free rate of 84%, and a 10-year distant metastasis-free rate of 78%. There were significant differences in clinical stage, pathological nodal involvement, and administration of systemic therapy between various histologic subtypes. As expected, those patients with histologies of low metastatic potential (such as intraductal, tubular, and mucinous) had significantly superior distant recurrence-free survival rates. With respect to breast relapse rates, there were no statistically significant differences in the 5- and 10-year breast recurrence-free rates between any of the histologic subtypes. Patients with intraductal carcinoma with or without focal invasion had similar breast relapse rates as those with other histologic subtypes. Patients with lobular carcinoma in situ as a histologic component also had a similar overall breast relapse-free recurrence rate. In conclusion, long-term follow-up of conservatively treated breast cancer patients demonstrates no significant differences in ipsilateral breast tumor recurrence rates between various histologic subtypes. There are no histologies which had a statistically significantly higher breast-relapse rate than infiltrating ductal carcinomas and therefore no primary histologic subtype represents a relative contraindication to breast conservation therapy.     

A multicenter clinical trial of gadolite oral suspension as a contrast agent for MRI

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49–1.18 for reader 1; .46–1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.     

Leukocyte Depletion of Blood Cardioplegia Attenuates Reperfusion Injury

Background. Leukocytes are associated with myocardial injury during reperfusion after ischemia. Short periods of leukocyte depletion during reperfusion result in persistent attenuation of postischemic myocardial dysfunction.

Methods. Leukocyte depletion was examined in a canine model of regional myocardial ischemia and reperfusion. The extracorporeal circuit and cardioplegia circuits underwent leukocyte depletion by mechanical filtration. Animals were instrumented for baseline global function before 90-minute occlusion of the left anterior descending coronary artery. Global function during ischemia and at 5, 30, 60, and 90 minutes after a 60-minute cardioplegic arrest using continuous blood cardioplegia was assessed in leukocyte-depleted (n = 9) and control (n = 10) groups.

Results. No significant difference between groups was seen for systemic leukocyte counts, global function, or water content. Endothelial function was significantly protected as assessed by response to both calcium ionophore (endothelial-dependent, receptor-independent relaxation: leukocyte-depleted, 72% ± 19% of endothelin-induced constriction versus control, 46% ± 14%; p < 0.05) and acetylcholine (endothelial-dependent, receptor-dependent relaxation: leukocyte-depleted, 83% ± 11% versus control, 44% ± 15%; p < 0.05).

Conclusions. Leukocyte-mediated endothelial reperfusion injury can be attenuated by leukocyte depletion during reperfusion.     

Quantifying how tests reduce diagnostic uncertainty.

BACKGROUND: Diagnostic tests are commonly evaluated from sensitivity and specificity, which are robust and independent of prevalence, but clinically not intuitive. Many clinicians prefer to use positive and negative predictive values (PPV and NPV), but they are frequently applied as if they are independent of prevalence, whereas this may make an important difference. METHODS AND RESULTS: We present graphs that allow easy reference to appropriate values and demonstrate that PPV and NPV are not independent of prevalence. PPV and NPV figures reflect the prior probability of the case having a positive diagnosis, estimated clinically from the history, examination and other results, as well as the impact of the test result. To avoid the common error of allowing for prior probability twice, and to interpret the impact of the test result alone, we present graphs of the proportionate reduction in uncertainty score (PRU), calculated from sensitivity, specificity and prevalence. These plots show the extent to which either a positive or negative test result affects the remaining degree of uncertainty about a diagnosis in either direction, according to likely clinical prevalence. CONCLUSIONS: PRU plots demonstrate the discriminatory value of tests more clearly than sensitivity and specificity from which they are derived, and should be published alongside them.     

Ischemia-reperfusion-induced muscle damage: Protective effect of corticosteroids and antioxidants in rabbits

We examined the potential protective effect of pretreatment with corticosteroids or antioxidants (ascorbic acid or allopurinol) in rabbits with reper-fusion-induced damage to skeletal muscle after ischemia.

4 hours of limb ischemia induced by a pneumatic tourniquet, followed by reperfusion for 1 hour, caused a considerable amount of ultrastructural damage to the anterior tibialis muscles accompanied by a rise in circulating creatine kinase activity. Pretreatment of animals with depomedrone by a single 8 mg bolus injection led to a preservation of the anterior tibialis structure on both light and electron microscopy. High-dose continuous intravenous infusion with ascorbic acid (80 mg/hr) throughout the period of ischemia and reperfusion also preserved skeletal muscle structure, although allopurinol in various doses had no protective effect.

These data are fully compatible with a mechanism of ischemia/reperfusion-induced injury to skeletal muscle, involving generation of oxygen radicals and neutrophil sequestration and activation. They also indicate that damage to human skeletal muscle caused by prolonged use of a tourniquet is likely to be reduced by simple pharmacological interventions.