Safety in High School Supervised Agricultural Experiences: Teachers' Training and Students' Injury Awareness.

This research study sought to gather evidence of school-based agriculture teachers' hazard perceptions, safety practices, training experiences, and awareness of student injuries related to supervised agricultural experience (SAE) programs. Teachers agreed that students should follow safety guidelines developed by the National Children's Center for Rural and Agricultural Safety and Health during SAE work. Approximately 66% (f = 153) of teachers reported having general training in first aid, CPR, and AED. Twenty participants (8.6%) indicated having no safety certifications or training. Abrasions, lacerations, bites/stings, and burns accounted for a majority of the student SAE-related injuries that were reported. There were 82 participants (35.5%) who stated that no injuries had been reported or they were not aware of any injuries that occurred. The majority of teachers (66%) had received some form offirst aid or first response training, but fewer teachers had received safety training for ATVs (f = 25, 10.8%), tractors (f = 48, 20.7%), and livestock (f = 39, 16.8%). Results indicated a disparity between required safe work habits and the types of hazardous tasks students should be allowed to complete alone while participating in SAE activities. It appears most responding teachers in this study agreed to allow students to operate equipment and machinery alone. Recommendations for teachers include attending professional development training specific to SAE safety and keeping records of any risk assessments conducted during SAE supervision. Further development of best practices for SAE supervision and safety are needed to assist agricultural education professionals in protecting and shaping our future leaders in agriculture.

Experimental knee joint pain during strength training and muscle strength gain in healthy subjects: a randomized controlled trial.

OBJECTIVE: Knee joint pain and reduced quadriceps strength are cardinal symptoms in many knee pathologies. In people with painful knee pathologies, quadriceps exercise reduces pain, improves physical function, and increases muscle strength. A general assumption is that pain compromises muscle function and thus may prevent effective rehabilitation. This study evaluated the effects of experimental knee joint pain during quadriceps strength training on muscle strength gain in healthy individuals. METHODS: Twenty-seven healthy untrained volunteers participated in a randomized controlled trial of quadriceps strengthening (3 times per week for 8 weeks). Participants were randomized to perform resistance training either during pain induced by injections of painful hypertonic saline (pain group, n = 13) or during a nonpainful control condition with injection of isotonic saline (control group, n = 14) into the infrapatellar fat pad. The primary outcome measure was change in maximal isokinetic muscle strength in knee extension/flexion (60, 120, and 180 degrees/second). RESULTS: The group who exercised with pain had a significantly larger improvement in isokinetic muscle strength at all angular velocities of knee extension compared to the control group. In knee flexion there were improvements in isokinetic muscle strength in both groups with no between-group differences. CONCLUSION: Experimental knee joint pain improved the training-induced gain in muscle strength following 8 weeks of quadriceps training. It remains to be studied whether knee joint pain has a positive effect on strength gain in patients with knee pathology.

Physician interpretation and quantitative measures of electrocardiographic ventricular fibrillation waveform.

OBJECTIVES: The characteristics of the ventricular fibrillation (VF) waveform may influence treatment decisions and the likelihood of therapeutic success. However, assessment of VF as being fine or coarse and the distinction between fine VF and asystole are largely subjective. The authors sought to determine the level of agreement among physicians for interpretation of varying VF waveforms, and to compare these subjective interpretations with quantitative measures. METHODS: Six-second segments of waveform from LIFEPAK 300 units were collected. Fifty segments, including 45 VF and five ventricular tachycardia (VT) distracters, were graphed to simulate rhythm strips. These waveforms were quantitatively described using scaling exponent, root-mean-squared amplitude, and centroid frequency. Thirty-two emergency medicine residents were asked to interpret the arrhythmias as VT, "coarse" VF, "fine" VF, or asystole. Their responses were compared with the qantitative measures. Interphysician agreement was assessed with the kappa statistic. RESULTS: One thousand four hundred forty interpretations were analyzed. There was fair agreement between physicians about the classification of arrhythmias (kappa = 0.39). Mean values associated with coarse VF, fine VF, and asystole differed in all three quantitative measure categories. The decision whether to defibrillate was highly correlated with the distinction between VF and asystole (Pearson chi-square = 1,170.40, df = 1, p[two-sided] < 0.001). CONCLUSIONS: With only fair agreement on the threshold of fine VF and asystole, defibrillation decisions are largely subjective and caregiver-specific. These data suggest that quantitative measures of the VF waveform could augment the current standard of subjective classification of VF by emergency care providers.

The regional capillary distribution of retrograde blood cardioplegia in explanted human hearts.

Warm retrograde blood cardioplegia is frequently used for myocardial protection, despite experimental studies questioning the adequacy of capillary flow to the right ventricle and septum. The capillary distribution of retrograde blood cardioplegia in the human heart is unknown. Hearts from eight transplant recipients with the diagnosis of idiopathic or dilated cardiomyopathy were arrested in situ with cold blood cardioplegia and excised with the coronary sinus intact. Within 20 minutes of explanation, colored microspheres mixed in 37 degrees C blood cardioplegia were administered through the coronary sinus at a pressure of 30 to 40 mm Hg for 2 minutes. Twelve transmural myocardial samples were taken horizontally at the level of midventricle and apex to determine regional capillary flow rates. When retrograde warm blood cardioplegia was administered at a rate of 0.42 +/- 0.06 ml/gm/min, the left ventricle, the septum, the posterior wall of the right ventricle, and the apex consistently received capillary flow rates in excess of their metabolic requirements. The capillary perfusion of anterior and lateral walls of the right ventricle was marginally adequate to sustain aerobic metabolism. In explanted human hearts, retrograde blood cardioplegia provides adequate capillary flow to the left ventricle, the septum, the posterior wall of the right ventricle, and the apex; however, capillary flow to the anterior and lateral walls of the right ventricle is marginal. This study delineates the tenuous balance between supply and demand for right ventricular protection with warm continuous retrograde blood cardioplegia.

Loss of endothelium-dependent vasodilatation and nitric oxide release after myocardial protection with University of Wisconsin solution.

University of Wisconsin solution has proved to be a superior form of cardioplegia for cardiac transplantation, demonstrating better functional recovery than that provided by extracellular crystalloid solutions. Furthermore, experimental data have suggested a role for University of Wisconsin solution in protection of the neonatal heart during operations for congenital heart defects. However, significant concerns have been raised regarding potential endothelial injury from the high potassium concentration contained in University of Wisconsin solution that could affect its safety and thus its clinical application. Fourteen neonatal (aged 1 to 3 days) piglet hearts were harvested and supported on an isolated, blood-perfused circuit. Endothelium-dependent vasodilatation was measured by bradykinin (10(-6) mol/L) infusion and nitric oxide release was determined. Endothelium-independent vasodilatation was then induced by sodium nitroprusside (10(-6) mol/L) infusion. A 2-hour period of cold cardioplegic arrest was instituted with multidose University of Wisconsin solution (group 1, n = 7) or blood cardioplegia (group 2, n = 7). After reperfusion and stabilization, another stimulation with bradykinin and nitroprusside was carried out and nitric oxide was again measured. After 2 hours of arrest with University of Wisconsin solution, there was a near-complete loss of vasodilatation in response to bradykinin infusion; coronary blood flow reached 245% of baseline before arrest versus only 117% of baseline after arrest (p = 0.0011). This correlated with an inability of the endothelium to release nitric oxide (96 +/- 30 nmol/min before arrest versus -32 +/- 9 nmol/min after arrest, p = 0.0039. In group 2, the vasodilatory response to bradykinin was preserved after arrest and reperfusion; 265% of baseline before arrest versus 222% of baseline after arrest. These results demonstrate a loss of endothelium-dependent vasodilatation after multidose University of Wisconsin cardioplegia caused by the inability of the endothelium to release nitric oxide. In contrast, blood cardioplegia does not result in impaired endothelial function.

Experimental cardiac allograft vasculopathy in mice.

Cardiac allograft vasculopathy is the most common cause of death in heart transplant recipients after the first postoperative year. The pathogenesis of cardiac allograft vasculopathy is not clearly defined. To better study this disease, a genetically well-defined and reproducible animal model such as the mouse is needed. We performed heterotopic, intraabdominal heart transplantation between two inbred strains of mice. The B10.A strain served as donors, and the B10.BR strain served as recipients. No immunosuppressive therapy was administered. The allografts in groups I (n = 6) and II (n = 6) were harvested at 30 and 50 days after operation, respectively. All allografts had palpable contractions at the time of harvest. The cardiac allografts from both groups showed mild to moderate acute cellular rejection. In groups I and II, 55% +/- 26% and 60% +/- 18% of arteries showed intimal thickening, respectively. Pathologically, the vascular lesions were characterized with varying degrees of intimal thickening, subendothelial mononuclear cell infiltration and fibrosis, frequent disruption of the internal elastic lamina, and perivascular inflammation. These findings are characteristic of cardiac allograft vasculopathy seen clinically. Isografts (n = 6) showed no vascular lesions. The heterotopic transplantation of B10.A-strain hearts into B10.BR recipients provides a useful murine model for future studies in the pathogenesis and treatment of cardiac allograft vasculopathy.

Gross and microvascular distribution of retrograde cardioplegia in explanted human hearts.

In this report, explanted hearts from transplant recipients with the diagnosis of idiopathic cardiomyopathy underwent a blood cardioplegia arrest and extended subatrial resection to preserve their coronary sinus venous system. The coronary sinus and left and right coronary arteries were then cannulated and warm blood cardioplegia retrograde infused at a pressure of 30 to 40 mm Hg. Effluent from the coronary arteries and thebesian veins was then collected. Hearts were subsequently fixed with retrograde glutaraldehyde perfusion and perfused retrograde with NTB-2 (an inert intracapillary marker). Histologic sections were examined from 12 separate sites. There was no significant difference in the percentage of capillaries perfused by retrograde-delivered cardioplegia between corresponding regions of the left and right ventricles. However, effluent analysis indicated that 67.2% +/- 6.4% of retrograde-delivered blood cardioplegia was shunted through thebesian veins, thereby bypassing the microvasculature, whereas 29.3% +/- 6.3% and 3.5% +/- 3.1% traversed the myocardium supplied by the left and right coronary arteries, respectively. The results indicate that all regions of both ventricles are perfused by retrograde blood cardioplegia. However, they also suggest that nutrient flow to the microvasculature of the right ventricle is minimal during retrograde cardioplegia.

Aortic valve replacement using a continuous suture technique.

The continuous suture technique has been proposed as an alternate method for aortic valve replacement (AVR). Advantages include a decreased ischemic and bypass time. Despite reports of a low incidence of perivalvular leak, wide use of the continuous suture technique has not been adopted. This report reviews our experience with the continuous suture technique. From January 1984 through November 1991, 181 consecutive patients underwent AVR using the continuous suture technique. The mean age was 61 years (range 6 to 88 years). Diagnoses included pure aortic stenosis (AS) in 41%, aortic insufficiency (AI) in 31%, and a combination of AS and AI in 28%. Fifty-six patients underwent isolated AVR and 125 underwent AVR combined with other procedures. The overall early mortality was 5.5%. Early mortality for isolated AVR was 0% (0/56) and was 8.0% (10/125) for those undergoing concomitant procedures. Late mortality was 4.7% in a mean follow-up of 30 months (range 1 to 86 months). The incidence of perivalvular leak was 2.3% (4/171 operative survivors). Perivalvular leak was mild in two, and moderate in two; none required reoperation. Perivalvular leak developed only in patients whose suture line was not reinforced with glutaraldehyde treated pericardium. The continuous suture technique is a quick and effective method for AVR and results in a low incidence of perivalvular leak.

Cardiac transplantation at UCLA.

In the last decade, the number of patients undergoing heart transplantation has steadily increased as a result of expanding indications for cardiac transplantation. The limitation on the number of transplants performed has been the scarcity of donor organs. At UCLA, 320 heart transplant procedures were performed in adults through the end of 1992; 173 patients (54%) underwent transplantation for ischemic cardiomyopathy; 104 (33%) for dilated cardiomyopathy, and 13 (4%) for severe rejection or cardiac allograft vasculopathy. The mean number of rejection episodes and infections per patient per year in the first posttransplant year was 1.28 and 0.58, respectively. Early mortality (30 days) was 5.7%, while 1-, 3-, and 5-year survival rates were 84.3%, 74.3%, and 67.5%, respectively. Survival of patients transplanted for ischemic cardiomyopathy and idiopathic cardiomyopathy was nearly equal. Survival was also comparable in patients aged 60 years and over (n = 71) and those under age 60. We observed improved patient outcome including shorter posttransplant hospital stay, time to extubation, and lower incidences of infections, rejection episodes, and renal failure in patients transplanted in 1991 and 1992. This observation was interesting in view of the increased proportion of critically ill patients in this group (46% UNOS Status 1) compared with patients transplanted in the previous years (30% UNOS Status 1).(ABSTRACT TRUNCATED AT 250 WORDS)