Time-dependent changes in norepinephrine-induced left ventricular dysfunction and histopathologic condition.

BACKGROUND: Intense activation of the sympathetic nervous system or administration of high concentrations of catecholamines diminishes myocardial contractility and produces infarct-like lesions throughout the heart. This study was conducted to determine whether norepinephrine-induced left ventricular (LV) dysfunction reverses with time and whether the histopathologic condition and the cardiac dysfunction produced by high doses of norepinephrine are causally related. METHODS: Norepinephrine, 10 microg bolus followed by 2.5 microg/kg/min for 90 minutes, was administered to conscious New Zealand white rabbits. Control rabbits (n=8) received saline solution. LV function was evaluated either immediately (n=7), on day 4 (n=8), or on day 10 (n=7) after norepinephrine treatment. Transverse sections from the left ventricle were then prepared for light microscopic study. RESULTS: Animals studied immediately after norepinephrine treatment demonstrated severe LV dysfunction and a decrease in global LV compliance. In contrast, LV function and compliance were normal in rabbits studied on day 4, but tissue sections from the left ventricle showed diffuse areas of inflammation. By day 10 the inflammatory process had progressed, and substantial collagen deposition had occurred. LV systolic function was normal, but a decrease in LV compliance was evident at this time. CONCLUSIONS: The normal LV systolic function on days 4 and 10 in spite of multiple foci of inflammation suggests (1) that norepinephrine-induced LV systolic dysfunction is reversible and (2) that the histologic derangements and the LV dysfunction are not causally related.

Myocardial work load is a major determinant of norepinephrine-induced left ventricular dysfunction.

This study was conducted to determine whether increased myocardial energy demand plays a role in norepinephrine (NE)-induced left ventricular (LV) dysfunction. A range of arterial pressure-heart rate (P-R) products (myocardial energy demand) was produced in both conscious and pentobarbital sodium-anesthetized rabbits with the same dose of NE (10 micrograms priming bolus plus 2.5 micrograms.kg-1 x min-1 for 2.5 h). After NE treatment, LV function was evaluated in vitro and found to be markedly diminished in the rabbits that had an elevated P-R product. In contrast, LV function was not significantly affected when the P-R product was maintained near control levels during NE treatment. In separate experiments, rabbit hearts were isolated and exposed to NE (10,000 or 50,000 pg/ml) for 2.5 h under low P-R product conditions. These hearts exhibited a dose-dependent decrease in LV function that was modest compared with that observed in rabbits that had elevated P-R products during in vivo NE treatment. Our results suggest that high concentrations of NE may cause modest degrees of LV dysfunction independently of increases in myocardial energy demand, but the LV dysfunction is exacerbated when myocardial energy demand is elevated.

MRI of the athletic knee. Findings in asymptomatic professional basketball and collegiate football players.

For the dedicated athlete in whom minor injuries are frequent and major injuries relatively common, a noninvasive knee assessment could either obviate the need for arthroscopy or focus its direction. The opportunity to study asymptomatic athletes was not feasible before the advent of magnetic resonance imaging (MRI). In this preliminary work, we examined 40 knees in 20 asymptomatic volunteer athletes, including five professional basketball players and 15 collegiate football players. Images were obtained at 0.5 T or 1.5 T. Spin echo sequences were used to obtain 5.0 mm thick coronal and sagittal sections. Fifty percent of asymptomatic athletes (10/20) had significant baseline MRI abnormalities that could have adversely affected scan interpretation in the context of an acute injury. Half of these athletes with MRI abnormalities, or 25% of the total (5/20), had no previous surgery and were unaware of significant injury.

Occult anterior subluxations of the shoulder in noncontact sports.

Athletes participating in noncontact sports involving abduction and external rotation of the shoulder (e.g., throwing) may develop occult recurrent subluxation manifested only as pain. The lack of contact trauma preceding symptoms, the failure of the athlete to appreciate the instability, the relative rarity that the lesion has been previously recognized and reported, and the lack of objective evidence of instability often lead to incorrect diagnosis by the physician. We report 30 shoulders in 28 patients with this lesion. Nineteen of these patients had been originally seen by other physicians prior to presenting to us and misdiagnosed. The newly described apical oblique roentgenographic projection revealed Hill-Sach's lesions in 23 of 28 patients in this series. In addition, two of the five patients without Hill-Sach's lesions had bony changes pathognomonic for the Bankart lesion on the apical oblique projection. A total of 25 of the 28 patients had objective roentgenographic evidence of previous anterior subluxation. Eleven of the patients had arthroscopic examinations confirming various pathology consistent with anterior subluxation, including anterior or inferior labral tears, Hill-Sach's lesions, anterior inferior glenoid articular cartilaginous erosion, or Bankart lesions. Two of the twenty-eight patients had pathology in addition to evidence of previous occult subluxation which may have played a role in their symptoms, one having had osteolysis of the distal end of the clavicle and another having subacromical adhesions.

Outcome following cardiopulmonary resuscitation in severe pediatric near-drowning.

Between April 1979 and September 1984, 66 children were admitted to the intensive care unit (ICU) at Childrens Hospital of Los Angeles after a severe near-drowning episode. Each patient required full cardiopulmonary resuscitation and had an initial Glasgow coma score (GCS) of 3 in a referring emergency room. Patients were reclassified according to results of a neurologic examination (GCS) on arrival in the ICU. The overall results showed 16 patients (24%) with apparently intact survival, 17 patients (26%) with vegetative survival, and 33 deaths (50%). No patient who arrived at the ICU with a GCS of 3 (flaccid) survived neurologically intact. Out of 37 such patients arriving in flaccid coma, 26 patients died and 11 patients suffered severe brain damage. The majority of patients with GCS of less than 6 underwent intracranial pressure (ICP) monitoring and aggressive therapy directed to control ICP. Despite adequate control of ICP and maintenance of cerebral perfusion pressure, 12 monitored patients survived in a vegetative neurologic state. The results justify aggressive emergency room resuscitation of severe pediatric near-drowning victims but suggest that cerebral resuscitative measures must be subjected to critical prospective evaluation.

The Cybex II evaluation of lateral ankle ligamentous reconstructions.

Chronic lateral ankle instability is a costly disability to the athlete. The Chrisman-Snook and Evans lateral ligamentous reconstructions are two procedures frequently performed to correct ligamentous instability. The entire peroneus brevis tendon is transected in the Evans procedure, thus sacrificing its eversion strength and power. The importance of preserving the eversion function of the peroneus brevis muscle is speculative, but may be of significance for good long-term results. The ankle eversion strength and power of 10 patients with Chrisman-Snook and 10 patients with Evans lateral ligamentous reconstructions were objectively evaluated with the Cybex II Isokinetic Dynamometer. The mean postoperative time to testing was 4.2 years. The uninvolved ankle was also tested and used as the normal strength of the patient. Twenty normal controls matched for age, sex, and physical activity were tested to assure maximum test reproducibility. The eversion strength was tested at several speeds, but torque values at speeds of 30 and 120 deg/sec were selected for analysis. At slow speeds, 30 deg/sec, and ankles that had Evans and Chrisman-Snook reconstruction were 4% and 7% weaker, respectively, than the contralateral normal ankles. At 120 deg/second the ankles were 8% and 9% weaker with the Evans and Chrisman-Snook reconstructions, respectively. A three factor analysis of variance with repeated measures on two of the factors was used to analyze the data.(ABSTRACT TRUNCATED AT 250 WORDS)

Traumatic dislocations of the peroneal tendons.

Traumatic dislocation of the peroneal tendons is an often unrecognized injury which has been reported to occur most commonly during snow skiing. The strength of the peroneal retinaculum is exceeded during resistance to violent passive dorsiflexion or to inversion stress. Pain, swelling, and ecchymosis may hinder early diagnosis; however, intense retromalleolar pain on active eversion is a specific, highly suggestive finding. Fracture of a thin shell of the lateral malleolar cortex is diagnostic. In chronic cases, marked dislocation of the tendons is frequently demonstrable, with more than the usual degree of snapping. Surgical repair is advocated, using one of several procedures available. Most acute cases can be treated by simple repair of the torn or fractured structures. In chronic cases, or in acute cases with deficient structures predisposing to dislocation, it is necessary to reconstruct the peroneal retinaculum and/or deepen the peroneal groove. Longitudinal splitting of the peroneus brevis tendon was a new finding in this series.

A review of lateral ankle ligamentous reconstructions.

We have performed on ongoing retrospective and prospective multi-institutional review of 50 patients who underwent 53 lateral ligamentous reconstructive procedures of the ankle. The point grading system used for postoperative evaluation of our patients allowed for classification of functional activity. The grading system included evaluation of the patient's return to preinjury activities and athletics, degree of pain, degree of swelling, number of recurrent sprains, and any disability that the patient incurred secondary to the tendon transfer. Preoperative and postoperative stress radiographs were obtained to evaluate the talar tilt angle. Of our 53 lateral ankle ligamentous reconstructions, we consider 45 to be excellent, with the patients returning to full activity and athletics. Our results show no statistically significant difference in long-term function among the five ligamentous repairs employed in this series (Pearson Chi-square test; chi 2 = 2.30, df = 4, P = 0.68). No correlation could be made between the long-term clinical response of the various procedures and the postoperative talar tilt angle. We conclude that lateral ligamentous reconstructive repairs of the ankle are indicated, and that good or excellent clinical results, greater than 91%, can be obtained with any of the five reconstructive procedures, performed correctly.

Selective chemical hepatic sympathectomy in the dog.

Intraportal injection of 6-hydroxydopamine (6-OHDA) was used to produce selective hepatic sympathectomy in the dog. Previously reported techniques for 6-OHDA induced hepatic sympathectomy in rats and cats were modified considerably using alpha and beta adrenergic blocking agents to prevent the otherwise intense and fatal sympathomimetic response which has prevented adaptation of the intraportal 6-OHDA injection for dogs. After 6-OHDA injection, histofluorescent staining demonstrated loss of hepatic adrenergic nerves with preservation of normal adrenergic innervation in the heart and pancreas. Tyramine iv was used to further document functional integrity of peripheral sympathetic mechanisms. This technique provides a useful model for evaluation of sympathetic nervous system mediated changes in hepatic metabolic function associated with the neuroendocrine response to hemorrhage in the classic dog model.