Vagus Nerve Stimulation Induces a Sustained Anticonvulsant Effect

Summary: Purpose: Stimulation of the vagus nerve can effectively abort several types of experimentally induced seizures in animals when administered near the time of seizure onset. Indirect evidence from human trials and animal studies suggests that the anticonvulsant effects of vagus nerve stimulation (VNS) extend beyond the duration of stimulation. We used the pentylenetetrazol model to determine whether VNS exerts a persistent anticonvulsant effect.
Methods: VNS (1 mA, 30 Hz, 500 μs pulse width) was administered continuously for 0, 1, or 60 min, or intermittently (30 s on, 5 min off) for 60 min, to awake and freely moving animals. After the end of stimulation, pentylenetetrazol (50 mg/kg i.p.) was administered to induce seizures. Time-course studies were also performed, consisting of 60 min of VNS followed by pentylenetetrazol injection after 0, 3-, 5-, and 10-min intervals.
Results: The greatest anticonvulsant effect occurred after 60 min of continuous VNS, which prevented convulsions in four of 12 rats and reduced significantly seizure duration, the total number of seizures, and number of tonic seizures. Intermittent VNS was less effective than continuous stimulation for 60 min, but more effective than that for 1 min. The anticonvulsant effect declined in a time-dependent fashion after discontinuation of VNS, with return to nonstimulated control values by 10 min.
Conclusions: The results of this study verify a persistent VNS-induced anticonvulsant effect and indicate that its efficacy is dependent on the cumulative stimulus duration.     

Beneficial Effects of Short-term Vasopressin Infusion during Severe Septic Shock

Background: Septic shock is associated with vasopressin deficiency and a hypersensitivity to its exogenous administration. The goal of the current study was to determine whether short-term vasopressin infusion in patients experiencing severe septic shock has a vasopressor sparing effect while maintaining hemodynamic stability and adequate end-organ perfusion.

Methods: Patients experiencing septic shock that required high-dose vasopressor support were randomized to a double-blinded 4-h infusion of either norepinephrine (n = 11) or vasopressin (n = 13), and open-label vasopressors were titrated to maintain blood pressure. To assess end-organ perfusion, urine output and creatinine clearance, gastric mucosal carbon dioxide tension, and electrocardiogram ST segment position were measured.

Results: Patients randomized to norepinephrine went from a median prestudy norepinephrine infusion of 20.0 [mu]g/min to a blinded infusion of 17.0 [mu]g/min at 4 h, whereas those randomized to vasopressin went from a median prestudy norepinephrine infusion of 25.0 [mu]g/min to 5.3 [mu]g/min at 4 h (P < 0.001). Mean arterial pressure and cardiac index were maintained in both groups. Urine output did not change in the norepinephrine group (median, 25 to 15 ml/h) but increased substantially in the vasopressin group (median, 32.5 to 65 ml/h;P < 0.05). Similarly, creatinine clearance did not change in the norepinephrine group but increased by 75% in the vasopressin group (P < 0.05). Gastric mucosal carbon dioxide tension and electrocardiogram ST segments did not change significantly in either group.     

Laterality, torque and personality

Evidence accumulating from a variety of methodological approaches suggests that unusual laterality is often a concomitant feature of emotional pathology. In the present study both torque and a multifaceted measure of laterality were examined with respect to personality variables measured by the 16 PF in a normal population. Interestingly, a pattern of emotionality for subjects with a more confused laterality was revealed in a normal population which is notably similar to reported aberrant personality factors and laterality in more pathological groups. The existence of a cohesive continuum of emotional expression in relation to confused laterality is suggested. In addition, both torque and the multifactored measure of laterality are critiqued as research measures and for their clinical potential.     

Elevated hypothalamic neuropeptide Y levels in rats with dorsomedial hindbrain lesions

Lesions centered on the area postrema (AP) and adjacent nucleus of the solitary tract (AP/mNTS-lesions) are reported to result in increased consumption of highly palatable diets. Recent studies suggest that neuropeptide Y (NPY) may cause a preference for carbohydrate-rich diets. Thus, it is possible that NPY may play a role in the enhanced intake of highly palatable diets by AP/mNTS-lesioned rats. In the studies reported here, we found that lesions centered on the AP result in increased levels of NPY-immunoreactivity in the paraventricular nucleus of the hypothalamus. Additionally, steady-state NPY mRNA in the basomedial hypothalamus including the arcuate nucleus was elevated. Enhanced NPY was not found throughout the hypothalamus however, as NPY-immunoreactivity was not elevated in the lateral hypothalamus or the tissue bordering the anteroventral third ventricle. These data suggest the possibility that elevated hypothalamic NPY, particularly in the arcuate and paraventricular nuclei, may contribute to the altered food intake and energy balance observed in rats with lesions centered on the AP.     

Laparoscopic bilateral adrenalectomy following failed hypophysectomy

Background: Laparoscopic adrenalectomy has recently been shown to be a safe and effective means of treating adrenal pathology with much lower morbidity than the traditional approach. The majority of reports in the literature involve removal of adrenal tumors. Although open bilateral adrenalectomy has been utilized for persistent Cushing's syndrome following attempted hypophysectomy, there is little data available describing the application of laparoscopic adrenal surgery to this problem. Methods: Four patients with persistent Cushing's syndrome after attempted treatment with hypophysectomy underwent laparoscopic bilateral adrenalectomy at our institution. One procedure was done transabdominally in the supine position. Three procedures were done transabdominally using sequential lateral decubitus positions. Results: All procedures were completed laparoscopically. The mean operative time was 4.6 h (range 3.9–5.25). Repositioning and reprepping the patients resulted in a slight increase in operative time, but visualization was improved using the lateral decubitus position. Average blood loss: 156 cc (range 50–300). One patient required early reoperation for bleeding from the left adrenal bed, which was controlled laparoscopically. Three patients were eating the following day and were discharged on postoperative days 1, 2, and 5. The fourth patient remained hospitalized for 18 days due to problems unrelated to surgery. After a mean follow-up of 10 months, all patients have done well and have no clinical or biochemical evidence of recurrent disease. Conclusion: Our clinical experience indicates that laparoscopic bilateral adrenalectomy is a viable treatment option for Cushing's syndrome following failed hypophysectomy. Received: 29 March 1996/Accepted: 12 June 1996     

Patterns of calcifications and cholangiographic findings in hepatobiliary tuberculosis

The radiologic findings on conventional examinations (plain films and cholangiograms) in a large group of patients with proven hepatobiliary tuberculosis are reviewed. The plain film findings of large chalky and confluent hepatic calcifications or nodal-type calcifications along the course of the common bile duct are suggestive of hepatobiliary tuberculosis. Small, discrete, scattered calcifications may be mimicked by histoplasmosis but can be differentiated from hepatobiliary tuberculosis. Obstructing defects seen on cholangiography are indicative of tuberculosis when adjacent calcifications are present. The patterns of liver calcifications could provide a clue to the diagnosis of hepatobiliary tuberculosis and its differentiation from liver calcifications of various other etiologies.