Thallium-Technetium isotope subtraction scanning was used routinely as a preoperative localization investigation in 90 patients with primary hyperparathyroidism who were submitted to "first-time" cervical exploration from 1985 to 1988. When the scintigram demonstrated a single focus of activity suggesting the site of a solitary parathyroid adenoma, a scan-directed exploration was carried out. If the tumor was found at the location suggested by the scan, it was then removed and the ipsilateral normal parathyroid was biopsied. The contralateral side of the neck was not explored in these patients. A total of 48 patients underwent unilateral cervical exploration while the remaining 42 individuals had a standard bilateral neck operation performed. The difference in operating times for patients who had a solitary adenoma and who underwent unilateral and bilateral neck exploration, respectively, was statistically highly significant (71 minutes versus 97 minutes, p less than 0.001). At mean follow-up of 16.8 months, no patient who had a unilateral neck exploration performed for solitary parathyroid adenoma demonstrated persistent or recurrent hypercalcemia.

Adenoma↗

PubMedDate not supplied

Can a single vasodilator be responsible for both coronary autoregulation and metabolic vasodilation?

To test the hypothesis that both coronary autoregulation and metabolic vasodilation can be mediated by the same substance, we have analysed measured autoregulation curves with the aid of a simple mass balance model. In an open-chest dog preparation, increasing the heart rate by pacing results in a nearly parallel shift of the autoregulation curve to a higher flow (Q) level. We assume a unique relationship between vascular conductance and interstitial concentration of a vasodilating substance [A]. Applying a compartmental mass balance, it is possible to predict with a minimum of assumptions the increase of flow between two points with increased production but having the same vasodilator concentration. The simple result of this analysis is: delta Q = delta production/[A]. If the vasodilator concentration varies by more than a factor 2 between low and high conductance points, the autoregulation curve cannot shift in a parallel fashion as a result of an increased production rate, but rather will become less and less steep. We conclude that a single vasodilator cannot be responsible for both autoregulation and metabolic vasodilation unless complex assumptions are made, for which there is as yet no experimental support.

Adenosine↗