Jane L. Tyler

Cerebral Blood Volume is Increased in Dogs during Administration of Nitrous Oxide or Isoflurane

Positron emission tomography was used to study the effects of nitrous oxide (N2O) and isoflurane on regional cerebral blood volume (rCBV) in dogs during normocapnia and hypocapnia. Regional cerebral blood volume was measured serially during the addition of 50% N2O to a background anesthetic of fentanyl in normocapnic (group 1) and hypocapnic (PaCO2 25 mmHg, group 2) dogs. In each group, after 15 min of N2O administration accompanied by rCBV measurement, elimination of N2O with 100% O2 was continued for 15 min. This was followed by introduction of 2% isoflurane (no N2O), again accompanied by serial measurements of rCBV. In the normocapnic animals, the addition of 50% N2O caused an 11% increase in rCBV (6.1 ± 1.4 to 6.8 ± 1.0 ml/100 g, P < 0.02) while 2% isoflurane caused a 36% increase (6.1 ± 1.3 to 8.0 ± 1.7 ml/100 g, P < 0.02). The initial induction of hypocapnia during infusion of fentanyl in group 2 animals was associated with a 17% decrease in rCBV. In the hypocapnic dogs, there was no change in rCBV when N2O was introduced; however, an increase of 15% occurred following the addition of isoflurane (3.9 ± 0.6 to 4.5 ± 0.7 ml/100 g, P < 0.02). Isoflurane, even during hypocapnia, may increase cerebral blood volume which in some circumstances may lead to an increase in ICP.

Early diagnosis of myositis ossificans with Tc-99m diphosphonate imaging

Myositis ossificans is primarily a disorder of young adults, whereby an area of muscle mass undergoes progressive ossification. The authors review a case in which the patients presentation was somewhat atypical, and where the course of disease was unusually prolonged. Examination of the soft tissue lesion using Tc-99m diphosphonate bone scans was helpful in establishing the diagnosis and in determining the full extent of the process early in its evolution.

Measurement of Cerebral Blood Flow and Volume with Positron Emission Tomography during Isoflurane Administration in the Hypocapnic Baboon

Using positron emission tomography, cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured after the addition of isoflurane (1.3 vols %, end-tidal concentration) to neuroleptanesthesia (fentanyl/droperidol) in hypocapnic baboons. The study was designed to determine whether isoflurane, when administered during hypocapnia, acted as a cerebral vasodilator to increase either CBF or CBV. Mean arterial pressure was maintained within 10% of preisoflurane levels with an angiotensin infusion. In the first protocol (A), CBF and CBV were measured as close together in time as possible in order to detect divergent effects of isoflurane on these variables. When PaCO2 was reduced from 40 mmHg to 25 mmHg, CBF decreased from 44 +/- 4 to 31 +/- 4 ml.100 g-1.min-1 (P less than 0.05) and CBV decreased from 3.1 +/- 0.3 to 2.6 +/- 0.3 ml/100 g (P less than .05). Neither CBF nor CBV was significantly changed by the addition of isoflurane. In the second protocol (B), serial CBV scans were performed frequently during the addition of isoflurane in a fashion designed to detect transient changes in CBV at the time isoflurane was first added to the breathing circuit. Induction of hypocapnia again reduced CBV from 3.1 +/- .3 to 2.7 +/- .2 ml/100 g, (P less than .05) and addition of isoflurane did not change CBV. From these results the authors conclude that in the normal hypocapnic baboon the addition of 1.3% isoflurane does not significantly change cerebral blood flow or volume.

Tc-99m DTPA uptake in soft tissue sarcoma.

A case of spindle-cell sarcoma which demostrates intense uptake of Tc-99m DTPA is presented.

Orbital accumulation of gallium-67 citrate

In order to determine the normal range of Gallium-67 citrate (Ga-67) accumulation in the orbital regions, and to possibly identify groups tending to have increased Ga-67 concentration in the eyes, 75 studies were performed prospectively over a two-month period. No difference in the ocular count/background ratio was found on the basis of sex, or on the basis of symptomatic ocular involvement in a systemic disease process. A significant difference in this ratio was found between age groups separated by 20 years or more, with younger patients tending to have higher ocular counts. This decrease in the ratio with age possibly reflects the physiologic senile involution of the lacrimal apparatus with time. The wide range of normal ocular Ga-67 accumulation should be kept in mind, and demonstrable Ga-67 concentration in the orbital regions need not be automatically ascribed to a pathologic process.