Twice-daily anesthesia in infants receiving hyperfractionated irradiation.

Four children ranging in age from 6-30 months were treated with twice-daily (BID) radiation therapy under general anesthesia with a 5-6 hr treatment interval. Anesthesia was accomplished with sodium thiopental administered intravenously (IV) by bolus injection. This as followed by continuous drip infusion of sodium thiopental in a few instances where more prolonged anesthesia was required. Children received an initial formula feeding 6 hr before their first treatment and were subsequently kept NPO (nothing by mouth) until they recovered from their second anesthesia. Recovery from thiopental was rapid and children were ready for a normal feeding within 1-1 1/2 hr of the second treatment. No parenteral feedings were required in any of these patients. Children maintained their weight during courses of radiation therapy which ranged between 19 and 43 elapsed days. There were no radiation-related treatment breaks. One child experienced two hypotensive episodes during anesthesia which responded rapidly to intravenous atropine. No other anesthetic complications occurred. This experience demonstrates that hyperfractionated radiation therapy can be safely delivered in infants requiring general anesthesia for immobilization. We feel that sodium thiopental is the anesthetic of choice in this setting because of the short duration of action and consequently rapid post-anesthesia recovery which makes it possible to achieve adequate nutrition with oral feedings alone.

Calcium and magnesium content of skeletal muscle. Studies in subjects undergoing diagnostic testing for malignant hyperthermia.

Ca2+ and Mg2+ contents were measured and compared among three different malignant hyperthermia susceptible (MHS) diagnostic groups. No difference was found among mean values for Ca2+ content, whereas Mg2+ content was greater in MHS muscle. Variance of measured values was unequal and greatest among MHS muscles, suggesting a possible abnormal distribution associated with MHS. Although more muscle fibres with Ca2+ less than or equal to 12 mumol g-1 were observed in MHS muscle, this difference was not statistically significant. In contrast, non-parametric analysis showed that the population of Mg2+ values was significantly greater in the MHS muscle. This study suggests that the distribution of Ca2+ and Mg2+ values is different in MHS muscle as a result of unknown genetic factors associated with the disease.

Comparison of Ca++ uptake and spontaneous Ca++ release from sarcoplasmic reticulum vesicles isolated from muscle of malignant hyperthermia diagnostic patients.

Inward Ca++ transport and spontaneous Ca++ release activities were compared among sarcoplasmic reticulum (SR) membrane fractions isolated from human skeletal muscle in patients undergoing malignant hyperthermia (MH) diagnostic contracture testing. Two different membrane fractions were isolated, a heavy (8-12,000 X g) and light (12-48,000 X g) fraction, from each diagnostic subject. The rates of inward Ca++ transport were faster in light SR compared to heavy SR, but no statistically significant difference was observed among MH diagnostic groups. Spontaneous Ca++ release occurred at optimum Ca++ preload in all SR fractions and this preload did not differ among MH diagnostic groups. Optimal Ca++ preload for rate of spontaneously released Ca++ was greater in light SR compared to heavy SR. Similarly, rate of Ca++ release was faster in light SR than in heavy SR, but no difference in rate of spontaneously released Ca++ was observed among MH diagnostic groups. Amount of Ca++ released did not differ among SR fractions and it did not differ among diagnostic groups. In contrast to previous studies showing a defect in Ca++-induced Ca++ release, the mechanisms related to spontaneous Ca++ release and to oxalate-facilitated inward Ca++ transport, as measured in this study, appear to be normal in SR from human MH skeletal muscle.