The authors represent a cooperative group of 15 institutions that examined the feasibility of using metabolic fea tures observed in vivo with 'H-magnetic resonance (MR) spectroscopy to characterize brain tumors of the glial type.The institutions provided blinded, centralized MR spectroscopy data processing along with independent central review of MR spectroscopy voxel placement, composition and contamination by brain, histopathological typing using current World Health Organization criteria, and clinical data, Proton 'H-MR spectroscopy was performed using a spin-echo technique to obtain spectra from 8-cc voxels in the tumor and when feasible in the contralateral brain. Eighty-six cases were assessable, 41 of which had contralateral brain spectra. Glial tumors had significantly elevated intensities of choline signals, decreased intensities of creatine signals, and decreased intensities of N-acetyl asp art ate compared to brain. Choline signal intensities were highest in astrocytomas and anaplastic astrocytomas, and creatine signal intensi ties were lowest in glioblastomas. However, whether expressed relative to brain or as intratumoral ratios, these meta bolic characteristics exhibited large variations within each subtype of glial tumor. The resulting overlaps precluded diagnostic accuracy in the distinction of low-and high-grade tumors. Although the extent of contamination of the ]H-MR spectroscopy voxel by brain had a marked effect on metabolite concentrations and ratios, selection of cases with minimal contamination did not reduce these overlaps. Thus, each type and grade of tumor is a metabolically hetero geneous group. Lactate occurred infrequently and in all grades. Mobile lipids, on the other hand, occurred in 41% of high-grade tumors with higher mean amounts found in glioblastomas. This result, coupled with the recent demonstra tion that intratumoral mobile lipids correlate with microscopic tumor cell necrosis, leads to the hypothesis that mobile lipids observed in vivo in E H-MR spectroscopy may correlate independently with prognosis of individual patients. W. G. Negendank, et ciL rylcholine), one primarily from creatines (creatine and phosphocreatine), and one primarily from acetyl aspar tate (NAA), In disease, signals from lactate and mobile lipids may also be observed.Studies of extracts of surgical specimens of human as trocytic tum ors using ]H -N M R spectroscopy indicated an increase in the ratio o f cholines to creatines, and a decrease in the ratio of N A A to creatines, with increas ing histopathological grades of m alignancy.16,45'61 Studies in patients using !H-N M R spectroscopy, referred to as MR spectroscopy, indicated sim ilar correlations betw een m etabolic features in vivo and the histopathological grades of astrocytic tum ors. 4'11'14'21,32,43'57'58'61 Other MR spectroscopy studies indicated that lactate is more likely to be present in high-than in low-grade tumors4, 14,15'20'21 and that the am ount of lactate may correlate with the extent of hyperm etabolic glucose consumption sho...

We evaluated the rate of complications experienced by children who undergo adenotonsillectomy for obstructive sleep apnea syndrome (OSAS), the safety of a standard anesthetic protocol for these children, and preoperative predictors of complications. Sixty-one children with OSAS, confirmed by polysomnography, and 21 children with recurrent tonsillitis were anesthetized using a standard protocol before adenotonsillectomy (ages 2-16 yr, ASA 1-3). The number of complications and medical interventions in the perioperative period were recorded and correlated with the presence and severity of OSAS. Children with OSAS had more respiratory complications per operation than non-OSAS children (5.7 vs 2.9, P < 0.0001). Supraglottic obstruction, breath holding, and desaturation on anesthetic induction and emergence were the most common complications. Increased severity of OSAS, low weight, and young age are correlated with an increased rate of complications. Medical intervention was necessary in more children with OSAS during recovery and emergence than in the non-OSAS group (17/61 vs 1/21, P < 0.05). Both groups of children had similar opioid requirements and time to discharge from the recovery room. These findings suggest that children with OSAS are at risk for respiratory complications after adenotonsillectomy, but that these complications do not prolong the time to discharge.

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