Accuracy of a cerebral oximeter in healthy volunteers under conditions of isocapnic hypoxia.

BACKGROUND: A cerebral oximeter measures oxygen saturation of brain tissue noninvasively by near infrared spectroscopy. The accuracy of a commercially available oximeter was tested in healthy volunteers by precisely controlling end-tidal oxygen (P[ET]O2) and carbon dioxide (P[ET]CO2) tensions to alter global cerebral oxygen saturation. METHODS: In 30 healthy volunteers, dynamic end-tidal forcing was used to produce step changes in P[ET]O2 resulting in arterial saturation ranging from approximately 70% to 100% under conditions of controlled normocapnia (each person's resting P[ET]CO2) or hypercapnia (resting plus 7-10 mmHg). Blood arterial (SaO2) and jugular bulb venous (S[jv]O2) saturations during each P(ET)O2 interval were determined by co-oximetry. The cerebral oximeter reading (rSO2) and an estimated jugular venous saturation (S[jv]O2), derived from a combination of SaO2 and rSO2, were compared with the measured S(jv)O2. RESULTS: The S(jv)O2 was significantly higher with hypercapnia than with normocapnia for the same SaO2. The rSO2 and S(jv)O2 were both highly correlated with S(jv)O2 for individual volunteers (mean r2 = 0.91 for each relation); however, the slopes and intercepts varied widely among volunteers. In three of them, the cerebral oximeter substantially underestimated the measured S(jv)O2. CONCLUSIONS: During isocapnic hypoxia in healthy persons, cerebral oxygenation as estimated by near infrared spectroscopy precisely tracks changes in measured S(jv)O2 within individuals, but the relation exhibits a wide range of slopes and intercepts. Therefore the clinical utility of the device is limited to situations in which tracking trends in cerebral oxygenation would be acceptable.

Use of esmolol to control bleeding and heart rate during electroconvulsive therapy in a patient with an intracranial aneurysm.

Electroconvulsive therapy (ECT) is a commonly used treatment modality for patients with major affective disorders that are unresponsive to pharmacological therapy. While ECT has been shown to be a very safe treatment, it is associated with transient hemodynamic alterations, including hypertension, which are associated with an increased risk of rupture of an intracranial aneurysm. We describe our use of the ultrashort acting beta-blocker, esmolol, for blood-pressure control in a woman with known cerebral aneurysmal disease who required ECT for treatment of recurrent major depression.

Transesophageal echocardiography and the intraoperative management of pediatric congenital heart disease: initial experience with a pediatric esophageal 2D color flow echocardiographic probe.

Intraoperative color Doppler transesophageal echocardiography (TEE) was performed in 26 patients undergoing corrective or palliative surgery for congenital heart disease. Age ranged from 1 day to 15 years, and body weight ranged from 2.9 to 42 kg. Objectives of the study were to determine the smallest infant in whom the pediatric probe could be used safely, additional diagnostic value, and it role in the intraoperative assessment of the surgical repair. The insertion of the pediatric probe was possible in all 26 patients. The smallest infant in this series was a newborn weighing 2.9 kg. Excellent correlation was obtained with preoperative transthoracic echocardiographic findings and operative findings. Assessment of the surgical repair was obtained in the immediate postcardiopulmonary bypass period. No short-term complications occurred in this series. Intraoperative color Doppler TEE provided a detailed and accurate assessment of the morphology, the function of the heart, and altered the management of at least two patients.

The site-specific ribosomal insertion element type II of Bombyx mori (R2Bm) contains the coding sequence for a reverse transcriptase-like enzyme.

Two classes of DNA elements interrupt a fraction of the rRNA repeats of Bombyx mori. We have analyzed by genomic blotting and sequence analysis one class of these elements which we have named R2. These elements occupy approximately 9% of the rDNA units of B. mori and appear to be homologous to the type II rDNA insertions detected in Drosophila melanogaster. Approximately 25 copies of R2 exist within the B. mori genome, of which at least 20 are located at a precise location within otherwise typical rDNA units. Nucleotide sequence analysis has revealed that the 4.2-kilobase-pair R2 element has a single large open reading frame, occupying over 82% of the total length of the element. The central region of this 1,151-amino-acid open reading frame shows homology to the reverse transcriptase enzymes found in retroviruses and certain transposable elements. Amino acid homology of this region is highest to the mobile line 1 elements of mammals, followed by the mitochondrial type II introns of fungi, and the pol gene of retroviruses. Less homology exists with transposable elements of D. melanogaster and Saccharomyces cerevisiae. Two additional regions of sequence homology between L1 and R2 elements were also found outside the reverse transcriptase region. We suggest that the R2 elements are retrotransposons that are site specific in their insertion into the genome. Such mobility would enable these elements to occupy a small fraction of the rDNA units of B. mori despite their continual elimination from the rDNA locus by sequence turnover.