Modeling the role of osmotic forces in the cerebrovascular response to CO2.

Increases in blood osmolarity have been shown to exert a vasodilatory effect on cerebral and other vasculature, with accompanying increases in blood flow. It has also been shown that, through an influence on blood concentration of the bicarbonate ion and pH, changes in blood levels of CO2 can alter blood osmolarity sufficiently to have an impact on vessel diameter. We propose here that this phenomenon plays a previously unappreciated role in CO2-mediated vasodilation, and present a biophysical model of osmotically driven vasodilation. Our model, which is based on literature data describing CO2-dependent changes in blood osmolarity and hydraulic conductivity (Lp) of the blood-brain barrier, is used to predict the change in cerebral blood flow (CBF) associated with osmotic forces arising from a specific hypercapnic challenge. Modeled changes were then compared with actual CBF changes determined using arterial spin-labeling (ASL) MRI. For changes in the arterial partial pressure of CO2 (PaCO2) of 20 mmHg, our model predicted increases of 80% from baseline CBF with a temporal evolution that was comparable to the measured hemodynamic responses. Our modeling results suggest that osmotic forces could play a significant role in the cerebrovascular response to CO2.

Elimination of visually evoked BOLD responses during carbogen inhalation: implications for calibrated MRI.

Breathing a mixture of 10% CO(2) with 90% O(2) (referred to here as carbogen-10) increases blood flow due to the vasodilatory effect of CO(2), and raises blood O(2) saturation due to the enriched oxygen level. These effects both tend to reduce the level of deoxygenated hemoglobin in brain tissues, thereby reducing the potential for further increases in BOLD contrast. In the present study, blocks of intense visual stimulation (60s) were presented amid longer blocks (180s) during which subjects breathed various fractional concentrations (0-100%) of carbogen-10 diluted with medical air. When breathing undiluted carbogen-10, the BOLD response to visual stimulation was reduced below the level of noise against the background of the carbogen-10 response. At these concentrations, the total (visual+carbogen) BOLD response amplitude (7.5±1.0%, n=6) converged toward that seen with carbogen alone (7.5±1.0%, n=6). In spite of the almost complete elimination of the visual BOLD response, pseudo-continuous arterial spin-labeling on a separate cohort indicated a largely preserved perfusion response (89±34%, n=5) to the visual stimulus during inhalation of carbogen-10. The previously discussed observations suggest that venous saturation can be driven to very high levels during carbogen inhalation, a finding which has significant implications for calibrated MRI techniques. The latter methods involve estimation of the relative change in venous O(2) saturation by expressing activation-induced BOLD signal increases as a fraction of the maximal BOLD signal M that would be observed as venous saturation approaches 100%. While the value of M has generally been extrapolated from much smaller BOLD responses induced using hypercapnia or hyperoxia, our results suggest that these effects could be combined through carbogen inhalation to obtain estimates of M based on larger BOLD increases. Using a hybrid BOLD calibration model taking into account changes in both blood flow and arterial oxygenation, we estimated that inhalation of carbogen-10 led to an average venous saturation of 91%, allowing us to compute an estimated M value of 9.5%.

Resection and end-to-end anastomosis for ascending aortic aneurysm: surgical technique.

Treatment of ascending aortic aneurysm, without involvement of aortic sinuses of Valsalva, is usually treated by tube graft interposition. Nowadays, many alternative techniques were described. The technique of resection and end-to-end anastomosis has been already described both by our group and by other authors as well. This report will focus on some surgical details of this technique based on a ten-year-experience. The preoperative study of candidates amenable to undergo this technique has to be completed by a computed tomography-scan of thoracic aorta. The ideal candidate has an elongated aorta in the antero-lateral wall. As a consequence, the heart is usually displaced inferiorly and toward a more horizontal plane. The aortotomy is done circumferentially one and half cm above the aortic commissures. A wide wedge resection of the aortic wall is performed. The resected aortic wall is wider in the anterior part than in the posterior. A very accurate hemostasis of the fat tissue close to the pulmonary artery is achieved by diathermy. The amount of wedge resection is mainly dictated by the elongation of the aortic wall. In authors' experience it usually ranges between 4 and 6 cm anteriorly and 1 cm posteriorly. The suture of the two stumps is performed by a running suture. The technique described has extensively been used; up today 136 patients undergo. According to authors' opinion this technique can be a useful alternative to the tube graft interposition in selected patients.

Chronic transverse sternal fracture. Role of CT scan and repair by an alternative use of the Synthes-Titanium Sternal Fixation System.

Chest wall fractures, including injuries of the sternum, usually heal spontaneously without specific treatment. However sometimes, they need surgical treatment. To treat these patients the selection criteria often are subjective in spite of many surgical devices for sternal osteosynthesis are available nowadays. One of the most recent device is the Synthes-Titanium Sternal Fixing System, usually used to treat post-sternotomy dehiscence. We describe the case of a 67-year-old man with previous history of chest trauma presenting to our institution with chronic transverse sternal fracture. We describe the pre-operative study, stressing the particular role of the CT scan and a surgical approach by an alternative use of the Synthes.

Active surveillance of Streptococcus pneumoniae bacteremia in Italian children.

There are few data published regarding the incidence of Streptococcus pneumoniae bacteremia in Italian children. A 14-month surveillance study was conducted in 10 paediatric hospitals to investigate the rate of Sp bacteremia in children aged less than 5 years. The serotype prevalence and antimicrobial susceptibility of isolates were determined. A total of 55 Sp isolates were obtained from 4576 blood cultures (incidence rate, 1.2%). In order of frequency, the most common serotypes were 14, 23F, 19F, 9V, 1. Serotypes in the 7-valent conjugate pneumococcal vaccine (4, 6B, 9V, 14, 18C, 19F, 23F) accounted for 70% of isolates under 2 years of age, and 58% in the interval between 2 and 5 years of age.

Effectiveness of hepatitis B vaccination in babies born to hepatitis B surface antigen-positive mothers in Italy.

This study examined 522 children born to hepatitis B surface antigen (HBsAg)-positive mothers from 1985 through 1994 and evaluated the protection provided by anti-hepatitis B virus (HBV) immunization at birth. Babies were given hepatitis B immunoglobulin and hepatitis B vaccine at birth. At 5-14 years after immunization, 17 children (3.3%) were anti-HB core antigen positive, and 3 also were HBsAg positive. One carrier child had a double mutation, with substitution of proline-->serine at codons 120 (P120S) and 127 (P127S) within the a determinant of HBsAg. Of the 522 children, 400 (79.2%) of 505 still had protective anti-HBsAg titers > or =10 mIU/mL. Thus, HBV vaccination of children born to HBsAg-positive mothers is effective and confers long-term immunity. There is no evidence that the emergence of HBV escape mutants secondary to the immune pressure against wild-type HBV is of concern.

Ad hoc survey of hepatitis B vaccination campaign in newborns of HBsAg positive mothers and in 12-year-old subjects in southern Italy.

The ongoing vaccination campaign against hepatitis B (HB) for newborns of hepatitis B surface antigen (HBsAg) positive mothers and for 12-year-old subjects was evaluated in Naples, Italy, an area of relatively high HB endemicity. Subjects were recruited by a random sampling procedure. Among 2060 pregnant women studied, 1887 (91.6%) were screened for HBsAg. HBsAg prevalence was 2.5% (47/1887). Immunoprophylaxis according to the protocol (immunoglobulins within 24 h plus vaccine within 7 days after birth) was administered in 26 (55.3%) out of the 47 newborns of HBsAg positive mothers; vaccination was delayed (later than 7 days after birth) for 14 (29.8%) infants; in the remaining seven newborns (14.9%) were not given immunoglobulins at birth. All infants were vaccinated. Out of the 1000 adolescents sampled 130 (13%) were not found due to an inaccurate census list; 727 (83.3%) of the 870 investigated had received a three-dose HB vaccine series. Overall, the HB vaccination program in Italy is working well. However, further efforts should be made to improve the efficacy and effectiveness of the campaign.

Levels of 4-chloro-2-methylphenoxyacetic acid (MCPA) in the urine of northern italy occupationally exposed agricultural workers.

MCPA residues were assayed in 18 urine samples collected from northern Italy herbicide spraymen. Urine was collected within less than or equal to 24 hr from workshift start and kept at -20 degrees C until analysis. Twenty-five-milliliter urine specimens were ether-extracted at pH 1 and then the free MCPA was turned into its methyl ester. Detection and quantitation were carried out by high-resolution gas chromatography coupled with low-resolution mass spectrometry (hrGC-lrMS) run in the multiple ion detection (MID) mode. Specimen mass chromatograms were referred to MCPA methyl ester external standards. Detection thresholds were 25 and 10 ppb when S/N ratios of approximately 10 and 2.5, respectively, were adopted for the quantitation ion mass. Mean recovery was better than 80% over the full concentration range tested (10-1000 ppb). Urine analysis yielded the following results: eight outcomes fell in the 10-50 ppb range, five outcomes in the 50-150 ppb range, and five in the 150-500 ppb range.

Acute renal failure due to cisplatin.

A case of acute renal failure associated with cisplatin therapy for a stage IV neuroepitelioma of the chest wall is described. This case was associated with a normal magnesium concentration and with presence of fibrinogen in the Tubular Basement Membrane and of IgG in the interstitial infiltrates. Immunological activation was evidentiated by fine needle aspiration biopsy (FNAB) at the time of renal biopsy.

Improved tube for nasojejunal feeding in low birthweight infants.

A simple tube for nasojejunal feeding is described. 22 infants with birthweight less than 1500 g and 25 infants 1500--2000 g were fed during the first weeks of life. The tube elimintes many of the difficulties previously encountered with nasojejunal feeding.