Perioperative management of pediatric patients undergoing juvenile angiofibroma resection. A case series and educational review highlighting patient blood management.

BACKGROUND: Juvenile nasopharyngeal angiofibromas are one of the most enigmatic, bloody tumors encountered by otorhinolarygnologists, head and neck surgeons, neurosurgeons, and anesthesiologists. Juvenile nasopharyngeal angiofibromas are rare, benign, highly vascular tumors with a propensity towards aggressive local invasion. Surgery, open or endoscopic, to remove the growth is the primary treatment of choice for Juvenile nasopharyngeal angiofibromas. Historically, surgical resection was associated with massive, rapid blood loss, traditionally managed by blood product transfusion and deliberate hypotension. Preventative management employing multimodal blood conservation strategies should be an essential standard of perioperative care for patients with Juvenile nasopharyngeal angiofibromas. METHODS: We describe a contemporary and comprehensive approach in the management of patients with high grade Juvenile nasopharyngeal angiofibromas. This includes surgical strategies such as preemptive external carotid artery embolization, endoscopic surgical approach, and staged operations, as well as anesthetic strategies including antifibrinolytic therapy and acute normovolemic hemodilution. These surgeries, once synonymous with massive transfusion, may potentially be performed without allogeneic blood transfusion, or deliberate hypotension. AIMS: Using a case series, the authors introduce a contemporary approach to multimodal, multidisciplinary blood conservation strategies for Juvenile nasopharyngeal angiofibromas surgery. RESULTS: Here in the authors report on an updated contemporary perioperative clinical approach to patients with Juvenile nasopharyngeal angiofibromas. From an anesthetic perspective, we describe the successful use of normal hemodynamic goals, restrictive transfusion strategy, antifibrinolytic therapy, autologous normovolemic hemodilution, and early extubation in the care of three adolescent males with highly invasive tumors. We demonstrate that new surgical and anesthetic strategies have yielded a significant decrease in intraoperative blood loss and eliminated the need for transfusion of autologous red blood cells, which enable improved outcomes. CONCLUSIONS: The perioperative approach to elective surgery for Juvenile nasopharyngeal angiofibromas management is presented from a multidisciplinary patient blood management perspective.

Clinically shaped fields: relative outputs for Varian multileaf collimators and tray-mounted cerrobend blocks.

The purpose of this study was to determine the variation in relative output factors for fields shaped using a multileaf collimator (MLC) versus tray-mounted cerrobend blocks. A total of 21 different clinical fields from 16 patients were compared by casting cerrobend blocks from the same films that had generated the MLC shapes. Output measurements were made on a Varian 2300CD (26 1 cm leaves per side) in solid water for 6 and 20 MV at source-to-axis-distance (SAD = 100 cm) and at two depths, 5 cm (d5) and the clinically prescribed depth (d(clinical)). All measurements were taken under the central axis of the beam unless the shaped field was obviously skewed off axis or the beam was split. Several cases were repeated on a Varian 2100CD (40 1 cm leaves per side) MLC. For the 21 cases studied, the average overall MLC factor (MLC reading divided by the block reading) was found to be 0.9952 with a standard deviation of 0.0024. Repeat measurements performed on the 2100CD were within 0.2% of the MLC factors measured (for the same fields) on the 2300CD. When the data are broken down in terms of clinical applications (type of case at a clinically prescribed depth and energy), the resulting total clinical average is 0.9957 with a standard deviation of 0.0022. Both the overall average and the total clinical average MLC factors (0.995-0.996) agree with previous literature, which used abstract or generic field shapes. Further investigation of the data from this study may find a correlation between the MLC factor and the percent of open field.

Noncontact dipole effects on channel permeation. I. Experiments with (5F-indole)Trp13 gramicidin A channels.

Gramicidin A (gA), with four Trp residues per monomer, has an increased conductance compared to its Phe replacement analogs. When the dipole moment of the Trp13 side chain is increased by fluorination at indole position 5 (FgA), the conductance is expected to increase further. gA and FgA conductances to Na+, K+, and H+ were measured in planar diphytanoylphosphatidylcholine (DPhPC) or glycerylmonoolein (GMO) bilayers. In DPhPC bilayers, Na+ and K+ conductances increased upon fluorination, whereas in GMO they decreased. The low ratio in the monoglyceride bilayer was not reversed in GMO-ether bilayers, solvent-inflated or -deflated bilayers, or variable fatty acid chain monoglyceride bilayers. In both GMO and DPhPC bilayers, fluorination decreased conductance to H+ but increased conductance in the mixed solution, 1 M KCl at pH 2.0, where K+ dominates conduction. Eadie-Hofstee plot slopes suggest similar destabilization of K+ binding in both lipids. Channel lifetimes were not affected by fluorination in either lipid. These observations indicate that fluorination does not change the rotameric conformation of the side chain. The expected difference in the rate-limiting step for transport through channels in the two bilayers qualitatively explains all of the above trends.

How big is a pinhole?

Numerical estimates are formulated for the pinhole size required for a distortion free pinhole camera. The appropriate formulas are shown for both large and small pinholes.