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Chlorophyll is a pyrrolic pigment with important optical properties, which is the reason it has been studied for many years. Recently, interest has been rising with respect to this molecule because of its outstanding physicochemical properties, particularly applicable to the design and development of luminescent materials, hybrid sensor systems, and photodynamic therapy devices for the treatment of cancer cells and bacteria. More recently, our research group has been finding evidence for the possibility of preserving these important properties of substrates containing chlorophyll covalently incorporated within solid pore matrices, such as SiO2, TiO2 or ZrO2 synthesized through the sol-gel process. In this work, we study the optical properties of silica xerogels organo-modified on their surface with allyl and phenyl groups and containing different concentrations of chlorophyll bonded to the pore walls, in order to optimize the fluorescence that these macrocyclic species displays in solution. The intention of this investigation was to determine the maximum chlorophyll a concentration at which this molecule can be trapped inside the pores of a given xerogel and to ascertain if this pigment remains trapped as a monomer, a dimer, or aggregate. Allyl and phenyl groups were deposited on the surface of xerogels in view of their important effects on the stability of the molecule, as well as over the fluorescence emission of chlorophyll; however, these organic groups allow the trapping of either chlorophyll a monomers or dimers. The determination of the above parameters allows finding the most adequate systems for subsequent in vitro or in vivo studies. The characterization of the obtained xerogels was performed through spectroscopic absorption, emission and excitation spectra. These hybrid systems can be employed as mimics of natural systems; the entrapment of chlorophyll inside pore matrices indicates that it is possible to exploit some of the most physicochemical properties of trapped chlorophyll for diverse technological applications. The data herein collected suggest the possibility of applying the developed methodology to other active, captive molecules in order to synthesize new hybrid materials with optimized properties, suitable to be applied in diverse technological fields.

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Assuntos

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Polymorphous silicon thin films (pm-Si) have been deposited from mixtures of dichlorosilane and hydrogen, using argon as the diluting gas by plasma-enhanced chemical vapor deposition. The deposition conditions were chosen to simultaneously obtain both Si nanocrystallites and an amorphous silicon matrix in the as-grown samples. High resolution transmission electron microscopy studies show the crystallinity of Si domains whose dimensions are in the interval of 2-14 nm. The surface passivation state of the silicon nanocrystals was inferred from Fourier transform infrared spectroscopy analysis. Two optical absorption edges, corresponding to the amorphous matrix and the Si nanocrystals, were observed for all the pm-Si thin films. Intense visible photoluminescence was observed for the as-grown samples. The possibility of using these thin films for the down-conversion effect in silicon solar cells is discussed.

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We report two cases of early-onset pressure pneumocephalus, one occurring during supratentorial brain surgery (craniopharyngioma) which was diagnosed at the end of the anesthetic period upon appearance of comatose status leading to the suspicion of surgical complication in the form of a hematoma. The second case of pneumocephalus was detected after posterior fossa surgery performed with the patient in the sitting position. We review the significance of our anesthetic management on the prevention of tension pneumocephalus, and discuss diagnostic and therapeutic measures available for use in the Postoperative Intensive Care Recovery Unit.

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We report the case of a 54-year-old woman with cephalea of five months duration caused by a chronic subdural hematoma that appeared after epidural anesthesia and accidental dural puncture for bilateral saphenectomy. Computed tomography of the brain revealed an intracranial hematoma. After surgical evacuation, the patient's headaches resolved and she recovered fully. The appearance of cephalea after dural puncture is a relatively frequent complication of spinal anesthesia, but its persistence over time, as well as changes in its initial characteristics, should lead to a suspicion of life-threatening subdural hematoma.

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OBJECTIVE: To determine whether provision of an information sheet during the preanesthesia visit to the patient, and general recommendations for anesthesia, can change patients' image of the anesthesiologist. PATIENTS AND METHODS: Two groups of 100 patients each were studied before outpatient surgery. Group 1 (given no information) answered a questionnaire before an interview with the anesthesiologist. Group 2 (who were given information) answered the same questionnaire, which was accompanied by an information sheet explaining the nature of anesthesia, possible risks, operating room and postoperative procedures. RESULTS: In group 1,67% identified the anesthesiologist as a physician. In group 2, 99% (p < 0.05) were able to do so. In group 1, 48% believed that the anesthesiologist works under the surgeon's orders, while only 27% (p < 0.05) thought so in group 2. The chief of the postanesthesia intensive care unit was thought to be a member of the nursing staff by 48% in group 1, whereas 95% (p < 0.05) in group 2 identified the chief as an anesthesiologist. CONCLUSIONS: The image of anesthesiology and the anesthesiologist can be improved by systematically providing an information sheet to patients who are scheduled for presurgical study.

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We divided 80 patients undergoing cataract surgery into two groups of 40: one control group and one propofol group to whom 1-1.5 mg/kg of propofol was administered before retrobulbar anesthesia. The following parameters were recorded before and after retrobulbar anesthesia: systolic and diastolic arterial pressure (SAP and DAP), heart rate (HR) and finally arterial oxygen saturation through pulse oximetry. Pain was also measured on the Scott-Huskisson visual analog scale. For patients in the control group a rise in arterial pressure over baseline values after 5 minutes (p < 0.01) was observed, while a decrease was found in the propofol group (p < 0.01). The rise after 5 minutes in the control group was significant when compared with the measurements for the propofol group (p < 0.01). The pain measure for the control group reached 5.53 +/- 1.54 on the Scott-Huskisson scale, but was 0 in the propofol group. Measurements on the pain scale correlated positively with diastolic arterial pressure 5 minutes after blockade in the control group (p < 0.05). The technique studied affords greater comfort for the patient, presents no special difficulties for the anesthesiologist performing the retrobulbar blockade, and causes no complications.

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OBJECTIVES: Comparative study of clinical characteristics and complications during induction, maintenance, and recovery in pediatric inhalational anesthesia between two commonly used fluoride agents (halothane and isoflurane). MATERIAL AND METHODS: We studied 66 children aged 1 month to 13 years undergoing general anesthesia for short lasting surgery who were divided into two groups of 33 patients each one: Isoflurane group and halothane group. Induction and maintenance anesthesia was performed with the corresponding inhalant agent. Parameters measured were duration of unconsciousness, time elapsed for intubation and recovery, heart rate, arterial blood pressure, and incidence of complications. RESULTS: Children anesthetized with isoflurane showed a shorter period of unconsciousness (1.55 +/- 0.11 min) than those anesthetized with halothane (1.91 +/- 0.12 min); whereas that the time required for intubation was significantly more prolonged (8.94 +/- 0.51 and 6.57 +/- 0.32 min, respectively). The incidence of complications was higher in the isoflurane group, mainly expressed as laryngeal spasm during the induction period. Both groups of patients showed a similar hemodynamic behaviour, although diastolic arterial pressure during maintenance anesthesia was significantly lower with isoflurane. Anesthesia recovery was faster and more predictable with isoflurane than with halothane. CONCLUSIONS: Anesthetic agent isoflurane is less appropriate than halothane for induction in pediatric anesthesia due to a high incidence of complications, specially laryngeal spasm.

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We compare the degree of nitrous oxide diffusion in three types of endotracheal tubes available in the market, by means of continuous monitoring of the pressure attained at the pneumoballoon. Among the systems designed to impede or to minimize nitrous oxide diffusion, we have used in this study the so called "rediffusion system". When the endotracheal tube possesses this system, the pressure attained at the pneumoballoon remained constant throughout the study period (23.2 +/- 0.53 mmHg at time zero vs 24.2 +/- 0.66 mmHg 50 min after administration of protoxide). In contrast, endotracheal tubes without "rediffusion system" showed a statistically significant increase (p less than 0.05) of pneumoballoon pressure (25.2 +/- 2.43 mmHg and 26.7 +/- 1.01 mmHg at time zero vs 45.2 +/- 3.12 and 44.3 +/- 2.41 mmHg 50 min after protoxide administration in the two other types of endotracheal tubes). We believe that during anesthesia with nitrous oxide the pneumoballoon pressure should be monitored or systems that avoid diffusion of this inhalational agent should be inserted. Our results indicate that endotracheal tubes equiped with "rediffusion system" are effective in impeding diffusion of the inhalational agents.

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