NICU guidelines for nursing care of the infant with congenital malignancies.

Cancer is a rare occurrence among neonates. NICU nurses must have the knowledge base and skills to comfortably and competently care for infants with this disease and their families. This case study provides an overview of neonatal malignancies and a review of clinical management and chemotherapeutic treatments.

Lymphatic mapping and sentinel lymph node biopsy in the staging of melanoma.

In recent months, we have witnessed a 'paradigm shift' in the management of intermediate-thickness melanoma. The collective experience of the recent past confirms the validity of the 'sentinel' lymph node as being the initial draining site from a specific area of skin. Furthermore, the sentinel lymph node has been confirmed as the most likely site in the regional lymph node basin to harbor occult metastatic disease. Identification of sentinel lymph nodes by visual inspection and intraoperative gamma probe detection after the peritumoral injection of Lymphazurin blue dye and technetium sulfur colloid is a reliable new technique. Staging accuracy also has improved, allowing the precise identification of patients who benefit from avoiding the morbidity of radical lymphadenectomy. The importance of accurate staging has been heightened by data demonstrating effective adjuvant therapy with recombinant interferon-alpha 2B. Precisely defining patient subsets who benefit from adjuvant high-dose interferon-alpha 2B is the current focus of clinical trials designed to maximize the enhanced staging accuracy of the novel approach of sentinel lymph node biopsy.

Bilateral popliteal vein aneurysms.

An 82-year-old man was admitted with a left hip fracture sustained in a fall. The fracture was surgically repaired. Ipsilateral leg swelling developed over the following 2 weeks. A lower extremity venous duplex scan demonstrated isolated dilatation of the popliteal veins in both lower extremities. Chronic thrombosis was noted in both popliteal veins at the level of this dilatation. Initial duplex scanning also revealed acute thrombus in the left popliteal, posterior tibial, and peroneal veins. A repeat scan 1 week later identified propagation of thrombus into the superficial femoral vein. Popliteal vein aneurysms, although rare, can cause significant morbidity and mortality. The literature is also reviewed.

Kinetics and thermodynamics of oxygen, CO, and azide binding by the subcomponents of soybean leghemoglobin.

Leghemoglobin shows extreme high affinity behavior in the binding of both oxygen and CO. We have determined the temperature dependence of the rate constants for ligation of oxygen and CO and from these data the thermodynamics (delta G0, delta H0, delta S0) of ligation for the purified components of soybean leghemoglobin. X-ray crystallography has shown that the heme cavity can easily accommodate ligands the size of nicotinate, and analysis of extended x-ray absorption fine structure data has shown that the Fe atom is in the mean plane of the heme in the leghemoglobin-CO complex. Ligation of oxygen and CO are in accord with this picture in that the Ea for oxygen binding is that expected for a diffusion controlled reaction and delta S0 for the ligation of both CO and oxygen is consistent with the simple immobilization of the ligand at the Fe, with no evidence for significant conformational changes in the protein or changes in solvation. At 20 degrees C the rate constants for oxygen and CO binding vary by 26-44% among the eight leghemoglobin components. For azide binding the variation is a factor of 2. These variations appear to arise from amino acid substitutions outside either the heme cavity or the two major paths for ligand entry to the heme. The distribution of leghemoglobin components varies with the age of the soybean nodule during the growing season. The changes in composition alone, however, would only allow the concentration of free oxygen to vary by about 3%. This finding calls into question models that ascribe a significant functional role to changes in the distribution of leghemoglobin components in regulating oxygen concentration in the nodule.

Kinetics and thermodynamics of oxygen and carbon monoxide binding to the T-state hemoglobin of Urechis caupo.

The tetrameric hemoglobin from Urechis caupo is nearly ideal for studying ligation to the T-state. Our previous EXAFS study had shown that the Fe is displaced 0.35 A from the mean plane of the porphyrin in the HbCO derivative. We have carried out detailed kinetic studies of oxygen and CO ligation as a function of temperature in order to characterize both the kinetics and thermodynamics of ligation in this hemoglobin. The entropy change associated with ligation essentially corresponds to simple immobilization of the ligand and is virtually the same as that we have determined for leghemoglobin, an extreme R-state-type hemoglobin. The low ligand affinities thus derive from small enthalpies of ligation, which can be correlated with the large out of plane displacement of the Fe. Only oxygen pulse measurements revealed kinetic evidence for cooperative oxygen binding, but a direct measurement of oxygen binding gave a Hill number of 1.3. An allosteric analysis gave L = 2.6 and c = 0.048 (oxygen) and c = 0.77 (CO). The higher affinity state in this weakly cooperative hemoglobin is denoted T*, and it is for this state that thermodynamic quantities have been determined. The small differences between T and T* in CO binding were nevertheless sufficient to allow us to measure by flash photolysis the rate of the T*----T conformational change in terms of an allosteric model. The half-time for this transition was calculated to be 8-14 ms at 20 degrees C.

A multipass cuvette for laser photolysis studies and its uses in studying hemoglobin kinetics and equilibria.

A simple multipass cuvette was constructed by cementing small first-surface mirrors to opposite optical faces of a standard cuvette, eliminating the need for complex alignment devices. The multipass cuvette could then be positioned to provide optical path lengths of approximately 5 and 7 cm for the observing beam directed perpendicularly to the laser photolytic pulse. Internal reflection losses in the cuvette elevated the baseline by 0.36 in absorbance for the seven-pass alignment. Heme proteins can easily be studied at 100 nM in this cuvette. Analysis of the concentration dependence of the rapid recombination phase following photolysis of HbCO allows KTD to be determined. Precise determination of this constant, however, requires that a large range of concentrations be studied, allowing the fraction of rapid phase to vary from 20 to 80%. Human HbCO at pH 7 cannot be effectively studied over this concentration range in ordinary cuvettes owing to the low concentrations required. By employing the multipass cuvette, we have been able to make very precise determinations of this constant and find at pH 7, 21 degrees C, a value for KTD of 0.66 microM. We also determined that the quantum yield for photolysis of HbCO dimers and tetramers must be very nearly the same. For HbCO in Tris buffer, pH 7.4, the R----T conformation change is some six to seven times slower than that in phosphate. We have developed a simple equation that allows both the rate constant for the conformational change and the KTD to be determined under these conditions. The KTD obtained is in excellent agreement with a reported value obtained by large-zone gel filtration.

Is the continued use of ocular pneumoplethysmography necessary for the diagnosis of cerebrovascular disease?

The combination of duplex scanning and ocular pneumoplethysmography (OPG) has been used by many vascular laboratories for noninvasive evaluation of the carotid arteries. This study was undertaken to determine if OPG significantly improved the accuracy of duplex scanning alone. Three hundred eighty-five carotid arteries were studied in 190 patients with angiograms, duplex scans, or OPG. A total of 329 carotid arteries were examined with all three modalities. Three different criteria were used to interpret the OPG results, one each intended to deliver a high sensitivity, specificity, and overall accuracy. Depending on the criteria used, sensitivity of OPG alone for detecting hemodynamically significant (greater than 50%) stenosis ranged from 53% to 83%, with a specificity of 59% to 94%. Duplex scanning alone had a sensitivity of 87% and a specificity of 90% for similar lesions. If patients with only intracranial arterial stenosis were excluded, the sensitivity of the duplex scan rose to 91%. The addition of OPG to the duplex scan slightly increased sensitivity (range 91% to 95%; difference not significant) but significantly decreased specificity (range 56% to 84%; p less than 0.005). For detecting stenoses greater than 80%, the duplex scan alone had a sensitivity of 90% and a specificity of 88%. The addition of OPG to duplex scanning slightly increased sensitivity for these high-grade lesions but significantly decreased specificity (p less than 0.001) and overall accuracy. These results were unaffected by the presence or absence of intracranial disease. Because the addition of OPG to duplex scanning reduces specificity and accuracy without any significant increase in sensitivity, we no longer use it as part of our routine noninvasive cerebrovascular examination.

Are routine inferior vena cavograms necessary before Greenfield filter placement?

In August 1983 we began routinely studying the inferior vena cava (IVC) before placement of a Greenfield filter. We have performed 83 caval interruptions since that time, but six patients were excluded from this study because an IVC clip had been placed in three patients during other abdominal surgery, and the medical records of three others could not be retrieved. Of the remaining 77 patients, 65 (84%) had IVC venograms taken before placement of their filter. We personally reviewed 63 of these cavograms but had to accept the radiologist's reports for two studies that could not be retrieved. Ten (15%) cavograms showed abnormalities that significantly affected the placement of the filter. The most frequent abnormality was intracaval clot extending above the L3-4 interspace. Other important abnormalities were severe narrowing of the diaphragmatic IVC (two patients) and a tortuous IVC in a patient with severe scliosis. Seven (11%) additional cavograms showed unilateral iliac thrombus that would have influenced the surgical approach had a femoral approach been required. Formal preoperative cavography expedited filter placement and reduced operating time by obviating the need for intraoperative angiograms. Because 26% of the cavograms showed clinically important information, we recommend that routine IVC angiograms be taken before filter placement.

Use of autologous spiral vein grafts for vascular reconstructions in contaminated fields.

Vascular reconstructions in heavily contaminated fields can be particularly challenging. Prosthetic grafts are rarely suitable because of the risk of infection, but the saphenous vein is usually too small for isodiametric replacement of large arteries and veins. Although surgeons rarely consider the use of spiral vein grafts, they may occasionally be the ideal autogenous vascular replacement because they can be tailored to fit a vessel of any size. We report the use of spiral vein grafts in three patients requiring vascular reconstructions in the presence of heavy bacterial contamination.

Overaccommodation, underaccommodation, and the clinical phoropter: a study of instrument myopia and related effects.

To explore the degree to which a phoropter can induce overaccommodation (instrument myopia) and/or underaccommodation , 19 college-age subjects participated in a series of measurements of accommodation response. Accommodation responses were assessed while subjects looked through a phoropter (both with standard 19-mm viewing apertures and through 2-mm artificial pupils) and when no phoropter was present. Subjects were tested both monocularly and binocularly, and under three stimulus conditions (near target, far target, and total darkness). Even without the phoropter , subjects tended to overaccommodate for the far target. The 19-mm phoropter produced no significant overaccommodation or underaccommodation effects over and above those observed without the presence of the phoropter . The 2-mm artificial pupils produced significantly more underaccommodation for the near target. Results indicate a tendency for accommodation response to approach an intermediate resting position as the viewing situation becomes impoverished.

Use of a ready signal in accommodation assessment.

The usual procedure in making laser optometer measurements of accommodation is to precede each trial with a ready signal. Given previous findings that stress, arousal, attention, etc., can influence accommodation and related phenomena, the question arises as to whether such a ready signal might induce some form of orientation response reflected in alterations of accommodation. Dark focus (DF) accommodation (accommodation in total darkness) was assessed in 26 young adults (13 males and 13 females) under two conditions, one of which involved the use of a ready signal and the other did not. Analyses showed that the presence or absence of the ready signal had no differential impact on accommodation.