Toward successful migration to computerized physician order entry for chemotherapy

BACKGROUND

Computerized physician order entry (cpoe) systems allow for medical order management in a clinical setting. Use of a cpoe has been shown to significantly improve chemotherapy safety by reducing the number of prescribing errors. Usability of these systems has been identified as a critical factor in their successful adoption. However, there is a paucity of literature investigating the usability of cpoe for chemotherapy and describing the experiences of cancer care providers in implementing and using a cpoe system.

METHODS

A mixed-methods study, including a national survey and a workshop, was conducted to determine the current status of cpoe adoption in Canadian oncology institutions, to identify and prioritize knowledge gaps in cpoe usability and adoption, and to establish a research agenda to bridge those gaps. Survey respondents were representatives of cancer care providers from each Canadian province. The workshop participants were oncology clinicians, human factors engineers, patient safety researchers, policymakers, and hospital administrators from across Canada, with participation from the United States.

RESULTS

A variety of issues related to implementing and using a cpoe for chemotherapy were identified. The major issues concerned the need for better understanding of current practices of chemotherapy ordering, preparation, and administration; a lack of system selection and procurement guidance; a lack of implementation and maintenance guidance; poor cpoe usability and workflow support; and other cpoe system design issues. An additional three research themes for addressing the existing challenges and advancing successful adoption of cpoe for chemotherapy were identified: The need to investigate variances in workflows and practices in chemotherapy ordering and administrationThe need to develop best-practice cpoe procurement and implementation guidance specifically for chemotherapyThe need to measure the effects of cpoe implementation in medical oncology.

CONCLUSIONS

Addressing the existing challenges in cpoe usability and adoption for chemotherapy, and accelerating successful migration to cpoe by cancer care providers requires future research focusing on workflow variations, chemotherapy-specific cpoe procurement needs, and implementation guidance needs.

Thermal stability and DPPC/Ca2+ interactions of pulmonary surfactant SP-A from bulk-phase and monolayer IR spectroscopy

Surfactant protein A (SP-A), the most abundant pulmonary surfactant protein, is implicated in multiple biological functions including surfactant homeostasis, biophysical activity, and host defense. SP-A forms ternary complexes with lipids and Ca2+ which are important for protein function. The current study uses infrared (IR) transmission spectroscopy to investigate the bulk-phase interaction between SP-A, 1,2-dipalmitoylphosphatidylcholine (DPPC), and Ca2+ ions along with IR reflection-absorption spectroscopy (IRRAS) to examine protein secondary structure and lipid orientational order in monolayer films in situ at the air/water interface. The amide I contour of SP-A reveals two features at 1653 and 1636 cm(-1) arising from the collagen-like domain and a broad feature at 1645 cm(-1) suggested to arise from the carbohydrate recognition domain (CRD). SP-A secondary structure is unchanged in lipid monolayers. Thermal denaturation of SP-A in the presence of either DPPC or Ca2+ ion reveals a sequence of events involving the initial melting of the collagen-like region, followed by formation of intermolecular extended forms. Interestingly, these spectral changes were inhibited in the ternary system, showing that the combined presence of both DPPC and Ca2+ confers a remarkable thermal stability upon SP-A. The ternary interaction was revealed by the enhanced intensity of the asymmetric carboxylate stretching vibration. The IRRAS measurements indicated that incorporation of SP-A into preformed DPPC monolayers at a surface pressure of 10 mN/m induced a decrease in the average acyl chain tilt angle from 35 degrees to 28 degrees. In contrast, little change in chain tilt was observed at surface pressures of 25 or 40 mN/m. These results are consistent with and extend the fluorescence microscopy studies of Keough and co-workers [Ruano, M. L. F., et al. (1998) Biophys. J. 74, 1101-1109] in which SP-A was suggested to accumulate at the liquid-expanded/liquid-condensed boundary. Overall these experiments reveal the remarkable stability of SP-A in diverse, biologically relevant environments.

Bacteriorhodopsin thermal stability: influence of bound cations and lipids on the intrinsic protein fluorescence

Temperature-induced changes in protein intrinsic fluorescence of native, delipidated and deionized purple membranes are investigated. It is found that the removal of cations most strongly affects the protein and its thermal stability. The denaturation of dei-BR completes at 70 degrees C, while delipidated and native BR still maintain their native structure at this temperature. Both the quantum yield and the fluorescence maximum suggest correlation between the Trp-retinal coupling and protein structural stability. The low red shift of the fluorescence maximum caused by increasing of temperature indicates limited unfolding of bacteriorhodopsin upon denaturation.

Effect of calcium on phospholipid interaction with pulmonary surfactant protein C

Porcine pulmonary surfactant-associated protein SP-C was incorporated into bilayers of chain-perdeuterated dipalmitoylphosphatidylglycerol (DPPG-d62) and chain-perdeuterated dipalmitoyl-phosphatidylcholine (DPPC-d62) and into bilayers containing 70 mol% dipalmitoyl-phosphatidylcholine (DPPC) and 30 mol% DPPG-d62 or 70 mol% DPPC-d62 and 30 mol% dipalmitoylphosphatidylglycerol (DPPG). The effect of SP-C on the phase behavior, lipid chain order, and dynamics in these bilayers was examined by using deuterium nuclear magnetic resonance. SP-C was found to have a similar effect on the chain order and phase behavior of DPPC-d62 and DPPG-d62 in bilayers with a single lipid component. In gel phase DPPC/DPPG (7:3) bilayers with one or the other lipid component chain-perdeuterated, SP-C was found to affect first spectral moment more strongly for DPPG-d62 than for DPPC-d62. This may indicate that SP-C induced a nonrandom lateral distribution in the mixed lipid bilayer. SP-C was also found to influence motions responsible for deuteron transverse relaxation in both the gel and liquid crystalline phases. The presence of 5 mM Ca2+ in the aqueous phase substantially altered the effect of SP-C on transverse relaxation in the bilayer.

What NMR can tell us about where lung surfactant proteins live

2H-NMR is beginning to provide some insights into the way in which the hydrophobic surfactant proteins SP-B and SP-C interact with phospholipid bilayers in multilamellar structures. Both proteins have a significant effect on slow bilayer motions. In many ways, the effect of SP-C on the surrounding bilayer is similar to that of other transmembrane proteins. Ca2+ appears to modify the way in which SP-C perturbs the bilayers containing DPPG. The effect of SP-B on bilayers differs, in subtle ways, from that expected for a transmembrane protein.

Adsorption of pulmonary surfactant protein D to phospholipid monolayers at the air-water interface

The intrinsic surface activity of recombinant rat surfactant-associated protein D (SP-D) expressed in CHO-K1 cells has been determined from measurements of surface tension of its aqueous solutions. The interactions of recombinant SP-D with monolayers of phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylinositol (PI) spread at the air-water interface have been characterized. Injection of SP-D beneath preformed lipid monolayers at surface pressures less than 30 mN/m produced an increase in surface pressure, consistent with SP-D penetrating the lipid films. The adsorption of SP-D to the lipid monolayers did not display significant head group dependency, suggesting that the changes in surface pressure produced by the protein were likely due primarily to hydrophobic interactions with the lipid layers. In the presence of calcium ions in the subphase, SP-D displayed lower surface activity by itself and a reduced ability to generate surface pressure changes during adsorption to lipid monolayers compared to these properties of the protein in the absence of 2 mM Ca2+. Circular dichroism measurements on SP-D solutions with or without Ca2+ suggested that the cations altered the conformation of the protein and this possibly led to the calcium dependency of the surface activity of the protein in the presence or absence of lipid monolayers. Compressional isotherms of surface pressure versus area for SP-D/(DPPC-PI) and SP-D/(DPPC-PG) films formed by adsorption of the protein to preformed lipid monolayers were consistent with incorporation of some or all of the SP-D molecules into the lipid layers. The isotherms obtained on compression of the SP-D/lipid films to a maximum surface pressure of about 70 mN/m were consistent with the interpretation that any SP-D which was incorporated by adsorption was apparently not squeezed out, nor was lipid removed by the protein. The work suggests that when soluble recombinant SP-D is allowed to interact with phospholipid monolayers under the selected conditions of this experiment, it does so to a limited extent driven by primarily hydrophobic forces, and apparently without a high selectivity for phospholipid head groups.

Cholesterol modifies the properties of surface films of dipalmitoylphosphatidylcholine plus pulmonary surfactant-associated protein B or C spread or adsorbed at the air-water interface

Cholesterol is a substantial component of pulmonary surfactant (approximately 8 wt % or approximately 14 mol % of surfactant lipids). This study investigated the effect of cholesterol on the way in which hydrophobic SP-B and SP-C modulated the adsorption of lipid into the air-water interface and their respreading from collapsed phase produced on overcompression of the surface film. The properties of binary spread monolayers of SP-B or SP-C plus cholesterol (CH) were consistent with miscibility between the hydrophobic proteins and the sterol. Results from surface pressure versus area measurements at 23 degrees C on spread monolayers of dipalmitoylphosphatidylcholine (DPPC) plus SP-B in the presence of 8 wt % cholesterol implied that CH did not significantly affect the properties of the films of SP-B/(DPPC/CH) compared to those of binary SP-B/DPPC monolayers. In contrast, CH appeared to enhance the mixing of SP-C with DPPC/CH in ternary SP-C/(DPPC/CH) films compared to the miscibility of SP-C with DPPC in the SP-C/DPPC films. It is estimated that about 10 wt % SP-C might remain in the SP-C/(DPPC/CH) monolayers compressed to high surface pressures of about 72 mN/m, whereas SP-C at concentrations of > or = 5 wt % was squeezed out at pi approximately 50 mN/m from SP-C/DPPC films without cholesterol. Cholesterol reduced the stability of the films of SP-B/(DPPC/CH) and SP-C/(DPPC/CH) when they had been compressed to pi approximately 72 mN/m, in contrast to films of SP-B/DPPC and SP-C/DPPC which exhibited a relatively slow relaxation from the collapse pressure of 72 mN/m. Dynamic cyclic compression beyond collapse of SP-B/(DPPC/CH) and SP-C/(DPPC/CH) monolayers showed that cholesterol diminished their postcollapse respreading compared to the respreading of the protein/DPPC films without cholesterol. Cholesterol, at 8 wt %, inhibited the rate of adsorption to the air-water interface at 35 degrees C of aqueous dispersions of DPPC containing 2.5 or 5 wt % SP-B or SP-C. The results suggest that cholesterol has an apparent negative influence on the surfactant surface properties, which are generally considered to be important in surfactant function, although increasing protein concentrations can counteract some of the negative influences.

External reflection absorption infrared spectroscopy study of lung surfactant proteins SP-B and SP-C in phospholipid monolayers at the air/water interface

The interactions of the hydrophobic pulmonary surfactant proteins SP-B and SP-C with 1,2-dipalmitoylphosphatidylcholine in mixed, spread monolayer films have been studied in situ at the air/water interface with the technique of external reflection absorption infrared spectroscopy (IRRAS). SP-C has a mostly alpha-helical secondary structure both in the pure state and in the presence of lipids, whereas SP-B secondary structure is a mixture of alpha-helical and disordered forms. When films of SP-B/1,2-dipalmitoylphosphatidylcholine are compressed to surface pressures (pi) greater than approximately 40-43 mN/m, the protein is partially (15-35%) excluded from the surface, as measured by intensity ratios of the peptide bond amide l/lipid C==O stretching vibrations. The extent of exclusion increases as the protein/lipid ratio in the film increases. In contrast, SP-C either remains at the surface at high pressures or leaves accompanied by lipids. The amide l peak of SP-C becomes asymmetric as a result of the formation of intermolecular sheet structures (1615-1630 cm-1) suggestive of peptide aggregation. The power of the IRRAS experiment for determination of film composition and molecular structure, i.e., as a direct test of the squeeze-out hypothesis of pulmonary surfactant function, is evident from this work.

Pulmonary surfactant protein SP-A with phospholipids in spread monolayers at the air-water interface

Spread monolayers of pulmonary surfactant protein SP-A, alone or mixed with phospholipid(s), were formed at the air-water interface. Binary monolayers of SP-A plus dipalmitoylphosphatidylcholine (DPPC) showed positive deviations from ideal behavior of the mean areas in the films consistent with partial miscibility and interaction between the protein and lipid. During compression of SP-A/DPPC films which contained > or = 5 wt % SP-A, properties were displayed which were consistent with the protein being partially squeezed out at surface pressures of about 30 mN/m. Some protein appeared to remain in the monolayers even when they were compressed to high surface pressures of about 65-70 mN/m, and it was possibly included in the collapse phase(s) that was (were) formed at 72 mN/m. During dynamic cyclic compression-expansion of SP-A/DPPC monolayers initially formed at low surface pressures, SP-A enhanced the respreading of the films compressed beyond collapse compared to the respreading after collapse of films containing DPPC alone. Spread monolayers of SP-A plus either dipalmitoylphosphatidylglycerol (DPPG) or a mixture of DPPC plus DPPG (7:3, mol/mol) displayed additivity of the mean areas in the films, consistent with complete immiscibility (or ideal miscibility, an unlikely effect) between the protein and lipid components. Electrostatic repulsion between SP-A and DPPG, both negatively charged at physiological pH, possibly governed the behavior of these lipid-protein films. Calcium ions in the subphase did not alter the properties of SP-A/DPPC films, whereas they improved the ability of SP-A to mix with DPPG and DPPC/DPPG. Binding of calcium to the negatively charged DPPG and SP-A may account for association of the protein with DPPG and DPPC/DPPG in the monolayers in the presence of the divalent ions.

Early and delayed stages in the solubilization of purple membrane by a polyoxyethylenic surfactant

The purpose of this paper is to explore the reasons by which purple membrane solubilization by detergents takes hours, or even days, to reach equilibrium, while most biomembranes are solubilized in a matter of seconds, or minutes. With that aim, changes in the purple membrane absorption spectrum produced by hydrogenated Triton X-100 under equilibrium conditions (24 h) have been compared to those caused by the same surfactant in the minute, second and sub-second time scale. It is found that the various processes that accompany, or lead to, solubilization are already detected, and even reach an apparent equilibrium, in the 10 s that follow detergent addition. No new phenomena are detected in the following minutes, or hours, that are relevant to the process under study. This leads to the conclusion that the long solubilization process consists of the repeated operation of simple phenomena that are relatively fast in themselves. A hypothesis is proposed according to which the tight crystalline organization of the purple membrane prevents the insertion of detergent monomers in the lipid bilayer; instead, the surfactant would bind the periphery of the patches, i.e., the hydrocarbon-water contact region, and solubilization would take place gradually, from the periphery towards the core of the membrane patches, at a progressively lower rate as the amounts of free detergent and detergent-binding sites are decreased by the previous solubilization steps.

Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: II. Monolayers of pulmonary surfactant protein SP-C and phospholipids

The interaction of the hydrophobic pulmonary surfactant protein SP-C with dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) and DPPC:DPPG (7:3, mol:mol) in spread monolayers at the air-water interface has been studied. At low concentrations of SP-C (about 0.5 mol% or 3 weight%protein) the protein-lipid films collapsed at surface pressures of about 70 mN.m-1, comparable to those of the lipids alone. At initial protein concentrations higher than 0.8 mol%, or 4 weight%, the isotherms displayed kinks at surface pressures of about 50 mN.m-1 in addition to the collapse plateaux at the higher pressures. The presence of less than 6 mol%, or 27 weight%, of SP-C in the protein-lipid monolayers gave a positive deviation from ideal behavior of the mean areas in the films. Analyses of the mean areas in the protein-lipid films as functions of the monolayer composition and surface pressure showed that SP-C, associated with some phospholipid (about 8-10 lipid molecules per molecule of SP-C), was squeezed out from the monolayers at surface pressures of about 55 mN.m-1. The results suggest a potential role for SP-C to modify the composition of the monolayer at the air-water interface in the alveoli.

Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: III. Proteins SP-B plus SP-C with phospholipids in spread monolayers

Spread binary monolayers of surfactant-associated proteins SP-B and SP-C were formed at the air-water interface. Surface pressure measurements showed no interactions between the hydrophobic proteins. The effects of a mixture of SP-B plus SP-C (2:1, w/w) on the properties of monolayers of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), and DPPC:DPPG (7:3, mol:mol) were studied. During compression of ternary and quaternary films, containing less than 0.4 mol% or 5 weight% total protein, the proteins were not squeezed out and appeared to remain associated with the film until collapse at surface pressures of about 65-70 mN.m-1. At initial concentrations of total protein of about 0.9 mol% or 10 weight%, exclusion of protein-lipid complexes was observed at 40-50 mN.m-1. Larger amounts of phospholipid were removed by proteins from (SP-B:SP-C)/DPPG films than from (SP-B:SP-C)/DPPC ones. Separate squeeze-out of SP-B (or SP-B plus DPPC) at about 40 mN.m-1, followed by exclusion of SP-C (or SP-C plus DPPC) at about 50 mN.m-1, was observed in (SP-B:SP-C)/DPPC films. This led to a conclusion that there was independent behavior of SP-B and SP-C in (SP-B:SP-C)/DPPC monolayers. The quaternary (SP-B:SP-C)/(DPPC:DPPG) films showed qualitatively similar process of squeeze-out of the proteins. In the ternary mixtures of SP-B plus SP-C with DPPG separate exclusion of SP-B was not detected; rather, the data was consistent with exclusion of a (SP-B:SP-C)/DPPG complex at about 50 mN.m-1. The results imply possible interactions between SP-B and SP-C and the acidic phospholipid.

Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: I. Monolayers of pulmonary surfactant protein SP-B and phospholipids

The effects of pulmonary surfactant protein SP-B on the properties of monolayers of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG), and a mixture of DPPC:DPPG (7:3, mol:mol) were studied using spread films at the air-water interface. The addition of SP-B to the phospholipid monolayers gave positive deviations from additivity of the mean areas in the films. At low protein concentrations (less than 45% amino acid residues which corresponds to 0.5 mol% or 10 weight% SP-B) monolayers of SP-B/DPPC, SP-B/DPPG and SP-B/(DPPC:DPPG) collapsed at surface pressures of about 70 mN.m-1, comparable to those of the lipids alone. At higher concentrations of SP-B in the protein-lipid monolayers, kink points appeared in the isotherms at about 40-45 mN.m-1, implying possible exclusion of material from the films, hence, changes in the original monolayer compositions. Calculated analyses of the monolayer compositions as a function of surface pressure indicated that nearly pure SP-B, associated with small amounts of phospholipid (2-3 lipid molecules per SP-B dimer), was lost from SP-B/DPPC, SP-B/DPPG, and SP-B/(DPPC:DPPG) films at surface pressures higher than 40-45 mN.m-1. The results are consistent with a low effectiveness of SP-B in removing saturated phospholipids, DPPC or DPPG, from the spread SP-B/phospholipid films.

2H NMR studies of the effect of pulmonary surfactant SP-C on the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine headgroup: a model for transbilayer peptides in surfactant and biological membranes

Surfactant protein C (SP-C) was isolated from solvent extracts of porcine pulmonary surfactant by gel filtration chromatography. The surfactant protein was combined with dipalmitoylphosphatidylcholine deuterated at the alpha and beta positions of the choline headgroup (DPPC-d4) Deuterium nuclear magnetic resonance spectra were collected as a function of temperature for a series of protein concentrations. The splitting of the alpha-deuteron spectrum in the liquid-crystalline phase was insensitive to temperature but decreased with increasing protein concentration. The response of headgroup conformation to protein concentration was consistent with an interaction between the lipid headgroup dipole and the net positive surface charge associated with the protein. The observed effect per charge on the alpha splitting was less than that reported for singly-charged amphiphiles [Scherer, P. G., & Seelig, J. (1989) Biochemistry 28, 7720-7728] but was similar to that obtained using a multipled-charged amphiphilic polypeptide [Roux, M., Neumann, J.-M., Hodges, R. S., Devaux, P. F., & Bloom, M. (1989) Biochemistry 28, 2313-2321]. This comparison suggests that the charges on SP-C are located near the bilayer surface. The possibility that the headgroup response is sensitive to the degree of clustering of surface charge is discussed. The beta-deuteron splitting in the liquid-crystalline phase decreased with increasing temperature but was relatively insensitive to protein concentration, suggesting that the torsion angle about the C alpha-C beta bond might be sensitive to steric interactions between the lipid headgroup and the protein.

Pulmonary surfactant protein SP-C causes packing rearrangements of dipalmitoylphosphatidylcholine in spread monolayers

The hydrophobic pulmonary surfactant protein SP-C has been isolated from porcine lung surfactant, and it has been incorporated into monolayers of dipalmitoylphosphatidylcholine (DPPC). The monolayers, which contained 1 mol% of a fluorescently-labeled phosphatidylcholine, were observed under various states of compression in an epifluorescence surface balance. SP-C altered the packing arrangements of DPPC in the monolayer, causing the production of many more, smaller condensed lipid domains in its presence than in its absence.