The analysis of 51 genes in DSM-IV combined type attention deficit hyperactivity disorder: association signals in DRD4, DAT1 and 16 other genes

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder, starting in early childhood and persisting into adulthood in the majority of cases. Family and twin studies have demonstrated the importance of genetic factors and candidate gene association studies have identified several loci that exert small but significant effects on ADHD. To provide further clarification of reported associations and identify novel associated genes, we examined 1,038 single-nucleotide polymorphisms (SNPs) spanning 51 candidate genes involved in the regulation of neurotransmitter pathways, particularly dopamine, norepinephrine and serotonin pathways, in addition to circadian rhythm genes. Analysis used within family tests of association in a sample of 776 DSM-IV ADHD combined type cases ascertained for the International Multi-centre ADHD Gene project. We found nominal significance with one or more SNPs in 18 genes, including the two most replicated findings in the literature: DRD4 and DAT1. Gene-wide tests, adjusted for the number of SNPs analysed in each gene, identified associations with TPH2, ARRB2, SYP, DAT1, ADRB2, HES1, MAOA and PNMT. Further studies will be needed to confirm or refute the observed associations and their generalisability to other samples.

Beneficial effects of leukocyte depletion of transfused blood on postoperative complications in patients undergoing cardiac surgery: a randomized clinical trial

BACKGROUND

Leukocytes in transfused blood are associated with several posttransfusion immunomodulatory effects. Although leukocytes play an important role in reperfusion injury, the contribution of leukocytes in transfused blood products has not been investigated. To estimate the role and the timing of leukocyte filtration of red cells in cardiac surgery, we performed a randomized study.

METHODS AND RESULTS

Patients scheduled for cardiac surgery were randomly allocated to receive either packed cells without buffy coat (PC, n = 306), fresh-filtered units (FF, n = 305), or stored-filtered units (SF, n = 303) when transfusion was indicated. We evaluated the periods of hospitalization and stay at the intensive care unit, and the occurrences of postoperative complications up to 60 days after surgery. The average hospital stay was 10.7 days, of which 3.2 days were in the intensive care unit, without significant differences between the groups. In the PC trial arm, 23.0% of the patients had infections versus 16.9% and 17.9% of the patients in the leukocyte-depleted trial arms (P=.13). Within 60 days, 45 patients had died, 24 patients in the PC trial arm (7.8%), versus 11 (3.6%) and 10 (3.3%) patients in the FF and SF trial arms, respectively (P=.015).

CONCLUSIONS

In cardiac surgery patients, especially when more than three blood transfusions are required, leukocyte depletion by filtration results in a significant reduction of the postoperative mortality that can only partially be explained by the higher incidence of postoperative infections in the PC group.

The genetic background to PTSD

Although extensive research has already been done on the genetic bases of psychiatric disorders, little is known about polygenetic influences in posttraumatic stress disorder (PTSD). This article reviews molecular genetic studies relating to PTSD that were found in a literature search in Medline, Embase and Web of Science. Association studies have investigated 8 major genotypes in connection with PTSD. They have tested hypotheses involving key candidate genes in the serotonin (5-HTT), dopamine (DRD2, DAT), glucocorticoid (GR), GABA (GABRB), apolipoprotein systems (APOE2), brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY). The studies have produced inconsistent results, many of which may be attributable to methodological shortcomings and insufficient statistical power. The complex aetiology of PTSD, for which experiencing a traumatic event forms a necessary condition, makes it difficult to identify specific genes that substantially contribute to the disorder. Gene-finding strategies are difficult to apply. Interactions between different genes and between them and the environment probably make certain people vulnerable to developing PTSD. Gene-environmental studies are needed that focus more narrowly on specific, distinct endophenotypes and on influences from environmental factors.

Patient safety: latent risk factors

The person-centred analysis and prevention approach has long dominated proposals to improve patient safety in healthcare. In this approach, the focus is on the individual responsible for making an error. An alternative is the systems-centred approach, in which attention is paid to the organizational factors that create precursors for individual errors. This approach assumes that since humans are fallible, systems must be designed to prevent humans from making errors or to be tolerant to those errors. The questions raised by this approach might, for example, include asking why an individual had specific gaps in their knowledge, experience, or ability. The systems approach focuses on working conditions rather than on errors of individuals, as the likelihood of specific errors increases with unfavourable conditions. Since the factors that promote errors are not directly visible in the working environment, they are described as latent risk factors (LRFs). Safety failures in anaesthesia, in particular, and medicine, in general, result from multiple unfavourable LRFs, so we propose that effective interventions require that attention is paid to interactions between multiple factors and actors. Understanding how LRFs affect safety can enable us to design more effective control measures that will impact significantly on both individual performance and patient outcomes.

The reliability of plain radiography in experimental fracture healing

OBJECTIVE

To investigate the reliability of radiographs in the evaluation of healing of closed fractures.

DESIGN

A closed midshaft tibial fracture was created in 40 goats and stabilized with an external fixator. The animals were assigned to four groups: no injection, injection of 1 mg osteogenic protein-1 (OP-1), 1 mg OP-1 with collagenous carrier, or carrier alone. Radiographs were performed weekly until the animals were killed after 2 and 4 weeks. Healing was evaluated using radiographs, biomechanical testing, and histological examination. All radiographs were examined by two independent observers. Interobserver agreement was calculated and radiographic scores were compared with mechanical and histological scores using regression analysis.

RESULTS

Regression analysis showed poor correlation between radiographic scores and biomechanical and histological data. Correlation coefficients varied between 0.39 and 0.63. Good agreement between the observers was seen in only three parameters: visibility of the fracture line, weightbearing ability, and a combined healing parameter.

CONCLUSION

Plain radiography provides poor parameters for monitoring the fracture healing process.

New segmental long bone defect model in sheep: quantitative analysis of healing with dual energy x-ray absorptiometry

An appropriate animal model is required for the study of treatments that enhance bone healing. A new segmental long bone defect model was developed for this purpose, and dual energy x-ray absorptiometry was used to quantify healing of this bone defect. In 15 sheep, a 3-cm segmental defect was created in the left tibia and fixed with an interlocking intramedullary nail. In seven animals, the defect was left empty for the assessment of the spontaneous healing response. In eight animals serving as a positive control, autologous bone grafting was performed. After 12 weeks, healing was evaluated with radiographs, a torsional test to failure, and dual energy x-ray absorptiometry. The mechanical test results were used for the assessment of unions and nonunions. Radiographic determination of nonunion was not reliably accomplished in this model. By means of dual energy x-ray absorptiometry, bone mineral density and content were measured in the middle of the defect. Bone mineral density was 91+/-7% (mean +/- SEM) and 72+/-6% that of the contralateral intact tibia in, respectively, the autologous bone-grafting and empty defect groups (p = 0.04). For bone mineral content, the values were, respectively, 117+/-18 and 82+/-9% (p = 0.07). Torsional strength and stiffness were also higher, although not significantly, in the group with autologous bone grafting than in that with the empty defect. Bone mineral density and content were closely related to the torsional properties (r2 ranged from 0.76 to 0.85, p < or = 0.0001). Because interlocking intramedullary nailing is a very common fixation method in patients, the newly developed segmental defect model has clinical relevance. The interlocking intramedullary nail provided adequate stability without implant failure. This model may be useful for the study of treatments that affect bone healing, and dual energy x-ray absorptiometry may be somewhat helpful in the analysis of healing of this bone defect.

A high-density SNP linkage scan with 142 combined subtype ADHD sib pairs identifies linkage regions on chromosomes 9 and 16

As part of the International Multi-centre ADHD Genetics project we completed an affected sibling pair study of 142 narrowly defined Diagnostic and Statistical Manual of Mental Disorders, fourth edition combined type attention deficit hyperactivity disorder (ADHD) proband-sibling pairs. No linkage was observed on the most established ADHD-linked genomic regions of 5p and 17p. We found suggestive linkage signals on chromosomes 9 and 16, respectively, with the highest multipoint nonparametric linkage signal on chromosome 16q23 at 99 cM (log of the odds, LOD=3.1) overlapping data published from the previous UCLA (University of California, Los Angeles) (LOD>1, approximately 95 cM) and Dutch (LOD>1, approximately 100 cM) studies. The second highest peak in this study was on chromosome 9q22 at 90 cM (LOD=2.13); both the previous UCLA and German studies also found some evidence of linkage at almost the same location (UCLA LOD=1.45 at 93 cM; German LOD=0.68 at 100 cM). The overlap of these two main peaks with previous findings suggests that loci linked to ADHD may lie within these regions. Meta-analysis or reanalysis of the raw data of all the available ADHD linkage scan data may help to clarify whether these represent true linked loci.

The factor structure of the Buss and Plomin EAS Temperament Survey (parental ratings) in a Dutch sample of elementary school children

The psychometric properties of the Buss and Plomin (1984) EAS Temperament Survey for Children (Parental Ratings) were examined in a sample of Dutch children between 4 and 13 years of age. Ratings were obtained from 230 mothers and 172 fathers. The findings presented here provide the lacking cross-validation of the original analyses by Rowe and Plomin (1977): Emotionality, activity, and shyness were independent temperaments, regardless of age and gender. The factorial position of the yet experimental Sociability scale is more ambiguous: Sociability was significantly related to both shyness and activity but was more strongly associated with shyness in the youngest age cohort and most strongly with activity in the oldest cohort. This age trend, combined with a positive association with activity, supports the premise that sociability cannot be equated to nonshyness and justifies the inclusion of a separate Sociability scale in the EAS. All four EAS scales are reliable in terms of internal consistency and interrater agreement, but one modification of the Sociability scale is needed.

Quantification of fracture healing with three-dimensional computed tomography

Quantitative methods are necessary for an objective evaluation of fracture healing. Three-dimensional computed tomography (CT) for the measurement of callus volume and density could be such a method and was investigated in an animal model. In 23 goats a closed tibial fracture was created and stabilized with a cast. The animals were killed at 2, 4 and 6 weeks for radiographical, CT and biomechanical analysis. From the CT scans a three-dimensional reconstruction of the callus was made to measure its volume and mean density. At 2 weeks the callus volume had already reached its maximum. In contrast, callus density, torsional strength and torsional stiffness increased over time (P < 0.0001, analysis of variance, ANOVA). Multiple regression analysis showed that the callus volume was not related to the torsional properties. However, callus density was a significant explanatory variable for both torsional strength (R2 = 0.72, P < 0.0001) and torsional stiffness (R2 = 0.82, P < 0.0001). Therefore, callus density as measured by three-dimensional CT is a predictor of the extent of fracture consolidation. CT with three-dimensional reconstruction of the callus seems a valid technique for the quantification of fracture healing.

Enhancement of Exopolysaccharide Production by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 with a Simplified Defined Medium

The aim of this work was to investigate the medium requirements for growth and production of exopolysaccharides by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772. The strain was grown in batch cultures on a chemically defined medium, and the technique of single omission of medium components was applied to determine the nutritional requirements. The omission of aspartic acid, glutamic acid, or glycine affected growth only slightly, and the omission of glutamine, asparagine, or threonine resulted in a stronger reduction of the growth. All the other amino acids were essential. Multiple omissions of amino acids caused an almost complete loss of growth. L. delbrueckii subsp. bulgaricus required only riboflavin, calcium pantothenate, and nicotinic acid as individual vitamins. Surprisingly, when only these vitamins were present in the medium and other vitamins were not, less growth was observed than in the complete medium but the amount of exopolysaccharide produced was significantly greater. These observations were studied in more detail with a simplified defined medium in which L. delbrueckii subsp. bulgaricus was able to grow and produce exopolysaccharides. Although the final optical density in the simplified medium was lower, the production of exopolysaccharides was about twofold higher than in the complete medium.

Vandenbroucke-Grauls CMJ, Wilschut JA, van Egmond M, C. Stockmann HBA, van der Bij GJ, de Korte N, Oosterling SJ, Acherman YIZ, den Boer FC, Sonneveld DJA, Poort L. Randomized clinical trial of selective decontamination of the digestive tract in elective colorectal cancer surgery (SELECT trial)

Background

Infectious complications and anastomotic leakage affect approximately 30 per cent of patients after colorectal cancer surgery. The aim of this multicentre randomized trial was to investigate whether selective decontamination of the digestive tract (SDD) reduces these complications of elective colorectal cancer surgery.

Methods

The effectiveness of SDD was evaluated in a multicentre, open-label RCT in six centres in the Netherlands. Patients with colorectal cancer scheduled for elective curative surgery with a primary anastomosis were eligible. Oral colistin, tobramycin and amphotericin B were administered to patients in the SDD group to decontaminate the digestive tract. Both treatment and control group received intravenous cefazolin and metronidazole for perioperative prophylaxis. Mechanical bowel preparation was given for left-sided colectomies, sigmoid and anterior resections. Anastomotic leakage was the primary outcome; infectious complications and mortality were secondary outcomes.

Results

The outcomes for 228 patients randomized to the SDD group and 227 randomized to the control group were analysed. The trial was stopped after interim analysis demonstrated that superiority was no longer attainable. Effective SDD was confirmed by interspace DNA profiling analysis of rectal swabs. Anastomotic leakage was observed in 14 patients (6·1 per cent) in the SDD group and in 22 patients (9·7 per cent) in the control group (odds ratio (OR) 0·61, 95 per cent c.i. 0·30 to 1·22). Fewer patients in the SDD group had one or more infectious complications than patients in the control group (14·9 versus 26·9 per cent respectively; OR 0·48, 0·30 to 0·76). Multivariable analysis indicated that SDD reduced the rate of infectious complications (OR 0·47, 0·29 to 0·76).

Conclusion

SDD reduces infectious complications after colorectal cancer resection but did not significantly reduce anastomotic leakage in this trial. Registration number: NCT01740947 (https://www.clinicaltrials.gov).

Biomechanical and histological aspects of fracture healing, stimulated with osteogenic protein-1

Fracture healing could be stimulated with osteoinductive bone morphogenetic proteins (bmp's), such as osteogenic protein-1 (OP-1), but little is known about its effectiveness in stimulation of fracture healing. In this study, biomechanical and histological aspects of fracture healing after an injection of OP-1 in the fracture gap were investigated. In 40 goats, a closed fracture was created in the left tibia. The fractures were stabilized with an external fixator and the animals were assigned to four different groups: no injection, injection of 1 mg OP-1, injection of 1 mg OP-1 with collagenous carrier material, and injection of carrier material alone. Twenty-one animals were sacrificed after 2 weeks and 19 after 4 weeks. Biomechanical testing was perfomed on both explanted tibiae. Four longitudinal samples of the fracture were sawn, processed for histology, and examined by two observers. Biomechanical evaluation showed a higher stiffness and strength at 2 weeks after injection of OP-1. Histological evaluation showed normal fracture healing patterns in all animals without adverse effects of the given injections. These data show that fracture healing can be accelerated with a single injection of OP-1, eventually resulting in normally healed bone.

Effect of recombinant human osteogenic protein-1 on the healing of a freshly closed diaphyseal fracture

Osteogenic protein-1 (OP-1), or bone morphogenetic protein-7, is an osteoinductive morphogen that is involved in embryonic skeletogenesis and in bone repair. In bone defect models without spontaneous healing, local administration of recombinant human OP-1 (rhOP-1) induces complete healing. To investigate the ability of rhOP-1 to accelerate normal physiologic fracture healing, an experimental study was performed. In 40 adult female goats a closed tibial fracture was made, stabilized with an external fixator, and treated as follows: (1) no injection; (2) injection of 1 mg rhOP-1 dissolved in aqueous buffer; (3) injection of collagen matrix; and (4) injection of 1 mg rhOP-1 bound to collagen matrix. The test substances were injected in the fracture gap under fluoroscopic control. At 2 and 4 weeks, fracture healing was evaluated with radiographs, three-dimensional computed tomography (CT), dual-energy X-ray absorptiometry, biomechanical tests, and histology. At 2 weeks, callus diameter, callus volume, and bone mineral content at the fracture site were significantly increased in both rhOP-1 groups compared with the no-injection group. As signs of accelerated callus maturation, bending and torsional stiffness were higher and bony bridging of the fracture gap was observed more often in the group with rhOP-1 dissolved in aqueous buffer than in uninjected fractures. Treatment with rhOP-1 plus collagen matrix did not result in improved biomechanical properties or bony bridging of the fracture gap at 2 weeks. At 4 weeks there were no differences between groups, except for a larger callus volume in the rhOP-1 plus collagen matrix group compared with the control groups. All fractures showed an advanced stage of healing at 4 weeks. In conclusion, the healing of a closed fracture in a goat model can be accelerated by a single local administration of rhOP-1. The use of a carrier material does not seem to be crucial in this application of rhOP-1.

First-pass lung uptake and pulmonary clearance of propofol: assessment with a recirculatory indocyanine green pharmacokinetic model

BACKGROUND

The principal site for elimination of propofol is the liver. The clearance of propofol exceeds hepatic blood flow; therefore, extrahepatic clearance is thought to contribute to its elimination. This study examined the pulmonary kinetics of propofol using part of an indocyanine green (ICG) recirculatory model.

METHODS

Ten sheep, immobilized in a hammock, received injections of propofol (4 mg/kg) and ICG (25 mg) via two semipermanent catheters in the right internal jugular vein. Arterial blood samples were obtained from the carotid artery. The ICG injection was given for measurement of intravascular recirculatory parameters and determination of differences in propofol and ICG concentration-time profiles. No other medication was given during the experiment, and the sheep were not intubated. The arterial concentration-time curves of ICG were analyzed with a recirculatory model. The pulmonary uptake and elimination of propofol was analyzed with the central part of that model extended with a pulmonary tissue compartment allowing elimination from that compartment.

RESULTS

During the experiment, cardiac output was 3.90+/-0.72 l/min (mean +/- SD). The blood volume in heart and lungs, measured with ICG, was 0.66+/-0.07 l. A pulmonary tissue compartment of 0.47+/-0.16 l was found for propofol. The pulmonary first-pass elimination of propofol was 1.14+/-0.23 l/min. Thirty percent of the dose was eliminated during the first pass through the lungs.

CONCLUSIONS

Recirculatory modeling of ICG allows modeling of the first-pass pulmonary kinetics of propofol concurrently. Propofol undergoes extensive uptake and first-pass elimination in the lungs.

Recirculatory pharmacokinetics and pharmacodynamics of rocuronium in patients: the influence of cardiac output

BACKGROUND

Recirculatory models are capable of accurately describing first-pass pharmacokinetics and the influence of cardiac output (CO), which is important for drugs with a fast onset of effect. The influence of CO on pharmacokinetic and pharmacodynamic parameters of rocuronium in patients was evaluated using a recirculatory pharmacokinetic model.

METHODS

Fifteen patients were included to study rocuronium pharmacokinetics and pharmacodynamics. Bolus doses of rocuronium (0.35 mg/kg) and indocyanine green (25 mg) were injected simultaneously via a peripheral intravenous catheter. Blood samples were taken for 240 min from the radial artery. The force of contraction of the adductor pollicis after a train-of-four at 2 Hz every 12 s was measured. Arterial concentration-time curves of rocuronium and indocyanine green were analyzed using a recirculatory model. Pharmacodynamics were described using a sigmoid maximum effect (Emax) model.

RESULTS

The CO of the patients varied from 2.43 to 5.59 l/min. Total distribution volume of rocuronium was 17.3 +/- 4.8 l (mean +/- SD). The CO showed a correlation with the fast tissue clearance (Cl(T_f); r2 = 0.51), with the slow tissue clearance (Cl(T_s); r2 = 0.31) and with the mean transit times of rocuronium except for the mean transit time of the slow tissue compartment. The blood-effect site equilibration constant (k(e0)) was strongly correlated with CO (r2 = 0.70).

CONCLUSIONS

Cardiac output influences the pharmacokinetics, including k(e0), for rocuronium in patients. For drugs with a fast onset of effect, a recirculatory model, which includes CO, can give a good description of the relation between concentration and effect, in contrast to a conventional compartmental pharmacokinetic model.

Effect of propofol on peripheral vascular resistance during cardiopulmonary bypass

Twenty-eight patients undergoing elective coronary artery bypass surgery were allocated randomly to receive either propofol 2 mg kg-1 or an equivalent volume of its vehicle during cardiopulmonary bypass with constant pump flow. Peripheral vascular resistance (PVR) was calculated from perfusion pressure and pump flow. After propofol, PVR decreased from 1767 (SD 415) dyn s cm-5 to a minimum of 1263 (283) dyn s cm-5 at 2 min, and remained significantly less than the control value until 12.5 min after administration of propofol. In the group given the vehicle, PVR did not change significantly. In a second study in 10 patients, venous blood samples were withdrawn before and 2, 4, 6, 8, 10, 20 and 30 min after injection of propofol 2 mg kg-1 during cardiopulmonary bypass, for measurement of blood concentrations of propofol. Concentrations were greater than predicted by a computer simulation based on published pharmacokinetic data. The decrease in PVR may be an important factor in the hypotension caused by propofol during induction of anaesthesia.

Resorbable calcium phosphate particles as a carrier material for bone marrow in an ovine segmental defect

Resorbable calcium phosphate ceramics are only osteoconductive; therefore, their combination with osteogenic substances may lead to stimulation of bone healing. In the present study this combination, using autologous bone marrow, was investigated. In 31 sheep, a 3-cm tibial segmental defect was created and stabilized with an intramedullary nail. The animals were divided into four groups: empty defects (group 1, n = 7), and defects filled with 10-mL dense resorbable calcium phosphate particles (group 2, n = 8), with 10-mL particles soaked in bone marrow (group 3, n = 8), or with 10-mL autologous bone (group 4, n = 8). On evaluation after 12 weeks, significantly higher values were seen in group 3 than in group 2 for callus volume (p = .016), bone mineral density ratio (p = .03), bone mineral content ratio (p = .04), torsional strength (p = .005), and torsional stiffness (p = .01). For all end points, the outcome of group 3 was lower than that of group 4. In the histology, there was direct contact between newly formed bone and remnants of the particles. There were no signs of inflammatory reactions. Although a stimulatory effect of bone marrow was seen, the combination of resorbable calcium phosphate particles with bone marrow does not provide an alternative for autologous bone grafting.

Assessing system failures in operating rooms and intensive care units

BACKGROUND

The current awareness of the potential safety risks in healthcare environments has led to the development of largely reactive methods of systems analysis. Proactive methods are able to objectively detect structural shortcomings before mishaps and have been widely used in other high-risk industries.

METHODS

The Leiden Operating Theatre and Intensive Care Safety (LOTICS) scale was developed and evaluated with respect to factor structure and reliability of the scales. The survey was administered to the staff of operating rooms at two university hospitals, and intensive care units (ICUs) of one university hospital and one teaching hospital. The response rate varied between 40-47%. Data of 330 questionnaires were analysed. Safety aspects between the different groups were compared.

RESULTS

Factor analyses and tests for reliability resulted in nine subscales. To these scales another two were added making a total of 11. The reliability of the scales varied from 0.75 to 0.88. The results clearly showed differences between units (OR1, OR2, ICU1, ICU2) and staff.

CONCLUSION

The results seem to justify the conclusion that the LOTICS scale can be used in both the operating room and ICU to gain insight into the system failures, in a relatively quick and reliable manner. Furthermore the LOTICS scale can be used to compare organisations to each other, monitor changes in patient safety, as well as monitor the effectiveness of the changes made to improve the level of patient safety.

Effect of thiopentone, etomidate and propofol on systemic vascular resistance during cardiopulmonary bypass

We have studied the effect of thiopentone, etomidate and propofol on systemic vascular resistance (SVR) during cardiopulmonary bypass with constant pump flow in 30 patients undergoing elective coronary artery bypass surgery. SVR decreased to 78% of control values after thiopentone 4 mg kg-1, to 72% of control after etomidate 0.3 mg kg-1, and to 68% of control after propofol 2 mg kg-1; it returned to control values 10 min after administration of thiopentone and propofol and 7 min after administration of etomidate. Analysis of variance showed that there were no significant differences in the changes in SVR between the groups.

Evaluation of strength of healing fractures with dual energy Xray absorptiometry

Dual energy xray absorptiometry was investigated as a method for evaluation of the strength of closed tibial fractures. In 40 goats, a closed midshaft fracture was created in the left tibia. The fractures were stabilized with an external fixator. After 2 weeks (n = 21) and after 4 weeks (n = 19), both tibias were explanted and, using dual energy xray absorptiometry, bone mineral density and bone mineral content were measured in a 1 cm region. With nondestructive bending tests, area ratio and stiffness index were determined and torsional strength and torsional stiffness were determined with a torsional test to failure. Linear regression analysis was used to calculate the squared correlation coefficients for the relations between dual energy xray absorptiometry and the outcome of the mechanical tests. The squared correlation coefficients for the relation between bone mineral density and torsional strength, torsional stiffness, and area ratio and stiffness index were 0.72, 0.76, 0.64, and 0.72, respectively. The squared correlation coefficients for the relation between bone mineral content and these mechanical parameters were 0.72, 0.77, 0.63, and 0.77, respectively. The results using dual energy xray absorptiometry indicate the strength of healing closed fractures. Additional research is required to investigate specific aspects of this technique.

Recirculatory and compartmental pharmacokinetic modeling of alfentanil in pigs: the influence of cardiac output

BACKGROUND

Cardiac output (CO) is likely to influence the pharmacokinetics of anesthetic drugs and should be accounted for in pharmacokinetic models. The influence of CO on the pharmacokinetic parameters of alfentanil in pigs was evaluated using compartmental and recirculatory models.

METHODS

Twenty-four premedicated pigs were evaluated during halothane (0.6-2%) anesthesia. They were assigned randomly to one of three groups. One group served as control. In the other groups, the baseline CO was decreased or increased by 40% by pharmacologic intervention (propranolol or dobutamine). Boluses of alfentanil (2 mg) and indocyanine green (25 mg) were injected into the right atrium. Blood samples were taken for 150 min from the right atrium and aortic root. Arterial concentration-time curves of indocyanine green and alfentanil were analyzed using compartmental models (two-stage and mixed-effects approach) and a recirculatory model, which can describe lung uptake and early distribution.

RESULTS

The CO of individual pigs varied from 1.33 to 6.44 l/min. Three-compartmental modeling showed that CO is a determinant of the central compartment volume (V1, r2 = 0.54), fast peripheral compartment volume (V2, r2 = 0.29), steady state distribution volume (Vss, r2 = 0.29), fast distribution clearance (Cl12, r2 = 0.39), and elimination clearance (Cl10, r2 = 0.51). Recirculatory modeling showed that CO is a determinant of total distribution volume (r2 = 0.48), elimination clearance (r2 = 0.54), and some distribution clearances. The pulmonary distribution volume was independent of CO.

CONCLUSIONS

Cardiac output markedly influences the pharmacokinetics of alfentanil in pigs. Therefore, accounting for CO enhances the predictive value of pharmacokinetic models of alfentanil.

Uptake of sufentanil, alfentanil and morphine in the lungs of patients about to undergo coronary artery surgery

We have studied the pulmonary extraction and retention of sufentanil, alfentanil and morphine using a double indicator technique in 30 patients undergoing elective aortocoronary bypass surgery. Patients were allocated to three groups (10 each) to receive sufentanil 43 micrograms, alfentanil 672 micrograms or morphine 1887 micrograms, mixed with indocyanine green as indicator. After sufentanil, mean peak extraction was 93.7% (95% confidence interval 87.1-100.4%) and release occurred after 16.1 (13.8-18.4) s; first-pass retention was 61.1 (51.3-70.9)%. After alfentanil, peak extraction was 67.4 (42.7-92.0)% and release occurred after 9.9 (8.5-11.3) s; first-pass retention was 10.1 (3.5-16.7)%. After morphine, peak extraction was 58.3 (44.4-72.2)% and release occurred after 7.2 (4.4-10.1) s; first-pass retention was 7.1 (-4.7-19.9)%. Both peak extraction and first-pass retention were significantly greater after sufentanil. There was no significant difference in the peak extraction and first-pass retention between alfentanil and morphine.

Siblings in foster care: success and failure

This article reports on a retrospective study of 59 joint placements of siblings in foster homes, involving a total of 137 children. An overall picture is presented of the agencies' considerations in making these placements. The number of prematurely terminated placements in this group amounted to 14 (23.7%). Several factors that appear related to premature termination are discussed.