Quantum phase slips: from condensed matter to ultracold quantum gases.

Quantum phase slips (QPS) are the primary excitations in one-dimensional superfluids and superconductors at low temperatures. They have been well characterized in most condensed-matter systems, and signatures of their existence have been recently observed in superfluids based on quantum gases too. In this review, we briefly summarize the main results obtained on the investigation of phase slips from superconductors to quantum gases. In particular, we focus our attention on recent experimental results of the dissipation in one-dimensional Bose superfluids flowing along a shallow periodic potential, which show signatures of QPS.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

Modeling the transport of interacting matter waves in a disordered system by a nonlinear diffusion equation.

We model the expansion of an interacting atomic Bose-Einstein condensate in a disordered lattice with a nonlinear diffusion equation normally used for a variety of classical systems. We find approximate solutions of the diffusion equation that well reproduce the experimental observations for both short and asymptotic expansion times. Our study establishes a connection between the peculiar shape of the expanding density profiles and the microscopic nonlinear diffusion coefficients.

Magnetic dipolar interaction in a Bose-Einstein condensate atomic interferometer.

We study the role played by the magnetic dipole interaction in the decoherence of a lattice-based interferometer that employs an alkali Bose-Einstein condensate with a tunable scattering length. The different behavior we observe for two different orientations of the dipoles gives us evidence of the anisotropic character of the interaction. The experiment is correctly reproduced by a model we develop only if the long-range interaction between different lattice sites is taken into account. Our model indicates that dipolar interaction can be compensated by a proper choice of the scattering length and that the magnetic dipole interaction should not represent an obstacle for atom interferometry with Bose-Einstein condensates with a tunable interaction.

Atom interferometry with a weakly interacting Bose-Einstein condensate.

We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a 39K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a_(0) and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry.

39K Bose-Einstein condensate with tunable interactions.

We produce a Bose-Einstein condensate of 39K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intraspecies interactions at Feshbach resonances. We explore the tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a 39K condensate is interesting for future experiments requiring a weakly-interacting Bose gas.

Suggestions on meeting ASPAN standards in a pediatric setting.

Pediatric patients encompass a wide variety of ages and sizes that require specialized equipment and treatment plans. Managing all of these needs can be quite challenging. This article looks at each ASPAN standard and how it relates to the pediatric patient. Some standards are consistent across all patient care environments regardless of age, but some are appropriately adjusted to meet the needs of the pediatric population. Tips and ideas are provided on how to meet these standards not only in dedicated pediatric settings but also in institutions that care for few pediatric patients.

Oral granisetron for strabismus surgery in children.

PURPOSE: To determine the efficacy of oral granisetron in preventing postoperative vomiting (POV) following strabismus repair in children. METHODS: In a randomized, double-blind, placebo-controlled trial, 73 pediatric patients received either placebo, 20 micrograms.kg-1 or 40 micrograms.kg-1 granisetron po 20 min before induction of anesthesia. No premedication was given, induction was with halothane and all children breathed spontaneously via a laryngeal mask airway. Maintenance was with isoflurane without the use of opioids. Ketorolac and acetaminophen were used for analgesia. The number of episodes and the severity of vomiting and retching were recorded for the first 24 hr postoperatively, as was the use of rescue antiemetics. RESULTS: Granisetron 20 micrograms.kg-1 and 40 micrograms.kg-1 were more effective than placebo in reducing the incidence of POV during the first 24 hr (29% in both the granisetron groups vs 84% in the placebo group, P < 0.05). In addition, the number of children experiencing severe vomiting (> or = 3 episodes) was reduced in the granisetron 20 micrograms.kg-1 and 40 micrograms.kg-1 groups compared with placebo (4%, 8% and 48% respectively, P < 0.05). Patients in the granisetron group were discharged home earlier (105 min vs 124 min, P = 0.04). There was no difference in the incidence of POV between the two granisetron groups. CONCLUSION: Preoperative oral granisetron in a dose of 20 micrograms.kg-1 provided effective prophylaxis against POV in children undergoing stabismus repair.

Prolonged recovery stay and unplanned admission of the pediatric surgical outpatient: an observational study.

STUDY OBJECTIVE: To determine the incidence of and reasons for prolonged length of stay in the postanesthesia care unit and unplanned hospital admissions of children scheduled for outpatient surgery. DESIGN: Prospective, observational cohort study. SETTING: C. S. Mott Children's Hospital, a tertiary care setting. PATIENTS: 168 ASA physical status I, II, and III children (birth to 18 years), 130 of whom experienced a prolonged length of stay and 61 who had an unplanned hospital admissions. MEASUREMENTS AND MAIN RESULTS: 3.9% of annual outpatient population experienced a prolonged length of stay, and 1.9% had an unplanned outpatient admission. Prolonged length of stay was most commonly due to postoperative nausea and vomiting (19%) or respiratory complications (16%), whereas unplanned hospital admissions were primarily for respiratory or surgical reasons (32% and 30%, respectively). Higher ASA status had a significant direct relationship with the incidence of unplanned outpatient admission and respiratory complications. Although most families were satisfied with the length of their child's care, 28% of parents whose children were sent home after a prolonged length of stay would have preferred a short hospital admission, and 16% of parents of children with an unplanned hospital admission would have preferred a longer stay in recovery and discharge home. CONCLUSION: Prolonged length of stay and unplanned hospital admissions were uncommon outcomes following pediatric outpatient surgery. However, the impact of such outcomes on hospital staffing and family convenience may have implications related to cost containment and patient satisfaction.

Pharmacoeconomics analysis in a pediatric population.

BACKGROUND: Pharmacoeconomics is becoming increasingly important in the health-care environment, but pharmacoeconomic studies are fraught with problems. Pharmacoeconomics can be applied to analysis of the benefits of pharmacologic hemostasis. METHODS: This article reviews the available methods of pharmacoeconomic analysis and their inherent methodologic concerns. It reviews pharmacoeconomic studies of pharmacologic hemostasis, with particular focus on the Pediatric Reoperative Open Heart Surgery study. In this study, patients were randomized to receive either high-dose aprotinin, low-dose aprotinin, or placebo. Results were analyzed from the viewpoint of cost-benefit, cost-effectiveness calculated with use of a roll-back decision tree, and cost-effective ratios. RESULTS: Cost-benefit analysis showed low-dose aprotinin to have a greater cost-benefit than high-dose aprotinin, cost-effectiveness analysis and analysis of cost-effective ratios showed high-dose aprotinin to be more cost-effective than low-dose aprotinin, and all analyses showed aprotinin to be preferable to placebo. CONCLUSIONS: Aprotinin in pediatric repeat open heart operations not only has a cost-benefit but is cost-effective as well.

The efficacy and cost of aprotinin in children undergoing reoperative open heart surgery.

We performed a prospective, randomized, placebo-controlled, double-blind trial to assess the efficacy of aprotinin in 61 children (median age 3.7 yr) undergoing reoperative open heart surgery (OHS). Three demographically similar groups were studied: large-dose aprotinin (ALD), small-dose aprotinin (ASD), and placebo (P). Over the first 24 postoperative hours fewer patients in the aprotinin groups received packed red cells (ALD, 53%; ASD, 89%; and P, 95%; P = 0.001), platelets (ALD, 32%; ASD, 50%; and P, 65%; P = 0.04), and fresh frozen plasma (ALD, 16%; ASD, 17%; and P, 60%; P = 0.003) than placebo patients. Most importantly, aprotinin patients had fewer exposures to banked blood components (ALD, median 1 U; and ASD, median 2 U) than P (median 6 U; P = 0.001), with no difference in overall complication rate. Use of aprotinin was associated with a savings in the patient charges for blood components, operating room time, and duration of hospitalization. In conclusion, aprotinin decreased the number of units of banked blood components used during the first 24 postoperative hours in reoperative pediatric OHS. Aprotinin thus decreases the risks associated with exposure to banked blood components and reduces hospital charges.

Should pregnancy testing be routine in adolescent patients prior to surgery?

The reliability of the preoperative history obtained from adolescent patients in ruling out pregnancy was prospectively evaluated. Four hundred forty-four patients who underwent 525 procedures were questioned preoperatively regarding the possibility of pregnancy. Regardless of the history, a urine pregnancy test was ordered in accordance with institutional practice. In 508 cases, patients denied the possibility of pregnancy. Eight patients stated that they might be pregnant, and in six cases the parents responded for the patients and denied the possibility of pregnancy. Seventeen patients were not tested due to patient/parent refusal (n = 9) or inability to void (n = 8). All pregnancy tests were negative except one that was questionably negative. This patient had denied the possibility of pregnancy and had been anesthetized prior to test results. Follow-up revealed that the patient was not pregnant. Our data demonstrate that the preoperative history obtained from adolescent patients at our institution regarding their pregnancy status was in agreement with pregnancy test results. We suggest that a detailed history regarding last menstrual period, contraception, sexual activity, and the possibility of pregnancy be obtained in all postmenarchal patients presenting for surgery. Although in other populations history and pregnancy testing did not agree 100% of the time, for our adolescent population, human chorionic gonadotrophin (HCG) testing appears to be necessary only if indicated by patient history.

Age-related differences in heparin sensitivity and heparin-protamine interactions in cardiac surgery patients.

OBJECTIVE: The present study was conducted to determine how children and adults differ (it at all) with respect to sensitivity to heparin activity and heparin-protamine interactions during cardiac surgery requiring cardiopulmonary bypass (CPB). DESIGN: A prospective study of both children and adults undergoing CPB. SETTING: A tertiary care academic medical center between July 1992 and October 1994. PARTICIPANTS: Ninety patients who had cardiac or aortic arch surgery using CPB. The median age of the entire study sample was 15.8 years (range 2 months to 72 years). INTERVENTION: Data were obtained using the Medtronic Hemotec Hepcon Hemostasis Management System (Englewood, CO). An ex vivo heparin dose-response (HDR) curve was generated for each patient before skin incision to determine the target heparin concentration (THC) needed to achieve an activated coagulation time (ACT) of at least 480 seconds. Protamine dose was determined on the basis of whole blood heparin concentration estimated by means of a heparin-protamine titration. MEASUREMENTS AND MAIN RESULTS: The study population was divided into four groups based on age: infants (< 1 year), preschool (1 to 5 years), school-age (5 to 14 years) and adults (> 14 years). The mean +/- SD THC for the preschool group was 4.0 +/- 1.1; for infants, 3.3 +/- 0.7; for school-age, 3.1 +/- 0.7; and for adults, 3.4 +/- 0.7. The initial dose of heparin needed to achieve this THC (mean +/- SD) was significantly higher in infants (578 +/- 220 U/kg) and preschool children (477 +/- 159 U/kg) than in school-age children (327 +/- 57 U/kg) and adults (332 +/- 64 U/kg). The ratio of protamine to heparin was significantly higher in adults (1.4 +/- 0.5) and school-age children (1.3 +/- 0.6) than in infants (1.1 +/- 0.7) and preschool children (1.1 +/- 0.4). CONCLUSIONS: Pre-school children are less sensitive to heparin but also display a wider range of sensitivity. The data in this study support the use of 300 U/kg of heparin before CPB in patients > or = 5 years but suggest that heparin requirements may be greater in the younger patient who may require as much as 500 U/kg to achieve what is believed to be an appropriate target heparin concentration for initiating CPB.

The activated coagulation time: suitability for monitoring heparin effect and neutralization during pediatric cardiac surgery.

OBJECTIVES: To determine how the stage of surgery affects the relationship between activated clotting time (ACT) and heparin effect in children undergoing cardiac surgery using cardiopulmonary bypass (CPB) and to compare the results of ACT determinations made with two different coagulation timers using different clot detection technologies and activator compositions. DESIGN: Prospective, paired observation. SETTING: Tertiary care children's hospital affiliated with an academic medical center. PARTICIPANTS: Fifty-eight children scheduled for nonprimary cardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: ACTs were measured by two different commercially available automated coagulation timers (Hepcon Hemostasis Management System [HP] and the Hemochron model 801 [HM]) at four different time points over the course of cardiac surgery requiring CPB in patients ranging in age from 0.16 to 19 years. Simultaneous determinations of whole blood heparin concentration using heparin-protamine titrations were made as well. When the two methods of ACT determination were compared, baseline ACTs were not significantly different. HP ACT prolongation after heparin administration but before bypass was significantly less than HM ACT prolongation (median ACT range HM > or = 999 seconds; HP, 560 to 679; p = 0.006). Twenty-one percent of the HP ACTs and none of the HM ACTs fell below the 480 seconds required at this institution for the initiation of CPB (p = 0.008). Both instruments showed a significant further prolongation of ACT after initiation of bypass (median ACT range HP > or = 999 seconds; HM > or = 999; p < 0.001 for both), whereas the heparin concentration decreased significantly (before, 3.5 +/- 0.2 U/mL; after, 2.7 +/- 0.1; p < 0.001). After termination of CPB and heparin neutralization, no significant difference between the ACTs was found. However, four HP ACTs were > or = 999 seconds despite simultaneous HM baseline values and whole blood heparin concentrations of zero. Heparin concentration correlated with ACT prolongation using both the HM (Spearman p = 0.36; p = 0.02) and the HP (Spearman p = 0.57; p = 0.0025) instruments before, but not 10 minutes after, initiation of bypass. CONCLUSIONS: In pediatric cardiac surgery, the relationship between ACT and heparin concentration changes depending on when during the surgery the ACT is measured. ACT prolongation in children anticoagulated for CPB correlates poorly with heparin concentrations during CPB. HP and HM ACT tests are not interchangeable. The HM ACT is a better indicator of heparin neutralization than the HP ACT. On the other hand, continued prolongation of the HP ACT after heparin neutralization may be related to risk of postoperative hemorrhagic complications. If devices from different manufactures are freely substituted for each other, clinical practice may be altered in an uncontrolled manner.