Are conceptual knowledge and procedural knowledge empirically separable? The case of fractions.

BACKGROUND: Concerning students' difficulties with fractions, many explanatory approaches are based on the distinction between conceptual knowledge and procedural knowledge. For further research in this field, it is thus crucial to make these constructs accessible to valid measurement. AIMS: In this study, we aim at developing a test instrument that affords valid measurement of students' conceptual and procedural fraction knowledge, including in particular empirical validation of this distinction. SAMPLE: The data used in this study were from 8th- and 9th-grade students (N = 235) in Germany. METHODS: Facilitated by expert discussions, items from previous studies were developed further and assigned to either a conceptual scale or procedural scale. Confirmatory factor analysis was used to investigate the underlying structure of the data including model comparisons (1-dimensional; conceptual-procedural, verbal-non-verbal). Further analyses in terms of validation focused on reliability and on correlations of the knowledge types with general cognitive abilities. RESULTS: It was found that the theoretically assumed 2-dimensional model fitted the data best. Correlations of the two knowledge types with general cognitive abilities differed significantly. Furthermore, the latent constructs could be reliably estimated from its indicators. CONCLUSIONS: Our findings indicate that the empirical separation of conceptual and procedural fraction knowledge is possible: A theoretically grounded test instrument was developed that allows measuring the knowledge types with a sufficient degree of validity. These findings address a research gap that was pointed out repeatedly and gives rise to further research into reasons and remedies for students' difficulties in dealing with fractions.

Comparing low volume saphenous-obturator block with placebo and femoral-obturator block for anterior cruciate ligament reconstruction.

BACKGROUND: Anterior cruciate ligament reconstruction (ACL-RC) is often associated with moderate to severe postoperative pain even with a multimodal analgesic regimen. We aimed to compare the analgesic efficacy of low volume saphenous-obturator block with placebo and femoral-obturator block in patients undergoing ACL-RC. METHODS: In a randomized controlled trial eighty-two patients undergoing ACL-RC with hamstring autograft were allocated to either low volume saphenous-obturator block, placebo block or femoral-obturator block. Ropivacaine 0.75% was used for active blocks and saline for placebo. Primary outcome was pain-scores at rest quantified as area-under-the-curve 0-6 hr postoperatively. Secondary outcomes were postoperative opioid consumption and pain localization in the knee. RESULTS: No statistical difference existed between groups in area-under-the-curve 6 hr pain-scores. However, pain-scores were significantly lower in the two ropivacaine groups compared to placebo at emergence t=0 (P<0.018), at t=5 (P<0.042) and at t=6 hours (P<0.002) postoperatively. Furthermore, ropivacaine blocks exhibited significantly reduced total opioid consumption (15.81 and 18.44 mg) postoperatively compared with placebo (26.38 mg) (P<0.018). Patients receiving ropivacaine blocks localized pain in the posterolateral knee, whereas placebo block patients reported anteromedial and central pain. Other secondary outcomes were similar between groups. CONCLUSIONS: Low volume saphenous-obturator block is significantly more effective than placebo in reducing both early and late pain-scores as well as postoperative opioid consumption in patients undergoing ACL-RC. No statistical difference existed when comparing low volume saphenous-obturator block to femoral-obturator block regarding early and late pain-scores and postoperative opioid consumption.

[The Lazarus phenomenon].

The pathophysiological mechanisms of auto resuscitation - also called the Lazarus phenomenon - are unknown, but they are thought to be related to matters such as hyperkalaemia, hyperventilation and alkalosis or increased end-expiratory pressure during assisted ventilation. The phenomenon is probably underreported and this case report of the Lazarus phenomenon in a patient with severe hyperkalaemia demonstrates the necessity of following recommendations regarding resuscitation such as allowing pauses in assisted ventilation as well as ten minutes post resuscitation monitoring before declaring the patient dead.

Ultrasound-guided single-penetration dual-injection block for leg and foot surgery: a prospective, randomized, double-blind study.

BACKGROUND AND OBJECTIVES: We describe a new approach to blocking the sciatic and saphenous nerves in the proximal thigh (level of the lesser trochanter or immediately below) using a single-penetration dual-injection (SPEDI) technique. The popliteal-sciatic approach necessitates repositioning of the leg exposing the popliteal fossa and an extra injection for the saphenous nerve (SAN) block at the midthigh level. We introduce an alternative, effective, and possibly faster method. METHODS: Sixty patients undergoing leg and foot surgery under general anesthesia were included. We deposited 15 mL of ropivacaine 0.75% around the sciatic nerve (SCN) and 5 mL of ropivacaine 0.75% at the SAN. Patients were randomized to the popliteal-sciatic/saphenous technique or the SPEDI technique. The primary outcome measure was performance time. Positioning time, pain assessment, nausea in the postanesthesia care unit, sufentanil demand, dermatomal anesthesia, and degree of motor blockade were also recorded. RESULTS: Performance time was significantly faster with the SPEDI technique (median time, 110 seconds [range, 57-315 seconds] vs 246 seconds [range, 163-472 seconds]; P < 0.0001). Positioning time was significantly shorter with the SPEDI technique (P < 0.0001). No other statistically significant differences were recorded. CONCLUSIONS: The SPEDI block resulted in significantly faster performance time and reduced positioning time with statistically equal efficacy in relation to pain assessment, nausea, sufentanil demand, dermatomal anesthesia, and motor blockade. The SPEDI block is statistically an equally effective alternative to the traditional popliteal-sciatic/saphenous block combination for leg and foot surgery, but it is faster, requires only 1 skin penetration, and does not require repositioning of the leg.

Anesthetizing the obese child.

The prevalence of childhood obesity is increasing. The focus of this review is the special anesthetic considerations regarding the perioperative management of obese children. With obesity the risk of comorbidity such as asthma, obstructive sleep apnea, hypertension, and diabetes increases. The obese child has an increased risk of perioperative complications especially related to airway management and ventilation. There is a significantly increased risk of difficult mask ventilation and perioperative desaturation. Furthermore, obesity has an impact on the pharmacokinetics of most anesthetic drugs. This has important implications on how to estimate the optimal drug dose. This article offers a review of the literature on definition, prevalence and the pathophysiology of childhood obesity and provides suggestions on preanesthetic evaluation, airway management and dosage of the anesthetic drugs in these patients. The authors highlight the need of supplemental studies on various areas of the subject.

Delivery of medical care for migrants in Germany: delay of diagnosis and treatment.

BACKGROUND: Migrants form 9% of Germany's population and 13% of its capital Berlin. Only limited data are available regarding general health status and prevalence of tropical diseases among migrants in Germany. This study was conducted to investigate the spectrum and frequency of tropical diseases among migrants in Berlin and to evaluate the quality of the medical care provided. The necessity of a routine screening for tropical diseases among migrants was assessed. METHODS: Anonymized data of migrants presenting to the Berlin Institute of Tropical Medicine between 1999 and 2004 with a stay in Germany below 1 year (n= 153) were analyzed. RESULTS: Of all examined migrants, 48% needed immediate medical treatment and 38% carried an infectious disease, mainly nematodes and intestinal protozoa. 19% suffered from a noninfectious disease, mainly anemia, and 12% were transferred to other specialists for further investigation. These figures were similar among asymptomatic and symptomatic patients. The median duration of stay in Germany until presentation was 42 days. While 40% of the migrants were examined within the first 4 weeks of their stay, 20% had not received a medical examination after 6 months. Of this population, 50% required treatment upon presentation. CONCLUSIONS: The high proportion of delayed diagnosis and treatment indicates a lack of medical service for migrants. While this clearly translates into increased health risks for the individual patient, it also indicates a potential risk for transmission of communicable diseases in the community. The lack of a correlation between symptoms and detected infectious disease indicates the need for a standardized routine screening examination in all migrants.