Erik Michel

Gosling's Doppler pulsatility index revisited.

In Doppler sonography, the physiological meaning of Goslings pulsatility index (PI) as a measure of downstream resistance is still under dispute. We deliver the theoretical derivation of its physiological significance. We present a mathematical model based on the linked theories of critical closing pressure (CCP) and cerebrovascular impedance, verified in preterm neonates. Mathematical transformation results in a series of equations interrelating several physiological parameters. Instead of indicating cerebrovascular resistance, PI is linked to the ratio of cerebrovascular impedances at the heart rate and at zero frequency. Next to arterial blood pressure, CCP is the principal determinant of PI. PI is identical to the ratio of the alternate and the direct component of the effective driving force. Thus, PI has no distinctive physiological meaning by itself. At present, our model is confined to physiological conditions where the lowest velocity is the end diastolic, and always more than zero.

Pain in pediatric oncology — children's and parents' perspectives

There is a lack of valid epidemiological data on malignancy‐associated pain in modern pediatric oncology. Pediatric oncology patients (self‐assessment) and their parents from 28 hospitals were questioned using age‐adapted, structured interviews and validated pain assessment tools. Pain intensity was measured by the NRS and Bieri faces scale. We conducted 363 interviews with patients and their parents, and 46 with the parents alone (if patients <2.5 years). Pain was reported at the time of the interview or within the last 24 h, 7 d, or 4 weeks in 15%, 28%, 50% and 58% of cases, respectively. The proportion of patients suffering severe to maximal pain (NRS > 3; Bieri > 2) increased significantly (p = 0.001, χ2 test). The median pain intensity for the most severe pain episode within the last 4 weeks was 6.7 (NRS 0–10). Adverse effects of anti‐tumor therapy were the most frequent cause of pain. Multivariate analyses depicted general physical condition either “severely reduced” (ASA status 3) (OR 4.0, 95% CI 1.1‐14.7, p = 0.037) or “moderately reduced” (ASA status 2) (OR 1.8, 95% CI 1.1‐2.9, p = 0.018), “in‐patient status” (OR 1.8, 95% CI 1.2‐2.9, p = 0.010), and “co‐morbidity present” (OR 3.5, 95% CI 1.1‐10.7, p = 0.030) as risk factors for severe to maximal pain. General anesthesia was the only factor significantly (OR 0.14, 95% CI 0.05‐0.39, p < 0.01) associated with a reduction in the proportion of patients suffering severe to maximal pain during bone marrow aspiration. Our data emphasize both the importance of in‐house acute pain control and the need for general anesthesia during painful procedures in pediatric oncology.

Frequency Dependence of Cerebrovascular Impedance in Preterm Neonates A Different View on Critical Closing Pressure

The nonproportional relationship between instantaneous arterial blood pressure (BP) and cerebral blood flow velocity (CBFv) is well explained by the concept of critical closing pressure (CCP). We aimed to determine the frequency response of the neonatal cerebrovascular system, and to establish the exact mathematical relationship between cerebrovascular impedance and CCP under physiologic conditions. In 10 preterm neonates (gestational age, 25–32 weeks; birth weight, 685–1,730 g; age 1–7 days) we Doppler-traced CBFv of the internal carotid artery. Blood pressure was traced simultaneously. Critical closing pressure was graphically determined. Cerebrovascular impedance was calculated as the square root of the ratio of the corresponding peaks in the power spectra of BP and CBFv at zero frequency, and at heart rate (H) and harmonics (xH). Uniformly, the impedance between H and 3H (2 to 6 Hz) was reduced about fivefold, compared with the impedance at zero frequency. The cerebrovascular system behaves like a high-pass filter, leading to a reduction of the DC (direct current) component of CBFv (analogous to current) relative to that of the driving force BP (analogous to voltage). The frequency response of cerebrovascular impedance reflects the ratio of CCP and DC BP. A mathematical derivation of this relationship is given matching the observed results. Thus, both the CCP and the impedance approach are valid.

Stop the pain! A nation-wide quality improvement programme in paediatric oncology pain control

Introduction: Little is known about the impact of translation of pain management clinical practice guidelines on pain control in paediatrics. In an effort to overcome this, a longitudinal, nation‐wide, multi‐centre paediatric quality improvement (QI) study was initiated by the German Society of Pediatric Haematology and Oncology (GPOH) entitled Schmerz‐Therapie in der Onkologischen Paediatrie (STOP).

Buprenorphine TTS for children - a review of the drug's clinical pharmacology

Objective:  The transdermal therapeutic system (TTS) with buprenorphine is currently being used ‘off‐label’ to treat chronic pediatric pain. We compiled available pharmacokinetic (PK), pharmacodynamic (PD), and clinical pediatric data on buprenorphine to rationalize treatment regimens.

Snake: the development and validation of a questionnaire on sleep disturbances in children with severe psychomotor impairment

OBJECTIVE Sleep disturbance and daytime restlessness are present in 50% to 80% of children with severe psychomotor impairment due to neurologic or other complex diseases. Although these issues severely impair the quality of life of the children and their families, they are not well addressed or managed by professionals. The lack of validated assessment tools prevents further research and the development of adequate therapies. Our aim is to develop and validate a sleep questionnaire for these children that could be used both for clinical management and systematic research. METHODS The sleep questionnaire for children with severe psychomotor impairment (Schlaffragebogen für Kinder mit Neurologischen und Anderen Komplexen Erkrankungen, SNAKE) is based on expert opinion and consultation with parents. The psychometric quality of the questionnaire was assessed in a sample of 224 children with severe psychomotor impairment. RESULTS Confirmative factor analysis showed that SNAKE comprises of five factors (based on ICSD-2). Fit indices, analysis of item characteristics and convergent validity (coherence with measures of sleep [i.e., sleep efficiency]) and correlation with selected subscales of the Sleep Disturbance Scale for Children (SDSC) were good. Re-test analysis (n=62) depicted high stability and good replication of validity. CONCLUSIONS SNAKE is a reliable and valid tool for the diagnosis of sleep disturbances in children with severe psychomotor impairment. The SNAKE questionnaire is the first tool that addresses the specific relationship between sleep disturbance and severe disability in children.

Strukturelle und organisatorische Grundlagen

» Ich schaffe das alles nur, weil ich Ihre Telefonnummer habe. (Mutter eines Kindes mit lebenslimitierender Erkrankung zu einem Mitglied des padiatrischen Palliativteams) «

Can PRISM predict length of PICU stay? An analysis of 2000 cases

PRISM is claimed to score disease severity which has attributed an impact on length of PICU stay (LOS). Primary objective: To determine the impact of PRISM on LOS, and evaluate an Artificial Neural Networks (ANN) performance to estimate LOS from PRISM item patterns. Research design and methods: Retrospectively we performed correlation and regression analyses on routinely scored PRISM data of all consecutive admissions to our level-III PICU from 1994 to 1999 (n > 2000) with individual LOS. In addition, an ANN was trained on the chronologically first 75% of those data (inputs, PRISM items + age + sex; output, LOS). The ANNs performance was tested on the remaining most recent 25% of the data sets. Main results: The Spearman and Pearson coefficients of correlation between PRISM and LOS were 0.2 (p < 0.001) and 0.08 (p = 0.0003), the latter being slighly higher when LOS was logarithmically transformed. Pearsons coefficient of correlation between ANN derived LOS estimate and actual LOS was 0.21 (p < 0.001) (LOS logarithmically transformed: 0.34; p < 0.001) in the independent validation sample. Conclusions: The ANN with its intrinsic ability to detect non-linear correlation, and to relate specific item patterns to LOS, outperformed linear statistics but was still disappointing in estimating individual LOS. It might be speculated that therapeutic intervention modulates the natural course of the disease thus counteracting both disease severity as initially scored by PRISM, and LOS. This being true, the inverse of the correlation between PRISM (or PRISM based LOS estimate) and LOS might be a candidate indicator of quality of care.

Schmerztherapie in der Allgemeinpädiatrie

Eine Vielzahl von akuten Erkrankungen im Kindesalter geht mit Schmerzen einher. Schmerzen und Fieber sind die haufigsten Ursachen fur eine ungeplante Kinderarztkonsultation. Das Hauptanliegen von Padiater und Eltern ist die kurative Therapie der Grunderkrankung. Im Mittelpunkt des kindlichen Empfindens indes steht die Kontrolle der Leitsymptome „Schmerz und Stress“ — ihnen wird meist weniger Aufmerksamkeit geschenkt.

Differenzialdiagnose der Schmerzursachen

Akuter Schmerz hat die biologische Aufgabe, dem Organismus Vorgange zu signalisieren, die mit (potenzieller) Gewebsschadigung einhergehen, um sie lokalisieren und identifizieren zu konnen. Je nach Ursache finden sich charakteristische Muster der Gewebsschadigung, sodass Schmerzqualitat, -zeitverlauf und -lokalisation wichtige Hinweise auf die Schmerzursache geben konnen. Die physiologischen und pathophysiologischen Grundlagen werden ausfuhrlich in ▸ Kap. 1 vorgestellt.