The effects of sevoflurane and halothane anesthesia on cerebral blood flow velocity in children.

UNLABELLED: We compared cerebral blood flow velocity during anesthesia with sevoflurane and halothane in 23 children admitted for elective surgery (age, 0.4-9.7 yr; median age, 1.9 yr; ASA physical status I-II). Inhaled induction was performed in a randomized sequence with sevoflurane or halothane. Under steady-state conditions, cerebral blood flow velocity (systolic [V(s)], mean [V(mn)], and diastolic [VD]) were measured by a blinded investigator using transcranial pulsed Doppler ultrasonography. The anesthetic was then changed. CBFV measurements were repeated after washout of the first anesthetic and after steady-state of the second (equivalent minimal alveolar concentration to first anesthetic). The resistance index was calculated. VD and V(mn) were significantly lower during sevoflurane (V(mn) 1.35 m/s) than during halothane (V(mn) 1.50 m/s; P = 0.001), whereas V(s) was unchanged. The resistance index was lower during halothane (P < 0.001). Our results indicate lower vessel resistance and higher mean velocity during halothane than during sevoflurane. IMPLICATIONS: The mean cerebral blood flow velocity is significantly decreased in children during inhaled anesthesia with sevoflurane than during halothane. This might be relevant for the choice of anesthetic in children with risk of increased intracranial pressure, neurosurgery, or craniofacial osteotomies.

Influence of infusion line compliance on drug delivery rate during acute line loop formation.

OBJECTIVE: To determine whether infusion line compliance contributes to irregular drug delivery during vertical displacement of syringe pumps. DESIGN: Five different commercially available infusion lines were studied at infusion rates of 0.5, 1.0, and 1.5 ml/h. Zero drug delivery time was measured after acute line loop formation (70 cm) using an electronic balance. Compliance of each infusion line was calculated using a pressure transducer and measurement of the occlusion release bolus at 300 mmHg occlusion pressure. Finally, the influence of infusion line compliance on drug delivery during acute lowering of the syringe pump was studied using low- and high-compliance infusion lines. RESULTS: Acute line loop formation resulted in zero drug delivery time from 5.1 +/- 1.5 to 44.0 +/- 6.8 s at flow rates of 0.5 ml/h. Increased flow rates significantly reduced loop-induced flow variability. A close correlation was found between zero drug delivery time and calculated infusion line compliance at 0.5 ml/h (linear regression R2 = 0.79). Lowering of the syringe pump 50 cm prolonged zero drug delivery time from 295.8 +/- 20.7 s with the low-compliance tube to 463.3 +/- 24.0 s with the high-compliance infusion line. CONCLUSIONS: Infusion line compliance contributes to irregular drug delivery associated with vertical displacement of syringe pumps. Siphoning of the infusion line during patient care should be avoided, and flow rates of 1 ml/h or higher are recommended. Low-compliance infusion lines are indicated whenever highly short-acting vasoactive drugs at low delivery rates are administered.

Do antisiphon valves reduce flow irregularities during vertical displacement of infusion pump systems?

Vertical displacement of syringe pumps may cause irregular drug delivery due to hydrostatic pressure changes in the infusion line. The extent of flow fluctuations depends on the internal compliance of infusion lines, syringes and syringe pumps. We evaluated whether pressure regulation by antisiphon valves (ASV) reduces the flow variation during vertical displacement of 50 ml standard syringes and infusion pumps. An infusion assembly comprising a standard 50 ml BD Plastipak or a 50 ml Fresenius syringe, with syringe pump and 2 m low compliance infusion line was used for in vitro measurement of fluid delivery. The assembly was tested without ASV, and with two ASVs of differing operating pressure (ASV:75: valve opening pressure = 75 mmHg; ASV:155, 155 mmHg). Retrograde aspiration volume, zero-drug delivery time and valve opening bolus were determined after lowering the syringe pump by 50 cm. After elevating the syringe pump to its initial position the ensuing infusion bolus was recorded. Without an antisiphon valve the observed zero-drug delivery times after lowering the syringe pump were (mean +/- SD) 2.4 +/- 0.2 min using the BD Plastipak syringe and 4.09 +/- 0.55 min using the Fresenius syringe. Introduction of the antisiphon valve prolonged the zero drug delivery time 58% (ASV:75) and 88% (ASV:155) in the BD Plastipak syringe assembly and 43% (ASV:75) and 81% (ASV:155) in the Fresenius syringe assembly (P < 0.001). Antisiphon valves worsen flow irregularities caused by vertical displacement of syringe pumps and when used with delivery of concentrated inotropic drugs at low infusion rates, they may aggravate haemodynamic consequences of inconstant drug delivery.

[The effect of air within the infusion syringe on drug delivery of syringe pump infusion systems] . / Auswirkungen von Luftbläschen in der Infusionsspritze auf die Funktion von Spritzenpumpen.

Application of highly concentrated short-acting vasoactive drugs in the critically ill patient requires precisely working syringe pump systems for continuous intravenous drug delivery. We performed a bench study to investigate the consequences of small amounts of air entrapped within a 50-ml infusion syringe. In particular we studied the effect of entrapped air on drug delivery after moderate vertical displacement of the pump by 50 cm (e.g. in preparation for transport) and the effect on the time required to trigger the pressure alarm after occlusion of the infusion line. At a flow rate of 1 ml/h, lowering the syringe pump prolonged the zero-drug delivery time from (mean +/- SD) 4.1 +/- 0.8 min (without air) to 6.2 +/- 0.9 (with 1 ml air) and to 13.1 +/- 0.9 min (with 2 ml of air, p < 0.001 for all comparisons). Entrapping of 2 ml of air within the syringe resulted in a 2.6-fold prolongation of the occlusion alarm time after accidental occlusion of the infusion line and a 3-fold increase of the resulting infusion bolus after occlusion. Enclosed air within infusion syringes considerably affects the syringe compliance. It increases the susceptibility of constant drug delivery to vertical displacement of syringe pumps and impairs the occlusion alarm function. Therefore, any air in syringe of infusion pump systems should be carefully removed. To avoid infusion boluses of short-acting vasoactive drugs after accidental occlusions, the occluded infusion line should be released to ambient pressure first.

Oral vitamin K1 prophylaxis for newborns with a new mixed-micellar preparation of phylloquinone: 3 years experience in Switzerland.

UNLABELLED: In 1995, a new water-soluble mixed-micellar analogue of vitamin K1 (Konakion MM paediatric) was introduced in Switzerland to replace the formerly used fat-soluble Konakion drops for the prevention of vitamin K1-deficiency-bleeding (VKDB) in infants. According to the new guidelines, an oral dose of 2 mg is given after birth and again on the 4th day of life. We examined the compliance with these guidelines and the impact on the incidence of VKDB. To assess compliance, questionnaires were sent to all hospitals with delivery services 6 months after the introduction of the new guidelines. Using the database of the Swiss Paediatric Surveillance Unit (SPSU) which records rare paediatric diseases, we assessed the incidence of VKDB in Switzerland between July 1995 and June 1998. In addition, we determined the precise circumstances under which the episodes of VKDB occurred. More than 99% of infants received vitamin K1 prophylaxis. Since July 1995, 93% of newborns have received prophylaxis according to the new guidelines; the remaining infants were given fat-soluble Konakion drops or parenteral vitamin K1. Within 3 years, one case of classical and 12 cases of late-onset VKDB (11 confirmed, 1 probable) were reported to the SPSU. Of the 11 confirmed late-onset cases, 7 received the recommended prophylaxis, whereas 3 had not and 1 had been given fat-soluble Konakion drops. All confirmed cases of late-onset VKDB occurred in fully breast-fed infants and 8 of 11 had hepatobiliary disease. CONCLUSION: With the introduction of two oral doses of a mixed-micellar vitamin K1 preparation administered in the 1st week of life, the incidence of late vitamin K1-deficiency-bleeding has decreased from 7.2:100,000 between 1986-1987 to 2.8:100,000 between 1995 and 1998. This regimen may be suitable for prophylaxis of vitamin K1-deficiency-bleeding, however, it does not fully protect infants with cholestatic disease from late-onset bleeding. If oral prophylaxis is considered for these infants, vitamin K1 has to be administered repeatedly to all infants during the breast feeding period.

Comparison of cerebral blood volume measured by near infrared spectroscopy and contrast enhanced magnetic resonance imaging.

Cerebral blood volume (CBV) can be quantified by both near infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI). The aim is to compare CBV results obtained by NIRS and MRI in adult patients. 10 adult patients, 6 females and 4 males, age median 24 (range 21 to 76) years, were included in this study. All needed a MRI investigation with contrast medium for clinical reasons. The NIRS instrument, the Cerebral RedOx Monitor 2020 from Critikon, quantifies cerebral haemoglobin concentration using a sensor with two receiving channels at different distances. Geometrical detector arrangements of this type enable a ratio measurement to be achieved, which reduces the contribution of the skull and skin, thus allowing quantification. Cerebral haemoglobin concentration can be converted in CBV, as the haemoglobin concentration in the blood is known. CBV can be quantified by MRI using an indicator dilution method. The method requires an injection of a paramagnetic contrast agent. The input function can be measured at the throat and thus perfusion images can be quantified. CBV was measured by NIRS just before the patient entered the magnet and after he had left it. The sensor for the NIRS measurement was applied to the patients front three times for 1 minute to each side, avoiding the sinuses. CBV was determined by contrast enhanced MRI between the NIRS measurements. The mean CBV (NIRS) was 8.6 (SD 1.3) ml/100 g and CBV (MRI) was 7.1 (SD 2.5). The correlation between CBV (NIRS) and CBV (MRI) was Pearson's correlation coefficient -0.297 (p = 0.204) respectively Spearman's rho (nonparametric) -0.266 (p = 0.257). The CBV values obtained by NIRS and MRI, even though they are in the same range, do not correlate.

[Sedation and analgesia in childhood]. / Sedation und Analgesie im Kindesalter.

As a rule the indication for sedation should be broad. Any child who is, or could be, frightened by an intervention should have the benefit of sedation. Correspondingly, an analgesic should be chosen if the intervention is painful. The sedatives of choice are midazolam and chloral hydrate, and possibly a neuroleptic for interventions which require the child to be motionless. Any physician who sedates a child must be aware of the side effects of the sedation and be well versed in countermeasures, including resuscitation. The dangers of sedation arise from wrong selection of patients and also from postsedation and combination of sedatives and analgesics; both should be left to experienced physicians or specialists. If sedation or analgesia is planned with the rest of the intervention and the described guidelines are followed, the patient's safety is ensured. Despite all efforts a small proportion of patients show an inadequate response to the chosen medication. In young children and in sick children the specific physiological and anatomical features will overtax the therapist. In such cases the help and advice of a specialist trained in paediatric anaesthesia can and should be sought.

Congenital hemiplegia: morphology of cerebral lesions and pathogenetic aspects from MRI.

We have analyzed the MRI findings from the brains of 33 children with congenital hemiplegia. Referral of these children to our hospital was either because of neurological problems or a history of complicated birth. According to maturation-dependent pathophysiological mechanisms we have classified the lesions into the following five groups: 1. malformations/prenatal encephalo-clastic lesions, 2. periventricular leukomalacia or atrophy, 3. diencephalic lesions, 4. subcortical and cortical lesions, and 5. normal findings. Combination of lesions was not uncommon. The neuroradiologically most prominent and most expanded lesions determined the classification to the different groups. We detected malformations/encephalo-clastic lesions (Group 1) in 5 children; one of these children also presented additional lesions of Groups 2 and 3. Six children displayed periventricular leukomalacia (Group 2), and in one child in combination with diencephalic and subcortical lesions. Ten children exhibited diencephalic lesions (Group 3), in one case combined with periventricular leukomalacia. The MRI of seven children showed subcortical/cortical lesions (Group 4), in four cases extending into diencephalic structures. Two children had a combination of evenly matched periventricular, diencephalic and subcortical/cortical lesions, where it was impossible to define a principal lesion. Three children had normal MRI findings. Significantly, 8 of 33 children had bilateral lesions although presenting with hemiplegia. The large proportion of diencephalic lesions, not described in similar CT studies, and the small number of normal MRI findings show the value of MRI in evaluation of congenital hemiplegia. The ability to correlate, to some extent, neuroradiological findings of damage to developmental stage affords the conclusion that at least a third of the children in our series with congenital hemiplegia suffered prenatal damage.

[Diagnostic imaging of the brain of blind and visually handicapped young children]. / Bildgebende Untersuchungen des Gehirns bei blinden und sehbehinderten Kleinkindern.

In infants with delayed or absent visual maturation a neuroradiological investigation of the brain is commonly performed in addition to neurophysiological examinations. We report our preliminary experience with magnetic resonance imaging (MRI). MRI allows a detailed anatomical assessment and an evaluation of the myelination, including the optic radiation. Following severe perinatal hypoxic-ischemic injury periventricular leukomalacia in the parieto-occipital region was a common finding. The findings in infants with or without ocular abnormalities were heterogeneous, including normal findings, nonspecific delays of cerebral myelination as well as several malformations (such as corpus callosum hypoplasia, Aicardi syndrome, septo-optic dysplasia, migration disorders). In the individual case the neuroradiological findings do not allow to draw conclusions to the visual function and prognosis. In children with Leber congenital retinal amaurosis we have observed a normal myelination of the optic radiation. In many cases, particularly if a syndromic diagnosis is reached, neuro-imaging gives useful information for prognostic and genetic counselling.