A scalable high-performance magnetic shield for very long baseline atom interferometry

We report on the design, construction, and characterization of a 10 m-long high-performance magnetic shield for very long baseline atom interferometry. We achieve residual fields below 4 nT and longitudinal inhomogeneities below 2.5 nT/m over 8 m along the longitudinal direction. Our modular design can be extended to longer baselines without compromising the shielding performance. Such a setup constrains biases associated with magnetic field gradients to the sub-pm/s² level in atomic matterwave accelerometry with rubidium atoms and paves the way toward tests of the universality of free fall with atomic test masses beyond the 10^-13 level.

Variation of bispectral index under TIVA with propofol in a paediatric population

BACKGROUND

In this prospective observational study, we aim to explore the relationship between age and bispectral index (BIS) values at different plasma concentrations of propofol.

METHODS

Fifty children aged from 3 to 15 yr were included. Anaesthesia was induced using a target-controlled infusion of propofol with the Kataria pharmacokinetic model together with a bolus of remifentanil followed by a continuous infusion rate at 0.2 microg kg(-1) min(-1). Target plasma propofol concentration was initially stabilized to 6 microg ml(-1) and continued for 6 min. The target was then decreased and stabilized to 4 microg ml(-1) and then to 2 microg ml(-1). BIS values, plasma propofol concentration, and EEG were continuously recorded. In order to explore the relationship between variations in propofol concentration and the EEG bispectrum, we used a multiple correspondence analysis (MCA). Results are shown in median (range).

RESULTS

We found no statistical difference between BIS values with propofol 6 microg ml(-1) [23 (12-40)] and 4 microg ml(-1) [28 (9-67)]. At 2 microg ml(-1), BIS was significantly different [52 (24-71)], but a significant correlation between the age of children and BIS values was found (r2=0.66; P<0.01). There was little change in children's position between 6 and 4 microg ml(-1) in the structure model of the MCA. From 4 to 2 microg ml(-1), the position of children moved only on axis 2.

CONCLUSIONS

These results showed the difficulty to interpret BIS values because of the absence of significant change for higher plasma propofol concentration variation or because of the link with age for the lower plasma concentration.

Effect of epinephrine on epidural, intrathecal, and plasma pharmacokinetics of ropivacaine and bupivacaine in sheep

BACKGROUND

Local vasoconstriction induced by epinephrine added to epidural local anaesthetics has been shown to improve their quality and duration of action in several clinical reports. There are several assumptions on the mechanisms. This study was designed to evaluate the influence of epinephrine on transmeningeal uptake of epidurally administered ropivacaine and bupivacaine by measuring local anaesthetic concentrations in the epidural and intrathecal spaces and in plasma.

METHODS

Ropivacaine (50 mg) and bupivacaine (30 mg) were administered epidurally in sheep with and without epinephrine (75 microg). A microdialysis technique was used to simultaneously measure epidural and intrathecal drug concentrations. Resulting dialysate and plasma concentrations were used to calculate pharmacokinetic parameters for ropivacaine and bupivacaine.

RESULTS

Co-administration of epinephrine decreased epidural clearance for ropivacaine [0.6 (sd 0.1) vs 0.4 (0.1) ml min(-1)] but not significantly for bupivacaine [1.2 (0.4) vs 0.8 (0.3) ml min(-1)]. The resultant increase in epidural area under the concentration-time curves (31% for ropivacaine and 52% for bupivacaine) was also observed in the intrathecal space (21% increase for ropivacaine and 37% for bupivacaine). There was no significant influence of epinephrine on ropivacaine plasma pharmacokinetics. Plasma Cmax for bupivacaine was decreased.

CONCLUSIONS

These results show that epinephrine decreases the clearance and distribution processes involved in epidural disposition of ropivacaine and bupivacaine, leading to an increased uptake into the intrathecal space with an apparent more pronounced effect for bupivacaine.

Brain activity modeling in general anesthesia: enhancing local mean-field models using a slow adaptive firing rate

In this paper, an enhanced local mean-field model that is suitable for simulating the electroencephalogram (EEG) in different depths of anesthesia is presented. The main building elements of the model (e.g., excitatory and inhibitory populations) are taken from Steyn-Ross [M. L. Steyn-Ross, Phys. Rev. E 64, 011917 (2001), D. A. Steyn-Ross, Phys. Rev. E 64, 011918 (2001)] and Bojak and Liley [I. Bojak and D. T. Liley, Phys. Rev. E 71, 041902 (2005)] mean-field models and a new slow ionic mechanism is included in the main model. Generally, in mean-field models, some sigmoid-shape functions determine firing rates of neural populations according to their mean membrane potentials. In the enhanced model, the sigmoid function corresponding to excitatory population is redefined to be also a function of the slow ionic mechanism. This modification adapts the firing rate of neural populations to slow ionic activities of the brain. When an anesthetic drug is administered, the slow mechanism may induce neural cells to alternate between two levels of activity referred to as up and down states. Basically, the frequency of up-down switching is in the delta band (0-4 Hz) and this is the main reason behind high amplitude, low frequency fluctuations of EEG signals in anesthesia. Our analyses show that the enhanced model may have different working states driven by anesthetic drug concentration. The model is settled in the up state in the waking period, it may switch to up and down states in moderate anesthesia while in deep anesthesia it remains in the down state.

Effect of remifentanil with and without atropine on heart rate variability and RR interval in children

Remifentanil can cause bradycardia either by parasympathetic activation or by other negative chronotropic effects. The high frequency (HF) component of heart rate variability (HRV) is a marker of parasympathetic activity. This study aimed to evaluate the effect of remifentanil on RR interval and on HRV in children. Forty children ASA I or II were studied after approval by the human studies committee and informed parental consent was obtained. After stabilisation at sevoflurane 1 MAC, they were randomly divided into two groups: one received a 20 microg.kg(-1) atropine injection (AT + REMI) and the other ringer lactate solution (REMI). Three minutes later, a 1 microg.kg(-1) bolus of remifentanil was administered over 1 min, followed by a continual infusion at 0.25 microg.kg(-1).min(-1) for 10 min increased to 0.5 microg.kg(-1).min(-1) for a further 10 min. A time varying, autoregressive analysis of RR sequences was used to estimate classical spectral parameters: low (0.04-0.15 Hz; LF) and high (0.15-0.45 Hz; HF) frequency, whereas the root mean square of successive differences of RR intervals (rmssd) was derived directly from the temporal sequence. Statistical analyses were conducted by means of the multiple correspondence analysis and with non parametrical tests. Remifentanil induced an RR interval lengthening, i.e. bradycardia, in both groups compared to pretreatment values and was associated with an increase of HF and rmssd only for the REMI group. The parasympathetic inhibition by atropine did not totally prevent remifentanil's negative chronotropic effect. A direct negative chronotropic effect of remifentanil is proposed.

Impact of age on both BIS values and EEG bispectrum during anaesthesia with sevoflurane in children

BACKGROUND

The aim of this study was to evaluate the potential relationship between age, BIS (Aspect), and the EEG bispectrum during anaesthesia with sevoflurane.

METHODS

BIS and raw EEG were recorded at a steady state of 1 MAC in 100 children, and during a decrease from 2 to 0.5 MAC in a sub-group of 29 children. The bispectrum of the EEG was estimated using MATLAB software. For analysis, the bispectrum was divided into 36 frequencies of coupling (P(i))--the MatBis. A multiple correspondence analysis (MCA) was used to establish an underlying structure of the pattern of each individual's MatBis at 1 MAC. Clustering of children into homogeneous groups was conducted by a hierarchical ascending classification (HAC). The level of statistical significance was set at 0.05.

RESULTS

At 1 MAC, the BIS values for all children ranged from 20 to 74 (median 40). Projection of both age and BIS value recorded at 1 MAC onto the structured model of the MCA showed them to be distributed along the same axis, demonstrating that the different values of BIS obtained in younger or older children are mainly dependent on their MatBis. At 1 MAC, six homogeneous groups of children were obtained through the HAC. Groups 5 (30 months; range 23-49) and 6 (18 months; range 6-180) were the younger children and Group 1 (97 months; range 46-162) the older. Groups 5 and 6 had the highest median values of BIS (54; range 50-59) (55; range 26-74) and Group 1 the lowest values (29; range 22-37).

CONCLUSION

The EEG bispectrum, as well as the BIS appeared to be strongly related to the age of children at 1 MAC sevoflurane.

Recommandations concernant la mise en place, la gestion, l’utilisation et l’évaluation d’une salle d’accueil des urgences vitales pédiatriques

The pediatric resuscitation room is the place where children suffering from vital distress are cared for in the emergency unit. Recommendations for its organization, functioning and evaluation have been ruled on by experts from six medical societies involved in these emergencies. They concern all the hospital's physicians, nurses and administrative directors.

Limits of corrected flow time to monitor hemodynamic status in children

OBJECTIVE

Doppler corrected flow time (i.e., corrected left ventricular ejection time) as a noninvasive tool for assessing hemodynamic changes has been previously reported for adult patients. Its use in paediatrics seems to be worthwhile but no data concerning its accuracy are presently available in this population. The purpose of this work was to study the relationships between corrected flow time (FT) and indices of systemic vascular resistance (SVR) and of myocardial contractility in healthy children.

METHODS

Twenty healthy children performed a graded maximal bicycle exercise in order to induce physiological hemodynamic alterations. Hemodynamic parameters were measured with an echocardiography-Doppler at rest and within a few minutes of post exercise. Cycle time (RR), mean aortic flow velocity, mean systolic velocity (MSV), FT, peak velocity (PV), and stroke distance were measured on the Doppler aortic velocity waveform. Cardiac index (CI) and SVR were calculated from the classical volumetric equation. Corrected FT was calculated by using Bazett's formula (FTb = FT/square root(RR)) and a simplified formula FTc = FTmeasured + [1.29 x (HR - 60)].

RESULTS

Post exercise, SVR, RR, FT, decreased, while CI, PV and MSV increased and stroke distance remained unchanged. After multiple regression analysis no significant correlation between SVR and FTb and SVR or FTc was noted. A significant correlation appeared between FTb and, respectively, PV (r = -0.83; p < 0.001), stroke distance (r = 0.78; p < 0.001) and RR (r = -0.52; p = 0.0016). A significant correlation was also shown between FTc and, respectively, PV (r = -0.71; p < 0.001) and stroke distance (r = 0.63; p < 0.001) but not with RR.

CONCLUSIONS

These results show that the use of Bazett's formula correct FT could lead to hemodynamic misinterpretations, because it does not rule out all the heart rate effect. Moreover, in healthy children corrected FT appears as an inaccurate index to monitor physiological afterload alterations, because of the involvment of other hemodynamic factors such as contractility in its variation.

Absolute bioavailability of midazolam after subcutaneous administration to healthy volunteers

AIMS

Midazolam is given intravenously for induction of anaesthesia and conscious sedation and by subcutaneous infusion in patients in palliative care units. The objective of the present study was to determine the absolute bioavailability of subcutaneous midazolam and its pharmacokinetics in young, healthy, male volunteers.

METHODS

Eighteen volunteers were given single doses of 0.1 mg kg-1 midazolam i.v. and s.c. after a wash-out period of 7-15 days in an open-label, randomized, cross-over study. Blood samples were collected up to 12 h post-infusion. Plasma concentrations of midazolam and of its two metabolites, 1'-OHM and 4-OHM, were assessed using an h.p.l.c.-MS method (LOQ 0.5 ng ml-1 for each analyte). Vital signs, cardiac parameters and oximetry were monitored. Local tolerance was determined and adverse events were also monitored.

RESULTS

After s.c. infusion t(max) and C(max) were 0.51 +/- 0.18 h and 127.8 +/- 29.3 ng ml-1 (mean +/- s.d.), respectively. No statistically significant difference was detected in AUC(0, infinity ) after i.v. and s.c. administration. The mean (+/- s.d.) absolute bioavailability of subcutaneous midazolam was 0.96 (+/- 0.14) (CI 0.84, 1.03). Mean (+/- s.d.) t1/2 was similar after s.c. (3.2 (+/- 1.0) h) and i.v. infusion (2.9 (+/- 0.7) h), although a statistically significant difference was reached (P < 0.05). Mean CL and V of i.v. midazolam were 4.4 +/- 1.0 ml min-1 kg-1 and 1.1 +/- 0.2 l kg-1 (mean +/- s.d.), respectively. Plasma concentrations of 1'-OHM were higher than those of 4-OHM. Few mild and transient adverse events were noted and there were no clinically significant effects on EEG, blood pressure and laboratory parameters.

CONCLUSIONS

This study has shown that subcutaneous midazolam has excellent bioavailability and that administration of midazolam by this route could be preferable when the intravenous route is inappropriate.

[Prevention of pain on injection with propofol in children: comparison of nitrous oxide with lidocaine]

INTRODUCTION

Injection pain caused by propofol is an important disadvantage, especially in children, incompletely reduced by adding lidocaine intravenously. Nitrous oxide's analgesic effects, well known, have never been evaluated on pain due to propofol.

OBJECTIVE

To compare the effects of nitrous oxide with lidocaine on pain on injection caused by propofol in children.

STUDY DESIGN

Double blind, randomised, prospective study.

PATIENTS AND METHODS

48 children aged more than 5 were randomly allocated to one of the 2 groups: N2O group, breathed 50% N2O + 50% O2 than received propofol only and Lido group breathed 100% O2 and received a mixture of propofol with lidocaine. The possible pain was scored during injection by a behavioural scale and once again in the recovery room by the child himself with a VAS.

RESULTS

There was no significant difference in behavioural pain scores among the 2 groups; pain was assessed as being moderate or severe in 6/24 patients in N2O group and 10/24 in Lido group (behavioural scores > 1). Significantly more children in the N2O group had low VAS scores compared with the Lido group (no child/24 scored a VAS > 4 and 7/23 in the Lido group) demonstrating that N2O amnesic effects would omit the memory of pain caused by propofol.

CONCLUSION

The use of nitrous oxide is an easy, cheap and efficient method to reduce the incidence of pain injection of propofol and his amnesic effects can provide real advantages in paediatric anaesthesia.

The effect of preoperative epidural morphine on postoperative analgesia in children

IMPLICATIONS

We examined the effects of preoperative epidural morphine associated with general anesthesia on postoperative morphine requirements. Twenty-one children older than 6 yr scheduled for major surgery were randomly assigned to two groups, a control group and an epidural group that received a single epidural morphine injection.

Comparison of recovery after intermediate duration of anaesthesia with sevoflurane and isoflurane

BACKGROUND

The purpose of this study was to compare recovery from anaesthesia after sevoflurane and isoflurane were administered to children for more than 90 min.

METHODS

After parental informed consent and ethical committee approval, children aged between 2 months and 6 years, ASA I or II, were randomly allocated to sevoflurane (n=20) or isoflurane (n=20) groups. Halogenated agents were discontinued following skin closure and patients were ventilated mechanically with 100% oxygen until minimum alveolar concentration (MAC) values awake were obtained (endtidal concentrations 0.6 MAC for sevoflurane and 0.4 MAC for isoflurane). Effective perioperative analgesia was provided by a caudal block.

RESULTS

The mean (+/- SD) duration of anaesthesia was 132 +/- 38 min and 139 +/- 49 min for sevoflurane and isoflurane, respectively. Early recovery occurred sooner in the isoflurane group (time to extubation was 16 +/- 7 min and 11 +/- 5 min, P<0.01; Aldrete's score at 0 min was 5.5 +/- 1.5 and 7.4 +/- 1.8, P<0.001, respectively). But the time to be fit for discharge from recovery room was similar at 136 +/- 18 min and 140 +/- 20 min, respectively.

CONCLUSIONS

After intermediate duration of anaesthesia administered to children for up to 90 min, isoflurane and sevoflurane allow recovery after approximatively the same lapse of time.

Accuracy and limitations of continuous oesophageal aortic blood flow measurement during general anaesthesia for children: comparison with transcutaneous echography-Doppler

BACKGROUND

Because it is noninvasive and easy to use, oesophageal Doppler ultrasonography appears to be a worthwhile alternative for continuous assessment of cardiac output measurement during anaesthesia. A new oesophageal Doppler-echography device (Dynemo 3000, Sometec, Paris, France) can simultaneously determine aortic diameter and aortic blood flow at the same anatomical level (DEeso). The purpose of this study was to assess the accuracy and the potential limitations of this device during general anaesthesia among 20 children, using transcutaneous Doppler-echocardiography for comparison (DEtra).

METHODS

The reproducibility of paired measurements of mean aortic blood flow velocity (MAFV), aortic diameter (ØAo) and aortic blood flow (ABF) was analysed with both methods. Second, haemodynamic values were measured simultaneously in a blinded manner by both methods before and after surgery.

RESULTS

The percent change (%Delta) in MAFV and ABF was calculated with both methods for each child. The age and weight of children included in this study was 8.3 +/- 2.5 years and 27 +/- 8 kg, respectively. Intraoperator reproducibility of MAFVtra, ABFtra, MAFVeso and ABFeso, was 5.0 +/- 4.1%, 7.0 +/- 5.6%, 20.1 +/- 17.5% and 22.0 +/- 16.6%, respectively. ABFtra was significantly linked to ABFeso (R=0.55, P < 0.01). Bias +/- SD of ABF measurements between both methods was 2.2 +/- 1.1 l. min-1. %DeltaABFtra was significantly linked to %DeltaABFeso (R=0.62, P < 0.01). The bias +/- SD inherent to %DeltaABF measurements with both methods was -0.02 +/- 18%.

CONCLUSION

These results suggest that this new oesophageal Doppler method is unsuitable to measure accurately absolute CO values and relative CO changes in children during anaesthesia.

Patent ductus arteriosus and cystic periventricular leucomalacia in preterm infants

AIM

To test the association between early disturbances in hemodynamics induced by left-to-right shunting through the duct and cystic periventricular leucomalacia.

PATIENTS

Forty-six preterm infants (27-32 wk) admitted to the neonatal intensive care unit with risk criteria.

METHODS

Patent ductus arteriosus was evaluated on days 1 and 4, and was significant (sPDA) in cases of absent or reversed end diastolic flow in the subductal aorta. Resistance index was measured in the anterior cerebral artery and in the subductal aorta.

MAIN OUTCOME

Diagnosis of cystic periventricular leucomalacia between day 10 and day 50.

RESULTS

The 12 infants who developed cystic periventricular leucomalacia were compared with those who did not. On day 1, sPDA was more frequent (64% vs 26%; p = 0.03) in the cystic periventricular leucomalacia group, left ventricular output was higher (median = 341 vs 279 ml kg-1.min-1; p = 0.005), and rescue surfactant was more frequently used (83% vs 47%; p = 0.03). This latter association was confirmed by multivariate analysis. Resistance index in the anterior cerebral artery was increased in cases of significant patent ductus arteriosus (p < 0.01) and was correlated with resistance index in the subductal aorta.

CONCLUSION

On day 1 in this selected population, sPDA has an effect on blood flow velocity waveform in cerebral arteries and is associated with an increase in the emergence of cystic periventricular leucomalacia. This association could be casual rather than causal.

[Syringomyelia discovered in the course of peridural anesthesia]

Neurological symptoms after epidural anaesthesia suggest complications due to anaesthetic procedure. We report the case of a child who underwent perineal surgery in a gynaecological position under general and epidural anaesthesia, who experienced the day after surgery hypoesthesia of the whole left lower limb without any motor deficit. Magnetic resonance imaging excluded spinal compression, but revealed syringomyelic cavity extending from T9 to T11. Electromyogram evaluation was normal. Clinical signs completely vanished within 24 hours. This case emphasizes that the apparition of neurological signs after central nerve blocks is not only a complication of regional anaesthesia, but may reveal unknown neuropathy or result from surgical position or surgical procedure. Meticulous neurological examination, magnetic resonance imaging and electromyogram are immediately required.

Axillary block in children: single or multiple injection?

The goal of this double-blind prospective study was to compare the effect of a single injection versus multiple fractionated doses on the onset time and quality of motor and sensory block, obtained in 70 children anaesthetized with axillary block alone. The brachial plexus was identified with a peripheral nerve stimulator, and blocked with 0.5 ml.kg-1 of 1.5% lignocaine with adrenaline. In Group S (single injection), the total volume was injected after location of one nerve. In Group M (multiple fractionated doses), two nerves were located, including necessarily one nerve implicated in the surgical territory. Motor and sensory blocks were assessed according to Lanz's scale before surgery by a blinded observer. A block was considered complete if there was no feeling in at least three nerve territories at 30 min. No difference was found between groups for motor and sensory block quality. However the onset time of the block was faster after multiple fractionated doses (Group M, 25+/-7 min vs Group S, 29+/-4 min) and was faster in younger children (5-9 years: M=23+/-7 min vs S=28+/-5 min, 10-15 years: no difference). There was a significant difference in the quality of the sensory blockade of the musculocutaneous nerve: 18 versus 8 complete blocks, 10 versus 14 incomplete blocks, respectively for Group M versus Group S. No adverse effect was observed and analgesia was prolonged for more than 4 h. We can conclude that, unlike adults, fractionated doses in chilren bring no benefit to the quality of sensory and motor block. Selective block of the musculocutaneous nerve is recommended when a surgical procedure takes place in this territory.

Haematocrit and red blood cell transport in preterm infants: an observational study

AIMS

To test whether cardiac output acts as a compensatory response to changes in haematocrit.

METHODS

A cohort of 38 preterm infants (27-31 weeks' gestation) was studied with repeated Doppler measurements of left ventricular output during the 1st month of life. Red blood cell transport was calculated when the duct was closed.

RESULTS

Multiple regression analysis showed that left ventricular output correlated negatively with haematocrit when the duct was closed (n = 84) and when it was open (n = 59). The influence of an increase of 10% in haematocrit absolute value on mean (SD) left ventricular output was estimated at -55 (11) ml/kg/min. Mean (SD) red blood cell transport was 132 (30) ml/kg/min with a mean (SD) intra-individual variability of 20% (8.8%). Red blood cell transport was increased more frequently by left ventricular output than by haematocrit. Haematocrit and left ventricular output but not red blood cell transport were dependent on postnatal age.

CONCLUSION

These results suggest that in preterm infants cardiac output adaptation is effective in attenuating the effects of red blood cell mass variations on systemic oxygen carrying capacity.

Left ventricle output and mean arterial blood pressure in preterm infants during the 1st day of life

The objective was to assess the contribution of left ventricular output (LVO) in determining low mean arterial blood pressure (MABP) in preterm infants admitted to the neonatal intensive care unit. Doppler echocardiography was prospectively performed on a cohort of 17 consecutive infants with low MABP (<30 mmHg) and on 17 consecutive control subjects (range: 600-1520 g; 27-30.7 weeks gestation). The median haematocrit was 42.5% in the low MABP group versus 49.4% in the control group (P < 0.01). The index of resistance to the LVO (RILV = MABP:LVO ratio) was lower in the low MABP group (98 vs 156 mmHg x l(-1) x kg(-1) x min(-1); P < 0.05). An analysis of the low MABP group regarding LVO revealed that a subgroup of four infants had LVO <10th percentile (185 ml x kg(-1) x min(-1)) with a high RILV (>90th percentile: 226 mmHg x l(-1) x kg(-1) x min(-1)) for three of the infants. The remaining 13 infants had LVO >10th percentile and a shortening fraction >25th percentile. In this subgroup, a high proportion of infants (9/13 vs 2/17, P < 0.01) had low RILV (<10th percentile: 96 mmHg x l(-1) x kg(-1) x min(-1) and the incidence of haemodynamically significant patent ductus arteriosus was higher than in the control group (10/13 vs 4/17, P < 0.01).

CONCLUSION

Left ventricular output, index of resistance to left ventricular output and patent ductus arteriosus status are important to consider in evaluating mean arterial blood pressure during early postnatal life in preterm infants. Low mean arterial blood pressure is frequently associated with normal or high left ventricular output, low index of resistance to left ventricular output and significant patent ductus arteriosus.

Haemodynamic effects of propofol vs thiopental in infants: an echocardiographic study

Rapid i.v. induction of general anaesthesia is indicated in infants at risk of vomiting or regurgitation to reduce the risk of aspiration of gastric contents. Propofol is an alternative to thiopental in infants, and we have compared cardiovascular changes when propofol or thiopental was used for induction of anaesthesia in infants. Twenty infants, ASA I or II, aged 1-11 months, undergoing elective surgery were allocated randomly to receive either thiopental or propofol for i.v. induction. Cardiovascular and echocardiographic data were recorded in both groups before, during and for 5 min after induction of anaesthesia. Doses required to induce anaesthesia in each group were mean 10.3 (SD 0.9) mg kg-1 of thiopental and 6.1 (0.6) mg kg-1 of propofol. Thiopental did not alter significantly systolic or mean arterial pressure, afterload indices, rate-corrected velocity of circumferential fibre shortening or cardiac index, but decreased shortening fraction at 1 and 5 min after induction compared with awake values. Propofol did not alter heart rate, shortening fraction, rate-corrected velocity of circumferential fibre shortening or cardiac index at 1 and 5 min after i.v. induction compared with awake values. After induction, systolic and mean arterial pressures and afterload indices decreased more after induction with both agents, but did not become abnormal. Thus propofol decreased arterial pressure more than thiopental because of an effect on afterload. Cardiac output remained unchanged with both agents.

[Sever acute pulmonary edema after peri-anesthetic laryngospasm in a newborn infant]

Severe acute pulmonary oedema following peranaesthetic laryngospasm in a newborn. The authors report a case of severe acute pulmonary oedema secondary to a laryngeal spasm in a 3-week-old neonate, immediately after induction of anaesthesia with halothane. After emergency tracheal intubation, the infant experienced a severe, life-threatening pulmonary oedema requiring prolonged intensive care. Such a secondary time course is unusual. Usually pulmonary oedema has a favourable outcome after oxygen administration and maintenance of positive expiration pressure, except in the neonate.

[Comparative hemodynamic effects of sevoflurane and halothane at tele-expiratory concentration in intubation of infants]

OBJECTIVE

To compare the cardiovascular changes at the end-tidal concentrations of sevoflurane versus halothane required for tracheal intubation in infants (intubation MAC).

STUDY DESIGN

Prospective randomized study.

PATIENTS

Thirty-two infants, ASA physical status 1 or 2, scheduled for elective surgery, randomized to receive either halothane or sevoflurane for anaesthetic induction by inhalation.

METHODS

Cardiovascular and echocardiographic data were recorded in both groups at baseline, and at the end-tidal concentrations needed for intubation.

RESULTS

Intubation MAC was significantly less with sevoflurane than with halothane in infants. Sevoflurane did not change heart rate (HR) and cardiac index (CI) compared to values when awake. Sevoflurane significantly decreased blood pressure, systemic vascular resistance (SVR) and shortening fraction (SF). Myocardial contractility assessed by stress-velocity index (SVI) and stress-shortening index (SSI) decreased significantly at the intubation MAC, but did not fall into the abnormal range. Halothane caused a greater decrease in HR, SF, SSI, and CI than sevoflurane.

CONCLUSIONS

Sevoflurane decreases cardiac output less than halothane in infants at the intubation MAC, due to a lower end-tidal concentration at intubation MAC and to less effects on haemodynamic variables.

Capillary refilling time and hemodynamics in neonates: a Doppler echocardiographic evaluation

OBJECTIVE

To evaluate the correlation of the capillary refilling time measured in neonates with the hemodynamic parameters obtained by Doppler echocardiography.

DESIGN

Prospective study.

SETTING

Neonatal intensive care unit (ICU) in a university hospital.

PATIENTS

Neonates without congenital cardiac disease admitted to the neonatal ICU (n = 100).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The clinical parameters obtained were: heart rate; blood pressure; mean airway pressure; cutaneous temperature; and capillary refilling time. The echocardiographic data included the measurement of aortic diameter, left atrial diameter, and shortening fraction. Pulsed-Doppler echocardiography was used to measure flow velocity values in the ascending aorta, in the pulmonary artery trunk, and in the patent ductus arteriosus. Cardiac index was calculated secondarily from the volumetric equation, including measured flow velocity in the ascending aorta, aortic diameter, and body weight. Shunt severity at this level was measured by analysis of the descending aortic flow. Thereafter, three groups were defined for analysis: group 1 with obliterated ductus arteriosus; group 2 with patent ductus arteriosus without a retrograde flow in the subdiaphragmatic aorta; and group 3 with patent ductus arteriosus and a retrograde flow in the subdiaphragmatic aorta. There was no correlation between the capillary refilling time and the following parameters: shortening fraction; mean airway pressure; body weight; left atrial diameter/ aortic diameter ratio; blood pressure; and heart rate. In group 1, the capillary refilling time was significantly linked to cardiac index (r2 = .54, p < .001). A lower correlation coefficient between capillary refilling time and cardiac index was found in groups 2 (r2 =.31, p < .001) and 3 (r2 =.41, p < .001).

CONCLUSION

The capillary refilling time was significantly linked to cardiac index in neonates.

Effects of volume expansion on cardiac output in the preterm infant

Clinical and echocardiographic haemodynamic evaluations of response to volume expansion are described in 12 preterm neonates aged < 7 days presenting without cardiac dysfunction and with a low cardiac output. They received 10% albumin solution (20 ml kg-1) for 3 h. Measurements were made before infusion, at volumes 5, 12.5 and 20 ml kg-1 and 1 h later. All infants increased significantly their cardiac output (CO) (from a median of 177 to 283 ml kg-1 min-1). The rise of CO decreased with the volume infused. The index of systemic vascular resistance (SVR = ratio of mean arterial pressure to the CO) decreased for the six patients without PDA (from 272 to 193 mmHg l-1 kg-1 min-1, p < 0.05) showing that the hypovolaemic preterm infant is able to shut down peripherally in response to hypovolaemia. The four hypotensive infants responded by increasing mean arterial blood pressure (from 29 to 44 mmHg). Cutaneous refilling time decreased during infusion (from 6.7 to 3.8 s. p < 0.01). One infant had an haemodynamically significant ductus arteriosus revealed by volume expansion, another one developed myocardial dysfunction.

Comparative hemodynamic depression of sevoflurane versus halothane in infants: an echocardiographic study

BACKGROUND

The cardiovascular side effects of volatile anesthetics are one of the chief causes of postoperative complications in children, and infants seem to be at the greatest risk for this. This study compared cardiovascular changes at equipotent concentrations of sevoflurane and halothane in infants.

METHODS

Thirty infants classified as American Society of Anesthesiologists physical status I or II who required elective surgery were randomized to receive either halothane or sevoflurane for inhalation induction. Cardiovascular and echocardiographic data were recorded in both groups at baseline and at end-tidal concentrations of 1 and 1.5 minimum alveolar concentration (MAC).

RESULTS

Sevoflurane did not alter heart rate or cardiac index at all concentrations compared with awake values. Sevoflurane significantly decreased blood pressure and systemic vascular resistance compared with awake values at all concentrations. Shortening fraction and rate-corrected velocity of circumferential fiber shortening decreased at 1.5 but not at 1 MAC. Myocardial contractility assessed by stress-velocity index and stress-shortening index decreased significantly at all concentrations, but did not fall into the abnormal range at any concentration. Halothane caused a greater decrease in heart rate, shortening fraction, stress-shortening index, velocity of circumferential fiber shortening, stress-velocity index, and cardiac index at all concentrations than did sevoflurane.

CONCLUSION

Sevoflurane causes a lesser decrease in cardiac output than does halothane in infants.

[Analgesia controlled by the patient in pediatrics]

The development of patient controlled analgesia (PCA) in children is the result of a search for an analgesia being both maximally efficient and secure, in the management of severe pain. The technique is based on self infusions of an analgesic, mainly morphine, by the child, through a special pump. The quality of the pump is essential in order to exclude any risk of overdosage. In order to prevent potential secondary effects and complications, a careful supervision is mandatory (clinical, by pulse oximetry, regular checking of pump parameters). PCA is applicable to children older than 5 years. The main indications are post-operative and oncological pains.

[Influence of surfactants on hemodynamics during neonatal respiratory distress syndrome]

The neonatal respiratory distress syndrome tends to delay the circulatory adaptation to extra-uterine life and leads to systematic hypotension. Haemodynamic changes following the instillation of surfactant are not stereotyped. They depend on the type of surfactant, the time of the instillation, the degree of prematurity, the severity of the respiratory disease and the mode of instillation. They are characterized by a transient haemodynamic instability with variable consequences on arterial pressure and systemic blood flow. The use of surfactant tends to decrease pulmonary arterial resistances and pulmonary arterial pressures but this effect is variable and is not obviously accompanied by long-term deleterious effect on the arterial duct. Haemodynamics and blood gases changes due to surfactant instillation have a variable effect on cerebral blood flow. The potential role of blood gas and haemodynamics changes on the occurrence of pulmonary haemorrhage or cerebral damage following instillation of surfactant remains poorly established but has to be taken into account.

[Spontaneous colonic perforations revealing Ehlers-Danlos syndrome type IV]

BACKGROUND

The malignant form of Ehlers-Danlos syndrome type IV owes its bad reputation to a proneness to spontaneous rupture of bowel or large vessels, which may reveal the disease.

CASE REPORT

A girl suffered acute rupture of the sigmoid at the age of 5 years and rupture of the left colon, twice, at the age of 11 and 13 years, respectively. These ruptures required colostomy and finally colectomy. A proneness to bruisability, history of dislocation of hips, hypermobile joints, ovarian cysts and some minor abnormalities of her face resembled that of the Ehlers-Danlos syndrome which was confirmed by optic and electronic microscopy of the skin biopsy.

CONCLUSION

This is the youngest case of rupture of bowel reported in Ehlers-Danlos syndrome. Long-term prognosis is influenced by repetition of intestinal ruptures and occurrence of vascular complications.

Halothane-induced cytotoxicity to rat centrilobular hepatocytes in primary culture is not increased under low oxygen concentration

BACKGROUND

Halothane can be metabolized by both oxidative and reductive pathways in the liver. This anesthetic can induce direct liver injury preferentially localized in centrilobular areas, probably in relation with lower oxygen tension. The reductive pathway has been related to liver damage; however, a correlation between lower oxygen concentration in centrilobular areas, the extent of reductive metabolism of halothane, and the degree of liver injury has not yet been demonstrated. This study was designed to better evaluate the toxicity of the reduced metabolites by using centrilobular and periportal rat hepatocyte subpopulations.

METHODS

Adult rat hepatocytes, either as whole cell preparations or after separation in centrilobular and periportal cell subpopulations, were placed in primary culture and exposed to either 2% or 4% halothane under various oxygen concentrations. The enriched centrilobular hepatocyte subpopulations isolated by the digitonin-collagenase method were characterized by immunolocalization of glutamine synthetase. Three oxygen concentrations were tested: 5%, 20%, and 95%, and the main parameters measured were cell viability and fluoride ion formation.

RESULTS

Viability of centrilobular hepatocytes was similar under 5% and 20% O2, but the unpurified hepatocyte population was more susceptible to 5% O2 (P < 0.01). Significantly higher cytochrome P-450 content was found in whole hepatocyte populations under 5% versus 20% oxygen, indicating that centrilobular hepatocytes that contained higher cytochrome P-450 monooxygenase activities were less sensitive to low oxygen concentrations. Halothane toxicity to centrilobular hepatocytes was enhanced under 95% versus 20% O2 (P < 0.05). By contrast, no significant difference was observed when the cells were maintained under 5% O2, although fluoride ions, indicative of reductive metabolism of halothane, were found in much higher amounts in the culture medium. Moreover, under 20% O2, halothane toxicity was significantly greater in centrilobular versus unpurified hepatocytes (P < 0.05).

CONCLUSIONS

Isolated centrilobular hepatocytes appear to be more sensitive to halothane than their periportal counterparts in vitro. However, the authors' results support the conclusion that increased reductive metabolism of halothane induced by decreasing oxygen concentration is not a critical parameter for the occurrence of liver damage in these cells.