[Special aspects of pediatric anesthesia in ophthalmic surgery]. / Besondere Aspekte der Kinderanästhesie in der Ophthalmochirurgie.

In ophthalmic surgery, children are anesthetized for various reasons. The airway needs special attention as children have higher oxygen requirements and brief periods of apnea can result in hypoxemia and subsequent bradycardia or even cardiac arrest. Most interventions can be managed with the aid of a laryngeal mask allowing minor airway manipulations and thereby reducing the risk of laryngeal and tracheal injuries and laryngospasm in children with hypersensitive airways. In children older than 3 years an adequate postoperative nausea and vomiting (PONV) prophylaxis should be performed. The modified postoperative vomiting in children (POVOC) score is a suitable method for the estimation of PONV. Strabismus surgery is an independent risk factor for PONV; therefore, prophylaxis is recommended in any case. The combination of drugs from different substance groups amplifies the antiemetic effect. This article discusses whether anesthesia can damage immature brains. In animal experiments it could be proven that neuronal apoptosis could be induced by most of the commonly used anesthetics. It has not yet been clarified whether this has an effect on the neurocognitive development of children. Because of this uncertainty the indications for surgery and anesthesia should be assessed on strict clinical requirements. There is, however, widespread agreement that a necessary anesthesia carried out in a correct and controlled manner has no negative consequences for children.

Observations on the effects of inhaled isoflurane in long-term sedation of critically Ill children using a modified AnaConDa©-system.

Long-term intravenous sedation may present problems due to dependence and side effects. Medical records of children who were administered isoflurane were reviewed. 15 patients (9 boys, 6 girls) with a mean age of 11.8 month (+2.4) were analysed.Analgesia and sedation was given in mean 9.7+1.1 days before commencing inhalation using a modified application device (AnaConDa©). Administration was given over a period of 7.2+1.4 days. Depth of sedation was monitored by using Comfort- and Hartwig-scores. Observations included continuous monitoring of heart-rate, pulse oxymetry, blood pressure and cerebral tissue oxygenation.Within 4 h post administration of isoflurane a satisfactory increase in the depth of sedation was seen and kept till extubation. 6/15 patients received tracheostomies during the observation period. None of the patients observed suffered life-critical events of the modified application of isoflurane proceeded without complications. Ketamine and clonidine infusion rates were significantly reduced (p<0.005) as well as the use and overall infusion rate of midazolam, γ-hydroxy butyrate, fentanyl and morphine (p<0.05).Isoflurane inhalation may provide an additional option for long-term sedation in a specific group of critically ill infants but neurodegenerative toxic effects will have to be taken into account when using volatile anesthetics at any time during infancy.

Device therapy to prevent sudden death in patients with structural heart disease.

The advent of the implantable cardioverter defibrillator has provided clinicians with a potential tool to prevent sudden arrhythmic death. When considering patients with structural heart disease, long-term follow-up data have suggested that this is indeed an important cause of late mortality. It is essential therefore to undertake follow-up studies to identify high risk individuals or disease categories that are associated with sudden cardiac death (SCD), and to elucidate the specific risk factors that may be associated with this complication. We provide a brief update on the current state of knowledge in this challenging and rapidly developing field.

Risk stratification in young patients with channelopathies.

Identifying the young patient at risk of malignant arrhythmias and sudden cardiac death remains a challenge. It is increasingly recognised that sudden death, syncope and aborted cardiac arrest at a young age in patients with a structurally normal heart may be the result of various ion channel disorders - the channelopathies. The approach to risk stratification involves a combination of the clinical presentation, taken in conjunction with the family history, genetic testing, invasive electrophysiological studies or other provocative tests where appropriate and feasible. A logical approach to risk stratification in some of the commoner channelopathies seen in paediatric practice is presented.

Device therapy in children: current indications.

The implantable cardioverter defibrillator has achieved increasing acceptance in paediatric cardiologic practice. Concurrent with technological advances which have made the devices more versatile, easier to implant and to program, there has been a fundamental breakthrough in our understanding of genetic and inherited arrhythmia syndromes in the last decade. This in turn has led to investigations into risk stratification, with the aim of choosing high risk candidates for timely device therapy. The second group of young patients with a risk of sudden death are those who have had a previous repair of a structural heart defect. Given that sudden arrhythmic death is the commonest cause of mortality in this population, it behoves the practising paediatric cardiologist to be aware of the current recommendations for device implantation in this population. In this manuscript, we summarise the current state of our understanding of the risk factors for sudden death, and identify possible candidates for ICD implantation.

Paediatric electrophysiologic studies: how and what with?

Catheter ablation of arrhythmias in children has become standard practice virtually worldwide. Successful and safe ablation has been made possible by a combination of factors. These include increased operator experience, a better understanding of the natural history of a wide variety of arrhythmias, advances in technology such as smaller catheters, the routine use of various three-dimensional mapping systems, and the development of alternative energy sources. It is also not uncommon to perform multiple catheter intervention procedures (ablation +/- intravascular stent implantation +/- device closure of residual shunts +/- elective pacemaker or device implantation) during a single session. It is important to bear in mind that arrhythmia recurrence is commoner in children in general, and that this is particularly the case with postoperative (scar-related arrhythmias). Despite acute success, long-term follow-up is mandated for this subgroup of patients.

Central venous catheters in children and neonates (Part 2) - Access via the internal jugular vein.

Central venous access via the internal jugular vein (IJV) is safe, relatively easy and very commonly used in infants and children undergoing cardiac surgery for congenital heart disease. Because of the wide range of anatomical variations an ultrasound-guided technique is advantageous in many cases, in particular in patients who have had previous punctures or those in whom difficulties are anticipated for various reasons. The right internal jugular vein is the preferred vein for central venous access as it offers straight access to the superior vena cava. The rate of complications - insertion-related as well as long term - are lower compared to the femoral and the subclavian access.

Central venous catheters in children and neonates (Part 3) - Access via the femoral vein.

BACKGROUND: Central venous access via the femoral vein (FV) is safe, relatively easy and very usual in infants and children undergoing cardiac surgery for congenital heart disease. It has a low insertion-related complication rate. RESULTS: It is therefore a good choice for short-term central venous lines and a preferred insertion site for less experienced staff. The maintenance-related complications of thrombus formation and infections are higher compared to the internal jugular and the subclavian venous access. CONCLUSIONS: Some of these complications are reduced by the use of heparin bonded catheters, routine use of antibiotics, and timely removal of these lines in patients with persistent signs of infection but without another focus being defined.

Central venous catheters in children and neonates - what is important?

Central venous access is an essential part of perioperative management for infants and children undergoing cardiac surgery for congenital heart disease. In addition, a thorough knowledge of the techniues for cannulation and placement of venous lines from the various percutaneously accessible sites is an important aspect of cardiac catheterization in this patient population. In the first of a series of papers describing the various approaches to venous access, we describe percutaneous cannulation of the subclavian vein. The standard approach, as well as potential difficulties, and how to overcome them, are described, as also the complications associated with this approach.

Pharmacological modulation of calcium and potassium channels in isolated vascular smooth muscle cells.

Calcium antagonists relax vascular smooth muscle cells (VSM) by decreasing Ca-influx and intracellular Ca-load. In isolated VSM, Ca-influx was measured as Ca-current by the voltage clamp technique applied to a patch of membrane (single-channel current) or to the whole cell (whole-cell current ICa). Gallopamil exerted Ca-antagonism mostly by reducing channel availability, i.e. the probability that the Ca-channel opens upon depolarization. Whole-cell-Ca-currents revealed prominent frequency dependence, i.e. reduction of ICa increased with the number of depolarizations. In addition, the gallopamil effect was voltage-dependent such that depolarized myocytes were more sensitive than hyperpolarized cells. The dihydropyridine nitrendipine abbreviated the life time which the Ca-channel stood in the open state and it hindered the channel to re-open again. Reduction of availability was found only after a prolonged application. In whole cell ICa, nitrendipine accelerated the inactivation time course. The Ca-antagonistic effect was voltage-dependent but not frequency-dependent. Potassium agonists are supposed to activate K-channels thereby hyperpolarizing the membrane, hyperpolarization shuts off the Ca-channels and thereby reduces Ca-influx. The K-agonists cromakalim, (+) niguldipine and diazoxide activated the Ca-dependent maxi K-channel (inside-out patches studied at [Ca2+]c of 50 nmol/l or 500 nmol/l. They increased the open probability mainly by decreasing the long closures between the channel openings. The K-agonists can repolarize the cell once it excited and suppress further excitability.