Total intravenous anesthesia for infants and children undergoing correction of tetralogy of Fallot: sufentanil versus sufentanil-flunitrazepam technique

[Total intravenous anesthesia. On the way to standard practice in pediatrics]

Since venous cannulation in children has become easier and extensive experience has been gained with total intravenous anaesthesia (TIVA) in adults, the interest in TIVA for children has recently increased. An intensified sensitivity of the operating room atmosphere to contamination with volatile anaesthetic agents is another important reason to choose intravenous techniques for paediatric anaesthesia. One of the most interesting agents for TIVA in paediatric anaesthesia is propofol. The pharmacokinetic and pharmacodynamic data for modern intravenous drugs is poor. Because the interpatient variability is relatively large, pharmacokinetic data can only provide guidelines for the dosage of propofol. Propofol has a rapid and smooth onset of action and is as easy to titrate in children as in adults. Propofol can be excellently controlled. Severe haemodynamic side-effects are missing in healthy children and plasma is cleared rapidly of propofol by redistribution and metabolism. There is no evidence of significant accumulation, not even after prolonged infusion times. Because propofol has no analgetic properties it must be combined with analgetics or a regional block for all painful procedures. The combination with the ultra-short acting remifentanil is a major advantage, but requires effective analgetic concepts for painful procedures. In comparison the combination of propofol with long acting opioids abolishes some of the favourable properties of propofol. Further studies of the kinetics and dynamics of propofol and other intravenous agents are needed in paediatrics which should focus on age, maturity and severity of illness. The whole importance of the propofol-infusion syndrome has to be cleared up urgently. TIVA has an important significance in paediatric anaesthesia for diagnostic and therapeutic procedures, especially where these have to be repeated. In day-case anaesthesia TIVA has advantages for all short procedures and for ENT and ophthalmic surgery: even after prolonged infusion children have an short recovery time. There is no evidence of agitation or other behavioural disorders after TIVA with propofol in paediatric anaesthesia. Propofol has anti-emetic properties. TIVA with propofol can be combined with regional anaesthesia advantageously to provide long-lasting analgesia after surgery. TIVA with propofol has been used successfully for sedation of spontaneously breathing children for MRI and CT and other procedures with open airways like bronchoscopy or endoscopy. Propofol facilitates endotracheal intubation without the use of muscle relaxants. Of course, in malignant hyperthermia TIVA will continue to be the technique of choice. Nothing is known about awareness under TIVA in paediatric patients. TIVA must be considered by comparison with the volatile agents. The use of ultra-short acting agents may cause problems such as awareness, vagal response, involuntary movements and in some cases slow recovery after prolonged infusion of propofol. But it is not known exactly how often this happens during paediatric anaesthesia. With TIVA an effective postoperative analgesia must be provided. Newer administration techniques such as the target-controlled infusions or closed-loop control systems are under development and will help to minimise the potential risk of overdosage with TIVA in paediatrics. At the present TIVA is an interesting and practicable alternative to volatile anaesthesia for pre-school and school children. TIVA with propofol in infants younger than 1 year old requires extensive experience with TIVA in older children and with the handling of this special age group and should be undertaken with maximum precautionary measures.

Intrathecal versus IV fentanyl in pediatric cardiac anesthesia

Systemic large-dose opioids are widely used in pediatric cardiac anesthesia, but there are no randomized, prospective studies regarding the use of intrathecal (IT) opioids for these procedures. In this randomized, prospective study, we compared cardiovascular and neurohumoral responses during IT or IV fentanyl anesthesia for pediatric cardiac surgery. Thirty children aged 6 mo to 6 yr were anesthetized with an IV fentanyl bolus of 10 micro g/kg. This was followed by a fentanyl infusion of 10 micro g. kg(-1). h(-1) (Group IV; n = 10), 2 micro g/kg of IT fentanyl (Group IT; n = 10), or combined IV and IT protocols (Group IV + IT; n = 10). Heart rate, mean arterial blood pressure, additional fentanyl doses, time to first analgesic requirement, COMFORT and Children's Hospital of Eastern Ontario Pain Scale scores, and extubation time were recorded. Blood cortisol, insulin, glucose, and lactate levels were measured presurgery, poststernotomy, during the rewarming phase of cardiopulmonary bypass (CPB), and 6 and 24 h after surgery. The patients' urinary cortisol excretion rates were also measured during the first postoperative day. The findings in all three groups were statistically similar, except for higher blood glucose levels during CPB in Group IT compared with Group IV (P < 0.004). Group IV + IT was the only group in which the increases in heart rate and mean arterial blood pressure from presurgery to poststernotomy were not significant. The 24-h urinary cortisol excretion rates ( micro g. kg(-1). d(-1)) were 61.51 +/- 39, 92.54 +/- 67.55, and 40.15 +/- 29.69 for Groups IV, IT, and IV + IT, respectively (P > 0.05). A single IT injection of fentanyl 2 micro g/kg offers no advantage over systemic fentanyl (10 micro g/kg bolus and 10 micro g. kg(-1). h(-1)) with regard to hemodynamic stability or suppression of stress response. The combination of these two regimens may provide better hemodynamic stability during the pre-CPB period and may be associated with a decreased 24-h urinary cortisol excretion rate.

IMPLICATIONS

In this prospective, randomized study, we investigated the adequacy of a single intrathecal injection of fentanyl for intraoperative analgesia, compared the effects of IT and IV fentanyl on stress response, and assessed for an additive effect of IT and IV fentanyl administration in pediatric cardiac anesthesia. The results with these three different anesthetic regimens were similar regarding anesthesia depth and level of stress response. However, the combination of IT and IV routes may provide better hemodynamic stability and a less pronounced stress response, as reflected by 24-h urinary cortisol excretion.

Stress response in infants undergoing cardiac surgery: a randomized study of fentanyl bolus, fentanyl infusion, and fentanyl-midazolam infusion

There have been significant changes in the management of neonates and infants undergoing cardiac surgery in the past decade. We have evaluated in this prospective, randomized, double-blinded study the effect of large-dose fentanyl anesthesia, with or without midazolam, on stress responses and outcome. Forty-five patients < 6 mo of age received bolus fentanyl (Group 1), fentanyl by continuous infusion (Group 2), or fentanyl-midazolam infusion (Group 3). Epinephrine, norepinephrine, cortisol, adrenocortical hormone, glucose, and lactate were measured after the induction (T1), after sternotomy (T2), 15 min after initiating cardiopulmonary bypass (T3), at the end of surgery (T4), and after 24 h in the intensive care unit (T5). Plasma fentanyl concentrations were obtained at all time points except at T5. Within each group epinephrine, norepinephrine, cortisol, glucose and lactate levels were significantly larger at T4 (P values < 0.01), but there were no differences among groups. Within groups, fentanyl levels were significantly larger in Groups 2 and 3 (P < 0.001) at T4, and among groups, the fentanyl level was larger only at T2 in Group 1 compared with Groups 2 and 3 (P < 0.006). There were no deaths or postoperative complications, and no significant differences in duration of mechanical ventilation or intensive care unit or hospital stay. Fentanyl dosing strategies, with or without midazolam, do not prevent a hormonal or metabolic stress response in infants undergoing cardiac surgery.

IMPLICATIONS

We demonstrated a significant endocrine stress response in infants with well compensated congenital cardiac disease undergoing cardiac surgery, but without adverse postoperative outcome. The use of large-dose fentanyl, with or without midazolam, with the intention of providing "stress free" anesthesia, does not appear to be an important determinant of early postoperative outcome.