Prolonged administration of isoflurane to pediatric patients during mechanical ventilation

TIVA versus Inhalational Agents for Pediatric Cardiac Intensive Care

The field of pediatric intensive care has come a long way, especially with the recognition that adequate sedation and analgesia form an imperative cornerstone of patient management. With various drugs available for the same, the debate continues as to which is the better: total intravenous anesthesia (TIVA) or inhalational agents. While each have their own advantages and disadvantages, in the present era of balance toward the IV agents, we should not forget the edge our volatile agents (VAs) might have in special scenarios. And ultimately as anesthesiologists, let us not forget that be it knob and dial, or syringe and plunger, our aim is to put pain to sleep and awaken a new faith to breathe.

Long-Term Inhalative Sedation in Children With Pulmonary Diseases

OBJECTIVES

To describe safety and feasibility of long-term inhalative sedation (LTIS) in children with severe respiratory diseases compared to patients with normal lung function with respect to recent studies that showed beneficial effects in adult patients with acute respiratory distress syndrome (ARDS).

DESIGN

Single-center retrospective study.

SETTING

12-bed pediatric intensive care unit (PICU) in a tertiary-care academic medical center in Germany.

PATIENTS

All patients treated in our PICU with LTIS using the AnaConDa® device between July 2011 and July 2019.

MEASUREMENTS AND MAIN RESULTS

Thirty-seven courses of LTIS in 29 patients were analyzed. LTIS was feasible in both groups, but concomitant intravenous sedatives could be reduced more rapidly in children with lung diseases. Cardiocirculatory depression requiring vasopressors was observed in all patients. However, severe side effects only rarely occured.

CONCLUSIONS

In this largest cohort of children treated with LTIS reported so far, LTIS was feasible even in children with severely impaired lung function. From our data, a prospective trial on the use of LTIS in children with ARDS seems justified. However, a thorough monitoring of cardiocirculatory side effects is mandatory.

Targeted Versus Continuous Delivery of Volatile Anesthetics During Cholinergic Bronchoconstriction

Volatile anesthetics have been shown to reduce lung resistance through dilation of constricted airways. In this study, we hypothesized that that diffusion of inhaled anesthetics from airway lumen to smooth muscle would yield significant bronchodilation in vivo, and systemic recirculation would not be necessary to reduce lung resistance (RL ) and elastance (EL ) during sustained bronchoconstriction. To test this hypothesis, we designed a delivery system for precise timing of inhaled volatile anesthetics during the course of a positive pressure breath. We compared changes in RL , EL , and anatomic dead space (VD ) in canines (N=5) during pharmacologically-induced bronchoconstriction with intravenous methacholine, and following treatments with: 1) targeted anesthetic delivery to VD ; and 2) continuous anesthetic delivery throughout inspiration. Both sevoflurane and isoflurane were used during each delivery regimen. Compared to continuous delivery, targeted delivery resulted in significantly lower doses of delivered anesthetic and decreased end-expiratory concentrations. However, we did not detect significant reductions in RL or EL for either anesthetic delivery regimen. This lack of response may have resulted from an insufficient dose of the anesthetic to cause bronchodilation, or from the preferential distribution of air flow with inhaled anesthetic delivery to less constricted, unobstructed regions of the lung, thereby enhancing airway heterogeneity and increasing apparent RL and EL .

An Unusual Complication With the Administration of a Volatile Anesthetic Agent for Status Asthmaticus in the Pediatric Intensive Care Unit: Case Report and Review of the Literature

In severe cases of status asthmaticus, when conventional therapies fail, volatile anesthetic agents remain a therapeutic option. When delivered outside of the operating room setting, specialized delivery techniques are needed to ensure the safe and effective use of volatile anesthetic agents. We present a 16-year-old adolescent with status asthmaticus who required the therapeutic administration of the volatile anesthetic agent, sevoflurane, in the pediatric intensive care unit (PICU). Although initially effective in reducing bronchospasm, progressive hypercarbia developed due to defective functioning of the carbon dioxide absorber of the anesthesia machine. This failure occurred as the soda lime compartment filled with water accumulated from circuit humidification and continuous albuterol therapy. The role of volatile anesthetic agents in the treatment of status asthmaticus in the PICU is discussed, options for delivery outside of the operating room presented, and potential problems with delivery reviewed.

Sevoflurane Therapy for Severe Refractory Bronchospasm in Children

OBJECTIVES

To describe the effect of inhaled sevoflurane in the treatment of severe refractory bronchospasm in children.

DESIGN

Retrospective case series.

SETTING

Two PICUs of tertiary general university hospitals in Spain.

PATIENTS

Ten patients ranging from 5 months to 14 years old with severe bronchospasm and acute respiratory failure requiring tracheal intubation and mechanical ventilation and treated with sevoflurane from 2008 to 2015.

INTERVENTION

Inhaled sevoflurane therapy was initiated after failure of conventional medical management and mechanical ventilation. In two patients, sevoflurane was administered through a Servo 900C ventilator (Maquet, Bridgewater, NJ) equipped with a vaporizer and in the other eight patients via the Anesthetic Conserving Device (AnaConDa; Sedana medical, Uppsala, Sweden) with a critical care ventilator.

MEASUREMENTS AND MAIN RESULTS

Inhaled sevoflurane resulted in statistically significant decreases of PaCO2 of 34.2 torr (95% CI, 8.3-60), peak inspiratory pressure of 14.3 cm H2O (95% CI, 8.6-19.9), and improvement in pH of 0.17 (0.346-0.002) within 6 hours of administration. Only one patient presented hypotension responsive to volume administration at the beginning of the treatment. All patients could be extubated within a median time of 120 hours (interquartile range, 46-216).

CONCLUSIONS

Inhaled sevoflurane therapy decreases the levels of PaCO2 and peak inspiratory pressure values, and it may be considered as a rescue therapy in patients with life-threatening bronchospasm refractory to conventional therapy.

Bispectral Index Monitoring During the Administration of Neuromuscular Blocking Agents in the Pediatric Intensive Care Unit Patient

Bispectral index (BIS) values were prospectively recorded in pediatric intensive care unit patients receiving continuous infusion of a neuromuscular blocking agent. Sedation was provided by a continuous infusion of midazolam or propofol. The BIS number was recorded by a bedside computer every 10 seconds but was concealed from health care workers. BIS values were recorded for 476 hours (161 893 BIS values) in 12 patients. The BIS number was 50 to 70, 57% of the time; ≤49, 35% of the time; and ≥71, 8% of the time. When supplemental doses of sedatives were administered, the BIS number was >70, 64% of the time; 50 to 70, 31% of the time; and ≤49, 5% of the time. Oversedation was more likely with propofol than midazolam. During the use of neuromuscular blocking agents, oversedation is a common occurrence. Physiologic parameters are not an accurate means of assessing the depth of sedation.

Volatile Agents in Medical and Surgical Intensive Care Units: A Meta-Analysis of Randomized Clinical Trials

OBJECTIVE

To comprehensively assess published randomized peer-reviewed studies related to volatile agents used for sedation in intensive care unit (ICU) settings, with the hypothesis that volatile agents could reduce time to extubation in adult patients.

DESIGN

Systematic review and meta-analysis of randomized trials.

SETTING

Intensive care units.

PARTICIPANTS

Critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The BioMedCentral, PubMed, Embase, and Cochrane Central Register databases of clinical trials were searched systematically for studies on volatile agents used in the ICU setting. Articles were assessed by trained investigators, and divergences were resolved by consensus. Inclusion criteria included random allocation to treatment (volatile agents versus any intravenous comparator, with no restriction on dose or time of administration) in patients requiring mechanical ventilation in the ICU. Twelve studies with 934 patients were included in the meta-analysis. The use of halogenated agents reduced the time to extubation (standardized mean difference = -0.78 [-1.01 to -0.55] hours; p for effect<0.00001; p for heterogeneity = 0.18; I(2) = 32% in 7 studies with 503 patients). Results for time to extubation were confirmed in all subanalyses (eg, medical and surgical patients) and sensitivity analyses. No differences in length of hospital stay, ICU stay, and mortality were recorded.

CONCLUSIONS

In this meta-analysis of randomized trials, volatile anesthetics reduced time to extubation in medical and surgical ICU patients. The results of this study should be confirmed by large and high-quality randomized controlled studies.

Continuous infusion, general anesthesia and other intensive care treatment for uncontrolled status epilepticus

PURPOSE OF REVIEW

To discuss the use of continuous infusions, general anesthesia, hypothermia, and ketogenic diet as treatment for uncontrolled status epilepticus in pediatric patients.

RECENT FINDINGS

Recent studies demonstrate that clinical practitioners have a hierarchy in approach in controlling refractory status epilepticus (RSE) and super-refractory status epilepticus in children. In the acute setting of RSE, midazolam achieves clinical seizure control at a mean of 41 min after starting an infusion. When midazolam has failed to control RSE, the evidence points to barbiturate anesthesia as the next frequently used option. When both midazolam and barbiturates have failed, use of isoflurane or ketamine anesthesia has been tried at a mean of 10 days after RSE onset, although the studies are largely anecdotal. Increasingly, the use of therapeutic hypothermia or ketogenic diet is described as a strategy for super-refractory status epilepticus, and better evidence for their use may become available from ongoing randomized studies.

SUMMARY

Uncontrolled episodes of status epilepticus require intensive care treatment and the literature describes a common pathway of care used by many. However, cases of truly refractory and super-refractory status epilepticus are seen infrequently at any given institution. One strategy to improve the quality of evidence is to develop prospective, national and multinational case registries to determine the range of presentations and causes, efficacy of treatments, and clinical outcomes.

Volatile Anesthetics and the Treatment of Severe Bronchospasm: A Concept of Targeted Delivery

Status asthmaticus (SA) is a severe, refractory form of asthma that can result in rapid respiratory deterioration and death. Treatment of SA with inhaled anesthetics is a potentially life-saving therapy, but remarkably few data are available about its mechanism of action or optimal administration. In this paper, we will review the clinical use of inhaled anesthetics for treatment of SA, the potential mechanisms by which they dilate constricted airways, and the side effects associated with their administration. We will also introduce the concept of 'targeted' delivery of these agents to the conducting airways, a process which may maximize their therapeutic effects while minimizing associated systemic side effects. Such a delivery regimen has the potential to define a rapidly translatable treatment paradigm for this life-threatening disorder.

A case series discussing the anaesthetic management of pregnant patients with brain tumours

Pregnancy may aggravate the natural history of an intracranial tumour, and may even unmask a previously unknown diagnosis. Here we present a series of seven patients who had brain tumours during pregnancy. The aim of this case series is to characterize the current perioperative management and to suggest evidence based guidelines for the anaesthetic management of pregnant females with brain tumours. This is a retrospective study. Information on pregnant patients diagnosed with brain tumours that underwent caesarean section (CS) and/or brain tumour resection from May 2003 through June 2008 was obtained from the Department of General Anaesthesia and the Rose Ella Burkhardt Brain Tumour & Neuro-Oncology Centre (BBTC) at the Cleveland Clinic, OH, USA. The mean age was 34.5 years (range 29-40 years old). Six patients had glioma, two of whom had concomitant craniotomy and CS. Six cases had the tumour in the frontal lobe. Four cases were operated on under general anaesthesia and three underwent awake craniotomy. The neonatal outcomes of the six patients with elective or emergent delivery were six viable infants with normal Apgar scores. Pregnancy was terminated in the 7th patient. In conclusion, good knowledge of the variable anesthetic agents and their effects on the fetus is very important in managing those patients.

Pediatric intensive care treatment of uncontrolled status epilepticus

The critically ill mechanically ventilated child with ongoing seizures that are refractory to any treatment presents a distinct challenge in pediatric neurocritical care. The evidence base from randomized controlled trials on which anti-epileptic drug (AED) strategy should be used is inadequate. This review of refractory and super-refractory status epilepticus summarizes recent pediatric case series regarding definitions, the second-tier AED therapies once initial anticonvulsants have failed, and the experience of high-dose midazolam, barbiturate anesthesia, and volatile anesthetics for uncontrolled status epilepticus.

Isoflurane/nitrous oxide anesthesia and stress-induced procedures enhance neuroapoptosis in intrauterine growth-restricted piglets

PURPOSE

There is compelling evidence that interference of various anesthetics with synaptic functions and stress-provoking procedures during critical periods of brain maturation results in increased neuroapoptotic cell death. The hypothesis is that adverse intrauterine environmental conditions leading to intrauterine growth restriction (IUGR) with altered brain development may result in enhanced susceptibility to developmental anesthetic neurotoxicity.

METHODS

This was a prospective, randomized, blinded animal study performed in a university laboratory involving 20 normal-weight (NW) and 19 IUGR newborn piglets. General inhalation anesthesia with isoflurane and nitrous oxide at clinically comparable dosages were administered for about 10 h. Surgical and monitoring procedures were accompanied by appropriate stage of general anesthesia. Resulting effects on developmental anesthetic and stress-induced neurotoxicity were assessed by estimation of apoptotic rates in untreated piglets and piglets after 10-h general anesthesia with MAC 1.0 isoflurane in 70 % nitrous oxide and 30 % oxygen.

RESULTS

IUGR piglets exposed to different levels of isoflurane inhalation exhibited a significant increased apoptosis rate (TUNEL-positive neuronal cells) compared to NW animals of similar condition (P < 0.05). Cardiovascular and metabolic monitorings revealed similar effects of general anesthesia together with similar effects on brain electrical activity and broadly a similar dose-dependent gradual restriction in brain oxidative metabolism in NW and IUGR piglets.

CONCLUSIONS

There is no indication that the increased rate in neuroapoptosis in IUGR piglets is confounded by additional adverse systemic or organ-specific impairments resulting from administered mixed inhalation anesthesia. Developmental anesthetic and stress-induced neuroapoptosis presumably originated in response to fetal adaptations to adverse conditions during prenatal life and should be considered in clinical interventions on infants having suffered from fetal growth restriction.

Isoflurane for life-threatening bronchospasm: a 15-year single-center experience

BACKGROUND

Children with severe bronchospasm requiring mechanical ventilation may become refractory to conventional therapy. In these critically ill patients, isoflurane is an inhaled anesthetic agent available in some centers to treat bronchospasm. We hypothesized that isoflurane is safe and would lead to improved gas exchange in children with life-threatening bronchospasm refractory to conventional therapy.

METHODS

A retrospective review was conducted and included mechanically ventilated children treated with isoflurane in a quaternary pediatric ICU for life-threatening bronchospasm, from 1993 to 2007. Demographic, blood gas, ventilator, and outcome data were collected.

RESULTS

Thirty-one patients, with a mean age of 9.5 years (range 0.4-23 years) were treated with isoflurane, from 1993 to 2007. Mean time to initiation of isoflurane after intubation was 13 hours (0-120 h), and the mean maximum isoflurane dose was 1.1% (0.3-2.5%). Mean duration of isoflurane administration was 54.5 hours (range 1-181 h), with a total mean duration of mechanical ventilation of 252 hours (range 16-1,444 h). Isoflurane led to significant improvement in pH and P(CO(2)) within 4 hours of initiation (P ≤ .001). Complications during isoflurane administration included hypotension requiring vasoactive infusions in 24 (77%), arrhythmia in 3 (10%), neurologic side effects in 3 (10%), and pneumothorax in 1 (3%) patient.

CONCLUSIONS

Isoflurane led to improvement in pH and P(CO(2)) within 4 hours in this series of mechanically ventilated patients with life-threatening bronchospasm. The majority of patients in this series developed hypotension, but there was a low incidence of other side effects related to isoflurane administration. Isoflurane appears to be an effective therapy in patients with life-threatening bronchospasm refractory to conventional therapy. However, further investigation is warranted, given the uncertain overall impact of isoflurane in this context.

[Anesthetic conserving device (AnaConDa) used after cardiac surgery: experience in a postoperative recovery unit]

OBJECTIVE

To assess the safety and efficacy of using the Anesthetic Conserving Device (AnaConDa) when maintaining sedation after cardiac surgery.

MATERIAL AND METHODS

Descriptive study of 46 consecutive patients in the postoperative recovery unit after cardiac surgery between January and April 2009. The patients were under sevoflurane sedation administered with the AnaConDa placed in the inhalation tube. No exclusion criteria were established before enrollment. The sevoflurane dose was set using the manufacturer's normogram and was later adjusted to give an end-tidal concentration of sevoflurane between 0.5% and 0.7% on the basis of data from a gas analyzer. Remifentanil was administered to all patients; a fast-track extubation protocol was used. The only criterion for excluding a patient's data from analysis was prolonged sedation (> 5 hours).

RESULTS

The mean (SD) time patients were under sedation with the AnaConDa in place was 2588 (12.32) minutes. The end-tidal concentration of sevoflurane never exceeded 1%. Scores on the Richmond agitation-sedation scale were -5 at 60 minutes in all cases; there was some score variability at 120 minutes. Deeper sedation was desired for the first 60 minutes to avoid awakening related to rewarming. The mean time until awakening was 6.17 minutes (range, 1-30 minutes). The mean time until extubation was 43 (6.69) minutes. The most common adverse effect was arterial hypotension (12 cases). Hypotension was related to bleeding in 3 patients and to low cardiac output in 4 patients.

CONCLUSION

Administering sevoflurane through the AnaConDa can be a safe, valid, and reliable method for sedating patients after cardiac surgery. With this device, it is possible to monitor the concentration administered.

Inhalational anesthesia: basic pharmacology, end organ effects, and applications in the treatment of status asthmaticus

The potent inhalational anesthetic agents are used on a daily basis to provide intraoperative anesthesia. Given their beneficial effects on airway tone and reactivity, they also have a role in the treatment of status asthmaticus that is refractory to standard therapy. Although generally not of clinical significance, these agents can affect various physiological functions. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. The following article reviews the history of inhalational anesthesia, the physical structure of the inhalational anesthetic agents, their end-organ effects, reports of their use for the treatment of refractory status asthmaticus in the intensive care unit (ICU) patient, and special considerations for their administration in this setting including equipment for their delivery, scavenging, and monitoring.

Is anesthesia bad for the newborn brain?

Although certain data suggest that common general anesthetics may be neurotoxic to immature animals, there are also data suggesting that these same anesthetics may be neuroprotective against hypoxicischemic injury, and that inadequate analgesia during painful procedures may lead to increased neuronal cell death in animals and long-term behavioral changes in humans. The challenge for the pediatric anesthesia community is to design and implement studies in human infants to ascertain the safety of general anesthesia. In this article, the authors review the relevant preclinical and clinical data that are currently available on this topic.

Efficacy of sedation regimens to facilitate mechanical ventilation in the pediatric intensive care unit: a systematic review

OBJECTIVE

Children admitted to pediatric intensive care units (PICUs) often receive sedatives to facilitate mechanical ventilation. However, despite their widespread use, data supporting appropriate dosing, safety, and optimal regimens for sedation during mechanical ventilation are lacking. Therefore, we conducted a systematic review of published data regarding efficacy of sedation to facilitate mechanical ventilation in PICU patients. Our primary objective was to identify and evaluate the quality of evidence supporting sedatives used in PICUs for this purpose.

DATA SOURCES

We searched MEDLINE, EMBASE, and The Cochrane Registry of Clinical Trials from 1966 to June 2008 to identify published articles evaluating sedation regimens to facilitate mechanical ventilation in PICU patients.

STUDY SELECTION

We included only those studies of intubated PICU or pediatric cardiac intensive care unit patients receiving pharmacologic agents to facilitate mechanical ventilation that reported quality of sedation as an outcome.

DATA EXTRACTION

We analyzed studies separately for study type and by agents being studied. Studies were appraised using criteria of particular importance for reviews evaluating sedatives.

DATA SYNTHESIS

Our search strategy yielded 39 studies, including 3 randomized trials, 15 cohort studies, and 21 cases series or reports. The 39 studies evaluated a total of 39 different sedation regimens, with 21 different scoring systems, in a total of 901 PICU/cardiac intensive care unit patients ranging in age from 3 days to 19 years old. Most of the studies were small (<30 patients), and only four studies compared one or more agents to another. Few studies thoroughly evaluated drug safety, and only one study met all quality criteria.

CONCLUSIONS

Despite the widespread use of sedatives to facilitate mechanical ventilation in the PICU, we found that high-quality evidence to guide clinical practice is still limited. Pediatric randomized, controlled trials with reproducible methods and assessment of drug safety are needed.

[Sedation concepts with volatile anaesthetics in intensive care: practical use and current experiences with the AnaConDa system]

The use of volatile anaesthetics in intensive care medicine has so far been limited by the lack of equipment suitable for daily routine use and the need for an anaesthetic machine. The new Anaesthetic Conserving Device (AnaConDa) enables the routine use of volatile anaesthetics for long-term sedation via intensive care ventilators. The Anaesthetic Conserving Device replaces the common heat and moisture exchanger in the ventilation circuit. The volatile anaesthetic is continuously applied in liquid status via a syringe pump to a form of mini-vaporiser where the anaesthetic agent is vaporised. The expired anaesthetic gas is stored in the carbon filter and approximately 90% of the gas is resupplied into the breathing cycle. The current experiences suggest that volatile anaesthetics present an alternative for long-term sedation in intensive care units, providing optimised pathways, from a medical as well as from an economical point of view. It must, however, be emphasized that the use of volatile anaesthetics for longer periods of time is an off-label use and should only undertaken by medical professionals at their own risk.

Therapeutic applications and uses of inhalational anesthesia in the pediatric intensive care unit

OBJECTIVE

To review the physical properties, end-organ effects, therapeutic applications, and delivery techniques of inhalational anesthetic agents in the pediatric intensive care unit.

DATA SOURCE

A computerized, bibliographic search regarding intensive care unit applications of inhalational anesthetic agents.

MAIN RESULTS

Although the end-organ effects of inhalational anesthetic agents vary depending on the agent, general effects include a dose-related depression of ventilatory and cardiovascular function. With increasing anesthetic depth, there is a decrease in alveolar ventilation with a reduction in tidal volume and an increase in PaCO2 in spontaneously breathing patients. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. Beneficial effects include sedation, amnesia, and anxiolysis, making these agents effective for sedation during mechanical ventilation. Bronchodilatory and anticonvulsant properties have led to their use as therapeutic agents in patients with refractory status asthmaticus and epilepticus. Issues regarding their delivery in the intensive care unit include equipment for their delivery, scavenging, and monitoring.

CONCLUSIONS

The literature contains reports of the therapeutic use of the potent inhalational anesthetic agents in the pediatric intensive care unit. Potential applications include sedation during mechanical ventilation as well as therapeutic use for the treatment of status asthmaticus and epilepticus.

Isoflurane-induced neuroapoptosis in the developing brain of nonhypoglycemic mice

Drugs that suppress neuronal activity, including general anesthetics used in pediatric and obstetric medicine, trigger neuroapoptosis in the developing rodent brain. Exposure of infant rats for 6 hours to a combination of anesthetic drugs (midazolam, nitrous oxide, isoflurane) reportedly causes widespread apoptotic neurodegeneration, followed by lifelong cognitive deficits. Isoflurane, the dominant ingredient in this triple cocktail, has not been evaluated individually for apoptogenic potential. It was recently reported that (1) the minimum alveolar concentration (MAC) for anesthetizing infant mice with isoflurane is 2.26%, and; (2) that infant mice, without assisted respiration, maintain normal arterial oxygen values but become hypoglycemic when exposed to isoflurane 3% for 30 minutes, then 1.8% for 1 hour (1.46 MAC-hours). In the present experiments, infant mice were exposed to isoflurane at various sub-MAC concentrations and durations, and the brains were evaluated quantitatively 5 hours after initiation of anesthesia exposure to determine the number of neuronal profiles undergoing apoptosis. Blood glucose values were also determined under each of these conditions. All conditions tested (isoflurane at 0.75% for 4 h, 1.5% for 2 h, 2.0% for 1 h) triggered a statistically significant increase in neuroapoptosis compared with the rate of spontaneous apoptosis in littermate controls. Blood glucose determinations ruled out hypoglycemia as a potential cause of the brain damage. It is concluded that exposure to sub-MAC concentrations of isoflurane for one or more hours triggers neuroapoptosis in the infant mouse brain. These findings are consistent with other recent evidence demonstrating that brief exposure to ethanol, ketamine, or midazolam triggers neuroapoptosis in the developing mouse brain.

Status asthmaticus in children

PURPOSE OF REVIEW

The prevalence of severe asthma in children has risen in the past few decades. The present review explores our current understanding of epidemiology, pathophysiology and treatment of status asthmaticus in children.

RECENT FINDINGS

The pathophysiology of inflammation and airway hyperactivity continues to be a source of research. Early initiation of inhaled beta-agonists and oral or parenteral steroids remain the standard of care in the treatment of status asthmaticus. Other treatment modalities such as magnesium and intravenous beta-agonists show some benefit. There is a resurgence of interest in the use of methylxanthines. Alternatives to endotracheal intubation show some promise in preventing respiratory failure.

SUMMARY

Asthma remains the third leading cause of hospitalization in children younger than 15 years old. Researchers continue to explore the efficacy of old and new treatment modalities. Future research efforts targeting at-risk populations could dramatically decrease asthma morbidity and mortality.

Cisatracurium in "weakening doses" assists in weaning from sedation and withdrawal following extended use of inhaled isoflurane

OBJECTIVE

Isoflurane was used to treat a patient with status asthmaticus refractive to standard therapeutic measures. The patient developed a significant withdrawal syndrome when the isoflurane was weaned. A case is reported here where this withdrawal syndrome was treated successfully by using a weakening dose neuromuscular blockade with cisatracurium.

DESIGN

Case report.

SETTING

Pediatric critical care unit.

PATIENT

A 4-yr-old girl with severe reactive airways disease.

INTERVENTIONS

The use of weakening doses of cisatracurium to assist in weaning from mechanical ventilation in the setting of withdrawal symptoms following the extended use of inhaled isoflurane.

MEASUREMENTS AND MAIN RESULTS

Despite treatment with mechanical ventilation, intravenous corticosteroids, and bronchodilators for status asthmaticus, the patient required inhaled isoflurane. She became tolerant to isoflurane over an extended period of time; her tolerance was associated with a specific withdrawal syndrome, with the development of choreoathetoid movements resulting in poor pulmonary coordination and agitation. Conventional medical treatment of withdrawal failed. Finally, by using an infusion of cisatracurium at weakening doses to assist in the control of these choreoathetoid movements, the isoflurane and ventilator support were weaned.

CONCLUSIONS

Weakening doses of cisatracurium may be used safely to control unpleasant motor symptoms secondary to tolerance of isoflurane. This may have a use in other circumstances where agitation in mechanically ventilated patients is not due to pain or anxiety.

Three cases of PICU sedation with isoflurane delivered by the 'AnaConDa'

Prolonged sedation in the pediatric intensive care unit may be difficult because of tolerance, drug dependence and withdrawal, drug interactions and unwanted drug effects. We present three patients sedated with isoflurane via the Anesthetic Conserving Device, AnaConDa. AnaConDa is a modified heat and moisture exchanger that allows evaporation and delivery of inhalational anesthetics without an anesthesia machine, vaporizer or adapted ventilator. Two patients with abdominal complications and prolonged sedation for mechanical ventilation were converted to isoflurane sedation for several days. The third patient with refractory status epilepticus received isoflurane to treat epileptiform electroencephalogram activity. Patients weighing 40 and 30 kg were treated with AnaConDa placed at the Y-piece, while the patient weighing 20 kg was treated with AnaConDa in the inspiratory limb of the respiratory circuit. Adequate sedation was achieved with endtidal isoflurane concentration of 0.3-0.4%, while antiepileptic effect was achieved at a higher dose, 0.9%. Intravenous sedatives could be reduced or discontinued during isoflurane sedation. Inhaled sedation of isoflurane with AnaConDa was effective in these patients. It may provide an alternative in difficult cases needing prolonged sedation and should be evaluated further.

Managing sedation withdrawal in children who undergo prolonged PICU admission after discharge to the ward

Children who undergo a prolonged stay within the intensive care unit require adequate sedation and analgesia. During the recovery phase there will need to be a period of sedation withdrawal to prevent occurrence of an abstinence syndrome. We present a strategy developed within our hospital for managing this process which uses the resource of the Pain Service, along with guidelines to help prevent the development of withdrawal, and a plan for managing any signs of abstinence which occur.

Desflurane compared with propofol for postoperative sedation in the intensive care unit

BACKGROUND

We hypothesized that emergence from sedation in postoperative patients in the intensive care unit would be faster and more predictable after sedation with desflurane than with propofol.

METHODS

Sixty patients after major operations were allocated randomly to receive either desflurane or propofol. The target level of sedation was defined by a bispectral index(TM) (BIS(TM)) of 60. All patients were receiving mechanical ventilation of the lungs for 10.6 (SD 5.5) h depending on their clinical state. The study drugs were stopped abruptly in a calm atmosphere with the fresh gas flow set to 6 litres min(-1), and the time until the BIS increased above 75 was measured (t(BIS75), the main objective measure). After extubation of the trachea, when the patients could state their birth date, they were asked to memorize five words.

RESULTS

Emergence times were shorter (P<0.001) after desflurane than after propofol (25th, 50th and 75th percentiles): t(BIS75), 3.0, 4.5 and 5.8 vs 5.2, 7.7 and 10.3 min; time to first response, 3.7, 5.0 and 5.7 vs 6.9, 8.6 and 10.7 min; time to eyes open, 4.7, 5.7 and 8.0 vs 7.3, 10.5 and 20.8 min; time to squeeze hand, 5.1, 6.5 and 10.2 vs 9.2, 11.1 and 21.1 min; time to tracheal extubation, 5.8, 7.7 and 10.0 vs 9.7, 13.5 and 18.9 min; time to saying their birth date, 7.7, 10.5 and 15.5 vs 13.0, 19.4 and 31.8 min. Patients who received desflurane recalled significantly more of the five words. We did not observe major side-effects and there were no haemodynamic or laboratory changes except for a more marked increase in systolic blood pressure after stopping desflurane. Using a low fresh gas flow (air/oxygen 1 litre min(-1)), pure drug costs were lower for desflurane than for propofol (95 vs 171 Euros day(-1)).

CONCLUSIONS

We found shorter and more predictable emergence times and quicker mental recovery after short-term postoperative sedation with desflurane compared with propofol. Desflurane allows precise timing of extubation, shortening the time during which the patient needs very close attention.

Status asthmaticus in children: a review

About 10% of American children have asthma, and its prevalence, morbidity, and mortality have been increasing. Asthma is an inflammatory disease with edema, bronchial constriction, and mucous plugging. Status asthmaticus in children requires aggressive treatment with beta-agonists, anticholinergics, and corticosteroids. Intubation and mechanical ventilation should be avoided if at all possible, as the underlying dynamic hyperinflation will worsen with positive-pressure ventilation. If mechanical ventilation becomes necessary, controlled hypoventilation with low tidal volume and long expiratory time may lessen the risk of barotrauma and hypotension. Unusual and nonestablished therapies for severe asthma are discussed.

Tolerance, withdrawal, and physical dependency after long-term sedation and analgesia of children in the pediatric intensive care unit

OBJECTIVE

To describe the consequences of the prolonged administration of sedative and analgesic agents to the pediatric intensive care unit (PICU) patient. The problems to be investigated include tolerance, physical dependency, and withdrawal.

DATA SOURCES

A MEDLINE search was performed of literature published in the English language. Cross-reference searches were performed using the following terms: sedation, analgesia with PICU, children, physical dependency, withdrawal; tolerance with sedative, analgesics, benzodiazepines, opioids, inhalational anesthetic agents, nitrous oxide, ketamine, barbiturates, propofol, pentobarbital, phenobarbital.

STUDY SELECTION

Studies dealing with the problems of tolerance, physical dependency, and withdrawal in children in the PICU population were selected.

DATA EXTRACTION

All of the above-mentioned studies were reviewed in the current manuscript.

DATA SYNTHESIS

A case by case review is presented, outlining the reported problems of tolerance, physical dependency, and withdrawal after the use of sedative/analgesic agents in the PICU population. This is followed up by a review of the literature discussing current treatment options for these problems.

CONCLUSIONS

Tolerance, physical dependency, and withdrawal can occur after the prolonged administration of any agent used for sedation and analgesia in the PICU population. Important components in the care of such patients include careful observation to identify the occurrence of withdrawal signs and symptoms. Treatment options after prolonged administration of sedative/analgesic agents include slowly tapering the intravenous administration of these agents or, depending on the drug, switching to subcutaneous or oral administration.

Sedation and analgesia in paediatric intensive care units: a guide to drug selection and use

The indications for sedation in the paediatric intensive care unit (PICU) patient are varied ranging from short term use for various procedures to prolonged administration to provide comfort during mechanical ventilation. When faced with the decision to institute sedation, the healthcare provider must make three decisions: the agent to be used, the route of delivery, and the mode of administration (intermittent versus continuous). There are several agents that have been used to provide sedation in the PICU patient including the inhalational anaesthetic agents, benzodiazepines, opioids, ketamine, propofol, chloral hydrate, phenothiazines, and the barbiturates. This review describes the various agents for sedation and discusses their advantages and disadvantages as they pertain to the PICU. Consequences of and treatment strategies for long term problems with prolonged sedation including tolerance, physical dependency, and withdrawal are reviewed.