Extracorporeal Life Support: Four Decades and Counting.

Extracorporeal membrane oxygenation (ECMO) or extracorporeal life support (ECLS) is a form of heart lung bypass that is used to support neonates, pediatrics, and adult patients with cardiorespiratory failure for days or weeks till organ recovery or transplantation. Venoarterial (VA) and venovenous (VV) ECLS are the most common modes of support. ECLS circuit components and monitoring have been evolving over the last 40 years. The technology is safer, simpler, and more durable with fewer complications. The use of neonatal respiratory ECLS use has been declining over the last two decades, while adult respiratory ECLS is growing especially since the H1N1 influenza pandemic in 2009. This review provides an overview of ECLS evolution over the last four decades, its use in neonatal, pediatric and adults, description of basic principles, circuit components, complications, and outcomes as well as a quick look into the future.

Dexmedetomidine for acute baclofen withdrawal.

BACKGROUND: Intrathecal baclofen is widely accepted as a treatment option for severe spasticity through its γ-Aminobutyric acid-B (GABAB ) agonist properties. Abrupt cessation can lead to severe and life-threatening withdrawal characterized by altered mental status, autonomic dysreflexia, rigidity, and seizures. This symptomatic presentation is similar to alcohol withdrawal, which is mediated by modification of GABAA expression. Use of the α2-adrenergic agonist dexmedetomidine for the treatment of ethanol withdrawal has been widely reported, raising the question of its potential role in baclofen withdrawal. We present a case of the successful treatment of acute severe baclofen withdrawal with a dexmedetomidine infusion. METHODS: A 15-year-old patient with spastic quadriparesis and cerebral palsy underwent unexpected removal of his baclofen pump due to an infection that was encountered during a planned pump revision. Following removal, he was placed on high dose enteral baclofen every 6 h. Despite further benzodiazepine supplementation, he had progressive hemodynamic instability, severe rebound spasticity, and intermittent spontaneous clonus consistent with baclofen withdrawal. A dexmedetomidine infusion was titrated to a peak dose of 16 mcg per hour with successful treatment of withdrawal symptoms. RESULTS: The patient became normotensive without tachycardia. Tone and agitation improved. CONCLUSION: Dexmedetomidine is to our knowledge a previously unreported option for treatment of acute severe baclofen withdrawal. We report a case of safe and efficacious use in a patient with spastic quadriparesis on chronic intrathecal baclofen. Scientifically rigorous comparison with other options remains to be performed.

Dexmedetomidine for pediatric MRI sedation: a review of a series of cases.

BACKGROUND: The aim of this review was to determine whether dexmedetomidine alone provided satisfactory conditions for children undergoing magnetice resonance imaging (MRI). METHODS: A retrospective review of 21 patients was undertaken, (age range: 1-8 years, weight 10-27 kg) who received dexmedetomidine to provide deep sedation for an MRI procedure. RESULTS: In the initial eight patients who received dexmedetomidine (bolus 0.5-1.5 mg.kg(-1) and infusion rate 1-1.5 mg.kg(-1).h(-1)) by itself, movement occurred in five of them, even when the maximum suggested dose was used (1 microg.kg(-1).h(-1)). Midazolam (0.1 mg.kg(-1)) i.v. was given as an adjunct to the following 13 patients (dexemdetomidine doses were lower: bolus 1 mg.kg(-1), infusion 0.5-1 mg.kg(-1).h(-1)). Only one patient moved within this group. The mean time to discharge postprocedure was 90 min. There were no differences with respect to recovery or discharge times between those who did or did not receive midazolam. No cardiac or respiratory complications were noted. CONCLUSIONS: The use of dexmedetomidine for MRI sedation by itself was more unpredictable than anticipated from the published case reports of its use.

The effects of isoflurane and desflurane titrated to a bispectral index of 60 on the cortical somatosensory evoked potential during pediatric scoliosis surgery.

In this study, we compared the effect of isoflurane and desflurane on the posterior tibial somatosensory evoked potential recorded by scalp electrodes during correction of idiopathic scoliosis in pediatric patients. Depth of sedation was controlled by maintaining bispectral index (BIS) at 60 throughout the study. Comparison of patients breathing desflurane and isoflurane showed an evoked cortical amplitude (N37-P45) of 0.53 +/- 0.3 microV versus 1.3 +/- 0.8 microV (P = 0.014), respectively. In addition to this comparison, a crossover design was included whereby the desflurane or isoflurane received in the first part of the study was changed to the other anesthetic. Substituting one anesthetic for another confirmed our initial finding that the cortical evoked amplitude is greater with isoflurane than with desflurane. No differential effect was found between desflurane and isoflurane on the evoked subcortical (N31-P34) amplitude or the P37 latency.

The clinical effect of mixing different proportions of rocuronium and mivacurium.

BACKGROUND: A synergistic effect has been described when rocuronium (Roc) and mivacurium (Miv) are combined in equal (i.e. 1:1) ED95 proportions at various total doses. We have investigated the effect of Roc or Miv alone and four different ratios (1:4, 2:3, 3:2 and 4:1) of Roc and Miv mixed to a total dose of 1.33 x ED95. The primary outcome is the ratio producing the maximum enhancement of duration of clinical effect. METHODS: Sixty-eight healthy children were anaesthetized with propofol, nitrous oxide and fentanyl. They then randomly received either Roc 0.4 (mg.kg(-1)), Miv 0.133 (mg.kg(-1)) or one of four Roc + Miv combinations (mg.kg(-1)): Roc 0.32 + Miv 0.027; Roc 0.24 + Miv 0.053; Roc 0.16 + Miv 0.08; and Roc 0.08 + Miv 0.106. The mechanical response of the adductor pollicis muscle to supramaximal stimulation of the ulnar nerve at the wrist was recorded. RESULTS: Duration of effect was greater in the combination groups than that predicted from the duration of Roc or Miv used alone. Duration was maximally increased around a 1:1 ratio (2:3 and 3:2) of Roc and Miv. The likelihood of achieving 100% block was greater in combination groups compared with Roc or Miv used alone. CONCLUSIONS: Combinations of Roc and Miv show a synergistic effect, which appears maximal as the mixture approaches a 1:1 ratio of their ED95s. This combination acted as if a larger effective dose of a single (new) drug had been given, but did not offer the advantage of both rapid onset and short duration of effect.

Methadone dosage for prevention of opioid withdrawal in children.

BACKGROUND: Opioids are frequently used for sedation in the Paediatric Intensive Care Unit (PICU). With time the dosing often increases because of tolerance. On cessation of the sedation there is a risk of the opioid withdrawal syndrome. The aim of our study was to evaluate methadone dosing as a risk factor for opioid withdrawal and to determine optimal dose and efficacy of methadone to prevent withdrawal. METHOD: We undertook a clinical, retrospective, chart review study. Data were analysed from the quality improvement initiative database of a tertiary-care 18 bed PICU. RESULTS: Data from 30 children who received an opioid infusion for >/=7 days and subsequently received methadone for opioid withdrawal (between January 2000 and July 2001) were analysed. Nurses documented the presence or absence of withdrawal signs daily. Our unit protocol has recommended converting the patient's opioid dose into fentanyl equivalents and a dose of methadone equal to the total daily dose of fentanyl to be given three times a day. Twenty patients had no or minimal withdrawal symptoms and 10 experienced significant withdrawal. Age, weight, PRISM score, lorazepam dose, muscle relaxant use and fentanyl dose were not statistically significantly between these groups. Receiver Operator Characteristics analysis showed that 80% of the suggested methadone dose was effective in minimizing withdrawal symptoms. The odds ratio for withdrawal with <80% of the predicted methadone dose was 21. CONCLUSIONS: Inadequate methadone is a risk factor for opioid withdrawal. A daily starting methadone dose equivalent to 2.5 times the daily fentanyl dose is effective in minimizing withdrawal symptoms.

Sedation monitoring of children by the Bispectral Index in the pediatric intensive care unit.

OBJECTIVE: To compare the Bispectral Index with clinical sedation assessment using the Ramsay score in normal sedated and paralyzed critically ill children. DESIGN: Prospective observational study. SETTING: Multidisciplinary 18-bed pediatric intensive care unit at a university-affiliated children's hospital. PATIENTS: A total of 48 pediatric intensive care unit patients requiring mechanical ventilation and sedation. Of these, 24 patients were not paralyzed. MEASUREMENTS AND MAIN RESULTS: Twenty-four pediatric intensive care unit children with normal mentation who were sedated and being ventilated in the intensive care unit were included in the study. The Ramsay score as assessed by the nurses was compared with the blinded Bispectral Index score. The regression coefficient between the Bispectral Index score and Ramsay score was 0.77 (p < 0.0001). The second group of patients included normal children similar to the previous group but paralyzed. The Ramsay score, as expected, was a poor tool for sedation assessment in a paralyzed patient. The nurse assessment only detected 8% of those patients at risk for awareness and recall (Bispectral Index score, > or = 80). Nurse assessment for oversedation (Bispectral Index score, < 40) was better with a sensitivity of 89.7% but a poor specificity of 38.6%. CONCLUSIONS: The Bispectral Index correlates well with the Ramsay score in the normal sedated child. The Ramsay score and bedside nurse assessment are inadequate for monitoring the depth of sedation in paralyzed children. The Bispectral Index is a useful adjunct in assessing sedation in a paralyzed patient.

Heliox enhances carbon dioxide clearance from lungs of normal rabbits during low bias flow oscillation.

OBJECTIVES: To evaluate carbon dioxide clearance in normal rabbits during high-frequency oscillatory ventilation with helium-oxygen mixtures by using a low bias flow oscillation (LBFO) system designed to conserve expensive gas. DESIGN: A prospective, paired-controlled, interventional, in vivo animal laboratory study. SETTING: Animal laboratory of a health science university. SUBJECTS: Twelve New Zealand White rabbits. INTERVENTIONS: Juvenile rabbits were anesthetized, paralyzed, and ventilated through a tracheostomy. LBFO was performed with a modified high-frequency oscillatory ventilation circuit that uses low bias flow (100 mL/kg) and a soda lime cartridge to clear carbon dioxide. LBFO-heliox trials were performed with 20%, 40%, 50%, 60%, and 70% helium (balanced with oxygen) for 30 mins. Each heliox trial was preceded by a paired control trial with 40% oxygen and 60% nitrogen for 30 mins. Ventilator settings in control and heliox trials were identical. During the second part of the study, four rabbits were made hypercapnic by decreasing the power (amplitude), and LBFO was performed with 70% helium against paired-control trials of 40% oxygen and 60% nitrogen. Arterial blood gases were measured at 15-min intervals and airway pressure amplitude was recorded. PaCO2 of control and heliox trials, alveolar PO2-PaO2 gradient of control, and 60% helium trials were compared by paired Student's t-test. MEASUREMENTS AND MAIN RESULTS: At constant power, amplitude was unaffected by helium. Helium concentrations of 40%, 50%, 60%, and 70% decreased PaCO2 by 12%, 33%, 36%, and 46%, respectively. Alveolar PO2-PaO2 gradient was decreased by 40% during ventilation with 60% helium. Under hypercapnic conditions, 70% helium decreased PaCO2 by 20%. CONCLUSION: Helium concentrations > or = 40% facilitate carbon dioxide clearance from lungs of normal rabbits during LBFO. This could be accomplished inexpensively with LBFO due to preservation of heliox when using this device.