Myron Yaster

Life-threatening airway obstruction as a complication to the management of mediastinal masses in children

Life-threatening airway obstruction from large mediastinal masses in children poses a difficult diagnostic and therapeutic dilemma, requiring the close coordination of a pediatric surgeon, anesthesiologist, radiologist, and oncologist. To focus on this problem, the anesthetic and surgical management of 50 consecutive children with mediastinal masses treated between 1978 and 1984 were reviewed. Thirty children presented with respiratory symptoms; nine had life-threatening respiratory compromise with dyspnea, orthopnea, and stridor. Thirteen of these symptomatic children had marked compression of the trachea and/or mainstem bronchi on radiographic studies. The tracheal cross-sectional area which was measured by computed tomography was decreased by 35% to 93% of the normal tracheal dimensions in these children. Nonresectable malignant neoplasms including lymphoma, Hodgkins disease, rhabdomyosarcoma, and neuroblastoma were the eventual diagnoses in 10 of these patients. The other 3 patients were less than 4 years old and had benign lesions. General anesthesia was judged to be prohibitively risky in 5 of 13 patients. The diagnosis was established by node or needle biopsy under local anesthesia, and general anesthesia was deferred until the compromised airway was alleviated by radiation and chemotherapy. General anesthesia with endotracheal intubation was administered to 8 patients, 5 of whom developed total airway obstruction. Using a variety of maneuvers, ventilation was reestablished in all 5 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effects of a Small-Dose Naloxone Infusion on Opioid- Induced Side Effects and Analgesia in Children and Adolescents Treated with Intravenous Patient-Controlled Analgesia: A Double-Blind, Prospective, Randomized, Controlled Study

Opioids are frequently associated with side effects such as nausea, vomiting, and pruritus. We hypothesized that a prophylactic, continuous small-dose naloxone infusion would reduce the incidence of opioid-induced side effects without affecting analgesia or opioid consumption. In this prospective, double-blind, randomized, controlled clinical trial, we studied 46 postoperative patients (M:F, 21:25), averaging 14 ± 2.5 yr and 53 ± 17 kg, at the start of morphine IV patient-controlled analgesia. Patients were randomized to either saline (control, n = 26) or naloxone 0.25 &mgr;g · kg−1 · h−1 (n = 20). We found that the incidence and severity of pruritus (77% versus 20%; P < 0.05) and nausea (70% versus 35%; P < 0.05) was significantly more frequent in the placebo group compared with the naloxone group. Morphine consump-tion (1.02 ± 0.41 mg · kg−1 · d−1 versus 1.28 ± 0.61 mg · kg−1 · d−1), pain scores at rest (4 ± 2 versus 3 ± 2), and pain scores with coughing (6 ± 2 versus 6 ± 2) were not different. We conclude that, in children and adolescents, a small-dose naloxone infusion (0.25 &mgr;g · kg−1 · h−1) can significantly reduce the incidence and severity of opioid-induced side effects without affecting opioid-induced analgesia. When initiating morphine IV patient-controlled analgesia for the treatment of moderate to severe pain, clinicians should strongly consider starting a concomitant small-dose naloxone infusion.

The safety and efficacy of parent-/nurse-controlled analgesia in patients less than six years of age.

Over the past 5 yr, we have treated nonsurgical and postoperative pain in children <6 yr of age by using a patient-controlled analgesia pump to deliver small-dose continuous IV opioid infusions supplemented by parent- and nurse-controlled opioid bolus dosing. We call this technique parent-/nurse-controlled analgesia (PNCA). Because the safety and efficacy of PNCA have not been previously evaluated, we have undertaken a prospective, 1-yr observational study to determine patient demographics, effectiveness of analgesia, and the incidence of complications (pruritus, vomiting, and respiratory depression) in patients receiving PNCA. Data were collected on 212 children (98 female) who were treated on 240 occasions with PNCA for episodes of pain. Patients averaged 2.3 ± 1.7 yr of age and 11 ± 5 kg, and received a median of 4 (range 2–54) days of PNCA therapy. Maximum daily pain scores were ≤3/10 (objective pain scale) or ≤2/5 (objective or self-report pain scale) in more than 80% of all occasions of PNCA use. PNCA usage was associated with an 8% incidence of pruritus and a 15% incidence of vomiting on the first day of treatment. Nine children studied received naloxone, four (1.7%) for treatment of PNCA-related apnea or desaturation. All had improvement in their symptoms after naloxone administration. Implications Parent-/nurse-controled analgesia provided effective pain relief in most children <6 yr of age experiencing nonsurgical or postoperative pain. The observed incidence of vomiting and pruritis was similar to that seen in older patients treated with patient-controlled analgesia. However, significant respiratory depression, although uncommon, did occur, thus reinforcing the need for close patient monitoring.

Bacterial Colonization and Infection Rate of Continuous Epidural Catheters in Children

Continuous epidural infusions are widely used for postoperative analgesia in children.We prospectively studied the incidence of bacterial colonization of caudal and lumbar epidural catheters, as well as the incidence of serious systemic and local infection, in 210 children after short-term epidural analgesia. Using aseptic technique, epidural catheters were inserted into either the lumbar or the caudal epidural space based on the preferences of the anesthesia team and/or clinical indication. The integrity of the catheter and overlying transparent dressing site was evaluated by a member of the pediatric pain service at least once a day. The catheters were aseptically removed if the patient had a fever greater than 39[degree sign]C, if the dressing was compromised, or when epidural analgesia was no longer required. The subcutaneous portion of the catheter was semiquantitatively cultured. Cellulitis (erythema, swelling, purulent discharge, pustule formation, or tenderness) was diagnosed by examination of the epidural insertion site. The mean (+/- SD) age of patients in the caudal catheter group (n = 170) was 3 +/- 3 yr; their mean weight was 13 +/- 11 kg. The mean (+/- SD) age of patients in the epidural catheter group (n = 40) was 11 +/- 4 yr; their mean weight was 36 +/- 23 kg. All catheters remained in place for 3 +/- 1 days (range 1-5 days). There was no serious systemic infection (meningitis, epidural abscess, or systemic sepsis). Of all epidural catheters, 35% (73 of 210) were colonized. Gram-positive colonization was similar in caudal (25%; 43 of 170) and lumbar (23%; 9 of 40) catheters. Gram-negative organisms were cultured from 16% of the caudal catheters (27 of 170) and 3% of the lumbar catheters (1 of 40). In patients treated with caudal epidural catheters, children aged >3 yr were less likely to have colonized epidural catheters than younger children. Age did not affect the probability of developing cellulitis at the insertion site. Although patients aged <3 yr with caudal catheters had a slightly greater risk of cellulitis than children aged >3 yr (14% vs 9%), this association was very weak (P = 0.33). We observed that, despite bacterial colonization of caudal and lumbar epidural catheters, serious systemic and local infection after short-term epidural analgesia did not occur in our study. Implications: Continuous epidural infusions are widely used for postoperative analgesia in children. We found no serious systemic infections after short-term (3 days) continuous epidural analgesia in children. (Anesth Analg 1998;86:712-6)

Management of pediatric pain with opioid analgesics

We have attempted to dispel many of the myths and misconceptions surrounding the use of narcotic analgesics in the treatment of childhood pain. Our hope is that an improved understanding and the application of effective, safe therapy will minimize the suffering of the child with acute or chronic pain.

Detection of intravascular injection of regional anaesthetics in children

PurposeDetection of intravascular injection of local anaesthetic during placement of regional blocks in children by using epinephnne-induced tachycardia or hypertension may produce false positive and false negative findings. This study evaluates ECG changes as markers of intravascular injection of local anaesthetics with epinephnne, during placement of epidural blocks in children.MethodsObservational study in a teaching hospital of all epidural anaesthetics administered to paediatnc patients dunng one year. General anaesthesia, where used, was not controlled. An ECG rhythm strip was recorded during test dose injection and analyzed for changes in rate, rhythm, and T-wave configuration.ResultsDuring the study penod, 742 paediatnc epidural blocks were administered. There were 644 caudal (284 without catheters). 97 lumbar, and one thoracic epidural anaesthetics. Satisfactory placement was achieved in 97.7% of patients. Intravascular injection was detected in 42 (5.6%) of epidural anaesthetics (3.8% and 6.7% of straight needle and catheter injections, respectively). Detection was by immediate aspiration of blood in six patients, and by heart rate increases > 10 bpm in 30. Five had heart rate decreases suggesting a baroreceptor response. Five had heart rate increases < 10 bpm that were possible responses to noxious stimuli. Of 30 patients with known intravascular injection and for whom ECG strips were available, 25 (83%) had T-wave amplitude increases > 25%. and 29 (97%) had ECG changes in T-wave or rhythm in response to the epinephrine injection. There were no false positives.ConclusionIn order to reduce risks associated with epidural anaesthesia in children, epinephnne should be added to the local anaesthetic test dose, the ECG should be monitored continuously for changes in heart rate, rhythm, and T-wave amplitude. Epidural injections should be given in small increments.RésuméObjectifLa détection de l’injection intravasculaire d’anesthésique local pendant l’administration d’un bloc régional chez l’enfant par la tachycardie et l’hypertension peut donner lieu à des faux positifs et des faux négatifs. Cette étude évalue les changements de l’ÉCG comme indices d’injection intravasculaire d’anesthésiques locaux adrénalinés pendant l’administration du bloc.MéthodesL’inventaire de toutes les anesthésies épidurales administrées à des enfants pendant une année dans un hôpital d’enseignement. Lanesthésie générale était un critère d’exclusion. Un bande de rythme ÉEG était enregistrée pendant l’injection de la dose test et examinée relativement aux changements de fréquence, de rythme et de configuration de l’onde T.RésultatsPendant la pénode d’étude, 742 blocs épiduraux pédiatriques ont été administrés, dont 644 anesthésies caudales (284 sans cathéter). 97 lombaires et une épidurale thoracique avec succès dans 97,7% des patients. Une injection mtravasculaire est survenue au cours de 42 (5,6%) anesthésies épidurales (3,8% par l’aiguille et 7.6% par le cathéter) et a été détectée par l’aspiration immédiate de sang chez six patients et par une augmentation de la fréquence cardiaque > 10 bpm chez 30. La fréquence a diminué chez cinq patients suggérant une réponse barotropique. Cinq ont présenté des augmentations de fréquence < 10 bpm en réaction possible aux stimuli nocifs. Sur 30 patients chez qui l’injection intravasculaire était claire et chez qui des bandes de rythme étaient disponibles. 25 (83%) présentaient une augmentation de l’amplitude de l’onde T > 25%. et 29 (97%) avaient des changements de l’onde T ou du rythme en réponse à l’injection d’épinéphnne. Il n’y a pas eu de faux positifs.ConclusionPour réduire les risques associés à l’anesthésie épidurale chez l’enfant, de l’épinéphnne devrait être ajoutée à la dose test d’anesthésique local et l’ÉCG devrait être monitoré en continu pour révéler les changements de fréquence, du rythme et d’amplitude de l’onde T. Lanesthésique local doit être administré dans l’espace épidural en petites doses répétées.

Genetic knockout and pharmacologic inhibition of neuronal nitric oxide synthase attenuate nerve injury-induced mechanical hypersensitivity in mice.

Neuronal nitric oxide synthase (nNOS) is a key enzyme for nitric oxide production in neuronal tissues and contributes to the spinal central sensitization in inflammatory pain. However, the role of nNOS in neuropathic pain remains unclear. The present study combined a genetic strategy with a pharmacologic approach to examine the effects of genetic knockout and pharmacologic inhibition of nNOS on neuropathic pain induced by unilateral fifth lumbar spinal nerve injury in mice. In contrast to wildtype mice, nNOS knockout mice failed to display nerve injury-induced mechanical hypersensitivity. Furthermore, either intraperitoneal (100 mg/kg) or intrathecal (30 μg/5 μl) administration of L-NG-nitro-arginine methyl ester, a nonspecific NOS inhibitor, significantly reversed nerve injury-induced mechanical hypersensitivity on day 7 post-nerve injury in wildtype mice. Intrathecal injection of 7-nitroindazole (8.15 μg/5 μl), a selective nNOS inhibitor, also dramatically attenuated nerve injury-induced mechanical hypersensitivity. Western blot analysis showed that the expression of nNOS protein was significantly increased in ipsilateral L5 dorsal root ganglion but not in ipsilateral L5 lumbar spinal cord on day 7 post-nerve injury. The expression of inducible NOS and endothelial NOS proteins was not markedly altered after nerve injury in either the dorsal root ganglion or spinal cord. Our findings suggest that nNOS, especially in the dorsal root ganglion, may participate in the development and/or maintenance of mechanical hypersensitivity after nerve injury.

Preinduction of Anesthesia in Children with Rectally Administered Midazolam

The authors evaluated the efficacy of rectally administered midazolam for preinduction (i.e., premedication/induction) of anesthesia in 67 pediatric patients, ASA physical status 1 or 2, undergoing a variety of elective surgical procedures. In phase 1, 41 children weighing 12 +/- 3 kg (range 7-20 kg) and 31 +/- 16 months (range 8-67 months) of age (mean +/- SD) received midazolam, 0.4-5.0 mg.kg-1, in an attempt to produce unconsciousness. Only one child lost consciousness (4.5 mg.kg-1). However, at all doses, inhalational induction of anesthesia was facilitated because children were tranquil and calmly separated from their parent(s). There were no clinically significant changes in arterial blood pressure, heart rate, oxyhemoglobin saturation, and end-tidal carbon dioxide concentration, 10 min after drug administration. In phase 2, 26 children weighing 17 +/- 4 kg (range 10-26 kg) and 44 +/- 19 months (range 17-84 months) months of age undergoing tonsil and/or adenoid surgery were studied to determine the optimal sedative dose of rectally administered midazolam. Patients received 0.3, 1.0, 2.0, or 3.0 mg.kg-1 of midazolam in a randomized, double-blind fashion. One third (3 of 9) of patients receiving 0.3 mg.kg-1 struggled during mask induction. All patients receiving greater than or equal to 1.0 mg.kg-1 were adequately sedated (P less than 0.008). Discharge from the postanesthesia care unit (PACU), however, was delayed (greater than 60 min) in children receiving greater than or equal to 2.0 mg.kg-1 (P less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of neuronal excitatory amino acid carrier 1 expression in rat dorsal root ganglion neurons and their central terminals

The expression and distribution of the neuronal glutamate transporter, excitatory amino acid carrier-1 (EAAC1), are demonstrated in the dorsal root ganglion neurons and their central terminals. Reverse transcriptase-polymerase chain reaction shows expression of EAAC1 mRNA in the dorsal root ganglion. Immunoblotting analysis further confirms existence of EAAC1 protein in this region. Immunocytochemistry reveals that approximately 46.6% of the dorsal root ganglion neurons are EAAC1-positive. Most EAAC1-positive neurons are small and around 250-750 microm2 in surface area, and some co-label with calcitonin gene-related peptide (CGRP) or isolectin IB4. In the spinal cord, EAAC-1 immunoreactive small dot- or patch-like structures are mainly localized in the superficial dorsal horn, and some are positive for CGRP or labeled by isolectin IB4. Unilateral dorsal rhizotomy experiments further show that EAAC1 immunoreactivity is less intense in superficial dorsal horn on the side ipsilateral to the dorsal rhizotomy than on the contralateral side. The results indicate the presence of EAAC1 in the dorsal root ganglion neurons and their central terminals. Our findings suggest that EAAC1 might play an important role in transmission and modulation of nociceptive information via the regulation of pre-synaptically released glutamate.

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. I. Emergence and recovery profiles

Pyloric stenosis is sometimes associated with hemodynamic instability and postoperative apnea. In this multicenter study we examined the hemodynamic response and recovery profile of remifentanil and compared it with that of halothane in infants undergoing pyloromyotomy. After atropine, propofol, and succinylcholine administration and tracheal intubation, patients were randomized (2:1 ratio) to receive either remifentanil with nitrous oxide and oxygen or halothane with nitrous oxide and oxygen as the maintenance anesthetic. Pre- and postoperative pneumograms were done and evaluated by an observer blinded to the study. Intraoperative hemodynamic data and postanesthesia care unit (PACU) discharge times, PACU recovery scores, pain medications, and adverse events (vomiting, bradycardia, dysrhythmia, and hypoxemia) were recorded by the study’s research nurse. There were no significant differences in patient age or weight between the two groups. There were no significant differences in hemodynamic values between the two groups at the various intraoperative stress points. The extubation times, PACU discharge times, pain medications, and adverse events were similar for both groups. No patient anesthetized with remifentanil who had a normal preoperative pneumogram had an abnormal postoperative pneumogram, whereas three patients with a normal preoperative pneumogram who were anesthetized with halothane had abnormal pneumograms after.