Mary C. Theroux

Multimodality monitoring of transcranial electric motor and somatosensory-evoked potentials during surgical correction of spinal deformity in patients with cerebral palsy and other neuromuscular disorders.

Study Design. This prospective, descriptive study determined the reliability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials in children with neuromuscular scoliosis. Objective. To assess the applicability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials during surgical correction of neuromuscular scoliosis, particularly with cerebral palsy-related deformity. Summary of Background Data. During corrective spinal surgery for neuromuscular scoliosis, intraoperative multimodality spinal cord monitoring is recommended. There exist conflicting, retrospective studies regarding the reliability of spinal cord monitoring in patients with neuromuscular scoliosis. Methods. Transcranial electric motor potentials and posterior tibial nerve somatosensory-evoked potentials were monitored in all patients presenting for spinal fusion between 2000 and 2001. Anesthesia was standardized for all patients. Results. There were 68 patients subdivided into two subject groups. Group I consisted of 39 patients with neuromuscular scoliosis associated with cerebral palsy, and Group II consisted of 29 children with neuromuscular scoliosis due to a disease process other than cerebral palsy. Five of the 68 patients had significant amplitude changes in 1 or both monitoring methods during surgery relative to baseline. Of these, one had permanent neurologic deficit despite standard intervention. Somatosensory-evoked potentials were monitored successfully in 82% of the cerebral palsy and 86% of the noncerebral palsy patients. Transcranial electric motor-evoked potentials, on the other hand, were monitorable in 63% of patients with mild or moderate degrees of cerebral palsy and 39% of those with severe involvement. Eighty-six percent of those with noncerebral palsy-related neuromuscular scoliosis had recordable motor-evoked potentials at baseline. Conclusion. Both transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials can be monitored reliably in most patients with neuromuscularscoliosis. Those with severe cerebral palsy present the greatest challenge to successful neurophysiologicmonitoring.

A Study of Desmopressin and Blood Loss during Spinal Fusion for Neuromuscular Scoliosis A Randomized, Controlled, Double-Blinded Study

Background: Studies examining the use of desmopressin acetate (DDAVP) have shown variable results in DDAVPs efficacy for reducing blood loss. Studies of adults having cardiac surgery and of children having spinal fusion have suggested that patients with complicated medical histories and complex surgical procedures may benefit from use of DDAVP. Therefore, this study was designed to examine the homeostatic effects of DDAVP in children with severe cerebral palsy undergoing spinal fusion. Methods: A randomized, double‐blinded, and placebo‐controlled trial of DDAVP was designed to enroll 40 patients. However, termination of the study was advised by the Institutional Review Board after 21 patients were enrolled. All patients had spastic quadriplegic‐type cerebral palsy and were randomly assigned to one of two groups. The DDAVP group received 0.3 micro gram/kg DDAVP in 100 ml normal saline, and the placebo group received normal saline alone. All patients were anesthetized with nitrous oxide, oxygen, isoflurane, and fentanyl. Factor VIIIC and von Willebrands factor (vWF) concentrations were measured in blood drawn before DDAVP infusion and 1 h after infusion. Blood pressure was maintained at a systolic pressure of less than 100 mmHg. Use of crystalloids, packed erythrocytes, platelets, and fresh frozen plasma were based on criteria established by protocol. Estimated blood loss was assessed by weighing sponges and measuring suctioned blood from canisters. Results: Estimated blood loss (intraoperative and postoperative) and amount of packed erythrocytes transfused were similar for the DDAVP and placebo groups. Concentrations of both factor VIIIC and vWF were significantly greater after DDAVP infusion when compared with concentrations after placebo infusion. Conclusions: In the children who had complex spinal fusion, there was no difference in estimated blood loss between those who received DDAVP and those who received a placebo. Administration of DDAVP significantly increased factor VIIIC and vWF levels.

The Potency of Succinylcholine in Obese Adolescents

We constructed a single-dose response curve for succinylcholine in 30 obese adolescents during thiopental-fentanyl anesthesia administration by using 100 &mgr;g/kg, 150 &mgr;g/kg, or 250 &mgr;g/kg IV. The maximal response (percent depression of neuromuscular function) of the adductor pollicis to supramaximal train-of-four stimuli was recorded by using a Datex (Helsinki, Finland) relaxograph. Linear regression and inverse prediction were used to determine doses of succinylcholine to produce 50% (ED50), 90% (ED90), and 95% (ED95) depression of neuromuscular function. The ED50, ED90, and ED95 were 152.8 &mgr;g/kg (95% confidence interval: 77.8–299.5), 275.4 &mgr;g/kg (95% confidence interval: 142–545.7), and 344.3 &mgr;g/kg (95% confidence interval: 175.3–675.3), respectively. This ED50 is similar to the dose reported for similarly aged, nonobese adolescents, 147 &mgr;g/kg. The previously reported ED95 for succinylcholine in nonobese adolescents, 270 &mgr;g/kg, is within the 95% confidence interval generated for ED95 in our study. Implications: The potency estimates for succinylcholine in obese (body mass index > 30 kg/m2) adolescents are comparable to those in similarly aged nonobese adolescents when dosing is calculated based on total body mass and not lean body mass. When a rapid sequence induction of anesthesia is considered in an obese adolescent, the dose of succinylcholine should be based on actual (not lean) body mass.

Dose Response of Succinylcholine at the Adductor Pollicis of Children with Cerebral Palsy During Propofol and Nitrous Oxide Anesthesia

Children with cerebral palsy may be resistant to paralysis induced by nondepolarizing neuromuscular blocking drugs. Potency of a bolus of succinylcholine in children with cerebral palsy has not been studied previously. Therefore, we measured the response of the adductor pollicis to succinylcholine in children with cerebral palsy anesthetized with propofol and nitrous oxide. Forty children between the ages of 2 and 10.2 yr with spastic quadriplegic cerebral palsy were randomly assigned to receive 100, 175, 250, or 375 micrograms/kg of succinylcholine during anesthesia with propofol and nitrous oxide. The ulnar nerve was stimulated with a train-of-four supramaximal stimulus every 10 s and the compound electromyogram of the adductor pollicis recorded by a Datex NMT monitor. Plasma cholinesterase activity was measured in all patients with three different substrates (propionylthiocholine, benzoylcholine, and succinylcholine). Dibucaine number was also determined using inhibition of benzoylcholine degradation. ED50 of succinylcholine was 146.8 micrograms/kg with 95% confidence intervals of 111.4-193.7 micrograms/kg. ED95 of succinylcholine was 360.5 micrograms with 95% confidence intervals of 273.3-475.5 micrograms/kg. We conclude that children with cerebral palsy are slightly sensitive to succinylcholine, but probably not sufficiently to be clinically important.

Neuromuscular junctions in Cerebral palsy: Presence of extrajunctional acetylcholine receptors

Background Cerebral palsy (CP) is the most prevalent neurologic disease in children. A primary deficit in CP is neuromuscular dysfunction; however, neuromuscular junctions in children with CP have not been studied. Evidence exists that up-regulation of acetylcholine receptors (AChRs) may be present in children with CP, and the current study was undertaken to examine this possibility. Methods Thirty-nine children with spastic CP and 25 neurologically normal children were enrolled in the study. Paraspinal muscles underwent biopsy during scheduled spinal fusion surgery. Two sets of assessments were performed on the biopsy specimens: (1) reverse-transcription polymerase chain reaction and Western blotting to evaluate the expression of the &ggr; subunit of the AChR; and (2) histologic evaluation using a double-stain technique for AChR and acetylcholinesterase, wherein acetylcholinesterase staining defined the limits of the neuromuscular junction, and AChR staining that appeared outside of these limits indicated an abnormal distribution of AChRs. Results Reverse-transcription polymerase chain reaction and Western blot analyses showed that neither the CP nor non-CP samples had detectable &ggr;-AChR subunit. Histologic analysis indicated that 11 of 39 children with CP and none of 20 children with idiopathic scoliosis scored positive for the presence of AChR outside of the neuromuscular junction (P = 0.0085). Conclusion A subset of children with CP have an abnormal distribution of AChR relative to the acetylcholinesterase found at the neuromuscular junction. The altered distribution of AChR in CP was not associated with a detectable presence of the &ggr;-AChR subunit, suggesting that the nonjunctional AChRs in CP does not contain the &ggr; subunit.

Protective ventilation to reduce inflammatory injury from one lung ventilation in a piglet model

Objectives:  To test the hypothesis that protective ventilation strategy (PVS) as defined by the use of low stretch ventilation (tidal volume of 5 ml·kg−1 and employing 5 cm of positive end expiratory pressure (PEEP) during one lung ventilation (OLV) in piglets would result in reduced injury compared to a control group of piglets who received the conventional ventilation (tidal volume of 10 ml·kg−1 and no PEEP).

Recovery from Doxacurium Infusion Administered to Produce Immobility for More Than Four Days in Pediatric Patients in the Intensive Care Unit

Doxacurium was administered by titrated infusion to 14 pediatric patients for 4.7-12.3 days after laryngotracheal reconstruction to produce minimum spontaneous movement and less than five posttetanic movements of the first toe after stimulation of the posterior tibial nerve. Recovery was documented by stimulation of the ulnar nerve with 2 Hz for 2 s (train-of-four [TOF]) at intervals of 1 min and measurement of the ratio of the fourth to the first response (TOF ratio) at the adductor pollicis. During spontaneous recovery, the TOF ratio was between 0.4 and 0.7 for 0.6-3.3 h, mean (SEM) 2.2 (0.31) h. The TOF ratio equaled 1 between 4.7 and 23.0 h, mean (SEM) 11.0 (2.1) h after termination of doxacurium infusion. In six of the patients, weakness and decreased coordination were noted for a few days to weeks postoperatively. There were no complications related to impairment of upper airway function or ventilation in those patients who had recovery of neuromuscular transmission to the extent of TOF ratio equal to 1 prior to extubation or in those patients in whom weakness or lack of coordination was noted after tracheal extubation. (Anesth Analg 1997;84:307-14)

Popliteal pterygium syndrome with syngnathia.

We report a case of perioperative management of a neonate with popliteal pterygium syndrome complicated by interalveolar syngnathia. Syngnathia were excised in the operating room without a major anaesthetic. We discuss our management of this case, as well as other possible strategies to secure the airway in neonates with syngnathia. We also reviewed the literature regarding airway management in presence of syngnathia in similar situations.

Intraoperative Presentation of Malignant Hyperthermia (Confirmed by RYR1 Gene Mutation, c.7522C>T; p.R2508C) Leads to Diagnosis of King-Denborough Syndrome in a Child With Hypotonia and Dysmorphic Features: A Case Report.

We present the novel case report of a child with hypotonia and dysmorphic features who developed malignant hyperthermia (MH) intraoperatively. Neurology workup revealed the presence of a known causative ryanodine receptor (RYR1) mutation for MH, c.7522C>T; p.R2508C. Furthermore, the neurology workup diagnosed the child with King-Denborough syndrome (KDS). This particular mutation has never been documented in a patient with KDS. Atypical presentation of MH is more likely in patients with RYR1-related myopathy. A high index of suspicion for MH in children with myopathy is important. The MH hotline was helpful in the management of this patient when it was called after the initial dose of dantrolene. A neurology consult was essential for the diagnosis of KDS and future care.