Warwick A. Ames

The effect of ionised magnesium on coagulation using thromboelastography

Magnesium is an ionised mineral with therapeutic uses. There is laboratory evidence that it may have an anticoagulant activity although recent research has been to the contrary. The clinical implications of the effect of a therapeutic dose of magnesium on coagulation have yet to be resolved conclusively. In our study, 10 healthy volunteers were given 4 g of magnesium sulphate intravenously. Thromboelastographs were recorded and blood analysed for haematological indices, before and after the infusion. All variables associated with coagulation remained unchanged except the alpha angle on the thromboelastograph which increased significantly. We conclude that in our in vivo study, the effect of magnesium sulphate on coagulation is not clinically significant.

The Accuracy of a Near-Infrared Spectroscopy Cerebral Oximetry Device and Its Potential Value for Estimating Jugular Venous Oxygen Saturation

BACKGROUND:An intriguing potential clinical use of cerebral oximeter measurements (SctO2) is the ability to noninvasively estimate jugular bulb venous oxygen saturation (SjvO2). Our purpose in this study was to determine the accuracy of the FORE-SIGHT® (CAS Medical Systems, Branford, CT), which is calibrated to a weighted average of 70% (SjvO2) and 30% arterial saturation, for Food and Drug Administration pre-market approval 510(k) certification by adapting an industry standard protocol, ISO 9919:2005 (www.ISO.org) (used for pulse oximeters), and to evaluate the use of SctO2 and SpO2 measurements to noninvasively estimate jugular venous oxygen saturation (SnvO2). METHODS:Paired blood gas samples from the radial artery and the jugular venous bulb were collected from 20 healthy volunteers undergoing progressive oxygen desaturation from 100% to 70%. The blood sample pairs were analyzed via co-oximetry and used to calculate the approximate mixed vascular cerebral blood oxygen saturation, or reference SctO2 values (refSctO2), during increasing hypoxia. These reference values were compared to bilateral FORE-SIGHT SctO2 values recorded simultaneously with the blood gas draws to determine its accuracy. Bilateral SctO2 and SpO2 measurements were then used to calculate SnvO2 values which were compared to SjvO2. RESULTS:Two hundred forty-six arterial and 253 venous samples from 18 subjects were used in the analysis. The ipsilateral FORE-SIGHT SctO2 values showed a tolerance interval (TI) of [−10.72 to 10.90] and Lin concordance correlation coefficient (CCC) with standard error (SE) of 0.83 ± 0.073 with the refSctO2 values calculated using arterial and venous blood gases. The ipsilateral data had a CCC of 0.81 + 0.059 with TI of [−9.22 to 9.40] with overall bias of 0.09%, and amplitude of the root mean square of error after it was corrected with random effects analysis was 2.92%. The bias and variability values between the ipsilateral and the contralateral FORE-SIGHT SctO2 measurements varied from person to person. The SnvO2 calculated from the ipsilateral SctO2 and SpO2 data showed a CCC ± SE of 0.79 ± 0.088, TI = [−14.93 to 15.33], slope of 0.98, y-intercept of 1.14% with SjvO2 values with a bias of 0.20% and an Arms of 4.08%. The SnvO2 values calculated independently from contralateral forehead FORE-SIGHT SctO2 values were not as correlated with the SjvO2 values (contralateral side CCC + SE = 0.72 ± 0.118, TI = [−14.86 to 15.20], slope of 0.66, and y-intercept of 20.36%). CONCLUSIONS:The FORE-SIGHT cerebral oximeter was able to estimate oxygen saturation within the tissues of the frontal lobe under conditions of normocapnia and varying degrees of hypoxia (with 95% confidence interval of [−5.60 to 5.78] with ipsilateral blood sample data). These findings from healthy volunteers also suggest that the use of the calculated SnvO2 derived from SctO2 and SpO2 values may be a reasonable noninvasive method of estimating SjvO2 and therefore global cerebral oxygen consumption in the clinical setting. Further laboratory and clinical research is required to define the clinical utility of near-infrared spectroscopy determination of SctO2 and SnvO2 in the operating room setting.

Evaluation of Pediatric Near-Infrared Cerebral Oximeter for Cardiac Disease

BACKGROUND Cerebral hypoxia-ischemia remains a complication in children with congenital heart disease. Near-infrared spectroscopy can be utilized at the bedside to detect cerebral hypoxia-ischemia. This study aimed to calibrate and validate an advanced technology near-infrared cerebral oximeter for use in children with congenital heart disease. METHODS After institutional review board approval and parental consent, 100 children less than 12 years and less than 40 kg were enrolled. Phase I (calibration) measured arterial and jugular venous saturation (SaO(2), SjO(2)) by co-oximetry simultaneously with device signals to calibrate an algorithm to determine regional cerebral saturation against a weighted average cerebral saturation (0.7 SjO(2) + 0.3 SaO(2)). Phase II (validation) evaluated regional cerebral saturation from the algorithm against the weighted average cerebral saturation by correlation, bias, precision, and A(Root Mean Square) assessed by linear regression and Bland-Altman analysis. RESULTS Of 100 patients, 86 were evaluable consisting of 7 neonates, 44 infants, and 35 children of whom 55% were female, 79% Caucasian, and 41% with cyanotic disease. The SaO(2) and regional cerebral saturation ranged from 34% to 100% and 34% to 91%, respectively. There were no significant differences in subject characteristics between phases. For the entire cohort, A(RMS), bias, precision, and correlation coefficient were 5.4%, 0.5%, 5.39%, and 0.88, respectively. Age, skin color, and hematocrit did not affect these values. CONCLUSIONS This cerebral oximeter accurately measures the absolute value of cerebral saturation in children over a wide range of oxygenation and subject characteristics, offering advantages in assessment of cerebral hypoxia-ischemia in congenital heart disease.

The role of corticosteroids in Duchenne muscular dystrophy: a review for the anesthetist

Corticosteroids are a diverse class of drugs that are used in a wide variety of clinical disorders. Anesthetists are most familiar with corticosteroids in the context of their use in conditions such as cerebral edema, asthma, acute respiratory distress syndrome, and in the prevention of postoperative nausea and vomiting. In recent years, the use of these drugs has gained prominence in the management of patients with Duchenne muscular dystrophy (DMD). Although reviews of DMD have been published in the anesthesia literature, none has discussed the effects of corticosteroids on the course of this debilitating disease (1,2). This review will focus on the role of corticosteroids and their implications for anesthetic management in DMD.

Obstetrical and Pediatric Anesthesia Anesthetic management of children with Moebius sequence

BackgroundMoebius sequence is a rare congenital absence of the sixth and seventh cranial nerves, although there may be additional congenital cranial neuropathies. Developmental delay, cardiac and musculoskeletal abnormalities may also coexist. Oro-facial manifestations include bilateral facial nerve palsy resulting in a mask like facies, drooling, incomplete eye closure, and strabismus secondary to the extra-ocular muscle imbalance. This condition has multiple implications for anesthetic care.MethodsWe reviewed III anesthesia records of 46 patients with Moebius sequence for anesthesia technique and related complications.ResultsFacial nerve palsy was universally present and bilateral in 44 (93.6%) patients. Thirty-two (68%) had concomitant sixth nerve palsy. Oro-facial and limb abnormalities were present in 16 (35%) and 18 (39%) of patients respectively. Endotracheal intubation, when attempted, was easy in 76 of 106 cases. Tracheal intubation was consistently difficult in seven patients and intubation failure occurred in a single patient only. Statistically significant factors associated with difficult tracheal intubation included structural abnormalities of the mandible and palate and abnormalities of four cranial nerves (IX, X, XI, XII).ConclusionWe confirm that tracheal intubation may be difficult in patients with Moebius sequence. We identify disease features that might predict a difficult tracheal intubation and thus allow the anesthesiologist an opportunity to plan accordingly.RésuméHistoriqueLe syndrome de Moebius, paralysie congénitale rare des nerfs crâniens VI et VII, est parfois accompagné ďautres neuropathies crâniennes congénitales. Un retard de développement, des anomalies cardiaques et musculo-squelettiques peuvent aussi coexister.Au niveau du visage, on note la paralysie bilatérale du nerf facial, qui entraîne le manque ďexpression, ľhypersalivation, la fermeture incomplète des yeux et le strabisme secondaire au déséquilibre du muscle de ľorbite.MéthodeNous avons passé en revue III dossiers anesthésiques de 46 patients atteints du syndrome de Moebius et noté la technique utilisée et les complications rapportées.RésultatsLa paralysie du nerf facial était toujours présente, et bilatérale chez 44 (93,6 %) patients. Trente-deux (68 %) enfants avaient aussi uneparalysie du nerf VI.Les anomalies oro-faciales et des membres étaient respectivement présentes chez 16 (35 %) et 18 (39 %) des patients.Ľintubation endotrachéale, si elle était tentée, était facile dans 76 des 106 cas.Elle était régulièrement difficile chez sept patients et impossible chez un seul.Les facteurs statistiquement significatifs liés aux difficultés ďintubation comptaient des anomalies de la mandibule et du palais et des nerfs crâniens IX, X, XI, XII.ConclusionĽintubation endotrachéale peut être difficile chez des patients atteints dusyndrome de Moebius.Nous avons repéré des caractéristiques de la maladie qui pourraient aider à prédire ces difficultés et à préparer ľanesthésie en conséquence.

Anesthetic care of parturients with single ventricle physiology

Understanding the management of the parturient with single ventricle physiology starts with knowledge of the lesion, the patients current stage of surgical palliation, her current functional status, and the impact of pregnancy and labor on her cardiac physiology. A multidisciplinary team approach, described in this article, is crucial to a positive outcome.

Local anaesthesia for laminectomy surgery

Neurosurgical patients presenting for laminectomy surgery may have premorbid pathology that either contraindicates general anaesthesia or at least represents a significant risk to the patient. We present a sample case from a series of ten patients in whom laminectomy surgery was performed under local anaesthesia. The mean duration of surgery was 98 minutes and the average dose of lignocaine used was 1.91 mg/kg and, therefore, within safe limits. One patient was converted to a general anaesthetic. We believe that local anaesthesia can offer a safe and satisfactory alternative, in patients who may otherwise be denied surgery. The additional advantage of awake neuro-monitoring, may also reduce the risk of inadvertant spinal cord injury.

3-Factor Prothrombin Complex Concentrates in Infants With Refractory Bleeding After Cardiac Surgery

From the *Department of Anesthesiology, Duke Children’s Pediatric and Congenital Heart Center, Duke University, Durham, NC; †Department of Anesthesiology, Duke University, Durham, NC; ‡Department of Surgery, Division of Cardiovascular and Thoracic Surgery, Duke Children’s Pediatric and Congenital Heart Center, Duke University, Durham, NC; and §Department of Anesthesiology, Division of Adult Cardiothoracic Anesthesiology and Critical Care Medicine, Duke University, Durham, NC. Address reprint requests to Edmund Jooste, MBChB, Department of Pediatric Anesthesiology, Duke University Medical Center Box 3094, Durham, NC, 27710. E-mail: Edmund.jooste@duke.edu

A change in anticoagulation monitoring improves safety, reduces transfusion, and reduces costs in infants on cardiopulmonary bypass

An immature coagulation system coupled with the hypothermia and hemodilution associated with cardiopulmonary bypass (CPB) in infants makes the activated clotting time (ACT) an ineffective monitor for anticoagulation in this population. The Medtronic HMS Plus Hemostasis Management System (HMS; Medtronic, Inc., Minneapolis, MN, USA) is shown to decrease thrombin generation and blood product requirements.

Sedation and restraint practices in UK paediatric intensive cares: a telephone survey

paralytic ileus. An ileal strictoplasty was performed and small bowel adhesions were divided. On his day 14 postoperatively, he was discharged home. Further injuries at the time of the accident included a fracture of L3 and skin lacerations. Discussion Major trauma in children is fortunately rare, but it is known to be the commonest cause of death in children above 1 year of age in the developed world. While large bowel injury is known to occur at any impact velocity, small bowel injury is usually a result of high velocity impacts and is reported in 10±16% of patients sustaining blunt abdominal trauma. Associated injuries are common and contribute to the mortality rate, which is reported to be 25% or more. In some cases, symptoms can be minimal, diagnosis might be dif®cult and patients might present later with peritonitis or ileus symptoms; other patients can present with intraperitoneal bleeding requiring immediate lifesaving surgery. It is possible to manage patients with such injuries in a District Hospital.