James A. DiNardo

High dose dexmedetomidine as the sole sedative for pediatric MRI

Objective:  This large‐scale retrospective review evaluates the sedation profile of dexmedetomidine.

Clinical comparison of sevoflurane and isoflurane in healthy patients

&NA; We compared blood pressure and heart rate changes in healthy patients during anesthesia with sevoflurane (n = 50) versus isoflurane (n = 25) and the rate of recovery after such anesthesia. After premedication with intravenous administration of midazolam, induction of anesthesia with thiopental, and intubation of the trachea facilitated with succinylcholine or vecuronium, anesthesia was maintained with approximately 1 MAC (sevoflurane, 2.05%; isoflurane, 1.15%) of the volatile anesthetic in oxygen for the duration of the operation. Anesthetic concentration was varied as indicated to maintain arterial blood pressure at ±20% of baseline values. Sevoflurane and isoflurane produced similar systolic and diastolic arterial blood pressures, but heart rate after incision was faster in patients given isoflurane. Recovery of response to command was shorter in patients given sevoflurane than that in patients given isoflurane (7.5 ± 0.5 min versus 18.6 ± 2.0 min). Consistent with this finding, venous blood drawn after anesthesia showed a more rapid initial decay with sevoflurane. Nausea and vomiting were comparable in both groups. We conclude that sevoflurane anesthesia, as compared with isoflurane, is associated with possible advantageous effects on heart rate and recovery.

Cardiovascular Effects of Sevoflurane Compared with Those of Isoflurane in Volunteers

Background Sevoflurane is a new inhalational anesthetic with desirable clinical properties. In some clinical situations, an understanding of the detailed cardiovascular properties of an anesthetic is important, so the authors evaluated the hemodynamic effects of sevoflurane in healthy volunteers not undergoing surgery.

Microstream Capnography Improves Patient Monitoring During Moderate Sedation: A Randomized, Controlled Trial

BACKGROUND. Investigative efforts to improve monitoring during sedation for patients of all ages are part of a national agenda for patient safety. According to the Institute of Medicine, recent technological advances in patient monitoring have contributed to substantially decreased mortality for people receiving general anesthesia in operating room settings. Patient safety has not been similarly targeted for the several million children annually in the United States who receive moderate sedation without endotracheal intubation. Critical event analyses have documented that hypoxemia secondary to depressed respiratory activity is a principal risk factor for near misses and death in this population. Current guidelines for monitoring patient safety during moderate sedation in children call for continuous pulse oximetry and visual assessment, which may not detect alveolar hypoventilation until arterial oxygen desaturation has occurred. Microstream capnography may provide an “early warning system” by generating real-time waveforms of respiratory activity in nonintubated patients. OBJECTIVE. The aim of this study was to determine whether intervention based on capnography indications of alveolar hypoventilation reduces the incidence of arterial oxygen desaturation in nonintubated children receiving moderate sedation for nonsurgical procedures. PARTICIPANTS AND METHODS. We included 163 children undergoing 174 elective gastrointestinal procedures with moderate sedation in a pediatric endoscopy unit in a randomized, controlled trial. All of the patients received routine care, including 2-L supplemental oxygen via nasal cannula. Investigators, patients, and endoscopy staff were blinded to additional capnography monitoring. In the intervention arm, trained independent observers signaled to clinical staff if capnograms indicated alveolar hypoventilation for >15 seconds. In the control arm, observers signaled if capnograms indicated alveolar hypoventilation for >60 seconds. Endoscopy nurses responded to signals in both arms by encouraging patients to breathe deeply, even if routine patient monitoring did not indicate a change in respiratory status. OUTCOME MEASURES. Our primary outcome measure was patient arterial oxygen desaturation defined as a pulse oximetry reading of <95% for >5 seconds. Secondary outcome measures included documented assessments of abnormal ventilation, termination of the procedure secondary to concerns for patient safety, as well as other more rare adverse events including need for bag-mask ventilation, sedation reversal, or seizures. RESULTS. Children randomly assigned to the intervention arm were significantly less likely to experience arterial oxygen desaturation than children in the control arm. Two study patients had documented adverse events, with no procedures terminated for patient safety concerns. Intervention and control patients did not differ in baseline characteristics. Endoscopy staff documented poor ventilation in 3% of all procedures and no apnea. Capnography indicated alveolar hypoventilation during 56% of procedures and apnea during 24%. We found no change in magnitude or statistical significance of the intervention effect when we adjusted the analysis for age, sedative dose, or other covariates. CONCLUSIONS. The results of this controlled effectiveness trial support routine use of microstream capnography to detect alveolar hypoventilation and reduce hypoxemia during procedural sedation in children. In addition, capnography allowed early detection of arterial oxygen desaturation because of alveolar hypoventilation in the presence of supplemental oxygen. The current standard of care for monitoring all patients receiving sedation relies overtly on pulse oximetry, which does not measure ventilation. Most medical societies and regulatory organizations consider moderate sedation to be safe but also acknowledge serious associated risks, including suboptimal ventilation, airway obstruction, apnea, hypoxemia, hypoxia, and cardiopulmonary arrest. The results of this controlled trial suggest that microstream capnography improves the current standard of care for monitoring sedated children by allowing early detection of respiratory compromise, prompting intervention to minimize hypoxemia. Integrating capnography into patient monitoring protocols may ultimately improve the safety of nonintubated patients receiving moderate sedation.

TEG and ROTEM: Technology and clinical applications

Initially described in 1948 by Hertert thromboelastography (TEG) provides a real‐time assessment of viscoelastic clot strength in whole blood. Rotational thromboelastometry (ROTEM) evolved from TEG technology and both devices generate output by transducing changes in the viscoelastic strength of a small sample of clotting blood (300 µl) to which a constant rotational force is applied. These point of care devices allow visual assessment of blood coagulation from clot formation, through propagation, and stabilization, until clot dissolution. Computer analysis of the output allows sophisticated clot formation/dissolution kinetics and clot strength data to be generated. Activation of clot formation can be initiated with both intrinsic (kaolin, ellagic acid) and extrinsic (tissue factor) activators. In addition, the independent contributions of platelets and fibrinogen to final clot strength can be assessed using added platelet inhibitors (abciximab and cytochalasin D). Increasingly, ROTEM and TEG analysis is being incorporated in vertical algorithms to diagnose and treat bleeding in high‐risk populations such as those undergoing cardiac surgery or suffering from blunt trauma. Some evidence suggests these algorithms might reduce transfusions, but further study is needed to assess patient outcomes. Am. J. Hematol. 89:228–232, 2014.

Relationship of Intraoperative Cerebral Oxygen Saturation to Neurodevelopmental Outcome and Brain Magnetic Resonance Imaging at 1 Year of Age in Infants Undergoing Biventricular Repair

Background— Near-infrared spectroscopy monitoring of cerebral oxygen saturation (rSo2) has become routine in many centers, but no studies have reported the relationship of intraoperative near-infrared spectroscopy to long-term neurodevelopmental outcomes after cardiac surgery. Methods and Results— Of 104 infants undergoing biventricular repair without aortic arch reconstruction, 89 (86%) returned for neurodevelopmental testing at 1 year of age. The primary near-infrared spectroscopy variable was the integrated rSo2 (area under the curve) for rSo2 ≤45%; secondary variables were the average and minimum rSo2 by perfusion phase and at specific time points. Psychomotor and mental development indexes of the Bayley scales, head circumference, neurological examination, and abnormalities on brain magnetic resonance imaging did not differ between subjects according to a threshold level for rSo2 of 45%. Lower Psychomotor Development Index scores were modestly associated with lower average (r=0.23, P=0.03) and minimum (r=0.22, P=0.04) rSo2 during the 60-minute period after cardiopulmonary bypass but not with other perfusion phases. Hemosiderin foci on brain magnetic resonance imaging were associated with lower average rSo2 from postinduction to 60 minutes post cardiopulmonary bypass (71±10% versus 78±6%, P=0.01) and with lower average rSO2 during the rewarming phase (72±12% versus 83±9%, P=.003) and during the 60-minute period following cardiopulmonary bypass (65±11% versus 75±10%, P=0.009). In regression analyses that adjusted for age ≤30 days, Psychomotor Development Index score (P=0.02) and brain hemosiderin (P=0.04) remained significantly associated with rSo2 during the 60-minute period following cardiopulmonary bypass. Conclusions— Perioperative periods of diminished cerebral oxygen delivery, as indicated by rSo2, are associated with 1-year Psychomotor Development Index and brain magnetic resonance imaging abnormalities among infants undergoing reparative heart surgery. Clinical Trial Registration— URL: http://clinicaltrials.gov. Unique identifier: NCT00006183.

Anaesthesia considerations for cardiac MRI in infants and small children.

Background : General anaesthesia is frequently necessary in infants and small children undergoing cardiac magnetic resonance imaging (MRI), because of the imaging techniques, MRI environment and potential need for breath‐holding to facilitate imaging. Anaesthetizing paediatric patients with congenital heart disease (CHD) for cardiac MRI poses many challenges for the anaesthetist and this report reviews our experience.

Procoagulant and anticoagulant factor abnormalities following the fontan procedure: increased factor VIII may predispose to thrombosis

OBJECTIVE Using age-matched controls, this study prospectively evaluated coagulation factor abnormalities and hemodynamic variables in children who had undergone the Fontan operation. METHODS Coagulation factors were assayed in 20 children (mean age 6.4 +/- 2.9 years), at a mean 3.7 +/- 2.3 years after the Fontan procedure; 24 healthy children (mean age 6.8 +/- 2.8 years) were assayed as controls. Concentration of factors II, V, VII, VIII, IX, X; ATIII; plasminogen; proteins C and S; fibrinogen; serum albumin; and liver enzymes were measured. Normal reference intervals based on the control patients were determined using 95% confidence limits. Patient demographic, hemodynamic variables, and elapsed time after the Fontan procedure were evaluated as possible predictors of coagulation abnormalities. RESULTS Concentrations of protein C; factors II, V, VII, X; plasminogen; and ATIII were significantly lower in Fontan patients compared with age-matched controls (P <.01); factor VIII was significantly elevated in 6 patients (35%), 2 of whom had a thromboembolic event. A higher superior vena cava pressure was predictive of an elevated factor VIII level (P =.003). No other specific hemodynamic variables were predictive of a procoagulant or anticoagulant abnormality. CONCLUSION Procoagulant and anticoagulant factor levels were significantly lower in patients after the Fontan operation independent of hemodynamic variables peculiar to the Fontan circulation. Increased factor VIII level requires further evaluation as a cause of thrombosis in patients with Fontan physiology and may also indicate a subset of these patients in whom anticoagulation is indicated.

Prospective longitudinal study of coagulation profiles in children with hypoplastic left heart syndrome from stage I through Fontan completion

OBJECTIVE The risk for thrombosis is increased after the Fontan operation. It is unknown whether children with univentricular heart disease have an intrinsic coagulation anomaly or acquire a defect in coagulation during the course of the staged repair. This prospective, longitudinal study evaluated changes in coagulation profiles in a cohort of patients with hypoplastic left heart syndrome from stage I palliation through completion of the Fontan operation. METHODS Thirty-seven patients with hypoplastic left heart syndrome were enrolled prospectively, and the concentration of factors II, V, VII, VIII, IX, X, proteins C and S, fibrinogen, antithrombin, serum albumin, and liver enzymes were measured before stage I palliation (mean age 4 +/- 2 days), before bidirectional Glenn (mean age 5.9 +/- 1.8 months), before the Fontan procedure (mean age 27.1 +/- 6.6 months), and after the Fontan procedure (mean age 49 +/- 17.6 months). Healthy children were used as age-matched controls for coagulation factors. Demographic, hemodynamic variables, and elapsed time after the Fontan procedure were evaluated as possible predictors of coagulation abnormalities. RESULTS Significantly lower levels of both procoagulation and anticoagulation factors were demonstrated through to completion of the Fontan procedure. After the Fontan procedure, there was a significantly higher factor VIII level (P < .005) but no correlation with hemodynamic variables or liver function. CONCLUSION This longitudinal study in patients with identical cardiac disease and staged surgical procedures confirms the increase in factor VIII level after the Fontan procedure. This is an acquired defect, and although the cause remains to be determined, monitoring factor VIII levels after the Fontan operation could indicate a subset of patients at risk for thrombosis.

Congenital supravalvular aortic stenosis and sudden death associated with anesthesia: what's the mystery?

Patients with congenital supravalvular aortic stenosis and associated peripheral pulmonary artery stenoses, the majority of whom have Williams-Beuren syndrome, are inherently at risk for development of myocardial ischemia. This is particularly true in the setting of procedural sedation and anesthesia. The biventricular hypertrophy that accompanies these lesions increases myocardial oxygen consumption and compromises oxygen delivery. In addition, these patients often have direct, multifactorial compromise of coronary blood flow. In this article, we review both the pathophysiology of congenital supravalvular aortic stenosis and the literature regarding sudden death in association with sedation and anesthesia. Recommendations as to preoperative assessment and management of these patients are made based on the best available evidence.