James P. Spaeth

Brain magnetic resonance imaging abnormalities after the Norwood procedure using regional cerebral perfusion

OBJECTIVES Neurologic deficits are common after the Norwood procedure for hypoplastic left heart syndrome. Because of the association of deep hypothermic circulatory arrest with adverse neurologic outcome, regional low-flow cerebral perfusion has been used to limit the period of intraoperative brain ischemia. To evaluate the impact of this technique on brain ischemia, we performed serial brain magnetic resonance imaging in a cohort of infants before and after the Norwood operation using regional cerebral perfusion. METHODS Twenty-two term neonates with hypoplastic left heart syndrome were studied with brain magnetic resonance imaging before and at a median of 9.5 days after the Norwood operation. Results were compared with preoperative, intraoperative, and postoperative risk factors to identify predictors of neurologic injury. RESULTS Preoperative magnetic resonance imaging (n = 22) demonstrated ischemic lesions in 23% of patients. Postoperative magnetic resonance imaging (n = 15) demonstrated new or worsened ischemic lesions in 73% of patients, with periventricular leukomalacia and focal ischemic lesions occurring most commonly. Prolonged low postoperative cerebral oximetry (<45% for >180 minutes) was associated with the development of new or worsened ischemia on postoperative magnetic resonance imaging (P = .029). CONCLUSIONS Ischemic lesions occur commonly in neonates with hypoplastic left heart syndrome before surgery. Despite the adoption of regional cerebral perfusion, postoperative cerebral ischemic lesions are frequent, occurring in the majority of infants after the Norwood operation. Long-term follow-up is necessary to assess the functional impact of these lesions.

Handoff checklists improve the reliability of patient handoffs in the operating room and postanesthesia care unit

Ineffective communications among healthcare providers are common and increases the risk of medical errors. During the perioperative period, multiple handoffs occur within a short period of time, and failure to convey important patient information can compromise safety. We used quality improvement methodology to improve the reliability of our handoffs in the operating room and postanesthesia care unit (PACU).

Glucose and heart surgery: neonates are not just small adults.

DESPITE the many advances in cardiac surgery, neurologic complications continue to be recognized postoperatively. Cognitive deficits appear in about one-half of adults after coronary artery bypass grafting and in as many as one-third of children after neonatal heart surgery. Preoperative, intraoperative, and postoperative episodes of hypoxia-ischemia all seem to contribute to these complications. Hyperglycemia has been shown to worsen neurologic injury in adult ischemia models. Given the risk of ischemic neurologic injury in neonatal heart surgery and the role of hyperglycemia in ischemic brain injury in adults, de Ferranti et al. ’s examination of the relationship of blood glucose to neurologic outcome after neonatal heart surgery, published in this issue of the Journal, addresses an important and timely question. To appreciate the distinction between neonates and adults, it is useful to briefly review their differences in whole body and brain glucose metabolism. During development, brain metabolism changes markedly. Glucose crosses the blood-brain barrier through transporter proteins (GLUT1), and then enters the cell through a second glucose transporter system (GLUT3). Glycolysis then begins with the phosphorylation of glucose by hexokinase I. GLUT3 and hexokinase I increase fivefold from neonate to adult as cerebral metabolic rate increases. The developmental increase in cerebral glucose metabolic rate corresponds with an increase in synaptic activity, synaptogenesis, and myelination of specific brain regions. Cerebral glucose metabolism yields adenosine triphosphate, which provides energy to maintain ion gradients, support synaptic activity, and preserve cellular homeostasis. Unlike the adult brain, the neonatal brain is able to metabolize ketone bodies (acetoacetate and D-3hydroxybutyrate) and free fatty acids to generate adenosine triphosphate under physiologic conditions. The neonatal brain is also able to metabolize lactate to generate adenosine triphosphate for up to 60% of its energy requirements. Lactate permeability across the bloodbrain barrier is greater in neonates compared with adults, thus supporting brain lactate metabolism and limiting its build-up. During ischemia, the neonatal brain is able to use alternative substrates such as lactate and glycogen for energy. A wealth of information from animal models and clinical studies implicates hyperglycemia to be detrimental to the adult brain during global and focal ischemia. Although hyperglycemia supports adenosine triphosphate production through glycolysis and delays cellular energy failure during ischemia, the resultant lactic acidosis seems to be toxic to several intracellular processes, thereby hastening cell death and poisoning the repair mechanism of surviving cells. In contrast to the adult, hyperglycemia in the neonate seems to protect the brain from ischemic damage. In a neonatal rat model of hypoxia-ischemia, Vannucci et al. found that low-dose glucose treatment yielding mild hyperglycemia (270–360 mg/dl) did not exacerbate brain damage; unexpectedly, glucose treatment yielding moderate hyperglycemia (630–720 mg/dl) ameliorated the brain damage in this model. Studies in neonatal pigs involving hypothermic low-flow cardiopulmonary bypass or deep hypothermic circulatory arrest also demonstrated less brain damage with higher glucose levels. There are several reasons why hyperglycemia may help the neonatal brain. First, hyperglycemia increases cerebral high-energy reserves and glycogen stores. As a result, high-energy phosphates are sustained longer during ischemia in hyperglycemic compared to normoglycemic neonatal animals. Second, glucose uptake and metabolism is slower and lactate accumulates slower in the neonatal brain compared with the adult brain. Third, lactate clearance is enhanced, thereby avoiding the toxicity of lactacidosis. Although many studies have related serum glucose levels to ischemic neurologic outcome in adults, only one clinical study pertains to cardiac surgery. Ceriana et al. found that hyperglycemia was associated with adverse neurologic outcome in adults undergoing aortic arch reconstruction. As a result, many cardiac anesthesiologists treat hyperglycemia based on clinical studies of stroke or cardiac arrest and animal studies of ischemia. For pediatric cardiac surgery, the role of hyperglycemia in neurologic injury is even less clear. At the same time, neonates are at additional risk for hypoglycemic neurologic injury. In neonates, hypoglycemia during fasting or illness is This Editorial View accompanies the following article: de Ferranti S, Gauvreau K, Hickey PR, Jonas RA, Wypij D, du Plessis A, Bellinger DC, Kuban K, Newburger JW, Laussen PC: Intraoperative hyperglycemia during infant cardiac surgery is not associated with adverse neurodevelopmental outcomes at 1, 4, and 8 years. ANESTHESIOLOGY 2004; 100:1345–52.

Protection of tongue from injuries during transcranial motor-evoked potential monitoring.

3 months to 6 years, Wang et al. (4) had compared correlations between the ID of an uncuffed oral tube and child’s age, weight, height, head girth and circumference of the right fifth finger of the child. They found that height had the best correlation to the size of a tube, and suggested that a height-based formula, ID (mm) = 2 + [height (cm) ⁄ 30], was applicable to Chinese children. Moreover, it is generally believed that when used individually, single variables such as age, height and weight are less predictive (5). Therefore, we think that prediction of the corrected tube sizes in children is best accomplished using multiple variables. Eck et al. (5) have recommended that for any child aged up to 7 years, tube size is represented by the formula: 2.44 + (age · 0.1) + (height · 0.02) + (weight · 0.016). Although this results in a complex formula, this may be overcome with the use of computers in the operating theatre. Past published data on guidelines or formulae for selecting tube size in children were based on Western children measurements. We have noted that the choice of tube size for children may be different between Eastern and Western children of the same age group (2,4–7), because body build is generally different between them. Thus the guidelines of the choice of the tube size for children of different race are also needed. These problems deserve further study. Considering the significant difficulty in the choice of the most suitable tube size for a child, we always have readily available tubes one size larger and one size smaller than the one chosen on the basis of age before intubation is attempted. If a difficult intubation is anticipated, a smaller tube is always used. Fu Shan Xue Ya Chao Xu Xu Liao Yan Ming Zhang Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100144, China (email: fruitxue@yahoo.com.cn)

Interventions designed using quality improvement methods reduce the incidence of serious airway events and airway cardiac arrests during pediatric anesthesia

Although serious complications during pediatric anesthesia are less common than they were 20 years ago, serious airway events continue to occur. Based on Quality Improvement (QI) data from our institution, a QI project was designed to reduce the incidence of serious airway events and airway cardiac arrests.

Assessment and Management of the Pediatric Airway

Anatomic features that differ between children and adults include (1) a proportionally larger head and occiput (relative to body size), causing neck fl exion and leading to potential airway obstruction when lying supine; (2) a relatively larger tongue, decreasing the size of the oral cavity; (3) decreased muscle tone, resulting in passive obstruction of the airway by the tongue; (4) a shorter, narrower, horizontally positioned, softer epiglottis; (5) cephalad and anterior position of the larynx; (6) shorter, smaller, narrower trachea; and (7) funnel-shaped versus cylindrical airway, such that the narrowest portion of the airway is located at the level of the cricoid cartilage (Figure 24.1). The fi rst and perhaps most obvious difference is that the pediatric airway is much smaller in diameter and shorter in length than the adult’s. For example, the length of the trachea changes from approximately 4 cm in neonates to approximately 12 cm in adults, and the tracheal diameter varies from approximately 3 mm in the premature infant to approximately 25 mm in the adult [11,13]. According to Hagen-Poiseuille’s law, the change in air fl ow resulting from a reduction in airway diameter is directly proportional to the airway radius elevated to the fourth power:

Perioperative Management of DORV

The diagnosis of double-outlet right ventricle (DORV) characterizes a complex heterogeneous group of congenital cardiac malformations for which multiple classification schemes have been used. A clear understanding of the anatomy is critical to understanding the physiologic consequences of the specific type of DORV. Perioperative considerations include the medical management of the patient during the preoperative period, anesthetic and surgical management, and postoperative care. Both anesthetic and surgical management strategies are very different depending on the type of DORV. Key principles for anesthetic management include balancing the systemic and pulmonary circulations, optimizing systemic cardiac output, and closely monitoring for impaired oxygen delivery to the tissues. Depending on the specific anatomy the patient is usually placed on a 1- or 2-ventricle pathway, and initial palliation may involve placement of a systemic arterial to pulmonary artery shunt or pulmonary artery banding. In some cases the child may undergo a complete repair during the first few months of life. Surgical outcomes, both short and long-term, are dependent on the type of DORV and surgical procedure done. These patients require long-term follow up and may present for surgical or catheter-based interventions as adults.

Case discussion and root cause analysis: bupivacaine overdose in an infant leading to ventricular tachycardia.

An otherwise healthy 11-month-old, 8-kg infant presented for an elective circumcision. After a penile block with an excessive dose of 0.5% bupivacaine, the patient progressed to ventricular tachycardia. He was resuscitated with intralipid and had an uneventful recovery. The case was classified as a serious safety event, and a team was created to perform a root cause analysis. A sequence of events was constructed from gathered data, and policies and procedures were reviewed. Proximate cause was determined to be the failure of the surgeon, anesthesiologist, nurse, and scrub technician to communicate about the maximum dose of local anesthetic allowed before the medication being drawn up. Interventions were developed to target the proximate and contributing causes.

Patient safety in pediatric anesthesia: developing a system to improve perioperative outcomes.

1. Provide background information regarding safety in anesthesia. 2. Introduce the systems model of human error. 3. Describe development of a system of patient safety. 4. Identify barriers to improving safety. 5. Describe methods for reporting serious safety and adverse events. 6. Outline safety and adverse event analysis. 7. Describe categorization and tracking of serious safety and adverse events. 8. Discuss the use of quality improvement methods to improve safety.

The Extremely Premature Infant (Micropremie) and Common Neonatal Emergencies

Abstract The preterm infant, defined as birth before 37 weeks gestation, provides unique medical and surgical challenges to health care providers due to a myriad of anatomical underdevelopments and physiologic derangements. The physiology of prematurity as it relates to anesthesia is of particular importance when preparing for surgery. Anatomic differences of the premature airway and altered respiratory mechanics, such as a smaller airway diameter, increased oxygen consumption, bronchopulmonary dysplasia and apnea place these infants at risk for rapid and profound desaturation and hypoventilation during anesthesia. The immature heart has not had time to develop sufficient muscle fibers for optimal contractility. In addition, persistent pulmonary hypertension of the newborn may develop when right-to-left shunting of blood occurs through a patent ductus arteriosus and/or a patent foramen ovale due to failure of the pulmonary vascular resistance to drop at birth. These factors may combine and lead to significant cardiovascular collapse during surgery. Premature infants are susceptible to metabolic derangements such as hypoglycemia and hypocalcemia due to improper storage and loss of maternal-fetal transfer during gestation. The liver and kidneys are underdeveloped, leading to altered drug metabolism, thus, anesthetic drugs must be tailored accordingly. Neonatal surgical emergencies, such as congenital diaphragmatic hernia, hypertrophic pyloric stenosis, necrotizing enterocolitis and gastroschisis, can present at any time and be life-threatening. Immediate surgical intervention is not always necessary and there is often time for medical optimization. Advances in neonatal care have improved the morbidity and mortality of critically ill newborns.