Pediatric Anesthesia: A Guide for the Non-Pediatric Anesthesia Provider E-Book
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- Herausgeber: Bentham Science Publishers
- Kategorie: Fachliteratur
- Sprache: Englisch
Pediatric Anesthesia: A Guide for the Non-Pediatric Anesthesia is a comprehensive, contemporary reference that addresses all aspects of pediatric anesthesia. Both students and medical practitioners – novice and experienced - will find invaluable educational and practical information in this book. The book covers the subject in two parts.
Part I covers basic information about pediatric and neonatal anatomy and physiology, pharmacology, emergency room and operating room procedures and surgery. Chapters on general anesthetic procedures in emergency rooms, operational theatres and common surgeries.
Part II covers advanced topics for practicing healthcare professionals which include anesthesia for patients with a range of common and uncommon comorbidities, considerations for critically-ill patients, genetic disorders, pain management, COVID-19 guidelines for anesthesia, patient safety and research.
Key features:
- Basic and advanced information about pediatric and neonatal anesthesia covered in 25 chapters over two parts
- Simple and organized presentation for learners
- Contributions by expert clinicians and researchers
- Special topics included such as considerations for patients with comorbidities and genetic disorders
- References for further reading
- Detailed illustrations and tables
The text is an essential reference for scholars and professionals affiliated with general anesthesiology and surgery specialties at all levels who want to understand anesthesia for pediatric patients.
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Seitenzahl: 672
Veröffentlichungsjahr: 2001
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PREFACE
Bharathi GourkantiI have been practicing the art and science of anesthesia for almost three decades, and for the past 23 years as a pediatric anesthesiologist. It is my strong belief that providing anesthesia for children is not just a job; it is a privilege. Parents trust anesthesia providers with their child’s life, which they value more than their own lives. Guarding a child’s life, taking charge of their care, and handing them back safely to their family is a great honor and an immense responsibility. When I was approached to edit a textbook on pediatric anesthesia, I did not wish to produce a formal or standard text, but to make it more informative, clinically oriented, practical, and user-friendly.
WHO THIS BOOK IS WRITTEN FOR
Though this is written for general anesthesia providers who occasionally are required to provide pediatric anesthesia, many others who provide pediatric anesthesia, sedation, pain control, resuscitation, or emergency care may also benefit. This book is an excellent starting point for providers in training, and a handy clinical reference for those who are many years into clinical practice. Our goal is to provide a source with the most critical and clinically relevant information that can be easily referenced by a busy practitioner in the middle of the night.
WHO CONTRIBUTED TO THIS BOOK
Every member of the anesthesia care team has a unique perspective and an abundance of knowledge to share. Our editors and contributors include board-certified pediatric anesthesiologists, general anesthesiologists who occasionally treat children, pediatric anesthesia fellows in training, anesthesia residents, and certified registered nurse anesthetists. Our collective knowledge and teamwork have given this text its unique and approachable voice.
WHAT IS IN THIS BOOK
Our goal in this book was to present the scientific data as it relates to current clinical practice in an approachable and easily understood fashion. The information presented ranges from basic topics that will be useful for residents and nurses preparing for their exams, to a comprehensive analysis of the current controversies and common practices in pediatric anesthesia. We summarize the information into tables, figures, and illustrations where possible for easy reference. We review the key differences in a pediatric patient’s anatomy, physiology, and pharmacology for those providers accustomed to treating adults, and outline how to modify anesthetic techniques accordingly. We highlight topics critical to the safe perioperative care of infants and children. A thorough discussion of the management of common pediatric comorbidities is included, and commonly encountered anesthetic complications and their treatments are presented.
THANKS
I am extremely grateful to all the contributors for bringing their invaluable knowledge, various points of view, and unique expertise to this book.
I thank my co-editors Dr. Irwin Gratz, Dr. Grace Dippo, Dr. Nathalie Peiris and Dr. Dinesh K. Choudhry, for their knowledge, competence, patience, and scrupulous attention to detail to make this manuscript more meaningful.
My warmest thanks to Hira Aftab, Manager-Publications, and our Project Coordinator whose unrelenting support has helped make this project possible.
Finally, I would like to thank Bentham Science for providing the opportunity to create this body of work.
SUMMARY
In summary, we designed this book for all those who routinely or occasionally provide pediatric anesthesia with theoretical, clinical, and practical knowledge, and a readily available quick reference.
We sincerely hope this book will be of help to you in providing the safe practice of pediatric anesthesia.
List of Contributors
Anatomy and Physiology
Rachel Koehler1,Pravin Taneja2,Nathalie Peiris3Abstract
Knowing the anatomical differences between the pediatric patient and the adult patient are important for perioperative anesthetic care. This chapter will describe the head, neck, and airway anatomical differences in pediatric patients and their perioperative implications. In addition, this chapter will explore the physiology of different organ systems in the pediatric patient and the perioperative considerations for the anesthesia provider.
AIRWAY
The pediatric airway is unique compared to the adult airway. These differences at times can cause dire consequences when not in care of experienced hands [1]. See (Fig. 1) below for comparison.
Infants have a larger head size compared to their body causing difficulties with proper positioning. A shoulder roll is helpful to raise the shoulders to better align the oral, pharyngeal, and tracheal axises for a more optimized view [2]. The first thing a provider will notice is that the tongue of the infant is larger compared to the size of the oral cavity. This makes obstruction (particularly when doing a mask induction) more likely to occur and the anesthesia provider should be prepared to manage an obstructed airway. In addition, it makes it more difficult to
“sweep” it out of the way to obtain a view of the vocal cords. The epiglottis in children is narrow, omega-shaped, floppy, and long which makes it challenging to directly lift in order to obtain a good view of the vocal cords. The larynx is closer to the head (at the level of C3-4 versus C4-5) and appears to be more anterior compared to adults [3]. This produces a more acute angle between the different airway axises, making visualization more difficult. The anterior attachment of the vocal cords of an infant is also angled more caudally compared to an adult (which are attached perpendicular to the trachea) which may cause difficulty with guiding the endotracheal tube through the glottic opening. Due to these anatomic differences, a Miller blade is typically used over a Macintosh blade because it allows for better control and lift of the epiglottis and it is also able to move the large tongue out of the way [3-5]. The anesthesia provider managing the airway should also know that the narrowest part of the pediatric airway is the cricoid cartilage, in comparison to adults where it is the glottic opening. This is important because the endotracheal tube may pass through the glottic opening but encounter resistance in the subglottic region. It is thought that the differences in the subglottic region of the airway become similar to adults by the age of 10 [6].
Fig. (1)) Comparison of the pediatric and adult airways.This reported “funnel shaped” airway has led to the debate between using cuffed versus uncuffed endotracheal tubes in pediatric patients. The cricoid ring is the only complete ring of cartilage in the airway and thus, does not have any distensibility. The concern with cuffed endotracheal tubes is that the balloon will be overfilled, leading to mucosal ischemia, fibrosis, and edema to the surrounding anatomy causing inflammation and reduced airway diameter upon extubation. This would lead to post-extubation complications such as croup or subglottic stenosis. This is particularly concerning for the youngest population, where any decrease in airway diameter would increase airway resistance significantly. The benefits of an uncuffed endotracheal tube are the removal of the risk of the cuff causing mucosal trauma, and a larger internal diameter of the endotracheal tube which allows for easier suctioning and lower airway resistance [7]. However, drawbacks of an uncuffed endotracheal tube include increased risk of multiple tube exchanges due to inability to adequately ventilate secondary to an air leak. An adequate fit is when a leak occurs at an airway pressure of 15-25 cm of H2O pressure [8]. Multiple tube exchanges could lead to increased risk of trauma due to multiple airway manipulation attempts in addition to increasing operating room contamination due to leak of volatile anesthetics.
A Cochrane Review from 2017 which looked at the benefit of using a cuffed versus uncuffed endotracheal tube for general anesthesia in pediatric patients under 8 years old was not able to draw definite conclusions [9]. However, a meta- analysis done a year later did find that cuffed endotracheal tubes showed no difference in duration of intubation, reintubation occurrence, accidental extubation rate, croup occurrence and racemic epinephrine use during the intubation process and no increased rate of croup post-extubation [10].
Respiratory Physiology
The respiratory center in a neonate is not fully developed at birth. Neonates have an impaired response to hypoxia and hypercarbia. Preterm infants will typically have the paradoxical reaction of decreased respiratory rate and apnea in response to hypoxia and hypercapnia. An increased ventilatory drive does not occur in full term infants until after the first week of life. High concentration of inspired oxygen in a neonate also leads to depressed respiratory drive and complications such as retinopathy of prematurity and bronchopulmonary dysplasia due to the inability to break down oxygen free radicals. However, a low concentration of oxygen has been found to stimulate a neonate’s respiratory drive [11]. In addition, the medications used commonly in the anesthesia world can dull the response to hypercapnia and hypoxia [12]. Due to the combination of general anesthesia and a neonate’s immature response to hypoxia and hypercapnia, life-threatening apneas can occur in neonates - particularly in premature ones. This risk is typically highest in the first 12 hours postoperatively. This is why it is recommended to keep premature infants (those under 60 weeks post conceptual age) for overnight monitoring of postoperative apnea [6].
Infants are obligate nasal breathers. This is due to immature coordination between breathing and swallowing mechanisms. The ability to switch to oral breathing does not occur until 3-5 months [6]. Thus, it is important to remember to ensure nasal passages are clear because the infant may not have the ability to switch to oral breathing when its nasal passages are obstructed. One can do this by gentle nasal suctioning with a soft suction prior to induction and extubation.
The main purpose of the lungs is to oxygenate the blood and to ventilate carbon dioxide from the body [13, 14]. The pulmonary system overall is incomplete when a baby is first born and matures over a child’s development [15]. The lungs of an infant have less alveoli compared to adults. They also do not have the interconnections between them or as much elastic tissue around the alveoli which help prevent atelectasis [16-18]. Infants have defined tidal volumes which cannot change during inspiration due to their chest anatomy. The intercostal muscles are poorly developed and the ribs of pediatric patients are horizontally placed and result in significantly more chest wall compliance compared to adults. This increased chest wall compliance results in the infant relying solely on the diaphragm for inspiration - thus increasing the work of breathing for the infant. In addition, the diaphragm in the infant and neonate has proportionally less type 1 muscle fibers compared to an adult - which makes the younger population more prone to respiratory failure due to fatigue. Pediatric patients also have lower functional residual capacity (FRC) and smaller lung volumes compared to adults. This leads to a higher closing volume than FRC, which results in the premature closure of small airways. Pediatric patients compensate for this through different respiratory mechanics such as increased respiratory rate, quick expiratory times, and laryngeal adduction [3, 19-22]. However, under general anesthesia, these mechanics are ablated. During anesthesia, a provider should provide at least 5 cm H20 of PEEP in an attempt to avoid atelectasis and conserve FRC [23]. The ratio of their minute ventilation to their FRC is much higher than it is in an adult. They also have a much higher oxygen consumption rate at 7 mL/kg/min compared to an adult which is roughly 3 mL/kg/min [8]. All of these factors combined make an infant more susceptible to desaturation during induction of anesthesia at a much faster rate [11].
Inhalational induction is usually used for children versus intravenous induction due to difficulty getting an IV in an awake patient and the rate of induction is often quicker in this patient population. Lerman et al. found that blood-gas partition coefficients were about 18% less than those in adults with a p-value of <0.005. The fast rising rate of alveolar anesthetic partial pressure is due to multiple factors. Infants have an increased cardiac output per kg and have greater perfusion of vascular organs. As mentioned previously, they have a greater ratio of minute ventilation to their FRC and thus have a greater alveolar ventilation [24, 25].
Cardiac Physiology
The main role of the heart is to deliver oxygenated blood from the lungs to the various organs and tissues throughout the body. There are a multitude of structures, signals, and steps involved in the formation of the heart and vascular system. This process starts during the third week of gestation and is completed around the seventh week [26]. A provider should be aware that when something goes awry in one of these steps this could lead to a congenital heart defect. The incidence of congenital heart disease in the United States is roughly 1%, which is around 40,000 births per year [27, 28].
Fetal circulation, neonatal circulation, and adult circulation vary greatly from one another and every child must transition through each of these. During gestation (Fig. 2), oxygenated blood comes from the placenta via the umbilical vein. Half the oxygenated blood goes to the liver and supplies oxygen while the other half bypasses the liver via the ductus venosus and travels via the inferior vena cava to the right atrium. The oxygenated blood goes through the right atrium to the left atrium via the patent foramen ovale, down to the left ventricle and pumps oxygenated blood through the aorta, brain and upper half of the body. Deoxygenated blood comes from two sources; the inferior vena cava (bringing the deoxygenated blood from the lower half of the body) and the superior vena cava (bringing deoxygenated blood from the upper half of the body). This deoxygenated blood passes from the right atrium to the right ventricle and up to the pulmonary artery. However, pulmonary vascular resistance is high, causing blood to flow through the ductus arteriosus which connects the pulmonary artery to the descending aorta. Thus, deoxygenated blood bypasses the lungs, travels through the descending aorta (some supplying the lower half of the body with blood) to the umbilical artery back to the placenta for reoxygenation. Thus, the fetal circulation is said to run in parallel (with the left ventricle supplying oxygenated blood to the brain and upper half of body while the right ventricle supplying blood with less oxygen to the placenta and lower half of the body) [11].
Fig. (2)) Fetal circulation.Once a baby is born, their circulation must transition from fetal life to neonatal life (Fig. 3). When a baby takes their first breath this causes the pulmonary arterial pressure to dramatically decrease. After the placenta is separated from the baby this causes the systemic vascular resistance to increase. This leads to change in flow and helps to increase pulmonary artery blood flow and return of oxygenated blood to the left atrium. Ductus venosus narrows and decreases right atrium pressure. The increase in left atrium pressure compared to right atrium pressure results in functional closure of the patent foramen ovale. The rise in partial pressure of oxygen and decrease in prostaglandin production due to placenta removal causes constriction of the ductus arteriosus. This functionally closes in 24-48 hours and permanently closes after 4-8 weeks [11].
Fig. (3)) Neonatal circulation.The transitional period is very vulnerable and changes during the perioperative period could cause increase in pulmonary vascular resistance and reversal to fetal circulation. Factors that one must be mindful of include hypoxia, hypercarbia, hypothermia or acidosis in a neonate. These conditions can cause increased pulmonary vascular resistance and lead to right to left shunting through the ductus arteriosus. One way to monitor for this intraoperatively would be to place two pulse oximeters on a neonatal patient - one preductal such as the right hand and one post-ductal such as a lower extremity. An increase in 3% of oxygen saturation in a pre-ductal pulse oximeter compared to a post-ductal pulse oximeter indicates a right to left shunt [11]. Persistent fetal circulation and right to left shunting leads to decreased perfusion to systemic circulation resulting in peripheral tissue ischemia and a prolonged time for anesthesia induction via inhalational induction.
The newborn heart has less actin and myosin proteins and is less compliant than the adult heart. When a newborn heart has an increase of volume within their ventricles, it does not respond as well based on the well-known Frank-Starling curve due to the rigidity present. The main way an infant increases their cardiac output is through their heart rate which is why children are known to be heart rate dependent. See Table 1 below for normal hemodynamic values.
Renal Physiology
Renal function in a pediatric patient is not fully formed at birth. This is due to low renal perfusion pressure and immature glomerular and tubular function [33]. The kidneys play an important role with fluid, pH, electrolyte balance, and drug metabolism and excretion. Anesthesia providers should be aware that the pediatric population can experience decreased creatinine clearance, compromised electrolyte balance, and issues maintaining proper concentration of urine [34]. The newborn’s glomerular filtration rate (GFR) is low at around 40 ml/min/1.73 m2 and does not reach adult range until around two years of age [35]. Due to this immaturity of renal clearance, metabolism of many common drugs used during anesthesia is slowed which can lead to prolonged duration of action of medications. These drugs include antibiotics, narcotics, and neuromuscular blocking drugs. Thus, one could consider a pediatric patient as if he or she is similar to an adult patient with renal failure (in particular to antibiotic dosing and in conjunction with a pediatric pharmacist)-with longer intervals between redosing. In extremely premature patients, one can also consider using medications that completely bypass renal metabolism when possible such as cisatracurium for neuromuscular blockade. Since renal blood flow and GFR values are decreased in the pediatric population, fluids should not be carelessly given [36, 37]. Administration of fluids should be given in a volume-controlled device such as on an infusion pump or Buretrol.
Electrolyte disturbances occur due to decreased absorption in the renal tubules. This puts pediatric patients at risk for electrolyte derangements such as hyponatremia, hypoglycemia, and metabolic acidosis. Thus, if a pediatric child comes to the operating room with maintenance fluids or TPN, it is prudent to continue those fluids to avoid electrolyte disturbances.
Hematologic Physiology
Blood within our body is mainly made up of red blood cells, white blood cells, platelets, plasma, and proteins. The hematological system has a multitude of functions including delivering oxygen to different tissues, fighting infections, and hemostasis. The bone marrow is the main site of hematopoiesis at birth. When the infant is experiencing some type of stress, extramedullary enters can be seen in the liver, lymph nodes, spleen, and paravertebral regions [38, 39]. A clinician has to be mindful of the values of each cell line and how they differ from adults. Platelet counts in neonates are roughly the same as adults [40]. The average lymphocyte count is also within the range of adults [41]. A newborn is born with an average hemoglobin of 16.8 g/dL due to the production of fetal hemoglobin and adult hemoglobin A [6]. After a child is born, hemoglobin values start to fall due to decrease in fetal hemoglobin and slow increase of erythropoietin levels. This nadir is reached around 8-12 weeks of age and decreases to a hemoglobin level of 9.5-11 g/dL [42, 43]. Preterm infants have a quicker reduction and lower nadir values of hemoglobin compared to term infants [44]. This phenomenon is physiologic and occurs for a few reasons. In healthy adults, red blood cells have an average lifespan of 120 days. This timeline is cut in half in infants, where they will only last for 60-70 days. Preterm infants' red blood cells have an even shorter life span of 35-50 days. Preterm infants are also at a disadvantage because the majority of iron transfer from the mother occurs late in the last trimester [45, 46]. While the baby is in utero the oxygen saturation is around 50%. The oxygen saturation dramatically increases to 95% once the baby is born and takes their first breath. This causes a downregulation of erythropoietin which is the hormone that stimulates the production of red blood cells. During a child’s development the hemoglobin concentration gradually increases and reaches adult values at the age of adolescence [47]. Typical treatment of anemia is to limit blood draws or give blood transfusions [48].
Premature babies also may have an increased risk of bleeding due to decreased synthesis of vitamin K dependent coagulation factors and thrombocytopenia due to association with concerning neonatal pathologies such as retinopathy of prematurity, intraventricular hemorrhage, and sepsis [49]. One treatment that helps prevent intraventricular hemorrhage is vitamin K injection which is given prophylactically to babies when they are first born [50]. If a premature patient is scheduled for surgery, it is prudent to check a platelet count and coagulation levels in order to have the pertinent blood products available.
Gastrointestinal Physiology
The gastrointestinal and hepatic systems carry out many functions, including breaking down foods, processing and absorbing nutrients, metabolizing drugs, glucose control, and removal of waste [51, 52]. The gastrointestinal system is not fully formed at birth and intestinal motility is stimulated by enteral feeds. Breast milk has been shown to decrease common ailments a preterm infant may encounter such as necrotizing enterocolitis, retinopathy of prematurity, and sepsis [53-55]. Lactose is the main carbohydrate found in a baby’s diet and it is a disaccharide containing glucose and galactose.
Around 10% of healthy infants can experience hypoglycemia, and this rate can go even higher in premature, small for gestational age, intrauterine growth restriction, or babies of diabetic mothers. There are multiple processes behind this including decreased glycogen storage, increased energy demands, insufficient muscle mass which would provide amino acids for gluconeogenesis, and low-fat stores which would be used to make ketones [56-60]. The American Academy of Pediatrics defines hypoglycemia as < 47 mg/dL [61]. There are many signs and symptoms of hypoglycemia including diaphoresis, irritability, pallor, hunger, tachycardia, vomiting, apnea, hypotonia, seizures, and coma which could lead to death [62]. However, under general anesthesia, these symptoms are often masked. Oftentimes, due to the increased catecholamine release from stresses of surgery, pediatric patients may not require as much glucose supplementation. If an anesthesia provider is suspicious about hypoglycemia, one should immediately obtain a point-of-care glucose level which is quick and easy. Treatment is with intravenous dextrose [6].
The liver is the primary source of drug metabolism in the body. Functional hepatic metabolism does not reach adult levels until 1 year of age. This is due to immaturity of liver enzymes, reduction of hepatic proteins (such as albumin) and low hepatic perfusion pressure (which results in less drug delivery to the liver) [6]. All of these factors result in decreased drug metabolism and caution should be taken in the administration of medications that are highly protein bound (such as certain antibiotics, antiepileptics), or rely on perfusion-limited hepatic clearance (such as propofol or narcotics) in order to avoid toxicity. Another consideration would be to bypass hepatic metabolism altogether by using medications such as cisatracurium for neuromuscular blockade and remifentanil for opioids. More about pharmacodynamics will be discussed in the pharmacology chapter.
Temperature Physiology
Humans are normothermic and maintain an internal body temperature at ~37 degrees Celsius plus or minus 0.2 degrees Celsius [63]. Temperature is sensed by myelinated A-delta and unmyelinated C nerve fibers and travels along the spinothalamic tracts in the anterior spinal cord to convey information to the hypothalamus [64-66]. The hypothalamus is the primary regulator of internal body temperature. If body temperature is perceived to be above threshold, sweating and vasodilation will occur. Conversely, if body temperature is perceived to be below threshold, vasoconstriction, and shivering will occur [67].
The administration of general anesthesia changes this normal thermoregulation. Volatile anesthetics, propofol and narcotics such as morphine have vasodilatory effects and inhibit hypothalamic thermoregulation by decreasing the shivering threshold and increasing the sweating threshold as seen in Fig. (4) below.
Fig. (4)) Comparison of changes in thermogenesis under anesthesia.There are 3 phases of hypothermia under general anesthesia: rapid decline, slow decline, and steady state. The first phase involves redistribution of heat from the core to the periphery. This causes a 1-2 degree Celsius drop in temperature. The slow decline is when heat loss is greater than heat production. Once the heat loss and production are equal, the patient is said to be in a steady state [68].
There are four modes of heat loss that occur under general anesthesia in the operating room as seen in Fig. (5). Radiation is the transfer of heat to the surrounding air via photons. This is the primary mode of heat loss during the redistribution of heat from the core to the periphery.
Fig. (5)) Different modes and percentages of heat loss in babies.Convection is the transfer of heat due to air movement which occurs due to the cool laminar air flow in the operating room. Evaporation is when heat loss occurs when water turns into a gas. In the operating room, this occurs due to exposed skin, respiratory exchange and surgical wound exposure. Conduction is the transfer of heat between two objects directly in contact with each other - such as the patient on the operating room table [63, 69].
Heat loss is greater in pediatric patients compared to adults due to their increased body surface areas relative to their total body volume, nominal amount of subcutaneous fat, and thin skin [63, 70, 71]. In addition, the younger the patient is, the more inefficient heat generation is. For the first 3 months of life, neonatal patients do not have the ability to shiver and rely instead on non-shivering thermogenesis (via brown fat metabolism, which does not develop until 26-30 weeks of gestation) for their primary source of heat generation. Non-shivering thermogenesis is inhibited by volatile anesthetics and thus leads to decreased ability of the neonate to thermoregulate.
Regulation of core body temperature is important to maintain optimal organ and enzymatic function. Hypothermia occurs when the temperature goes below 36 degrees Celsius. Hypothermia during surgery is well known to cause increased rates of surgical site infection, poor wound healing, platelet dysfunction, coagulopathy, increased rate of blood transfusion, increased myocardial events, decreased rate of drug metabolism, delayed awakening, and increased length of hospital stay [63, 70]. Conversely, hyperthermia (body temperature > 38 degrees Celsius) can cause tachycardia, vasodilation, and neurological injury. However, the biggest concern when encountering hyperthermia in a pediatric patient in the operating room is malignant hyperthermia, which can be deadly if not detected and treated in a timely manner.
Temperature monitoring should be performed for all anesthetics in order to prevent and treat derangements in body temperature. There are multiple different areas one can measure temperature. A provider can measure the core or peripheral, the core temperature being the most accurate. The core temperature can be measured via nasopharyngeal, distal esophageal, pulmonary arterial catheter or tympanic membrane. Near core temperatures can be measured via rectum or bladder. Skin temperature probes are the most common temperature probe used however, measure peripheral temperature which may be a 2-4 degree Celsius difference from core temperature. Each of these modalities have their limitations [63]. The easiest way to measure core temperature in a pediatric patient typically is nasopharyngeal or distal esophageal - taking care to avoid causing trauma with placement.
There are multiple methods an anesthesia provider can use to warm a pediatric patient. The first way to prevent initial heat loss is by warming the operating room to 75-80 degrees Fahrenheit prior to the patient’s arrival to decrease radiation and convective losses. If a neonatal patient needs to be transported to and from the operating room, one can ensure that the patient has a hat on, wrapped in warm blankets, and transported in a warming incubator or on a warming mattress. Once in the operating room, one can warm the patient prior to inducing anesthesia by forced air blankets and radiant heat lamps [70, 72]. This will increase the heat content of the body overall [73]. Unless a pediatric patient is receiving large volumes of fluids or blood products a fluid warmer adds little value for treating hypothermia [63]. Also, keep in mind pediatric patients may need a higher temperature compared to adults within the operating room to maintain normothermia [74]. Humidifying the breathing circuit minimizes heat loss via evaporation. This can be done actively by evaporative or ultrasonic humidifiers or passively by heat and moisture exchanger (HME). HMEs have commonly been referred to as “artificial noses” [75, 76]. HMEs can humidify the circuit up to 50% which preserves normal cilia function, prevents bronchospasm, and maintains normothermia in the pediatric population. This is due to higher minute ventilation observed in children which is why this is a more effective means of heat conversation compared to adults [77-80]. The patient can be kept warm during the operation by use of forced air blankets while continued temperature monitoring will ensure that the patient does not overheat.
CONCLUSION
Children are not just miniature adults, but differ significantly in the anatomy and physiology of the cardiovascular, respiratory, neurologic, renal, and hepatic organ systems. Also, infants and neonates respond quite differently to various medications due to differences in pharmacokinetics and pharmacodynamics. The understanding of these differences in the developmental phase is essential to providing safe anesthetic care and a complication-free perioperative course.
CONSENT FOR PUBLICATION
Not applicable.
CONFLICT OF INTEREST
The author declares no conflict of interest, financial or otherwise.
ACKNOWLEDGEMENT
The authors thank Eureka Science for the medical illustrations seen throughout the chapter.
