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Christian Seefelder, Robert SĂźmpelmann
1Anesthesia and analgesia for thoracic surgery
1.1Introduction
The unpleasant times of years gone by when surgeons and anesthesiologists found themselves in conflict over competing perceptions of their respective importance and relevance are hopefully consigned to the past. Today, interdisciplinary collaboration and close cooperation are critical to ensuring that all patients are provided with the best practice and levels of care. This is particularly true when treating low-weight prematures or performing minimally invasive procedures in the thoracic cavity. In the following chapter, Christian Seefelder focuses not only on appropriate procedures and techniques, but also on perioperative pain management.
1.2Anesthesia for pediatric thoracic surgery
The advances in pediatric surgery have resulted in the desire by the pediatric surgeon, by families and by medical consultants for earlier, more definitive, often video-assisted, âminimally invasiveâ surgery in younger and sicker patients than a decade ago. Anesthesia care for small, young and sick patients may have become safer more through better understanding, improved monitoring and more courage than through improvements in drugs, advances in technology or innovation in management. Pediatric anesthesiologists need intimate knowledge and understanding of the (congenital) surgical lesion and its pathophysiology, of the associated medical disorders and of the surgical procedure. In turn, pediatric surgeons need knowledge and understanding of the anesthetic techniques, concerns and limitations such as neurotoxicity of anesthesia in neonates, infants and young children, the difficulty of lung isolation in small patients or the physiologic challenges of minimally invasive surgery in pediatric patients.
1.2.1Neurotoxicity of anesthesia in neonates, infants and young children
Animal and human data suggest that anesthesia in young animals as well as in human neonates, infants and young children may have unfavorable effects on the developing brain. The initial animal studies provoked disbelief, as a human neonate could not just be equated with a rat pup. Subsequently, clinical studies disturbingly confirmed the concerns rather than dispelling them [1, 2]. Further data are eagerly awaited by the pediatric anesthesia community, while surgeons not uncommonly have remained unaware of the whole discussion.
1.2.1.1Animal data
Solid data from animal models suggest that exposure of neonatal animals to agents used in human anesthesia results in accelerated or premature neuroapoptosis and neurodevelopmental disadvantages. Common criticism of these studies includes the difficulty extrapolating from animal data to humans, difficulty comparing doses required for animals and humans, difficulty comparing animal outcomes to human outcomes, difficulty excluding the effect of disease and surgery requiring anesthesia on neurodevelopment and impossibility of providing necessary surgery without anesthesia. At the same time, suspicion has been brought forward that it is less the anesthetic agent than the physiologic milieu created that may be responsible for the changes (i.e. hypotension, desaturation). A clear recommendation regarding a safe or advantageous general anesthetic technique or agent is missing, but dexmedetomidine may be less detrimental than other anesthetic agents in regards to neurotoxicity.
1.2.1.2Human data
Human data from retrospective and database studies indicate a neurodevelopmental disadvantage in children who have undergone (multiple) anesthetics as neonates, infants or young children compared to matched controls, siblings or twins without anesthesia. First results of a prospective randomized controlled study comparing one hour of sevoflurane anesthesia with awake/regional anesthesia for hernia repair in infants did not show a difference in neurodevelopmental outcomes at the 2-year follow-up [3]. Further information is sought through studies of neurodevelopment after intrauterine exposure to anesthesia, studies of sedation of neonates in the intensive care unit and studies of retinal apoptosis as âwindows into the brainâ.
1.2.2Basic anesthetic techniques in pediatric anesthesia
While thoracic surgery is performed under general anesthesia, there is often a misunderstanding by patients, families, medical specialists and surgeons about the degree of sedation for other studies and procedures. Not uncommonly, it has been agreed upon that a procedure can be done âunder localâ or âlight sedationâ, but at the same time the patient has been promised to be âasleepâ and the surgeon or radiologist expects the patient to be ânot movingâ.
Few children are interested in being awake and aware and in lying still for procedures or studies. Small infants can sometimes be fed and bundled up and sleep through non-stimulating studies such as MRI. Distraction and entertainment with videos can be offered and parents can be present for reassurance for older children to undergo unsedated imaging studies or procedures such as lumbar puncture, bone marrow aspirate or central line placement under topical or local anesthesia.
Although light and moderate sedation with low doses of sedatives or systemic analgesics administered enterally or parenterally may relieve anxiety, by definition patients will respond to commands and stimulation and some children may move and cry, sometimes are disinhibited and may become more restless and less cooperative with the risk of escalating dosing of drugs.
For adequate surgical conditions and for imaging studies requiring immobility, deep sedation or general anesthesia are necessary; while spontaneous respirations may be maintained, concerns are progression to apnea, loss of protective airway reflexes, increasing airway obstruction and hemodynamic compromise.
1.2.3Age at and timing of surgery
Cardiothoracic surgical intervention may occur as early as in utero, for example for aortic stenosis with evolving hypoplastic left heart syndrome, life threatening congenital pulmonary airway malformation or severe congenital diaphragmatic hernia. Some patients may require ex utero intra partum treatment or âEXITâ procedures with surgical intervention or placement on extracorporeal membrane oxygenation (ECMO) during birth and while on placental support. Anesthesia, monitoring and resuscitation of the fetus is provided by fetal anesthesia subspecialists while the mother is anesthetized and monitored by the obstetric anesthesiologist. Emergent or urgent neonatal thoracic surgery is required for large or enlarging congenital pulmonary lesions, for tracheo-esophageal fistula (TEF) and congenital diaphragmatic hernia. Many lung biopsies and tumor resections need to be performed whenever the patient presents. Given the neurodevelopmental risks of anesthesia in young patients, elective pediatric surgery should be postponed, but the age by which anesthesia in children is safe remains elusive. Irrespective of the neurodevelopmental concerns, the risk of anesthesia-related complications is highest in the youngest [4].
Surgical pathology in children is dominated by congenital abnormalities or pediatric-specific acquired disorders. Pediatric anesthesia and surgery provide care to patients from the 0.5 kg 24-week premature neonate to the 100 kg teenager. While âa child is not just a small adultâ, the main difference and the anesthetic implication for older children lie mostly in the psychological issues as well as in issues of equipment-size. For premature and term neonates as well as infants, drugs, equipment or technologies may not be available, formally approved or scientifically validated. The difference in physiology of the neonate and infant from the physiology of older children and adults is characterized by immaturity of the function of all organs and systems (central nervous, cardiovascular, respiratory system, renal, hepatic, endocrine, metabolic, gastrointestinal function, pharmacology, immunology, hematology), all of which need to be considered by the pediatric anesthesiologist during anesthesia in this patient population.
1.2.4Preoperative evaluation and workup
The typical evaluation and workup will include all aspects of the history and physical exam, with focus on the thoracic pathology in question, specifically any respiratory symptoms and distress, stridor and any signs or symptoms indicating difficult airway management or risk of respiratory obstruction during anesthesia and surgery. Most studies will have been ordered by surgeons and pediatric specialists but should be reviewed by the pediatric anesthesiologist, including chest x-ray, computed tomography (CT), magnetic resonance imaging (MRI), angiograms, ventilation/perfusion scans, cardiologic studies, lung function tests, laboratory results, cultures and biopsies. Of particular importance is consultation with other pediatric specialists such as pediatric pulmonologists, cardiologists, hematologists, oncologists, endocrinologists and radiologists to optimize preoperative workup, evaluation, management and communication.
Especially in younger children with limited cooperation, many types of studies such as lung function tests may not be possible at all. Others such as CTs, MRIs, angiographies or biopsies will require the involvement of the anesthesiologist for sedation or anesthesia. To provide the patient with a safe anesthetic and a satisfactory study, requesting service, surgeon, radiologist and anesthesiologist should communicate before the study to understand each otherâs concerns and objectives. While case to case assessment and discussion are important, agreeing on a protocol across departments allows input from all specialties ahead of time and decreases case to case confrontation. Protocols appear reasonable for imaging studies in patients with anterior mediastinal masses or tracheomalacia. Early involvement has the advantage of familiarizing the anesthesiologist with the patientâs airway anatomy and management and physiologic response to anesthesia prior to major thoracic surgery.
1.2.5Intraoperative monitoring
Standard monitoring includes electrocardiogram (ECG), non-invasive blood pressure (NIBP), pulse oximetry, patient temperature, inspiratory oxygen concentration (FiO2) and end-tidal CO2 concentration (ETCO2). It may be difficult to establish all monitors prior to induction in children.
Invasive arterial monitoring allows arterial blood gas sampling and immediate recognition of hemodynamic effects of surgical retraction, mechanical arrhythmias or air embolism. It is indicated in lobectomy or pneumonectomy, in thoracic tumor resections, major neonatal thoracic surgery for congenital diaphragmatic hernia or TEF repair, in infant thoracoscopy or for the patientâs general medical condition. Lung isolation in itself is not an indication for placement of an arterial catheter, and it may not be necessary for simple lung wedge resections or biopsies, thoracoscopic pleurodesis or pectus repair. Risks include ischemic complications from local skin necrosis to loss of an extremity. Placement aids for small patients are transillumination, Doppler and more recently ultrasound.
Central venous pressure monitoring may not be reliable in situations of an open chest, retraction of cardiovascular structures and capnothorax but may have a place for perioperative monitoring. A central venous catheter also serves as secure perioperative venous access and for the administration of vasoactive agents and should be considered whenever their need is anticipated.
Pulse oximeters, arterial catheter and blood pressure cuff are distributed over several extremities. In neonates, pre- (right arm) and post-ductal (lower extremity) oxygen saturation should be monitored to detect right to left shunting across the ductus arteriosus. Electroencephalographic monitors are available for anesthetic depth, seizure and ischemia monitoring. Transesophageal echocardiography is available for children, non-invasive cardiac outp...
