Analgesia

Providing analgesia for procedures both in and out of the operating room is a major responsibility and functions within a spectrum of care (Table 70-4). Techniques exist to provide profound pain relief during operative procedures for all patients, including the most critically ill infants. Blunting the physiologic responses to painful stimuli inhibits the stress response and its multiple deleterious physiologic and metabolic consequences. The response to painful and stressful stimuli is a potent stimulus of the systemic inflammatory response syndrome (SIRS), which leads to increased catabolism, physiologic instability, and increased mortality (Chapter 64). Appropriate use of medication, such as fentanyl anesthesia in neonates, reduces the incidence of postoperative bradycardia, hypotension, acidosis, interventricular hemorrhage, coagulation abnormalities, hypoglycemia, and death.

Hypnosis and Amnesia

The blunting of both consciousness (hypnosis) and conscious recall (amnesia) is a crucial feature of pediatric anesthesia care. Awareness of painful, anxiety-provoking, and stressful conditions for children is just as deleterious, physically and psychologically, as the painful procedures themselves. Management is aimed at blunting the fear and emotional response during surgery, painful procedures (bone marrow aspiration, lumbar punctures), or nonpainful but anxiety-provoking procedures (MRI, CT). Many drugs provide anxiolysis, blunting of recall, and amnesia for such events (Table 70-5). Obtundation of consciousness may accompany the provision of analgesia. Hypnotic and sedative agents can induce altered consciousness without producing any analgesia; analgesia and obtunded consciousness are not synonymous. It is also possible to provide analgesia (local, spinal, or epidural analgesia) without obtunding consciousness.

Table 70-5 SELECTED DRUGS USED IN ANESTHESIA

ICU, intensive care unit.

Sedation describes a medically induced state that is on a continuum between the fully alert, awakened state and general anesthesia (see Table 70-4). In addition to inducing unconsciousness and amnesia, general anesthesia obtunds or ablates critical physiologic reflexes; the most important are airway-protective reflexes: coughing, gagging, and swallowing. Cardiorespiratory reflexes are also obtunded with general anesthesia; respiratory depression and hemodynamic compromise may occur and may be profound. As sedation deepens toward general anesthesia, loss of airway patency, loss of airway-protective reflexes, and loss of cardiovascular stability occur. Light (minimal) sedation is anxiolysis without loss of these reflexes or airway patency. Deep sedation occurs when these reflexes are obtunded or lost (see Table 70-4). Adequate sedation in children may be accompanied by the actual or potential loss of vital reflexes. It is mandatory that those providing sedation for a child be able to detect the transition into deep sedation and general anesthesia and be prepared to manage the child’s airway and circulation, and provide cardiopulmonary resuscitation (CPR) if required.

Akinesia (Immobility or Muscular Relaxation)

Akinesia is the absence of movement. It is necessary to ensure safe and adequate operative conditions and to provide ideal conditions for advanced and meticulous surgery. Akinesia is produced with muscle relaxants (see Table 70-5). These agents facilitate respiratory management in the perioperative period and in critically ill patients. The absence of movement is neither the absence of pain nor the presence of amnesia. Whenever neuromuscular blocking agents are used, analgesia and sedation must be provided.

Physiologic Support

The need for anesthesia increases the need to monitor and support physiologic integrity and homeostasis. Sedation and anesthesia have significant and potentially life-threatening physiologic consequences (see Tables 70-4 and 70-5). Maintenance of adequate cardiorespiratory function, fluid management, electrolyte control, thermoregulation, and concern for all aspects of the child’s health are critical during anesthesia.

Vigilance

Constant, critical attention by physicians who understand the demands of the surgical procedure as well as the changes in physiologic status and their implications is mandatory to provide safe perioperative care for all children. Careful attention to a child’s preoperative condition is mandatory for minimizing the risk during perioperative care (see Tables 70-3 and 70-4).

Inhalational Anesthetics

General anesthesia may be induced and maintained by either inhalation or the IV route. The inhalational anesthetics used in children include sevoflurane, isoflurane, and desflurane. Although halothane is the prototypical pediatric inhalational anesthetic agent, it is no longer used in the USA.

The minimal alveolar concentration (MAC) of an inhalational anesthetic is the alveolar concentration (expressed as percent at 1 atmosphere) that provides sufficient depth of anesthesia for surgery in 50% of patients. For potent inhalational agents, the alveolar concentration of an anesthetic reflects the arterial concentration of anesthetic in the blood perfusing the brain. Thus, the MAC is an indication of anesthetic potency and is analogous to the ED₅₀ (effective dose in 50% of recipients) of a drug. MAC is age-dependent, is lower in premature infants than in full-term infants, and decreases from term through infancy to preadolescence. In adolescence, MAC again increases, falling thereafter. Inhalational anesthetic agents are poorly soluble in blood but rapidly equilibrate between alveolar gas and blood. The less soluble an anesthetic agent is in blood (low blood gas partition coefficient, or ratio of the anesthetic concentration in the blood to the alveolar gas at equilibrium), the more rapid are both the induction of and the emergence from inhalational anesthesia with that agent. Blood gas partition coefficients for sevoflurane (0.69) and desflurane (0.42) are lower than that for halothane (2.4).

Respiratory Effects

The advantages of inhalational anesthesia are rapid onset, rapid offset, convenient route of delivery and excretion (respiratory), and the ability to provide profound analgesia and amnesia. Inhalational anesthetics are all airway irritants and, in low doses, can cause laryngospasm. All inhalational anesthetics depress ventilation in a dose-dependent manner. Thus expired CO₂ and PaCO₂ increase. In addition, anesthesia also decreases end-expiratory lung volume. Small lung volumes result in a decrease in lung compliance, increases in total pulmonary resistance, work of breathing, and intrapulmonary arteriovenous shunting, and a restrictive lung defect. Inhalational anesthetics also shift the CO₂ response curve to the right, thus decreasing, but not ablating, the increase in minute ventilation with increasing PaCO₂.

Inhalational anesthetics, which may induce apnea and hypoxia in premature infants and newborns, are less frequently used in premature infants and children. In neonates and young infants, general anesthesia always necessitates endotracheal intubation and controlled mechanical ventilation. In older children, spontaneous breathing through a mask or a laryngeal mask airway without controlled ventilation is possible for shorter operations. The decreased end-expiratory lung volume and increased work of breathing always necessitate higher inspired oxygen tension.

Cardiovascular Effects

Cardiovascular effects of inhalational anesthesia include depressed cardiac output and peripheral vasodilation; hypotension is frequent. This is accentuated in hypovolemic patients. This hypotensive effect is more pronounced in neonates than in older children and adults. Inhalational anesthetics also decrease baroreceptor and heart rate responses. Inhalational anesthesia blunts the hypoxic pulmonary vasomotor response in the pulmonary circulation, an effect that may contribute to hypoxemia.

The net effect of inhalational anesthesia is decreased oxygen delivery. Perioperatively, catabolism is enhanced and oxygen demand is increased; there may be a profound imbalance between oxygen demand and oxygen delivery. Development of a metabolic acidosis may reflect this imbalance. Because the cardiovascular depressant effects of inhalational anesthesia are greater in premature and newborn infants, these agents are of limited use in such patients.

All inhalational anesthetic agents cause cerebrovasodilation. Sevoflurane is a more potent cerebrovasodilator than isoflurane. Thus, in children with elevated intracranial pressure, impaired cerebral perfusion, or head trauma, and in premature neonates at risk for intraventricular hemorrhage, inhalational anesthetics should be used with extreme caution. Although inhalational anesthetics decrease cerebral oxygen consumption, they may disproportionately decrease blood flow, thus worsening oxygen delivery.

Specific Anesthetics

Intravenous Anesthetic Agents

Anesthesia can be both induced and maintained with either intermittent boluses or continuous infusions of IV anesthetic agents. Intravenous anesthetics include barbiturates, opioids, benzodiazepines, and miscellaneous drugs, such as propofol and ketamine. Intravenous anesthetic agents can induce anesthesia more rapidly than inhalational anesthetics, with fewer complications. Vascular access is required, so unless IV access has already been obtained, inhalation induction is the preferred route. For children arriving in the operating room with vascular access, IV induction should be routine, because it rapidly takes the child from the awake state to the anesthetized state with less psychologic and cardiorespiratory compromise than occurs with inhalational induction. All IV agents affect cardiorespiratory function. The one exception to this may be ketamine, which, in lower doses, releases catecholamines, which maintain cardiac function and blood pressure.

Complications during Induction of Anesthesia

The period between full wakefulness, with the child in control of airway reflexes, and general anesthesia, with total loss of control, is fraught with difficulty. During induction, laryngospasm, bronchospasm, vomiting, pulmonary aspiration of gastric contents, and subsequent aspiration pneumonitis pose a constant threat although they rarely occur. Concern about vomiting and aspiration dictates the use of preanesthetic fasting (NPO) guidelines and indicates rapid sequence anesthetic induction.

Laryngospasm is the most common complication. During induction of anesthesia, especially with inhalational anesthetics, a period of excitement may occur. This period is associated with heightened airway reflexes, which can lead to coughing, gagging, laryngospasm, and bronchospasm. Laryngospasm is reflex closure of the larynx, which makes it impossible for the child to breathe or for ventilation to be used. The child may make violent inspiratory efforts against a closed glottis, generating significantly negative intrathoracic pressure. This may affect cardiovascular function and cause postobstructive pulmonary edema. Laryngospasm can be prolonged, and hypoxia may ensue. Laryngospasm occurs in up to 2% of all anesthetic inductions in children younger than 9 yr and is half as common in older patients. Laryngospasm occurs twice as frequently in children with active or recent upper respiratory tract infection (URI). A history of passive smoking from environmental (parental) tobacco smoke increases the likelihood of laryngospasm 10-fold, and even more if the smoker is the child’s mother.

Laryngospasm can be relieved during induction of anesthesia by increasing the anesthetic dosage, either intravenously or through inhalation (although with the glottis closed, further administration of inhalational anesthesia is not possible). Muscle relaxation relieves laryngospasm, and in an acute situation, this situation may be an indication for succinylcholine. Constant positive airway pressure administered by someone skilled in airway management to ensure patency of the soft tissues of the oropharynx may be beneficial in alleviating laryngospasm. Laryngospasm may also occur during emergence from anesthesia, because a state of excitement is again traversed between deep anesthesia and wakefulness.

Bronchospasm can occur during induction, either in response to histamine release as a result of many of the anesthetic agents or as part of a hyperexcitable stage. Endotracheal intubation may also induce bronchospasm during induction. Bronchospasm during induction is particularly common in children with asthma. Bronchospasm secondary to intubation in a patient with reactive airway disease can be severe, may be associated with life-threatening hypoxemia, and may make it impossible to ventilate the child. The use of histamine-releasing anesthetic agents has been associated with total airway obstruction, respiratory failure, and cardiac arrest. Environmental tobacco smoke is a risk factor.

Other pulmonary problems with induction of anesthesia include massive atelectasis with hypoxemia, impaired ventilation and perfusion, blunted hypoxic pulmonary vasoconstriction, and increased airway secretions with decreased bronchociliary function. Hypersecretion is prevented by the routine use of antisialagogues, such as atropine. The newer inhalation agents are less potent secretagogues, and the use of atropine premedication is much less common, but is probably indicated if ketamine is used.

Hemodynamic complications upon anesthesia induction include hypotension, which can be profound in hypovolemic patients; decreased myocardial function, which can be severe in patients with compromised cardiac function; and tachycardia and cardiac dysrhythmias. Inhalational anesthetics sensitize the myocardium to circulating catecholamines, and induction and excitement are associated with a hypercatecholaminergic state.

Parental Presence during Induction of Anesthesia

Parents may expect to be with their child during the induction of anesthesia. Removing a terrified child from the comforting arms of a parent is stressful for the child, the parent, and the caregivers. If this parental separation cannot be achieved comfortably with preoperative psychoprophylaxis and behavioral modification, including education and desensitization to the operative environment, or with pharmacologic aids, such as preoperative medications including benzodiazepine and barbiturates, then there may be a need to defer parent-child separation until general anesthesia has been induced. Preoperative medication with oral benzodiazepine more frequently provides calm, smooth induction conditions than PPI without pharmacologic preparation. Although the use of PPI in the hands of a confident, competent anesthesia practitioner can replace the need for preoperative medication, it does not reliably predict smooth induction. PPI appears to decrease neither emergence phenomena nor the incidence of postoperative behavioral changes, and it does not appear to add an advantage for the child over that provided by preoperative sedative medication, such as with oral midazolam.

Fluid Maintenance during Surgery and Anesthesia

Patients who are unconscious and immobile have lost venous pump mechanisms and have peripheral venous pooling. Anesthetic agents cause vasodilation, and anesthetized patients have relative hypovolemia. Intravascular volume expansion is frequently required after the induction of anesthesia to maintain adequate perfusion, tissue oxygenation, urine output, and blood pressure. Volume expansion is most commonly provided by isotonic salt-containing solutions (normal saline, lactated Ringer). Autonomic responses may be increased as part of the surgical stress response, with vasoconstriction and intravascular volume contraction due to diuresis, intravascular volume loss from hemorrhage, evaporation (insensible loss, increased during surgery) and third space (interstitial space) fluid losses due to the inflammatory response. Abnormalities in the distribution of renal blood flow and secretion of antidiuretic hormone further complicate the regulation of intravascular volume.

The concern about hypoglycemia due to preoperative fasting led to the recommendation that infants and small children receive isotonic solutions with 5% glucose. The occurrence of hyperglycemia and potential neurologic injury during cardiopulmonary bypass, or during neurosurgery and other situations in which central nervous system (CNS) injury can occur, however, along with the recognition that hypoglycemia is rare in non-neonates, has called into question the routine use of glucose-containing solutions. In neonates, glucose monitoring during and after anesthesia is indicated. In older children with normal nutritional status, isotonic salt solutions without additional glucose are adequate. In children who are receiving parenteral alimentation with a solution containing a high glucose concentration (>10%), continuation of the glucose concentration should be ensured to avoid rebound hypoglycemia, which would occur if the high-glucose solution was stopped.

Intraoperative fluid maintenance includes: (1) current maintenance fluids and replacement of usual deficits during the NPO period; (2) replacement of third space losses; and (3) replacement of extraordinary losses (hemorrhage). Infants should receive glucose-containing isotonic fluids, such as 5% dextrose in water (D5W) with 0.25 normal saline or isotonic crystalloid solutions. A guideline for determining fluid deficits and maintenance requirements in the operating room is shown in Table 70-6. Fluid deficits should be replaced over the first 2 or 3 hr of intraoperative management. Deficits are generally calculated as the number of hours of NPO status multiplied by the hourly maintenance rate for the child. Half of this deficit is replaced during the 1st hr and half during each of the subsequent 2 hr. If hypotension or tachycardia occurs or persists in the early stages of anesthesia, more rapid replacement of the fluid deficit is indicated. The deficit is replaced with isotonic crystalloid solutions.

Table 70-6 INTRAOPERATIVE PEDIATRIC FLUID REPLACEMENT

Third space losses are replaced with isotonic salt solutions. For large operations, such as abdominal or thoracic procedures, during which there may be a large amount of evaporative loss as well as a significant amount of third space loss, 8-10 mL/kg per hr of surgery is generally given as IV fluid replacement. For smaller operations, such as herniorrhaphy, pyloromyotomy, and minor procedures, fluid replacement at 3-5 mL/kg/hr is indicated for third space losses. Even when surgery involves the extremities and third space losses are minor, it is wise to give an additional 1-2 mL/kg/hr to replace them.

A crystalloid solution is indicated for blood loss, at 3 mL per mL of blood lost. This formula could be reduced somewhat if blood is replaced on an mL-per-mL basis with packed red blood cells or whole blood equivalent. The use of albumin or other suitable colloid, such as fresh frozen plasma in neonatal surgery, also decreases the amount of crystalloid replacement needed for blood loss. During maintenance anesthesia, if large-volume transfusions are required, warming the blood and crystalloid solutions avoids hypothermia. With major surgery and the resultant SIRS, capillary integrity is lost and third space losses are common. Failure to replace this third space loss and restore intravascular volume leads to hypotension, shock, acidemia, and renal failure, and further stimulates the SIRS.

Complications in the PACU

Airway Evaluation

Because the induction of anesthesia is associated with loss of spontaneous ventilation and airway reflexes, predicting the inability to bag-and-mask ventilate or endotracheally intubate a child before anesthesia is critical. The anesthesiologist must be made aware of children who have congenital anomalies that affect the airway (Table 70-9). Such anomalies include micrognathia syndromes, macroglossia syndromes, and some thoracic anomalies. Congenital anomalies associated with airway compromise should be diagnosed preoperatively. Conditions that impair mouth opening (temporomandibular joint disease) should be noted. A history of wheezing or stridor may indicate postoperative airway complications and difficult intraoperative airway management.

Mediastinal Masses

Children with anterior mediastinal masses, such as lymphomas and primary mediastinal tumors, are at serious risk for airway compromise, cardiac tamponade, and vascular obstruction. Induction of general anesthesia and even mild sedation can lead rapidly to total loss of the airway, with inability to ventilate the child and cardiovascular collapse. These patients often present in a semi-emergency fashion, with the need for both a tissue diagnosis of the mass before treatment is initiated and a surgically placed central venous line.

Significant compression of vital structures can occur with seemingly mild symptoms. Tachypnea, orthopnea, wheezing, and sleep disturbances or avoidance of prone or supine positions are significant indications of serious risk. Pericardial tamponade or superior vena cava syndromes are more concerning findings. A CT scan showing >50% compression of the airway at the carina is an indication to prohibit general anesthesia and provide only mild sedation. Echocardiographic or CT evidence of pericardial tamponade, right ventricular compression, or compression of the pulmonary artery suggests severe risk. Biopsy with the child under local anesthesia may be indicated. If anesthesia is required, cardiopulmonary bypass should be considered, in case it becomes impossible to ventilate the child during surgery. In high-risk children, consideration should be given to initiating treatment with steroids, radiation therapy, and chemotherapy before obtaining a tissue diagnosis.

Down Syndrome

Children with Down syndrome are occasionally behaviorally difficult and are especially fearful of medical caregivers (Chapter 76). Their cardiac anomalies, macroglossia, and upper airway obstruction can be challenging. Children with Down syndrome have atlantoaxial instability due to odontoid hypoplasia and joint laxity. In younger children, extension of the neck, routinely used to maintain and intubate the airway, may lead to cervical dislocation and spinal cord trauma. Some anesthesiologists recommend extension and flexion lateral neck films to detect instability before anesthesia. In children with Down syndrome, it is wise to exercise caution in stabilizing the cervical spine and also to avoid cervical flexion and extension.

Cardiovascular System

Because of the depressant effects of anesthetics and the increased metabolic demands of surgery, any compromise of myocardial function should be clearly delineated preoperatively. A preoperative ECG, an echocardiogram, and a cardiology consultation are indicated for children with a history of heart disease. An intracardiac shunt will affect oxygenation status intraoperatively. Because of the significant effect on the oxygen supply-and-demand relationship caused by general anesthesia and surgical stress, obstructive lesions, such as a valvular stenosis, must also be clearly defined. A history of cardiac dysrhythmias should be clearly understood, because inhalational anesthetics are dysrhythmogenic.

In neonates, ductus arteriosus, myocardial compromise, pulmonary edema, or congenital heart disease can significantly complicate oxygen delivery during anesthesia. Accurate diagnosis of cardiac murmurs in neonates is essential. Any preoperative cardiovascular compromise will be worsened intraoperatively and can catastrophically complicate the perioperative course.

Anemia should be diagnosed and corrected preoperatively if possible. A hematocrit value >30% is generally acceptable for routine elective anesthesia. If there are reasons to expect significant blood loss or prolonged convalescence, anemia should be corrected preoperatively. In the emergency setting, transfusion may be required. Although lower hematocrit values can be tolerated in unstressed children, the significant threat to oxygen delivery posed by anesthesia and surgery, especially if blood loss is expected, requires maintenance of an adequate hemoglobin concentration perioperatively.

Evidence of coagulopathy should be sought. Easy bruising, the use of aspirin, and familial bleeding disorders should be discussed. Intraoperative hemorrhagic bleeding can be difficult to control; massive perioperative blood transfusions have significant risk of morbidity and mortality. Preoperative correction of coagulopathic disorders is indicated. In neonates, assurance of vitamin K prophylaxis and adequate coagulation status is critical before any significant surgery. In neonates and critically ill children, adequacy of platelet count and, where indicated, coagulation factors, prothrombin time, and partial thromboplastin time should be assured.

Neurobehavioral Considerations

Seizures, significant neurologic impairment, altered level of consciousness, respiratory airway compromise secondary to neurologic disease, and neuromuscular disease should be sought and evaluated. Anticonvulsant drug metabolism is often altered perioperatively, and this change may affect anticonvulsant drug levels. Anticonvulsants may also complicate anesthetic management. Maintenance of appropriate anticonvulsant therapy postoperatively is important to avoid new seizures. Cerebrospinal fluid secretion is increased during surgery and general anesthesia. This fact is significant in patients in whom elevated intracranial pressure is suspected and in children with ventriculoperitoneal shunts. In infants or older children with ventriculoperitoneal shunts, shunt patency and function should be assured before surgery.

Illness and the need for surgery or painful medical procedures are psychologically traumatic events for children and their families. Children are also remarkably adept at sensing stressful signals from their parents and caregivers. Many children who require anesthesia may have significant levels of fear and anxiety. Most children undergoing surgery have new-onset negative behavioral changes in the postoperative period, such as maladaptive behavioral responses that include generalized anxiety, enuresis, enhanced separation anxiety, temper tantrums, nighttime crying, and fear of strangers, doctors, and hospitals. Approximately 20% show these negative behavioral adaptations for 6 mo after surgery. Sleep quality is also altered postoperatively, resulting in further behavioral compromise.

The risk factors for postoperative behavioral changes include preoperative or induction anxiety and behaviors indicating extreme stress, as well as emergence excitation. The type of surgery may be important, with tonsillectomy and genitourinary surgery having a high incidence of postoperative behavioral changes, whereas simple procedures (tympanostomy tubes) seem to be associated with fewer changes. Another risk factor is recurrent procedures, such as anesthesia for laser surgery, strabismus surgery, or repeated eye examinations, which lead to difficult behavioral changes and have a significant effect on family dynamics.

Preoperative psychologic preparation programs decrease the incidence of postoperative behavioral changes, which last for up to 1 mo. PPI does not improve postoperative behavior. Oral midazolam (0.5 mg/kg) may decrease negative behavioral changes after surgery. Midazolam has the benefit of providing not only rapid-onset anxiolysis in 10-20 min but also very effective and rapid (10 min) amnesia.

Preoperative Preparation

The child should be in the best possible nutritional state, and nutritional supplementation, even hyperalimentation in chronically ill children, may be worthwhile.

Regional Anesthesia

Regional anesthesia is the use of anesthetics to block the conduction of afferent neural impulses to the CNS. These can be local analgesic techniques, peripheral nerve blocks, nerve plexus blocks, or epidural and subarachnoid (spinal) nerve blocks. They may be administered either through a single injection (single shot) or through continuous infusion, as is common with epidural and occasionally subarachnoid blocks. They may be used for intraoperative anesthesia and postoperative analgesia, and they have the potential to decrease intraoperative analgesia and anesthetic use as well as to provide postoperative pain management. Increased use of regional indwelling catheters to deliver continuous analgesia has shortened recovery times and hospital stays in children.

Analgesia at the site of need, without central cardiorespiratory depressant effects, can be valuable. Local anesthesia, with injection of lidocaine or bupivacaine into the affected area, can provide procedural analgesia that lasts for several hours. Infiltration of the wound site and the edges of an incision decreases postoperative pain in the initial hours after surgery. This can be performed by the surgeon at the conclusion of surgery and may supplement postoperative analgesia.

Epidural analgesia is common in pediatric practice. The epidural space lies between the dura and the pia and arachnoid membranes, an area through which all nerve roots pass. Bathing these nerve roots in local anesthetics inhibits conduction of pain impulses centrally. A single dose of epidural anesthetic may provide hours of pain relief, and a continuous infusion may provide effective pain relief for hours to days. The epidural injection of opioids can provide analgesia for 12-24 hr and is a potential supplement to postoperative analgesia.

A lumbar epidural injection is placed in the lumbar area to provide analgesia for labor and for surgery below the thorax. Caudal epidural analgesia is placed through the sacral hiatus, inferior to the distal end of the spinal cord. This is the site most commonly used for regional anesthesia and analgesia in children and is efficacious for the provision of pelvic and lower limb anesthesia as well as beneficial in orthopedic and urologic surgery. A continuous infusion of bupivacaine is the most common means of providing postoperative epidural pain relief; it may be mixed with an opioid (fentanyl or preservative-free morphine). It is also possible to provide epidural PCA with a continuous infusion pump and the ability of the patient to self-medicate with bolus prn dosing. Epidural analgesia can also provide pain relief in patients with chronic pain or pain caused by advanced malignant conditions.

The most serious complications of neuraxial anesthesia include cephalad spread of blockade with respiratory depression, paralysis of respiratory muscles, and, in extreme cases, brainstem analgesia and depression. The most common complications of neuraxial analgesia include mild discomfort; a paresthesia-like feeling of numbness and tingling; pruritus, which, if opioids are used, can be quite distressing; and occasional nausea and vomiting. Infection and epidural hematoma are extremely rare. Neuraxial opioids, especially when administered intrathecally, can cause respiratory depression; their use requires postoperative monitoring. The use of neuraxial opioids often requires treatment with antipruritic as well as antiemetic drugs.