Chapter Outline
Preoperative Evaluation of Children 101
Sedation of the Pediatric Patient by Nonanesthesiologists 103
Acute Pain Management 103
Regional Analgesia 106
Strategies to Reduce Blood Transfusions in Scoliosis Surgery 108
Latex Allergy 110
Malignant Hyperthermia 111
Anesthetic Considerations for Pediatric Orthopaedic Diseases and Syndromes 112
Preoperative Evaluation of Children
More than 50% of all surgeries performed in children are in the ambulatory or same-day surgery setting. The success of outpatient surgery depends, in part, on the adequate preparation of children and parents. Much of the preoperative and immediate postoperative care of these children that was provided in the hospital by the anesthesiologist is now being done by the child’s surgeon or pediatrician in an outpatient setting.
Infants and children who require anesthesia for orthopaedic procedures represent all stages of development, from birth to adolescence. At one end of the spectrum is a healthy child; at the other is a child with multiple congenital anomalies who could present special problems to the anesthesiologist. The orthopaedic surgeon, by being aware of such potential problems, can alert the anesthesiologist.
In this section, the emphasis is placed on the aspects of the child’s history and physical examination and relevant laboratory tests that contribute to decreasing anesthetic risk. The areas of primary concern in the child’s history are related to respiratory, cardiovascular, neuromuscular, endocrine, and hematologic and oncologic disease. In the physical examination, the anesthesiologist is mainly interested in airway anatomy (warning of the possibility of a difficult intubation), the presence of stridor, wheezing (preoperative and postoperative hypoxemia), murmurs, and any preexisting neurologic deficit; anesthesia agents and medications can exacerbate any preexisting neuromuscular weakness.
Children on seizure medication should take their morning dose with a sip of water. Because almost all anesthetics produce cerebral vasodilation and therefore may increase intracranial pressure, children at risk of developing intracranial hypertension (e.g., hydrocephalus, blocked ventriculoperitoneal shunts, brain tumors) must be identified before surgery. Any evidence of brain stem dysfunction (e.g., vocal cord paralysis, swallowing dysfunction and/or aspiration) should be noted in the preoperative evaluation. In children with progressive diseases of nerve or muscle, hyperkalemia or malignant hyperthermia occur more commonly following the administration of succinylcholine; therefore, the anesthesiologist should be warned of the nature and extent of the underlying condition. The presence of an abnormal murmur, cyanosis, decreased exercise tolerance, poor weight gain, sweating, decreased femoral pulses, or a precordial heave necessitates a more thorough evaluation (hematocrit, electrocardiography, chest radiograph, O 2 saturation, and cardiology consult).
Antibiotic prophylaxis to prevent bacterial endocarditis for children with congenital heart disease undergoing surgery is essential. I follow the American Heart Association antibiotic regimen guidelines. The first dose is usually given via the intravenous (IV) route after initiation of anesthesia and before nasotracheal intubation or surgical incision. The parents must be advised that the antibiotic prophylaxis must be continued postoperatively at home in cases of outpatient surgery.
Infants born prematurely have a significant risk of postoperative apnea that decreases as postconceptual age increases. Children with a history of bronchopulmonary dysplasia and those with obstructive sleep apnea are at greater risk for perioperative hypoxemia and acute right heart failure. Patients with diabetes need to be evaluated jointly by the anesthesiologist and pediatrician of record to determine a plan of management.
Patients on long-term corticosteroid therapy have suppression of the hypothalamic-pituitary-adrenal axis and therefore cannot manifest an appropriate stress response (addisonian crisis). These children should receive 0.5 mg/kg prednisone orally the night before and 1 mg/kg hydrocortisone IV after induction of anesthesia.
In otherwise healthy children scheduled for elective surgery, routine laboratory tests, chest radiography, or urinanalysis are rarely indicated. However, African-American children who have not had a hemoglobin or hematocrit determination after 4 months of age should have a sickle cell screening test; if positive, a hemoglobin electrophoresis should be done to define the exact nature of the hemoglobinopathy.
Although the healthy child needs almost no preoperative laboratory tests, the situation is entirely different in children who have a history of an abnormality. For example, knowing the hemoglobin level is important in the child with cardiac or sickle cell disease. A chest radiograph is helpful in a child with a history of chronic aspiration or lower airway disease. Children on digoxin therapy should have their serum sodium, potassium, and digoxin levels measured. An electrocardiogram (ECG) is warranted in a child with congenital heart disease, obstructive sleep apnea, or bronchopulmonary dysplasia (BPD). The child with Down syndrome or diastrophic dysplasia needs an anterior-posterior and lateral radiograph of the neck to detect the presence of instability of the cervical spine.
Upper Respiratory Infections
Upper respiratory infections (URIs) are the most common illnesses affecting children younger than 5 years. The reported incidence of URI is 24% in this age group. Children younger than 1 year have an average of 6.1 respiratory illnesses/yr. Children between 1 and 5 years of age have an average of 4.7 to 5.7 respiratory illnesses/yr. In children with an URI there is an increased incidence of the following problems during and after surgery:
- •
Laryngospasm during induction of and emergence from anesthesia.
- •
Bronchospasm. A viral URI will initiate wheezing more commonly in children than adults, whether or not they have a history of asthma. Children younger than 5 years with preexisting asthma or with respiratory syncytial virus are prone to develop bronchospasm.
- •
Coughing caused by increased airway secretion and hyperreactivity. Coughing can infrequently cause silent regurgitation and aspiration.
- •
Reduction in O 2 saturation intraoperatively and postoperatively caused by these factors and also by lung atelectasis and the reduction of functional residual capacity (FRC).
Diagnosis
In general, two of the following criteria must exist:
- •
Sore or scratchy throat
- •
Sneezing
- •
Rhinitis
- •
Fever (mild)
- •
Congestion
- •
Malaise
- •
Nonproductive cough
- •
Laryngitis
Sneezing and runny nose do not necessarily indicate an URI and when in doubt, it is helpful to ask the parents if they think that the child has an URI. These symptoms are often caused by allergic rhinitis, and one should ask if there is a family history of allergies.
Routine surgery in the presence of URI should definitely be canceled if any of the following criteria are a factor:
- •
The patient is younger than 1 year.
- •
The patient has a lower respiratory infection.
- •
The patient has signs of overt viral or bacterial infection.
Elective surgery on patients with a suspected respiratory tract infection should be postponed for 1 to 2 weeks after cessation of symptoms for URI and for at least 4 to 6 weeks after cessation of symptoms for lower respiratory infection (e.g., bronchiolitis or pneumonia).
Asthma
Every anesthesiologist is interested in the preoperative optimization of medical therapy for asthma because children with reactive airway disease (RAD) have a high likelihood of intraoperative bronchospasm, hypoxia, hypercarbia, acidosis, and prolonged hospitalization. In general, therapy should be escalated preoperatively for asthmatic children, even if they are well controlled, because many procedures routinely performed during anesthesia (e.g., laryngoscopy, intubation) are potential triggers for bronchospasm. For example, the child on an as-needed (PRN) inhaled β-agonist, steroid or oral medication should be changed to regular administration for 3 to 5 days preoperatively. The child on chronic medication should have a steroid added. The child on a chronic bronchodilator and steroid requires an increase in frequency of nebulizers or increased steroids or, if necessary, all of the above.
A recent asthma exacerbation requiring emergency admission or hospitalization within 6 weeks of surgery precludes elective surgery. The peak expiratory flow and FEV 1 (forced expired volume in 1 second) are reduced for up to 6 weeks following an asthma attack. Elective surgery in asthmatic children who have an URI should be postponed for 6 weeks, even if they do not have any evidence of wheezing on auscultation, because the incidence of bronchospasm increases by elevenfold in asthmatic compared with nonasthmatic children.
Corticosteroids are extremely effective in preventing perioperative wheezing. For children who have required steroid administration in the past year, those who are on bronchodilators all the time, and those who are almost never wheeze-free, a short course of prednisone, 1 mg/kg orally, once daily for 3 days prior to surgery and on the morning of surgery is highly recommended.
NPO Requirements in Infants and Children
In the hope of reducing the risk of perioperative aspiration pneumonitis, a period of fasting (NPO) has become a routine feature of the preoperative preparation of the surgical patient ( Table 8-1 ).
| Age (mo) | Fasting Time (hr) | |
|---|---|---|
| Solids * | Clear Liquids | |
| <6 | 6 | 2 |
| 6-36 | Formula: 6 | 2 |
| Solids: 8 | ||
| >36 | 8 | 2 |
Fluid Management
Postoperative Fluid Management
During the immediate postoperative period, IV fluids are administered to replace the following:
- 1.
Maintenance fluid loss
plus
- 2.
Ongoing third space loss, dependent on the extent of the surgical procedure (range, 1-10 mL/kg/hr)
plus
- 3.
Minor blood loss
Hourly Maintenance Fluid Requirement
Managing fluid balance is usually easier if fluid requirements are calculated on an hourly basis:
- •
4 mL/kg/hr for the first 10 kg of body weight
- •
2 mL/kg/hr for the next 10 kg of body weight
- •
1 mL/kg/hr for any weight more than 20 kg (i.e., a 27-kg child will receive 67 mL/hr)
Sedation of the Pediatric Patient by Nonanesthesiologists
The safe sedation of children requires a network of trained personnel with common sense in selecting patients suitable for sedation and in appropriate selection and dosage of drugs, and with the ability to monitor vital signs and manage the airway using appropriate equipment. Catastrophic outcomes such as seizures and respiratory and cardiac arrest have occurred in various practice settings when any one of these factors was deficient.
Sedation and Analgesia (Conscious Sedation)
Conscious sedation is a state that allows a patient to tolerate unpleasant procedures while maintaining the following: (1) protective reflexes; (2) a patent airway independently and continuously; and (3) the ability to respond to physical stimulation or verbal commands (e.g., “open your eyes”).
Deep Sedation
Deep sedation is a medically controlled state of depressed consciousness or unconsciousness from which the patient is not easily aroused. It may be accompanied by a partial or complete loss of protective reflexes and includes the inability to maintain a patent airway independently and respond purposefully to physical stimulation or verbal command.
In my opinion, the term conscious sedation should be abolished because it is often difficult to achieve conscious sedation without the potential for the patient to become deeply sedated. This term has given many physicians the false hope that they can achieve a state of satisfactory sedation for all types of painful and stressful procedures without adverse sequelae. Any physician who orders narcotics and sedatives for the purpose of consciously sedating a patient must be able to manage an obstructed airway or depressed level of respiration.
Patient Selection and Evaluation
The relative health of the child may be readily assessed by using the same simple scale used by anesthesiologists when evaluating preoperative patients ( Table 8-2 ). The nonanesthesiologist should restrict the choice of patient for conscious sedation to classes I and II and request assistance from the anesthesiology department for the very sick patient ( Table 8-3 ).
| Class | Description of Patient |
|---|---|
| I | Normally healthy patient |
| II | Patient with mild systemic disease |
| III | Patient with severe systemic disease |
| IV | Patient with severe systemic disease that is a constant threat to life |
| V | Moribund patient who is not expected to survive without the operation |
| Drug | Route of Administration | Dose (mg/kg) |
|---|---|---|
| Barbiturates | ||
| Pentobarbital | Rectal | 5-10 |
| Benzodiazepines | ||
| Diazepam | Oral | 0.1-0.3 |
| IV | 0.1-0.3 | |
| Rectal | 0.2-0.3 | |
| Midazolam | Oral | 0.5-0.75 |
| Rectal | 0.5-0.75 | |
| Nasal | 0.2-0.5 | |
| Sublingual | 0.2-0.5 | |
| IV | 0.05-0.15 | |
| IM | 0.05-0.15 | |
| Choral hydrate | Oral | 50-100 |
| Ketamine | Oral | 6-10 |
| Rectal | 5-10 | |
| IV | 1-3 | |
| IM | 3-10 | |
| Opioids | ||
| Morphine | IV | 0.1-0.3 |
| IM | 0.1-0.3 | |
| Meperidine | IV | 1-3 |
| IM | 1-3 | |
| Fentanyl | Oral transmucosal | 0.015-0.030 |
| (15-30 µg/kg) | ||
| IV | 0.001-0.005 | |
| (1-5 µg/kg) In increments of 0.5-1.0 µg/kg | ||
A child undergoing a procedure that is not painful (e.g., computed tomography [CT] scan) does not need a narcotic. Conversely, a child undergoing a painful procedure needs a narcotic or combination of narcotic and sedative, but never sedative alone. It is of utmost importance for the child to be observed in an appropriate recovery facility for an appropriate period of time prior to discharge.
Acute Pain Management
Acute pain refers to pain of short duration (usually, 3-7 days) and is usually associated with surgery, trauma, or an acute illness. Historically, the management of pain in children has been neglected. The common misconception that neonates are unable to perceive pain and that all children are at excessive risk of respiratory depression after administration of opioids led to underdosing of children after surgery. There is now a body of evidence showing that pain activates neuroendocrine responses, which increase tissue catabolism and impair tissue healing. Furthermore, inadequate analgesia may further impair postoperative pulmonary function and increase the risk of morbidity or mortality after surgery.
Assessment of Pain in Children
To treat pain effectively, one must be able to assess and measure pain accurately. Because pain is a subjective experience, a self-assessment scale is always preferable to an observer’s objective assessment and should be used whenever possible. Unfortunately, preverbal or mentally impaired children must be assessed by an objective observer and no fully satisfactory system has yet been devised.
Self-Assessment
Simple self-assessment methods can be used in children 4 years of age and older who can verbalize and is the most reliable and effective method of pain assessment. Younger children prefer to use the FACES Scale ( Fig. 8-1 ); children 7 years of age and older can often use a visual analog scale (VAS) or numeric rating scale ( Fig. 8-2 ).
Physiologic Measurement and Behavioral Observation
These methods of pain assessment are used in children with limited or no verbal skills. All objective rating systems rely on changes in heart rate, respiratory rate, and blood pressure, together with behavioral assessment. There is always some difficulty in separating behavior associated with pain from that caused by anxiety, fear, or hunger. One such scale is the FLACC ( f ace, l eg, a ctivity, c ry, c onsolability) scale ( Table 8-4 ).
| Behavior Category | Score | ||
|---|---|---|---|
| 0 | 1 | 2 | |
| F ace | No particular expression or smiling | Occasional grimace or frown, withdrawn, disinterested | Frequent to constant clenched jaw, quivering chin |
| L egs | Normal position or relaxed | Uneasy, restless, tense | Kicking, or legs drawn up |
| A ctivity | Lying quietly, normal position, moves easily | Squirming, shifting back and forth, tense | Arched, rigid, or jerking |
| C ry | No crying—awake or asleep | Moans or whimpers, occasional complaint | Crying steadily, screams or sobs, frequent complaints |
| C onsolability | Content, relaxed | Reassured by occasional touching, hugging, or “talking to”; distractible | Difficult to console or comfort |
Pain Management
Pain following orthopaedic surgery is often intense. Effective pain management always begins during a preoperative discussion with children and their parents. Psychological preparation of patients can favorably modify the amount of discomfort and anxiety experienced by the child. The child and parents should be informed that every effort will be made to have the child as pain-free as possible and that although some discomfort is inevitable, it will be minimized. Appropriate pain management techniques are discussed here. Play therapy, both as a preoperative teaching tool and a postoperative distraction technique, is also very helpful. A child life specialist is often enlisted for this purpose.
Systemic Analgesia
Nonopioid Analgesics
Acetaminophen is the nonopioid analgesic generally used in pediatrics. It should be used in preference to aspirin because of aspirin’s greater frequency of side effects (e.g., gastritis, platelet dysfunction, and the rare but significant statistical association of aspirin with Reye syndrome). Acetaminophen is safe, even in newborns. Acetaminophen may be administered orally, 10 to 15 mg/kg, every 4 hours or rectally, 10 to 20 mg/kg, every 4 hours.
Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit the cyclooxygenase enzyme, resulting in decreased production of prostaglandin. It is believed that because prostaglandins are a major component of the inflammatory response, and because the inflammatory response contributes to pain, the use of NSAIDs reduces pain. These drugs in combination with opioids will provide more effective analgesia in the short-term management of moderate to severe postoperative pain than either of the drugs used alone.
IV ketorolac may be administered at 0.5 mg/kg (maximum, 30 mg/kg) every 6 hours for a maximum of 3 to 5 days because the risk of renal impairment is increased if used longer than 3 to 5 days. If the child is able to tolerate oral medication, ibuprofen (8-10 mg/kg) four times daily is recommended.
The side effects of NSAIDs include renal impairment (especially in patients in a state of shock, such as hypovolemic or cardiogenic shock), platelet dysfunction and prolonged bleeding time, and gastrointestinal upset. Adult studies have demonstrated that the prolonged bleeding time that occurs with ketorolac is probably of little clinical importance.
Benzodiazepines are drugs that act as a sedative, anxiolytic, and amnesic, and they have no analgesic properties. They are frequently used in conjunction with pain medication when muscle spasm is a component of pain. Benzodiazepines potentiate the respiratory depressant effects of opioids and these combinations must be used with great caution.
Opioids
Opioids act on opioid receptors that exist in the brain, spinal cord, and opioid receptors that have been recently identified in the periphery—hence, the rationale for the administration of narcotics in joints. Four main pain receptors have thus far been identified (mu, delta, kappa, and sigma) in addition to a number of subgroups. Both endogenous (endorphin) and exogenous substances (opioid drugs) interact with these receptors to inhibit pain sensation.
Routes of Administration.
Opioids are administered by the IV, IM, oral, transmucosal, or transdermal route. They have been added to neuraxial anesthesia via the epidural or spinal route. The least reliable method to achieve a desired blood level of opioid is by the oral route, because most of the drug absorbed from the gastrointestinal tract undergoes first-pass metabolism in the liver before reaching the opioid receptors ( Table 8-5 ). IM opioid injection should be avoided in children because of the variable and unpredictable absorption of opioid via this route, and the fear of frequent injection may lead to denial of pain and refusal by the child for much needed analgesia. IV bolus administration of opioid has the advantage of rapid onset with a high level of efficacy in terms of pain relief. The disadvantages of an IV bolus of opioid include the relatively short duration of analgesic activity and labor-intensive nature of this route of administration ( Table 8-6 ).
| Medication | Ingredients | Usual Dosage |
|---|---|---|
| Acetaminophen + codeine elixir (Tylenol with codeine elixir) | Acetaminophen 120 mg + codeine 12 mg/5 mL | Acetaminophen, 15 mg/kg; codeine, 1 mg/kg/dose PO every 4 hr PRN |
| Acetaminophen + codeine tablets (Tylenol No. 3) | Acetaminophen 300 mg + codeine 15 mg/tablet | 1-2 tablets PO every 4 hr PRN |
| Morphine sulfate oral solution | Morphine sulfate 2 mg/mL | 0.3 mg/kg PO every 4 hr PRN |
| Acetaminophen + oxycodone (Percocet) | Acetaminophen 325 mg + oxycodone 5 mg | 1-2 tablets PO every 4 hr PRN |
| Acetaminophen + hydrocodone (Vicodin) | Acetaminophen 325 mg + hydrocodone 5 mg | 1-2 tablets PO every 4 hr PRN |
| Acetaminophen + propoxyphene (Darvocet) | Acetaminophen 650 mg + propoxyphene 100 mg | 1 tablet PO every 4 hr PRN |
| Acetaminophen 325 mg + propoxyphene 50 mg | 1-2 tablets PO every 4 hr PRN |
| Type of Pain | Dosage |
|---|---|
| Severe | 0.08 mg/kg IV every 2 hr PRN |
| Moderate | 0.05 mg/kg IV every 2 hr PRN |
| Mild | 0.025 mg/kg IV every 2 hr PRN |
Continuous Intravenous Infusion.
Continuous IV infusion of opioid (usually morphine sulfate) is used when patient-controlled analgesia (PCA) or regional anesthesia is not indicated. It is very important that a loading dose of opioid be administered before the initiation of continuous infusion of opioid. Patients on continuous infusion must be closely monitored because if excessive drug accumulates, respiratory depression will ensue. The need for reduction of the hourly dose must be considered if the child is to remain on continuous infusion for longer than 24 hours. The hourly rate is usually reduced by 10% for each additional day that continuous infusion of opioid is allowed to continue ( Table 8-7 ).
| Parameter | Dosage |
|---|---|
| Concentration: 0.1 mg/mL | Loading dose: 0.05 mg/kg every 10 minutes until analgesia is achieved |
| Age, 3-12 mo | 0.015 mg/kg/hr |
| Age, 1-7 yr | 0.025 mg/kg/hr |
Patient-Controlled Analgesia.
PCA provides the patient with an element of control in his or her pain management. The method is successful only after an adequate bolus injection of opioids is given to provide adequate analgesia. Subsequently the patient will receive a predetermined dose of opioid when she or he pushes the button on the PCA device. Advantages of PCA include a high level of efficacy coupled with lower side effects and high patient satisfaction. Children 6 to 7 years of age or older are capable of using a PCA device effectively. Younger children may benefit from an IV bolus or continuous infusion of opioids. In infants younger than 3 months, great caution must be exercised in the use of opioids, and the need to titrate to effect is of paramount importance. Clearance of opioid is very slow in these infants compared with clearance in older children. In addition, there is less protein binding of opioid, resulting in higher free active levels of opioids in the blood. Table 8-8 indicates how the PCA pump is to be programmed.
| Parameter | Dosage |
|---|---|
| Drug |
|
| Loading dose |
|
| PCA dose |
|
| Lockout interval or delay | Usual range, 7-12 min |
| 1-hr limit |
|
Regional Analgesia
The popularity and acceptance of the use of regional anesthesia for surgery and postoperative pain relief have undergone a dramatic increase in recent years. In no other specialty are the benefits of regional anesthesia more real and more accepted than in the orthopaedic surgical setting, in which the intraoperative and postoperative advantages of regional anesthesia have been clearly documented.
Regional analgesia is an extremely effective method of pain control for most patients. It provides effective pain relief with much smaller doses of narcotics and less sedation than parenteral opioids. The addition of very dilute local anesthetic will allow the patient to ambulate postoperatively. Motor blockade occurs uncommonly, but has been observed even with dilute bupivacaine (0.1%); therefore, the patient must always be accompanied by a nurse when ambulating.
Contraindications to regional anesthesia include the following:
- •
Sepsis
- •
Infection at the site or near the site of insertion
- •
Anatomic abnormalities (e.g., meningomyelocele, sacral dysgenesis)
- •
Coagulopathies and thrombocytopenia
It is advantageous to place the block at the beginning of the surgical procedure rather than at the end. Patients are often more alert and oriented in the postanesthesia care unit (PACU) because regional blockade obviates the need for intraoperative IV opioids and smaller amounts of anesthetic agents are required to maintain anesthesia. Interruption of nociceptive pathways at the spinal cord level may prevent imprinting of painful stimuli on the sensory cortex. Hence, patients who receive an intraoperative neural block may experience much less postoperative pain than those managed with general analgesia. It is well demonstrated that in certain conditions, such as patients who undergo limb amputation under a regional block, there is a decreased incidence of phantom pain.
Regional analgesia ranges from local infiltration of the wound edges to the administration of local anesthetics and/or opioid along the neuraxis (epidural or subarachnoid).
Epidural Analgesia
This is the most versatile analgesic technique in children undergoing thoracic, abdominal, perineal, and lower extremity surgery. The epidural space can be approached at any level, but is most frequently approached via the caudal or lumbar route. A caudal block is commonly used in younger children (6-7 years, weight ≤20 kg). Lumbar epidural is used in older children.
A catheter can be placed via a caudal or lumbar route and a variety of local anesthetics and/or opioids can be administered to maintain analgesia postoperatively. Typically, 0.1% bupivacaine plus a lipophilic opioid such as fentanyl is used for operations in the lower limb; 0.1% bupivacaine with a hydrophilic opioid such as morphine sulfate or hydromorphone is used when a larger number of dermatomes need to be blocked, as in scoliosis surgery.
Potential side effects of opioids in the neuraxis include respiratory depression, urinary retention, nausea and vomiting, and pruritus. The lipophilic agents (e.g., fentanyl) have less tendency to spread in a rostral direction because they tend to bind to the pain receptors in the spinal cord adjacent to the site of drug administration. The hydrophilic agents (e.g., morphine sulfate, hydromorphone) tend to spread further rostrally and have the potential to create respiratory depression. The hallmark of an impending overdose of epidural opioid is increasing sedation and decreasing depth of respiration before the respiratory rate decreases.
The most important monitor of the patient receiving an epidural opioid is the nurse who uses a stethoscope to detect the reduction in depth of respiration and level of sedation, rather than any electronic device. Therefore, education of the nursing staff is of utmost importance for creating a safe and effective pain service.
General Recommendations for Epidural Analgesia
- 1.
Administer the epidural at the start of the procedure whenever possible.
- 2.
Give no more than 2 mg/kg of bupivacaine as an initial loading dose after a standard test dose of lidocaine, 1.5% with epinephrine, 1 : 200,000, 0.1 mL/kg (maximum, 3 mL). Do not repeat the full loading dose intraoperatively.
- 3.
After an initial loading dose, infuse no more than 0.5 mg/kg/hr (= 0.5 mL/kg/hr of bupivacaine 0.1%).
- 4.
Always use the loss of resistance technique with saline.
- 5.
In general, the bolus for fentanyl is 1 µg/kg in 5 mL of preservative-free normal saline (NS). The bolus for hydromorphone (Dilaudid) is 10 µg/kg in 5 mL of NS. Bupivacaine 0.1% and fentanyl 2 µg/mL usually start at 0.2 mL/kg/hr (1 µg/kg/hr).
- 6.
Use a soluble liquid adhesive (e.g., Mastisol) for dressing the catheter.
Intravenous Regional Anesthesia
Intravenous regional anesthesia (IRA) of the upper extremity was first described by August Bier in 1908. This method uses an IV injection of local anesthetic into the involved limb while circulation to the limb is occluded. This form of regional block is often used for short surgical procedures (<90 minutes) distal to the elbow. Surgery on the arm proximal to the elbow is best managed with brachial plexus blockade. IV regional block is not suitable for lower extremity surgery because a large volume of local anesthetic solution would be required.
Indications
- •
Surgery on the arm proximal to the elbow
- •
Reduction of closed fracture of the forearm
Contraindications
- •
Sickle cell disease or trait; stasis of blood flow and acidosis promote sickling of red cells.
- •
Severe peripheral vascular disease or Raynaud disease.
- •
Cellulitis, infection, or venous thrombosis.
- •
Patient with history of heart block (severe bradycardia and asystole following tourniquet release has been reported even in patients with no myocardial conduction abnormality).
- •
History of epilepsy or hepatic disease.
- •
Full stomach; aspiration pneumonitis can occur if the patient seizes after tourniquet release from central nervous system toxicity of the local anesthetic.
Technique
The first step is the insertion of an IV catheter in the distal aspect of the limb involved in the surgical procedure. This usually means an IV catheter in the hand. There is evidence that inadequate or patchy anesthesia is more likely to occur when proximal veins such as the antecubital veins are used for the administration of local anesthetic.
- •
Insert another IV catheter in the opposite extremity and have equipment available for immediate resuscitation in case of an untoward reaction.
- •
Exsanguinate the surgical limb to ensure more complete analgesia. This can be achieved by an Esmarch bandage or elevation of the arm for 2 minutes.
- •
Apply a double tourniquet to the arm proximal to the operative site and fasten securely with an exterior bandage.
- •
Inflate the proximal cuff of the double tourniquet to 100 to 150 mm Hg above the patient’s systolic blood pressure.
- •
Inject the local anesthetic without vasoconstrictors slowly. A mottling of skin appears as the local anesthetic spreads. Muscular relaxation and complete analgesia usually develop within 10 minutes.
Most patients tolerate the tourniquet pressure for 30 to 40 minutes. Once the proximal tourniquet becomes uncomfortable, the distal tourniquet is inflated to the appropriate pressure and the proximal cuff is deflated. Because the distal cuff is placed over an anesthetized segment of arm, the patient should again tolerate the tourniquet for another 30 to 40 minutes. The double cuff method, therefore, allows for approximately 60 to 90 minutes of relatively pain-free tourniquet time.
- •
Allow at least 30 minutes from the time of the local anesthetic injection and release of the tourniquet. Deflate the tourniquet slowly over 10 minutes. Following tourniquet deflation, sensation and motor function rapidly return to the anesthetized limb.
- •
Vigilant monitoring of the pulse, blood pressure, electrocardiogram, and mental status is mandatory, especially after tourniquet release, to allow for the early detection of toxic reactions.
Peripheral Nerve Blocks
Ultrasound-guided upper and lower extremity blocks are increasingly popular in children and offer alternatives to neuraxial techniques. Procedures amenable to lower extremity blocks are mostly orthopaedic in nature. Unlike the upper limb, analgesia for lower extremity procedures frequently requires blockade of at least two peripheral nerves; for example, operations on the foot mostly require saphenous (or femoral) and sciatic nerve blocks. For anterior knee procedures, a femoral nerve block may be adequate. However, consideration should be given to adding an obturator nerve block to cover the medial aspect of the knee, whereas lateral femoral cutaneous nerve blockade is necessary when the lateral aspect of the knee is involved. Similarly, the sciatic nerve should be blocked when surgery involves the posterior aspect of the knee, such as in the case of anterior cruciate ligament repair when a hamstring allograft procedure is performed.
Local Anesthesia
Choice of Local Anesthetics
Prilocaine, 0.5%, 4 mg/kg, maximum dose, 500 mg, is the most rapidly metabolized amide and provides good anesthesia with minimal side effects. Theoretically, prilocaine could cause methemoglobinemia, especially if the total dose of prilocaine exceeds 600 mg in the 70-kg adult.
Bupivacaine, 0.25%, is no longer recommended for use in IRA because bupivacaine has greater cardiotoxicity and the affected patient may be difficult to resuscitate once toxic levels are attained. Lidocaine, 0.5%, has been extensively used for IRA at a dosage of 3 mg/kg. Side effects have included central nervous system toxicity, including dizziness, tinnitus, and convulsions. Cardiovascular toxicity from lidocaine includes hypotension, bradycardia, and electrocardiographic changes consisting of nodal rhythms, ventricular extrasystole, and cardiac arrest. Recently, IV regional anesthesia with low-dose lidocaine (1 mg/kg), 1% diluted to 0.125%, has been used for the closed reduction of forearm fractures in children with great success.
Side Effects of Local Anesthesia
Side effects of local anesthesia include central nervous system toxicity, ranging from mild dizziness and tinnitus to convulsions. In addition, cardiovascular toxicity may occur, ranging from mild transient bradycardia to cardiac arrest.
Toxic manifestations usually occur immediately following tourniquet deflation and correspond to the release of local anesthetic into the bloodstream. Thus, it is important to ensure a minimum tourniquet inflation period of at least 30 minutes. Rapid reinflation of the tourniquet immediately after the initial deflation can result in a reduced peak plasma anesthetic level and decreased incidence of side effects.
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