Mechanical Ventilation

Residual anesthesia is the most common cause of respiratory failure after surgery. Volatile agents used for anesthesia, benzodiazepines used to decrease anxiety, or opioids used to manage surgical pain may cause prolonged sedation and respiratory depression. Lung protective ventilation strategies should be used in patients needing continued mechanical ventilation postoperatively. Inspiratory volumes up to 8–10 mL/kg, positive end-expiratory pressure (PEEP) of 5–8 cmH ₂ O, and an age-appropriate respiratory rate should be used in patients with compliant lungs. In diseased lungs, acute lung injury, or respiratory distress syndrome, the mechanical ventilator volumes should be set to 4–8 mL/kg while maintaining plateau pressures of less than 30 cmH ₂ O and allowing for permissive hypercapnia.

Pediatric oncology patients may experience lung injury before surgery due to direct pulmonary toxicity from chemotherapy or radiation. Bleomycin, busulfan, cyclophosphamide, and nitrosoureas are chemotherapeutic agents known to cause rales, fever, and dyspnea at therapeutic levels. Methotrexate, cytarabine, ifosfamide, cyclophosphamide, interleukin (IL)-2, all-trans retinoic acid, and bleomycin may cause endothelial injury and vascular leakage, which can lead to noncardiac pulmonary edema. Dose-dependent radiation damage can present with cough, dyspnea, and pink sputum up to 3 months after treatment. One to two years after treatment, radiation damage can cause fibrosis, increased oxygen requirement, and decreased pulmonary function. Reviewing previous cancer therapies, current symptoms, chest imaging, and previous pulmonary function testing can provide helpful knowledge regarding lung damage.

Noninvasive Ventilation

Discontinuing mechanical ventilation immediately postoperatively decreases the risk of iatrogenic lung injury. The use of noninvasive positive pressure ventilation (NIV), continuous positive airway pressure (CPAP), or bilevel positive airway pressure (BiPAP) provides respiratory support when patients are recovering from anesthesia. These strategies provide respiratory support by preventing alveolar collapse in patients who are spontaneously breathing. Contraindications for NIV use include the following:

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  Patient’s inability to protect their airway

  
  
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  Glasgow coma scale <8

  
  
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  High risk of cardiac arrest

  
  
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  Hemodynamic instability

  
  
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  Rapidly progressive neuromuscular weakness

  
  
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  Unable to correctly fit the face mask (facial tumors, facial surgery)

  
  
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  Untreated pneumothorax

  
  
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  Vomiting or risk of aspiration

  
  
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  Skin breakdown that may be exacerbated by tight-fitting mask

High-Flow Nasal Cannula Therapy

High-flow nasal cannula (HFNC) therapy delivers heated and humidified oxygen via nasal prongs at recommended flow rates of 2–8 L/min for neonates and 4–70 L/min for children. An air-oxygen blender allows the percentage of oxygen delivered to the patient to be adjusted. HFNC is well tolerated in pediatric patients, from neonates through adolescence, and works to improve alveolar oxygen delivery through the generation of PEEP and dead space carbon dioxide washout. The heated and humidified flow prevents airway dryness, which preserves mucociliary function and enhances secretion clearance. Ideally, HFNC decreases the work of breathing and the need to escalate respiratory support to either CPAP or BiPAP and is often better tolerated than positive pressure ventilation with CPAP or BiPAP. HFNC may provide some positive pressure at sufficiently high flows, but this is limited due to multiple variables affecting the transmission of flow to the patient. The ability of HFNC to prevent the need for mechanical ventilation or to prevent mortality has been inconsistently supported in previous studies.

Pulmonary Hygiene

Pulmonary hygiene techniques, including traditional chest physical therapy, use postural drainage, percussion, chest wall vibration, and coughing to assist with airway clearance and maintenance. Postural drainage utilizes gravity to facilitate the movement of secretions from the peripheral airways to the larger bronchi. Percussion loosens secretions from the bronchial walls and can be performed in different positions, supporting postural drainage. Chest wall vibrations loosen or move bronchial secretions similar to percussion, but the clinician’s hand or device does not lose contact with the chest wall. Most sessions last 15–20 min and are scheduled 4–6 times per day. For acutely ill patients, pulmonary hygiene helps combat the hypoxemic effects of atelectasis, ventilation/perfusion mismatch, bronchospasm, or hypoventilation. Contraindications to pulmonary hygiene include increased intracranial pressure (>20 mmHg), spinal injury, active hemoptysis, hemodynamic instability, pulmonary embolism, pulmonary edema with congestive heart failure, or an open wound over the area where chest physiotherapy would be applied.

Pericardial and Pleural Effusions

Cardiac dysfunction from pericardial effusion can progress to cardiac tamponade if left untreated. Pediatric oncology patients at the highest risk for pericardial effusion are those with Hodgkin’s lymphoma or those who have received a hematopoietic stem cell transplant. The reported incidences in these patient populations are 5% to 25% and 0.2% to 16.9%, respectively. Pericardial effusion may occur due to graft versus host disease, infection, or immune suppression. Symptoms include tachycardia, S3, friction rub, narrow pulse pressure, dyspnea, cough, chest pain, electrocardiogram (ECG) changes (low voltage, electrical alternans, ST-segment elevation, or PR depression), pulsus paradoxus, Kussmaul sign (elevated jugular venous pressure with inspiration), and abdominal pain. The majority of pericardial effusions seen in patients with Hodgkin’s lymphoma are clinically silent and resolve with treatment of the underlying malignancy. Monitoring for the progression of pericardial effusion is performed using serial echocardiograms. Moderate to large effusions, as seen with hematopoietic stem cell transplantation, have a greater risk of life-threatening cardiac tamponade and require urgent pericardiocentesis. ^, Maintaining an appropriate fluid balance is essential for the management of pericardial and pleural effusions. A reduced preload due to under resuscitation could lead to cardiovascular collapse. By contrast, excessive administration of intravascular volume may worsen effusions.

Fluid Management

Postoperative fluid management should consider the type and length of surgery, estimated fluid deficit, ongoing fluid loss, and maintenance fluid requirements. Preoperative dehydration or inadequate intraoperative fluids may manifest as tachycardia, diastolic hypotension, or concentrated urine. Postoperatively, endothelial dysfunction results in capillary leak and may increase the risk of acute renal injury and the accumulation of pleural effusions and ascites. Normal saline solutions, PlasmaLyte, lactated Ringer’s solution, albumin, and blood products may be used for intravascular volume expansion. Although still controversial, albumin and fresh frozen plasma may have added benefits over large crystalloid volume infusion, protecting and repairing vascular endothelium. ^,

Postoperative laboratory studies should include a complete blood count, electrolyte levels, albumin, and coagulation studies to determine which fluid would provide the greatest benefit. Once euvolemia is established, intravenous maintenance fluids should be isotonic with appropriate amounts of sodium chloride, potassium chloride, and dextrose to help prevent hyponatremia, hypokalemia, and hypoglycemia. The use of hypotonic fluids in the postoperative period should be restricted to patients with sizeable free water losses, such as neonates and children with diabetes insipidus. In addition, surgical patients are prone to developing the syndrome of inappropriate antidiuretic hormone, leading to hyponatremia and fluid retention. Serum sodium levels should therefore be checked regularly after surgery and corrected appropriately in any patient with a seizure or decreased level of consciousness.

Inotropic Support

Postoperative hypotension should be treated with intravenous fluids or blood products until euvolemia is established. Early inotropic support should be considered in patients at risk of fluid overload and diastolic dysfunction. Hematopoietic stem cell transplant patients with endothelial damage are prone to a systemic inflammatory response after surgery, and fluid overload is detrimental to their overall survival. These patients may benefit from the inotropic, vasodilator, and lusitropic effects to improve cardiac output. Patients with preexisting preoperative or newly discovered postoperative heart dysfunction on echocardiography may benefit from milrinone’s inotropic and afterload reducing properties. Low-dose epinephrine in combination with milrinone can be used in hypotensive patients with poor contractility. Vasopressin can be used as a vasopressor to elevate systemic vascular resistance and improve organ perfusion. Norepinephrine can be used in patients with cytokine release syndrome or septic shock. Calcium infusions may also be used as inotropic agents in young children. ^,

Epidural/Regional Analgesia

In the past decade, an emerging concept in cancer surgery was the opioid-sparing analgesic approach with multimodal use of regional analgesia/anesthesia, acetaminophen, NSAIDs, gabapentin, and low-dose ketamine. The growing success of regional anesthesia has led to a decrease in the need for and length of opioid infusions. For example, in one large children’s hospital, local anesthetic infusions via peripheral nerve catheters increased 10-fold over 10 years. In addition, the need for PCA for narcotic delivery has decreased dramatically.

Continuous peripheral nerve blocks are increasingly used in children for postoperative pain control, especially after orthopedic cancer surgeries or extensive tumor resections. These nerve blocks are generally used for a few days, while swelling and pain are the most problematic. Nerve blocks may also be used to relieve intractable pain during end-of-life care. Thoracic surgeries for oncology patients are particularly painful. Nerve blocks have been reported to reduce pain scores, nausea, vomiting, pulmonary complications, and associated stress response markers. In a study involving 204 pediatric patients undergoing minimally invasive surgery, children undergoing thoracic surgery had significantly higher pain scores than those who underwent gastrointestinal surgery. These patients were treated with epidural analgesia and a combination of acetaminophen, morphine, ketorolac, tramadol, and ibuprofen.

Patient-Controlled Analgesia

PCA is an effective method for intravenous administration of opioids after surgery. The benefit is derived from the lack of a lag time between the demand for medication and its delivery. Most hospitals have protocols for using PCAs with options for continuous infusions, bolus infusions, and nurse and proxy (parent) administration. For example, in a Boston children’s hospital study, 32,338 PCAs were used over a 22-year period with an extremely low (1%) rate of adverse events. In this study, there were only five incidents where patients could administer larger bolus doses of opioids themselves.

Opioids

Opioids (e.g., morphine, hydromorphone, fentanyl) are the primary medications used to treat postoperative pain. Experimental research in cancer cells and in vivo animal models of cancer suggest that opioids facilitate cancer cell proliferation. However, other studies have demonstrated the opposite effect, reporting an inhibitory effect on cancer cells. Given the problems associated with opioid-related adverse events (ORADEs) opioid-sparing anesthesia (OSA) is gaining popularity in contemporary practice. OSA is administered, using dexmedetomidine, propofol, ketamine, and lidocaine infusions as appropriate; along with non-opioid adjuncts for analgesia utilizing acetaminophen, NSAIDs, gabapentinoids, and regional anesthesia in the absence of contraindications.

Ketamine and Dexmedetomidine

Dexmedetomidine infusions are often used postoperatively in the pediatric intensive care unit to manage pain and anxiety because the drug does not suppress the respiratory drive. The side effects of dexmedetomidine commonly include bradycardia and hypotension. Additionally, ketamine infusion provides sedation and pain control. One study in adults showed that low-dose continuous infusion of ketamine in mechanically ventilated patients was associated with a significant decrease in opioid use without adversely affecting hemodynamic stability.