What the Anesthesiologist Should Know before the Operative Procedure
Wilms’ tumor is the most common renal malignancy in children. The majority of Wilms’ tumors are sporadic mutations that cause proliferation of embryonal metanephric blastemal cells; the usual presentation is that of a healthy, preschool-aged child with an asymptomatic abdominal mass. Less commonly, Wilms’ tumors are associated with genetic syndromes, which themselves present anesthetic concerns separate from the malignancy.
In the United States, the National Wilms’ Tumor Study Group (NWTSG) recommends that clinical diagnosis and staging be followed by surgical staging and primary radical nephrectomy. Post resection management is guided by stage of disease. Presurgical chemotherapy may be considered in patients with bilateral renal involvement, unresectable tumor, or intravascular spread involving the inferior vena cava (IVC) or atrium.
This differs from the French Societe Internationale d’Oncologie Pediatrique (SIOP) recommendations that advocate preoperative chemotherapy for all patients. There is considerable controversy regarding which method is best. The anesthesiologist must therefore be aware of his/her institution’s philosophy of diagnosis and treatment of Wilms’ tumor to be best equipped to manage perianesthetic challenges.
Critical issues related to surgical intervention are directly related to the extent of disease, the presence of comorbidities, and the extent of surgical resection. Thorough preoperative evaluation, as described below, and meticulous intraoperative preparation minimize the risk of adverse events. While all children with Wilms’ tumor ultimately come to the operating room for a nephrectomy, the anesthesiologist may be confronted to care for these patients during nonsurgical procedures such as radiographic imaging and central venous access.
1. What is the urgency of the surgery?
What is the risk of delay in order to obtain additional preoperative information?
Surgical resection of Wilms’ tumor and nephrectomy is urgent, as delay can increase tumor burden and difficulty of surgical resection. However, comorbidities should be adequately assessed and optimized before the induction of anesthesia and surgery.
2. Preoperative evaluation
The standard preanesthetic history and physical should be performed, but the following may be noted specifically in patients with Wilms’ tumor. First, signs and symptoms of malignancy should be noted:
Uncontrolled/untreated hypertension may warrant delaying surgery
Respiratory symptoms related to pulmonary metastases or abdominal competition
Nausea, vomiting, and symptoms of delayed gastric emptying related to increased abdominal girth may warrant institution of medical therapy
Venous congestion related to IVC infiltration or involvement
Associated syndromes should also be noted:
WAGR (Wilms’ tumor, aniridia, genitourinary malformation, mental retardation)
Systemic effects of chemotherapy or radiation therapy are also pertinent to the preanesthesic history.
Radiographic imaging is essential to understand the extent of tumor burden and its impact on surgical resection and postsurgical management. First, physical compression of the viscera can slow gastric emptying or impair ventilation under anesthesia. Second, tumor involvement of the IVC or renal vein will have systemic effects while increasing the complexity of the resection. Last, lymphadenopathy and noncontiguous metastases will direct the oncologic plan (chemotherapy, radiation therapy, and surgical resection).
Echocardiography and electrocardiography, especially in the setting of previous anthracycline therapy (doxorubicin and daunorubicin), should be noted in the history, along with results of laboratory studies:
Basic metabolic panel specifically for renal impairment and electrolyte imbalance
Complete blood count specifically for anemia and thrombocytopenia
Coagulation studies; acquired von Willibrand’s disease may be seen
Type and screen
3. What are the implications of co-existing disease on perioperative care?
Diagnosis of Wilms’ tumor normally occurs in the first 5 years of life in patients who are generally healthy. Ten percent of cases, however, are noted in patients with genetic syndromes, as listed above. Details of the specific syndromes and their impact on perianesthetic management will not be described here. In the presence of one of the aforementioned syndromes, the anesthesiologist should be familiar with the specific nuances of the syndrome and their impact on anesthetic care.
a. Cardiovascular system
Anthracycline-induced cardiomyopathy may be seen in patients who have received presurgical chemotherapy. Preoperative echocardiography and an electrocardiogram should be obtained if this is a concern. Central venous pressure monitoring, in addition to standard monitors, may be useful in the judicious use of crystalloid and colloid therapy during the perioperative period.
Hypertension is present in 50% of patients with Wilms’ tumor, owing to renin production related to the tumor burden and compression. Long-standing hypertension can lead to intravascular contraction and hypertrophic cardiomyopathy. Achieving preoperative blood pressure control may minimize the risk of intravascular contraction and cardiomyopathy. Angiotensin-converting enzyme (ACE) inhibitors are effective for achieving this control. Lability in blood pressure during manipulation and resection of nephroblastoma may warrant invasive blood pressure monitoring.
Pulmonary metastases may be noted on chest radiography or computed tomography. Abdominal competition from tumor burden can diminish functional residual capacity and compromise oxygenation. Care must be taken to provide adequate tidal volumes and positive end-expiratory pressure during mechanical ventilation.
Increased abdominal girth and compression of tumor may cause nausea and vomiting and affect gastric motility. One may consider rapid sequence induction to facilitate endotracheal intubation. Renotoxic drugs should be used cautiously due to renal involvement of the tumor.
There are reports in the literature about spinal cord compression from the tumor’s metastases Physical exam and imaging studies should be thoroughly reviewed to fully understand the extent of disease. This is a relative contraindication to neuraxial analgesia in the perioperative period.
There are no general endocrinopathies associated with Wilms’ tumor. If Wilms’ tumor is presenting in a syndromic child, the anesthesiologist should understand the endocrinopathies associated with the specific syndrome.
Coagulopathy may be present as an acquired von Willibrand’s disease. Although rare, platelet dysfunction and coagulopathy should be assessed prior to the development of the anesthetic plan, not only to allow for ordering of appropriate blood replacement therapy but also to offer neuraxial analgesia.
Anemia and thrombocytopenia related to presurgical chemotherapy may be present.
Venous stasis related to IVC compression may be present.
4. What are the patient's medications and how should they be managed in the perioperative period?
Relatively healthy preschool-aged children usually are not on chronic medications at the time of surgery. Medication initiated at the time of diagnosis may be continued.
Antihypertensive medications should be continued until the day of surgery to prevent intravascular volume contraction and risk of cardiomyopathy. Antireflux/antiemetic medications may be continued through the perioperative course for symptomatic relief.
g. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
ACE inhibitors are the antihypertensive of choice in children who present with labile hypertension at the time of diagnosis. These medications are necessary to manage the higher levels of renin related to tumor burden and compression.
Hypotension during induction and maintenance of anesthesia in patients on ACE inhibitors is a well-known phenomenon. The anesthesiologist should be prepared to treat labile blood pressure during the perioperative period.
h. What should be recommended with regard to continuation of medications taken chronically?
Generally, chronic medications may be continued until the day of surgery. Most commonly, these include antihypertensives and inhalers/nebulizers for reactive airways disease. Parents should be instructed to stop all herbal medications, as well as antiplatelet medications, 2 weeks prior to surgery.
i. How to modify care for patients with known allergies –
As part of standard procedure, the anesthesiologist should be aware of any allergies the patient may have to drugs, adhesives, or foods.
j. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
k. Does the patient have any antibiotic allergies – [Tier 2 – Common antibiotic allergies and alternative antibiotics]
Perioperative antibiosis for the prevention of surgical site infection is usually given in the form of a first-generation cephalosporin for gram-positive skin flora. In the case of a penicillin-allergic patient, the anesthesiologist should assess for the likelihood of cross-reactivity to cephalosporins. If an alternative antibiotic is needed, clindamycin may be used.
l. Does the patient have a history of allergy to anesthesia?
Patients with Wilms’ tumor do not have an increased risk of malignant hyperthermia (MH). Standard questions regarding exposure history and risk should be asked.
If a history of MH has been documented, avoid all trigger agents such as succinylcholine and inhalational agents. The proposed general anesthetic plan is total intravenous anesthesia with nondepolarizing muscle relaxation. Ensure that an MH cart is available. If a family history of or risk factors for MH exists, total intravenous anesthesia with nondepolarizing muscle relaxation is recommended.
5. What laboratory tests should be obtained and has everything been reviewed?
Common laboratory normal values will be the same for all procedures, varying with age and gender.
A complete blood count should be obtained to assess hemoglobin concentration and platelet count, as well as a complete metabolic panel to assess electrolytes, renal function, and liver function. A coagulation panel should also be obtained to assess for the presence of acquired von Willibrand’s disease or other coagulopathy. A type and crossmatch for blood product administration is also recommended.
Imaging procedures may also be helpful in assessing anesthetic management of patients with Wilms’ tumor. Abdominal imaging (CT, MRI, US) can assess the extent of tumor burden, echocardiography can assess cardiac function (in the setting of anthracycline use) or atrial extension of tumor, and a chest radiograph can assess metastases and/or pulmonary involvement.
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
General anesthesia with or without neuroaxial blockade is the anesthetic of choice for this intra-abdominal procedure in the pediatric patient. A balanced anesthetic that provides amnesia, akinesia, and analgesia should be developed. There is no evidence to suggest that any one anesthetic technique is superior.
Epidural analgesia may be provided as an adjunct to general anesthesia and for postoperative analgesia. Care must be taken that there are no absolute or relative contraindications to the placement of an epidural catheter. Generally, epidurals are placed after the induction of general anesthesia in the pediatric patient. If no contraindications exist, a mid-thoracic epidural would cover the surgical incision for nephectomy.
Neuraxial techniques would provide adequate analgesia but would not be useful as a sole anesthetic in the pediatric patient. If neuraxial anesthesia is desired, an epidural catheter would be placed after the induction of general anesthesia. The anesthesiologist may choose to use the epidural catheter intraoperatively or solely for postoperative pain control.
The benefits of neuraxial anesthesia include decreased intraoperative and postoperative narcotic use and decreased side effects from intravenous narcotic use. The drawbacks to neuraxial anesthesia include difficulty covering the entire surgical site, depending on size of incision, and a potential for hemodynamic instability during the resection, which may preclude the intraoperative use of epidural catheter.
Peripheral nerve block techniques would not be useful for this procedure.
General anesthesia with inhaled anesthetic or intravenous anesthetic is necessary for the surgical treatment of Wilms’ tumor. Muscle relaxation enhances conditions for positioning, abdominal wall relaxation, and surgical manipulation. A balanced technique with an amnesic agent (volatile agent or intravenous agent), intravenous narcotic or epidural analgesia, and muscle relaxant is the anesthetic of choice.
Monitored Anesthesia Care
Monitored anesthesia care would not allow appropriate conditions for the surgical treatment of Wilms’ tumor.
6. What is the author's preferred method of anesthesia technique and why?
General anesthesia with a balanced technique of inhaled agent, muscle relaxant, and narcotic would be the author’s preferred method of anesthesia technique, as it provides the best conditions for surgical resection. It would be challenging to provide a neuraxial-based only anesthetic in the pediatric patient. Similarly, monitored anesthesia care would not provide adequate conditions for surgical exposure. Furthermore, the hemodynamic lability that is possible during surgical resection warrants full control of the airway.
What prophylactic antibiotics should be administered?
The vascular manipulations required during a nephrectomy warrant gram-positive coverage that cefazolin provides. Any special techniques that might be required by the surgeon should be communicated, as this might require gram-negative or anaerobic coverage in addition to cefazolin.
What do I need to know about the surgical technique to optimize my anesthetic care?
Patient positioning will depend on tumor burden and the surgeon’s strategy for removal; the patient may be positioned in a lateral or supine position. Care should be taken to protect extremities from pressure and nerves from compression or stretch. The surgical approach may involve laparoscopy. The surgeon’s approach should be discussed before planning for neuraxial analgesia.
If the tumor has invaded the IVC or atrium, the surgical plan may involve venoveno bypass or cardiopulmonary bypass. Such techniques should be discussed during the preoperative process; access for such techniques and patient position may be affected by this plan. Manipulation of the tumor can cause lability in blood pressure. The surgeon may or may not tie off the renal vein to decrease the intravascular spread of renin or other vasoactive substances. This should be discussed with the surgeon.
Capsule rupture and tumor spillage have been implicated in upstaging of disease. The surgeon may take great care to prevent this from occurring at the expense of IVC patency. This could cause transient decreases in preload and subsequent hypotension.
What can I do intraoperatively to assist the surgeon and optimize patient care?
Muscle relaxation may help with surgical exposure and exploration. Guiding the administration of neuromuscular blockade with a twitch monitor is recommended. Cell Saver is not recommended.
Controlled hypotension is not recommended, especially in the setting of preoperative hypertension. The patient’s blood pressure should be maintained within a normal range.
What are the most common intraoperative complications and how can they be avoided/treated?
Blood loss and the potential for hemorrhagic shock are common intraoperative complications. The anesthesiologist should be watchful of the blood loss and have blood products available for rapid transfusion
Compression of IVC during surgical exploration can be avoided with open communication with the surgeon regarding hypotension.
Labile blood pressure due to tumor manipulation can be mitigated using short-acting vasoactive medications to increase and decrease blood pressure. These medications should be available to be given in infusion and bolus forms, as needed during the procedure.
To avoid decreased functional residual capacity due to abdominal girth and abdominal competition, ensure adequate tidal volumes and positive end-expiratory pressures during mechanical ventilation. Consider CPAP during the induction of anesthesia to maintain FRC.
Pulmonary embolus from the tumor is a possible complication, if the renal vein or IVC has been invaded by the tumor.
a. If the patient is intubated, are there any special criteria for extubation?
Use standard criteria for extubation.
b. Postoperative management
What analgesic modalities can I implement?
Epidural analgesia or parenteral narcotics can be used for postoperative pain control. These patients are often too young for patient-controlled analgesia.
What level bed acuity is appropriate?
Postoperative care should be guided by the complexity of the case. If large volumes of crystalloid and colloid fluids are required for resuscitation or if there are any concerns for postoperative hypotension, hypertension, or ventilation, an intensive care unit (ICU) bed should be requested.
What are common postoperative complications, and ways to prevent and treat them?
Hypertension can persist for up to 2 weeks postoperatively, until the renin-angiotensin system normalizes. Intravenous and oral medications should be continued until blood pressure normalizes within a safe range. Adequate pain control should be provided to enable pulmonary toilet.
What's the Evidence?
Whyte, SD, Ansermino, JM. “Anesthetic considerations in the management of Wilm's tumor”. Pediatr Anesth. vol. 16. 2006. pp. 504-13.
Pritchard-Jones, K. “Controversies and advances in the management of Wilm's tumour”. Arch Dis Child. vol. 87. 2002. pp. 241-4.
Shiratori, T, Fujisawa, T, Ichino, T, Mitono, Y, Inokuti, M, Ohata, J. “Anaesthetic management of a patient with the intracardiac extension of Wilm's tumour”. Pediatr Anesth. vol. 14. 2004. pp. 361-4.
Evans, P, Chisholm, D. “Anesthesia and pediatric oncology”. Curr Anaesth Crit Care. vol. 19. 2008. pp. 50-8.
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- What the Anesthesiologist Should Know before the Operative Procedure
- 1. What is the urgency of the surgery?
- What is the risk of delay in order to obtain additional preoperative information?
- 2. Preoperative evaluation
- 3. What are the implications of co-existing disease on perioperative care?
- a. Cardiovascular system
- b. Pulmonary
- c. GI-Renal
- d. Neurologic
- e. Endocrine
- f. Hemotology
- 4. What are the patient's medications and how should they be managed in the perioperative period?
- g. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
- h. What should be recommended with regard to continuation of medications taken chronically?
- i. How to modify care for patients with known allergies -
- j. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
- k. Does the patient have any antibiotic allergies - [Tier 2 - Common antibiotic allergies and alternative antibiotics]
- l. Does the patient have a history of allergy to anesthesia?
- 5. What laboratory tests should be obtained and has everything been reviewed?
- Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
- 6. What is the author's preferred method of anesthesia technique and why?
- What prophylactic antibiotics should be administered?
- What do I need to know about the surgical technique to optimize my anesthetic care?
- What can I do intraoperatively to assist the surgeon and optimize patient care?
- What are the most common intraoperative complications and how can they be avoided/treated?
- a. If the patient is intubated, are there any special criteria for extubation?
- b. Postoperative management