|Year : 2017 | Volume
| Issue : 2 | Page : 69-72
Anesthetic consideration in a postchemotherapy pediatric patient for segmental mandibulectomy with free fibula reconstruction
Amit Kumar Mittal, Manoj Bhardwaj, Manisha Arora, Vani Bhageria
Department of Anaesthesiology, Rajiv Gandhi Cancer Institute, New Delhi, India
|Date of Submission||15-Oct-2017|
|Date of Acceptance||06-Nov-2017|
|Date of Web Publication||12-Dec-2017|
Dr. Amit Kumar Mittal
Department of Anesthesiology, Rajiv Gandhi Cancer Institute, Sector-5, Rohini, New Delhi - 110 085
Source of Support: None, Conflict of Interest: None
We report successful anesthetic management of a postchemotherapy pediatric patient having Ewing's Sarcoma mandible who underwent segmental mandibulectomy with free fibula reconstruction. The main challenges were securing difficult airway due to fragile mandible and maintenance of ideal blood rheostatic properties in an attempt to ensure optimal fluidity in microcirculation for the viability of flap. Other aspects of care like prevention of postoperative thrombosis of anastomotic vessels and need of tracheostomy for postoperative elective ventilation are being discussed.
Keywords: Chemotherapy, Ewing's Sarcoma, microvascular flap, pediatric anesthesia
|How to cite this article:|
Mittal AK, Bhardwaj M, Arora M, Bhageria V. Anesthetic consideration in a postchemotherapy pediatric patient for segmental mandibulectomy with free fibula reconstruction. Indian Anaesth Forum 2017;18:69-72
|How to cite this URL:|
Mittal AK, Bhardwaj M, Arora M, Bhageria V. Anesthetic consideration in a postchemotherapy pediatric patient for segmental mandibulectomy with free fibula reconstruction. Indian Anaesth Forum [serial online] 2017 [cited 2019 Aug 25];18:69-72. Available from: http://www.theiaforum.org/text.asp?2017/18/2/69/220561
| Introduction|| |
Ewing's Sarcoma (ES) of head and neck region among pediatric age involving mandible is rarely seen. The surgical treatment involves segmental mandibulectomy with free fibula graft reconstruction, which has profound implications on the anesthetic management due to pediatric age, extent and prolonged duration of surgery. The main challenges faced were difficult airway with a fragile mandible, thermoregulation, optimal fluid transfusion to counteract ongoing blood and fluid loss from wide exposed surface area. The blood rheology plays important role to maintain fluidity in microcirculation of small sized anastomotic conduits in transplanted tissue and thus optimal infusion of fluid and its monitoring plays crucial role. Extended care in postoperative period is necessary as elective ventilation, weaning, graft care, pain management and sedation are addressed by a well-planned strategy.
| Case Report|| |
A 2-year-old, 16 kg, nondiabetic male child was diagnosed with ES of the left mandible (cone-beam computed tomography showed expansile lytic lesion of 3 cm × 3.5 cm × 2 cm). After written informed consent from the parents, the child underwent segmental mandibulectomy with free fibula reconstruction. He received vincristine, adriamycin, cyclophosphamide/ifosfamide, carboplatin, and etoposide-based chemotherapy. Except mild anemia (Hb-9.8), preoperative investigations were within normal range. Preoperative airway assessment indicated difficult airway with Mallampati Class III.
The patient was induced with Sevoflurane 4%–6%, intravenous access was secured, and monitoring with SPO2, ETCO2 and noninvasive blood pressure (BP) started. The airway was secured with uncuffed endotracheal tube after optimal external laryngeal manipulation using Macintosh laryngoscope in the 2nd attempt. Anesthesia was maintained with mixture of O2+ air (50:50) with sevoflurane 2%–3% and Fentanyl infusion to keep MAC 0.8–1.0. Pressure control ventilation was used to keep ETCO2 in normal range. Patient was monitored for temperature, urine output, and hemodynamics (BP, systemic vascular resistance, and stroke volume variance) by FloTrac/EV1000 clinical platform FloTrac ™/EV1000™; (Edwards Lifesciences, Irvine, CA, USA) through left femoral artery [Figure 1].
|Figure 1: Hemodynamic parameters derived by FloTracTM/EV1000TM clinical platform, stroke volume variance and systemic vascular resistance values were derived (indicated by hollow arrows) but the stroke volume index and cardiac index could not be calculated as weight of the child was less than 30 kg|
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Extremities (except operating limb) were wrapped and covered with warming air blanket to prevent hypothermia. Peripherally inserted central catheter line was inserted in the right Basilic vein, central venous pressure (CVP) was monitored. Stroke volume variation (SVV) guided (target 4–10) lactate free fluid was transfused. Thereafter, elective tracheostomy was done with uncuffed PVC tracheostomy tube for postoperative ventilation [Figure 2].
|Figure 2: Facial symmetry in postreconstructed mandible by free fibular graft, retaining sutures were placed to hold tracheal stoma and tracheostomy tube in place|
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Polyuria noticed in the first 2 h of surgery (urine output >100 ml/h) was investigated. Blood gas analysis revealed hyperglycemia (RBS-359 mg/dl), metabolic acidosis (pH: 7.152, PCO2: 40 mm Hg, HCO3:13.7 mEq/L, SBE:-13.9), raised lactate (3.1 mMol/L) and hyponatremia (Na + 128 mEq/L). Metabolic derangement was corrected by insulin infusion and fluid transfusion, blood loss (240 ml) was replaced with 100 ml packed red blood cells. Out of 8 h of surgical duration, primary ischemia time was 73 min. Sedation with propofol and fentanyl infusion was continued for 48 h to aid elective ventilation on PCV mode. The child was gradually weaned off, decannulated, and discharged with healthy graft.
| Discussion|| |
Our important concerns in the anesthetic management were pediatric age group of patient and optimization of factors which could affect flap viability. The patient underwent segmental mandibulectomy with free fibula reconstruction and we encountered anticipated and unanticipated problems. First of all, after providing anesthesia, securing the airway with endotracheal tube required extra attempt with repositioning of head due to its large size and presence of mandibular tumor. Thereafter, in view of threat of disruption and kinking in anastomotic free flap vessels, tracheostomy, and postoperative elective ventilation was planned, as tracheostomy tube is better tolerated by conscious patients in not so cooperative and combative child. Tracheostomy in a pediatric patient may be associated with difficulties due to deeply placed trachea, short neck, and risk of premature extubation.
Another anticipated challenge was management of vital hemodynamic parameters and hematocrit due to ongoing blood loss from prolonged and compound surgery, necessitating blood transfusion to keep hematocrit ≤30. We instituted invasive hemodynamic monitoring to guide fluid therapy and stable hemodynamics to ensure adequate perfusion in transplanted graft. Although invasive hemodynamic monitoring by FloTrac is debatable in pediatrics age group we combined SVV, CVP trends, and urine output to guide fluid therapy.
Hyperthermia and hyperglycemia were unanticipated intraoperative events. Hypothermia is a common occurrence during prolonged surgery due to low ambient temperature and fluid transfusion, but we encountered hyperthermia (up to 38.7°C) in the later part of surgery, probably as a result of overcautious approach of using excessive drapes, warming blankets, and fluid warmer. Hyperthermia causes increase in basal metabolic rate, oxygen requirement and rise in ETCO2, requiring need for adjustment in ventilation to maintain normocapnia. We managed hyperthermia by taking out cotton wrapping, air warming blanket, and infusion of cold saline. Hyperglycemia has been reported in patients who received cyclophosphamide based chemotherapy. This drug increases the number of interferon-alpha producer in the islet and renders these lymphocytes more pathogenic and capable of destroying the islets of pancreas. Iphospamide can alter the glucose absorption from proximal tubules of nephrons and thus cause diuresis. Hyperglycemia has several implications on the anesthetic management and can have an adverse effect on graft survival. It leads to polyuria and thereby fluid loss and temporary hemodynamic instability along with interstitial tissue edema in transplanted tissue. Hence, we suggest preoperative glycosylated hemoglobin screening irrespective of age group in patients who receive chemotherapeutic agents with potential to precipitate diabetes.
Flap viability in a transplanted free flap is multifactorial. It depends on condition and size of anastomotic vessels, surgical skills and ischemia time (primary and secondary), ideal blood rheology, early detection of complications and postoperative care. The guiding principles and elements of anesthesia which provide laminar blood flow (Hagen–Poiseuille equation: Laminar flow = ΔP × r4 × π/8 × η × l) in anastomotic vessels are vasodilatation, good perfusion pressure and low viscosity.
Optimal blood flow thus provides adequate perfusion and flushing of debris after primary ischemic reperfusion reaction and help to modulate secondary ischemic insult. Optimal transfusion improves rheology by providing hyperdynamic circulation, higher cardiac output, higher pulse pressure, and peripheral vasodilation, thus ensuring adequate perfusion. On the other hand, fluid overload, microvascular venostasis, and significant interstitial edema (due to ischemic reperfusion injury) have additive effect on vascular leakage and cause tissue edema. Exaggerated tissue edema in turn creates undue extravascular pressure with deleterious effect on vascular diameter of flap. We closely monitored the volume status, hematocrit, and osmolarity (blood glucose) and thus minimized deleterious elements for flap viability and optimized blood flow in flap.
Other determinants which regulate regional blood flow and microvascular patency in transplanted flap tissue are PaO2, PaCO2, temperature, pH, and hematocrit.
Constant perioperative monitoring of vital parameters and timely intervention helped to keep them in physiological range, as any irregularity in these elements could impede fluidity in micro-circulation and result in flap failure. Both hypocapnia and hyperoxia causes vasoconstriction and decreases cardiac output, while hypercapnia causes sympathetic stimulation and reduces erythrocyte deformity. Keeping hematocrit in range of 28–30 is considered good for microcirculation, below 28 oxygen-carrying capacity of blood is decreased while hematocrit above 30 increases blood viscosity and impede fluidity in resistant arterioles.
| Conclusion|| |
Mandibular reconstruction with successful free fibula flap reconstruction in pediatric patient requires constant perioperative monitoring of physiological parameters and timely interventions to bring them within the normal range. Goal-directed fluid transfusion, maintaining hematocrit ≤30, thermoregulation, normocapnia, euglycemia, and prevention of compression on anastomotic vessels are crucial for flap viability.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]