Case presentation
A 11-year old Caucasian male, 33 kg, diagnosed with a maxillary Ewing’s Sarcoma, was admitted in February 2021 at Plastic Surgery and Maxillofacial Surgery Department of Ospedale Pediatrico Bambino Gesù in Rome for tumor removal and maxillary reconstruction using a free fibula flap.
At arrival in the operating room, standard monitoring with non-invasive arterial blood pressure, 3-lead electrocardiography and oxygen saturation was setted.
After preoxygenation, general anesthesia was induced and naso-tracheal intubation (6.0 mm preformed spiral tube) performed. Protective ventilation to maintain normal oxygen and CO2 end tidal levels in the range 30-40 was provided.
Anesthesia was conducted with Sevoflurane (MAC 1.5-2) and remifentanil (0.2-0.3 mcg/kg/min) to target BIS values between 40 and 50. We maintained permissive hypotension during tumor removal and isolation of the fibula flap, and instead higher blood pressure values after vascular anastomosis completion to ensure adequate perfusion of the free flap and its engraftment.
Before the surgical incision, ultrasound-guided Continuous Popliteal Sciatic Nerve Block was performed using a lateral approach.
A linear probe (8-12 MHz) was positioned transversely at the popliteal crease: the popliteal artery and vein were identified at a depth of 3 cm; laterally, biceps femoris muscles and medially the semimembranosus and semitendinosus muscles were identified. At a depth of 5 cm, the tibial and peroneal nerves were visualized joining together to form the sciatic nerve.
Guided by real-time ultrasound, a sterile 22-G Tuohy-type needle was cautiously advanced in-plane. After negative aspiration test, 10 ml of Ropivacaine 0.2% was administered within the sciatic nerve sheath (Vloka’s sheath) to separate both components of the nerve from adipose tissue and muscles. Drug spread was documented proximally and distally to the site of the injection.
The catheter was inserted 5 cm beyond the needle tip and its correct placement was documented by observing injection of local anesthetic within the sciatic nerve sheath; it was then secured through tunnelling and infusion regimen with Ropivacaine 0.2% 5 ml/h was started.
Surgery started 20 minutes after the block and, based on stable heart rate and blood pressure, there was no need of any rescue analgesia. (2)
As stated before, blood pressure was modulated according to different phases of the surgery. Permissive hypotension was the target during the first part when tumor asportation and preparation of the fibula flap were performed. Differently, during reconstruction phase, especially after completion of the vascular anastomosis and flap reperfusion, constant higher levels of blood pressure were maintained to ensure adequate perfusion of the graft, avoiding hypertensive peaks which instead would increase the risk of damage of the new anastomosis and bleeding.
To decrease the risk of thrombosis at the level of the vascular anastomosis, unfractionated heparin is administered immediately before reperfusion of the graft. Activated clotting time (ACT) was defined as point-of-care method to monitor the adequacy of intraoperative anticoagulation (target ACT >200 seconds).
A baseline ACT value was obtained and, if it was below the threshold on 200 seconds, administration of a bolus of 20 UI/kg of unfractionated heparin was performed. ACT was repeated 3 minutes later and then at regular intervals until the end of the surgery. Values were always above the threshold so no further administration of heparin was necessary.
At the end of the surgery a NIRS (Near Infrared Spectroscopy) probe was positioned over the skin area near the vascular anastomosis to monitor oxygenation of the free fibula flap. The probe was kept in place for the first 24 hours after surgery with values always above 92%. The goal was to detect in advance eventual hypoperfusion of the tissues which may contribute to the delay in the engraftment of the flap.
The patient was transferred to the postoperative Intensive Care Unit and was extubated 12 hours after the admission. On the 1st postoperative day the patient was discharged to the maxillofacial surgery ward and few hours later mobilized. The antalgic nerve sciatic catheter has been removed 4 days after surgery. The patient went back home after one week.