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.