ULTRASOUND GUIDED PRE-EMPTIVE BILATERAL SUPRAZYGOMATIC MAXILLARY NERVE BLOCK FOR SEPTOPLASTY: A CASE SERIES.

The cause of postoperative pain after septoplasty is resection of the facial bones around the nasal cavity and Os nasale . The maxillary nerve is exclusively sensory and carries pain, temperature, and tactile information from the region below the orbits and above mouth, which includes lower eyelid, skin that covers the side of the nose, cheek, maxillary sinus, nasopharynx, nasal cavity, palate, upper teeth, upper lip, and dura mater of the middle cranial fossa. The sensory information from these areas moves along axons whose cell bodies are located in the trigeminal ganglion, located within Meckel’s cave. Thus SZMB can provide targeted anaesthesia.

The Pterygopalatine fossa bock (PPFB),  targets the maxillary nerve and sphenopalatine ganglion (SPG). There are several approaches for PPFBs , each associated with a different risk profile. Among them, supra-zygomatic approach is easy and safest as it makes use of the bony anatomy. Thus, SZMB serves as an ideal target, providing broad analgesic coverage and effectively anesthetize multiple structures.

Figure 2- Blue area indicates the supply of the maxillary nerve

Informed and written consent for the procedure was obtained and  patient educated on Numerical Pain Rating Scale  beforehand (0 for no pain, 5 for moderate pain, and 10 for the worst possible pain).

All patients kept nil orally for a minimum of 6 hours pre-operatively for solids sand 2 hours pre operatively for clear liquids. In the operating room, intravenous access secured, and a multiparameter monitor attached to record ECG (Electrocardiogram), SpO2 (Oxygen saturation), RR (Respiratory rate), NIBP (Non-Invasive Blood Pressure), ETCO2 (End Tidal Carbon dioxide).

Intravenous line secured with 18G to 20G cannula and intravenous fluids Ringer Lactate started. All patients were administered premedications- Inj.Midazolam 0.02 mg/kg IV, Inj glycopyrrolate 0.004 mg/kg and induced with Inj propofol 1.5mg/kg IV, Inj vecuronium 0.1 mg/kg IV and Inj. Fentanyl 2 mcg/kg IV for analgesia. Pre-oxygenation for 3 minutes with 100% oxygen at 6L/min followed by which using direct laryngoscope, appropriate size cuffed endotracheal tube used for intubation and fixed after confirmation of bilateral air entry on 5-point auscultation. Anesthesia maintained with FiO2 of 34% and minimum alveolar concentration of 1, with O2: Air: Isoflurane = 0.5 L/min: 2.5 L/min: 0.8 %.  

Suprazygomatic maxillary nerve block performed under aseptic precautions post induction of anesthesia and before commencement of the surgical procedure.

Procedure steps:

A curvilinear ultrasound probe was placed inferior and parallel to the zygomatic arch and angled approximately 45° towards the pterygopalatine fossa. The pterygomaxillary fissure was identified between the maxilla and sphenoid bone. A SonoPlex needle was advanced under ultrasound guidance. After negative aspiration, 5 mL of 0.25% levobupivacaine was injected in divided doses on each side, and adequate spread was confirmed.The procedure was repeated on the opposite side.

Figure 3- Approach for SZMB

Figure 4- USG image

Pain using NRS was noted upon the transfer to the postoperative care unit (PACU) when the patient could communicate at 0, 4 h, 6 h, 12 h, and 24 h. The cumulative dose of rescue analgesia was noted.

Duration at which rescue analgesia given was noted and was initiated with a NRS more than or equal to 4.

Figure 5- NRS pain score

The results of our study demonstrated a significant reduction in postoperative pain with SZMNB not only in the immediate postoperative period but also at all time points over 24 h after FESS.

The efficacy of the block may be attributed to the inhibition of nociceptive impulses transmitted through the sensory branches of the maxillary nerve and its effectivity in preventing both peripheral and central sensitisation, leading to the reduction of postoperative pain.

Our study used a guided suprazygomatic approach to block the maxillary nerve. This approach provides a safer trajectory due to reliance on the surrounding bony anatomical landmarks of PPF to provide a direct pathway for the needle to navigate through the pterygomaxillary fissure to the fossa, thereby minimising the risk of inadvertently introducing the needle into unintended locations, ensuring a higher level of safety.

In contrast, infra‑zygomatic approach directs the needle towards the infra‑orbital fissure, risking the needle entry into the orbit, and is associated with a higher rate of complications like haematoma formation and swelling over the cheek.

In addition to the primary objective , we also assessed for evaluation of the visibility of the operative field during surgery, the quality scale proposed by Fromm and Boezaart was used and surgeon satisfaction score based on a Likert 5‑point scale from 1 to 5 - very bad, bad, average, good, and excellent.

The operative field conditions were assessed by the operating surgeon as:

Grade 0: No bleeding.

Grade 1: Slight bleeding – No suctioning of blood required.

Grade 2: Slight bleeding – Occasional suctioning required. Surgical field not threatened.

Grade 3: Slight bleeding – Frequent suctioning required. Bleeding threatens surgical field a few seconds after suction is removed.

Grade 4: Moderate bleeding – Frequent suctioning required. Bleeding threatens surgical field directly after suction is removed.

Grade 5: Severe bleeding – Constant suctioning required. Bleeding appears faster than can be removed by suction. Surgical field severely threatened and surgery impossible

All the cases fall under grade 2, which implicates that the block not only abridges pain , but also improves the visibility of surgical field, maintains intra operative haemodynamics and  Likert score ranges 4-5 , assuring surgeon satisfaction.

Ultrasound guided suprazygomatic approach to maxillary nerve block provides excellent postoperative analgesia for patients undergoing septoplasty surgery without significant side effects

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