Efficacy of ultrasound-guided mandibular block in predicting safer anesthetic induction

Mandibular nerve block reverses the trismus caused by pain and muscle spasm, thereby allowing for selection of a safer intubation technique.

As ultrasonographic imaging has added newer dimensions to clinical anesthesia practice, we utilized this tool in performing mandibular nerve block and evaluated its efficacy in segregating trismus patients on etiological basis, to predict safer anesthetic induction.

Prospective, randomized controlled, outcome assessor blinded trial.

Sixty-eight patients with unilateral mandibular fracture, acute pain, and trismus were randomized to receive mandibular nerve block by Vazirani-Akinosi approach (Group V) or the ultrasound-guided (USG) technique (Group U) before the general anesthetic induction for corrective surgery. Visual Analog Scale (VAS) score and inter-incisor distance was measured at intervals. Primary outcome measure was blocked failure (continued pain [VAS > 30] after the block procedure).

Mann-Whitney U-test and Wilcoxon signed rank test.

There was a significant decrease in pain score following the block procedure, except for six patients (block failure) in Group V. Inter-incisor distance increased to near-maximal levels after the nerve blockade, except for nine patients in Group V (including all block failures) and four in Group U having continued limited mouth opening. General anesthetic induction increased the inter-incisor gap in block failures (Group V) only.

USG mandibular block appears to relieve reversible trismus more reliably, thereby allowing for a precise decision on a safer intubation technique.