[Evaluation of safety and anesthetic effect for ultrasound-guided cervical plexus block]

To observe the influences upon the degree of diaphragmatic excursion during deep cervical plexus block at the third cervical vertebra (C3) and compare the safety and anesthetic effect of modified cervical plexus block by ultrasonic guidance and blocking of cervical plexus at one point.

Part I: 30 patients of ASA (American society of anesthesiologists) I-II scheduled for thyroid surgery were selected for bilateral cervical plexus block at C3 and bilateral skin nerve branches via ultrasonic guidance. Diaphragmatic excursion was recorded. Part II: 80 patients of ASAI-II scheduled for thyroid surgery were randomly divided into 2 groups: experimental group (Group U) and control group (Group C). In Group U, modified cervical plexus block was used to fix both sides of C3 and skin nerve branches. The anesthetic mixture with 2% lidocaine and 0.75% ropivacaine was injected. And anesthetic effects and complications were detected. In control group, traditional one-point method for blocking cervical plexus was employed.

High-frequency Doppler sonography could clearly visualize important neck structures and precisely guide the injection of mixture to the transverse process of C3. Diaphragmatic excursion decreased significantly at 15 and 30 min post-blocking (P < 0.05). And no paralysis of diaphragmatic muscle occurred. Hoverer 3 cases had partial diaphragmatic paralysis. Both blood pressure and heart rate increased significantly post-blocking in both groups (P < 0.05 or 0.01). In comparison with Group C, the range of blood pressure was notably lower at 10 and 20 min in Group U. And heart rate was notably lower at 5, 10, 20 and 30 min (P < 0.05 or 0.01). Furthermore the onset time of skin nerve branches was significantly shorter in Group U (P < 0.01). And the anesthetic effect score was better than that in Group C (P < 0.01). The incidence of complications, such as hoarseness, was significantly lower in Group U (12 cases in Group C but none in Group U, P < 0.01) and Horner's syndrome (2 cases in Group C). The number of cases requiring hypotensor and heart rate control drug was significantly smaller in Group U than that in Group C (P < 0.01).

The improving effect of ultrasound-guided cervical plexus block upon the degree of diaphragmatic movement is within the compensatory range of body. In comparison with the traditional one-point blocking of cervical plexus, the modified cervical plexus block with ultrasonic guidance offers better anesthetic effects, fewer complications and convenient anesthetic localization. Thus it may be clinically applicable.