title: Real-time ultrasound-guided spinal anesthesia using the SonixGPS ultrasound guidance system: a feasibility study.
abstract: BACKGROUND
  Real-time ultrasound-guided neuraxial blockade remains a largely experimental technique. SonixGPS® is a new needle tracking system that displays needle tip position on the ultrasound screen. We investigated if this novel technology might aid performance of real-time ultrasound-guided spinal anesthesia.
  
  
  METHODS
  Twenty patients with body mass index < 35 kg/m(2) undergoing elective total joint arthroplasty under spinal anesthesia were recruited. Patients with previous back surgery and spinal abnormalities were excluded. Following a pre-procedural ultrasound scan, a 17G proprietary needle-sensor assembly was inserted in-plane to the transducer in four patients and out-of-plane in 16 patients. In both approaches, the trajectory of insertion was adjusted in real-time until the needle tip lay just superficial to the ligamentum flavum-dura mater complex. At this point, a 25G 120 mm Whitacre spinal needle was inserted through the 17G SonixGPS® needle. Successful dural puncture was confirmed by backflow of cerebrospinal fluid from the spinal needle.
  
  
  RESULTS
  An overall success rate of 14/20 (70%) was seen with two failures (50%) and four failures (25%) in the in-plane and out-of-plane groups respectively. Dural puncture was successful on the first skin puncture in 71% of patients and in a single needle pass in 57% of patients. The median total procedure time was 16.4 and 11.1 min in the in-plane and out-of-plane groups respectively.
  
  
  CONCLUSIONS
  The SonixGPS® system simplifies real-time ultrasound-guided spinal anesthesia to a large extent, especially the out-of-plane approach. Nevertheless, it remains a complex multi-step procedure that requires time, specialized equipment, and a working knowledge of spinal sonoanatomy.
authors.affiliation: Department of Anesthesia, Toronto Western Hospital, University Health Network, Toronto, ON, Canada.
authors.forename: A U
authors.initials: AU
authors.lastname: Niazi
authors.forename: K J
authors.initials: KJ
authors.lastname: Chin
authors.forename: R
authors.initials: R
authors.lastname: Jin
authors.forename: V W
authors.initials: VW
authors.lastname: Chan
mesh_terms: D000368:Aged; D000775:Anesthesia, Spinal / Q000379:methods*; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D015992:Body Mass Index; D003199:Computer Systems; D017558:Elective Surgical Procedures; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology; D017060:Patient Satisfaction; D011677:Punctures / Q000009:adverse effects / Q000379:methods; D018084:Ultrasonography, Interventional / Q000295:instrumentation*; D014743:Videotape Recording