The Infiniti Plus ultrasound needle guidance system improves needle visualization during the placement of spinal anesthesia

popularity over the last two decades [1]. This new application of technology also facilitates spinal anesthesia in patients with challenging anatomy, such as those with scoliosis or obesity, or elderly patients [2,3]. Infiniti Plus (CIVCO Medical Solutions, Kalona, IA, USA) is a needle-guidance system that was recently developed to assist clinicians in performing ultrasound-guided nerve blocks. A needle-guidance system allows efficient needle movement with improved needle shaft and tip visualization. A needle-guidance system has been used for peripheral nerve blocks with a high-frequency ultrasound probe [4]. We used the Infiniti Plus needle-guidance system with a low-frequency ultrasound probe in spinal anesthesia administered by a single physician to two patients with difficult spinal anesthesia. A 62-year-old man was scheduled for left total hip replacement. He weighed 96 kg and had a body mass index of 30.4 kg/m. The L3-L5 spinous processes were not palpable, and the precise neuraxial midline was difficult to determine clinically. After obtaining informed consent, standard American Society of Anesthesiologists monitors and intravenous access was established and premedication with midazolam 2 mg and fentanyl 50 μg was given. He was positioned in the sitting position. Three trials of subarachnoid access without ultrasound guidance by an experienced anesthesiologist failed: bone was encountered in two trials, while in the third trial the cerebrospinal fluid (CSF) flow was not consistent (slow flow initially and no CSF was returned in the other three quadrants after turning the needle). Subsequently, spinal anesthesia was successful with an ultrasoundguided needle-guidance system at the first attempt. The second case was a 62-year-old man who was scheduled for total hip replacement. Spinal anesthesia had been unsuccessful in the past. His medical history included kyphoscoliosis. No lumbar X-ray was available for a more detailed anatomical examination. On palpation, it was difficult to determine the midline. He initially refused spinal anesthesia, as his previous experience was traumatic, and he had back pain after the previous procedure. After discussion, he agreed to proceed with spinal anesthesia under ultrasound guidance. After obtaining informed consent, routine monitoring and intravenous access premedication was given for a spinal anesthesia procedure with an ultrasound-guided needle-guidance system, and spinal anesthesia was successful at the first attempt. We used the SonoSite S nerve (SonoSite, Bothell, WA, USA) ultrasound machine with a low-frequency (2–5 MHz) curvilinear transducer. The ultrasound probe was covered with a sterile sleeve with sterile gel applied on the probe of the Infiniti Plus needle-guidance system (Fig. 1). The ultrasound probe was held in the left hand and the needle in the right hand at the cliniLetter to the Editor