John A. Norton

Possible central anticholinergic syndrome following transdermal scopolamine in an ambulatory surgery patient

To the Editor, We share an interesting case wherein use of a scopolamine transdermal patch for postoperative nausea and vomiting (PONV) prophylaxis may have contributed to the delayed emergence of an ambulatory surgery patient. The patient gave written consent for publication of this article. A 28-yr-old female (height 1.65 m, weight 90 kg) with a history of obsessive-compulsive disorder treated with citalopram presented for elective outpatient ankle arthroscopy. On a previous occasion, she had experienced severe PONV following a similar procedure performed under general anesthesia. A decision was made to administer a regional technique (sciatic and saphenous nerve blocks) combined with an intravenous general anesthestic using propofol. In the preoperative holding area, a transdermal scopolamine patch 1.5 mg was placed behind the patient’s left ear for additional PONV prophylaxis. Following application of routine monitors and block placement, the patient was administered propofol 200 lg kg min iv which was titrated down to 150 lg kg min during the procedure. Oxygen was administered via nasal cannula at 2 L min while ventilation was monitored via capnography. For additional PONV prophylaxis, dexamethasone 8 mg iv and later ondansetron 4 mg iv were administered intraoperatively. After approximately 45 min of surgery, the patient’s heart rate began to increase (from 80 beats min baseline to 110 beats min), and fentanyl 100 lg iv was administered slowly for suspected pneumatic tourniquet pain. Following completion of the one-hour procedure and deflation of the tourniquet, the patient’s heart rate remained elevated. Administration of propofol was discontinued approximately 15 min prior to room departure, and she was moved to the recovery area with continued monitoring while breathing spontaneously—though unresponsive to either verbal or tactile stimulation. Ten minutes after her arrival in the postanesthesia recovery unit, the patient remained unresponsive with an elevated heart rate of 140 beats min and blood pressure of 120/70 mmHg. The patient’s oxygen saturation was 100% with nasal cannula oxygen, and on examination, her pupils revealed bilateral mydriasis, nearly unresponsive to light, and a disconjugate gaze. A gag reflex was also present. Over the next 30 min, blood gas, electrolyte, and blood glucose readings were ordered, with normal results, while her electrocardiogram showed sinus tachycardia. Consideration was given to the possibility of central anticholinergic syndrome, and the scopolamine patch was removed after being in place for approximately two hours. Our hospital’s internal medicine colleagues, who had been notified relatively early in the case, had begun preparations for further neurological evaluation, workup, and intensive care unit admission. A decision was made to administer physostigmine for possible diagnostic and therapeutic intervention. Over the next 30 min, physostigmine 1.5 mg iv was administered in 0.5 mg increments. Within minutes of administering the last 0.5 mg dose, the patient became responsive and followed commands. Her blood pressure remained stable while her heart rate decreased to her baseline. The patient was admitted to hospital overnight for observation, and she was discharged the next morning with complete resolution of the suspected anticholinergic signs and without further sequelae. J. A. Norton, DO (&) B. Khabiri, DO F. L. Arbona, MD A. J. Kover, MD The Ohio State University, Columbus, OH, USA e-mail: john.norton@osumc.edu

Ultrasound basics for the busy novice practitioner.

This chapter provides general ultrasound (US) information for those new to the use of this technology. The use of US guidance in anesthesia and other areas of medicine have undergone significant advancement only recently. The first US-guided regional block was described in 1994. Since that time, US machine technology has advanced rapidly with today’s machines being smaller, increasingly portable, more user friendly, and providing image resolution comparable with the larger and costlier ‘‘cart-based’’ machines. US guidance in anesthesia practice has multiple benefits, but perhaps 2 applications lend the greatest weight to ambulatory anesthesia practice: use for (i) regional anesthetic block placement and (ii) vascular access procedures. Presently, US machines come in a variety of brand names and types. Clinicians should understand where and how the use of this technology is expected to make the greatest impact in their daily practice. Doing so will help to focus on the many machine-specific features that may or may not be important to those interested in using US. Such options include

Ultrasound-guided supine posterior approach for popliteal sciatic nerve block

To the Editor: Blockade of the sciatic nerve in the popliteal fossa is used for anesthesia and analgesia below the knee. Two common techniques used today are the prone posterior and the supine lateral approaches [1, 2]. The posterior approach with prone positioning is time consuming and problematic, especially for patients who are large and/or difficult to sedate. The supine lateral approach requires passage of the needle through the large lateral muscle groups of the leg, which can be painful, though the parallel needle path to the ultrasound transducer is ideal for visualizing the needle. With a lateral approach, however, some anesthesiologists have difficulty keeping the needle in plane, given the separation between the lateral needle insertion point and the transducer position on the back of the leg. This approach is made more challenging in patients with large legs. We believe the ultrasound-guided supine posterior approach is a novel technique for blocking the two divisions of the sciatic nerve in the popliteal fossa. The patient is supine with the leg elevated (Fig. 1). The sciatic nerve is visualized with a high-frequency linear ultrasound transducer oriented on the back of the leg in the transverse plane to the sciatic nerve. The bifurcation of the common peroneal nerve and posterior tibial nerve is identified near the popliteal fossa. Lidocaine 1% is used to anesthetize the skin and subcutaneous tissue. A 50 mm block needle is introduced out-of-plane and guided into the space between the common peroneal and posterior tibial nerves. Local anesthetic is then injected and the spread pattern is observed. Frequently a single injection is sufficient for the local anesthetic to spread around both nerves. Occasionally one or twominor needle adjustmentsmay be required to obtain spread of local anesthetic around both nerves. We believe the advantages of the supine posterior approach are 4-fold: 1) it allows for supine positioning of the patient during block placement, 2) with an out-of-plane approach, the distance the needle tip must travel to the target is shortened, 3) the needle insertion point is adjacent to the transducer, and 4) the popliteal vessels are probably less likely to be traversed, as they are typically located anterior and medial to the nerves. Initially using an out-of-plane needle insertion approach has the disadvantage of poor needle visualization. However, as experience is gainedwith this approach, the anesthesiologistwill be able to discern needle tip location by locating tissue movement, using hydrolocation, or visualizing the tip of the needle. We choose to place the block needle in the space between the common peroneal and posterior tibial nerves for two reasons. First, faster onset may be achieved by blocking the sciatic nerve distal to its bifurcation [3]; and second, we like to think that aiming the block needle towards this fat-filled space (between the nerves)may provide an additionalmargin of safety by avoiding the popliteal vessels as well as minimizing inadvertent needle contactwith nerve(s) (shouldwe be uncertain of the needle tip location given the out-of-plane approach).

Seizure complicating placement of a nerve stimulator-guided infraclavicular block: could the use of ultrasound decrease the risk?

The case of a patient who suffered a seizure following a nerve stimulator-guided coracoid infraclavicular brachial plexus block, is reported. Following the seizure, an ultrasound machine was used to image the patients infraclavicular region, which showed an anatomical variation in the position of the axillary vein relative to the axillary artery. The use of ultrasound in regional anesthesia provides additional safety information beyond nerve stimulation, which may help decrease the likelihood of such complications.