Hariharan Shankar

Desflurane Enhances Reactivity during the Use of the Laryngeal Mask Airway

Background:Desflurane and sevoflurane have markedly different pungencies. The tested hypothesis was that patients breathing equivalent concentrations of desflurane or sevoflurane through a laryngeal mask airway (LMA) would have similar responses. Methods:After institutional review board approval and informed consent were obtained, 60 patients were enrolled and given intravenous midazolam (14 &mgr;g/kg) and fentanyl (1 &mgr;g/kg) 5 min before induction of anesthesia. The LMA was inserted at loss of consciousness after 2 mg/kg propofol. When spontaneous breathing returned, a randomly assigned volatile anesthetic was started at an inspired concentration of either 1.8% sevoflurane or 6% desflurane at a fresh gas flow of 6 l/min in air:oxygen (50:50). After 5 min, a controlled movement of the LMA took place. Three minutes later, the inspiratory anesthetic concentration was changed to either 3.6% sevoflurane or 12% desflurane for 3 min. A blinded observer recorded movements and airway events during the start of anesthetic, LMA movement, deepening of the anesthetic, and emergence before LMA removal. Results:There were no differences at anesthetic start and LMA movement. Desflurane titration to 12% increased heart rate, increased mean arterial blood pressure, and initiated frequent coughing (53% vs. 0% sevoflurane) and body movements (47% vs. 0% sevoflurane). During emergence, there was a twofold greater incidence of coughing and a fivefold increase in breath holding in the desflurane group. Conclusions:When airway responses to sevoflurane and desflurane were compared in elective surgical patients breathing through an LMA, there were significantly more adverse responses with desflurane at 12% concentrations and during emergence.

Potential adverse ultrasound-related biological effects: a critical review.

Ultrasound energy exerts important cellular, genetic, thermal, and mechanical effects. Concern about the safety of ultrasound prompted several agencies to devise regulatory limits on the machine output intensities. The visual display of thermal and mechanical indices during ultrasound imaging provides an aid to limit the output of the machine. Despite many animal studies, no human investigations conducted to date have documented major physiologic consequences of ultrasound exposed during imaging. To date, ultrasound imaging appears to be safe for use in regional anesthesia and pain medicine interventions, and adherence to limiting the output of ultrasound machines as outlined by the Food and Drug Administration may avoid complications in the future. This article reviews ultrasound-related biologic effects, the role of the regulatory agencies in ensuring safety with the use of ultrasound, and the limitations and implications of ultrasound use in humans.

Two‐ and Three‐Dimensional Ultrasound Imaging to Facilitate Detection and Targeting of Taut Bands in Myofascial Pain Syndrome

INTRODUCTION Ultrasound imaging has gained acceptance in pain management interventions. Features of myofascial pain syndrome have been explored using ultrasound imaging and elastography. There is a paucity of reports showing the benefit clinically. This report provides three-dimensional features of taut bands and highlights the advantages of using two-dimensional ultrasound imaging to improve targeting of taut bands in deeper locations. CASE REPORT Fifty-eight-year-old man with pain and decreased range of motion of the right shoulder was referred for further management of pain above the scapula after having failed conservative management for myofascial pain syndrome. Three-dimensional ultrasound images provided evidence of aberrancy in the architecture of the muscle fascicles around the taut bands compared to the adjacent normal muscle tissue during serial sectioning of the accrued image. On two-dimensional ultrasound imaging over the palpated taut band, areas of hyperechogenicity were visualized in the trapezius and supraspinatus muscles. Subsequently, the patient received ultrasound-guided real-time lidocaine injections to the trigger points with successful resolution of symptoms. CONCLUSIONS This is a successful demonstration of utility of ultrasound imaging of taut bands in the management of myofascial pain syndrome. Utility of this imaging modality in myofascial pain syndrome requires further clinical validation.

Retrospective comparison of ultrasound and fluoroscopic image guidance for intercostal steroid injections.

Introduction:  Steroid injection around the intercostal nerves is one of the treatment options for intercostal neuralgia. The technique may be performed blindly, under fluoroscopic guidance (FSG) or with the use of ultrasound guidance (USG). This study is a retrospective comparison of image guidance for intercostal steroid injections.

Targeting Myofascial Taut Bands by Ultrasound

Myofascial pain syndrome (MPS) is a frequent diagnosis in chronic pain and is characterized by tender, taut bands known as trigger points. The trigger points are painful areas in skeletal muscle that are associated with a palpable nodule within a taut band of muscle fibers. Despite the prevalence of myofascial pain syndrome, diagnosis is based on clinical criteria alone. A growing body of evidence that suggests that taut bands are readily visualized under ultrasound-guided exam, especially when results are correlated with elastography, multidimensional imaging, and physical exam findings such as local twitch response. The actual image characteristic in B mode appears to be controversial. Ultrasonography provides an objective modality to assist with diagnosis and treatment of trigger points in the future.

Ultrasound-Guided Localization of Difficult-to-Access Refill Port of the Intrathecal Pump Reservoir.

Introduction. Ultrasound guidance is being increasingly utilized in many chronic pain interventions. This is a report of the use of ultrasound imaging for accessing an intrathecal pump. Case Report. A 56-year-old patient with a programmable implanted intrathecal drug delivery system for chronic non-malignant pain needed a pump refill of sufentanil. Attempts to access the refill port using the manufacturer supplied template were difficult because of the presence of a seroma. Using ultrasound guidance, the seroma, reservoir, and the refill port were visualized and the pump was successfully accessed. This imaging-guided refill technique is fully described in this article. As the patient continued to have a collection of fluid during his following visit, the collection was aspirated under ultrasound guidance. The specimen revealed a proteinaceous collection with minimal quantities of sufentanil. Conclusion. This is a successful demonstration of ultrasound guidance to facilitate access to a difficult-to-access refill port of a pump reservoir secondary to the formation of a seroma.Introduction. Ultrasound guidance is being increasingly utilized in many chronic pain interventions. This is a report of the use of ultrasound imaging for accessing an intrathecal pump. Case Report. A 56‐year‐old patient with a programmable implanted intrathecal drug delivery system for chronic non‐malignant pain needed a pump refill of sufentanil. Attempts to access the refill port using the manufacturer supplied template were difficult because of the presence of a seroma. Using ultrasound guidance, the seroma, reservoir, and the refill port were visualized and the pump was successfully accessed. This imaging‐guided refill technique is fully described in this article. As the patient continued to have a collection of fluid during his following visit, the collection was aspirated under ultrasound guidance. The specimen revealed a proteinaceous collection with minimal quantities of sufentanil. Conclusion. This is a successful demonstration of ultrasound guidance to facilitate access to a difficult‐to‐access refill port of a pump reservoir secondary to the formation of a seroma.

Vasodilation from Sufentanil in Humans

Sufentanil is a potent opioid that occasionally has been associated with hypotension. The mechanism behind this hypotension is unclear. We hypothesized that sufentanil had a direct effect on vascular smooth muscle to cause vasodilation. Sufentanil was infused into the brachial artery of 10 young, healthy volunteers at rates of 0.083, 0.167, 0.333, and 0.833 &mgr;g/min. Forearm blood flow was measured in both the experimental and control arms with venous occlusion plethysmography. The forearm blood flow in the infused arm increased in a dose-dependent fashion from 3.2 to 5.2 mL/min per 100 mL of tissue whereas simultaneous measurements in the control (non-infused) arm did not increase. Heart rate and mean arterial blood pressure were unchanged during the infusions. Furthermore, respiratory rate did not change at any infusion level and sedation did not occur. Thus, the data support that significant systemic “spillover” of sufentanil did not occur. We conclude that sufentanil has a direct, vasodilatory effect on human vascular tissue that is likely independent of a neurogenic or systemic mechanism.

Phantom pain in a patient with brachial plexus avulsion injury.

OBJECTIVE Phantom limb pain is a painful sensation perceived in the absent limb following surgical or traumatic amputation. Phantom limb sensations, which are nonpainful, occur in nearly all amputees. Deafferentation can also produce similar symptoms. Here we report the presence of phantom pain in a deafferented limb. DESIGN Case report. SETTING Hospital-based outpatient clinic. PATIENT A 65-year-old man was referred to the pain clinic for management of upper extremity pain secondary to brachial plexus avulsion (BPA) following a motor vehicle accident. Initially he noticed a feeling of growing and shrinking of his arm. Following this, the pain started gradually from his elbow extending to his fingertips covering all dermatomes. He described the pain as continuous, severe, and sharp. He also described the arm as being separate from his existing insensate arm and felt as though the fist was closed with the thumb pointing out. On physical examination, he had no sensation to fine touch or pressure below the elbow. There were no consistent areas of allodynia. He had diffuse muscle wasting in all the muscle groups of his left upper extremity, besides winging of the scapula. Electrodiagnostic studies showed a left brachial plexopathy consistent with multilevel nerve root avulsion sparing the dorsal rami. CONCLUSION This is a report of phantom limb sensations and phantom pain following BPA in an intact but flaccid and insensate limb.

Transient Neuronal Injury Followed by Intravascular Injection During an Ultrasound Guided Stellate Ganglion Block

Ultrasound guidance for pain interventions is becoming increasing recognized as a useful imaging tool. One of the common interventions where it is gaining wider acceptance is during the performance of a stellate ganglion block. The following is a unique report where intravascular and neuronal injury occurred during the performance of an ultrasound guided stellate ganglion block followed by dysphagia. 41 year old male, with a diagnosis of complex regional pain syndrome, was referred to our clinic for further management. He underwent a diagnostic ultrasound guided stellate ganglion block after having tried conservative therapies. The stellate ganglion block provided him with complete pain relief for over five weeks. During a subsequent therapeutic stellate ganglion block, performed by an experienced pain medicine fellow with more than 50 ultrasound guided proceduresclinician, the patient developed a transient injury to the brachial plexus upon needle entry. Subsequent redirection and injection of an ml of injectate resulted in an intravascular injection producing tinnitus. After the tinnitus decreased, he underwent another stellate block using an out of plane approach without any further complications. Two days later, he reported chest and throat discomfort which resolved over the next few days possibly due to a retropharyngeal hematoma. He declined further interventions and was subsequently managed with 3 tablets of oxycodone a day. This report highlights the importance of vigilance and meticulous planning during the performance of ultrasound guided pain interventions.

Correlation between spinous process dimensions and ease of spinal anaesthesia

Background: Neuraxial anaesthesia, despite being a common technique, may pose some technical challenges leading to complications such as post-dural puncture headache, trauma to neural structures and neuraxial haematoma. We hypothesised that the interspinous gap (ISG) and the spinous process width (SPW) could be used as objective measures to predict ease of access to the neuraxial space. Methods: Two hundred and two consecutive patients scheduled to have spinal anaesthesia for various surgical procedures were enrolled prospectively after institutional approval. Following proper positioning for the neuraxial blockade, the ISG and SPW at the intended level were measured with calipers. The number of attempts, and redirections at the selected spinal level, and the number of levels required for successful needle placement were also recorded. Results: Group-wise analysis of the data into patients requiring >1 attempt, >1 level and ≥3 redirections showed that the single independent predictor of a difficult neuraxial block was the ISG. Twenty-three percent of the patients required more than one attempt, with a mean gap of 6.35 (±1.2) mm, in contrast to 8.15 (±2.4) mm in those with a single attempt (P=0.000). In addition, 16% of the patients needed more than one level, with a mean gap of 6.03 (±2.01) mm in contrast to 8.07 (±2.37) mm for a single level (P=0.000). Conclusions: The single independent predictor of ease or difficulty during spinal anaesthesia was the ISG (P=0.000).