Anesth Analg 2002;94:1270-1271
© 2002 International Anesthesia Research Society
PAIN MEDICINE
Projected Complex Sensations After Interscalene Brachial Plexus Block
Mattias Casutt, MD,
Georgios Ekatodramis, MD,
Konrad Maurer, MD, and
Alain Borgeat, MD
Department of Anesthesiology, Orthopedic University Clinic Zurich/Balgrist, Zurich, Switzerland
Address correspondence and reprint requests to Alain Borgeat, MD, Chief of Staff, Anesthesiology, Orthopedic University Clinic of Zurich/Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. Address e-mail to aborgeat{at}balgrist.unizh.ch
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Abstract
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IMPLICATIONS: The development of projected complex sensations mimicking phantom pain after interscalene block is reported. The recognition of this entity is important because it may be confused with some other cardiac, esophageal, or visceral pathologies.
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Introduction
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Phantom pain is described as a strong misperception, the incidence of which is approximately 50%, of the presence of a limb after it has been amputated (1). This has to be differentiated from so-called phantom sensations—a misinterpretation of the mass, length, movement, and position in space of the deafferentated limb, which occurs in nearly 75% of patients after amputation (2). Pain from phantom sensations of a blocked part of the body has been reported after subarachnoid anesthesia (3) and IV regional anesthesia (4). Bromage and Melzack (5) described phantom sensations in 86% of patients after brachial plexus anesthesia. We report a case with complex sensations mimicking phantom sensations after an interscalene block (ISB).
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Case Report
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A 62-yr-old, ASA status II woman was admitted for right total shoulder replacement. The patient was otherwise healthy; she had no cardiac, esophageal, or visceral disease. The left shoulder was successfully operated on 1 yr earlier in our institution under ISB with catheter and general anesthesia with propofol target-controlled infusion technique (TCI). The anesthesia procedure had been uneventful. The patient was very satisfied with the postoperative analgesia management and therefore asked for the same type of anesthesia as the year before. She was premedicated with midazolam 7.5 mg orally 1 h before anesthesia. Before the ISB was performed, the patient was supine, her head was slightly turned on the opposite side, and her elbow was flexed with her right hand lying on her left chest. The interscalene brachial plexus was identified by using a nerve stimulator (Stimuplex-HNS II; B. Braun Melsungen AG, Melsungen, Germany) connected to the proximal end of the metal inner needle (Stimuplex A; B. Braun Melsungen AG). Contraction of the triceps was elicited on the first attempt with a threshold stimulation of 0.3 mA and an impulse duration of 0.1 ms. A catheter (Polymedic, 22-gauge with stylet; Te me na, Bondy, France) was introduced distally between the anterior and middle scalene muscles for 3 cm without producing dysesthesia or pain according to the "cannula over needle" technique. Then, the catheter was subcutaneously tunneled over 4 cm through an 18-gauge IV cannula and fixed to the skin with adhesive tape (Tegaderm; 3M Health Care, Borken, Germany). The ISB was performed with 20 mL of 0.75% ropivacaine and 20 mL of 0.5% ropivacaine and administered through the catheter, with the hand lying on the lower part of the left hemithorax. Within 20 min, the patient had a complete sensory block (inability to recognize cold temperature) and motor block (inability to extend the arm). General anesthesia was performed with TCI propofol (TCI pump, Graseby 3500; SIMS Graseby Limited, Watford, Herts, UK). Tracheal intubation was facilitated with rocuronium, and 0.1 mg of fentanyl was given before intubation. Surgery was uneventful and lasted 180 min. Upon arrival in the recovery room, the patient was fully awake and immediately complained about a constant, strong, and burning pressure pain in her right hand over the sternum; the pain was not modified by respiration. The pain intensity was 80 on a visual analog scale (VAS) from 0 to 100 (0, no pain; 100, worst pain imaginable). She explained she felt the pain located in her right hand on her chest (the last position of her arm before the ISB was done), although her hand was on her right side, slightly elevated, within the abductor splint. However, the shoulder was completely pain free (0 on the VAS), and the patient could not feel her arm and forearm. Electrocardiogram, creatine kinase, CK-MB, and troponin, which were all within normal range, were done to exclude cardiac ischemia. The patient received propacetamol 2 g IV and morphine 7.5 mg subcutaneously; these slightly reduced the pain on the thorax from 80 to 50 on the VAS. Six hours after the initial ISB, a continuous infusion of ropivacaine 0.2% for the next 72 h was started by using patient-controlled interscalene analgesia at a rate of 5 mL/h plus a bolus of 4 mL with a lockout time of 20 min. The VAS over the sternum (in her right hand, as reported by the patient) remained stable, at approximately 40, during the continuous infusion of ropivacaine for the next 72 h, although the shoulder and whole right upper limb were completely pain free. Rehabilitation was started as usual on the second day after surgery (VAS, 0). On the third postoperative day (72 h after the ISB), the interscalene catheter was removed. After the infusion of ropivacaine was stopped, pain on the thorax steadily decreased until it disappeared (VAS, 0) 2 h later. At this time, the patient also had no pain in the shoulder. After the analgesic action of ropivacaine had completely disappeared, there was no sign of brachial plexus or vagal nerve irritation.
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Discussion
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We report a first case of complex sensations mimicking phantom pain associated with ISB and analgesia through an interscalene catheter. The patient had constant, strong, and burning pressure pain over the sternum, corresponding to the last position of the arm before the brachial plexus block was performed. This pain lasted from the time she awoke from general anesthesia until the perfusion of ropivacaine was discontinued. It is interesting to note that the intensity of the pain was correlated with the concentration of the drug: it was maximal after the block (anesthetic concentration) and then decreased, but was still present, at the analgesic concentration.
We found one description of phantom sensations after an ISB (6). However, in this report, phantom sensations were reactivated in the forearm in the course of a new operation of an already amputated arm. Another case report described a painful misperception in the upper limb after IV regional anesthesia (4). This case presents some similarities with ours because the patient complained about weariness of an imaginary vertical arm position. Despite reassurance and repeated doses of fentanyl, the sensory disturbance was described as exhausting and intolerable. These phantom sensations disappeared only after the end of the anesthesia. The vertical position was used before the regional anesthesia was performed.
The perception of limb position during subarachnoid anesthesia was investigated by Isaacson et al. (7) in 40 patients. He demonstrated that proprioceptive memory involves a dynamic neuroplastic imprinting process. This process was influenced by limb or joint position before the initiation of spinal anesthesia, because a flexed limb as compared with a nonflexed limb had an increased incidence of phantom perception (7). The authors concluded that the flexed limb either imprints its position more intensely or is more susceptible to local anesthetic blockade, and, therefore, the capability to register limb position changes is lost. Higher afferent activity in a flexed limb may influence the development of a local anesthetic block, because it has been demonstrated that local anesthetic affinity is stronger for activated Na+ channels as compared with inactivated Na+ channels (8). This could explain in part the difference in joint position afferent imprinting on proprioceptive memory. Our observation is consistent with this hypothesis because our patient had a flexed elbow during performance of the ISB: the flexed limb imprints its position more intensely in the proprioceptive memory. There is also an additional imprint in the proprioceptive memory of the nonanesthetized part of the body, which is in direct contact with the blocked limb—in this case, the nonanesthetized sternum area that was in contact with the blocked right hand. This is consistent with the chest pain experienced by the patient.
It is also interesting that the pain severity was correlated with the local anesthetic concentration. This may imply a direct relationship between the intensity of the Na+ channel block and the pain. However, it is not known whether different kinds of Na+ channels, which have different sensitivities, are involved in this phantom process (7). Birbaumer et al. (9) demonstrated a functional relationship between cortical reorganization and phantom limb pain after regional anesthesia, suggesting that phantom limb pain might be modulated by behavioral or pharmacological interventions that modify cortical reorganization. Unfortunately, no neuroelectrophysiologic investigations have been performed on this patient.
In summary, we observed severe drug-concentration-dependent, post-ISB, complex sensations mimicking phantom pain over the sternum. The thorax pain was explained by the position of the hand before initiation of the ISB. Previous descriptions of phantom sensations after regional anesthesia have always been correlated with disturbances in the blocked limb. There are no reports about complex sensations mimicking phantom pain in a part of the body other than the blocked limb—this is therefore termed "projected complex sensations."
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References
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Accepted for publication December 18, 2001.
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Abstract
Introduction
