CONTINUOUS interscalene block of the brachial plexus is a common technique for analgesia after total shoulder arthroplasty because it provides good postoperative analgesia. Paresis of the ipsilateral hemidiaphragm is a well-described side effect of this technique. 1Bilateral interscalene block is generally considered an absolute contraindication because total paresis of the diaphragm could lead to respiratory insufficiency. We report a case of bilateral continuous interscalene block of the brachial plexus after bilateral total shoulder arthroplasty.

A 61-yr-old woman with American Society of Anesthesiologists physical status II was admitted for bilateral total shoulder replacement. Her medical history was remarkable for a systemic lupus erythematosus for 27 yr without clinically apparent lung involvement. She had a spine decompression in 1998 with untreatable nausea and vomiting during the first three postoperative days because of opioids. Results of preoperative clinical investigations (chest radiography, electrocardiography, and blood test) were all unremarkable. Because of her past experience with morphine, the patient asked not to receive, if possible, any opioids for analgesia. After written informed consent was obtained from the patient, a regional analgesia technique was chosen. The day before surgery, spirometry was assessed using a Cardiovit AT 6 recorder (Schiller Reomed AG, Dietikon, Switzerland) in its spirometry configuration with the patient placed in a 45° semirecumbent position. Diaphragm excursion was assessed by ultrasonography using a Sonoline Prima ultrasonograph (Siemens Medical, Erlangen, Germany). With the patient lying supine in a 45° semirecumbent position, a 3.5-MHz convex transducer was placed posterolaterally at the midclavicular line, using the usual subcostal approach. The procedure was always repeated at the same location on both sides. After identifying the dome of the hemidiaphragm (right and left separately), its excursion was measured in the M mode during rest and maximal forced inspiration. Spirometry and diaphragmatic excursion measurements were repeated according to the same procedure at 8, 24, and 72 h after the first interscalene block (figs. 1 and 2). The patient was premedicated with 7.5 mg oral midazolam 60 min before anesthesia. Monitoring included a continuous three-lead electrocardiography, noninvasive blood pressure measurement, and pulse oximetry. A peripheral venous catheter was inserted on the left foot. On both sides (right side first, left side 15 min later), interscalene brachial plexi were 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 with a threshold stimulation of 0.34 mA/0.32mA, right and left sides, respectively. The impulse duration was 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 catheters were subcutaneously tunneled over 4 cm through an 18-gauge intravenous cannula and fixed to the skin with adhesive tape (Tegaderm; 3 M Health Care, Borken, Germany). The interscalene blocks were performed with 30 ml ropivacaine, 0.5% (right side, time t = 0; left side, t = 15 min). At t = 40 min, the patient had complete bilateral sensory block (inability to recognize cold temperature) and motor block (inability to extend the arms). General anesthesia was performed with propofol using the target-controlled infusion technique (TCI Deltec Graseby 3500, Laubscher Basel, Basel, Switzerland, and Diprifusor subsystem, AstraZeneca Ltd., Macclesfield, Cheshire, United Kingdom). Tracheal intubation was performed after injection of 40 mg rocuronium and 0.1 mg fentanyl. Surgery was uneventful and lasted 280 min. The patient underwent extubation 5 min after the end of surgery. Clinically, the patient was ventilating adequately with auxiliary breathing muscles (muscle intercostales, muscle scaleni, muscle sternocleidomastoidei) at a respiratory rate between 12 and 18 breaths/min. In the supine position, pulse oximetry without supplementary oxygen was 94%, and respiratory rate was 17 breaths/min. The patient did not subjectively have “shortness of breath,” and visual analog scale score was 0 (0 = no pain, 100 = worst pain imaginable). A continuous perfusion of 0.2% ropivacaine was started in the recovery room 6 h after the first block at a rate of 7 ml/h on each side (total volume administered = 14 ml/h) via  the interscalene catheters by two perfusion pumps (PERFUSOR®secura; B.Braun Melsungen AG). Plasma concentrations of total and free fraction of ropivacaine and α-1-acid glycoprotein were measured at t = 0, 0.5, 1, and 1.5 h and at t = 8, 24, 48, and 72 h (fig. 3). The total concentration of ropivacaine in plasma was determined by gas chromatography with a nitrogen-sensitive detector. The free concentration of ropivacaine was determined by coupled-column liquid chromatography with mass spectrometric detection using electrospray ionization, after ultrafiltration of the plasma samples. The concentration of α-1-acid glycoprotein was determined by an immunoturbidimetric method. The patient received supplementary oxygen, 2 l/min, via  a nasal tube while asleep. Pulse oximetry over the whole period was always 92% or greater, and the patient at no time reported shortness of breath. Respiration rate was assessed every 4 h and remained within 10–18 breaths/min during the whole study period. Physical rehabilitation was started from the first postoperative day with visual analog scale score = 0. With this analgesic regimen, the visual analog scale score remained 0 until the end of the observation term (72 h). During the first 48 h, the patient was cared for in the intensive care unit, and then he was transferred to the ward. No nausea or vomiting occurred during the first 72 postoperative hours, significantly increasing patient satisfaction.

Total shoulder arthroplasty is known to be associated with severe pain, hindering early rehabilitation. Continuous interscalene block of the brachial plexus is therefore an effective technique for analgesia. However, bilateral interscalene block of the brachial plexus is considered contraindicated because it could lead to acute bilateral phrenic nerve paralysis 1with respiratory insufficiency. It has been demonstrated that paralysis of the phrenic nerve is only partial when 0.2% ropivacaine is administered through the indwelling interscalene catheter, 2and therefore, in the current case, a bilateral interscalene catheter could be chosen.

In the current case, the hemidiaphragm motions were paradoxical in forced respiration on both sides at t = 8 h and still slightly paradoxical at t = 24 h, probably because of some residual effect of the initial block consistent with the results of our previous study. 2On the left side, the excursion of the hemidiaphragm was still slightly paradoxical after 72 h, which could be explained by the more proximal location of the interscalene catheter on that side. At t = 72 h, the right hemidiaphragm showed a diminished physiologic excursion (fig. 1). Despite a marked decrease of the forced vital capacity by 60% from 2,670 ml preoperatively to 1,100 ml postoperatively (fig. 2), the postoperative respiratory course of this patient was uneventful and well-tolerated. This is mainly explained by the help of the auxiliary breathing muscles (muscle intercostales, muscle scaleni, muscle sternocleidomastoidei), which were able to provide sufficient ventilation even in the supine position, as demonstrated by a physiologic respiratory rate and the oxygen saturation of more than 92% at all times.

There are few data that show the effect of acute diaphragm paralysis on ventilation caused by isolated bilateral phrenic nerve paralysis in humans. Wiebel et al.  3found a reduced vital capacity by 50% in six patients with bilateral phrenic nerve paralysis. Camfferman et al.  4reported a case of normal ventilation in an awake patient, even in the supine position. Stradling et al.  5showed that acute diaphragm paralysis in awake dogs did not impair ventilation because of a marked increase in rib cage expansion, reflecting intercostal and accessory muscle activity. In the current case, a decrease in pulse oximetry was at no time observed during the whole controlled period. This could be explained by an incomplete phrenic nerve paralysis—unilateral or bilateral—as already shown by Borgeat et al.  2The difference in diaphragm motion amplitude between the right and left sides at t = 72 h could eventually be explained by more proximal placement of the tip of the catheter on the left side.

Total and free venous ropivacaine concentration reached a peak (2.27 and 0.18 g/l, respectively) 15 min after application of the second interscalene block and then constantly decreased (1.12 and 0.12 g/l, respectively) within the first 90 min. With the start of continuous perfusion of 0.2% ropivacaine (14 ml/h), total ropivacaine concentrations steadily increased in parallel with the increase of α-1-acid glycoprotein (acute phase protein), whereas the free ropivacaine concentration, responsible for toxic reactions, remained stable until the end of the continuous perfusion (fig. 3). This confirms earlier results with continuous epidural infusion of ropivacaine 6and is in accordance with the knowledge that regional anesthesia or analgesia does not block the inflammatory reaction mediated mainly by the liberation of interleukin 6, responsible in part for the steady increase of α-1-acid glycoprotein. 7,8This acute phase protein increase has the potential advantage to buffer the free concentration of ropivacaine, providing in the context of a continuous infusion of local anesthetics a protective mechanism against toxic reactions.

Although bilateral interscalene block of the brachial plexus is generally considered contraindicated, this technique can be performed in some selected patients. An acute paresis of the diaphragm causing a decrease in spirometry of 60% was well-tolerated in this case. However, this practice should be reserved for selected patients who do not have pulmonary disease jeopardizing ventilatory function in particular. It is imperative that the patient is closely monitored in an intensive care unit or equivalent facility for at least the first 48 postoperative hours to assess patient's tolerance and enable prompt reaction in the event of major complications.

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