Department of Anesthesiology and Pain Medicine, School of Medicine, Catholic University of Daegu, Daegu, Korea

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1 Anesth Pain Med 2011; 6: 270~274 Case Report Femoral and sciatic nerve blocks for total knee replacement in an obese patient with a previous history of failed endotracheal intubation A case report Department of Anesthesiology and Pain Medicine, School of Medicine, Catholic University of Daegu, Daegu, Korea Jong Hae Kim, Woon Seok Roh, Jin Yong Jung, Seok Young Song, Jung Eun Kim, and Baek Jin Kim Peripheral nerve block has frequently been used as an alternative to epidural analgesia for postoperative pain control in patients undergoing total knee replacement. However, there are few reports demonstrating that the combination of femoral and sciatic nerve blocks (FSNBs) can provide adequate analgesia and muscle relaxation during total knee replacement. We experienced a case of successful FSNBs for a total knee replacement in a 66 year-old female patient who had a previous cancelled surgery due to a failed tracheal intubation followed by a difficult mask ventilation for 50 minutes, 3 days before these blocks. FSNBs were performed with 50 ml of 1.5% mepivacaine because she had conditions precluding neuraxial blocks including a long distance from the skin to the epidural space related to a high body mass index and nonpalpable lumbar spinous processes. This case suggests that FSNBs can provide a good alternative anesthetic method for total knee replacement. (Anesth Pain Med 2011; 6: ) Key Words: Femoral nerve, Intubation, Nerve block, Sciatic nerve, Total knee replacement. are situations in which spinal or epidural anesthesia cannot be conducted, such as coagulation disturbances, sepsis, local infection, immune deficiency, severe spinal deformity, severe decompensated hypovolemia and shock. Moreover, factors associated with technically difficult neuraxial blocks influence the anesthesiologist s decision to perform the procedure [1]. In these cases, peripheral nerve block can provide a good solution for operations on a lower extremity. The combination of femoral and sciatic nerve blocks (FSNBs) has frequently been used for postoperative pain control after total knee replacement [2]. However, there are few reports demonstrating that FSNBs can provide an adequate anesthesia during a total knee replacement. We experienced a case of successful FSNBs for a total knee replacement in a 66 year-old female patient who had a history of failed tracheal intubation and conditions precluding neuraxial blocks. Spinal or epidural anesthesia has gained widespread acceptance for surgery involving the lower extremities. In the presence of an increased risk of perioperative pulmonary compromise, such as in patients with respiratory impairment or features suggestive of a difficult airway after induction of general anesthesia, spinal or epidural anesthesia might confer some management and outcome advantages. On occasion, there Received: February 21, Revised: March 4, Accepted: April 1, Corresponding author: Woon Seok Roh, M.D., Department of Anesthesiology and Pain Medicine, School of Medicine, Catholic University of Daegu, , Daemyeong 4-dong, Nam-gu, Daegu , Korea. Tel: , Fax: , usno@cu.ac.kr CASE REPORT A 66 year-old female (height 150 cm, weight 84 kg) was scheduled for elective total knee replacement. She had been treated with methyprednisolone and methotrexate for degenerative osteoarthritis and rheumatoid arthritis for 3 years, and with antihypertensive medications including aspirin 100 mg once a day for hypertension for 5 years. One year ago, total knee replacement was canceled due to underlying conditions involving heart and kidney, anemia and other problems in a local private hospital and then she was transferred to our institution for better management of the problems. After appropriate management of the clinical problems, an elective total knee replacement was scheduled. Preoperative laboratory tests showed hemoglobin 8.5 g/dl, total white blood cell count 16,500 cells/mm 3, platelet 270

2 Jong Hae Kim, et al:peripheral nerve block and total knee replacement 271 Fig. 1. Preoperative chest radiograph shows mild pulmonary edema, left pleural effusion and destructive pulmonary tuberculosis in atelectasis involving left upper lobe. Fig. 2. Preoperative lumbar spine anteroposterior radiograph shows osteophytes and no remarkably narrowed interlaminar space in the lower lumbar vertebrae. count 106,000/mm 3 and blood urea nitrogen 37.5 mg/dl, creatinine 2.7 mg/dl, prothrombin time 11.9 seconds, activated partial thromboplatin time 34.4 seconds and bleeding time and clotting time in the normal range. Pancytopenia resulting from disease modifying antirheumatic drugs was resolved following their cessation, but the anemia still persisted. Preoperative vital signs were blood pressure 120/80 mmhg and heart rate 60 beats per minute. Transthoracic echocardiography and coronary angiography were found to be normal with right bundle branch Fig. 3. Preoperative lumbar spine lateral radiograph demonstrates distance from skin to epidural space is approximately 97.8 mm. block in electrocardiogram. However, the pulmonary function test revealed moderate obstructive lung defect with 0.93 liters of forced expiratory volume in one second and decrease in flow rate at peak flow and flow at 50% and 75% of the flow volume curve, and mild pulmonary edema, left pleural effusion and destructive pulmonary tuberculosis in atelectasis involving left upper lobe were visualized on preoperative chest radiograph (Fig. 1). She also had a history of dyspnea on exertion for 3 years. In addition, she came to be diagnosed with chronic renal failure due to hypertensive nephropathy during this admission. Examination of her upper airway revealed that soft palate and uvula were easily visualized and she was assigned to Mallampati class II. Flexion and extension of the cervical spine appeared to be reasonably well preserved. Her lumbar interspinous space could not be palpated due to excess body trunk fat. She complained of intermittent low back pain, but plain radiographs of the lumbar spine showed no particular bony abnormalities except osteophytes (Fig. 2 and 3). After reviewing the risks of the various forms of anesthesia, general anesthesia was planned. Premedication consisted of intramuscular glycopyrrolate 0.1 mg 30 minutes before surgery. Electrocadiogram, pulse oximetry and blood pressure cuff were applied for intraoperative monitoring. Alveolar denitrogenation was performed with the patient breathing 100% oxygen through a nonrebreather mask. Anesthesia was induced with intravenous propofol 80 mg combined with continuous infusion of remifentanil 0.3 μg/kg/min. After achieving unconsciousness, intravenous rocuronium 85 mg was

3 272 Anesth Pain Med Vol. 6, No. 3, 2011 Fig. 4. This photograph shows the obese patient after femoral and sciatic nerve blocks. administered. Suddenly, mask ventilation became impossible and immediate endotracheal intubation was attempted. Laryngoscopy revealed a grade 4 Cormack and Lehane view and another attempt of endotracheal intubation also failed. The consecutive attempts using a light wand, fiberoptic bronchoscope, laryngeal mask airway were in vain. However, saturation of peripheral oxygen (SpO 2) was maintained above 95% with a two-handed technique despite failed intubation and difficult positive pressure ventilation. After discussion of 20 minute-long preoperative episodes with the surgeon, it was decided to cancel the surgery. To reverse neuromuscular blockade, 20 mg of pyridostigmine with 0.4 mg of glycoppyrolate was used intravenously. Recovery of spontaneous respiration and consciousness was not achieved in spite of 15 minutes of additional positive pressure ventilation with a two-hand technique, during which arterial catheterization was instituted for continuous blood pressure monitoring and frequent arterial blood sampling. At this time, the arterial blood gas analysis showed ph 7.14 PaCO 2 70 mmhg, PaO mmhg, and SaO 2 100%. So, an additional dose of reversal agent consisting of 10 mg of pyridostigmine and 0.2 mg of glycopyrrolate was injected intravenously. A subsequent arterial blood gas measurement showed that ventilation had improved, with ph 7.30, PaCO 2 45 mmhg, PaO mmhg and SaO 2 100%. Ten minutes later, massive gastric distention resulting from excessive pressure applied to maintain airway was decompressed via a nasogastric tube. Gradually, she regained normal consciousness and became responsive to verbal command. After taking a portable chest x-ray film during one-hour stay in the recovery room, the patient was moved to the ward and oxygen therapy was continued by Venturi mask. Her respiratory function had completely recovered 2 hours after arriving on the ward. Three days after the event, FSNBs was planned for the total knee replacement. On arrival in the operating room, monitoring of noninvasive blood pressure, electrocardiogram and SpO 2 was instituted. Then, femoral nerve block was performed lateral to the femoral artery immediately below the inguinal ligament. Successful location was indicated by contraction of the quadriceps femoris muscle with an initial current of 1 ma at 1 Hz and continuous contraction at 0.5 ma at 1 Hz using Stimuplex A R 150 mm needle (Braun Medical, Melsungen, Germany). After negative aspiration, 25 ml of 1.5% mepivacaine were injected. The sciatic nerve block was based on Labat s technique. In the lateral decubitus position (Sim s position), the same needle used for the femoral nerve block was inserted at a right angle to all cutaneous planes at the caudal end of 3 5 cm line originating from, and perpendicular to, the middle of a line that intersects the greater trochanter posterior to the iliac spine. The sciatic nerve was identified with the help of a nerve stimulator using a stimulus of 1 ma at 1 Hz, while contractions of the gastrocnemius (foot plantar flexion) indicated proximity to the sciatic nerve and the needle was introduced until muscle twitches were elicited with currents of 0.5 ma at 1 Hz. After negative aspiration, 25 ml of 1.5% mepivacaine were injected. Patients were then returned to a supine position (Fig. 4). Radial artery catheterization and subclavian central venous catheterization were performed for continuous arterial pressure monitoring and central venous pressure monitoring, respectively. The patient felt no pain at the incision site when pinch was applied just before the operation. The operation had been uneventful since and took 150 minutes. After completion of the surgery, there were no postoperative complications, and laboratory data and vital signs were within normal limits. Until the next 2 hours after the surgery, she didn t report the postoperative pain. The patient was discharged home 21 day after the surgery and reported no complications related to the event. DISCUSSION Regional anesthesia in total joint replacement is claimed to decrease the incidence of deep-vein thrombosis and pulmonary embolism and to reduce intraoperative bleeding, the need for transfusion and the length of hospital stay. It can also increase patient satisfaction especially after one-stage bilateral total hip replacement or total knee replacement [3]. Although spinal and epidural anesthesia/analgesia may cause hypotension, motor blockade, urinary retention, pruritus, inadvertent dural puncture

4 Jong Hae Kim, et al:peripheral nerve block and total knee replacement 273 Fig. 5. Preoperative abdominopelvic computerized tomography scan demonstrates distance from skin to epidural space is approximately 95.4 mm. and neurological injury, which may make these techniques less acceptable, epidural anesthesia/analgesia has been shown to improve the post-operative outcomes by relieving pain, reducing pulmonary complications, allowing early mobilization and shortening the length of hospital stay. In this case, we have chosen general anesthesia at first instead of spinal or epidural anesthesia due to long distance from skin to epidural space related to a high body mass index value and nonpalpable lumbar spinous processes. No remarkably narrow interlaminar space in the lower lumbar vertebrae visualized on the preoperative lumbar anteroposterior radiograph (Fig. 2) indicates that rheumatoid arthritis and osteoarthritis minimally affected the lumbar spine and potential technical problems in the performance of neuraxial blockade might not be anticipated. However, it would be expected that the relatively long distance from skin to epidural space (approximately 9.5 cm) in the mid-lumbar area, which was roughly measured in the lateral X-ray film of the lumbar spine (Fig. 3) and abdominopelvic computed tomographic scan (Fig. 5) taken 6 months before the operation, could make neuraxial block difficult. This long distance seems due to a high body mass index value (37.33 kg/m 2 ) according to the result of a previous study that has demonstrated correlations between the depth of epidural space and body mass index [4]. In addition, inability to positively identify spinous process could affect the decision not to perform neuaxial blockade in this patient as de Filho et al. [1] emphasized the quality of patients anatomical landmarks, which was assessed by palpation of the lumbar spinous processes, predicts difficulty of neuaxial block. Because the Mallampati score, most commonly used to assess the likelihood of a difficult laryngoscopy, does not successfully predict the difficulty in about 50% of patients [5], difficult intubation will continue to occur in an unpredictable fashion, like in this case (difficult laryngoscopy in spite of Mallampati score of 2). In the presence of the above factors that affect the safe conduct of neuraxial block and general anesthesia, FSNBs can be an excellent anesthetic option for patients undergoing total knee replacement. The unilateral sympathetic block resulting from FSNBs does not cause significant hemodynamic instability and the potential side effects of prolonged bilateral motor block or urinary retention, which result from neuraxial block. Moreover, FSNBs save time needed for the safe positioning of the conscious patient and no time is required for emergence in the operating room, when compared with general anesthesia. When long-acting agents are used, the block provides initial postoperative analgesia, omitting the need for opioids, which may make patients nauseated, thus limiting its use. These several benefits justify its use as an alternative anesthesia for total knee replacement. The dose of mepivacaine used in this case (8.9 mg/kg), which is more than maximum recommended dose (5 7 mg/kg), may cause systemic toxicity of local anesthetics. And Kaiser et al. [6] reported that the mean maximum venous plasma concentration of mepivacaine was 5.1 μg/ml, which is the threshold for toxic symptoms (5 6 μg/ml), in a pharmacokinetic study of "3-in-1"/sciatic nerve blocks for lower limb surgery using 9.4 mg/kg of mepivacaine on the average. However, the patient has some advantage over the systemic toxicity, because synthesis of the local anesthetic binding protein (alpha 1 acid glycoprotein) in the liver is stimulated in renal failure, offering some protection against systemic toxicity diminishing the free plasma fraction [7]. Actually, there were no signs and symptoms of systemic toxicity in the performance of FSNBs in this case. In a previous study, the time lasting from the end of local anesthetic injection to complete resolution of sensory and motor block in the patients receiving combined sciatic-femoral nerve block with 25 ml of 2% mepivacaine was 206 ± 51 minutes (values are expressed as mean ± standard deviation) [8]. In this case, 900 mg of 1.5% mepivacaine were used and there are no available reports comparable to the complete resolution time (approximately 270 minutes in this case) so far. However, considering an increase in the volume and the

5 274 Anesth Pain Med Vol. 6, No. 3, 2011 concentration of local anesthetics produces a longer duration of sensory block despite its not-linear pattern [9,10], a prolonged period of perioperative analgesia in this case is a consequent result. Several investigators have demonstrated that the femoral nerve block, to result in blockade of the femoral, obturator, and lateral femoral cutaneous nerves, does not consistently produce anesthesia of the obturator nerve [11] and addition of obturator nerve blocks improves postoperative analgesia [12]. However, an additional obturator nerve block could not be performed because the dose of local anesthetic used in FSNBs was already over maximum recommended dose. Fortunately, the quality of surgical anesthesia in this case was enough for the patient to undergo the total knee replacement, presumably due to occasional proximal spread of local anesthetics to the obturator nerve or no cutaneous contribution of the obturator nerve [13]. Recently, introduction of ultrasound imaging techniques to peripheral nerve blocks decreases the dose of local anesthetics required to produce a successful surgical block and time to perform the procedures, and provides improvements in onset and success of sensory block. Nevertheless, nerve stimulation should be an essential part of ultrasound guided technique, as ultrasound alone only had a 60% success rate [14]. Furthermore, ultrasound-aided peripheral nerve stimulated block is perhaps the optimal way to achieve a successful block, especially at the beginning of a learning process [15]. Thus, unavailability of ultrasound at the time of FSNBs implies the limitation of our experience. By decreasing the dose of local anesthetics required for FSNBs under ultrasound guidance, it should have been possible to perform an additional obturator block, which could not be blocked consistently by femoral 3 in 1 block. This case shows that FSNBs offers beneficial alternative anesthesia in a total knee replacement for a patient who has a previous history of unexpected failed endotracheal intubation and factors precluding central neuraxial block. The increase in degenerative diseases deforming spinal anatomy and cardiovascular disease requiring antiplatelet therapy is accompanied by the rapid rise in the elderly population. And the prevalence of obesity is also increasing dramatically in developed countries. Currently, no test is specific or sensitive enough to predict all difficult intubations. These conditions, that prevent the safe conduct of neuraxial block and general anesthesia, result in the need of an alternative anesthetic technique. In conclusion, FSNBs can be one of the good alternatives to neuraxial block and general anesthesia for patients undergoing total knee replacement. REFERENCES 1. de Filho GR, Gomes HP, da Fonseca MH, Hoffman JC, Pederneiras SG, Garcia JH. 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