Bariatric Times - January 2009 - (Page 26)

Anesthesiology Perspective Bariatric Times • January 2009 TABLE 1. Potential advantages of regional anesthesia in obesity • Minimal intraoperative airway interventions • Less cardiopulmonary depression • Improved postoperative pain control with decreased opioid consumption • Shorter PACU length of stay • Shorter hospital length of stay • Fewer unplanned hospital admissions due to pain, drowsiness, and nausea/vomiting • Increased overall patient satisfaction TABLE 2. Regional anesthetic considerations for morbid obesity • Difficulty in moving and positioning the patient • Increased technical difficulty in performing a regional block: ⇒ Obscured anatomic landmarks ⇒ Inability to identify the epidural or subarachnoid space ⇒ May require ultrasonography • Routine needle may be too short in relation to the excessively deep anatomical structures • Possibility of inadequate or failed block, requiring conversion to general anesthesia TABLE 3. Principles in the anesthetic management of the obese patient • Select a regional anesthesia technique when possible • Anticipate problems and effectively prepare with appropriate equipment, monitoring, and personnel • If general anesthesia is required, chose tracheal intubation and controlled ventilation • Postoperative care should include close monitoring and early mobilization • Judicious use of any opioid by any route obese patient to identify relevant landmarks, to approximate the distance to the intrathecal space, and to confirm proper position of the spinal needle as it was advanced.20 Reports of complications of spinal anesthesia in obese patients are once again limited to just a few case reports or small clinical series. For example, transient neurologic symptoms, described as leg or buttock pain, occurred more often in obese (BMI>30kg/m2) than normal weight patients following spinal anesthesia with lidocaine.21 As little information as we have on neuraxial blocks in obesity, there is even less data on peripheral nerve blocks in this population. A single large study considered 9,342 peripheral nerve blocks in 7,160 patients undergoing ambulatory surgery. Patients were placed into four groups depending on their BMI ( 35kg/m2). For risk adjustment, the authors categorized regional anesthetic procedures into the following four subsets to combine blocks with similar characteristics: 1) centro-neuraxial blocks; 2) peripheral nerve blocks; 3) continuous peripheral nerve blocks; and 4) paravertebral blocks. All peripheral nerve blocks were performed using a nerve stimulator technique. This study found that high BMI represented an independent risk factor for block failure.22 In a subsequent publication by the same group consisting of an almost identical database, the block failure in the different BMI categories was as follows: BMI 30kg/m2=12.7%.23 The riskadjusted block failure rate for peripheral nerve blocks was statistically significantly higher in obese patients but not in overweight patients. Pain with movement was significantly less in obese and overweight patients. Whether these results are related to increased pain tolerance, higher prevalence of diabetic neuropathy, or less extensive surgery in this subset of patients is unknown. A high level of overall satisfaction in the obese group clearly demonstrated that regional anesthesia techniques were well accepted among patients with increased BMI. A conclusion of this study was that overweight and obese patients should not be excluded from undergoing regional anesthesia in the ambulatory setting. In the only other relevant study, Franco et al24 investigated the impact of BMI on the success rate of supraclavicular block. Their success rate was 94.3 percent in obese patients, but this was significantly less than in their non-obese population. Once again, the use of US can make an invaluable contribution in performing successful peripheral nerve blocks in obese patients.25-26 CONCLUSION An extensive review of the medical literature reveals a paucity of studies of regional anesthesia and obesity. Although we can make some general recommendations for regional anesthesia in obese patients (Table 3), with so few studies addressing this topic these recommendations are based on the authors’ biases. We urge anesthesiologists and surgeons who routinely manage obese patients with regional anesthetic techniques to share their experiences with others. 15. 16. 17. 18. 19. 20. 21. 22. REFERENCES 1. 2. Vallejo MC. Anesthetic management of the morbidly obese parturient. Curr Opin Anaesthesiol. 2007; 20:175–180. Soens MA, Birnbach DJ, Ranasinghe JS, et al. Obstetric anesthesia for the obese and morbidly obese patient: an ounce of prevention is worth more than a pound of treatment. Acta Anaesthesiol Scand. 2008;52:6–19. Hodgkinson R, Husain FJ. Obesity and the cephalad spread of analgesia following epidural administration of bupivacaine for Cesarean section. Anesth Analg. 1980;59:89–92. Panni MK, Columb MO. Obese parturients have lower epidural local anaesthetic requirements for analgesia in labour. Br J Anaesth. 2006;96:106–110. Perlow JH, Morgan MA. Massive maternal obesity and perioperative cesarean morbidity. Am J Obstet Gynecol. 1994; 170:560–565. Hood DD, Dewan DM. Anesthetic and obstetric outcome in morbidly obese parturients. Anesthesiology. 1993;79:1210–1218. Ray A, Hildreth A, Esen UI. Morbid obesity and intrapartum care. J Obstet Gynecol. 2008;28:301–304. Adachi YU, Sanjo Y, Sato S. The epidural space is deeper in elderly and obese patients in the Japanese population. Acta Anaesthesiol Scand. 2007;51:731–735. Hamilton CL, Riley ET, Cohen SE. Changes in the position of epidural catheters associated with patient movement. Anesthesiology. 1997;86:778–784. Ranta P, Jouppila P, Spalding M, et al. The effects of maternal obesity on labour and labour pain. Anaesthesia. 1995;50:322–632. Faure E, Moreno R, Thisted R. Incidence of postdural puncture headache in morbidly obese parturients. Reg Anesth. 1994;19:361–363. Wallace DH, Currie JM, Gilstrap LC, et al. Indirect sonographic guidance for epidural anesthesia in obese pregnant patients. Reg Anesth. 1992;17:233–236. Santos A, Pedersen H, Finster M, et al. Hyperbaric bupivacaine for spinal anesthesia in cesarean section. Anesth Analg. 1984;63:1009–1013. Pitkanen MT. Body mass and spread of spinal anesthesia 23. 24. 3. 25. 4. 26. 5. with bupivacaine. Anesth Analg. 1987;66:127–131. Taivainen T, Tuominen M, Rosenberg PH. Influence of obesity on the spread of spinal analgesia after injection of plain 0.5% bupivacaine at the L3–4 and the L4–5 interspace. Br J Anesth. 1990;64:542–546. McCulloch WJ, Littlewoord DG. Influence of obesity on spinal analgesia with isobaric 0.5% bupivacaine. Br J Anaesth. 1986;58:610–614. Hogan QH, Prost R, Kulier A, et al. Magnetic resonance imaging of cerebrospinal fluid volume and the influence of body habitus and abdominal pressure. Anesthesiology. 1996;84:1341–1349. Michaloudis D, Fraidakis O, Petrou A, et al. Continuous spinal anesthesia/analgesia for perioperative management of morbidly obese patients undergoing laparotomy for gastroplastic surgery. Obes Surg. 2000;10:220–229. Prasad GA, Perlas A, Jinn K, et al. Ultrasound assisted spinal anesthesia in morbidly obese patients. Anesthesiol. 2008;109:A339. Eidelman A, Shulman MS, Novak GM. Fluoroscopic imaging for technically difficult spinal anesthesia. J Clin Anesth. 2005;17:69–71. Freedman JM, Li D-K, Drasner K, et al. Transient neurologic symptoms after spinal anesthesia: an epidemiologic study of 1,863 patients. Anesthesiology. 1998;89:633–641. Cotter JT, Nielsen KC, Guller U, et al. Increased body mass index and ASA physical status IV are risk factors for block failure in ambulatory surgery—an analysis of 9,342 blocks. Can J Anaesth. 2004;51:810–816. Nielsen KC, Guller U, Steele SM, et al. Influence of obesity on surgical regional anesthesia in the ambulatory setting: An analysis of 9,038 blocks. Anesthesiology. 2005;102:181–187. Franco CD, Gloss FJ, Voronov G, et al. Supraclavicular block in the obese population: an analysis of 2020 blocks. Anesth Analg. 2006;102:1252–1254. Chantzi C, Saranteas T, Zogogiannis J, et al. Ultrasound examination of the sciatic nerve at the anterior thigh in obese patients. Acta Anaesthesiol Scand. 2007;51:132. Duggan E, Brull R, Lai J, et al. Ultrasound-guided brachial plexus block in a patient with multiple glomangiomatosis. Reg Anesth Pain Med. 2008; 33:70–73. 6. AUTHOR CORRESPONDENCE Jay B. Brodsky, MD, Department of Anesthesia, Stanford University Medical Center, Stanford, CA, 94305; Phone: 650-723-6411; Fax: 650-725-8544; E-mail: jbrodsky@stanford.edu 7. 8. 9. 10. 11. 12. 13. 14.

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Bariatric Times - January 2009

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