REGIONAL/LOCAL ANESTHESIA and OBESITY

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1 REGIONAL/LOCAL ANESTHESIA and OBESITY Jay B. Brodsky, MD Stanford University School of Medicine Potential Advantages Regional compared to General Anesthesia Minimal intra-operative airway interventions Less cardiopulmonary depression Improved postoperative pain control Decreased opioid consumption Less postoperative nausea and vomiting (PONV) 1

2 Potential Advantages Regional compared to General Anesthesia Shorter PACU length of stay Shorter hospital length of stay Fewer unplanned hospital admissions Increased overall patient t satisfaction Is Regional Anesthesia Safer than General Anesthesia? Review of 141 trials Overall mortality reduced 1/3 Rodgers et al. Reduction of postoperative mortality and morbidity with epidural and spinal anesthesia: results from overview of randomised trials. BMJ 2006; 321:

3 Neuraxial Anesthesia (Epidural and Spinal) and Obesity Almost all studies are from obstetrical patients Normal term pregnancy mimics anatomic and physiologic changes associated with obesity Obese patients have smaller cerebrospinal fluid (CSF) volume - changes further exaggerated in the obese parturient Intra- abdominal pressure rises with increasing weight Pelosi, et al. Anesthesiology 1999; 91:

4 Hogan et al.magnetic Resonance Imaging of Cerebrospinal Fluid Volume and the Influence of Body Habitus and Abdominal Pressure. Anesthesiology 1996; 84: Decreased CSF volume from increased abdominal pressure - more extensive neuraxial blockade through diminished dilution of anesthetic Mechanism for decreased CSF volume is inward movement of soft tissue in the inter-vertebral foramen displacing CSF 4

5 50 patients t 4 ml 0.5% bupivacaine at L 3-4 McCulloch et al. Influence of obesity on spinal analgesia with isobaric 0.5% bupivacaine. BJA 1986; 58: patients per group 3 ml 0.5% bupivacaine L 3-4 or L 4-5 Taivainen et al. Influence of obesity on the spread of spinal analgesia after injection of plain 0.5% bupivacaine at the L3-4 or L4-5 interspace. BJA 1990; 64:

6 Epidural Higher EPIDURAL block (obstetrical patients) directly proportional to BMI [C-section, 20 ml 0.75% bupivacaine: adequate fo thin parturients (BMI < 28); TOO HIGH for obese patients] Hodgkinson R, Obesity and the cephalad spread of analgesia following epidural administration of bupivacaine for Cesarean section. Anesth Analg :

7 Regional Anesthesia Obesity TECHNICAL PROBLEMS Difficulty moving and positioning the patient Obscured anatomic landmarks Inability to identify epidural or subarachnoid spaces Increased frequency of vascular cannulation and/or wet tap during epidural placement Role of fluoroscopy/ultrasonography 7

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9 Conventional needles may be too short 9

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11 Epidural catheter can pull out > 1 cm Advance > 4 cm into epidural space (concern for multi-orificed epidural catheters) Hamilton et al. Changes in the position of epidural catheters associated with patient. Anesthesiology. 1997; 86:

12 Elevation Pillow 12

13 FRC Decreases with Increasing BMI POSITION Pelosi, et al: Anesth Analg 1998; 87:

14 NORMAL OBESITY Upright Supine FRC decreases at the expense of ERV SUPINE POSITION Increased O2 consumption, Decreased pao2 Increased work of breathing Decreased FRC and compliance Increased cardiac output Increased pulmonary artery pressure Obesity-Supine i Death Syndrome Tseuda et al. Anesth Analg 1979; 58:

15 OBESITY Supine Trendelenburg ALWAYS BE PREPARED FOR GENERAL ANESTHESIA! Increased chance of inadequate or failed block requiring conversion to general anesthesia Tracheal intubation often under less than ideal conditions 15

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18 Can J Anaesth 2004; 51: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Anesthesiology 2005; 102:

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20 Obese patients can be anesthetized in ambulatory setting Davies et al. Obesity and day-case surgery. Anaesthesia 2001; 56:

21 Non-obese Obese BMI < 30 kg/m 2 BMI > 30 kg/m 2. Anesth Analg 2006; 102:

22 Similar success rates between obese (BMI >25 kg/m 2 ) and normal-weight (BMI <25 kg/m 2 ) patients Longer time to identify structures in obese group Schwemmer U, et al. Ultrasound-guided interscalene brachial plexus anesthesia: differences in success between patients of normal and excessive weight. Ultraschall Med 2006; 27:

23 Potential Advantages Regional Anesthesia in Obesity Minimal airway intervention - difficult airway - increased risk of pulmonary aspiration (?) Minimal cardiopulmonary depression - high incidence of cardiopulmonary problems Potential Advantages Regional Anesthesia in Obesity Decreased opioid requirements - increased sensitivity to opioids and sedatives (Obstructive Sleep Apnea) Decreased PONV Shorter PACU /hospital stays 23

24 What are the risks/benefits of regional anesthesia in the obese patient?????????????????? What are the appropriate doses of local anesthetic in obesity? neuraxial block (spinal/epidural) peripheral block??????????????????? Regional Anesthetic Management of the Obese Patient Select a regional anesthesia technique when possible Anticipate problems; prepare with appropriate equipment, monitors and personnel If general anesthesia becomes necessary - tracheal intubation and controlled ventilation Postoperatively - close monitoring and early mobilization Judicious use of opioids 24

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