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REGIONAL/LOCAL ANESTHESIA and

Jay B. Brodsky, MD

ANESTHESIA and OBESITY

y y,Stanford University School

of MedicineJbrodsky@stanford.edu

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)

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Potential Advantages Regional compared to General Anesthesia

Shorter PACU length of stay

Shorter hospital length of stay

Fewer unplanned hospital admissions

I d ll ti t ti f tiIncreased overall patient satisfaction

Review of 141 trials –

Is Regional Anesthesia Safer than General Anesthesia?

Overall mortality reduced

Rodgers et al. Reduction of postoperative mortality and morbidity with epidural and spinal anesthesia: results from overview of randomised trials. BMJ 2006; 321: 1-12

1/3

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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-abdominalabdominal pressure rises with increasing weight

Pelosi, et al. Anesthesiology 1999; 91: 1221-31

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Hogan et al.Magnetic Resonance Imaging of Cerebrospinal Fluid Volume and the Influence of Body Habitus and Abdominal Pressure. Anesthesiology 1996; 84: 1341-9

D d CSF l f i d bd i l 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

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50 ti t 50 patients – 4 ml 0.5% bupivacaine at L3-4

McCulloch et al. Influence of obesity on spinal analgesia with isobaric 0.5% bupivacaine. BJA 1986; 58: 610-4

40 patients per group – 3 ml

0.5% bupivacaine pL3-4 or L4-5

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:

542-6

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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. 1980 59:89-92

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Regional Anesthesia – ObesityTECHNICAL 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

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Conventional needles may be too short

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Epidural catheter can pull out > 1 cm Ad 4 i t id l

Hamilton et al. Changes in the position of epidural catheters associated with patient. Anesthesiology. 1997; 86:778-84.

Advance > 4 cm into epidural space(concern for multi-orificed epidural catheters)

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Elevation Pillow

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FRC Decreases with Increasing BMI

Pelosi, et al: Anesth Analg 1998; 87: 654-60

POSITION

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Upright Supine

NORMAL OBESITY

FRC decreases at the expense of ERV

SUPINE POSITION• Increased O2 consumption, Decreased paO2

• Increased work of breathing• Increased work of breathing

• Decreased FRC and compliance

• Increased cardiac output

• Increased pulmonary artery pressure

“Ob it S i D th S d ”“Obesity-Supine Death Syndrome”

Tseuda et al. Anesth Analg 1979; 58: 345-7

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Supine

OBESITY

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

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Can J Anaesth 2004; 51: 810-16xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Anesthesiology 2005; 102: 181-187Anesthesiology 2005; 102: 181 187

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Obese patients can be anesthetized in ambulatory setting

Davies et al. Obesity and day-case surgery. Anaesthesia 2001; 56: 1090-115

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Non-obese ObeseBMI < 30 kg/m2 BMI > 30 kg/m2

. Anesth Analg 2006; 102: 1252-4

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Schwemmer U, et al. Ultrasound-guided interscalene brachial plexus anesthesia: differences in success between patients of normal and excessive weight. Ultraschall

Med 2006; 27: 245-50

Similar “success” rates between obese (BMI >25 kg/m2) and normal-weight (BMI <25 kg/m2) patients

Longer time to identify structures in obese group

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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 PONVDecreased PONV

Shorter PACU /hospital stays

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What are the risks/benefits of regional anesthesia in the obese patient?

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What are the appropriate doses of local anesthetic in obesity?

neuraxial block (spinal/epidural)neuraxial block (spinal/epidural)

peripheral block

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Regional Anesthetic Management of the Obese Patient

Select a regional anesthesia technique when possiblep

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

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The End