Guidelines Affecting Our Practice

From the 62nd Postgraduate Assembly in Anesthesiology, sponsored by the New York State Society of Anesthesiologists

Educational Objectives

The purpose of this program is to improve familiarity with the latest guidelines about preoperative fasting and re­gional anesthesia. After hearing and assimilating this program, the clinician will be better able to:

1.   Explain the rationale for the American Society of Anesthesiologists recommendations on fasting before sur­gery.

2.   Discuss the benefits of allowing clear liquids a few hours before surgery.

3.   Identify the factors that can increase risk for bleeding in patients on anticoagulant therapy and the indications for delaying surgery.

4.   Utilize American Society of Regional Anesthesia and Pain Medicine guidelines for performing neuraxial blockade or spinal, epidural, or perineural anesthesia in a patient with a systemic infection.

5.   Recognize risk factors for perioperative neurologic injury and explain how these risks can be minimized.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any per­sonal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and the planning committee reported nothing to disclose. Dr. Hebl presented information related to investigational or off-la­bel use of a therapy, product, or device.

Acknowledgements

This program was recorded at 62nd Postgraduate Assembly in Anesthesiology, held December 12-16, 2008, in New York, NY, and sponsored by the New York State Society of Anesthesiologists. The Audio-Digest Foundation thanks the speakers and the New York State Society of Anesthesiologists for their cooperation in the production of this program.

Guidelines for Fasting

Mark A. Warner, MD, Professor of Anesthesiology, Mayo Clinic College of Medicine, and Dean, Mayo School of Graduate Medical Education, Rochester, MN

Minimum time to surgery after consumption: 2 hr  —  clear liquids; 4 hr  —  breast milk; 6 hr  —  light carbohydrate meal; >8 hr  —  heavy protein foods (eg, cow’s milk or hamburgers); infant formula can be consumed within 4 to 6 hr, depending on protein content (American Society of Anesthesiologists [ASA] guidelines recommend 6 hr)

Importance of fasting: most cases of perioperative pulmonary aspiration not associated with lack of fasting; almost always related to clinician’s airway management skills (or lack thereof), or presence of bowel obstruction, ileus, or material in stomach (eg, blood from bleeding tonsil)

Requirements for aspiration: gastric contents capable of causing lung damage; low pH (acid may damage lungs); intragastric pressure must be capable of overcoming lower esophageal sphincter pressure; large volume of mate­rial regurgitated; material must be able to pass larynx

Perioperative pulmonary aspiration: rare; incidence similar in children >1 yr of age and adults (risk higher in chil­dren aged <6 to 12 mo [cricoid pressure more difficult to apply, and airway manipulation less successful]; young children often not completely paralyzed, so gagging reflex remains when laryngoscope introduced); oc­curs primarily during induction and laryngoscopy; of patients who aspirate, »1 in 25 experience severe se­quelae; aspirating patient has 4% chance of prolonged sequelae, severe injury, or death; according to 1986 study, aspiration risk highest among young children, elderly, and sick patients; “the routine healthy patient rarely aspirates”; in study conducted by speaker and colleagues, aspiration most likely during airway manipu­lation at start or finish of case (laryngoscopy or extubation; in this study, risk higher during extubation; patients often still partially paralyzed (without full laryngeal function); clinicians may not be paying as close attention as at start of case); pediatric patients  —rarely die of perioperative pulmonary aspiration; chronic aspiration more lethal

Fasting and perioperative pulmonary aspiration: no correlating data; stomach empties »90% of clear liquids within 1 hr of consumption; warm liquids empty faster; solid material added to liquid slows emptying (eg, or­ange juice with pulp); breast milk empties faster than cow’s milk; clear liquids flush stomach contents past py­lorus; also dilute acid and raise pH of stomach contents; speaker recommends encouraging patients to drink clear liquids up to 1 hr before surgery

Recommendations for children: formula, breast milk, or clear liquid acceptable before procedure; maintains blood glucose; patient less hungry, better-behaved, and more comfortable

Recommendations for adults: patients accustomed to drinking caffeinated drinks in morning feel better if coffee permitted; may prevent perioperative headache, nausea, and general irritability; nondairy creamer and sugar or sweetener permissible, but cow’s milk should be avoided

Guidelines for solids: large volumes slow stomach emptying; the more carbohydrate or protein present, the longer the empyting time; light carbohydrate meals (eg, toast and jelly) empty quickly and leave little residual volume at 4 hr; avoid dairy, other heavy protein, or fatty meal; clear liquids empty quickly, even if patient has gastroesoph­ageal reflux disease (GERD); solids may take longer than in patients without GERD

Diabetes: few studies in children; gastroparesis infrequent complication of diabetes in adults; usually seen in indi­viduals with longstanding, poorly controlled insulin-dependent diabetes; delays gastric emptying of liquids and solids; assume diabetic taking any insulin product has delayed emptying

Obesity: in adults, associated with slightly slower gastric emptying of liquids

Smoking: relaxes gastroesophageal sphincter for »10 min

Chewing gum and candy: gum modestly increases gastric volume; swallowed saliva has pH of 7 (beneficial; raises gastric pH); acceptable as long as patient remembers to remove it before procedure; hard candy riskier because often chewed (may introduce solid material into stomach and increase risk for aspiration)

Conclusions: adherence to guidelines vary with institution; helpful for making decisions about whether to delay ur­gent or emergency procedure; aspiration rare; unclear whether fasting really reduces risk; some patients might ben­efit from clear liquids and/or caffeine-containing beverages

Guidelines for Regional Anesthesia

James R. Hebl, MD, Associate Professor of Anesthesiology, Mayo Clinic College of Medicine, Rochester, MN

Recommendations from consensus panels convened by American Society of Regional Anesthesia and Pain Medicine (ASRA): disclaimers  —  based on best evidence currently available (may be sparse); few studies have sufficient power to allow definitive recommendations on catastrophic but rare events; advisories cannot guaran­tee specific outcome; subject to revision based on evolving clinical practice and data; variations that deviate from recommendations considered “entirely acceptable”, based on expert opinion and clinical judgment

Anticoagulation and neuraxial anesthesia: hemorrhagic complications described for single injection and continuous catheterization techniques, including upper and lower extremity peripheral blocks, as well as neuraxial tech­niques; addition of anticoagulation dramatically increases risk for major bleeding (ie, intracranial, intraspinal, ocular, mediastinal, retroperitoneal) requiring hospitalization or transfusion, and resulting in mortality)

Risk factors for bleeding: intensity or degree of anticoagulant effect; increasing age; female sex; previous history of gastrointestinal bleeding; concomitant aspirin therapy; duration of anticoagulation; international normalized ratio (INR) >4; patients treated with warfarin or heparin and with therapeutic INR of 2 to 3 have slightly <3% risk of bleeding over 3 mo of treatment; risk doubles if INR consistently >4; risk for bleeding associated with thrombolytic therapy approaches 30% in some studies; conclusion  —  prevention of thrombosis does carry some risk

2003 ASRA recommendations for using low-molecular-weight heparin with neuraxial anesthesia: low-dose (prophylaxis)  —  neuraxial needle placement should occur ³10 to 12 hr after prophylactic dose; high-dose (therapeutic or bridging) therapy  —  delay needle placement 24 hr after last dose; twice-daily postoperative dosing  —  no indwelling neuraxial catheters; administer first dose 24 hr after surgery; if catheter in place, re­move it and administer first dose 2 hr later; single-dose regimen  —  indwelling catheters acceptable (with cau­tion); first dose should be given 6 to 8 hr postoperatively and next dose l 24 hr later; if catheter in place, remove 10 to 12 hr after last dose and 2 hr before next dose; caveat  —  if blood encountered during needle or catheter placement, or if heme aspirated through catheter, urge surgeon to delay initiation of low-molecular-weight heparin therapy for 24 hr after neuraxial technique

Standard heparin: subcutaneous  —  no contraindications for neuraxial technique; if technically difficult block an­ticipated, recommendations suggest delaying administration until after block (eg, obese patient or patient with severe degenerative spinal disease); if patient has been receiving subcutaneous heparin >4 days, perform plate­let count to rule out thrombocytopenia; intravenous  —  delay administration until 1 hr after neuraxial tech­nique; remove catheter 2 to 4 hr after last dose, and resume administration 1 hr later; not mandatory to delay case if blood encountered during needle placement

Antiplatelet medications: nonsteroidal anti-inflammatory drugs not contraindicated; discontinue ticlopidine (Ti­clid) 14 days in advance, clopidogrel (Plavix) 7 days in advance, and glycoprotein IIb/IIIa inhibitors 8 to 48 hr in advance; warfarin (eg, Coumadin)  —  preoperative as well as postoperative doses deserve attention; for pa­tients discontinuing warfarin, ASRA recommends that patients have normal INR (1.0-1.1) before neuraxial placement; when patient begins warfarin, in situ catheter should be removed when INR <1.5; before neuraxial placement, check INR if patient has received preoperative warfarin >24 hr before or multiple preoperative war­farin doses

2004 ASRA practice advisory on infectious complications: neuraxial blockade  —  generally not recommended for patients with evidence of ongoing, untreated systemic infection, although decision should be tailored to specific case; patients with systemic infections may safely undergo spinal anesthesia if they have responded to antibiotics administered before neuraxial block; insufficient evidence for making recommendations regarding epidural anes­thesia for infected patients; perineural catheters  —  risk factors for infection include catheter placement in pa­tients subsequently admitted to intensive care unit or with traumatic injury (probably related to immune compromise); catheter use >48 hr; no antibiotic prophylaxis; male sex; other possible factors include anatomic region, method of catheter placement, type of antiseptic used, and whether tunneling or nontunneling catheter used; catheter colonization common, but true clinical signs and symptoms of infection much less common

2008 ASRA advisory on neurologic complications associated with regional anesthesia: in analysis of 32 studies, aggregate risk for neurologic complications 1:2500 (0.04%); risk highest for radiculopathy and neuropathy af­ter spinal or epidural anesthesia; after peripheral techniques, aggregate risk for neuropathy »3%, ranging from severe injuries to transient effects that resolved within 24 hr; brachial plexus blockade associated with highest risk

Neurologic injuries associated with peripheral blockade reported in ASA Closed Claims Database: 40% occurred after axillary blockade, 40% after interscalene blockade, 19% after intravenous regional anesthetics, 8% after superclavicular, and 2% after ankle administration; slightly >50% produced temporary nerve injury and >1 in 3 resulted in severe permanent injury, with 8% contributing to death (usually from cardiac collapse after intra­vascular injection of local anesthetics); mechanism of injury specifically block-related and attributed to anes­thesia provider in >50% of cases; in 20% of claims, anesthesia provider judged to have delivered substandard care; severe and permanent damage most often associated with brachial plexus blockade

Risk factors for perioperative nerve injury: patient factors  —  preexisting neurologic deficits; male sex; increasing age; extremes of body habitus; preoperative valgus deformity >10^o or knee contracture >15º for patients under­going lower-extremity surgery; surgical factors  —  intraoperative trauma; prolonged tourniquet inflation times; vascular compromise; inflammation; edema; abscess or hematoma compressing adjacent neural structures; tightly applied cast; patient positioning; anesthetic risk factors  —  direct needle or catheter-induced mechanical trauma; intrafascicular injection; chemical injury, including direct local anesthetic neurotoxicity; ischemic in­jury; injury usually results from several risk factors; double-crush phenomenon  —  patients with preexisting deficit or initial insult may be more susceptible to neurologic insults at remote or distant site along nerve; dam­age exceeds additive effect of individual insults

ASRA guidelines on nerve injury: no human or animal data to support benefit of any specific nerve localization technique; give serious consideration to neurology consultation for any postoperative nerve injury; perform early electromyographic assessment; when planning regional anesthetic for patient with preexisting neurologic com­promise, modify technique (eg, reduce dose of local anesthetic, eliminate or reduce additives such as epineph­rine); no data to suggest that regional anesthesia safe for heavily sedated or anesthetized patients; “overwhelming” evidence against administering interscalene blockade to heavily sedated or anesthetized pa­tients; however, these techniques may be appropriate for pediatric patients or those with dementia or develop­mental delays

Suggested Reading

Bernards CM et al: Regional anesthesia in anesthetized or heavily sedated patients. Reg Anesth Pain Med 33:459, 2008; Bopp C et al: A liberal preoperative fasting regimen improves patient comfort and satisfaction with anesthesia care in day-stay minor surgery. Minerva Anestiesiol Feb 4, 2009 [Epub ahead of print]; Heit JA: Perioperative man­agement of the chronically anticoagulated patient. J Thromb Thrombolysis 12:81, 2001; Hogan QH: Pathophysiol­ogy of peripheral nerve injury during regional anesthesia. Reg Anesth Pain Med 33:435, 2008; Horlocker TT et al: Regional anesthesia in the anticoagulated patient: defining the risks (the second ASRA Consensus Conference on Neuraxial Anesthesia and Anticoagulation). Reg Anesth Pain Med 28:172, 2003; Neal JM et al: ASRA Practice Ad­visory on Neurologic Complications in Regional Anesthesia and Pain Medicine. Reg Anesth Pain Med 33:404, 2008; No author cited: Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American So­ciety of Anesthesiologist Task Force on Preoperative Fasting. Anesthesiology 90:896, 1999; Olsson GL et al: Aspira­tion during anaesthesia: a computer-aided study of 185,358 anaesthetics. Acta Anaesthesiol Scand 30:84, 1986; Soreneson EJ: Neurological injuries associated with regional anesthesia. Reg Anesth Pain Med 33:442, 2008; Stuart PC: The evidence base behind modern fasting guidelines. Best Pract Res Clin Anaesthesiol 20:457, 2006; Warner MA et al: Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology 78:56, 1993; Warner MA: Is pulmonary aspiration still an important problem in anesthesia? Curr Opin Anesthesiol 13:215, 2000.