Identify risk factors that predispose to postoperative pulmonary complications.

Discuss prevention and treatment of these complications.

Summarize the most common serious complications of regional anesthesia.

Recognize factors that modify the incidence of these complications.

Review the management of complications associated with regional anesthesia.

Postoperative Pulmonary Complications
Mark Nunnally, MD, Assistant Professor, Department of Anesthesia and Critical Care, University of Chicago, Pritzker School of Medicine, Chicago, IL

Introduction: respiratory dysfunction strongly correlated with serious illness; respiratory function worsens for 1 to 2 days after initial surgical insult, then improves after ≈1 wk; incision site best predictor of pulmonary complications; pulmonary function tests (PFTs) do not accurately indicate future complications, except perhaps with lung resection surgery; neuraxial anesthesia not curative; microaspiration treatable problem; neuromuscular blockade, reversal, or antagonism useful; aggressive extubation, regardless of course of pulmonary complications, necessary in many cases; positive end-expiratory pressure (PEEP) and continuous positive airway pressure (CPAP) beneficial

Incidence: literature confusing; reported incidence from 0.2% to 40.0% (depends on definition of complication)

Risk for mortality: in general surgery population, serious complication (eg, reintubation, ventilatory failure, pneumonia) increases risk 10-fold; resource utilization increased and length-of-stay extended considerably; patients with respiratory failure sicker than most; mortality from serious pulmonary complication equivalent to that of perioperative myocardial infarction (MI); importance of length of stay and use of resources far greater than for MI

Complications: historically, goal to have patient survive surgery and eliminate need for mechanical ventilation; currently, able to identify atelectasis, pneumonia, and lobar collapse on chest x-ray; studies have different definitions for pulmonary complications; diagnosis of pneumonia unclear; low-grade end points include fever, atelectasis, and spirometry; factors associated with cost include length of stay, specialty use, and resource allocation; more quantifiable measures include death, reintubation, ventilator dependence, and perhaps, pneumonia

Predictors: length of surgery—sicker patients have longer procedures; possible mechanisms include dose-dependent depression of immune function from exposure to various anesthetic agents and tissue trauma; microaspiration—passage of small amounts of pharyngeal secretions around inflated endotracheal tube cuff; may be single greatest arena in which anesthesia provider can influence pulmonary complications; chronic obstructive pulmonary disease (COPD)—diagnosis does not have to lead to significantly increased risk, if patient appropriately optimized; smoking—risk increases substantially at 20-pack years; age—lungs less effective with increasing age; physiologic shunt increases; comorbidities likely greatest factor increasing risk for pulmonary complications; obesity—pulmonary complications not seen in all obese patients, but tend to be severe when they do occur; contributing factors include obstructive sleep apnea (OSA) and severe restrictive disease; avoid attempts to “normalize CO2 ” in patient who has retained CO2 and may have PaCO2 of 55 to 60 mm Hg; location of incision—best predictor of pulmonary complications; greater the proximity to diaphragm, greater the likelihood for complications; upper abdominal incision likely greatest risk; complications with neurosurgery may relate to risk for aspiration; additional risk factors —infection; aspiration; preoperative hospital stay; poor functional status

Testing to predict postoperative pulmonary complications: PFTs useful for stratifying patients for lung resection but not for nonthoracic surgery; newer literature argues PFTs of little, if any, benefit; preoperative blood gas measurement may be useful, but more practical to preoperatively measure oxygenation in room air; determine hypoventilation with blood chemistry panel

Pattern of pulmonary complications: increasing restrictive lung disease manifests as decreased lung volumes (eg, functional residual capacity [FRC], vital capacity, tidal volumes) and increased shunt fraction; possible causes diaphragmatic inhibition, partial splinting due to incisional pain, and systemic factors; patient with severe tissue trauma develops capillary leak leading to increased edema; older model suggests splinting, pain, and diaphragmatic dysfunction lead to reduced lung volumes and pulmonary complications; newer mechanisms include neural reflexes, microaspiration, diminished immunity, and edema

Preventing and treating pulmonary complications

Preoperatively: optimizing patient—for COPD, optimize medications, eg, anticholinergics, bronchodilators, inhaled steroids; short course of antibiotics may be worthwhile in chronic airway infection; for asthmatics, inhaled steroids and β- agonists; little role for preoperative respiratory therapy; nutrition important, but aggressive nutritional therapy in hospital makes little or no sense; maximal benefit from smoking cessation requires 8 wk; however, shorter duration of abstinence also has some benefits, including improved wound healing and reduced carbon monoxide levels

Intraoperatively: neuraxial techniques—effective when placed correctly; epidurals provide superior analgesia and may decrease risk for deep venous thrombosis (DVT); provide better pain control but not panacea once thought to be; laparoscopy and minimally invasive surgery—for abdominal surgery, probably helpful in preventing pulmonary complications, but literature conflicting; role in preventing pulmonary complications as likely related to degree of tissue injury as to incisional factors; however, laparoscopic cholecystectomy makes more sense than open procedure; preoxygenation with positive airway pressure—in obese patient, maintains lung volume, increases O2 capacity, and staves off hypoxemia; predictable loss of “lung units” after induction (dependent atelectasis) attenuated significantly in presence of positive airway pressure; provide CPAP with tight-fitting mask; adjust pressure release valve to 5 cm H2 O; alternatively, when using ventilator equipped with PEEP and pressure support, start with 0 cm H2 O or little pressure support and modest level of PEEP (5 cm H2 O while patient awake; 10 cm H2 O while anesthetized and intubated); other suggestions include keeping head slightly elevated to improve respiratory mechanics and extubating off PEEP

Postoperatively: incentive spirometry; pharyngeal swallowing apparatus, respiratory cough mechanisms, and glottic protecting mechanism exquisitely sensitive to nondepolarizing neuromuscular blockers; train-of-four ratio of ≈0.9 necessary to feel confident that pharyngeal mechanism functions adequately; downside of neostigmine relatively low, compared to benefits; if respiratory complications seen in postanesthesia care unit (PACU), consider inadequate neuromuscular blockade; postoperative lung expansion; selective postoperative nasogastric decompression (related to aspiration); short-acting neuromuscular blockade; data do not support routine total parenteral nutrition (TPN), aggressive enteric nutrition, or pulmonary artery (PA) catheters; early extubation advantageous to avoid colonization or long-term infectious complications and because patient better at managing lung volume and respiratory function; also, anesthesia provider expert at reintubation, if necessary; noninvasive positive pressure ventilation can be used if ventilation worsens after extubation

Complications of Regional Anesthesia
John E. Tetzlaff, MD, Professor of Anesthesiology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, and Vice Chair for Education and Program Director, Anesthesiology Institute, Cleveland Clinic, Cleveland, OH

Pain with block placement: personal or family experience of adverse outcome with regional anesthesia among most common reasons for refusing subsequent regional anesthesia; pain number one adverse experience; informed consent involves reality-based discussion; peripheral block should be performed with minimal infiltration of superficial structures, since infiltration of skeletal muscle can create rhabdomyolysis; analgesics also an option, although even with ultrasonography (US), not safe in patient with slow responsiveness; with preexisting back pain, honest informed consent relevant; all patients have some awareness of instrumentation of lower spine and may have brief exacerbation of back pain; pain after block

Block failure: timing of recognition may be smaller issue because sedative options (eg, propofol, dexmedetomidine) so powerful that patient capable of tolerating significant discomfort; before surgery begins, responsibility of person performing block to verify whether patient will have surgical anesthesia; may require cooperation of surgeon; recognizing partial block also relevant (supplemental blocks may be required); even if block best possible, it may still fail due to discomfort; propofol has revolutionized regional anesthesia; when mixed with short-acting opioids, even if regional anesthesia fails, overall situation only incomplete failure; failure may also be related to technique (choose technique with higher success rate when need for regional anesthesia critical, ie, difficult or unstable airway)

Selection of local anesthetic: local anesthetics behave differently in tissue, particularly highly lipophilic local anesthetics, eg, bupivacaine, ropivacaine, levobupivacaine, etidocaine (not available in United States); needle must be close to neural structure; if using mepivacaine, lidocaine, or chloroprocaine, particularly in association with gentle massage of tissues, movement some distance from injection site common; error in needle placement better overcome with certain local anes- thetics

Allergy to local anesthetics: very few cases of true allergies to local anesthetics; more common in ester family (due to para-aminobenzoic acid); few cases in literature of allergy to amide local anesthetics; probability of cross-reactivity between amide and ester local anesthetics low; allergy related to lidocaine from multidose vials almost nonexistent (because use of multidose vials declining); fewer allergies to methylparaben preservative; other preservatives have created other problems in local anesthetic use, including metabisulfite and ethylenediaminetetraacetic acid (EDTA); in unmonitored setting, when epinephrine mixed with local anesthetics, adrenergic effect of intravascular dose of epinephrine can create feelings that could be attributed to allergy; so-called “dental allergy” not true allergy; allergic label not easily removed from patient, even with allergy testing

Infectious complications: fulminant sepsis—contraindication to block; local infection at block site—skin puncture site should be relatively free of infectious process; superficial abscess—incidence ≈1 in 10000 peripheral nerve blocks in routine patients, assuming reasonable sterile technique; epidural abscess—incidence in routine healthy patient should be significantly lower; however, occurs some time after block placement and removal; after neuraxial block, presence of new neurologic deficit indicates possible infectious or vascular complication; magnetic resonance imaging (MRI) used to rule out epidural abscess; presence of compressive abscess should be identified as quickly as possible; intervention within 6 to 12 hr greatly improves probability of partial or full return of function; aseptic meningitis—risk in spinal anesthesia unfounded; instead, contaminant found in local anesthetic solutions (eg, phenol) caused problems in subarachnoid or epidural space; bacterial meningitis—incidence related to single-shot neuraxial block extremely infrequent; even catheterization for limited time (3-4 days) increases risk only slightly, although recent data on catheter removal show tip of catheter contaminated by bacteria (but may occur upon removal); long-term catheters—immunocompromised patient may have higher infection rate (infection rate in those with full immune suppression may be as high as 3.5%-5.0% if catheter in place >21 days)

Seizure activity: variables—choice of agent (amide local anesthetics more likely to cause seizure than ester drugs); total dose; route of administration (be more cautious in intercostal, caudal epidural, and lumbar epidural spaces); vasoconstrictors (even though they may not prolong duration, definitely delay uptake of agent into plasma); rate of accumulation; options to prevent seizure activity—incremental dosing (unwise to inject >5 mL at one time without pause); test doses (include epinephrine and opioids for certain patients); continuous monitoring; capability for immediate ventilation and oxygenation; seizure management—preparation; detection (talking to patient invaluable); raising seizure threshold (may be able to suppress seizure activity); supplemental O2 (precautionary; morbidity related to increased central nervous system demand for O2 ); midazolam (raises seizure threshold to point of slurred speech); thiopental; succinylcholine (or rocuronium); natural history (maintain airway and circulation)

Vascular injury: hematoma—particularly if subsequently infected; compressive hematoma—case reports with transarterial techniques; can create vascular embarrassment or, more commonly, neural compression; ischemia from other etiologies—perivascular techniques in patient on vasoconstrictors probably unwise; techniques that require vasoconstrictor should be avoided; vessel embarrassment—advent of US helpful; epidural hematoma—directly related to surgical sequelae for which epidural anesthesia indicated; avoid lower extremity DVT and thromboembolic complications; movement toward use of coumadin, heparin, and low molecular weight heparin (LMWH); even those who avoid blood thinners before surgery, due to concern about superficial hematoma after surgery, give above agents within 12 to 24 hr; if following patient in PACU, block not regressing, and level going up instead of down, consider epidural hematoma; diagnosis usually involves MRI; early recognition important because decompression can be neural-sparing

Anticoagulation: nonsteroidal anti-inflammatory drugs (NSAIDs)—not problematic (24-hr withdrawal); cyclooxy-genase-2 (COX-2)—even smaller issue; aspirin—one-per-day not an issue with regional anesthesia, unless patient indicates history of bleeding; coumadin—can be problematic; withdrawal for 3 days absolute minimum, although 3% to 5% of patients still experience therapeutic effect; heparin—problems when given intravenously; withdrawal recommended for ≥12 hr before neuraxial anesthesia; LMWH—avoid neuraxial anesthesia if patient already on LMWH; after one dose, waiting 12 hr adequate; if >1 dose, wait 24 hr; cannot detect effect with prothrombin time (PT) and partial thromboplastin time (PTT), although Sonoclot analyzer option can be used; long-acting antiplatelet drugs—clopidogrel should be withheld for minimum of 5 to 7 days

Neurologic injury: high central block (provide sedative); persistent paresthesia (common in ankle block); peripheral nerve injury (related to technique used; controversy with local anesthetic solutions); relationship to block technique (eg, type and size of needle, selection of agent)