Elements of the Preoperative History
Patients presenting for elective surgery and anesthe-sia typically require a focused preoperative medical history emphasizing cardiac and pulmonary func-tion, kidney disease, endocrine and metabolic dis-eases, musculoskeletal and anatomic issues relevant to airway management and regional anesthesia, and responses and reactions to previous anesthetics. The ASA publishes and periodically updates general guidelines for preoperative assessment.
Guidelines for preoperative cardiac assessment are available from the American College of Cardiology/American Heart Association and from the European Society of Cardiology (see Guidelines). The focus of preoperative cardiac assessment should be on determining whether the patient’s condition can and must be improved prior to the scheduled procedure, and whether the patient meets criteria for further cardiac evaluation prior to the scheduled surgery. Clearly the criteria for what must be done before elective arthroplasty will differ from what must be done before an operation for resectable pancreatic cancer, given the benign results of a delay in the former pro-cedure and the potential life-shortening effects of a delay in the latter procedure. In general, the indications for cardiovascular investigationsare the same in surgical patients as in any other patient. Put another way, the fact that a patient is scheduled to undergo surgery does not change the indications for such measures as noninvasive stress testing to diagnose coronary artery disease.
Perioperative pulmonary complications, most notably postoperative respiratory depression and respiratory failure, are vexing problems that have become seemingly more common as severe obe-sity and obstructive sleep apnea have increased in incidence. A recent guideline developed by the American College of Physicians takes an aggres-sive stance; it identifies patients 60 years of age or older, those with chronic obstructive lung disease, those with markedly reduced exercise tolerance and functional dependence, and those with heart failure as potentially requiring preoperative and postop-erative interventions to avoid complications. The risk of postoperative pulmonary complications is closely associated with these factors, and with the following: ASA class (class 3 and 4 patients have a markedly increased risk of pulmonary complica-tions relative to class 1 patients), cigarette smok-ing, longer surgeries (>4 h), certain types of surgery (abdominal, thoracic, aortic aneurysm, head and neck, and emergency surgery), and general anes-thesia (compared with cases in which general anes-thesia was not used).
Efforts at prevention of pulmonary complica-tions should focus on cessation of cigarette smoking prior to surgery and on lung expansion techniques (eg, incentive spirometry) after surgery in patients at risk. Patients with asthma, particularly those receiving suboptimal medical management, have a greater risk for bronchospasm during airway manipulation. Appropriate use of analgesia and monitoring are key strategies for avoiding post-operative respiratory depression in patients with obstructive sleep apnea.
Appropriate targets for control of diabetes mellitus and of blood glucose in critically ill patients have been subjects of great debate over the past decade. “Tight” control of blood glucose, with a target level in the normal range, was shown in the Diabetes Control and Complications Trial to improve out-comes in ambulatory patients with type 1 diabetes mellitus. It has become the usual practice to obtain a blood glucose measurement on the morning of elec-tive surgery. Unfortunately, many diabetic patients presenting for elective surgery do not maintain blood glucose within the desired range. Other patients, who may be unaware that they have type 2 diabetes, present with blood glucose measurements above the normal range. Adequacy of long-term blood glucose control can be easily andrapidly assessed by measurement of hemoglobin A1c. In patients with abnormally elevated hemoglobin A1c, referral to a diabetology service for education about the disease and adjustment of diet and medi-cations to improve metabolic control may be benefi-cial. Elective surgery should be delayed in patients presenting with marked hyperglycemia; this delay might consist only of rearranging the order of sched-uled cases to allow insulin infusion to bring the blood glucose concentration closer to the normal range before surgery begins.
Th ree important coagulation issues that must be addressed during the preoperative evaluation are how to manage patients who are taking warfarin on a long-term basis; (2) how to manage patients who are taking clopidogrel and related agents; andhow to safely provide regional anesthesia to patients who either are receiving long-term antico-agulation therapy or who will receive anticoagula-tion perioperatively. In the first circumstance, most patients who undergoing anything more involved than minor surgery will require discontinuation of warfarin 5 days in advance of surgery to avoid exces-sive blood loss. The key question to be answered is whether the patient will require “bridging” therapy with another agent while warfarin is discontinued.In patients deemed at high risk for thrombosis (eg, those with certain mechanical heart valveimplants or with atrial fibrillation and a prior throm-boembolic stroke), warfarin should be replaced by intravenous heparin or, more commonly, by intra-muscular heparinoids to minimize the risk. In patients receiving bridging therapy for a high risk of thrombosis, the risk of death from excessive bleed-ing is an order of magnitude lower than the risk of death or disability from stroke if the bridging ther-apy is omitted. Patients at lower risk for thrombosis may have warfarin discontinued and then reinitiatedafter successful surgery. Decisions regarding bridg-ing therapy often require consultation with the phy-sician who initiated the warfarin therapy.
Clopidogrel and related agents are most often administered with aspirin (so-called dual antiplate-let therapy) to patients with coronary artery dis-ease who have received intracoronary stenting. Immediately after stenting, such patients are at increased risk of acute myocardial infarction if clopidogrel (or related agents) and aspirin are abruptly discontinued for a surgical procedure.Therefore, current guidelines recommend postponing all but mandatory emergencysurgery until at least 1 month after any coronary intervention and suggest that treatment options other than a drug-eluting stent (which will requireprolonged dual antiplatelet therapy) be used in patients expected to undergo a surgical procedure within 12 months after the intervention (eg, in a patient with colon cancer who requires treatment for coronary disease). As the available drugs, treat-ment options, and consensus guidelines are updated relatively frequently, we recommend con-sultation with a cardiologist regarding safe man-agement of patients receiving these agents who require a surgical procedure.
The third circumstance—when it may be safe to perform regional (particularly neuraxial) anesthesia in patients who are or will be receiving anticoagu-lation therapy—has also been the subject of debate among hematologists and regional anesthetists. The American Society of Regional Anesthesia publishes a periodically updated consensus guideline on this topic, and other prominent societies (eg, the Euro-pean Society of Anaesthesiologists) also provide guidance on this topic.
Since Mendelson’s 1946 report, aspiration of gastric contents has been recognized as a potentially disas-trous pulmonary complication of surgical anesthe-sia. It has also been long recognized that the risk of aspiration is increased in certain groups of patients: pregnant women in the second and third trimes-ters, those whose stomachs have not emptied after a recent meal, and those with serious gastroesopha-geal reflux disease (GERD).Although there is a consensus that pregnant women and those who have recently (within 6 h) consumed a full meal should be treated as if they have “full” stomachs, there is less consensus as to the necessary period of time in which patients must fast before elective surgery. Proof of the lack of consen-sus is the fact that the ASA’s guideline on this topic was voted down by the ASA House of Delegates sev-eral years in a row before it was presented in a form that received majority approval. The guideline as approved is more permissive of f luid intake than many anesthesiologists would prefer, and many medical centers have policies that are more restrictive than the ASA guideline on this topic. The truth is that there are no good outcomes datato support restricting fluid intake (of any kind or any amount) more than 2 h before induction of general anesthesia in healthy patients undergoing elective procedures; indeed, there is evidence that nondia-betic patients should be encouraged to drink glucose-containing fluids up to 2 h before induc-tion of anesthesia.
Patients with a history of GERD present vex-ing problems. Some of these patients will clearly be at increased risk for aspiration; others may carry this “self-diagnosis” based on television advertise-ments or conversations with friends and family, or may have been given this diagnosis by a physician who did not follow the standard diagnostic crite-ria. Our approach is to treat patients who have only occasional symptoms like any other patient without GERD, and to treat patients with consistent symp-toms (multiple times per week) with medications (eg, nonparticulate antacids such as sodium citrate) and techniques (eg, tracheal intubation rather than laryngeal mask airway) as if they were at increased risk for aspiration.