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.
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