Ottawa Anesthesia Primer. Patrick Sullivan
investigations to identify and avoid potential problems, assess the severity of the patient’s condition, and optimize the patient’s condition prior to surgery. The first step is to ask the patient to explain the reason for the surgery. Ascertain information about the nature of the problem; determine its severity and any therapeutic interventions that have been used. Careful consideration of the surgical procedure will determine the likelihood of significant blood loss, cardiorespiratory compromise, or unusual positioning requirements (i.e., prone, lateral, lithotomy, etc.). This information can also be useful in planning for venous access, specific monitoring, and choice of anesthetic technique.
Anesthetic History:
The patient undergoing anesthesia and surgery should be carefully questioned about any reaction to previous anesthetics, and information that the patient considers relevant should be documented. A review of the patient’s previous anesthetic records may provide additional information concerning any prior perioperative complications and may offer solutions to avoid similar problems in the future.
The patient should be asked about a family history of adverse anesthetic problems. Malignant hyperthermia and plasma cholinesterase deficiency are two such hereditary disorders that manifest under anesthesia (for further information, see Chapter 25: Unusual Anesthetic Complications).
Problem Identification:
Anesthetic drugs and techniques can have a profound effect on human physiology. The anesthesiologist uses the preoperative evaluation to identify medical conditions that may be adversely affected by the administration of anesthetic medications. Special attention is paid to symptoms and diseases related to the cardiovascular, respiratory, and neuromuscular systems as they will be directly influenced by the anesthetic medications. A systems-based review can be used to illicit additional relevant information. Ask the patient general screening questions directed at all major body systems, and then narrow the focus if the patient gives positive responses to any of the questions. This information can then be used to develop an appropriate “patient-specific” anesthetic plan.
When available, a recent preoperative evaluation may be used to guide the assessment. Even when the patient has been seen in a pre-assessment clinic, it is of paramount importance that anesthesiologists perform a final preanesthetic assessment to formulate their own assessment and plan. The final preoperative evaluation should include a review of the patient’s history, physical examination, and most recent investigations.
Optimization prior to surgery requires identifying the patient’s medical condition(s) and determining the severity and stability or progression of disease. Patients scheduled for elective surgery who have significant unstable symptoms may need to have their surgery postponed.
Review of Systems:
Functional Capacity
A patient’s functional capacity or incapacity is a powerful predictor of postoperative cardiopulmonary1-3 and neurocognitive4 complications. Exercise capacity is measured quantitatively in terms of metabolic equivalents (1MET = consumption of 3.5 mL O2∙kg-1∙min-1 of body weight). To highlight the possible need for further evaluation, preoperative evaluation guidelines define poor exercise tolerance as ≤ 4 METS. Hence, to evaluate a patient’s preoperative functional capacity, one question to ask might be, “Can you climb a flight of stairs without stopping or becoming short of breath?” Table 3.1 provides examples of daily activities and their measured metabolic equivalencies.
Cardiovascular System:
Several disease processes can influence the cardiovascular system, and cardiovascular physiology can be altered significantly in the perioperative period.
Patients with coronary artery disease (CAD) are at risk for myocardial ischemia or infarction throughout the perioperative period. The exact mechanism of perioperative myocardial infarction (MI) is complex and involves both thrombus and supply-demand mechanisms. The patients at highest risk are those who have had a recent MI and those with unstable angina.
When assessing a patient at risk for CAD, find out whether the patient previously suffered a MI and, if so, determine the management strategy used. Possible strategies could necessitate treatment with medical therapy alone, percutaneous coronary intervention (PCI), stenting, or coronary artery bypass grafting (CABG).
The patient with a coronary stent placed within the preceding year is at high risk of perioperative cardiac events.6 The evaluation requires multidisciplinary consultation and careful planning. Cardiology consultation may be required.
Determine the severity and frequency of the patient’s ongoing angina pain using standardized reference scales, such as the Canadian Cardiovascular Society Functional Classification of Angina (Table 3.2)7, and be sure to get a sense of the stability or progression of the patient’s disease. Inquire about other coexisting non-cardiac diseases, such as hypertension, cerebrovascular disease, diabetes, smoking, and renal insufficiency. The presence of these conditions places the patient at an increased risk of a perioperative cardiac event.
The presence of congestive heart failure (CHF) is one of the most important risk factors for perioperative morbidity and mortality. When assessing a patient at risk for cardiac disease, the goal is to identify and minimize the effects of heart failure. Inquire about signs and symptoms of CHF (Table 3.3), including fatigue, syncope, dyspnea, orthopnea, paroxysmal nocturnal dyspnea (PND), and cough.8 Patients exhibiting signs and symptoms of decompensated or unstable CHF have an increased postoperative risk and should be optimized prior to elective surgery.
Valvular heart disease presents a special set of concerns to the anesthesiologist, including unfavorable and even dangerous alterations in hemodynamics with general and major regional anesthetic techniques. Significant valvular disease may present with a murmur, arrhythmia, or poor functional capacity. When a murmur is heard, an attempt should be made to characterize it in terms of intensity, location, timing (within the cardiac cycle), and radiation.
A systolic murmur heard over the right clavicle in an elderly patient would be considered highly suspicious of aortic stenosis and require further evaluation if accompanied by left-ventricular hypertrophy (LVH) that has been substantiated by (echocardiography) ECG.9
The preoperative assessment may identify a history of arrhythmia, previous pacemaker insertion, or symptoms suggesting the need for a pacemaker.
Electrosurgical cautery units as well as other electrical devices in the operating room can interfere with the normal functioning of a pacemaker or implantable cardioverter-defibrillator (ICD). If the patient has a pacemaker or ICD, students should ask the anesthesiologists for their recommendations concerning perioperative management, as a cardiology assessment and intervention may be required prior to the surgery.10
The Respiratory System:
There is wide spectrum of illness associated with the “common cold”. Patients with signs of severe systemic infection or pneumonia (fever, cough, purulent rhinitis, and rhonchi) are at an increased risk for adverse airway events during surgery. Following a complicated upper respiratory tract infection (URTI), hyper-reactive airways may require several weeks to normalize.11 There is no defined “safe period” to wait, and the decision to postpone anesthetic care should