Lecture 14 - Anesthetic Risk Assessment

Question 1

American Society of Anesthesiologist (ASA)risk classification

Answer 1

I: NHP

Question 2

Lee revised cardiac risk index

Answer 2

6 point score

• High risk surgical procedure
• History of IHD
• History of CCF
• History of cerebrovascular disease
• Insulin-dependent diabetes mellitus
• Chronic renal failure

Risk of major cardiac complication

• 0pt: 0.4%
• 1pt: 0.9%
• 2 pt: 7%
• 3+ pt: 11%

Question 3

Surgical factors

Answer 3

• different operations have different mortality rates

- emergency operations have higher mortality rates

Question 4

High risk surgical procedures : >5%

Answer 4

• major emergency procedures
• aortic/major vascular surgery
• prolonged surgery with large fluid shifts/blood loss
• peripheral vascular surgery

Question 5

Intermediate risk

Answer 5

• intraperitoneal surgery
• intrathoracic surgery
• head and neck surgery
• major orthopedic surgery
• prostate surgery

Question 6

Low risk surgical procedures

Answer 6

• endoscopic procedures
• superficial procedures
• cataract surgery
• breast surgery

Question 7

Patient factors

Answer 7

• Age: higher number of concurrent disease, decline of physiological reserve, increased morbidity and mortality
• existing co-morbidity: cardiovascular, respiratory, neurological
• exercise tolerance
• medication

Question 8

Patient factors: cardiovascular disease

Answer 8

• approximately 75% of patients who suffer perioperative death have cardiovascular disease
• conditions that are high odds ratio for cardiovascular death within 30 days of operation are: Previous MI, Angina, Hypertension, renal failure, cardiac failre

Question 9

Myocardial injury after non-cardiac surgery

Answer 9

• myocardial ischeamia during or within 30 days after non-cardiac surgery
• incidence 8%
• 10% risk of death within 30 days
• 84% of patients with myocardial injury are asymptomatic - no chest pain or shortness of breath

Question 10

How to assess cardiac risk

Answer 10

• static testing: electrocardiography, transthoracic echocardiography, transoesophageal echocardiography, cardiac catherisation
• Dynamic testing: exercise tolerance, exercise ECG, dobutamine stress echo, dipyridimole stress echo, cardiopulmonary exercise testing

Question 11

Pre-operative functional assessment

Answer 11

• 1 MET = 3.5 ml O2/kg/min
• 1 MET - eating and dressing
• 4 MET = climbing 2 flights of stairs
• > 10 MET: able to participate in strenuous sport

Question 12

Exercise tolerance and risk

Answer 12

• if

Question 13

Cardiopulmonary exercise testing

Answer 13

• examines the ability of the CVS to deliver oxygen to tissues under stress
• if a patient is unable to elevate oxygen delivery to the required levels they are more likely to have a poor outcome
• myochardial ischeamia in absence of heart failure has little effect on outcome
• its an objective test to determine pre-operative fitness
• ## corelates well with post-operative survival

Question 14

Parameters measured in cardiopulmonary exercise testing

Answer 14

• VO2 - volume of oxygen consumed
• METS - metabolic equivalents
• VCO2: volume of carbon dioxide produced in ml/min
• anaerobic threshold

Question 15

Anaerobic threshold

Answer 15

• during exercise, when rise in VCO2 becomes disproportionate to rise in VO2
• indicates the level of exercise where body has reached maximal aerobic capacity
• if anerobic threshold >11 ml/min/kg, mortality rate is 0.8%
• if anerobic threshold is

Question 16

BNP level

Answer 16

• marker of early distension of the right atrium - sign of cardiac failure

Question 17

Which cardiac conditions worry most

Answer 17

• severe stenotic lesions: flow limitng
• coronary - disease severity and extent
• AS > MS
• severe pulmonary hypertension

Question 18

Which cardiac conditions are not as worrisome

Answer 18

• regurgitant valvular lesions are rarely a problem perioperatively
• less concerned about CHF or arrythmia in the absence of ischemia

Question 19

Preoperative non-invasive testing in known or suspected CAD

Answer 19

• rest echocardiography but little insight into CAD
• simple treadmill: exercise capacity
• stress or dobutamine echo
• myocardial perfusion imaging - exercise or dipyridamole
• exercise whenenver possible

Question 20

Recommendations for coronary angiography in perioperative evaluation

Answer 20

• Class I: patients with suspected or known CAD
• evidence for high risk of adverse outcome based on non-invasive test results
• angina unresponsive to adequate medical therapy
• unstable angina particularly when facing intermediate risk or nigh risk noncardiac surgery
• equivocal non-invadive test results in patients at high clinical risk undergoing high-risk surgery

Question 21

When is revascularization recommended

Answer 21

• fenerally only when justified by the usual clinical factors, apart from planned non-cardiac surgery

Question 22

Preoperative therapy with b-blockers

Answer 22

• Class I: when b-blockers have been required in recent past for angina or hypertension. Also for patients undergoing vascular surgery with ischemia on preoperative testing
• Class IIa: when preoperative assessment identifies untreated hypertension, known CAD or major CAD risk factor
• Class IIIL contrainidication to b-blocade
• b-blockers reduce oxygen consumption of the hear

Question 23

Administering b blockers

Answer 23

• start pre-op : titrate to HR 50-60bpm
• short acting b-blockers provide more flexible dosing
• Give orally if possible, with IV supplementation when patient is NPO
• b-blockers preopertively at least a week befor

Question 24

Perioperative surveillance

Answer 24

• post operative myocardial ischemia is the strongest predictor of perioperative cardiac morbidity
• for patients with known or suspected CAD, undergoing high or intermiediate risk procedure: check ECG at baseline, immediately after procedure, and daily for 2 days. Also check cardiac troponin measurements 24 hours post op and on day 4, or hospital discharge

Question 25

Post-operative pulmonary complications

Answer 25

• atelectasis: alveoli collapses
• infection, including bronchitis and pneumonia
• prolonged mechanical ventilation and resp failure
• exacerbation of underlying chronic lung disease
• bronchospasm

Question 26

Patient related risk factors

Answer 26

• definite risk factors: COPD, smoking within 8 weeks of surgery
• Probable risk factors: GA, Emergency surgery, elevated PaCO2
• Possible risk factor: currect URTI, abnormal CXR, age >65, peri-operative NG tube placement

Question 27

Procedure related risk factors

Answer 27

• Surgical site: upper abdominal, thoracic, lower abdominal
• duration of surgery
• minimally invasive surgery decrease complications : less pain + early mobilization

Question 28

Why is smoking an issue?

Answer 28

• increase risks of anesthesisa
• increased risks after surgery
• poorer surgical outcomes

Question 29

Effects of cigarette smoke

Answer 29

• Acute physiological effects: increases sympathetic tone, lung inflammation, decrease tissue PO2
• Pathophysiological effects: Atherosclerosis, endothelial dysfunction, decrease mucociliary clearance
• chronic pharmacological effects: drug metabolism enzyme induction, nicotinic receptor function altered

Question 30

Why does smoking increase wound infection

Answer 30

• poor microcirculation
• reduced oxygen content and delivery
• local thrombosis: nicotine increase platelet adhesiveness and vasoconstriction
• CN - impairs cellular enzymes for MO phosphorylation
• collagen production is reduced

Question 31

Preoperative strategies

Answer 31

• smoking cessation for 8 weeks
• inhaled ipratropium for all patients with clinically significant COPD
• inhaled b-agonists for patients with COPD or asthma who have wheezes or dyspnea
• preoperative corticosteroids for patients with COPD or asthma who are not optimized to bes baseline and whose airway obstruction has not been maximally reduced
• antibiotics for patients with infected sputum
• delay elective surgery if resp infection present

Question 32

Post-operative strategies

Answer 32

• deep breathing exercises or incentive spirometry in high risk patients
• epidural analgesia
• continuous positive airway pressure

Question 33

Diabetes and surgery

Answer 33

• 50% of all diabetics present for surgery during their life time
• perioperative morbidity and mortality more in diabetic due to ischemia, silent MI, autonomic neuropathy, renal dysfunction, infection, septicemia

Question 34

Surgery and anestesia in diabetics

Answer 34

• increase neuroendocrine stress response leading to hyperglycemia and increased catabolism
• non diabetic patients can increase insulin secretion to maintain glucose homeostasis during surgery
• diabetic patients cannot compensate so BGL rise
• T1D: susceptoble to diabetic keto-acidosis
• T2D: risk hyperglycemic hyperosmolar nonketotic syndrome

Question 35

Benefits of stricter glycemic control perioperatively

Answer 35

• decrease infection rate
• increase recovery rate
• decrease length of stay

Question 36

Adverse effects of hyperglycemia

Answer 36

• hinders collagen production - reduced tensile strength of wounds
• impais leukocyte chemotaxis and phagocytosis - increase infection risk
• increase plasminogen activator factor inibitor and abnormal platelet function
• greater mortality, increased deep wound infections, more overall infection

Question 37

Perioperative pharmacotherapu

Answer 37

• aspirin, clopidogreal, warfarin and NOAC: increased bleeding risk
• Statins: anti-inflammatory
• ACE inhibitor - increased CVS instability
• steroid - replacement therapy