Lecture 14 - Anesthetic Risk Assessment Flashcards
1
Q
American Society of Anesthesiologist (ASA)risk classification
A
I: NHP
2
Q
Lee revised cardiac risk index
A
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%
3
Q
Surgical factors
A
- different operations have different mortality rates
- emergency operations have higher mortality rates
4
Q
High risk surgical procedures : >5%
A
- major emergency procedures
- aortic/major vascular surgery
- prolonged surgery with large fluid shifts/blood loss
- peripheral vascular surgery
5
Q
Intermediate risk
A
- intraperitoneal surgery
- intrathoracic surgery
- head and neck surgery
- major orthopedic surgery
- prostate surgery
6
Q
Low risk surgical procedures
A
- endoscopic procedures
- superficial procedures
- cataract surgery
- breast surgery
7
Q
Patient factors
A
- Age: higher number of concurrent disease, decline of physiological reserve, increased morbidity and mortality
- existing co-morbidity: cardiovascular, respiratory, neurological
- exercise tolerance
- medication
8
Q
Patient factors: cardiovascular disease
A
- 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
9
Q
Myocardial injury after non-cardiac surgery
A
- 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
10
Q
How to assess cardiac risk
A
- static testing: electrocardiography, transthoracic echocardiography, transoesophageal echocardiography, cardiac catherisation
- Dynamic testing: exercise tolerance, exercise ECG, dobutamine stress echo, dipyridimole stress echo, cardiopulmonary exercise testing
11
Q
Pre-operative functional assessment
A
- 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
12
Q
Exercise tolerance and risk
A
- if
13
Q
Cardiopulmonary exercise testing
A
- 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
14
Q
Parameters measured in cardiopulmonary exercise testing
A
- VO2 - volume of oxygen consumed
- METS - metabolic equivalents
- VCO2: volume of carbon dioxide produced in ml/min
- anaerobic threshold
15
Q
Anaerobic threshold
A
- 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
16
Q
BNP level
A
- marker of early distension of the right atrium - sign of cardiac failure
17
Q
Which cardiac conditions worry most
A
- severe stenotic lesions: flow limitng
- coronary - disease severity and extent
- AS > MS
- severe pulmonary hypertension
18
Q
Which cardiac conditions are not as worrisome
A
- regurgitant valvular lesions are rarely a problem perioperatively
- less concerned about CHF or arrythmia in the absence of ischemia
19
Q
Preoperative non-invasive testing in known or suspected CAD
A
- rest echocardiography but little insight into CAD
- simple treadmill: exercise capacity
- stress or dobutamine echo
- myocardial perfusion imaging - exercise or dipyridamole
- exercise whenenver possible
20
Q
Recommendations for coronary angiography in perioperative evaluation
A
- 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
21
Q
When is revascularization recommended
A
- fenerally only when justified by the usual clinical factors, apart from planned non-cardiac surgery
22
Q
Preoperative therapy with b-blockers
A
- 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
23
Q
Administering b blockers
A
- 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
24
Q
Perioperative surveillance
A
- 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
25
Post-operative pulmonary complications
- atelectasis: alveoli collapses
- infection, including bronchitis and pneumonia
- prolonged mechanical ventilation and resp failure
- exacerbation of underlying chronic lung disease
- bronchospasm
26
Patient related risk factors
- 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
27
Procedure related risk factors
- Surgical site: upper abdominal, thoracic, lower abdominal
- duration of surgery
- minimally invasive surgery decrease complications : less pain + early mobilization
28
Why is smoking an issue?
- increase risks of anesthesisa
- increased risks after surgery
- poorer surgical outcomes
29
Effects of cigarette smoke
- 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
30
Why does smoking increase wound infection
- 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
31
Preoperative strategies
- 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
32
Post-operative strategies
- deep breathing exercises or incentive spirometry in high risk patients
- epidural analgesia
- continuous positive airway pressure
33
Diabetes and surgery
- 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
34
Surgery and anestesia in diabetics
- 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
35
Benefits of stricter glycemic control perioperatively
- decrease infection rate
- increase recovery rate
- decrease length of stay
36
Adverse effects of hyperglycemia
- 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
37
Perioperative pharmacotherapu
- aspirin, clopidogreal, warfarin and NOAC: increased bleeding risk
- Statins: anti-inflammatory
- ACE inhibitor - increased CVS instability
- steroid - replacement therapy
