TaiChing

Purpose: assess the risks of anesthesia and surgery--> provide appropriate advice to their patient and family.

Topics of study:
A. General condition
B. Cardiorespiratory health
C. Familial conditions relevant to anesthesia

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A. General condition

What is the ASA grading system?

1. No systemic disease
2. systemic disease with good compensation
3. systemic disease result in mild disability
4. incapacitating disease threatening to life
5. not expected to survive 24 hours
6. brain death
E: emergency

What is the mortality associated with each grade?

ASA 1 : 0.06~0.08%
ASA 2 : 0.27~0.4%
ASA 3 : 1.8~4.3%
ASA 4 : 7.8~23%
ASA 5 : 9.4~51%
ASA 6

Why is a history of previous anesthesia important?

For choose proper anesthetic method, reducing perioperative morbidity and mortality.

B. Cardiorespiratory health

Describe a rapid assessment of the extent of a patient's cardiorespiratory reserve.

Exercise tolerance is a major determinant of perioperative risk that is evaluated by the estimated energy requirement for various activities and graded in metabolic equivalents (MET)
1~4 METs: standard light home activities, walk around house
5~9 METs: climb a flight of stairs, run a short distance
>10 METs: strenuous sports

How may lung disease be optimized preoperatively?

cessation of smoking

How should a patient with asthma be managed perioperatively?

1. PFTs before and after bronchodilation therapy
2. keep steroids and bronchodilators usage

How may cardiac disease be optimized prior to surgery?

1. Continue preoperative cardiac medications
2. Supplemental oxygen
3. Stop anticoagulant, warfarin for 3 days; clopidogrel for 7 days.

What is the significance of 'mild heart failure' to anesthetists?

mild heart failure suggests intermediate risk for anesthesia.
According to Ezekiel, intermediate risk factors is defined as "mild angina pectoris, prior MI, compensated or prior CHF, diabetes mellitus"

Many drugs used in hypertension and cardiac disease interact with anesthetic agents. Describe some of these.

1. alpha blocker(prezosin, phentolamine, phenoxybenzamine): hypotension, reflex tachcardia
2. beta blocker(propranolol, atenolol): hypotension, bradycardia, AV block, decreased contractility
3. mixed alpha/neta blocker(Labetalol): hypotension, bradycardia, AV block
4. calcium channel blocker(verapamil, diltiazem, nefedipin, nicardipine): hypotension, bradycardia, AV block
5. direct vasodilator(NTG, isosorbide, hydralazine): hypotension, reflex tachcardia
6. ACEI(captopril, enalapril): hypotension, hyperkalemia
7. ARB(Losatan, valsatan): hypotension, hyperkalemia
8. Diuretics(Thiazide, furosemide): hypovolemia, hypokalemia

C. Familial conditions relevant to anaesthesia

What is the significance of a history of severe muscle pain after exercise or previous anesthesia?

 higher risk developing fulminant skeletal muscle hypermetabolic syndrome result in malignant hyperthermia

What is the relevance of Myasthenia Gravis to anesthesia?

 Myasthenia Gravis is very sensitive to muscle relaxants such as succinylcholine, which can result in prolonged immobilization or even respiratory insufficiency.

What is Malignant Hyperpyrexia.

Fulminant skeletal muscle hypermetabolic syndrome occurring in genetically susceptible patients after exposure to an anesthetic triggering agent. Triggering anesthetics include halothane, enflurane, isoflurane, desflurane, sevoflurane, and succinylcholine.

How may it present during anesthesia?

Onset: tachycardia, tachypnea, hypercarbia
Early sign: tachycardia, tachypnea, unstable BP, sweating, rapid incresed BT, coca-cola like urine

How would you treat acute porphyria?

1. Stop anesthetics ASAP
2. hyperventilation
3. Dantrolene 2.5mg/kg IV, repeated per 5~10 mins
4. Correct metabolic acidosis with sodium bicarbonate 1~2mEq/kg IV follow ABG study
5. Correct hyperkalemia with bicarbonate, or glucose plus RI
6. actively cool patient with cold NS, surface cooling, and cold lavage
7. maintain urine output > 1~2mL/kg/hr with hydration and furosermide
8. Follow up labs data for coagulation, urine myoglobin, ABG, K, Ca, lactate, and CPK.

Discuss the effects of pseudocholinesterase deficiency.

pseudocholinesterase deficiency is defined as inherited enzyme abnormality resulting in abnormally slow metabolic degradation of exogenous choline ester drugs such as succinylcholine, causing perlonged respiratory paralysis unexpectedly.

Which drugs should be used with caution in these patients with pseudocholinesterase deficiency?

Anticholinesterase inhibitors such as succinylcholine. Others including glucocorticoids, OCPs, MAOI....

Reference:
1. Handbook of anesthesiology 2007-2008
2. Clinical Anesthesia
3. A Zambouri: Preoperative evaluation and preparation for anesthesia and surgery. Hippokratia. 2007 Jan–Mar; 11(1): 13–21.