Pre-operative evaluation and management

By Ronald Ombaka

Anesthetic drugs and techniques have profound effects on human physiology. Hence, a focused review of all major organ systems should be completed prior to surgery.

The goals of preoperative evaluation are to reduce patient risk and the morbidity of surgery

(with the premise that it will modify patient care and improve outcome)

This ultimately allows the anaesthesiologist to formulate an appropriate anaesthetic plan with contingencies to deal with patients comorbidity associated complications and/or need to optimize patient prior to surgery.

It is also a medicolegal document.

The process should be used to educate the patient about anesthesia and the perioperative period, answer all questions, and obtain informed consent.

thorough history and physical exam

thorough history and physical exam

thorough history and physical exam

thorough history and physical exam

Salient information obtained from history;

Indication for surgery

Site of surgery(has implications on positioning)

Urgency of procedure (? RSI)

Allergies

Prior surgeries and prior experience with anaesthetics(e.g. PONV, malignant hyperthermia )

Last meal taken

Current comorbidities(acute or chronic )

Current medications(as well as supplements)

(It is also a chance to take note of pre-anaesthetic health condition allowing comparison with outcome post-op)

Risk classification –ASA Physical status classification

ASA Physical Status 1 - A normal healthy patient ASA Physical Status 2 - A patient with mild

systemic disease ASA Physical Status 3 - A patient with severe

systemic disease ASA Physical Status 4 - A patient with severe

systemic disease that is a constant threat to life ASA Physical Status 5 - A moribund patient who

is not expected to survive without the operation ASA Physical Status 6 - A declared brain-dead

patient whose organs are being removed for donor purposes

medical status mortality

ASA I normal healthy patient without organic, biochemical, or psychiatric disease

0.06-0.08%

ASA II mild systemic disease with no significant impact on daily activity e.g. mild diabetes, controlled hypertension, obesity .

Unlikely to have an impact

0.27-0.4%

ASA III

severe systemic disease that limits activity e.g. angina, COPD, prior myocardial infarction

Probable impact 1.8-4.3%

ASA IV

an incapacitating disease that is a constant threat to life e.g. CHF, unstable angina, renal failure ,acute MI, respiratory failure requiring mechanical ventilation

Major impact 7.8-23%

ASA V moribund patient not expected to survive 24 hours e.g. ruptured aneurysm

9.4-51%

ASA VI

brain-dead patient whose organs are being harvested

ASA Physical Status Classification System

For emergent operations, you have to add the letter ‘E’ after the classification.

Airway

Evaluation of the airway involves determination of the thyromental distance, the ability to flex the base of the neck and extend the head, and examination of the oral cavity including dentition.

Mallampati classification.

Mallampati

Measurements 3-3-2-1 or 1-2-3-3 Patient ‘s fingers

Movement of the Neck

Malformations of the Skull

Teeth

Obstruction

Pathology

Class I = visualize the soft palate, fauces, uvula, anterior

and posterior pillars.

Class II = visualize the soft palate, fauces and uvula.

Class III = visualize the soft palate and the base

of the uvula.

Class IV = soft palate is not visible at all.

3 Fingers Mouth Opening

3 Fingers Hypomental Distance. (3 Fingers between the tip

of the jaw and the beginning of the neck (under the chin)

2 Fingers between the thyroid notch and the floor of the

mandible (top of the neck)

1 Finger Lower Jaw Anterior sublaxation

Skull (Hydro and Microcephalus)

Teeth ( protruded, & loose teeth. Macro and Micro mandibles)

Obstruction (obesity, short Bull Neck & swellings around the head

and neck)

Pathology (Craniofacial abnormalities & Syndromes e.g. Treacher

Collins, Goldenhar's, Pierre Robin syndromes)

.

Pierre Robin( hypertelorism; and external and middle ear deformities)

A screening evaluation should include questions regarding the history of tobacco use, shortness of breath, cough, wheezing, stridor, and snoring or sleep apnea.

The patient should also be questioned regarding the presence or recent history of an upper respiratory tract infection.

Auscultation should be used to detect decreased breath sounds, wheezing, stridor, or rales.

When screening a patient for cardiovascular disease prior to surgery, the anesthesiologist is most interested in recognizing signs and symptoms of uncontrolled hypertension and unstable cardiac disease such as ; myocardial ischemia, congestive heart failure, valvular heart disease, and significant cardiac dysrhythmias

Exercise tolerance is one of the most important determinants of perioperative risk and the need for further testing and invasive monitoring.

Inability to walk 4 blocks (1 block is100-200 meters) or climb 2 flights of stairs is defined as poor exercise tolerance.(this doubles your risk of adverse cardiovascular outcomes)

A screening of the neurological system in the apparently healthy patient can mostly be accomplished through simple observation.

The patient's ability to answer health history questions practically ensures a normal mental status.

Questions can be directed to exclude the presence of ; Increased intracranial pressure,

Cerebrovascular disease,

Seizure history,

Preexisting neuromuscular disease,

Nerve injuries,

Spinal cord Injury;

Disorders of NM junction e.g myasthenia gravis, muscular dystrophies

Each patient should be screened for endocrine diseases that may affect the perioperative course:

diabetes,

thyroid disease,

parathyroid disease,

endocrine-secreting tumors, and

adrenal cortical suppression.

significant blood loss;

respiratory compromise;

positioning

Reasonable testing

positive finding in history and physical exam.

need for baseline value in anticipation of significant

change due to surgery and medical intervention

patient's inclusion in population at higher risk

• Anesthetic indications: -Anxiolysis, sedation and amnesia. e.g. benzodiazepine(diazepam ,lorazepam) -Analgesia e.g narcotics-Drying of airway secretions e.g atropine,glycopyrrolate,scopolamine-Reduction of anesthetic requirements ,Facilitation of smooth induction -Patients at risk for GE reflux :ranitidine ,metoclopramide , sodium citrate

• Surgical indications: -Antibiotic prophylaxis for infective endocarditis. -Prophylaxis against DVT for high risk patients : low-dose heparin or aspirinintermittent calf compression, or warfarin.

• Co-existing Disease indications: Some medications should be continued on the day of surgery e,g B blockers, thyroxine. Others are stopped e.g oral hypoglycemics and antidepressants .Steroids within the last six months may require supplemental steroids

INGESTED MATERIAL

MINIMUM FASTING PERIOD,

APPLIED TO ALL AGES (hr)

Clear liquids 2

Breast milk 4

Infant formula 6

Nonhuman milk 6

Light meal (toast and clear liquids) 6