Topic 8 Preoperative Anesthetic review
You are on your first Anesthetic rotation. Today, you will be reviewing patients in the preoperative clinic but from an Anesthetic point of view. What important things do you need to cover?
Clinical assessment
Important things to cover in the history, specifically for the Anesthetic review includes:
-Past medical history in greater detail especially when it comes to respiratory and cardiovascular conditions.
For example, if a patient has a diagnosis of heart failure, see if you can get a hold of their last Echocardiogram. This will help grade the severity and type of heart failure
-Past Anesthetic history.
This includes: complications, type of anesthesia in the past, previous surgeries, as well as family history of problems with anesthesia (screening for malignant hyperthermia)
#TIP 1 See if you can get hold of previous Anesthetic records. They are invaluable in providing details on past complications as well as special technique and equipment required to manage the airway safely.
#TIP 2 One of the best predictors for difficult intubation, is previous history of difficult intubation.
ASA
American Society of Anesthesiologists Physical Status Classification System provides an indication of the patient’s current health status prior to surgery. More importantly it helps provide an estimation of perioperative risk.
For example:
Ms A is 21 yo with no past medical history, non-smoker and does not drink alcohol. She goes to the gym three times a week. Her ASA score will be 1.
Whereas
Ms B is 55 yo; past medical history of Type 2 diabetes on insulin, hypertension, BMI 45. She does not smoke, but drinks 4 standard drinks every single day. Her ASA score will be 3.
Being anesthetized places a lot of stress on the body. ASA level can provide a clue on how the patient might react under anesthesia. There will be greater need for clinical vigilance intraoperatively for a patient with ASA 4 versus ASA 1.
MET
MET stands for metabolic equivalent. One MET equates to the amount of oxygen consumed at rest. The more difficult the physical activity, the greater the MET score.
Generally speaking, patients who have a MET of 4 or more (signified by asking if they can walk 2 flights of stairs), means that they have sufficient physiological reserve to undergo surgery. Patients with MET less than 4 have a higher risk of perioperative complications.
Airway examination
The physical exam can help identify potential difficulties in airway management, allowing time for further airway management planning. You should assess and make a note of the following:
TEETH
Relationship of teeth during normal jaw closure (eg overbite)
Health of teeth (Chipped? Loose? Missing? Crowns? Veneers? Caps? dentures? )
JAW/FACE
Shape of the palate
Ability to protrude the mandible
NECK
Length and thickness of neck
Neck masses
Range of head and neck movement ( C spine mobility)
MEASUREMENTS
Thyromental distance; measured from thyroid notch to the chin with head extended back. Thyromental distance less than 6 cm is associated with poor laryngoscopic view.
Mallampati class; assesses oropharyngeal space. Mallampati 3 and 4 is associated with greater difficulty in endotracheal intubation.
Class I: The soft palate, fauces, uvula, and tonsillar pillars are visible.
Class II: The soft palate, fauces, and uvula are visible.
Class III: The soft palate and base of the uvula are visible.
Class IV: The soft palate is not visible.
#TIP To assess Mallampati score, have the patient sitting upright, head in a relaxed and neutral position.
3. Interincisor distance (degree of mouth opening); less than 3cm is associated with difficult airway management
By incorporating the above elements in your airway examination, it will help identify any potential difficulties in airway management.
Medical conditions which can make airway management more difficult
Below is a list of medical conditions that can potentially make it more difficult to manage the airway. If you identify any of these conditions in the patient’s history, be sure to flag it with your Senior!
Anatomical: foreign body, cervical spine injury or previous surgery, maxillary or mandibular injury, soft tissue neck injury, obesity
Face: large tongue, receding mandible, prominent upper incisors, beard, craniofacial deformity, radiation therapy to the neck and face
Genetic: down’s syndrome
Neoplasm: cancer located in the upper and lower airway
Autoimmune: ankylosing spondylitis, scleroderma, rheumatoid arthritis
Preoperative fasting guideline
Instructions to provide to patients:
Clear fluids eg water- 2 hours before surgery
Light meal- 6 hours before surgery
Patients can still take their routine medications, with small sips of water, ideally several hours before their surgery.
Resources Brian Keech, Ryan Laterza. Anesthesia Secrets 6th Edition Philadelphia, PA: Elsevier/Saunders, 2020John F. Butterworth IV, David C. Mackey, John D. Wasnick Morgan & Mikhail's Clinical Anesthesiology, 6th edition. 2018 Michael Gropper Lars Eriksson Lee Fleisher Jeanine Wiener-Kronish Neal Cohen Kate Leslie. Miller's Anesthesia 9th Edition. Elsevier. 2019 Miller, Ronald D, Manuel Pardo. Basics of Anesthesia. Philadelphia, PA: Elsevier/Saunders, 2018Smith I, Kranke P, Murat I, et al. Perioperative fasting in adults and children: guidelines from the European Society of Anaesthesiology. Eur J Anaesthesiol 2011; 28:556.