Dental Exam – look for mobile/carious teeth, edentulism, crowns, dentures, orthodontic appliances, and large tongue/tonsils.

Maximum Incisal Opening (MIO) – normal is >40 mm, <35 mm should be considered limited. Be cautious of patients with a history of temporomandibular joint disorders or a history of head and neck radiation. The ability to perform specific airway maneuvers depends in part on the degree that a patient is able to maximally open. At a MIO of 20 mm, it is possible to insert an oral or nasal airway, GlideScope ™, and perform a fiberoptic intubation. As the MIO increases to 30 mm, insertion of a laryngeal mask airway (LMA) becomes possible. At a MIO of 40 mm, direct laryngoscopy (DL) intubation may be performed.

Thyromental Distance – the distance between the top of the thyroid cartilage and the menton of the mandible. It is an indicator of the ability to displace the tongue during direct laryngoscopy. A distance of <6.5 cm (three finger breadths) may indicate difficulty with intubation.

Mandibular Protrusion – evaluate patient’s ability to protrude the lower jaw so that the mandibular incisors are in front of the maxillary incisors. This maneuver correlates with the clinician’s ability to sublux the mandible during laryngoscopy.

Neck Circumference – if greater than 43 cm (17 inches), associated with difficulty for intubation, more predictive than BMI.

Testing should be based on the history and physical of the patient and the nature of the surgical procedure.

An electrocardiogram (EKG) should be obtained in all adults over the age of 65, and any patient with a history of hypertension (HTN), cardiac disease, substance abuse, or eating disorder.

A fasting fingerstick glucose (FSG) should be obtained on all diabetics both prior to surgery and postoperatively prior to discharge.

Other lab tests that may be indicated depending on the patient’s reported history include Hematocrit (Hct), chest X-ray (CXR), urine pregnancy test (b-hCG), BMP, LFTs, coagulation studies, or echocardiogram.

During the preoperative evaluation, it is important to ask patients about their exercise capacity, as this is a significant determinant of perioperative risk. In general, patients with good exercise tolerance are at lower risk for cardiopulmonary complications during anesthesia. One commonly used measure of exercise tolerance is metabolic equivalent tasks (METs).

MET is a physiological measure that expresses the energy cost of performing various physical activities. It is expressed as the ratio of a patient’s metabolic rate during a specific physical activity over the reference metabolic rate, which is the resting or basal oxygen consumption of a 40-year-old, 70-kg man (3.5 mL O₂/kg/min or MET 1) [3].

Perioperative risk is elevated in patients with <4 METs. Activities of <4 METs include watching TV, shopping, golfing with a cart, and walking slowly (2–3 mph).

Activities associated with >4 METs include climbing a flight of stairs, bicycling, walking >4 mph, and performing housework.

ASA Class I: A healthy patient (healthy, non-smoking, no or minimal alcohol use).

ASA Class V: moribund patient who is not expected to survive without operation.

ASA Class VI: declared brain-dead patient whose organs are being removed for donor purposes.

The addition of “E” denotes emergency surgery – added when a delay in treatment of the patient would lead to a significant increase in the threat to life or body part.

Breast milk – at least 4 hours.

Infant formula – at least 6 hours.

Non-human milk – at least 6 hours.

Solids, light meals, non-clear liquids – at least 6 hours.

Heavy meal or fried/fatty foods – at least 8 hours.

Exhaled air contains 17% oxygen.

Each increase liter per minute is approximately 4% above room air.

FiO₂ = 20 + [4 L/min × L/min].

Flow greater than 4 L/min, although delivering 36%, may be uncomfortable.

Flow 8–12 L/min.

FiO₂: 35–65%.

Increase approximately 4% per liter flow.

Flow rate should be min 6–15 L/min.

FiO₂: 60–100%.

Delivered oxygen ~60%, each L/min increase will raise FiO₂ ~5%.

Can be used for spontaneously breathing patients or apneic patients via positive pressure ventilation.

Caution if full stomach, severe facial trauma or C-spine fracture.

Difficulty occurs when ventilating via the facemask is not possible because of an inadequate mask seal (e.g., beard hair), excessive gas leak, and/or excessive resistance to the ingress or egress of gas. This may be helped by oro/naso-pharyngeal airways.

Risk factors for bag mask ventilation difficulty include age greater than 55 years, BMI > 26 kg/m², edentulism, presence of a beard, and history of snoring [5].

Follows the curvature of the tongue, pulling the tongue and epiglottis away from the posterior pharyngeal wall.

Not appropriate for use in conscious patients (can cause coughing, retching, or laryngospasm due to irritation at base of tongue). Best used in the deeply anesthetized patient.

Sized by measuring from the corner of a patient’s mouth to the angle of the jaw.

Less stimulating than oropharyngeal airways, more appropriate for lightly anesthetized patients.

Lubricate prior to insertion and insert with the bevel facing the nasal septum.

Supraglottic airway that is blindly inserted into the pharynx.

Provides a patent conduit for ventilation, oxygenation, and delivery of anesthetic gases without tracheal intubation.

Less invasive than intubation but provides a more definitive airway than a facemask.

Can be used for either spontaneous ventilation or PPV.

Allows for delivery of O₂ and inhaled anesthetics during spontaneous ventilation or via PPV at pressures up to 20 cmH₂O.

Flexible LMA Tube – allows the tube to be moved out of the surgical field without displacement of the cuff, or loss of seal for the anesthesiologist.

Gold standard for airway management.

Establishes a definitive airway.

Maximal protection against aspiration of gastric contents.

Allows for delivery of O₂, inhalational anesthetics and allows for PPV with higher airway pressures than with a facemask or supraglottic airway (LMA).

Invasive technique that provides access to the airway in situations when either noninvasive maneuvers have failed or when it is clinically indicated as a primary plan to secure the airway.

Not considered a permanent airway, and after placement plans should be made for either the removal or conversion to a formal tracheostomy.

Note: In children <6 years of age, cricothyrotomy is contraindicated because the cricoid cartilage is the narrowest portion of the airway and the isthmus of the thyroid gland typically reaches the level of the cricothyroid membrane. Needle cricothyrotomy with transtracheal jet ventilation is indicated in this pediatric population.

Conversion to tracheostomy is normally recommended within 72 hours to prevent subglottic stenosis [6].

Allows for 30 minutes to 2 hours of ventilation.

Must be avoided in those with tracheal trauma.