M → Machine
S → Suction
M → Monitors
A → Airway
I → IV
D → Drugs
S → Special
The first “M” stands for the anesthesia Machine. In performing a machine check, one should use a written check list in order to ensure that nothing is overlooked. A typical machine check will include:
1.
Assure an adequate source of gases is coming from the wall
2.
Ensure an alternative source of oxygen (E-cylinder) is attached to the back of the anesthesia machine and that it is full
3.
Calibrate the oxygen sensor
4.
Make sure fail-safe alarms are working
5.
Check the level of volatile agent in the machine vaporizers
6.
Perform a high pressure test
7.
Perform a low pressure test
8.
Make sure ventilator bellows are working
Suction is a vital part of any room setup. It is imperative that suction be present and powerful enough to quickly evacuate any secretions in the oropharynx if they are present on induction – as this can improve the anesthesia provider’s view of the airway structures and help avoid aspiration of gastric contents. Prior to bringing a patient into the operating room, the anesthesiologist should ensure that there is an adequate source of suction available and that it will reach the patient.
The second “M” of the mnemonic reminds an anesthesia provider to prepare the standard American Society of Anesthesiologists recommended monitors as well as to consider if additional or invasive monitoring is necessary. Minimum monitoring requirements (see Chap. 11) include pulse oximetry, blood pressure, ECG, and capnography.
The Airway part of the mnemonic is vital to ensure that the necessary airway equipment is present and in good working order. If there is a possibility that the patient may have a difficult airway, emergency airway equipment or a difficult airway cart should be readily available. The minimum airway set up should include a working laryngoscope with at least 2 types and sizes of blades. An endotracheal tube of appropriate size should also be available and the endotracheal cuff should be tested to ensure that it is patent.
The “IV” portion of the mnemonic is a cue to consider how much intravenous access will be necessary for a given case. The degree of access required is determined by the expected blood loss and intraoperative fluid requirements. For patients, you may also need fluid warmers, pressure bags, rapid infusers, or even central venous access. Again, ideally these considerations should be made before the case begins.
The anesthesiologist must have an adequate supply of Drugs. This includes medications necessary to induce and maintain anesthesia, as well as emergency medications should the patient require vasoactive, inotropic, or chronotropic support. Typically, succinycholine, atropine, ephedrine, and phenylephrine are drawn up and available in addition to standard induction drugs (propofol, fentanyl).
The final “S” of the mnemonic encompasses all other considerations about the case such as padding, positioning, or other Special equipment.
As a part of this “pre-flight checklist,” the anesthesia provider should also carefully consider the preoperative assessment of the patient and administer any preoperative medications that might be appropriate given the patient’s comorbidities. Typical preoperative medications might include antibiotics, sedatives for anxiolysis, antiemetics for patients at risk of post-operative nausea, and antacids for patients at high risk of gastric aspiration.
Takeoff
The two most difficult and dangerous times for a pilot come during takeoff and landing – this corresponds to induction and emergence during anesthesia. Both the pilot and the anesthesiologist work hard to ensure a safe and smooth takeoff and landing.
Prior to induction, the anesthesiologist will apply monitors to the patient. After confirming that the patient is appropriate for anesthesia and that all of the monitors are working, the anesthesiologist will preoxygenate the patient by having them inhale 100 % oxygen through a sealed mask. The purpose of preoxygenation is to replace the nitrogen that is in the patient’s lungs with oxygen – as well as to maximally oxygenate all of the patient’s vital organs prior to induction. This essential step is a safety measure, which will help ensure that the patient is best able to tolerate any period of apnea from the time of anesthetic induction to the time when the airway is secured.
After the patient is maximally oxygenated, the anesthesiologist will induce anesthesia in the patient, usually with a combination of sedative hypnotics and analgesic drugs. After medications are given, the anesthesiologist will check for a lid-lash reflex by brushing a finger gently across the eye lashes. If no blink reflex is elicited, a mask airway will then be established by applying gentle positive pressure to the breathing circuit. Only after a mask airway has been established will paralytic agents then be administered to allow further manipulation of the airway. With the airway secured, the patient can then be properly positioned for surgery, prepped, and draped. Prior to surgical incision, a “time-out” or “hard stop” should be performed to verify that the correct procedure is about to be undertaken on the correct patient.
Cruising Altitude
Once a plane has reached altitude, many people think that the pilot can just turn on the auto-pilot and take a nap – but this is simply not true. The pilot and co-pilot must remain vigilant, constantly check the instruments, and communicate with the air traffic controllers to avoid a mishap. Similarly, during the maintenance phase of anesthesia, although on the surface it may appear that nothing is happening, the anesthesiologist must remain as vigilant as ever. The needs of a patient during the maintenance portion of an anesthetic may include fluid resuscitation, adjustment of the anesthetic and analgesic agents, monitoring of the patient’s blood pressure, heart rate and temperature, and paying attention to what is going on in the surgical field.
Landing
Landing a plane safely is the goal of every pilot just as a safe wake up and extubation is the goal of every anesthesiologist. Occasionally passengers on a plane will clap after a successful touchdown; similarly, our patients expect us to land them safely and comfortably. Depending on the patient, the anesthesiologist can choose to remove the endotracheal tube while the patient is still deeply asleep (Stage 3) or fully awake (Stage 1). Patients who have their airways manipulated during the intermediate Stage 2 of anesthesia are much more likely to suffer from laryngospasm and agitation than patients in either Stage 1 or Stage 3. There are multiple numerical endpoints that anesthesia providers use to ensure that a patient is ready for extubation. If a patient is going to be extubated awake, he/she should be following commands, able to oxygenate and ventilate without assistance, and able to protect his/her airway. The 4 stages of general anesthesia are outlined in the Table 12.2.
Table 12.2
Stages of general anesthesia
Stage 1 – Amnesia | Patients should follow commands; respiration pattern typically regular |
Stage 2 – Delirium | Period of uninhibited excitation; patients at risk for laryngospasm; pupils often divergent; respirations often irregular |
Stage 3 – Surgical anesthesia | Target depth for anesthesia during surgery; respiration pattern typically regular |
Stage 4 – Overdosage | Patients at risk for hypotension and cardiovascular collapse |
Taxi to the Terminal
The taxi to the terminal and the post flight check list is analogous to the trip from the operating room to the post anesthesia recovery area (PACU). The anesthesia provider should be at the head of the bed continuously evaluating the patient and ready to support the airway if necessary. Once in the PACU, the anesthesiologist will give a report to the PACU nurse and turn the care of the patient over to the PACU staff. Orders should be written to prepare for potential postoperative problems, such as pain, post operative nausea and vomiting, hypoxia, and blood pressure and heart rate perturbations (see Chap. 27, Postoperative Care Unit and Common Postoperative Problems) (Table 12.3).
Table 12.3
Action sequence of a general anesthetic
Air plane analogy | Anesthesia tasks | Important points |
|---|---|---|
Preflight check | Operating room setup Preoperative patient evaluation Preoperative medications | M.S.M.A.I.D.S Assessment of medical history Confirm NPO status Obtain informed consent Obtain I.V. access Administer appropriate preoperative medications and/or anxiolysis |
Takeoff | Patient monitoring Induction of anesthesia Airway management | Place and confirm appropriate monitors Position patient and pad pressure points Preoxygenate Administer induction agent Place endotracheal tube or other advanced airway device |
Cruising altitude | Maintenance of anesthesia
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