2) Evaluation of the signs and stages of anesthesia during emergence

    a) It is important to be able to evaluate a patient’s response to anesthetic drugs so that the patient’s care may be appropriately managed during emergence from anesthesia.

  i) Guedel defined four stages of anesthesia that occur in unpremedicated patients allowed to breathe spontaneously during ether anesthesia (1).

  ii) The Guedel system described the respiratory changes, pupillary alterations, eye movements, and changes in vomiting and swallowing responses that occur at various depths of anesthesia.

(1) In modern practice, they are only seen during emergence, as intravenous or inhalation induction is too rapid. In addition, the use of medications such as opioids and neuromuscular blocking agents, as well as the use of mechanical ventilation, make the pupillar changes and the respiratory patterns described by Guedel unreliable.

(2) Stage 1: Amnesia and analgesia

   (a) From the beginning of induction of anesthesia to loss of consciousness

(3) Stage 2: Delirium

   (a) From the loss of consciousness to the onset of automatic breathing

   (b) The eyelash reflex disappears but other reflexes remain intact.

   (c) Coughing, vomiting, and struggling may occur.

   (d) Respiration can be irregular, with breath holding.

(4) Stage 3: Surgical anesthesia

   (a) Plane I—sleep

     (i) From the onset of automatic respiration to the cessation of eye movements

     (ii) Eyelid reflex is lost, swallowing reflex disappears, and marked eye movement may occur.

     (iii) The conjunctival reflex is lost at the bottom of the plane.

   (b) Plane II—sensory loss

     (i) From the cessation of eye movements to the beginning of intercostal muscle paralysis

     (ii) Laryngeal reflex is lost, although inflammation of the upper respiratory tract increases reflex irritability.

     (iii) Corneal reflex disappears

     (iv) Tear secretion increases

     (v) Respiration is automatic and regular

     (vi) Movement and deep breathing as a response to skin stimulation disappear

   (c) Plane III—loss of muscle tone

     (i) From the beginning to the completion of intercostal muscle paralysis

     (ii) Diaphragmatic respiration persists, but there is progressive intercostal paralysis.

     (iii) Pupils are dilated and light reflex is abolished.

     (iv) The laryngeal reflex lost in plane II can still be initiated by painful stimuli. This was the desired plane for surgery when muscle relaxants were not used.

   (d) Plane IV—intercostal paralysis

     (i) From complete intercostal paralysis to diaphragmatic paralysis (apnea)

(5) Stage 4: Medullary paralysis

   (a) From the arrest of respiration until death

   (b) Anesthetic overdose causes medullary paralysis with respiratory arrest and vasomotor collapse.

   (c) Pupils are widely dilated and muscles are relaxed.

    b) Stage II is described as an excitement period with irregular breathing and possible agitation, laryngospasm, and regurgitation.

    c) Extubation should be performed only once Stage I is reached, that is, eyes have returned to a central position, breathing is regular, and consciousness returns.

  i) The main rationale is to keep the patient’s airway secure and protected during Stage II, with its risk of laryngospasm and vomiting.

1) Preparation for emergence

    a) Estimate remaining duration of surgical procedure; decrease concentration of inhaled anesthetic and/or rate of intravenous agent.

    b) Do not readminister muscle relaxants; give reversal medications.

    c) Titrate opioids to analgesia (estimate requirements based on procedure, patient’s weight, physiological status and opioid tolerance); if the patient is breathing spontaneously, the respiratory rate can be a useful indicator of adequate analgesia.

    d) Administer a 5-HT3 antagonist if indicated to prevent PONV.

    e) Administer 100% oxygen for 5 to 10 minutes, especially if N₂O used, to prevent hypoxemia.

  i) If N₂O has been used and the patient is allowed to breathe room air, diffusion hypoxia can occur. N₂O has a low blood:gas partition coefficient and will diffuse rapidly from the blood into the alveoli once administration is discontinued, resulting in the displacement of oxygen in the alveoli.

    f) Return patient to supine or back-up position prior to extubating. It is possible to extubate in the lateral or even prone position, but provisions should be made to be able to reposition the patient supine emergently if needed.

4) Extubation criteria (Table 4-1)

    a) Ensure that all the equipment to reintubate is available prior to extubating!

    b) Assess the potential for airway obstruction

  i) Especially in a patient who has received massive amounts of fluids and/or was positioned head down or prone, significant airway edema can develop and cause airway closure once the ETT is removed, which can result in a difficult or impossible reintubation.

  ii) Clinical inspection, possibly including direct laryngoscopy under GA to assess the feasibility of reintubation were the need to arise, should evaluate the degree of edema. Clinical judgment should be used to decide whether extubation should be delayed.

  iii) A leak test can be performed by deflating the ETT cuff (after pharyngeal suctioning) and assessing the presence of a leak around the ETT, indicating the absence of significant airway edema; the predictive value of this test is unclear.

    c) Suction pharynx; deflate ETT cuff and pull ETT; continue O₂ administration via nasal cannula or other appropriate device (e.g., face mask if nasal packing following sinus surgery).

    d) Reassess consciousness, ventilation, and comfort (pain, shivering).

5) Deep extubation

    a) Indications: Desire to avoid coughing, “bucking,” straining, cardiovascular response to the ETT, or bronchospasm in a patient at low risk for aspiration of gastric contents.

    b) Contraindications

  i) Full stomach, severe GERD, other situations where aspiration of gastric contents is a concern

  ii) Difficult intubation

  iii) Obesity, as the redundant pharyngeal tissue may make it very difficult to maintain a patent airway until muscle tone has returned. This is a relative contraindication.

    c) Uses: Can be used in cases such as an unclipped intracranial aneurysm, reactive airway disease, open-globe eye surgery (1)

    d) Technique

  i) The goal is to extubate the patient during Stage III (surgical anesthesia), not during Stage II.

  ii) Face mask

(1) The patient should not respond to stimulation and should be breathing spontaneously with a regular pattern.

(2) After oropharyngeal suctioning, the ETT cuff is deflated and the tube is removed.

(3) Ventilation is assisted as necessary via a facemask until the patient regains consciousness.

(4) An oral or nasal airway can be placed (2).

  iii) Laryngeal mask: “Bailey maneuver” (3) (Fig. 4-1)

(1) Following oropharyngeal suctioning, a laryngeal mask device is inserted behind the ETT and the cuff inflated.

(2) The ETT cuff is deflated and the tube removed. The laryngeal mask is left in place until the patient regains consciousness.

6) Postoperative considerations

    a) Respiratory failure

  i) Defined as the need to reintubate the trachea after extubation or the need for continued mechanical ventilation beyond 48 hours after the end of surgery

  ii) The most common causes are

(1) Hypoventilation due to Surgical swelling or hematoma causing airway obstruction, laryngospasm, bronchospasm, central apnea (opioid overdose, stroke), residual neuromuscular blockade.

(2) V/Q mismatch (aspiration of gastric contents, pulmonary edema, PE, atelectasis)

    b) Delayed emergence

  i) Residual drug effects: hypnotic or opioid overdose, reduced metabolism, potentiation by other drugs, residual neuromuscular blockade

  ii) Respiratory failure with significant hypercarbia

  iii) Metabolic derangements: hypoglycemia, severe hyperglycemia, electrolyte imbalance, hypothermia, central anticholinergic syndrome

  iv) Neurological complications: cerebral hypoxia, CVA [hemorrhage, embolism or thrombosis]

    c) Agitation and delirium

  i) Agitation upon awakening is not uncommon in children and young patients, especially when a balanced technique is used.

  ii) Patients are thrashing, crying, moaning, or incoherent.

  iii) Delirium usually resolves spontaneously within a few minutes.

  iv) Poor pain control may be implicated.

  v) Older patients can also experience emergence delirium, especially those who received anticholinergics that cross the blood–brain barrier, such as scopolamine.

  vi) Physostigmine (30 mg/kg) can be used to reverse anticholinergics.

  vii) Ketamine can cause hallucinations and delirium.

  viii) In one study, preoperative medication by benzodiazepines, breast surgery, abdominal surgery, and long duration of surgery increased the risk of delirium, while a previous history of illness and long-term treatment by antidepressants decreased the risk. Preoperative anxiety was not found to be a risk factor (4).

  ix) Hypoxia, severe hypercarbia, hypotension, hypoglycemia, increased intracranial pressure, as well as bladder distention can yield a similar clinical picture and should be excluded.

    d) Inadequate postoperative analgesia

  i) Besides the discomfort caused to the patient, postoperative pain can lead to severe complications such as myocardial ischemia and infarction.

  ii) Careful planning based on the patient’s weight and history of opioid use as well as the procedure performed allows adequate analgesia upon emergence in most cases; in some patients, however, more analgesics will be needed.

  iii) Regional analgesia as well as multimodal pharmacologic analgesia (acetaminophen, NSAIDs, gabapentin or pregabalin, etc.) can reduce the risk of inadequate postoperative analgesia.

  iv) Pain is subjective and should be treated, especially if the patient complains of severe pain (VAS>7), by titrating strong opioids until the VAS is <4.

    e) Hypothermia and shivering

  i) Postoperative hypothermia is best prevented by intraoperative active forced-air warming.

  ii) Hypothermia may lead to increased blood loss and transfusion requirements (because of platelet dysfunction) as well as poor wound healing and increased incidence of wound infection.

  iii) Shivering is a physiological response to hypothermia, using striated muscle contraction to produce heat. However, shivering is uncomfortable for the patient and can significantly increase oxygen consumption, leading to myocardial ischemia in susceptible patients.

  iv) Shivering can be treated with meperidine, 12.5 to 25 mg IV, and forced-air warming to correct hypothermia.

    f) PONV

  i) Prophylaxis should be used, depending on the patient’s risk factors.

  ii) Emptying the stomach with a gastric tube at the end of surgery, especially following ENT or oral surgery, where blood can be present in the stomach, also helps decrease the risk of PONV.

  iii) Treatment options include ondansetron (or another 5-HT3-antagonist), dopamine antagonists (metoclopramide, prochlorperazine, droperidol), and as a last resort a low-dose (0.1 mL/kg/h) propofol infusion (5).

References

1. Guedel AF. Inhalational Anesthesia. 2nd ed. New York, NY: The Macmillan Co., 1951:10–52.

2. Daley MD, Norman PH, Coveler LA. Tracheal extubation of adult surgical patients while deeply anesthetized: a survey of United States anesthesiologists. J Clin Anesth 1999;11(6):445–452.

3. Nair I, Bailey PM. Use of the laryngeal mask for airway maintenance following extubation. Anaesthesia 1995;50(2):174–175.

4. Lepousé C, Lautner CA, Liu L, et al. Emergence delirium in adults in the post-anaesthesia care unit. Br J Anaesth 2006;96(6):747–753.

5. Ewalenko P, Janny S, Dejonckheere M, et al. Antiemetic effect of subhypnotic doses of propofol after thyroidectomy. Br J Anaesth 1996;77(4):463–467.

Positioning of the Surgical Patient

Anastassia Grigorieva, MD • Jamie Murphy, MD

1) Overview

    a) Proper positioning of the surgical patient requires a careful balance of optimal surgical field exposure without subjecting the patient to inappropriate positioning.

    b) Each surgical position (supine, prone, lithotomy, and lateral) presents its own unique risks and challenges.

    c) Knowledge of potential positioning complications and their timely recognition and management are critically important for a successful outcome of any surgical procedure.

2) Factors affecting positioning (Table 5-1)

    a) Complications arising from patient malpositioning during surgery depend on both non-patient and patient factors.

    b) While most of these factors (e.g., type of procedure, patient’s age or gender) cannot be modified, recognition of patients who are at additional risk for positioning complications should alert the anesthesia provider to take extra precautions.

    c) These patients are typically 70 years of age or older; morbidly obese (BMI of > 40); thin, small in stature, have a poor preoperative nutritional status; or a history of diabetes or vascular disease.

1) General positioning guidelines (1–4)

    a) Proper patient positioning balances the need for adequate exposure of the surgical field and prevention of positioning injury.

    b) Optimal positioning is achieved when:

  i) Adequate arterial supply and venous outflow are maintained to all body parts

  ii) Nerves are protected from undue pressure or stretching

  iii) Bony prominences are padded

  iv) Circulatory and respiratory systems are minimally compromised

  v) Maximum surgical field exposure is achieved

4) Positioning guidelines

    a) Supine

  i) Used for abdominal, pelvic, open-heart, head and neck, and most extremity surgery.

  ii) Padding should be applied to the heels, elbows, knees, spinal column, and occiput.

  iii) To avoid pressure alopecia, periodically rotate the patient’s head, especially during prolonged cases.

  iv) To avoid brachial plexus injury, upper extremities should be abducted to <90 degrees with hands and forearms in a supinated or neutral position.

  vi) IV tubing and stopcocks touching the skin should be padded.

  vii) For the Trendelenburg position, a nonsliding mattress is recommended to prevent patients from sliding cephalad.

(1) The Trendelenburg position may cause cardiovascular and/or respiratory compromise.

(2) Patients may develop significant edema of the face and upper airway.

    b) Prone (Fig. 5-1)

Figure 5-1 The Classic Prone Position

A: Flat table with relaxed arms extended alongside patient’s head. Parallel chest rolls extended from just caudad of clavicle to just beyond inguinal area, with pillow over pelvic end. elbows and knees are padded, and legs are bent at the knees. head is turned onto a C-shaped foam sponge that frees the down-side eye and ear from compression. B: Same posture with arms snugly retained alongside torso. C: Table flexed to reduce lumbar lordosis; subgluteal area straps placed after the legs are lowered to provide cephalad thrust and prevent caudad slippage. Reproduced from Warner MA. Patient positioning and related injuries. In: Barash PG, ed. Clinical anesthesia. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:793–814, with permission.

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