3.3 Intraoperative Anesthesia Support, Airway Management & Physiological Monitoring

3.3 Intraoperative Anesthesia Support, Airway Management & Physiological Monitoring

The perioperative nurse plays a critical role in supporting the anesthesia provider during induction, maintenance, and emergence from anesthesia. Maintaining physiological homeostasis, assisting with airway emergencies, and recognizing lethal metabolic crises—such as Malignant Hyperthermia (MH) and Local Anesthetic Systemic Toxicity (LAST)—are vital intraoperative nursing competencies tested on the CNOR exam.

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1. Anesthesia Continuum & Induction Support

Anesthesia spans a continuum from minimal sedation to general anesthesia. During General Anesthesia, the patient loses consciousness, protective airway reflexes, and spontaneous ventilatory drive.

Phases of General Anesthesia & RN Roles

1. Induction: Transition from awake state to unconsciousness. The circulating nurse must stand at the head of the bed assisting the anesthesia provider during airway securing.
2. Maintenance: Sustained unconsciousness using volatile inhalation agents (e.g., sevoflurane, desflurane) or Total Intravenous Anesthesia (TIVA, e.g., propofol infusion).
3. Emergence: Extubation and return of protective reflexes. The circulating nurse must ensure suction equipment, 100% O2, and emergency airway supplies are immediately accessible.

Rapid Sequence Induction (RSI) & Cricoid Pressure

Rapid Sequence Induction (RSI) is indicated for patients at high risk for regurgitation and pulmonary aspiration (e.g., full stomach, emergency trauma, severe GERD, acute bowel obstruction, morbid obesity, or pregnancy >20 weeks).

   [ Unconscious Patient (RSI Induction) ]
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   [ Application of Cricoid Pressure (Sellick) ] ➔ (10 N awake -> 30 N unconscious)
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   [ Endotracheal Intubation (ETT Placement) ]
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   [ ETT Cuff Inflation & ETCO2 Confirmation ]
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   [ Release of Cricoid Pressure ]

• Sellick Maneuver (Cricoid Pressure): Downward compression applied to the cricoid cartilage (the only complete cartilaginous ring surrounding the trachea) to occlude the underlying esophagus against the 5th and 6th cervical vertebrae.
• Force Protocol: Apply 10 Newtons (N) of downward force while the patient is awake, increasing to 30 Newtons once loss of consciousness occurs.
• Critical Nursing Rule: Cricoid pressure must be maintained continuously without release until the endotracheal tube cuff is fully inflated and correct placement is confirmed via capnography. If active vomiting occurs, pressure must be released immediately to prevent esophageal rupture!
• Gold Standard Verification: Continuous End-Tidal Carbon Dioxide (ETCO2) capnography displaying a sustained 4-phase waveform is the gold standard for confirming ETT placement, supplemented by bilateral breath sounds and absent gastric insufflation.

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2. ASA Physiological Monitoring Standards

The American Society of Anesthesiologists (ASA) mandates continuous physiological monitoring for all patients undergoing general, regional, or monitored anesthesia care (MAC):

• Electrocardiogram (ECG): Continuous monitoring of heart rate and rhythm.
• Non-Invasive Blood Pressure (NIBP): Measured and documented at least every 5 minutes.
• Pulse Oximetry ($SpO_2$): Continuous pulse oximetry with audible pitch variation.
• Capnography ($ETCO_2$): Mandatory for all intubated patients and deep sedation cases.
• Core Body Temperature: Mandatory for procedures exceeding 30 minutes or conducted under general anesthesia. Hypothermia ($<36.0^\circ\text{C}$ or $96.8^\circ\text{F}$) increases wound infection rates, impairs coagulation, and delays drug clearance.

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3. Malignant Hyperthermia (MH) Management

Malignant Hyperthermia (MH) is a life-threatening pharmacogenetic skeletal muscle receptor disorder inherited as an autosomal dominant trait. It is triggered by exposure to volatile inhalational anesthetics (sevoflurane, desflurane, isoflurane) or the depolarizing muscle relaxant succinylcholine.

Pathophysiology & Clinical Manifestations

A mutation in the ryanodine receptor (RYR1) leads to uncontrolled calcium release from the sarcoplasmic reticulum into the skeletal muscle cytoplasm. This induces sustained muscle contractions, massive hypermetabolism, ATP depletion, excessive carbon dioxide production, and cell lysis.

Emergency MH Treatment Protocol

[ 1. CALL FOR HELP & MH CART ] ➔ [ 2. STOP TRIGGERING AGENTS & HYPERVENTILATE (100% O2 @ 10+ L/min) ]
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[ 3. ADMINISTER DANTROLENE SODIUM (2.5 mg/kg IV Rapid Push) ]
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[ 4. ACTIVE COOLING & RECONSTITUTION (Sterile Water WITHOUT Preservatives) ]
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[ 5. TREAT HYPERKALEMIA & MAINTAIN URINE OUTPUT (>2 mL/kg/hr) ]

1. Discontinue Triggers & Call for Help: Stop volatile agents and succinylcholine immediately. Notify surgeon to halt procedure. Call MHAUS hotline (1-800-684-9328). Hyperventilate with 100% $O_2$ at 10+ L/min through clean circuit.
2. Administer Dantrolene Sodium: The specific antidote. Administer 2.5 mg/kg IV rapid bolus, repeated every 5–10 minutes until symptoms subside (up to 10 mg/kg total).
   • Ryanodex (Dantrolene formulation): $250\text{ mg/vial}$, reconstituted with $5\text{ mL}$ of sterile water.
   • Traditional Dantrolene (Dantrium/Revonto): $20\text{ mg/vial}$, reconstituted with $60\text{ mL}$ of sterile water.
3. Reconstitution Rule: Reconstitute Dantrolene EXCLUSIVELY with Sterile Water for Injection WITHOUT bacteriostatic agents. Never use Normal Saline ($0.9%\text{ NaCl}$) or $D_5W$, as they cause drug precipitation.
4. Active Cooling: Administer cold IV normal saline ($4^\circ\text{C}$); apply ice packs to groin, axilla, and neck; perform cold gastric/peritoneal lavage. Stop cooling when core temperature drops to $38.5^\circ\text{C}$ ($101.3^\circ\text{F}$) to prevent rebound hypothermia.
5. Laboratory & Renal Management: Treat hyperkalemia ($IV\text{ Insulin} + D_{50}W$, Sodium Bicarbonate, Calcium Chloride). Administer mannitol/furosemide to maintain urine output $>2\text{ mL/kg/hr}$ to prevent renal tubular damage from myoglobinuria.

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4. Local Anesthetic Systemic Toxicity (LAST)

LAST is a life-threatening adverse event caused by accidental intravascular injection or rapid systemic absorption of local anesthetics (e.g., bupivacaine, ropivacaine, lidocaine).

• CNS Toxicity (Initial): Metallic taste in mouth, circumoral numbness, tinnitus, visual disturbances, tremors, seizures.
• Cardiovascular Toxicity (Progressive): Bradycardia, conduction blocks, severe hypotension, ventricular dysrhythmias, and refractory cardiac arrest.
• Antidote / Treatment: Immediately administer 20% Lipid Emulsion Therapy (Intralipid):
  • Initial bolus: 1.5 mL/kg IV over 1 minute.
  • Continuous infusion: 0.25 mL/kg/min.
  • Propofol and vasopressin should be avoided or minimized during resuscitation.

[!TIP] CNOR Exam Key Distinction: Remember that Hypercarbia ($ETCO_2$ elevation) is the earliest indicator of MH, whereas Hyperthermia is a late manifestation. Dantrolene works by inhibiting calcium release from the ryanodine receptor.