Anesthesia Principles & Patient Safety (LAST, Regional, General)

This category covers the core concepts of various anesthesia types, their mechanisms, and critical safety measures, particularly Local Anesthetic Systemic Toxicity (LAST).

Local Anesthetic Systemic Toxicity (LAST)

LAST is a critical, potentially life-threatening complication arising from the systemic absorption of local anesthetics.

The Three Phases of LAST

1. Initial Phase (Warning Signs): This phase is typically observed when local anesthetics accumulate rapidly (e.g., from “stacking” multiple injections). It signifies early central nervous system (CNS) excitation.
   • Perceptual Disturbances: A metallic taste, numbness or tingling around the mouth (tongue and lips), ringing in the ears.
   • Mild CNS Alterations: Feelings of lightheadedness, agitation, or a general sense of unease (“I don’t feel right”).
2. Excitation Phase (Intensified CNS Effects): As local anesthetic levels rise further, more pronounced CNS excitation occurs, potentially leading to seizures.
   • Speech and Cognitive Impairment: Slurred speech, confusion (resembling intoxication).
   • Motor Activity: Shivering, muscle twitching, which can progress to full-blown seizures.
   • Cardiovascular Signs: Often accompanied by tachycardia (rapid heart rate) and hypertension (high blood pressure) due to sympathetic nervous system activation.
   • Note: This phase can be particularly rapid and severe with direct intravenous injections, such as during Bier Blocks or unintended intravascular injection during a nerve block.
3. Depression Phase (CNS and Cardiovascular Collapse): This is the most severe phase, characterized by profound CNS and cardiovascular depression.
   • Loss of Consciousness: The patient becomes comatose.
   • Cardiovascular Depression: Bradycardia (slow heart rate) and hypotension (low blood pressure) due to direct effects on cardiac nodal tissue.
   • Cardiac Arrhythmias: Can progress to ventricular arrhythmias.
   • Respiratory and Cardiac Arrest: Ultimately, complete shutdown of respiratory and cardiac function.

Preventing LAST: Maximum Dose of Lidocaine

• Crucial Calculation: To prevent LAST, the maximum safe dose of 1% Lidocaine is 5 mg/kg/day.
• Protocol: Before administering additional local anesthetic to the surgical field, you must ascertain the amount the patient received pre-operatively. Subtract this amount from the 5 mg/kg/day maximum to determine the remaining safe dose for intraoperative use. Never exceed this remaining amount.

Strategies to Mitigate LAST Risk

1. Dose Calculation: Precisely calculate and adhere to the maximum safe dose of local anesthetic for each patient.
2. Aspiration: Always aspirate prior to injection to ensure the needle tip is not in a blood vessel (a nerve is typically positioned above a vessel). Seeing nothing on aspiration is the desired outcome.
3. Symptom Monitoring: Actively inquire about patient symptoms after each injection, and encourage patients to self-monitor and report any unusual sensations promptly.
4. Close Observation: Maintain vigilant monitoring, especially during serial repairs of large or multiple wounds, where cumulative dosing can rapidly increase risk.

Management of LAST (Treatment Protocol)

1. Stop the Injection: Immediately cease administration of the local anesthetic.
2. Call for Assistance: Initiate an emergency response and call for help.
3. Oxygenation and Ventilation: Provide 100% oxygen and assist ventilation as needed.
4. Secure IV Access: Ensure reliable intravenous access.
5. Seizure Control: Administer appropriate medications (e.g., benzodiazepines) to control seizures.
6. ACLS Protocol: Initiate Advanced Cardiovascular Life Support (ACLS) guidelines for cardiac events.
7. Lipid Emulsion Therapy (Antidote): Administer 20% Lipid Emulsion immediately.
   • Initial Bolus: 1-1.5 mL/kg given intravenously over 1 minute.
   • Repeat Bolus: Can be repeated up to 3 times.
   • Continuous Infusion: Follow with a continuous infusion of 0.25 mL/kg/min.
   • Mechanism: Lipid emulsion acts as a reversal agent by creating a “lipid sink” that sequesters and “engulfs” both amide and ester local anesthetics, reducing their concentration at target organs.
   • Duration: Continue administration until symptoms resolve.

Regional Anesthesia Techniques

Regional anesthesia involves blocking sensation in a specific body area without inducing general unconsciousness.

Types of Regional Anesthesia

• Topical Anesthesia: Applied directly to surfaces (e.g., drops for eyes, ointments).
• Local Infiltration: Direct injection of medication into the surgical site.
  • Maximum Dose: The maximum daily dose for 1% Lidocaine is 5 mg/kg.
• Regional Nerve Blockade: Injection of an amide or ester local anesthetic onto or near specific nerves to achieve temporary pain control (e.g., for extremities, eyes like a retrobulbar block).

Role of Epinephrine in Local Injections

• Primary Purpose: Epinephrine is added to local anesthetic solutions to prolong their duration of action and enhance postoperative pain control.
• Mechanism: It achieves this by causing vasoconstriction at the injection site, which delays the systemic absorption of the local anesthetic. Its role is not solely for bleeding control.

Brachial Plexus Blocks (Regional Anesthesia for Upper Extremity)

• Shoulder Surgery: An Interscalene Brachial Plexus Block (at the neck) is commonly performed.
• Four Locations for Brachial Plexus Blocks:
  1. Interscalene: At the neck, primarily for shoulder surgery.
  2. Supraclavicular: Above the clavicle, targeting the first three fingers and thumb.
  3. Infraclavicular: At the anterior shoulder, targeting the palm of the hand (e.g., for Dupuytren’s contracture release).
  4. Axillary: In the armpit or mid-arm, for procedures on the hand (e.g., Carpal Tunnel Release – CTR).

Complications of Brachial Plexus Blocks

• Interscalene Specific Complications:
  • Horner’s Syndrome: Occurs on the same side as the block, characterized by miosis (constricted pupil), ptosis (drooping eyelid), anhidrosis (absence of sweating), and a hoarse voice. It’s crucial for nurses to recognize this as a side effect of the block, not a stroke.
  • Phrenic Nerve Paresis: A common side effect where the phrenic nerve’s function is decreased (not complete paralysis). This indicates the block worked effectively. The patient may report feeling unable to take a deep breath or fully expand their ribs on the affected side, as the diaphragm is partially affected.
• Complications Across All Brachial Plexus Block Locations:
  • Supraclavicular:
    • Pneumothorax: Risk due to proximity to the lungs.
    • Phrenic nerve paresis (less common than with interscalene).
  • Infraclavicular: No highly specific severe complications; provides good pain control with shorter duration.
  • Axillary:
    • Hematoma: Can be difficult to apply sustained pressure in the axilla.
    • Accidental Vascular Injection: Increased risk, necessitating ultrasound guidance for accuracy.
    • High Risk for LAST: This site is prone to LAST due to rich vascularity, similar to epidurals.

Bier Block (Intravenous Regional Anesthesia)

A Bier block is a technique for short-duration extremity anesthesia.

Type of Anesthesia

• Intravenous (IV) Regional Anesthesia.

Tourniquet Utilization During a Bier Block

• Double Tourniquet System:
  1. Exsanguinate the Limb: Use an Esmarch bandage to remove blood from the limb.
  2. Inflate Proximal Cuff: Inflate the upper (proximal) tourniquet cuff.
  3. Inject Lidocaine: Administer Lidocaine intravenously into the limb.
  4. Inflate Distal Cuff: Inflate the lower (distal) tourniquet cuff.
  5. Deflate Proximal Cuff: Once the distal area is numb, deflate the upper (proximal) cuff. This transfers the pressure to the distal cuff, which is now on a desensitized area.
• Sequence: Proximal cuff UP → Distal cuff UP → Proximal cuff DOWN → Distal cuff DOWN.
• Scenario Anticipation: Be prepared for questions mid-scenario, e.g., if the proximal cuff is inflated and the patient experiences pain, the next step is to inflate the distal cuff.
• Minimum Occlusion Time: The limb must remain occluded for a minimum of 15 minutes after injection to prevent premature release of the local anesthetic into systemic circulation, which could cause LAST.

Post-Bier Block Mobility

• Patients can drive home after a Bier Block if no sedation was administered.
• Motor function recovers rapidly, while sensation typically returns within 1-2 hours.

Uses of Bier Blocks

• Ideal for hand procedures (e.g., Carpal Tunnel Release – CTR).
• Best for cases lasting 20-60 minutes (up to 1.5 hours).
• Rapid onset (<5 minutes).

Femoral Blocks

Use of Femoral Blocks

• Primarily for procedures involving the thigh and knee, such as femur fracture repair or quadriceps tendon repair.

Neuraxial Anesthesia (Epidural and Spinal)

Neuraxial anesthesia involves medication administration directly into the spinal canal.

Definition of Neuraxial Anesthesia

• Anesthesia administered directly on the spinal cord or its immediate surrounding spaces. This includes Epidurals and Spinals, involving amides and esters.

Most Common Injection Site for LAST

• Epidurals are the most common site for LAST, followed by Axillary Brachial Plexus Blocks.
• Crucial Rule: Always aspirate first! You should see nothing (no blood or CSF) on aspiration before injection.

Concerns with Neuraxial Anesthesia (Epidurals/Spinals)

1. Aspiration: Always aspirate before injection; no fluid should be seen.
2. Loss of Tone: Leads to loss of vascular tone, autonomic nervous system control, and compensatory vasoconstriction.
3. Careful Positioning/Transfer: Patients must be positioned and transferred with extreme care to maintain spinal alignment.
4. Slow Movements: Move patients slowly to prevent severe hypotension due to sympathetic blockade.

Anatomic Location Differences

• Peridural / Epidural / Caudal: Medication injected into the epidural space (the space superficial to the dura mater, before the spinal cord itself).
  • A pencil-point needle (non-beveled) is preferred to minimize the risk of puncturing the dura.
• Subdural / Spinal / Saddle: Medication injected directly into the spinal fluid (Cerebrospinal Fluid – CSF).

Epidural vs. Spinal Differences

Feature	Epidural	Spinal
Medication Location	Epidural space	Cerebrospinal Fluid (CSF)
Injection Site	Thoracic & Lumbar regions	Below L2 (lumbar region)
Duration of Effect	Longer duration; can be used for post-op pain via continuous pump	Shorter duration (approx. 2 hours for surgery); NOT for post-op pain; single injection
Dose	Larger dose	Smaller dose
Aspiration	Always aspirate! (should see nothing)	DO NOT aspirate CSF (unless for diagnostic purposes)
Onset of Action	15-30 minutes	~5 minutes

Why Spinals are Faster Onset than Epidurals

• Medication is sprayed directly onto the spinal cord, leading to rapid onset of action.

Considerations for Neuraxial Anesthesia

• Spinal Malformations: Assess history of conditions like spina bifida.
• Prior Spinal Surgery: Scar tissue can make insertion difficult.
• Psychological Status: Can the patient remain still and cooperate?
• Pediatric Specialists: Pediatric anesthesiologists are recommended for infants and children.

Contraindications for Neuraxial Anesthesia (6 Key Areas)

1. Anticoagulation/Bleeding Disorders: High risk of hematoma formation.
2. Increased Intracranial Pressure (ICP): Adding fluid to the spinal space can exacerbate ICP.
3. Sepsis: Risk of introducing infection into the CNS, leading to meningitis.
4. Skin Infection at Insertion Site: Increased risk of infection.
5. Pre-existing Neurological Disorders (e.g., MS): Can potentially worsen or accelerate disease progression.
6. Brain or Spinal Cord Cancer: Generally avoided.
7. Patient Refusal.

Complications of Neuraxial Anesthesia

1. Respiratory Depression: Can be caused by sedatives (e.g., Versed) or high placement of the block affecting the phrenic nerve (diaphragm), leading to difficulty taking deep breaths.
2. Bladder Distension: Sacral fibers are the last to recover. The sensation to void returns after motor function. If a full bladder is palpated, always offer a bedpan first.
3. Hypotension: Occurs in about one-third of patients due to vasodilation during induction (vascular changes cause smooth muscle relaxation, not always vasodilation in general). Closely monitor CHF and dehydrated patients.
4. Post-Dural Puncture Headache (PDPH): Occurs when CSF leaks from the puncture site, causing the brain to “sag.”
   • Non-Invasive Treatment: Keep HOB flat (to slow CSF loss), give fluids, analgesics, caffeine, and Sumatriptan (a migraine medication).
   • Invasive Treatment: In severe cases, an epidural blood patch (injecting venous blood directly at the puncture site) is performed to seal the leak.

Airway and Anesthesia Complications

Laryngospasms

• Causes: Secretions on the vocal cords, trauma, or swelling.
• Prevention: Suction before and after extubation. Encourage coughing.
• Treatment for Complete Spasm: Sedate and paralyze the patient to facilitate reintubation.

Emergence Delirium

• Management:
  • Place a hand on the patient’s shoulder to provide reassurance.
  • Attempt to talk to them and calm them down.
  • Avoid physically restraining them too aggressively.
• Demographics: More common in adolescents and males.

Anesthesia Stages and Goals

• Surgical Stage: Surgery is performed in Stage 3, Plane 3 of anesthesia.
• Goals of General Anesthesia Induction:
  • Rapid onset, short-acting hypnotic (e.g., Propofol, Etomidate).
  • Loss of laryngeal reflexes.
  • Reaching Stage 3 for surgical readiness.
  • Note: Induction agents typically do not provide analgesia.
• Highest Risk Stage:Stage 2 (Excitation Stage) poses the greatest risk.
  • Risks include laryngospasm and myocardial infarction (MI).
  • Environment: Minimize sensory stimulation (be quiet) during this stage.

Stages of Anesthesia (Four Stages)

1. Stage 1 (Analgesia/Amnesia): Drowsy, able to follow commands.
2. Stage 2 (Excitement/Delirium): Excitation, rapid eye movements. Highest risk for MI.
3. Stage 3 (Surgical Anesthesia): Surgical stage; patient cannot protect their airway.
4. Stage 4 (Medullary Depression/Overdose): Irregular respirations, paralysis; indicates overdose.

Succinylcholine vs. Rocuronium for Induction

• Succinylcholine:
  • Advantages: Faster onset, shorter duration.
  • Disadvantages: Depolarizing (can cause hyperkalemia and arrhythmias); contraindicated in patients with muscular dystrophy.
• Rocuronium:
  • Advantages: Slower onset, longer duration, does not cause fasciculations, has a reversal agent, and fewer side effects.

RN Monitoring and Anesthesia

Aldrete Score

• Purpose: Determines a patient’s readiness for discharge from PACU (Post-Anesthesia Care Unit).
• Parameters: Assesses Activity, Breathing, Circulation, Consciousness, and SpO2.
• Scoring: A perfect score is 10. A score of 9 is typically required for home discharge.

Differences: Local vs. Moderate Sedation

• Moderate Sedation: Involves IV access (and usually includes some systemic sedation, local anesthesia, and/or pain medications).
• Local Anesthesia: Does NOT involve IV access or systemic sedation.
• Airway Protection: In both cases, the patient is expected to protect their own airway.

Forms of Anesthesia an RN Can Monitor

• Local Anesthesia
• Moderate Sedation (with IV access)
• Conditions for RN Monitoring: The patient must be classified as ASA Class I, II, or III.

Monitored Anesthesia Care (MAC) vs. Moderate Sedation

• MAC (or TIVA – Total Intravenous Anesthesia): Typically involves Propofol and the patient may or may not protect their own airway. An LMA (Laryngeal Mask Airway) may be used.

ASA Scores for RN Monitoring

• Types of Anesthesia: RNs can monitor patients undergoing Local Anesthesia and Moderate Sedation (with IV). In both cases, the patient must protect their own airway.
• Acceptable ASA Scores for RN Monitoring: ASA Class I, II, and III.
  • ASA 1: Healthy patient, no underlying medical conditions.
  • ASA 2: Mild systemic disease not related to the primary disease process (e.g., controlled hypertension, smoker, pregnant).
  • ASA 3: Severe systemic disease with related health issues (e.g., diabetic with peripheral neuropathy, chronic wounds, cataracts related to diabetes).

“E” Indication in ASA Score

• The “E” denotes an emergent procedure.
• It can be appended to any ASA class from 1 to 5 (e.g., ASA 1E = a healthy patient involved in a car accident).
• Note: There is never an “E” after ASA 6 (brain dead/organ harvest).

Differences Between ASA Class 4-6

ASA 6: A brain-dead patient whose organs are being harvested.

ASA 4: Severe systemic disease that poses a constant threat to life and requires regular medical intervention to survive.

This is a Class 3 patient who requires continuous management. Often referred to as “Frequent Flyer Four.”

Example: A renal failure patient on regular dialysis.

ASA 5: A near-death patient not expected to survive without immediate hospital intervention.

Example: A severe trauma patient with hemorrhage, in the ICU on a ventilator and ECMO.