Neuromuscular blockers

Question 1

Discuss the two assessments that should be addressed prior to administration of a neuromuscular blocking agent (NMBA).

Answer 1

1. Assess endotracheal tube (ET) placement**
2. Patient must have adequate sedation AND analgesia prior to initiation of a Neuromuscular Blocking Agent (NMBA)***

—>Continuous Intravenous (IV) sedative*
Must have amnestic properties and a deeper level of sedation

—>Continuous IV analgesic*
Morphine, Fentanyl

Question 2

Succinylcholine (one dose hyperkalemia)

ADR

Answer 2

Hyperkalemia***

Question 3

Aminosteroidal vs. Benzylisoquinolinium

Answer 3

Aminosteroidal not recommended with  dose corticosteroids (i.e. ≥1 gram methylprednisolone

Question 4

Pancuronium

Answer 4

(~90% of patients) vagolytic effect (transient) Increase: HR, BP, CO

Patient with cardiovascular disease will not tolerate

Question 5

Vecuronium

Answer 5

Metabolism and eliminated: Renally and hepatically eliminated – Never use with renal or hepatic insufficiency

Question 6

Cisatracurium

Answer 6

Preferred in critically ill patients with organ dysfunction

Bolus does – do not worry about renal inssuficnecy

Question 7

Rocuronium

Answer 7

Onset: 3 minutes

Duration of blockade mildly affected by renal or hepatic impairment

Question 8

Factors altering effects of NMBA: Potentiating Block

Answer 8

Antibiotics
Aminoglycosides, clindamycin, amphotericin B

Cardiovascular agents
Calcium channel blockers, furosemide, β-blockers, lidocaine, procainamide, quinidine

Corticosteroids –IV and PO only

Myasthenia gravis

The interactions are NOT contraindicated when using a NMBA but should be considered when initiating/ adjusting therapy

Question 9

Factors altering effects of NMBA: Antagonize Block

Answer 9

Phenytoin

Pregnancy

Burns

The interactions are NOT contraindicated when using a NMBA but should be considered when initiating/ adjusting therapy

Question 10

Recovery from paralysis

Answer 10

occurs in the reverse order—when you see the patients blinking, the patient has drug out of the system

Question 11

Paralysis occurs sequentially

Answer 11

Smaller, fast twitch muscles
i.e. eyes and larynx

Limbs
Neck
Trunk
Upper airway

Intercostals and diaphragm
Until respirations

Question 12

Monitoring of NMBA: Clinical exam

Answer 12

Visual, tactile assessment of patients’ muscle tone
Observation of skeletal muscle and respiratory efforts

Monitoring allows for lowest effective NMBA dose

Minimizes adverse effects or prolonged muscle weakness

Signs and symptoms suggesting inadequate sedation and analgesia (increased–> HR, BP, sweating

Question 13

Monitoring of NMBA: TOF

Answer 13

Two small conductive pads are applied at the wrist to deliver a series of four mild electric stimuli

Monitor q4hours to avoid muscle weakness
Mark anatomic sites: Facial nerve and Ulnar nerve

Responses: Out of 4 Twitches
Responses		Percentage of block
 4					0-75%
 3					75-80%
 2					80-90%
 1					90%
 0					100%

1/4 to 2/4 – Requires no change with infusion rate Response

Troubleshooting:
Weak batteries
Unsecured lead wire attachments
Peripheral or periorbital edema
Diaphoresis
Incorrect positioning
Directly stimulating orbicularis oculi

Question 14

Reversal of Neuromuscular Blockade

Answer 14

Neostigmine
After surgery
Dose: 0.5- 2.5 mg IV
–>Give with atropine or glycopyrolate to prevent adverse effects

Question 15

Neostigmine-IV only

Mechanism of action: anti-acetylcholinesterase agent

AE

Answer 15

Adverse effects
Bradycardia*
Salivation
Bronchoconstriction
Confusion

Question 16

Adverse Effects of NMBAs

Answer 16

Slowed gastric motility – on phentyl or morphine drip

increase risk of VTE
May mask seizure activity
may mask proper sedation/analgesia
skin break down
corneal abrasiaon

Question 17

Continuous Infusion NMBA Interventions

Answer 17

Airway/breathing
Proper endotracheal tube (ET) placement
Ventilator alarms set

Sedation and analgesia

• Continuous administration of sedation and analgesia
• -Sedative with amnestic properties
• —>Benzodiazepine (lorazepam, midazolam), propofol

Assess for pain
Neuro-exam (per unit practice)

Immobility
 Skin breakdown prevention
-Eye care
--->Ocular lubricants
-Specialty bed consult
-Turn/positions

DVT prophylaxis

• Enoxaparin
• Heparin
• Mechanical prophylaxis

Stress Ulcer prophylaxis

• H2 blockers
• PPI

Foot drop boots/ Multi-podus boots
Wrist splints
Physical Therapy

Family education
Nutrition
+/- Laxatives/ Stimulants

Question 18

Discuss the appropriate indications for neuromuscular blocking agents.

Answer 18

Short-term Indications

Facilitate short-term procedures
Endotracheal intubations

Long-term Indications

Improve ventilator synchrony to enhance oxygenation
Prevent interference with surgical repair
Increased intracranial pressure
Therapeutic hypothermia after cardiac arrest
Prevent shivering

When all other means have been tried without success
-Used for intubated patients with persistent hypoxia despite ADEQUATE sedation and analgesia
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Question 19

Depolarizing agents
Succinylcholine

IV bolus only

Answer 19

Onset of action and duration: onset within 60 seconds and lasts 3-6 minutes –FASTEST***

Metabolized in the blood; Not metabolized renally or hepatically

Adverse effects: Hyperkalemia***, bradycardia, increase intracranial pressure, malignant hyperthermia

Question 20

Depolarizing agents
Succinylcholine
IV bolus only
MOA

Answer 20

Competitively inhibits the ACh receptor on the motor endplate

The drug binding to the receptor prevents the change in the receptor so the endplate potential is not generated

The nerve impulse stops

An action potential in the muscle cell fails to occur and the muscle fibers cannot contract

Aminosteroidal vs. Benzylisoquinolinium
Aminosteroidal not recommended with increase dose corticosteroids (i.e. ≥1 gram methylprednisolone)

Question 21

Pancuronium

IV bolus only
Onset: 3 – 5 minutes
Duration: Long-acting 90-100 minutes

Active metabolite: 3-hydroxypancuronium

Answer 21

Active metabolite: 3-hydroxypancuronium

Adverse effects:
(~90% of patients) vagolytic effect (transient HR) BP,  cardiac output
–Patient with cardiovascular disease will not tolerate

Skeletal muscle weakness, polyneuropathy, myopathy
—Can occur with all continuous infusion neuromuscular blockers

Question 22

Vecuronium
IV bolus and Continous infusion

Active metabolite: 3-desacetylvecuronium

Adverse effects:
Minimal cardiovascular effects
Skeletal muscle weakness, polyneuropathy, myopathy
Prolonged paralysis in renal and liver impairment

Whats the Onset, Duration of action, Motablism

Answer 22

Onset: 1- 2 minutes (2nd Fastest)

Duration: Intermediate acting 35- 40 minutes

Metabolism and eliminated: Renally and hepatically eliminated – Never use with renal or hepatic insufficiency.

Question 23

Cisatracurium

IV bolus and continuous infusion

Onset: 3- 5 minutes
Duration: 45- 60 minutes

How is this metabolized?

Answer 23

Metabolized by ester hydrolysis and Hofmann elimination

Adverse effects:
Duration of blockade not affected by renal or hepatic impairment - NOT Renally ELIMATED

Preferred in critically ill patients with organ dysfunction
Bolus does – do not worry about renal inssuficnecy.

Question 24

Rocuronium
IV bolus and continous infusion
Onset:  3 minutes 
Duration:  30- 60 minutes
Mildly hepatically metabolized

Answer 24

Adverse effects:
Duration of blockade mildly affected by renal or hepatic impairment

Skeletal muscle weakness, polyneuropathy, myopathy