General and Local Anesthetic Agents: Nursing Pharmacology

Anesthetics: Generic and Brand Names

• General Anesthetic Agents
  • Barbiturate Anesthetics
    • methohexital (Brevital)
    • thiopental (Pentothal)
  • Nonbarbiturate General Anesthetics
    • droperidol (Inapsine)
    • etomidate (Amidate)
    • fospropofol (Lusedra)
    • ketamine (Ketalar)
    • midazolam
    • propofol (Diprivan)
  • Anesthetic Gases
    • nitrous oxide (blue)
  • Volatile Liquids
    • desflurane (Suprane)
    • enflurane (Ethrane)
    • halothane (Fluothane)
    • isoflurane
    • sevoflurane (Ultane)
• Local Anesthetic Agents
  • Esters
    • benzocaine (Dermoplast, Lanacane)
    • chloroprocaine (Nesacaine)
    • procaine (Novocaine)
    • tetracaine (Pontocaine)
  • Amides
    • bupivacaine (Marcaine, Sensorcaine)
    • dibucaine (Nupercainal)
    • lidocaine (Dilocaine, Xylocaine, Solarcaine, Lidoderm, Octocaine)
    • mepivacaine (Carbocaine, Isocaine, Polocaine)
    • prilocaine (Citanest)
    • ropivacaine (Naropin)
  • Others
    • pramoxine (Tronothane, PrameGel, Itch-X)

General and Local Anesthesia

General Anesthesia

General anesthesia combines agents to achieve analgesia (loss of pain perception), unconsciousness (loss of awareness of surroundings), and amnesia (inability to recall what took place), with the fewest adverse effects. It blocks the autonomic reflexes that drive the body's involuntary response to injury, which can compromise cardiac, respiratory, gastrointestinal, and immune status. It also blocks muscle reflexes to prevent jerking movements that would interfere with surgery.

Risk factors for widespread CNS depression

• CNS factors: neurological disease that may react abnormally to the CNS-depressing and muscle-relaxing effects, such as epilepsy, stroke, and myasthenia gravis.
• Cardiovascular (CV) factors: underlying CV disease worsened by severe reactions to anesthesia (shock, hypotension, dysrhythmia, ischemia), such as coronary artery disease (CAD).
• Respiratory factors: obstructive pulmonary disease that complicates gas delivery, intubation, and mechanical ventilation, such as asthma, chronic obstructive pulmonary disease (COPD), and bronchitis.
• Renal and hepatic function: conditions that interfere with metabolism and excretion and can prolong anesthesia, such as acute renal failure and hepatitis.

Depth of anesthesia (stages)

• Stage 1, Analgesia: loss of pain sensation, patient still conscious and able to communicate.
• Stage 2, Excitement: excitement and often combative behavior with signs of sympathetic stimulation.
• Stage 3, Surgical Anesthesia: muscle relaxation, regular respirations, progressive loss of eye reflexes, pupil dilation. Surgery is performed here.
• Stage 4, Medullary Paralysis: very deep CNS depression with loss of respiratory and vasomotor center stimuli. Anesthesia has become too intense and death can occur rapidly.

Phases of administration

• Induction: from the start of anesthesia to stage 3. The most dangerous period is stage 2, because of the systemic stimulation that occurs.
• Maintenance: from stage 3 to completion of surgery.
• Recovery: from discontinuation of the anesthetic to regained consciousness, movement, and ability to communicate.

Local Anesthesia

Loss of sensation in a limited area, achieved by several methods:

• Topical: cream, lotion, ointment, or drops applied to traumatized skin or to mucous membranes of the eyes, nose, throat, mouth, urethra, anus, or rectum.
• Infiltration: injecting the anesthetic directly into the tissue to be treated, putting it in contact with the nerve endings there and stopping them from transmitting impulses to the brain.
• Field block: injecting around the area affected by surgery so the anesthetic contacts all the surrounding nerve endings. Often used for tooth extraction.
• Nerve block: injecting along the nerve(s) running to and from the target region. Types include peripheral nerve block, central nerve block, epidural anesthesia, caudal block, and spinal anesthesia.

Age-Group Considerations (General Anesthetics)

These apply across the general anesthetic classes; drug-specific age notes appear under each agent below.

• Children: at greater risk for complications after anesthesia (laryngospasm, bronchospasm, aspiration). Provide support and reassurance, assess for skin breakdown related to immobility, and keep safety precautions in place.
• Adults: educate on what happens during administration and the expected body reactions. Reassure them continuously during the period when they are aware of their surroundings but unable to speak. Most general anesthetics are not recommended in pregnancy because of potential harm to the fetus. Lactating women need 4-6 hours after the anesthetic before nursing.
• Older adults: more susceptible to adverse effects (CNS, CV, dermatological) and at risk for toxicity from possible hepatic and renal impairment. Institute safety measures (side rails, call light, ambulation assistance, skin care), monitor longer, and reorient and reassure regularly. After general anesthesia, promote vigorous pulmonary toilet to reduce pneumonia risk.

General Anesthetic Agents

General anesthetic agents fall into four classes: barbiturate anesthetics, nonbarbiturate anesthetics, anesthetic gases, and volatile liquids.

Barbiturate Anesthetics

Intravenous drugs used to induce rapid anesthesia, then maintained with an inhaled drug.

Therapeutic Action

Depress the CNS to produce hypnosis and anesthesia without analgesia.

Indications

Induction and maintenance of anesthesia and induction of hypnosis. Thiopental is the most widely used intravenous anesthetic. Neither thiopental nor methohexital has analgesic properties, so patients need analgesics after the operation.

Pharmacokinetics

Here are the characteristic interactions of barbiturate anesthetics and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

• Silicone (rubber stoppers, disposable syringes): methohexital causes immediate breakdown of silicone.
• Pregnancy, lactation: CNS-depressant effects on fetus and baby.
• Do not use until the anesthesiologist and staff are ready and equipped for intubation and respiratory support. The rapid onset can cause respiratory depression and apnea.

Adverse Effects

• CNS: CNS suppression
• CV: bradycardia, hypotension
• Respiratory: respiratory depression
• GI: decreased GI activity
• Nausea and vomiting are common after recovery.

Interactions

• Theophylline, oral anticoagulants, beta-blockers, corticosteroids, hormonal contraceptives, phenylbutazones, metronidazole, quinidine, carbamazepine: decreased effectiveness with barbiturates.
• Narcotics: increased risk for apnea.

Nonbarbiturate Anesthetics

The other parenteral drugs used for intravenous anesthesia.

Therapeutic Action

Potent amnesiacs thought to act in the reticular activating system and limbic system to potentiate the effects of GABA, with little effect on cortical function.

Indications

• Midazolam, the prototype, produces amnesia or sedation for diagnostic, therapeutic, and endoscopic procedures, induces anesthesia, and provides continuous sedation for intubated, mechanically ventilated patients.
• Droperidol produces marked sedation and mental detachment, with an antiemetic effect that reduces nausea and vomiting in surgical and diagnostic procedures.
• Ketamine is useful when cardiac depression is dangerous, because it causes sympathetic stimulation with a rise in blood pressure and heart rate.
• Propofol suits short procedures: very rapid clearance, much less hangover effect, and quick recovery.

Age-specific notes: propofol is widely used for diagnostic tests and short procedures in children older than 3 years because of its rapid onset and metabolism. Etomidate is not recommended in children younger than 10 years.

Pharmacokinetics

Here are the characteristic interactions of nonbarbiturate anesthetics and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

• Conditions worsened by vomiting: midazolam is more likely to cause nausea and vomiting than other anesthetics.
• Renal or hepatic failure, prolonged QT intervals: contraindicate droperidol.
• Respiratory depression and arrest are associated with nonbarbiturate anesthetics, so keep life support equipment available at all times.

Adverse Effects

• Midazolam: CNS suppression, respiratory depression
• Droperidol: chills, hypotension, hallucinations, drowsiness, QT prolongation
• Etomidate: myoclonic and tonic movements
• Ketamine: hallucinations, dreams, psychotic episodes (can cross the blood-brain barrier)
• Propofol: local burning at injection sites, bradycardia, hypotension, pulmonary edema
• Fospropofol: perianal burning, stinging, tingling, rash (usually pass without intervention)

Interactions

• Ketamine and halothane: severe cardiac depression with hypotension and bradycardia.
• NMJ blockers: potentiated neuromuscular blockade when paired with ketamine.
• Inhaled anesthetics, other CNS depressants, narcotics, propofol, thiopental: increased toxicity and length of recovery with midazolam.

Anesthetic Gases

Anesthetic gases enter the bronchi and alveoli, cross the capillary system, and are carried to the heart and pumped through the body. They are lipophilic with high affinity for fatty tissue, including the lipid membrane of CNS nerves, pass quickly to the brain, and cause CNS depression. They are very flammable and carry toxic adverse effects.

Therapeutic Action

Move quickly in and out of the body, so they can accumulate in closed compartments (such as the sinuses) and cause pressure there. Very potent analgesics. Do not cause muscle relaxation.

Indications

Only one anesthetic gas, nitrous oxide (blue cylinder), is still used. It is typically used for dental surgery and is also combined with other agents for anesthetic use.

Age-specific note: children need to be cautioned not to bite themselves when receiving dental anesthesia.

Pharmacokinetics

Here are the characteristic interactions of anesthetic gases and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

• Conditions at risk for hypoxia: oxygen is always given with nitrous oxide, because the drug can block oxygen reuptake after surgery. Monitor susceptible patients for hypoxia, chest pain, and stroke.
• Pregnancy: potential adverse effects to the fetus.
• Lactation: wait 4 hours after nitrous oxide before nursing a baby.

Adverse Effects

• Respiratory: pneumothorax
• GI: bowel obstruction
• EENT: acute sinus pain, middle ear pain
• Inactivates vitamin B12.

Interactions

• Ketamine and halothane: severe cardiac depression with hypotension and bradycardia.

Volatile Liquids

Inhaled anesthetics that are unstable at room temperature and release gases. Most are halogenated hydrocarbons.

Therapeutic Action

Depress the CNS to cause anesthesia and also relax muscles. They sensitize the myocardium to the effects of norepinephrine and epinephrine.

Indications

• Halothane, the prototype, maintains anesthesia and can work as an induction agent.
• Desflurane is widely used in outpatient surgery for its rapid onset and quick recovery.
• Isoflurane is widely used to maintain anesthesia after induction and can cause muscle relaxation.

Age-specific note: halothane is widely used in children, especially those with respiratory dysfunction, because it tends to produce bronchial dilation, but it is contraindicated with increased intracranial pressure (ICP).

Pharmacokinetics

Here are the characteristic interactions of volatile liquids and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

• Hepatic impairment: can contribute to hepatic toxicity.
• Cardiovascular disease: associated with bradycardia and hypotension.
• Respiratory depression and increased sensitivity: tend to depress respiration and irritate the airways.
• Pregnancy, lactation: potential adverse effects to fetus and baby.
• All of these drugs can trigger malignant hyperthermia. MHAUS lists every halogenated volatile agent (halothane, enflurane, isoflurane, sevoflurane, desflurane) plus succinylcholine as triggers, while nitrous oxide, barbiturates, opioids, and local anesthetics are considered safe. Dantrolene is the treatment and, per MHAUS, must be available within 10 minutes of the decision to treat wherever these agents are given (MHAUS, Safe and Unsafe Anesthetics).

Adverse Effects

• Halothane's recovery syndrome: fever, anorexia, nausea, vomiting, hepatitis (can progress to fatal hepatic necrosis). Not used for more than 3 weeks, to reduce patient risk.
• Desflurane respiratory reactions: cough, increased secretions, laryngospasm.

Interactions

• Use caution when any of these drugs is combined with other CNS suppressants.

Nursing Considerations (General Anesthetics)

Nursing Assessment

• Assess for the cautions and contraindications above (drug allergies, hepatic and renal impairment) to prevent complications.
• Perform a thorough physical assessment (weight, neurological status, vital signs, heart sounds, skin color and lesions, bowel sounds) for baseline data, to gauge effectiveness, and to catch adverse effects.
• Monitor lab results (liver and renal function tests) for possible dose reduction and toxicity.

Nursing Diagnoses

• Impaired gas exchange related to respiratory depression.
• Impaired skin integrity related to immobility from positioning during anesthesia.
• Risk for injury related to CNS-depressant drug effects.

Implementation

• Prepare emergency equipment to maintain the airway and provide mechanical ventilation when the patient cannot maintain respiration because of CNS depression.
• Monitor temperature for prompt detection and treatment of malignant hyperthermia. Keep dantrolene on standby.
• Monitor vital signs and ECG to assess the systemic response to CNS depression and support as needed.
• Provide safety measures (adequate lighting, raised side rails) to prevent injury.
• Educate the patient on drug therapy to promote understanding and compliance.
• Provide comfort measures (pain relief, skin care) to help the patient tolerate drug effects.

Evaluation

• Monitor patient response (analgesia, loss of consciousness).
• Monitor for adverse effects (respiratory depression, hypotension, bronchospasm, skin breakdown).
• Confirm understanding by asking the patient to name the drug, its indication, and the adverse effects to watch for.
• Monitor compliance with drug therapy.

Local Anesthetic Agents

Local anesthetics prevent pain for varying periods after they are given in the peripheral nervous system. They block sensation in this sequence: temperature, touch, proprioception, and skeletal muscle tone. They are powerful nerve blockers and should not be absorbed systemically, since systemic absorption causes toxic effects on the nervous system and heart. They are either esters or amides; pramoxine fits neither class.

Therapeutic Action

Local anesthetics cause a temporary interruption in the production and conduction of nerve impulses. They alter the permeability of nerve membranes to sodium ions; by keeping sodium ions out of the nerve, they stop it from depolarizing. They reduce the height and rate of rise of the action potential, raise the excitation threshold, and slow conduction velocity. Ester local anesthetics are broken down immediately in the plasma by enzymes called plasma esterases.

Indications

Infiltration anesthesia, peripheral and sympathetic nerve blocks, central nerve blocks, spinal and caudal anesthesia, and topical anesthesia for skin or mucous membrane disorders.

Age-specific notes: local anesthetics are used in children much as in adults, but infants are at particular risk for systemic absorption and toxicity from topically applied agents, and tight diapers and occlusive dressings increase absorption. Regional or local anesthesia is preferred if surgery is needed during pregnancy. Older adults are more susceptible to adverse effects (CNS, CV, dermatological) and to toxicity from hepatic and renal impairment, so use safety measures, monitor longer, and reorient and reassure regularly.

Pharmacokinetics

Here are the characteristic interactions of local anesthetics and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

• Allergy to anesthetics and parabens: avoid hypersensitivity reactions.
• Heart block: could be exacerbated with systemic absorption.
• Shock: can alter local delivery and absorption.
• Decreased plasma esterase: can produce toxic levels of ester-type local anesthetics.
• Pregnancy, lactation: potential adverse effects to fetus and baby.

Adverse Effects

• CNS: headache (especially with epidural and spinal anesthesia), restlessness, anxiety, dizziness, tremors, blurred vision, backache
• CV: peripheral vasodilation, myocardial depression, arrhythmias, blood pressure changes
• Respiratory: respiratory arrest
• GI: nausea, vomiting
• Loss of skin integrity, especially in patients who cannot move.

Interactions

• Succinylcholine: increased and prolonged neuromuscular blockade.
• Epinephrine: less risk of systemic absorption and increased local effect.

Nursing Considerations (Local Anesthetics)

Nursing Assessment

• Assess for the cautions and contraindications above (drug allergies, hepatic and renal impairment) to prevent complications.
• Perform a thorough physical assessment (weight, neurological status, vital signs, heart sounds, skin color and lesions, bowel sounds) for baseline data, to gauge effectiveness, and to catch adverse effects.
• Inspect the application site to confirm skin integrity and prevent inadvertent systemic absorption.
• Monitor lab results (liver and renal function tests, plasma esterases) for possible dose reduction and toxicity.

Nursing Diagnoses

• Disturbed sensory perception related to local anesthetic effect.
• Impaired skin integrity related to immobility caused by the drug.
• Risk for injury related to loss of sensation and mobility.

Implementation

• Prepare emergency equipment to maintain the airway and provide mechanical ventilation if needed. Watch for local anesthetic systemic toxicity (LAST) from inadvertent systemic absorption, which presents with CNS signs (perioral numbness, tinnitus, agitation, seizures) that can progress to cardiac arrest. Intravenous 20% lipid emulsion is the definitive treatment and should be started at the first signs of serious toxicity, alongside airway support (Local Anesthetic Toxicity, StatPearls).
• Keep patients receiving spinal or epidural anesthesia well hydrated and lying down for up to 12 hours afterward to minimize headache.
• Provide skin care to the administration site to reduce breakdown.
• Provide comfort measures to help the patient tolerate drug effects.
• Provide safety measures (adequate lighting, raised side rails) to prevent injury.
• Educate the patient on drug therapy to promote understanding and compliance.

Evaluation

• Monitor patient response (loss of feeling in the designated area).
• Monitor for adverse effects (respiratory depression, blood pressure changes, arrhythmias, GI upset, skin breakdown, injury, CNS alterations).
• Confirm understanding by asking the patient to name the drug, its indication, and the adverse effects to watch for.
• Monitor compliance with drug therapy.

Frequently Asked Questions

What is the difference between general and local anesthesia? General anesthetics depress the whole central nervous system to remove pain, consciousness, and recall, so the nurse's focus is the airway, vital signs, and depth of anesthesia. Local anesthetics numb a defined area by blocking nerve conduction without systemic CNS depression, so the focus shifts to preventing systemic absorption and catching toxicity early.

What are the four stages of general anesthesia? Stage 1 is analgesia (still conscious), stage 2 is excitement (the most dangerous period during induction, with possible combative behavior), stage 3 is surgical anesthesia (where surgery is done), and stage 4 is medullary paralysis (too deep, with loss of respiratory and vasomotor drive and risk of death).

Which anesthetics trigger malignant hyperthermia, and what is the antidote? The halogenated volatile liquids (halothane, enflurane, isoflurane, sevoflurane, desflurane) and the depolarizing muscle relaxant succinylcholine are the triggers. Dantrolene is the treatment and, per MHAUS, must be available within 10 minutes of the decision to treat wherever these agents are used. Nitrous oxide, barbiturates, opioids, and local anesthetics are considered safe (MHAUS).

What is local anesthetic systemic toxicity (LAST)? LAST happens when a local anesthetic reaches the bloodstream in toxic amounts. Early CNS signs include perioral numbness, tinnitus, metallic taste, and agitation, which can progress to seizures, then cardiovascular collapse. Intravenous 20% lipid emulsion is the definitive treatment and is started at the first serious signs, along with airway and circulatory support (Local Anesthetic Toxicity, StatPearls).

Why is epinephrine sometimes added to a local anesthetic? Epinephrine causes local vasoconstriction, which slows systemic absorption of the anesthetic. That keeps the drug at the site longer for a stronger, longer local effect and lowers the risk of systemic toxicity.

Why must spinal and epidural patients lie down and stay hydrated afterward? Dural puncture can cause a post-anesthesia headache. Keeping the patient well hydrated and lying flat for up to 12 hours after the block helps minimize that headache while sensation and mobility return.