Beyond Sedation: Exploring Drugs
That Interfere with Anesthesia
Introduction
Mechanism of General
Anesthesia
Anesthetic Gases
Intravenous Anesthetic Agents
Neural Suppression
Cardiovascular and Respiratory Depression
Categories of Interfering
Medications
Psychiatric Medications
Allergy and Cold Medications
Cardiovascular Medications
Gastrointestinal Medications
Pain Medications
Neurological Medications
Alternative Medicines and Supplements
Illicit and Recreational Drugs
Specific Drug Interactions and
Effects
Antidepressants
Antihistamines
Diuretics
NSAIDs
Muscle Relaxants
Herbal Supplements
Cocaine and Amphetamines
Marijuana
Mechanisms of Adverse Effects
Potentiation of Anesthesia
Nervous System Depression
Blood Pressure Instability
Heart Rhythm Disturbances
Impaired Clotting
Respiratory Impairment
Delayed Recovery
Pre-Operative Risk Assessment
Reviewing Medications
Evaluating Medical Conditions
Identifying Risk Factors
Developing Management Plan
Educating the Patient
Anesthetic Adjustments and
Modifications
Altering Medications
Changing Anesthetic Choice
Adjusting Dosage and Delivery
Extra Caution with Paralytics
Limiting Regional Anesthesia
Vigilant Intra-Operative
Monitoring
Cardiovascular Parameters
Pulmonary Function
Body Temperature
Muscle Relaxation
Additional Monitoring Options
Post-Operative Care
Considerations
Extended Recovery Room Stay
Ongoing Vital Sign Monitoring
Preventing and Managing Complications
Following Up After Discharge
Creating an Anesthesia Care
Plan
Complete Medication Review
Surgery Risk Assessment
Patient Optimization
Anesthesia Plan
Informed Consent
Conclusion
FAQs
Introduction
Anesthesia allows patients to
safely undergo surgery by inducing unconsciousness, amnesia, pain relief, and
muscle relaxation. However, many types of medications can potentially interfere
with anesthesia and create complications. Understanding these drug interactions
is extremely important for anesthesia providers to deliver high quality,
effective care and avoid adverse outcomes. This comprehensive article will
explore a wide range of drugs that may interfere with anesthesia, their
mechanisms of interaction, effects on the body, risk assessment, and strategies
to safely manage patients taking these medications perioperatively. 💊👨⚕️
The main keyword "drugs that
interfere with anesthesia" encompasses a broad category of
pharmaceuticals, supplements, and illicit substances that can alter the
metabolism and effects of anesthetic agents in potentially dangerous ways.
Specific drugs will be examined in detail, along with their impact on anesthesia
and surgical risks they pose. Additionally, vital pre-operative,
intra-operative, and post-operative considerations will be discussed to
optimize patient safety when dealing with these concerning medication
interactions. The goal is to provide anesthesia practitioners with an extensive
overview of this clinically significant issue in order to prevent complications
and enhance patient care. Let's dive in!⛑️
Mechanism of General Anesthesia
To understand how various drugs
can interfere with anesthesia, it is important to first understand how general
anesthetic agents work in the body and brain. The state of general anesthesia
is complex and involves multiple components mediated by both intravenous and
inhaled anesthetic drugs.👨🔬
Anesthetic Gases
Inhaled gases like sevoflurane,
desflurane, and isoflurane are absorbed into the lungs and bloodstream. They
traverse the blood-brain barrier and interact with proteins on neuron cell
membranes called GABA receptors. Here, they enhance the inhibitory effects of
the neurotransmitter GABA and suppress central nervous system activity.
Inhalational agents also bind to
N-methyl-D-aspartate (NMDA) receptors on neurons. NMDA receptor inhibition
decreases excitatory nerve signaling related to wakefullness and pain
sensation.
Volatile gases additionally exert
effects on the cardiovascular system, causing dose-dependent decreases in blood
pressure and peripheral vascular resistance. Respiration may also become
depressed.
Intravenous Anesthetic Agents
Intravenous anesthetic agents
such as propofol, etomidate, ketamine, and benzodiazepines work on the central
nervous system through various mechanisms.
Propofol enhances GABA receptor
activity, similar to inhalational agents. It also modulates sodium channels on
neurons to inhibit nerve transmission.
Ketamine and etomidate act as
NMDA receptor antagonists, blocking excitatory activity.
Benzodiazepines like midazolam
activate GABA receptors to increase sedation and amnesia.
IV agents also reduce blood pressure,
respiratory drive, and heart rate via effects on the brain and circulation.
Neural Suppression
Through these various pathways,
inhaled and intravenous anesthetics suppress overall CNS activity. This leads
to a controlled, reversible loss of consciousness, loss of memory formation,
lack of pain sensation, and immobility.
Cardiovascular and Respiratory
Depression
While inducing CNS depression to
achieve general anesthesia, anesthetic medications also suppress cardiac and
respiratory function in a dose-dependent manner.
Blood pressure drops through
vasodilation. Heart rate slows via autonomic effects. Breathing becomes slowed
and shallow. Cough and gag reflexes are also inhibited.
Understanding these mechanisms
provides insight into how additional medications could potentially interfere
with anesthesia in dangerous ways. Any drug that also impacts the CNS,
cardiovascular system, or respiration has potential to interact. Next, we will
explore some major categories of medications with important anesthesia
interactions.
Categories of Interfering
Medications
Many types of prescription,
over-the-counter, herbal, and illicit medications have concerning interactions
with general anesthesia. These drugs come from a wide range of therapeutic categories
and have diverse mechanisms of action in the body. Some major categories
include:
Psychiatric Medications
Psychiatric drugs like
antidepressants, antipsychotics, and antianxiety agents affect
neurotransmitters and neural transmission. Selective serotonin reuptake
inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs),
tricyclic antidepressants (TCAs), and monoamine oxidase inhibitors (MAOIs)
impact serotonin, norepinephrine, dopamine, and other key signaling molecules
in the brain and nerves.
Allergy and Cold Medications
Antihistamines like
diphenhydramine and medications containing decongestants such as
pseudoephedrine have anticholinergic properties. They block acetylcholine, a
critical neurotransmitter involved in arousal, breathing, heart rate
regulation, and other vital functions.
Cardiovascular Medications
Blood pressure medications
including diuretics, beta blockers, ACE inhibitors, and calcium channel
blockers alter fluid balance, vascular resistance, heart rate, and cardiac
conduction. Anticoagulants or antiplatelets affect clotting factors and
bleeding risks.
Gastrointestinal Medications
Acid reducers like proton pump
inhibitors (PPIs) raise gastric pH and may affect drug absorption. H2 blockers
like famotidine also impact acid secretion. Laxatives, antidiarrheals,
antiemetics, and other GI agents disrupt motility, secretion, and absorption -
all factors that may alter anesthetic drug effects and metabolism.
Pain Medications
Non-steroidal anti-inflammatory
drugs (NSAIDs), acetaminophen, opioids, and analgesics/antipyretics have
widespread effects on pain and inflammatory pathways, including prostaglandin
synthesis, endorphin release, and pain sensation signaling. They may interact
with anesthetic mechanisms in the central and peripheral nervous systems.
Neurological Medications
Antiseizure drugs, muscle
relaxants, neuroleptics, sedatives like benzodiazepines, and other neurologic
agents exert diverse effects on nerve transmission, motor pathways, and
neurotransmitter systems that may be additive, synergistic, or competitive with
general anesthesia drugs.
Alternative Medicines and
Supplements
Herbal products, probiotics,
nutraceuticals, and vitamins/minerals may have underrecognized effects on drug
metabolism, bleeding risks, and anesthesia potency due to components like
bromelain, garlic, gingko, ginseng, St John's Wort, valerian root, and others.
Illicit and Recreational Drugs
Substances like marijuana,
cocaine, amphetamines, hallucinogens, and others dramatically impact neurotransmitter
signaling, cardiovascular function, and metabolism. Their largely unpredictable
effects make anesthesia risk extremely hazardous.
This overview demonstrates the
diversity of medication classes that can potentially interfere with anesthesia
and surgery. Next we will look closer at some of the most common examples
within these categories and their specific mechanisms of interaction and
related adverse effects.
Specific Drug Interactions and
Effects
While many types of medications
may cause issues, some common culprits have interactions that are particularly
important for anesthesia providers to recognize.
Antidepressants
Selective serotonin reuptake
inhibitors (SSRIs) like fluoxetine, sertraline, citalopram, and others are
among the most concerning drugs given their widespread use. SRNIs like
duloxetine also have similar effects.
These work by blocking reuptake
of serotonin, norepinephrine, and dopamine in the central and peripheral
nervous systems. But this mechanism impacts signaling molecules that are also
affected by anesthetic agents.
In particular, effects on
serotonin pathways appear to enhance and prolong the effects of certain
anesthetics - potentially causing excessive sedation, cardiovascular
instability, and delayed emergence after surgery.
Antihistamines
Histamine blockers with
anticholinergic properties such as diphenhydramine and chlorpheniramine have long
been known to complicate anesthesia.
By blocking acetylcholine
activity in the brain and body, they can markedly prolong the effects of both
inhaled and intravenous anesthesia. This delays awakening from general
anesthesia.
Their anticholinergic effects
also slow heart rate and may worsen hypotension under anesthesia. Impaired
bronchial secretions can lead to post-op lung congestion. Confusion after
surgery may be more common as well.
Diuretics
Loop diuretics like furosemide
are incredibly common for treating hypertension and edema. But their dramatic
effects on fluid and electrolyte balance can create hazards under anesthesia.
Sudden electrolyte shifts affect
cardiac stability - sudden drops in potassium and magnesium predispose to
dysrhythmias during surgery. Dehydration also exacerettes hypotension under
anesthesia.
Additionally, diuretics alter the
volumes of distribution of intravenous anesthetic agents. This makes their
effects less predictable.
NSAIDs
Non-steroidal anti-inflammatory
drugs like ibuprofen, naproxen, and others inhibit cyclooxygenase (COX) enzymes
involved in pain, inflammation, fever, and coagulation pathways.
Their effects on platelet
function and clotting factors in particular lead to substantially increased
bleeding risks during surgery under anesthesia.
They also irritate gastric mucosa and impair
kidneys, increasing surgical complications. Caution with dosing is needed.
Muscle Relaxants
Medications like cyclobenzaprine,
carisoprodol, tizanidine and others used for musculoskeletal pain and spasm act
directly on central nervous system pathways that are also affected by
anesthetic paralytics.
Concurrent use can greatly
prolong paralysis from medications like succinylcholine and rocuronium after
surgery. This leads to risks like aspiration, hypoventilation, and upper airway
obstruction in the postoperative period if ventilation and monitoring are not
properly managed.
Herbal Supplements
Herbal products like St John's
Wort, gingko biloba, ginseng, garlic, and others contain diverse phytochemicals
whose interactions with anesthesia are complex and poorly understood.
However, many compounds appear to
competitively bind to enzyme systems and protein carriers also affected by general
anesthetics - potentially increasing their potency to excessive levels.
Certain supplements also directly
influence bleeding risks or act as sedatives, creating additive effects of
unclear magnitude. Their use should be minimized perioperatively due to
unpredictable interactions.
Cocaine and Amphetamines
Illicit stimulants like cocaine
and amphetamines flood the brain with excessive dopamine, norepinephrine, and
serotonin through disinhibition of synaptic reuptake mechanisms.
This overwhelms cardiovascular
stability through uncontrolled hypertension, tachycardia, and vasospasm under
the hemodynamic effects of anesthesia. Myocardial irritability also increases,
raising risks for perioperative infarcts, strokes, and arrhythmias.
Marijuana
Cannabis products containing THC
have complex effects on the CNS and cardiovascular system that are not well
understood. But post-operative cognitive dysfunction and cardiac effects have
been demonstrated.
THC and other cannabinoids likely
interact with anesthesia through impacts on GABA, glutamate, opioid, and
serotomimetic receptors in the brain and spinal cord that may lead to
unpredictable potentiation or inhibition effects.
Now that we have reviewed some of
the most problematic specific medication types, we will discuss the range of
adverse effects that can result from these concerning drug interactions with
anesthesia.
Mechanisms of Adverse Effects
There are several key mechanisms
by which medications interfere with general anesthesia to produce
complications:
Potentiation of Anesthesia
Some drugs like SSRIs and
antihistamines enhance the effects of anesthetics - either through additive CNS
depression or possibly direct receptor interactions. This results in prolonged
sedation, difficulty waking at the end of surgery, and slower post-op recovery.
Nervous System Depression
Many agents directly depress
neural transmission, compounding the CNS suppression caused by anesthetics.
This enhances sedation and cognitive dysfunction.
Blood Pressure Instability
Medications that lower blood
pressure like diuretics or neurologic agents can worsen anesthesia-induced
hypotension. On the other hand, drugs with pressor effects like amphetamines
complicate management of hypertension.
Heart Rhythm Disturbances
Electrolyte disturbances and
direct effects on cardiac conduction from some drugs result in arrhythmias,
often when combined with intravenous anesthetic effects on electrical
conduction in the heart.
Impaired Clotting
NSAIDs and certain herbal
products impair platelet function and intrinsic clotting mechanisms. Under
anesthesia, this heightens already substantial bleeding risks from surgery
itself.
Respiratory Impairment
Depression of breathing from
medication interactions with anesthesia may necessitate ongoing ventilation
after surgery. This includes increased risks for airway obstruction and
aspiration.
Delayed Recovery
Prolonged sedation and cognitive
dysfunction from interacting medications delays emergence after anesthesia and
discharge from the recovery room - increasing healthcare costs and affecting
outcomes.
These varied mechanisms
demonstrate the importance of assessing medication use pre-operatively and
selecting anesthesia techniques least likely to compound these concerning
interactions intraoperatively.
Pre-Operative Risk Assessment
Before any surgery with general
anesthesia, a thorough risk assessment is critical to detect potential
medication interactions and optimize the patient's overall medical status. Key
elements include:
Reviewing Medications
Obtain a complete list of the
patient's prescription medications, over-the-counter drugs, herbal supplements,
nutraceuticals, and illicit drug use. Determine which agents may potentially
complicate anesthesia management based on the interactions discussed earlier.
Evaluating Medical Conditions
Assess the patient's underlying
health conditions like cardiovascular disease, respiratory disease, endocrine
disorders, kidney dysfunction, obesity, sleep apnea, and others that may be
exacerbated by medication effects under anesthesia.
Identifying Risk Factors
Based on the medication review
and medical evaluation, determine which risk factors are most significant -
these may include risks for hypotension, dysrhythmias, respiratory depression,
bleeding, delayed emergence, hypertension, and more.
Developing Management Plan
Create a tailored anesthesia care
plan to address the identified risks. This may involve adjusting preoperative
medications, intraoperative monitoring and interventions, post-operative
recovery protocols, and contingency planning. Clear communication with surgeons
is critical.
Educating the Patient
Explain identified risks and the
customized management plan to the patient or family. Obtain informed consent
detailing the increased risks related to medication interactions with
anesthesia. Make medication changes per protocols and ensure understanding of
perioperative instructions.
Thorough risk assessment sets the
stage for the subsequent components of safe anesthesia care in patients taking
potentially interacting medications.
Anesthetic Adjustments and
Modifications
Based on the risk profile, the
anesthesia technique itself can be adapted to account for medication
interactions while still ensuring adequate general anesthesia for the planned
surgery:
Altering Medications
High risk medications may need to
be modified preoperatively - either reduced or held for a number of days/weeks
or switched to alternatives less likely to interact with anesthesia. This is
coordinated with the prescribing doctor and patient through shared decision
making.
Changing Anesthetic Choice
The choice of intravenous agents,
inhalational gases, and other components of the general anesthetic can be
adapted to minimize risks identified - for example, avoiding propofol in
patients with difficult to control hypotension or using lower MAC gases if
excess sedation is a concern.
Adjusting Dosage and Delivery
Dosages of anesthesia medications
may need to be reduced depending on identified interactions. Anesthesia can
also be titrated carefully through continuous intravenous infusions rather than
large bolus drugs in selected cases to allow better titration.
Extra Caution with Paralytics
Depolarizing and non-depolarizing
muscle relaxants are used cautiously and dosed appropriately to limit prolonged
paralysis from medication interactions in susceptible patients.
Anticholinesterase inhibitors help reverse effects.
Limiting Regional Anesthesia
While regional anesthesia through
epidural or spinal routes avoids some systemic drug interactions, local
anesthetics still have cardiovascular and neurological effects. Careful dosing
is essential to avoid toxicity, hypotension, etc.
Adjunctive Medications and Fluids
IV fluids, vasopressors,
antiemetics, anticholinergics, and other supportive meds may be needed to
optimize hemodynamics, breathing, nausea, etc while accounting for medication
effects on the patient.
Invasive Monitoring
In high risk cases, invasive
arterial and central venous access allows beat-to-beat monitoring of blood
pressure, filling pressures, and sampling of blood gases and electrolytes. This
guides fluid, pressor, and other therapy.
Open Communication
The anesthesia team must
communicate methods to prevent interactions and manage any that occur to all
other perioperative staff including surgeons, nurses, and techs. Collaborative
approaches are key.
Vigilant Intra-Operative Monitoring
During the surgery itself,
meticulous monitoring is essential to detect any adverse physiologic effects
from medication interactions with anesthesia early so that timely interventions
can be taken:
Cardiovascular Parameters
Continuous heart rate and rhythm
monitoring, blood pressure cuff or arterial line pressures, and potentially
central venous pressures guide circulatory management and treatment of
instability.
Pulmonary Function
Oxygenation saturation via pulse
oximetry, end-tidal CO2, and spirometry identify respiratory depression,
hypoventilation, airway obstruction, and pulmonary edema to allow support.
Body Temperature
Core temperature is tracked and
controlled with forced air warming since many medications predispose patients
to intra-op hypothermia and shivering which increases oxygen consumption,
hypertension, and pain.
Muscle Relaxation
Nerve stimulators quantify the
degree of paralysis to guide dosing of neuromuscular blockers and determine
recovery, particularly in patients on chronic relaxants.
Additional Monitoring
Other modalities like EEG
bispectral index, depth of anesthesia monitoring, and cerebral oximetry provide
additional data points related to anesthetic depth and degree of consciousness
which guide dosing.
Post-Operative Care Considerations
Even after surgery concludes,
effects from medication interactions with anesthesia may persist. Close
monitoring and management during the post-operative period is key:
Extended Recovery Room Stay
Patients are kept in the
post-anesthesia care unit for an extended period to monitor for delayed
awakening, low blood pressure, bleeding, arrhythmias, oxygen desaturation,
neurologic changes, and other complications until stabilized.
Ongoing Vital Sign Monitoring
Cardiovascular vitals,
oxygenation, respiratory rate/pattern, and mental status assessments continue
every 15 minutes for 1-2 hours to ensure hemodynamic stability, adequate gas
exchange, and appropriate cognitive function before transferring from recovery.
Preventing and Managing
Complications
If issues like respiratory
depression, hypotension, dysrhythmias, delayed emergence, bleeding, or mental
status changes appear post-operatively, they are promptly addressed with
supportive therapies per clinical protocols to restore normal function.
Following Up After Discharge
Phone calls, prescription fills,
and follow up visits after discharge provide opportunities to check for
medication-related return of symptoms or new side effects and to adjust therapy
accordingly to stabilize patients. Clear instructions are essential.
Through each phase of care,
special efforts are made around medication reconciliation, avoidance of
problematic agents, sequencing of medications appropriately, and managing any
related symptoms that do appear perioperatively.
Creating an Anesthesia Care Plan
Pulling together all the steps
outlined, an overall structured process can optimize safety in patients at risk
for medication interactions with anesthesia:
Complete Medication Review
Compile a list of all medications
a patient is taking. Identify any that may potentially interact with anesthesia
based on mechanism, metabolism, and effects.
Surgery Risk Assessment
Consider factors like surgery
type, length, body position, blood loss risk, fluid shifts, etc that may
heighten risks from drug interactions in order to prepare.
Patient Optimization
Address modifiable health issues
through smoking cessation, weight loss, diet, hypertension control, etc. Adjust
high risk medications pre-operatively per established guidelines and protocols.
Anesthesia Plan
Choose anesthetic agents and
techniques that will limit risks identified from the patient's medication list
and medical conditions. Identify needed monitoring and have contingency plans
ready.
Informed Consent
Document a thorough discussion of
risks, benefits, and alternatives to anesthesia care related to medications
effects. Explain additional risks, need for vital sign monitoring, and
prolonged post-op recovery.
This purposeful, step-wise
approach can then be adapted to each individual patient scenario to mitigate
the unpredictable effects of medications interacting with anesthesia.
Conclusion
Interactions between anesthesia
medications and a patient's prescriptions, supplements, illicit drugs, and more
can lead to a wide range of cardiorespiratory, neurological, metabolic, and
coagulation disturbances perioperatively.
Thorough review of medications,
risk analysis, pre-operative adjustments, intra-operative modifications,
vigilant monitoring, and thoughtful post-operative care are all critical to
avoid adverse outcomes from these concerning and complex drug interactions.
By understanding mechanisms of
medication effects on anesthesia care, providers can thoughtfully select
approaches that maximize benefit while limiting risks related to the necessary
pharmacology these patients require for their existing medical conditions.
While many agents have been shown
to complicate anesthesia through varied mechanisms, mindful risk assessment,
patient preparation, careful anesthetic technique, and watchful management
allows positive outcomes to be achieved safely.
FAQs
What are some of the most common
types of medications that may interact with anesthesia?
Some of the most common include
SSRIs/SNRIs, diuretics, NSAIDs, antihistamines, muscle relaxants, prescription
pain medications, herbal supplements, illicit drugs, and OTC cold/allergy pills
containing decongestants or antihistamines.
Why does the anesthesia team need to
know all medications a patient is taking?
It is extremely important for the
anesthesia team to know about ALL medications the patient takes - prescription,
OTC, herbal, supplements, nutraceuticals, recreational drugs, etc. This
comprehensive list allows identification of agents that may potentially
interact with anesthesia to cause complications so they can be addressed and
managed appropriately.
What types of effects can
potentially occur from drug interactions with anesthesia?
Concerning effects include
cardiovascular instability like arrhythmias and hypotension, bleeding from drug
effects on clotting and platelets, respiratory depression and airway
obstruction, electrolyte disturbances, prolonged unconsciousness, delayed emergence
after surgery, confusion, increased pain, nausea and vomiting, and more.
How are patients optimized before
surgery who are on interacting medications?
Preoperative optimization
involves adjusting high risk medications in advance through tools like holding
or lowering doses of certain drugs, substituting alternate agents, timing doses
appropriately, and medically managing conditions like hypertension, pain, and
anxiety through methods less likely to interact with anesthesia.
Why are vital signs monitored
closely during surgery for patients on interacting meds?
Intra-operative monitoring allows
the anesthesia team to quickly detect problems like low blood pressure, oxygen
desaturation, arrhythmias, bleeding, or neurologic changes from medication
interactions so they can rapidly intervene to treat any issues and avoid
further complications.
What is done if a patient seems
excessively sedated after surgery and is not waking up promptly?
Delayed emergence and prolonged
sedation may indicate potentiation of anesthesia from certain interacting
medications. Supportive care is provided, such as supplemental oxygen, IV
fluids, vasopressors for low blood pressure, antiemetics for nausea, and
observation with supportive care until the patient achieves full consciousness.
Can illicit drug use increase
surgical risks related to anesthesia?
Absolutely. Many illicit drugs
like cocaine, amphetamines, and cannabis have potentially very dangerous
interactions with anesthetic agents leading to uncontrolled hypertension, heart
rhythm disturbances, excess sedation, and other issues. It is critical to
inform your anesthesiologist about any illicit drug use before undergoing
surgery requiring anesthesia.
What technique can make anesthesia
somewhat safer in high risk patients?
While not always appropriate, the
use of regional anesthesia through epidural or spinal approaches can avoid some
systemic medication interactions related to IV and inhaled general anesthesia
drugs. However, close monitoring is still very important to detect any
cardiovascular or respiratory effects.
How soon after surgery are
medication interactions no longer a concern?
It’s important to note that risks
from medication interactions can persist for hours to days after surgery since
the effects on awakening, cardiopulmonary function, bleeding, pain, and healing
can linger during the post-op recovery period. Careful monitoring and follow up
are needed to ensure stabilization.
What should patients keep in mind
regarding their medication list and anesthesia?
The most important things for
patients to remember are: 1) Disclose ALL medications to your anesthesiologist,
even illicit drugs; 2) Discuss possible interactions and concerns with your
doctors; 3) Follow instructions for adjusting medications before surgery; 4)
Report any new side effects during recovery promptly to your surgical team.