LAST (Local Anesthetic Systemic Toxicity): A practical update for clinicians
Summary
TLDRThis video script delves into Local Anesthetic Systemic Toxicity (LAST), a rare but serious complication of local anesthetic use that can lead to severe injury or death. It outlines the evolving clinical presentation of LAST, emphasizing the necessity for vigilance in prevention and the importance of understanding its mechanism. The script also discusses the multimodal antidotal role of lipid emulsion, risk factors, preventive measures, and management strategies, including the crucial steps to take in the event of an LAST episode.
Takeaways
- 🚨 Local anesthetic systemic toxicity (LAST) is a potentially fatal complication of local anesthetic use, with permanent injury or death as possible outcomes.
- 🔍 LAST is an overdose situation that can occur due to accidental intravascular injection or exceeding a patient's toxic threshold.
- 📈 The incidence of LAST is estimated to be between one to two in every thousand nerve blocks, but this number may be higher due to unreported cases.
- 🌐 The presentation of LAST has evolved and can vary, with about half of cases starting with neurologic signs and symptoms, and a quarter with only cardiac signs.
- 👨⚕️ The risk of LAST is not limited to a specific site of injection, and vigilance is required to prevent it, especially with the rise of outpatient procedures.
- 💊 The toxic mechanism of LAST involves blockade of sodium channels and mitochondrial poisoning, affecting primarily the heart and brain.
- 🩺 An antidote for LAST is the lipid emulsion, which works by scavenging local anesthetic molecules from the heart and brain, providing an inotropic effect, and improving cardiac output.
- 👶 Certain populations are at higher risk for LAST, including the elderly, infants under six months, pregnant patients, and those with reduced ventricular function or arrhythmias.
- ⚠️ Prevention strategies include being aware of dose limits, using fractional injection techniques, aspirating before injecting, and using epinephrine as a marker for intravascular injection.
- 🔬 Ultrasound guidance is associated with a significantly reduced incidence of LAST, emphasizing its importance in procedural practices.
- 🆘 In the event of LAST, immediate steps include stopping the injection, calling for help, maintaining airway, ventilating the patient, and administering lipid emulsion as the primary treatment.
Q & A
What is Local Anesthetic Systemic Toxicity (LAST)?
-LAST is a potentially fatal complication that can occur from the use of local anesthetics, either due to accidental intravascular injection or because the administered dose is too high for the patient, leading to toxic plasma levels.
How common is LAST and what are its historical presentation symptoms?
-LAST is considered a rare complication, occurring in approximately one to two in every thousand nerve blocks. Historically, it presented with prodromal symptoms such as numbness around the mouth, metallic taste, and ringing in the ears, followed by agitation, twitching, and seizures as plasma concentrations increased.
How has the understanding of LAST presentation evolved?
-Contemporary data shows that not all cases of LAST present with the classic order of symptoms. About half of the cases now present initially with neurologic signs and symptoms, a third with both neurologic and cardiovascular manifestations, and a quarter with only cardiac signs.
Why is it important to remain vigilant about preventing LAST?
-Preventing LAST is crucial because the traditional method of catching it early through prodromal symptoms is not reliable. Being vigilant helps in early detection and intervention, which can be life-saving.
What are some changes in where LAST occurs and which professionals are involved?
-While the majority of LAST cases still occur in hospitals, there has been an increase in cases in outpatient settings such as urology, cosmetic surgery, and dental offices. The proportion of LAST due to non-anesthesiologists has also increased, partly due to tumescent anesthesia for liposuction.
What is the toxic mechanism of LAST and how does it affect the body?
-The toxic mechanism of LAST involves blockade of sodium channels in the heart and CNS, inhibition of other ion channels, and primarily poisoning of the mitochondrial oxidative phosphorylation pathway, leading to metabolic asphyxiation. This results in cardiac and neurotoxicity due to the heart and brain's intolerance to intracellular energy depletion.
How does the lipid emulsion work as an antidote for LAST?
-Lipid emulsion works multimodally, primarily by scavenging lipid-soluble local anesthetic molecules from the heart and brain, reducing their concentration at ion channels, and providing fatty acid substrate for poisoned mitochondria. It also has a volume effect that helps generate cardiac output.
Which patient populations may be at higher risk for LAST?
-Populations at higher risk for LAST include the extremes of age (elderly with cardiac comorbidities and infants under six months with immature hepatic pathways), pregnant patients with reduced plasma binding proteins, and patients with reduced ventricular function or pre-existing arrhythmias.
What preventive strategies can be employed to reduce the risk of LAST?
-Strategies include being conscious of published dose limits, using the lowest effective dose, fractional injection with pauses, aspirating before injecting, using epinephrine as a marker for intravascular injection, and utilizing ultrasound guidance for blocks.
What are the special considerations for managing LAST in the case of a cardiac arrest?
-In a cardiac arrest due to LAST, standard ACLS should be followed with modifications: avoid using high doses of epinephrine or vasopressin, and do not use lidocaine to treat arrhythmias. Chest compressions are key to improve coronary perfusion with lipid emulsion.
What steps should be taken if LAST is suspected during a procedure?
-If LAST is suspected, immediately stop injecting the local anesthetic, call for help, prepare a lipid emulsion kit, maintain the airway, and if necessary, ventilate the patient. Administer benzodiazepines for seizures and start the lipid emulsion as soon as possible.
Outlines
🚨 Local Anesthetic Systemic Toxicity Overview
This paragraph introduces the concept of Local Anesthetic Systemic Toxicity (LAST), a serious complication arising from the use of local anesthetics. It explains that LAST is an overdose situation that can lead to permanent injury or death. The paragraph outlines the evolution of understanding regarding the presentation of LAST, moving from a classic symptom pattern to a more varied and unpredictable one. It also touches on the frequency of occurrence, the changing locations where LAST happens, and the shift in demographics of those affected. The toxic mechanism of LAST is described as involving sodium channel blockade and mitochondrial poisoning, leading to cardiac and neurotoxicity. The paragraph concludes with the introduction of lipid emulsion as an antidote for LAST, explaining its multimodal action in mitigating the toxic effects.
👶👵 Populations at Higher Risk for LAST
The second paragraph delves into the populations that are at a higher risk for LAST, including the elderly and infants under six months due to their physiological differences. It discusses how pregnant patients and those with reduced ventricular function or pre-existing arrhythmias are also at increased risk. The paragraph emphasizes the importance of preventive measures such as adhering to published dose limits, using the lowest effective dose, and utilizing techniques like fractional injection and aspiration before injection to minimize the risk of LAST. It also highlights the benefits of using epinephrine as a marker for intravascular injection and the advantages of ultrasound-guided blocks in reducing the incidence of LAST. Special attention is given to fascial plane blocks, catheters, and the use of intravenous lidocaine, with recommendations for cautious dosing.
🆘 Managing LAST: Immediate Actions and Treatment
The final paragraph focuses on the immediate steps to take in the event of a LAST occurrence. It provides a clear protocol for managing the crisis, starting with stopping the injection of the local anesthetic, calling for help, and preparing a lipid emulsion kit. The paragraph outlines the dosage and administration of lipid emulsion, including the bolus dose and infusion rate, and advises on adjusting these based on the patient's response. It also discusses the importance of maintaining the patient's airway and the use of benzodiazepines to control seizures. The paragraph advises against the use of certain medications during a LAST event that could exacerbate the situation and emphasizes the importance of standard ACLS procedures with modifications, such as prioritizing chest compressions for better lipid flow. It concludes with guidelines for post-stabilization monitoring and the potential need for advanced interventions like cardiopulmonary bypass or ECMO in severe cases, along with references to management flowcharts from professional organizations.
Mindmap
Keywords
💡Local Anesthetic Systemic Toxicity (LAST)
💡Plasma Levels
💡Prodromal Symptoms
💡Neurologic Signs and Symptoms
💡Cardiovascular Manifestations
💡Mitochondrial Poisoning
💡Lipid Emulsion
💡Risk Factors
💡Ultrasound Guidance
💡Fractional Injection
💡Epinephrine
Highlights
Local anesthetic systemic toxicity (LAST) is a potentially fatal complication of local anesthetic use.
LAST can result in permanent injury or death, emphasizing the importance of understanding its mechanisms.
LAST occurs due to accidental intravascular injection or an excessive dose for the patient's tolerance.
The incidence of LAST is estimated to be 1-2 in every thousand nerve blocks, but likely underreported.
Classic presentation of LAST includes numbness, metallic taste, and neurologic symptoms, followed by agitation and seizures.
Contemporary data shows varied presentations of LAST, not always following the classic order.
Prevention of LAST is crucial due to the unreliability of prodromal symptoms for early detection.
LAST can occur in various settings, including outpatient clinics and dental offices, not just in hospitals.
The toxic mechanism of LAST involves sodium channel blockade and mitochondrial poisoning, affecting the heart and brain.
Lipid emulsion is an effective antidote for LAST, working through multiple mechanisms including scavenging local anesthetics.
High-risk populations for LAST include the elderly, infants, and pregnant patients, requiring dose adjustments.
Patients with cardiac issues are more susceptible to LAST-induced myocardial depression.
Preventive strategies include adhering to dose limits, fractional injection, and aspirating before each dose.
Epinephrine is used in local anesthetics to detect intravascular injection and reduce peak plasma levels.
Ultrasound guidance is associated with a reduced incidence of LAST compared to non-ultrasound techniques.
Special considerations are needed for fascial plane blocks and catheters due to higher LAST risks.
In the event of LAST, immediate steps include stopping injection, calling for help, and preparing lipid emulsion.
Management of LAST includes maintaining airway, ventilating the patient, and using benzodiazepines for seizures.
Lipid emulsion dosage and administration guidelines are crucial during LAST management.
In cardiac arrest due to LAST, standard ACLS protocols should be adapted to avoid exacerbating the situation.
Post-incident monitoring is necessary to ensure the heart and brain are no longer at risk from LAST.
LAST management guidelines from professional organizations emphasize the importance of preparedness and vigilance.
Transcripts
[Music]
local anesthetic systemic toxicity or
last is a potentially fatal complication
of local anesthetic use the presentation
can be variable but a substantial number
of these cases result in permanent
injury or death and understanding the
ins and outs of this complication is a
must for any clinician using local
anesthetics in this video we'll review
the mechanism the clinical presentation
as well as strategies for prevention and
management last is an overdose of local
anesthetic and happens either because
we've accidentally put a big dose of
local in a vessel or for whatever reason
the local we've administered into the
correct body compartment is just too
much for that particular patient and the
plasma levels hit a toxic threshold is
this a rare complication
maybe our best numbers suggest that it
happens in one to two in every thousand
nerve blocks however those are just the
ones we know about from perspective
registries or databases there are no
doubt several fold more cases that go
unreported especially if the outcome is
favorable
our understanding of how last presents
has evolved over the last several
decades and especially in the era of
ultrasound and fascial plane blocks the
classic presentation was based on rising
levels of plasma local anesthetic and
started with the prodromal symptoms
numbness around the mouth and tongue
ringing in the ears a metallic taste and
some other non-specific neurologic items
then as plasma concentration increased
the patient would become agitated
restless and start to twitch and
eventually seize
only the cases with the highest plasma
levels would develop arrhythmias and
cardiac pump failure it's important to
understand that while the syndrome can
present in that specific order it
certainly doesn't have to more
contemporary data show that just under
half of all cases present initially with
neurologic signs and symptoms makes
sense a third percent with both
neurologic and cardiovascular
manifestations at the same time so that
means that about a quarter percent with
only cardiac signs that's not good
in the old days we kind of relied on the
paradigm of hopefully i'll catch the
last early because i'll watch for the
prodrome we know that's just not
reliable anymore and this speaks to the
need to remain uber vigilant about
preventing last another thing that's
changed is where it happens while the
majority still occur in hospital about
40 happen in ascs outpatient urology
clinics cosmetic surgery clinics dental
offices and so on as anesthesiologists
we used to own this complication because
we were the ones using large volumes of
local anesthetic and running into
trouble in the last 10 years we've seen
an uptick in the proportion of last due
to surgeons and other proceduralists at
least part of that trend relates to
tumescent anesthesia for liposuction the
site of injection seems to matter too
although that picture has changed
slightly as well a commonly taught list
of injection sites ranked in order of
potential for systemic absorption
started with intercostal and epidural
and ended with subcutaneous and it made
sense that these might represent a
graded risk for last more recent case
reports suggest that procedures such as
penile blocks in children and local
infiltration analgesia for joint
replacement are bigger culprits this
probably represents inattention to
dosing limits relative to patient's size
neraxial is still up there as are upper
extremity blocks and pair vertebral
blocks but keep in mind that there is no
site that is truly safe from last the
toxic mechanism is complicated and not
fully understood we do know that part of
it relates to blockade of sodium
channels in the heart and central
nervous system but there's also
inhibition of other membrane ion
channels including potassium calcium and
others however the primary toxic
mechanism probably relates to poisoning
of the mitochondrial oxidative
phosphorylation pathway to put it more
simply the cells just can't generate atp
for energy they're metabolically
asphyxiated as you might expect the
organs that are most intolerant of
intracellular energy depletion are the
heart and brain which is why the
clinical syndrome manifests as cardiac
and neurotoxicity this mitochondrial
poisoning theory may also explain why
the usual hemodynamic therapies like
vasopressors and anatropic drugs are
frustratingly ineffective in severe last
in the brain high local anesthetic
levels first provoke blockade of
inhibitory neurons in the cortex which
leaves the excitatory pathways
unrestrained this explains the twitching
hallucinations and seizures that
characterize neurotoxicity at a higher
threshold plasma level the excitatory
neurons get blocked too resulting in cns
depression and coma in the heart we see
sodium channel blockade of conducting
fibers which provokes either bradycardia
or reentrant tachyarrhythmias there's
also a direct myocardial depressant
effect from calcium channel blockade and
interference with the myocardial sodium
calcium channel pump add on to that the
mitochondrial poisoning and you can see
how the heart muscle begins to fail fast
now we have an antidote for this
poisoning fat specifically a 20 emulsion
of triglycerides and phospholipids it's
amazing for its sheer effectiveness at
reversing the toxic changes after local
anesthetic poisoning and the fact that
it's cheap and plentiful makes it all
the more attractive so how does lipid
emulsion work it's actually multimodal
but the first and principle way it works
is by scavenging lipid soluble local
anesthetic molecules from the heart and
brain tissue and shuttling them to other
tissue depots notably the high mass high
flow skeletal muscle and liver this
lowers the concentration of local
anesthetic at the ion channels in the
heart and brain and when that
concentration drops sufficiently the
tissues can begin to function again
the triglycerides also provide fatty
acid substrate for the poisoned
mitochondria to use providing a little
inotropic kick there's also a volume
effect from the colloidal lipid emulsion
that helps generate cardiac output so it
really does work in a couple different
ways when we think about populations
that may be at higher risk for last the
extremes of age seem to be in that
category elderly people have cardiac
comorbidities that result in a lower
threshold for rhythm disturbances or
pump failure they also have decreased
muscle mass which means they're unable
to use that as a neutral reservoir for
local anesthetics babies under six
months of age have decreased muscle mass
too as well as immature hepatic bowel
transformation pathways so plasma levels
of local anesthetic may be elevated
particularly since they also have
reduced concentrations of alpha one acid
glycoprotein a protein that binds local
anesthetics into plasma for both the
frail elderly and children less than six
months of age a dose reduction of local
anesthetic of 10 to 20 percent seems
reasonable
pregnant patients have a reduced
concentration of plasma binding proteins
and increased cardiac output which
translates to a more rapid rise to peak
plasma levels add to that the epidural
venous engorgement from the mass effect
of the uterus and it seems reasonable to
reduce the epidural dose by 10 to 20
percent starting in the first trimester
patients with reduced ventricular
function will be more susceptible to
local anesthetic induced myocardial
depression and they won't clear local as
fast those that already have arrhythmias
are at slightly higher risk for
developing a serious arrhythmia with
last two
coronary disease doesn't seem to be a
risk in and of itself but remember you
need to feed fat to the heart in a
cardiac arrest situation and if that
muscle is poorly perfused because of
sclerotic blockages it will prolong the
resuscitation
we don't want to have to manage last so
it pays to prevent it first off be
conscious of published dose limits there
are obviously downsides to a set of
limits that don't take into account the
site of injection or other patient
factors however they're a good framework
to work from it's scary to see that
there are plenty reports of last with
sub-maximal doses a good rule is to use
the lowest dose possible that gets the
analgesia you need fractional injection
means pausing between each four to five
ml aliquot for 20-30 seconds to allow
the plasma concentration to begin to
fall this is a good safe practice it can
be somewhat impractical with small
volume blocks and will typically do this
for the elderly patient with multiple
risk factors or high volume blocks
always aspirate before injecting each
dose it's not perfect there are some
false negatives but they're rare
epinephrine is used as a marker for
inadvertent intravascular injection we
put it in virtually every local
anesthetic syringe and have had some
good saves where we were obviously
mistaken as to the needle tip position
epinephrine also truncates the peak
plasma level of local anesthetics
and finally use ultrasound we now have
evidence that ultrasound guided blocks
are associated with a significantly
reduced incidence of last over a
non-ultrasound technique so use it
three special situations deserve a brief
mention
fascial plane blocks carry a somewhat
higher risk for last for two reasons one
the target inter-muscular fascial plane
is sandwiched between two reasonably
vascular muscle bellies and so uptake is
relatively quick depending on the
individual block we also use large
volumes such as 80 mils total for a
bilateral set of blocks in these cases
it's wise to dilute the local anesthetic
down to stay well within dosing
guidelines the nerves in these blocks
are generally quite small and easily
blocked with dilute local anesthetic
catheters are wonderful but be aware
that most of the data we have to date
shows that the total plasma levels of
repivocane do continue to rise for the
duration of the catheter and so care
should be taken when planning the
infusion regimen again the least amount
of local possible to get the job done is
the right dose fortunately the alpha-1
acid glycoprotein also rises following
surgery so while the total plasma level
may be high the actual free fraction is
not as high as you might think
special care should be taken with
multiple catheters intravenous laticane
has been the culprit in a number of
serious last cases even in normal doses
over 10 percent of patients report mild
cns or cardiovascular disturbances a
recent international consensus statement
has recommended that infusion rates go
no higher than 1.5 milligrams per
kilogram per hour and only infused for
24 hours a block should not be performed
within 4 hours of starting or finishing
the infusion the worst happened and
you've got a case of last what are your
first steps
first stop injecting the offending
poison call for help and if you have a
lipid emulsion kit prepared call for
that specifically maintain the airway
and if necessary ventilate the patient
the seizure produces a profound
hypercarbic state which vasodilates the
cerebral arteries promoting the delivery
of the very agent we want to avoid to
the brain you want to aim for eucapnia
or slight hypocapnia stopping the
seizure is important and benzodiazepines
are the first line two milligrams of
midazolam is usually sufficient purple
fall should be used sparingly as it will
have a negative effect on blood pressure
and cardiac output at this point you're
going to want to give the lipid i
recommend delegating one individual to
manage the lipid portion of the recess
direct him or her to withdraw 1.5 mils
per kilo using some big syringes this is
your bolus dose and you want to get it
in quick once the bolus is finished
direct him or her to start the infusion
at 0.25 mils per kilo per minute up to
two more boluses of the same dose can be
given if needed and the infusion rate
doubled if there's refractory
hypotension but the maximum dose is 12
mils per kilo
now doing math in the middle of a crisis
is no fun so here's an easy math free
version that will approximate your bolus
and infusion assuming an ideal body
weight of 70 kilos 100 ml bolus and a
thousand mils per hour on the pump in
the heat of the recess just get things
going with those two settings and then
once the dust has settled you can fine
tune your infusion if needed lipid
emulsion is very well tolerated and
there are sufficiently few side effects
that most experts recommend giving it at
the first hint of last you may over
treat some patients who are false
positives but given that last can
progress quickly you really don't want
to take that chance if you have the
clinical suspicion give the lipid it's
nice to have your lipid and the
instructions in one place here's an
example from lipidrescue.org where the
lipid is in a sealed box with
instructions pasted to the top
in a cardiac arrest setting everything
else is the same but you'll want to
carry on with standard acls standard
except for the following don't use a
milligram of epinephrine all it does is
provoke arrhythmias wildly increased
cardiac work impairs gas exchange and
provokes a rise in lactate the goal here
is to get flow of lipid through the
coronaries so chest compressions are key
don't use a vasopressin as it has been
shown to worsen outcomes and obviously
you wouldn't use lidocaine to treat
arrhythmias in the setting of last and
similarly don't use meds that reduce the
ionotropy or av conduction
once you've had the patient back and
stable for 10 minutes you can stop the
lipid infusion if the patient has
experienced cardiovascular compromise he
or she should be monitored for at least
six hours to ensure the heart and brain
are no longer at risk from
redistribution if there were only
neurologic manifestations two hours is
enough if the episode was brief and not
severe it may be best to proceed with
surgery especially if the patient has
already been blocked and the block is
sound on the other hand in cases where
the patient is not responding to these
measures consider calling in the cavalry
and getting cardiopulmonary bypass or
ecmo deployed here's a flowchart for
last management from the american
society of regional anesthesia and pain
medicine and this is a similar guideline
from the association of anesthetists of
great britain and ireland both are very
similar last is a terrible complication
of local anesthetic use that with the
right preventive strategies and
vigilance can be avoided make sure
you're prepared in any setting you use
local anesthetics
you
Посмотреть больше похожих видео
Dengue Fever Treatment (Dengue Hemorrhagic Fever) Symptoms, Rashes, Diagnosis, Management Lecture
Bronquiolite - Aula de Pediatria do Curso Intensivo Residência Médica
CH05. L02. Test planning overview
Risiko Kritis #8 Bekerja dengan Panas
Overview of Heat-Related Illnesses | NEJM
Childhood Injury Prevention -- Focus on the Cause: Energy Transfer
5.0 / 5 (0 votes)