Toxicology Flashcards
What is “evidence-based” analysis?
- to identify at an early stage those who are most at risk of developing serious complications
- to identyfy who might potentially benefit from decontamination, elimination techniques
Principles of managing the acutely overdosed patient
- do not focus on ingredients listed on the container of the product
- do not focus on specific antidote
- more rational individualized early treatment
- treat the patients, not the poison - rapid clinical management plan
Explain the general evaluation protocol in poisoned/overdosed patient
The 5 W’s in taking patient history?
- Who - age, weight, relationship
- What - name and dosage of medication(s)
- When - the time and date of ingestion
- Where - route of poisoning and geographical location
- Why - intentional or unintentional
Which drugs are known as “date-rape drugs”?
- Rohypnol (benzodiazepine)
- GHB (γ-hydroxybutyrate)
First thing to do when you get an overdosed patient?
Stabilize! Do your ABCDE’s!
Important Rule-Outs in an overdosed patient?
ATOMIC
Alcohol: check ethanol lvl
Trauma: consier CT scan
Overdose: drug lvls, other drugs involved?
Metabolic: ABG, Na, K, glucose, Thyroid, creatinine, etc
Infection: consider blood values
Carbonmonoxide: obtain COHb lvl
What is the protocol for empirical treatment of coma patient?
- Give Oxygen/ventilation if sat% is low
- Nolaxone (2.0mg in adults)
- Thiamine 100mg (BEFORE glucose)
- Glucose 50% IV 50ml (or 1 mg glucagon if you can’t place PVK)
Why do we give thimine before glucose?
To prevent risk of Wernicke’s encephalopathy
Nolaxone, when should you consider giving it?
When there is a sign of respiratory og CNS depression
How is Nolaxone dosage considered?
- Adult: 2.0mg (repeated every 2 min, total dose 10mg)
- Children > 5 years + respiratory depression: 2.0mg
- Children > 5years - respiratory depression: 0.1 - 0.8 mg
- Children < 5 years: 0.1mg/kg
- Narcotic-dependent patients: 0.1mg, doubled every 2 min, total dose 10mg
Explain the typical toxologic physical exam
- Mental status: agitation, confusion, coma, reflexes
- Pupils: pupils size, nystagmus, reactivity, increased lacrimation
- Bowel: sounds, tenderness or rigidity
- Muscle: tone, activity, coordination
- Skin: dry or diaphoretic, bruising, cyanosis, flushing
- Lungs: bronchorrhea or wheezing
- Cadriovascular: rhythm, rate, regularity
Based on these consider type of Autonomic Syndromes
What are Autonomic Syndromes?
Dysfunctions within the autonomic system with either procholinergic or anticholinergic side effects.
What are toxidromes?
Clusters of symptoms that may suggest particular classes of substances bein the cause of poisoning/overdose.
Name the types of toxidromes
- Sedative-hypnotic toxidrome
- Anticholinergic toxidrome
- Cholinergic toxidrome (muscarinic)
- Cholinergic toxidrome (nicotinic)
- Opioid toxidrome
- Sympathomimetic
- Withdrawl
- Thermal
Sedative-hypnotic toxidrome, symptoms and causes?
Anticholinergic toxidrome, symptoms and causes?
Cholinergic toxidrome (muscarinic), symptoms and causes?
Cholinergic toxidrome (nicotinic), symptoms and causes?
Opioid toxidrome, symptoms and causes?
Sympathomimetic toxidrome, symptoms and causes?
Withdrawl toxidrome, symptoms and causes?
Thermal toxidrome, causes behind hyper- & hypothermia?
Why do certain toxic substances show delayed signs?
The delay may occur because only the metabolite is toxic rather than the parent substance (eg, methanol, ethylene glycol, hepatotoxins etc…)
What is the routine lab-test for intoxicated patients?
- ABGs
- complete blood cell count
- serum electrolyte
- glucose levels
- chemical screen with hepatic and renal function studies
- serum osmolarity may be helpful if poisoning with methanol, ethylene glycol or isopropanol is suspected.
When should you take chest radiographs?
If you suspect:
- aspiration
- coma
- ingestion of substances that may cause non-cardiogenic pulmonary edema
What do you especially need to be conserned about when treating a patient that unintentially overdosed while working as a drug-mule?
Monitor blood lvls of the substance and be sure that levels are sustainly decreasing, a sudden increase could be a sign of reexposure (rupture of unremoved hidden drug pouch in the GI)
What is Ipecac and what can it do?
- A syrup that can induce vomiting by irritating GI mucosae and stimulate chemotrigger zone of the brain
- May be used to remove ingested poisons/drugs
- 30ml for adults, 15ml for children
- Most common side effect is vomiting lasting >60 min
(although prolonged vomiting could also be caused by the toxin)
Contraindications for using Ipecac?
- ingestions with potential for change in mental status
- active or prior vomiting
- corrosives and volatile poisons
- heart disease patients
- pregnant women
- toxin with more pulmonary than GI toxicity
- ingestion of toxins with potential for seizures (aspiration pneumonia)
According to the AAPCC, at what circumstances should Ipecac be used at all?
Only indication for Ipecac use at home is if there would be a delay of 1 h or more before a patient (adult) could get to an Emergency Department (and even then, only if it could be administered within 30-90 min after the ingestion)
Home-use of ipecac in pediatric patients is not recommended!
Indications for Gastric Emptying/Gastric lavage?
- Must be done within 1h of ingestion
- If the drug contains on of the following:
- hydrocarbon
- benzene
- toluene, camphor
- halogenated hydrocarbons
- pesticides
- heavy metals
- If the drug is liquid: more than 4ml/kg has to be ingested
What is Gastric Lavage?
- A type of Gastric Emptying procedure
- Flexible tube is inserted through the nose into the stomach
- Size: > 36 French for adults or 22-24 French for children
- Used for retrieving tablet fragments
How is the Gastric Lavage procedure done?
- Before nose insertion, measure from chin to xiphoid and confirm with air insufflation
- Because lavage sometimes forces substances farther into the GI tract, a 25g dose of charcoal is instilled through the tube first
- Lavage continues until the withdrawn fluids appear free of the substance (usually 500 - 3000ml), while small aliquits of lavage fluid are repeatadly introduced into the stomach by gravity
- After lavage, give a 2nd dose of 25g charcoal
When is gastric lavage contraindicated?
- no patient’s agreement
- large pills
- nontoxic ingestion
- non-life threatening
- most hydrocarbons
- airway integrity not secured
- drug is more toxic to lung than GI
What is Activated Charcoal?
- Given when multiple or unknown substances have been ingested
- Absorbs most toxins because of its molecular configuration
- Given at doses of 1-2g/kg, repeat with 4-6h interval
- Given in fluid solution (e.g in a slurry or soft drink)
- Given trough gastric tube in unconcious patients
6.
Which substances do we have to give repeated doses of charcoal (Multi-dose charcoal) for?
Substances that undergo enterohepatic recirculation
- phenobarbital
- carbamazepine SR
- aspirin (enterocoated tablets)
- theophylline SR
- other Sustained-Release products
Which substances is multi-dose charcoal not useful for?
The typical substances that we prefer Gastric Lavage for:
- cyanide
- mineral acids
- caustic
- organic solvents
- iron
- ethanol
- methanol
- lithium
Complications and side effects of active charcoal?
- decreased O2
- nausea/ vomiting
- epistaxis
- insertion into trachea
- aspiration
- fluid and elctrolyte abnormalities
- small bowel obstruction
- pneumonia
What are Cathartics?
- Substance that accelerates defecation
- Consist of either 70% sorbitol 1g/kg or 10 magnesium citrate
- Often given with activated charcoal
- Typically used in WBI (whole bowel irrigation)
How does WBI work?
- A commercially prepared solution of polyethylene glycol (PEG glycol) (which is nonabsorbable) and electrolytes is given at a rate of 1-2 L/h until the rectal effluent is clear
- Usually given through gastric tube
- Benefits of WBI are uncertain, may help for SR drug intox
What is Alkaline Diuresis?
A method of eliminating weak acids by giving a solution of Dextrose, NaHCO3 and KCl
What do we mean when we say Extracorporeal Treatment in toxicology?
Removing toxin by hemodialysis or hemoperfusion
Absolute indications for Extracorporeal treatment?
All of the following must be present:
- Exposition to toxic drug
- Drug must be readily eliminated by ECT
- Evidence of toxicity either (biochemical or clinical sympt)
- Lack of alternative life saving treatments (antidote)
Relative indications for Extracorporeal treatment?
- Deteriorating condition despite optimal therapy
- Problems with renal or hepatic metabolism
Common toxins that may require extracorporeal treatment?
- Ethylene glycol
- Lithium
- Methanol
- Salicylates
- Theophylline
- VPA
- Phenobarbital
In which circumstances is hemodialysis less usefull for removing toxins?
If the poison…
- Is a large or charged
- Has a large volume of distribution
- Is stored in fatty tissue
- Is extensively bound to protein
When do we use hemofiltration or give plasma exchange?
When the liver/kidneys are damaged and need time for recovery/transplantation
A main advantage hemoperfusion has over hemodialysis?
It consists of a filter made of activated charcoal in the dialysis circuit (might help in filtrating large or protein-bound toxins)
Antidote for Acetaminophen (paracetamol)?
N-Acetylcysteine
Antitode for Anticholinergics?
Physostigmine
Antidote for benzodiazepines?
Flumazenil
Antidote for B-blockers?
Glucagon
Antidote for Ca-channel blockers?
- Ca IV
- Insulin with IV glucose
Antidote for Carbametes?
- Atropine
- Pralidoxime
Antidote for Organophosphates?
- Atropine
- Pralidoxime
Antidote for Digitalis glycosides?
Specific Fab fragments
Antidote for Ethylene glycol?
- Ethanol
- Fomepizole
Antidote for Methylene?
- Fomepizole
- Ethanol (if fomepizol is unavailable)
Antidote for Heavy metals?
Chelating drugs
Antidote for Iron intoxication?
Deferoxamine
Antidote for Isoniazid?
Pyridoxine (vitamin B6)
Name the Methemoglobin-forming agents
- Aniline dyes
- Some local anesthetics
- Nitrates
- Nitrites
- Phenacetin
- Sulfonamides
Antidote for Methemoglobin-forming agents?
Methylene blue
Antidote for opioids?
Naloxone
Antidote for Tricyclic antidepressants?
NaHCO3
Antidote for Cyanide?
- Hydroxocobalamin
- Cyanide antidote kit (includes amyl nitrate, Na nitrite, and Na thiosulfate)
What to do if intoxicated patient shows respiratory depression?
First try giving 2mg Naloxone, if it still persists do endotracheal intubation with slow-infusing Naloxone perfusion
What to do if intoxicated patients show altered conciousness?
- FIRST give 100mg thiamine
- Then give 50ml of 50% Dextrose solution
First-choice vasopressor for drug-induced hypotension?
Norepinephrine 0.5-1mg/min
(if the hypotension is refractory, consider other vasopressors)
What to do if patient shows refractory arrythmia?
- Cardiac Pacing
For Torsades de Pointes we can give Magnesium Sulfate 1-2g IV
What to give to intoxicated patient with seizures?
- Benzodiazepines first
- Phenobarbital or phenytoin if benzo doesn’t work
How does acetaminophen (paracetamol) hepatotoxicity occur?
Ocurrs due to metabolism by p450 (mainly CYP2E1) to the hepatotoxic substance NAPQI –> GSH depletion, oxidative stress and mitochondrial dysfunction
What is the Rumack–Matthew Nomogram used for?
Used for estimation of the likelihood of hepatic injury due to acetaminophen toxicity for patients with a single ingestion at a known time
Result of cross reaction between acetaminophen and ACUTE alcohol abuse?
Decreased NAPQI due to ethanol being a competitive substrate of CYP2E1
Result of cross reaction between acetaminophen and Chronic alcohol abuse?
Increased NAPQI due to long ethanol abuse will over time increase number and action of CYP2E1 enzyme
Acetaminophen overdose:
Clinical manifestations - Stage 1
- First 24 hours of ingestion
- Characterized by the non-specific symptoms of nausea, vomiting, malaise, lethargy and diaphoresis
- AST and ALT are usually normal
Acetaminophen overdose:
Clinical manifestations - Stage 2
- 24 to 72 hours
- Characterized by resolution of stage I symptoms
- Elevations of AST and ALT typically begin to occur
- In severe cases:hepatomegaly (with right-upper quadrant pain), jaundice and coagulopathy
- 1∼2% of patients may also experience renal failure
Acetaminophen overdose:
Clinical manifestations - Stage 3
- 72 to 96 hours after ingestion
- Return of stage I symptoms
- AST and ALT elevations
- Maximal liver injury (jaundice, encephalopathy, coagulopathy and lactic acidosis)
- Renal failure, and on rare occasions pancreatitis
- Prolonged prothrombin time
Why do we see lactic acidosis in acetaminophen overdose?
Increase lactic acid in two ways (two-hit increase):
- NAPQI causes hypoxia in hepatic cells –> increased lactic acid
- NAPQI-induced hypoxia in hepatic cells –> decreased lactic acid metabolism –> even more lactic acid buildup!
If a patient survives stage 3, what is the recovery time?
- 96 hours after stage 3 (1-2 weeks from time of ingestion)
- May last longer depen ding on severity
How much acetaminophen is considered to be toxic dose?
> 7.5g of acetaminophen is toxic
Alternative antidote for acetaminophen overdose?
If acetylcysteine is not accessible, give activated charcoal 1g/kg within 4 hours of poison ingestion
Indications for N-acetylcysteine in acetaminophen overdose?
- Acetaminophen lvl above “treatment” line on the nomogram chart
- Single ingestion of greater than 150 mg/kg (7.5 g total dose regardless of weight)
- Unknown time of ingestion and a serum acetaminophen concentration >10 mcg/mL (66 micromole/L)
- Patient with a history of acetaminophen ingestion and any evidence of liver injury
- Patients with delayed presentation (>24 hours after ingestion) + evidence of liver injury or history of previous acetaminophen overdose
Explain the 20-hour IV acetylcysteine dosing regimen
- Administer initial loading dose of 150 mg/kg IV for 1 hour
- Next, administer a 12.5 mg/kg/h IV for 4 hours
- Finally, administer 6.25 mg/kg/h for 16 hours
Explain the 72-hour oral acetylcysteine regimen
- Loading dose of 140 mg/kg
- Then 70 mg/kg every 4 hours (total dose of 17 times)
Side effects of N-acetylcysteine treatment?
- Non-IgE mediated anaphylaxis (when given IV)
- Vomiting (when given oral)
Protocol for acetaminophen-overdosed patient with hepatic failure?
- Choose IV acetylcystein regimen (improves hepatic microcirculatory function)
- Continued until patient recieves transplant or [encephalopathy is resolved and INR <2]
- Additional supportive therapies are also started
Aspirin overdose, mechanism of action?
- Inhibition of COX 1 and 2 decreased synthesis of prostaglandins, prostacyclin and thromboxanes –> platelet dysfunction and gastric mucosal injury
- Stimulation of the chemoreceptor trigger zone in the medulla causes nausea and vomiting
- Activation of the respiratory center of the medulla results in hyperventilation and respiratory alkalosis
- Interference with cellular metabolism (eg, Krebs cycle, oxidative phosphorylation) leads to metabolic acidosis
Body defense-mechanism against aspirin intoxication include?
- Binding to protein (90% of normal dose bind to protein)
- Hepatic metabolism
What happens to body-defense against aspirin when we overdose?
As aspirin lvl rises, the body runs out of enough proteins to bind the aspirin (salisylate) and hepatic metabolism can’t keep up with the large amounts –> elimination becomes dependent upon (slow) renal excretion –> aspirin half-life increase from 2-4h to 30h!
Clinical features of acute aspirin overdose?
- First symptoms present within 1-2h after ingestion
- Early symptoms include hyperpnea (earliest), tinnitus, vertigo, nausea, vomiting and diarrhea
- Afterwards if the overdose is severe, another set of symptoms including altered mental status, hyperpyrexia, noncardiac pulmonary edema, and coma
- Most patient also have either respiratory-alkalosis or a mix of respiratory-alkalosis and metabolic-acidosis
What is the therapeutic range of aspirin dosage and what is a fatal dose?
- Therapeutic range: 10 to 30 mg/dL
- Fatal dose: 10-30g/dL
First signs of intoxication appear as early as 40-50mg/dL
Why can aspirin overdose cause altered mental status?
- Salicylate is directly toxic to the CNS
- Overdose may cause neuroglycopenia
- Overdose may cause cerebral edema
Important side effect that mainly occur in geriatric aspirin overdose?
Salicylate-induced noncardiogenic pulmonary edema
What causes the acid-base abnormalities in aspirin overdose?
- Salicylate directly effects the respiratory center –> hyperpnea –> respiratory alkalosis
- Cell-damage and glycopnea induced by overdose cause buildup of acids (lactic and ketoacids) –> metabolic-acidosis
What is special about the substance aspirin is made up from?
- The molecular design of Salisylic Acid consists of a deprotonated (charged) and protonated (uncharged) form
- The uncharged form can cross lipid barriers meaning it can cross the blood-brain barrier and epithelium of renal tubule
- The lipid soluability means low doses are enough for a cns buildup as it can easyly get reabsorbed in renal collecting tubule and move towards the brain and affect it
How do you treat aspirin overdoes?
By giving sodium bicarbonate (NaCOH3 ): Increasing the systemic pH increases the charged/uncharged ratio of salisylic acid, more uncharged means less lipid soluability (less cross blood-brain, and less are reabsorbed in the renals)
- Initial dose of NaCOH3 1-2mEq/kg IV
- Then: 100-150 mEq NaCOH3 in 1L 5% dextrose solution
- Keep going until Serum Salicylate <40mEq/kg
- Give Potassium even if patient doesn’t have hypokalemia as alkanization will further decrease serum potassium
Diagnostic testing methods for aspirin overdose?
- Serum Salicylate lvl - >40 mg/dL (2.9 mmol/L)
- Serum Creatinine lvl - (aspirin is excreted through kidneys)
- Serum potasium - chance of hypokalemia
- Prothrombin time - overdose may cause hepatotoxicity –> interfere with Vit K metabolism
- Serum Lactate - Salicylates uncouple oxidative phosphorylation –> increased anaerobic metabolism
- Anion gap - often elevated with overdose
Further management of aspirin-overdosed patient?
- ABCDE (stabilize!)
- Tracheal intubation ONLY IF NECESSARY (patient has respiratory alkalosis to manage the low pH and we must try to not disturb this natural management)
- If hypotensive give fluids, unless patient has cerebral edema or pulmonary edema
- Activated Charcoal within two hours of ingestion (1g/kg, 50g total dose)
- Give glucose solution despite normal blood glucose (as cerebral glucose lvls are often low)
Aspirin-overdosed patient with respiratory alkalosis, should you treat with bicarbonate?
Yes! Respiratory alkalosis is not a contraindication of treatment, just keep serum pH <7.6
Patient with aspirin overdose has low serum pH but large urinary flow, is your treatment working?
No, urinary flow is not beneficial to remove salicylate unless the pH is normal or high (when it’s low, most salicylate gets reabsorbed), give more NaHCO3
Indications for hemodialysis in aspirin.overdosed patient?
Patient has one or more of the following:
- Altered mental status
- Pulmonary edema due to respiratory distress
- Cerebral edema
- Acute or chronic kidney injury
- Fluid overload that prevents HCO3 administration
- Very high serum salicylate (>90mg/dL)
- Severe acidemia (pH <7.2)
How do NSAIDs differ from aspirin in what they inhibit?
NSAIDs prevent COX-mediated production of prostaglandins and thromboxanes but not leukotrienes and other eicosanoids (while Aspirin does!)
COX-1 vs COX-2 function?
COX-1: Expressed in most tissues and regulates basal cellular homeostasis (platelet function, gastric mucosal integrity, and regulation of renal blood flow)
Cox-2: Regulates inflammatory cytokines and pain
Pharmacokinetics of NSAIDS?
- They are weak acids
- Peak serum lvl within 1-2h, overdose ight cause delay of 3-4h
- 99% becomes protein-bound, and 1% is free (ratio changes during overdose, too few proteins to bind it all)
- Metabolised in the liver, then excreted through the kidneys
- Half life differ based on type (either over or under 8h)
Name the short half-life NSAIDs (<8h)
- Ibuprofen
- Indomethacin
- Ketorolac
- Diclofenac
Name the long half-life NSAIDs (>8h)
- Naproxen (shortest of them)
- Oxaprozin
- Piroxicam)
- Phenylbutazone (longest of them)
How much NSAIDs must be ingested for signs of toxicity?
> 100mg/kg (except mefenamic acid and phenylbutazone)
Most common symptoms include:
- Nausea and vomiting
- Drowsiness
- Blurred Vision
- Dizziness
(at this lvl, very few show severe harm or need treatment)
Which other drugs must you always rule out before suspecting NSAID overdose?
Aspirin and acetaminophen! People often mistake them for being NSAIDs and initial overdose-symptoms may be similar.
What are more severe clinical signs of NSAID overdose and how much must be ingested for them to show?
Severe toxicity at ingestion >400mg/kg
Symptoms:
- Anaphylaxis (especially in asthma & urticaria patients)
- Increased anion gap
- Lactic acidosis and weak-acidic metabolites
- Cardiac Dysrythmias (due to acidosis)
- Electrolyte disturbance (due to acidosis)
- Seizures and mental status change (due to acidosis)
- Acute renal failure/necrosis (very rare)
- Hypotension/cardiovascular collapse (ibuprofen)
- Anemia or agranulocytosis (phenylbutazone and indomethacin)
Which lab-measurments do you want to take for NSAID-overdose patient?
- Rule out aspirin and acetaminophen ingestion (check blood levels!)
- CBC and Hb lvls (in case of NSAID-induced bleeding)
- Renal function test in severe cases
- Routine ABG if mental status changes (rule out acidosis)
Serum NSAID lvl is of no value, we monitor symptoms rather than NSAID blood lvl, as even high doses might not cause as severe symptoms as mentioned above
Management of NSAID overdosed patient?
- ABCDE first
- Activated Charcoal within 2h of ingestion
- Correction of metabolic acidosis
- Crystalloid in case of hypotension
- Benzodiazepines in case of seizures
- External warming in case of hypothermia
*Extracorporeal removal is ineffective due to high protein binding
What are dihydropyridines?
- Calcium Channel Blockers
- Mainly affect smooth muscle
- May cause reflex-tachycardia (due to smooth muscle relaxation causing hypotension)
Examples of Dehydropyridines?
- Amlodipine
- Felodipine
- Nicardipine
- Nifedipine
What are Nondehydropyridines?
- Calcium Channel Blockers
- Affects myocardial muscle and smooth muscle
- Cause myocardial depression and decreased electrical activity
Examples of Nondehydropyridines?
- Diltiazem
- Verapamil
Special effects to note about Calcium channel blockers
- At high doses, can block sodium channels –> QRS prolongation
- Often affect pancreas –> decreased insulin release –> hyperglycemia
Signs of Calcium Channel Blocker overdose?
- Hypotension (the main sign of both types)
- Bradycardia (in nondehydropyridines + nifedipine)
- Reflex-tachycardia (only in dehydropyridines)
- Jugular venous distention and respiratory crackles (and other clinical signs heart failure)
Types of treatment for Calcium channel blocker overdose?
- Antidotes
- Decontamination therapy
- Adrenergic agents
- High-dose Insulin Euglycemia Therapy (HIET)
- Invasive therapy
- Intralipid therapy
Antidotes for Calcium channel blockers?
- Calcium salts:
- Calcium chloride 10-20ml 10% solution over 10 min
- Calcium gluconate 30-60ml 10% solution
(both can also be repeated once and given continuously)
- Glucagon: 5mg IV (can be repeated twice with 10 min interval)
Explain decontamination therapy for CCB overdose
Give a combination of the following:
- 50g Activated Charcoal
- IV fluids
- Atropine 1mg IV (can be repeated until total 3mg)
What do you give if CCB overdose patient still has hypotension after fluids are given?
Give vasopressors, especially adrenergic agents (norepinephrine, dopamine etc…)
Explain High-dose Insulin Euglycemia Therapy (HIET) for CCB overdose patients
Give the following combination (insulin-glucose):
- Insulin bolus 1 U/kg IV. then continuous 0.5–1 U/kg/h
- Dextrose 25-50g bolus, then continous 0.5g/kg/h
Invasive methods of managing CCB overdose?
- Transvenous pacing
- Intraaortic balloon pump
- Cardiopulmonary bypass
- Extracorporeal membrane oxygenation
Explain Intralipid therapy for CCB overdose patients, and how does it help?
20% Lipid emulsion is given bolus of 1.5ml/kg, then continous 0.25ml/kg/min
Helps in three ways:
- Makes an intravascular fatty compartment that absorbs some of the CCB
- The free fatty acids are an alternative energy source for myocardial cells
- The triglycerides prolong myocardial calcium channel opening –> increased myocardial Ca2+ concentration
Explain the 3 types of B-receptors
B1: Found in heart muscle, activation causes:
- Increased HR and contractility
- Increased AV conduction
- Decreased Av-node refractory period
B2: Found in heart, but mostly in bronchial and vascular smooth muscle. Activation causes:
- Vasodilation
- Bronchodilation
B3: Found in the heart and adipose tissue, activation causes:
- Reduced cardiac contraction
- Catecholamine-induced thermogenesis
Results of non-selective B-receptor blockade?
- Bronchoconstriction
- Decreased gluconeogenesis
- Decreased insulin release
Results of B1-receptor blockade?
- Decreased myocardial contractility
- Decreased automaticity in pacemaker cells
- Decreased AV-node conduction
Signs of B-blocker overdose?
Occur within 2-6h, but can take upto 24h in SR types and sotalol
- Bradycardia
- Hypotension
- Mental status change and seizures (specially in hypotension)
- Bronchospasm
- Hypoglycemia
ECG changes due to B-blocker intake?
- PR prolongation (due to decreased AV-node conduction)
- RR prolongation (due to bradycardia)
- QRS prolongation (due to overall decreased conduction)
- Significant QTc prolongation (sotalol antiarrythmatic effect)
Treatment of B-blocker overdose patient?
Glucagon IV 5mg over 1min, if no increase in pulse or BP after 10-15min, give 2nd bolus of 2-5mg over 1h
(Atropine and isoprotenerol might also help, but are inconsistent)
Why is Glucagon the chosen B-blocker antidote?
Because glucagon receptors activate the same secondary messenger system as B-receptors
Management protocol for B-blocker poisoning?
- Secure the airways
- Give ALS if necessary
- Establish IV access and heart monitoring
- Isotonic fluid to correct hypotension
- Treat bradycardia with Atropine 0.5-1mg IV every 3-5min, total dose of 0.03mg/kg
- IV glucagon treatment protocol (main antidote)
- NaHCO3 or Magnesium in case of arrythmia
- IV calcium salts
- Vasopressors
- HIET
- Lipid Emulsion Therapy
Explain Calcium Salt management of B-blocker overdosed patient
- Calcium chloride IV 10ml of 10% solution through CVK
- Calcium gluconate 30ml of 10% solution through PVK
Benefits of HIET in B-blocker overdose patients?
Myocardial cell benefits due to the insulin:
- increased glucose and lactate uptake by myocardial cells
- improved myocardial function without increased O2 demand
- increased pyruvate dehydrogenase activity –> increased myocardial lactate oxidation –> better Ca2+ handling
Myocardial cell benefits due to the glucose:
- Increased myocardial SR-ATPase activity
- Increased cytoplasmatic Ca2+ concentration
- Incrased Ca2+ entrance into mitochondria & sarcolemma
Side effects of High-dose Insulin Euglycaemic Therapy (HIET)?
- Hypoglycaemia
- Hypokalaemia
- Hypomagnesaemia
- Hypophosphataemia
Effects Digoxin has on the heart?
Increases intracellular Ca2 concentration in myocardial cells. Happens due to Digoxin inhibiting Na-K ATPase –> inhibition of Na-Ca symporter –> more intracellular calcium
Which pre-existing conditions might increase overall Digoxin sensitivity?
- Renal impairment (cause it’s excreted in urine)
- Acid–base disturbances
- Hypokalaemia
- Hypomagnesaemia
- Hypercalcaemia
- Myocardial ischaemia
- Hypoxaemia
Clinical signs of Digoxin overdose?
- Lethargy
- Confusion
- GI symptoms
- Visual symptoms
- Cardiac arrythmias (might be deadly)
The classic ECG sign found in Digoxin-overdosed patients?
Reverse ticks: downsloping ST depression
Other conduction abnormalities typical for Digoxin overdose?
- Premature Ventricular Contractions (PVCs)
- Sinus bradycardia
- Overall decreased conduction
The main antidote for Digoxin overdose?
Digoxin-spesific antibody fragments