Toxicology

Question 1

Which substances are dialysable

Answer 1

MNEMONIC PLASMA TV

Phenobarb
Lithium
Acidosis
Salicylates
Metformin
Alcohols
Theophylline
Valproate

Question 2

Which substances do not bind to charcoal

Answer 2

MNEMONIC PHAILS
Pesticides
Hydrocarbons
Acids/alkalis or alcohols
Iron
Lithium
Solvents

Question 3

Modifications to resuscitation for toxicology

Answer 3

-Wear PPE and remove clothing from patient
-treat life threatening tachyarrhythmia with cardioversion
-consider decreased absportion/ enhanced elimination measures
-Identify toxin and give antidote
-Monitor temp
-Standard BLS and ALS if cardiac arrest occur
-Continue resuscitation for prolonged period of time paticularly iin young
-consider ecpr if toxicity reversible

Question 4

Modifications to ALS for hypothermia

Answer 4

-if VF persists after 3 shocks delay further attempts until >30 degrees
-Withhhold adrenaline if < 30 degrees
-increase interval of adrenaline to 6 - 10 minutes- every 3 - 4 cycles between 30-34 degrees
-Normal after that
-resuscitate until K > 12 or 34 degrees

Question 5

Degrees of hypothermia

Answer 5

< 28 is severe- unconscious with vital signs
28-32 is moderate-impaired consciousness and not shivering
32- 35 is mild- conscious and shivering

Question 5

ALS modification in PE

Answer 5

continue for 60-90 minutes after fibronolytic drug given

Question 6

when should 3 stacked shocks be attempted?

Answer 6

-witnessed and monitored arrest where defib immediately available
-time required for rhythm recognition and charging defib is < 10 seconds

Question 7

Components of a toxicology risk assessment?

Answer 7

-agent
-dose
-time since ingestion
-clinical features and progress
-patient factors- weight and comorbidities

Question 8

What are the screening tests required for all toxic ingestions?

Answer 8

-ECG
-BSL
-serum paracetamol level

Question 9

Potential benefits of GI decontamination

Answer 9

-improved clinical outcome
-more benign clinical course requiring lower level of supportive care
-reduced need for other potentially hazardous complications
-reduced hospital length of stay

Question 10

Potential Risks of GI Decontamination

Answer 10

-pulmonary aspiration
-direct administration into lungs by misplaced NGT can be fata
-bowel obstruction or perforation, bezoar formation
-corneal abrasion
-distraction of staff from resuscitation and supportive care priorities
-diversion of departmental resources for procedure

Question 11

2 Methods of GI decontamination

Answer 11

-single dose activated charcoal
-whole bowel irrigation

Question 12

Indications for single dose activated charcoal?

Answer 12

-1-2 hours after administration
-toxic dose
-massive ingestions- salicylates, paracetamol xr, diltiazem or verapamil
-agent must bind to charcoal (not pesticides, heavy metals, acid/alkali/alcohol, iron, lithium, solvents)

Question 13

Contraindication for SDAC

Answer 13

-agent does not bind to AC
-non toxic ingestion
-decreased GCS ( unless intubated)
-corrosive ingestions

Question 14

Dose of SDAC

Answer 14

50gm for adults, 1gm/kg paed

Question 15

Whole bowel irrigation method

Answer 15

–1:1 nursing
-NGT confirmed placement
-PEG-ELS as tolerated up to a maximum 2L/hr in adult
- 25ml/kg/hr paed
-continue irrigation till effluent is clear

Question 16

Indications for WBI

Answer 16

Specific toxic ingestions:
Iron >60mg/kg, Slow release KCL > 2.5mmol/kg, Diltiazem or verapamil XR, arsenic, lead, body packers

Question 17

Contraindications for WBI

Answer 17

-uncooperative patient
-uncontrolled vomiting
-decreased LOC or risk of seizures
-ileus or intestinal obstruction

Question 18

Methods of enhanced elimination

Answer 18

-MDAC
-urinary alkalinisation
-dialysis

Question 19

How does MDAC work?

Answer 19

1. interrupts enterohepatic circulation( prevents reabsorption into biliary system in small bowel)
2. GI dialysis- gut passes across membrane to charcoal down concentration gradient and binds
   —> works for drugs that are small molecule, small volume of distribution, lipid soluble and low protein binding

Question 20

MDAC is indicated in toxic ingestion of which drugs?

Answer 20

-carbamazepine
-phenobarbitone
-Dapsone
-quinine
-theophylline

Question 21

MDAC contraindications

Answer 21

-Decreased GCS
-seizure expected
-bowel obstruction

Question 22

How to give MDAC

Answer 22

• initial dose SDAC (50gm adult or 1gm/kg kid)
  -25gm every 2 hours or 0.5gm/kg paed
  NGT after confirmation in right place
  -check bowel sounds and aspirated before each dose
  -stop if no sounds or high aspirates
  -rarely beyond 6 hours

Question 23

How does urinary alkalinisation work?

Answer 23

-alkaline urine promotes ionisation of acidic drugs and prevents reabsorption across the renal tubular epithelial system
-dug needs to be filtered at glomerulus, have a small volume of distribution and be a weak acid

Question 24

Drugs where urinary alkalinisation is indicated

Answer 24

- salicylates -methotrexate, phenobarbitone, some herbicides

Question 25

Complications of urinary alkalinisation?

Answer 25

Alkalosis hypokalaemia hypocalcaemia fluid overload

Question 26

How to administer Urinary Alkalinisation?

Answer 26

-correct hypokalaemia -give 1-2 mmol/kg IV NaHco3 bolus -infusion of 150mmol NAHCO3 in 850ml 5 % dextrose at 250 ml/kr -add 20 mmol KCl to keep K normal -aim urine ph > 7.5 check Hco3 and K every 2 hours -continue until evidence of toxicity resolving

Question 27

What is the toxic mechanism of iron ingestion?

Answer 27

-**Liberates oxygen free radicals** causing lipid peroxidation of cell membranes and cell death. -Also causes intracellular toxicity due to** mitochondrial damage** and impaired oxidative phosphorylation **--> GI Mucosa-->progressive cellular toxicity give multiorgan effects-->metabolic acidosis from Lactate production due to mitochondrial dysfunction and liberation of free hydrogen ions---Coagulopathy from liver failure and impairment of clotting cascade**

Question 28

What are the stages of iron toxicity?

Answer 28

1- 0-6 hour post ingestion- vomiting diarrhoea and abdominal pain due to corrosive effects if GI system. Can get large GI fluid loss and hypovolaemia. 2.6-12 hours post ingestion-Ongoing absorption and redistribution. GI symptoms may improve with apparent resolution of toxicity. 3.12-48 hours post ingestion- prgressive mitochondrial toxicity resulting in metabolic acidosis, vasodilatory shock and multiorgan failure 4. 2-5 days post ingestion- hepatic failure with jaundice, coma, hypoglycaemia, coagulopathy. High mortality. 5. 2-6 weeks- fibrosis GI tract with strictures

Question 29

Iron dose mg/kg risk

Answer 29

< 20mg/kg- asymptomatic -20-40mg/kg GI Sx -**60**-120mg/kg systemic toxicity >**120mg/kg**- potentially lethal

Question 30

Management Iron overdose- specifics

Answer 30

-AXR- iron preparations are radioopaque Serum iro levels- peak 4-6 hoursand then gets redistributed -WBI required for toxic ingestion- DOES not bind to charcoal -Specific antidote is desferrioxamine

Question 31

Indication for desferrioxamine in iron overdose

Answer 31

-established features of toxicity OR -Serum iron level > 90micromol or 500mcg at 4-6 hours post ingestion Dose is 15mg/kg/hr

Question 32

Life threatening Hydrofluoric acid concentration -BSA %

Answer 32

* 100% HFA to 2.5% BSA * 70% HFA- 8 % BSA * 23% FHA- 11% BSA * ingestion 100ml 65 HSA by adult * any exposure to child can be fatal

Question 33

What is the toxic mechanism of HFA poisining?

Answer 33

-corrosive hydrogen ions cause local tissue injury -cytotoxic fluoride anions caue chelation of Ca and Mg and inhibitis Na/ K ATPase pump **(Low Ca and low Mg and High K)** -Systemic flurosis occours when these anions get to all organs and cause **Liquefactive necrosis**

Question 34

How does HFA posioning present?

Answer 34

Skni exposure: < 15% concentration may not be immediately painful- up to 6 hours later deep unremitting pain develops--> pallor and blanching after several hours--> blistering and tissue loss days Inhalational exposure -immediate onset of mucosal irritation followed by cough, dyspnoea and wheeze--> non cardiogenic pulmonary oedema ingestion -any ingestion can cause corrosive injury- cardiac arrest within 6 hours

Question 35

What does systemic HFA toxicity look like?

Answer 35

-hypocalcaemia -hyopmagnasaemia -hyperkalaemia -prolonged QT -Torsdaes -Cardiac arresy

Question 36

What is the specific treatment of HFA

Answer 36

**For dysrythmia** - Calcium gluconate 10% 20 mmol IV and repeat every 5 minutes aim normal calcium (0.6mmol/kg in kid) - magnesium 10mmol IV (0.05mmol/kg paed) - hyperkalaemia normal management **For pain at site** - 2.5% calcium gluconate gel topically for small areak - local injection calcium gluconate 1gm in 10 ml sub cut - biers block- 10ml calcium gluconate in 40ml saline for forearm exposre- release cuff after 20 minutes - intrarterial infusion- into radial, brachial or femoral arter of affected limb- same as bier block **For inhalational injury** -nebulised 2.4 % calcium gluconate solution DONT use calcium solution on eye for irrigation- cause injury- use water