A brief account on use of bicarbonate in toxicology. It includes use in sodium channel blocker poisoning, serum alkalisation, urine alkalisation and toxic alcohol. Details in to doses and routes also included.

2. SCOPE
• BACKGROUND
• SODIUM CHANNEL BLOCKADE REVERSAL
• SERUM ALKALIZATION
• URINE ALKALIZATION
• TOXIC ALCOHOLS

3. BACKGROUND
• CO2 + H20 ⇋ H2CO3 ⇋ HCO3
-; + H+
• Antidote to drugs that impair fast sodium channel function
• An alkalinizing agent to manipulate drug distribution and excretion

4. • 8.4% solution 50ml “ampule” containing 50mEq NaHCO3.
• This formulation is alkaline (pH 8.0) and
• Highly osmotic (2000mosmol/kg)
• “Bicarb drip” which is made by mixing 3 ampules (150 ml) of 8.4% NaHCO3 with 850ml
D5W solution.
• A benefit of this mixture is an osmolality that is much more physiologic (300mosmol/kg)

5. SODIUM CHANNEL BLOCKADE
REVERSAL
• Sodium channels are ion channels which have effects primarily on the cardiac and
neurologic systems
• Sodium bicarbonate works to overwhelm these ion channels with increased extracellular
sodium, allowing for higher electrochemical gradients and resolving the channel
blockade

7. TCA OVERDOSE- CARDIOTOXICITY
• Dosing:
• Bolus dosing of 8.4% NaHCO3 ampules is preferred over infusions.
• Start with 1-2mEq/kg bolus and repeat to clinical effect.
• The primary endpoint of treatment is controversial,
• But goal is a QRS <140 msec.
• A pH of 7.5 or greater
• Na+ of 150meq or 155 mmol/l

8. NON TCA NA CHANNEL BLOCKERS
• Lamotrigine, flecainide, propranolol
• Give 1 mmol/kg or 100 mmol bolus every 3-5 minutes PRN to a maximum total of 3
mmol/kg and
• Gently hyperventilate (aim for pCO2 35-45) until a normal pH target range of 7.35 – 7.45 is
reached on ABG.
• The QRS interval often remains unchanged.
• If hypotension persists, add inotropic or vasopressor therapy guided by bedside ECHO

9. SERUM ALKALIZATION
• Salicylates
• Aspirin
• Bismuth salicylate
• Methyl salicylate
• These uncharged weak acids can cross cellular membranes and the blood brain barrier
leading to increased toxicity

10. • Common treatment regiments (no validated dosing)
• Initial bolus of 1-2 mEq/kg of 8.4% NaHCO3 followed by
• A NaHCO3 infusion starting at 200-250cc/hr.
• Goal of therapy is a serum pH 7.4.
• Blood gas 2 hourly
• Until definitive care with hemodialysis is achieved

11. URINE ALKALIZATION
• Salicylates, chlorphenoxy herbicides, methotrexate, phenobarbital, chlorpropamide, and
fluoride is increased after reaching urinary pH levels of 7.5–8.0

13. • Correct hypokalemia.
• Give 1-2 mmol/kg sodium bicarbonate IV bolus.
• Commence an infusion of 150 mmol sodium bicarbonate in 850 ml of 5% dextrose at 250
ml/hour.
• 20 mmol of KCl may be added to maintain normokalaemia.
• Aim for a urinary pH > 7.5.
• Monitor serum bicarbonate and potassium every 4 hours.

14. TOXIC ALCOHOLS

15. • Convert these uncharged acids to their de-protonated and charged conjugate bases,
• Sodium bicarbonate dosing (no definitive standard.)
• 1-2mEq/kg 8.4% NaHCO3 aim for a pH < 7. 3
• The goal of treatment being a physiologic pH of 7.35-7.45.
• This therapy should be noted to be an adjunct in addition to antidote therapy with
fomepizole or hemodialysis, which is the standard of care

16. ADVERSE EFFECTS
• Metabolic alkalosis
• Hypernatremia
• Hypokalemia (due to intracellular shift)
• Hyper-osmolality
• Paradoxical lactic acidosis
• Local infiltration with skin and vascular damage

17. REFERENCES
• Http://www.Emdocs.Net/toxcard-sodium-bicarbonate-for-toxicology-when-to-use-it-and-
why/
• Https://www.Ncbi.Nlm.Nih.Gov/pmc/articles/PMC5591930/
• Https://litfl.Com/sodium-bicarbonate/