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Matt Van Zetten - PowerPoint Presentation

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Matt Van Zetten - PPT Presentation

ICU SRMO Sodium Bicarbonate use in critical care Metabolic Acidosis Hyperkalaemia Toxicology Cardiac arrest RTA CRRT Others Potential Sodium Bicarbonate Uses NaHCO3 Available in 84 solution 1050100 ml ID: 224828

metabolic nahco3 overdose acidosis nahco3 metabolic acidosis overdose acid cardiac sodium bicarbonate effects arrest moa tca qrs toxic decreased

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Presentation Transcript

Slide1

Matt Van ZettenICU SRMO

Sodium Bicarbonate

- use in critical careSlide2

Metabolic AcidosisHyperkalaemiaToxicologyCardiac arrestRTACRRTOthers?

Potential Sodium Bicarbonate Uses:Slide3

NaHCO3Available in 8.4% solution, 10/50/100 ml1mmol per mlSodibic capsule840mg = 10mmolAlkalinising agent / buffer

Na+ and HCO3- dissociate

HCO3- + H+ -> H2CO3 -> H20 + CO2

Sodium BicarbonateSlide4

Adverse effects:CardiovascularMyocardial dysfunction / decreased cardiac outputArrhythmiasDecreased TPR / hypotensionDecreased sensitivity to catecholamines

Pulmonary vasoconstriction

Neurological

Decreased LoC

Metabolic

Insulin resistanceInhibition of glycolysis

AcidaemiaSlide5

TreatmentCorrection of underlying disorderi.e. hypoxia / sepsis / hypoperfusion / DKAMixed opinion in literature regarding buffer therapyNo evidence that routine buffer use improves outcome

Studies have shown no improvement in myocardial contractility with NaHCO3 administration

Alternative buffers researched, but not in clinical practice

Buffer therapy generally reserved for severe MA

Threshold of “severe” MA varies

Metabolic acidosisSlide6

Based on Base Excess (to correct 50% of deficit)<5kgBE x weight/4ChildBE x weight/6Adult

BE x weight/10

Toxicology / Arrest

1-2 mmol/kg/dose

NaHCO3 DosingSlide7

Increased CO2 loadWorsening of intracellular acidosisHypokalaemiaHypernatraemiaHypervolaemiaHypocalcaemia (decreased ionised Ca)

Metabolic alkalosis

Worsening of lactic acidosis

Decreased O2 delivery to tissues

Decreased acidosis inhibition of anaerobic metabolism

Complications of NaH2CO3 TherapySlide8

Only advised if life threatening and associated with metabolic acidosisFacilitates intracellular shift of K in exchange for extracellular movement of HTemporising measure similar to salbutamol / Insulin

I.E. K >7 with ECG changes + acidosis

HyperkalaemiaSlide9

Toxic effects via: Blockade of fast cardiac Na channelsNoradrenaline reuptake inhibitionalpha blockadeAnticholinergic actionClinically

Tachycardia, QRS / QT / PR prolongation, hypotension

Confusion, drowsiness/coma, fever

Acidosis (mixed)

Hypokalaemia

TCA OverdoseSlide10

NaHCO3 MOA:

Alkalinisation increases TCA protein binding

?Correction of acidosis -> improved myocardial function

?via increasing extracellular sodium

Volume loading

Therapeutic goal

Resolution of hypotension, QRS prolongation

1-2mmol/kg boluses

Target pH 7.5-7.55

NB: Hyperventilation and HTS have also been shown to be effective in reducing QRS prolongation

TCA OverdoseSlide11

Propanolol overdoseChloroquine OverdoseClass 1a / 1c antiarrhythmics overdoseVenlafaxin overdoseBupropion overdose

Therapeutic goals

1-2mmol/kg every 2-3 minutes

Until hypotension and QRS complexes resolve

Cardiotoxicity

from Fast Na channel blockadeSlide12

Toxic effects via:

Direct stimulation of respiratory centre

Increased endogenous acid production

Acidity of salicylate itself

Uncoupling

oxidative

phosphorylation

Inhibiting

Krebs cycle

enzymes

Inhibiting

amino acid synthesis.

Clinically:

Raised anion gap acidosis

Hyperventilation

Hyperthermia

Hypotension

Neurological – Tinnitus / Deafness / N+V / Confusion / Seizures

Salicylate

OverdoseSlide13

NaHCO3 MOA:Enhances urinary drug eliminationIncreases elimination from tissue and serumPrevents redistribution to CNSTreatment Goal

Serum pH <7.5

Urinary pH >7.5

Salicylate OverdoseSlide14

Toxic effects viaToxic metabolites (first enzyme is ADH)(glycoaldehyde, glycolic acid, glyoxylate, oxalic acid)

Deposition of calcium oxalate in tissues (e.g. kidneys)

Clinically

Apparent drunkenness

N+V

Seizures

Coma

Raised anion/osmolar gap metabolic acidosis

Hyperosmolality

ATN / Renal Failure

Ethylene Glycol OverdoseSlide15

NaHCO3 MOA:Correct acidosisIncrease elimination of glycolic acid by kidneysInhibit precipitation of calcium oxalate crystalsTherapeutic Goal:

Metabolic acidosis with an arterial pH < 7.3 should be treated with a sodium bicarbonate infusion to keep the pH between 7.35 and 7.45

Aim for urinary pH >7.0

Ethylene Glycol OverdoseSlide16

Toxic effects via:Metabolism in liver via ADH to formaldehyde -> formic acid

Clinically:

Drunkenness

Headache / nausea / vomiting

Blindness (optic nerve damage)

Drowsiness / coma

Seizures

Raised anion/osmolar gap acidosis

Methanol OverdoseSlide17

NaHCO3 MOA:Correcting metabolic acidosisDecreasing formic acid levelTherapeutic GoalMetabolic acidosis with an arterial pH < 7.3 should be treated with a sodium bicarbonate infusion to keep the pH between 7.35 and 7.45

Methanol OverdoseSlide18

Routine use of sodium bicarbonate is not recommended for cardiac arrest by the ARCStudies have shown no improvement in outcome?Related to worsened intracellular acidosisConsider administration in:

TCA overdose

Hyperkalaemia

Pre-existing metabolic acidosis

Prolonged cardiac arrest

Cardiac ArrestSlide19

ARC guidelines recommend NaHCO3 as 2nd line therapy for several conditionsPEAAs acidosis /hypovolaemia may predispose to PEA

Asystole / Severe Bradycardia

Refractory VF/VT

Cardiac Arrest - APLSSlide20

Distal RTAReduced H+ secretion in DCTNa / K wastingHyperchloraemic MATypically require 1-4 mmol/kg/day of SodibicProximal RTA

Impaired HCO3 reabsorption in PCT

K wasting

May require up to 10mmol/kg/day

RTASlide21

CRRTSlide22

NaHCO3 used as buffer in dialysate fluidCRRT rather than NaHCO3 can be used to treat severe metabolic acidosisAlso useful to dialyse toxins

CRRTSlide23

Preventing contrast induced nephropathyMixed outcomes from research in recent yearsSome trials show decreased AKI with NaHCO3 pre-hydrationMeta-analysis (Eur J Radiology 2009)Many included trials not of high quality

OR for CIN 0.33 with NaHCO3 vs. NaCl

No difference in death / CCF / RRT requirement

Not routinely recommended

Further research ongoing

Other uses?