Calculation of LA dose among patients.pdf

1. Calculation of LA dose
among patients
‫ساندي‬
‫ماجد‬
‫حبيب‬
‫ابراهيم‬
‫محمد‬
‫البغدادي‬
‫هدى‬
‫ايمن‬
‫الرفاعي‬
‫ابراهيم‬
‫محمد‬
‫السيد‬
‫مصطفى‬
‫عزيز‬
‫تيسيلر‬
‫حيدر‬

2. • Patients have a wide variance in body size
• Maximum recommended dose of LA must be calculated to prevent overdose
• LA dose is expressed as a milligram of drug per kilogram of body weight
• Other variables influence appropriate maximum recommended dose as
overweight, under weight
• and cardiovascular complications (medically compromised)

3. Anesthesia
• When it comes to calculating local anaesthesia, three numbers are
essential.
• It is important to note the different units of measurement; they
must be converted.
1. Maximum dose (mg/kg)
2. Concentration(%)
3. Patients weight (kg)
• These 3 variables are used to calculate the maximum recommended
volume of local anaesthetic.

4. Maximum recommended dose
• You have to know the maximum recommended dose for each
drug in relation to healthy patient and medically compromised
patient
• For example, Articaine maximum dose for healthy patient is 7
mg/kg and in medically compromised patient is 4.4 mg/kg
• You also must know the maximum recommended dose of
vasoconstrictor if found in relation to healthy patient and
medically compromised patient
• Epinephrine maximum recommended dose for healthy
patient is 0.2 mg/ visit and for medically compromised
patient is 0.04 mg/visit

5. A table showing maximum
recommended dose of
different drugs

6. Calculate Concentrations:
There are two concentrations to be calculated
• local anaesthetic and adrenaline (if used).
• They require a unit conversion.
Local Anaesthetic Concentration:
Concentration is expressed as a percentage (%) & max safe dose is
mg/kg.
Must convert % to mg/kg by multiplying the % by 10.

8. Calculationof epinephrine
Adrenaline Concentration:
Epinephrine concentrations are expressed as ratios & need to convert to mg/ml.
This can be converted in 2 steps Convert the ratio as a %: 1 in 100 is 1% and 1 in 1000 in 0.1%.
Multiply the % x 10 to get mg/ml.
Example:
how many carpules of 4% articaine and 1:100000 epinephrine can be injected to 70 kg healthy
patient?
Calculation of vasocnstricor ( epinephrine ) dose
-1:100000 epinephrine means 1 gm/ 100000 ml ( 1000 mg/ 100000ml) , equals 0.01 mg/ 1ml
-epinephrine in one carpule 0.01 * 1.8 = 0.018
-maximum epinephrine dose in healthy patient is 0.2 mg/visit
So, 0.2/ 0.018 equals 11.11 carpules
- we can give this number of carpules by giving half the amount of indicated carpules in relation to
drug dose (3.4 carpules ) every half-life till reaching 11 carpules *

9. COMPLICATIONS OF OVERDOSE ANAESTHESIA
Overdosing on local anesthesia is a serious medical concern with
potentially severe complications.
central nervous system (CNS) toxicity
Excessive amounts of local anesthetics can impair the normal
functioning of the central nervous system, leading to symptoms such
as dizziness, confusion, and, in extreme cases, seizures.
Cardiovascular complications
Local anesthetics can affect the heart’s electrical conduction system,
leading to arrhythmias and, in severe cases, cardiac arrest, Rapid and
irregular heartbeats, decreased cardiac output, and a drop in blood
pressure are all potential consequences of local anesthetic overdose.
Respiratory distress
is a critical complication associated with local anesthetic overdose.
The drugs can depress the respiratory center in the brain, leading to
shallow breathing or, in extreme cases, respiratory failure.

10. Management of LA complications:
When LA toxicity is suspected
• 1st step is stabilization of vital signs and call for help
• Then secure airway
• Control seizure .The American society of regional anaesthesia and pain medicine
(ASRA) recommend benzodiazepines as first line of ttt of seizure and when persist
small use of muscle relaxants
• Lipid emulsion (ASRA) recommend starting lipid emulsion therapy at the first sign of
systemic toxicity
• LAs do have the possibility of provoking an allergic reaction can be treated with
diphenhydramine in case of serous reactions use epinephrine or corticosteroids

11. Initial management
Emergency call stop LA injection
Secure air way
Establish i.v. line
Anticonvulsant(benzodiazepine)
Lipid emulsion
Mild cardiac suppression
Anti hypotension (ephedrine ,adrenaline)
anti arrhythmia(atropine)
Lipid emulsion
Cardiac arrest
CPR
ACLS(adrenaline)
Lipid emulsion
Cardiopulmonary bypass

12. references
• Berde CB and Strichartz GR. Miller's anesthesia. 4th ed. Amsterdam (Netherlands): Elsevier Academic Press; c2015. Chapter 36: Local anesthetics; p.
1028-1054.
• Catterall WA, Mackie K. Local Anesthetics. In: Brunton LL, Hilal-Dandan R, Knollmann BC. eds. Goodman & Gilman's: The Pharmacological Basis of
Therapeutics, 13e New York, NY: McGraw-Hill.
• Curtis LA, Dolan TS, and Seibert HE. Are One or Two Dangerous? Lidocaine and Topical Anesthetic Exposures in Children. The Journal of Emergency
Medicine vol 37, No.1, pp 32-9, 2009
• Drasner K. Local Anesthetics. In: Katzung BG. eds. Basic & Clinical Pharmacology, 14e New York, NY: McGraw-Hill.
• Keddis, RN. Chapter 120: Local Anesthetics and Adjuvants. In: Atchabahian A, Gupta R. The Anesthesia Guide, 1e New York, NY: McGraw-Hill.
• Local Anesthetics. In: Butterworth IV JF, Mackey DC, Wasnick JD. eds. Morgan & Mikhail's Clinical Anesthesiology, 6e New York, NY: McGraw-Hill.
• Williams D, Walker J. A nomogram for calculating the maximum dose of local anaesthetic. Anaesthesia.

13. Thank you