SYSTEMIC COMPLICATIONS OF LOCAL ANAESTHESIA

PREAPARED BY:PARTH AND SHEFALI

SYSTEMIC COMPLICATIONS OF LA

• Drugs have 2 types of effect when administerd.

• 1)Desirable=Actions may be sought ,beneficial.

• 2)Undesirable=Actions may be additional,not sought.

• Basically 3 principles are their..

• 1)NO DRUG EVER EXERTS A SINGLE ACTION.

• 2)NO CLINICALLY USEFUL DRUG IS ENTIRELY DEVOID OF TOXICITY.

• 3)THE POTENTIAL TOXICITY OF A DRUG RESTS IN THE HAND OF THE USER.

PRINCIPLE-1

• If we follow this route so it helps to produce the desirable actions.

• The way from starting to till the end is given below.

• Right drug>Right dose>Right route>Right patient>Right time>Right reason.

• Because of this clinical requirements the drug is not suppose to exert the desirable actions in all the patients.

PRINCIPLE-2

• It says that all the drugs have 2 effect.

• 1)TOXIC

• )NON-TOXIC

• If the drug is properly handeled it may produce non toxic effect.

• If not properly handeled it may harmful or toxic.

• For nontoxic effect=we have to take the precautions

PRINCIPLE-3

• It based on the patient’s health or the past medical history.

• Because different people have different reactivity to the drug.

• So must ask questions or about past medical and drug history before giving to the patient.

MAIN TOPIC

• Mainly in this chapter we have to study briefly about the topic given below.

• 1)OVERDOSE

• 2)ALLERGY

• 3)IDIOSYNCRASY

OVERDOSE

• It is a clinical sign and symptom which is responsible for absolute or relative overadministration of drug.

• All the drugs are poision when its given with inadequate dose.

• First the drug gain accessin the circulatory system in quantities to produce adv on the various tissues.

• There is constant absorption of the drug occurs from site of administration.

• Steady removal is also occurs from the blood.

• This steady state can be alter.

La overdose:predisposing factors

Patient factors

• 1)AGE

• 2)SEX

• 3)OTHER DRUGS

• 4)WEIGHT

• 5)PRESENCE OF DISEASE

• 6)GENETICS

• 7)MENTAL ATTIYUDE

Drug factors

• 1)VASOACTIVITY

• 2)CONCENTRATION

• 3)DOSE

• 4)ROUTE OF ADMINISTRATION

• 5)RATE OF INJECTION

• 6)VASCULARITY OF INJECTION SITE

• 7)PRESENCE OF VASOCONSTRICTORS

Patient factors

• 1)AGE:• ADR occurs in any person with any age.• The functions like absorption distribution and secretion

are not properly devloped and in old age its get diminshed.

• 2)WEIGHT:• Greater the body weight:More tolerance power

produce against the overdose.• Maximum recommended doses can be calculated on

the basis of miligram of drug per kilogram or pound of body weight.

• 3)SEX:• In humans the only instance of sexual difference affecting a

drug response is pregnancy.• During pregnancy renal functions are disturbed.• There is a impaired excretion of certain drugs their

acccumulation in the blood and increased risk of overdose.• 4)PRESENCE OF DISEASE• Disease may affect the ability of the body to transform a

drug into inactive product.• Hepatic and renal dysfunction impair the body’s ability to

breakdown and excrete the local anaesthetic leading to an increased anaesthetic blood level whereas congestive heart failure decreases liver perfusion therby increasing the half lives of amide local anaesthetics and increasing the risk of overdose.

• 5)Genetics:

• It may alter the patient’s response to certain drugs.

• A genetic deficiency in the enzymw serum pseudocolinstearase is an imp.ex.

• This enzyme produced in liver>circulates in blood>responsible for the biotransformation of the ester local anaesthetics.

• A deficiency in this enzyme either quantitative or qualitative can prolong the half life of an ester local anaesthetic and increase its blood level.

• MENTAL ATTITUDE AND ENVIROMENT:

• A patient’s psycological attitude influence the ultimate effect of a drug.

• It affects the patient’s response to various stimuli.

• The apprehensive patient who overreacts to stimulation is more likely to receive a larger dose of local anaesthetic.

• Local anaesthetic seizure threshold is lower in patients who are fearful and apprehensive than in nonfearful patients.

DRUG FACTORS

• 1)VASOACTIVITY:

• All the LA have vasodialating properties.

• INJ in to soft tissues increases perfusion in the area, so greater absorption occurs in from the site of inj in to cvs.

• 2 undesirable effects are their.

• 1)short duration of clinical LA.

• 2)increased blood level of local anaesthetic.

2)CONCENTRATION:• Greater the concentration of the local anaesthetics

administered ,greater the number of mg/ml of solutions and greater the circulating blood volume of the drug in the patient.

• 3)DOSE:• Larger the volume of a local anaesthetic ,the greater

number of mg is injected and the higher the resulting circulating blood level.

• High blood levels of the local anaesthetic can be achieved in dental situations because of the greater vascularity of the intraoral injections site or intravascular injection.

• 4)ROUTE OF ADMINISTRATION:• LA used to control pain.• Drug should not enter in the cvs and reach to the

minimum therapeutic blood level.• LA administered for anti-dys-rhydhmic purposes

must reach a therapeutic blood level to be effective .• One factor involved in pain control by a LA is

diffusion of the drug out of the nerve tissues ,absorb into the cvs and removal from the area of injection.

• Absorption of LA by OMM is dangerous because of the rate at which some topically applied anaesthetics enter the circulatory system.

• Example:lidocaine,tetracaine.

• 5)RATE OF INJECTION:

• Very important factor in the causation or prevention of overdose reactions.

• Acc to author rate of injection is the single most factor.

• IV injection may or may not produce signs and symptoms of overdose.

• The rate is most imp factor which determine that the effect of the drug which will be clinically safe or hazardous.

• 6)VASCULARITY OF THE INJECTION SITE:

• Greater the vascularity of the inj site ,more rapid the absorption of the drug from that area in to the circulation.

• Oral cavity is the highly vascular in entire body.

• Some areas within the oral cavity that are less well perfused ,these areas are more recommended than any other more well perfused areas.

• 7)PRESENCE OF VASOCONSTRICTORS.

• The addition of vasoconstriction to a local anaestheticproduces a decrease in the perfusion of an area and a decreased rate of systemic absorption of the drug.

CAUSES

• 1)BIOTRANSFORMATION OF THE DRUG IS UNUSUALLY SLOW.

• 2)THE UNBIOTRANSFORMED DRUG IS TOO SLOWLY ELMINATED FROM THE BODY THROUGH THE KIDNEYS.

• 3)TOO LARGE A TOTAL DOSE IS ADMINISTERED.

• 4)ABSORPTION FROM THE INJECTION SITE IS UNUSUALLY RAPID.

• 5)INADVERTENT INTRAVASCULAR ADMINISTRATION OCCURS.

• 1)Biotransformation and elmination.

• Ester local anaesthetics as a group undergo more rapid biotransformation in the liver and blood than the amides.

• Plasma pseudocolinstearase is primarily responsible for their hydrolysis to PABA.

• Atypical colinstearase represent a relative contraindication to the administration of ester local anaesthetics .

• Amide local anasthetics may be used without increased risk of the overdose in patient with pseudocolinstearase.

• A low average dose is also causes the problem of overdose if the liver functions are comprised.

• Excessive total dose:in excessive dose all drugs are capable to produce overdose reactions.

• Biological variability has a great influence on the manner in which persons respond to drug.

• The maximum recommended dose of parenterallyadministered drugs is commonly calculated after consideration of a number of factors including,

• 1-patient’s age: age increases the tolerance to the drug is decreased.

• 2-patient’s physical status:for medically compromised patients the calculated MRD is low.

• 3-patient’s weight:The larger the person the greater is the distribution of the drug.

RAPID ABSORPTION IN TO THE CIRCULATION

• Vasoconstricting drugs are considered an integral component of all local anaesthetics whenever depth and duration of anaesthesia are important.

• Vasoconstrictor increases the duration of anaesthesia and reduce systemic toxicity of most local anaesthetics by delaying their absorption in to the cvs.

• The ADA and AHA summerised thid as follows:• “vasoconstrictor agents should be used in local anaesthetic solutions

during dental practice only when it is clear that the procedure will be shortened or the analgesia rendered more profound.

• When vasoconstrictor is indicated extreme care should be taken to avoid IV INJECTION.

• Serious overdose reaction have been reported after topical application of amide local anaesthetic.

• The area of application of a topical anaesthetic should be limited.

INTRAVASCULAR INJECTION

• IV INJECTION may occur with any type of intraoral nerve block but is more likely with following:

• Nerve block: positive aspiration

• Inferior alveolar: 11.7%

• Mental or incisive 5.7%

• Posterior sup alveolar 3.1%

• Ant sup alveolar 0.7%

• Buccal 0.5%

• Both IV and interratical injections are capable of producing overdose.

• IA injection can cause retrograde blood flow in the artery as the anaesthetic drug is deposited.

• IV injections within the usual practice of dentistry should not occur.

• With care and knowledge of the anatomy of the area to be anaesthetised and proper technique of aspiration before injecting the anaestheticsolution overdose as a result of inadvertent intravascular injection is minimized.

PREVENTION

• To prevent intravascular injection use an aspirating syringe.

• Use a needle no smaller than 25 guage when the risk of aspiration is high.

• Althought aspiration of blood is possible smaller gauge needles ,there is an increase in resistance to the return of blood into lumen of smaller gauge needles,leadingto an increased likelihood of an unreliable aspiration test.

• Therefor injection technique with a greater likelihood of positive aspiration dictate the use of a 25 gauge needle.

CLINICAL MANIFESTATIONS

• Clinical signs and symptoms of LA overdose appear whenever the anaesthetic blood level in an organ becomes overly high for that individual.

• The rate of onset of signs and symptoms and to an extent their severity correspond to this level.

• First clinical manifestation may be drowsiness which leads up to unconsciousness and respiratory arrest.This is occurs due to lidocainetherapy.

PATHOPHYSIOLOGY

• The blood or plasma level of a drug is the amount absorbed into circulatory system and transported in plasma throughout the body.

• Levels are measured in micrograms/ml.• LA exert a depressant effect on all excitable membranes.• In clinical use LA is applied in particular area of the body

where it produces its primary effect :a reversible depression of peripheral nerve conduction;other effects are related to its absorption into the circulation and its subsequent actions on excitable membranes,includingsmooth muscle, the myocardium, and the CNS.