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Additive vasoconstrictors

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Introduction

The autonomic =vegetative nervous system works without the control of our consciousness.
It is divided into the sympathetic and parasympathetic nervous systems.

The sympathetic nervous system influences the organs and the metabolism resulting in an increase in efficiency:
  • Cardiovascular stimulation
  • Mobilisation of metabolic reserves
  • Inhibition of digestive activities
The parasympathetic nervous system influences the organs and the metabolism resulting in regeneration:
  • Decreased cardiac and circulatory functions
  • Limitation of energy consumption
  • Increase in resorption and digestion
The peripheral transmitters of the sympathetic system are norepinephrine (noradrenaline) and epinephrine (adrenaline).
The transmitter of the parasympathetic system is acetylcholine.
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Effect of sympathetic stimuli on organ structures

The target organs possess different receptors:
α, β1, β2

Organ α β1 β2
Heart  
  • Heart rate ↑
  • Contractility ↑
  • Excitability ↑
  • Conductibility↑
  •  
    Bronchi     Dilatation
    Vessels Contraction
    (skin, kidney)
      Dilatation
    (muscle, liver)
    Gastrointestinal tract Contraction of sphincters   Inhibition of peristalsis
    Skeletal muscles     Glycogenolysis
    Fat tissue   Lipolysis  


    The effect of sympathetic stimulation depends on the receptor distribution of the given organ.

    Vasoconstrictory additives

    Adrenaline

    Adrenaline is a sympathomimetic agent, i.e. it stimulates the sympathetic nervous system.
    It stimulates all types of receptors: α, β1, β2

    Topical administration:
    Vessels in skin and mucous membranes react with vasoconstriction.

    Systemic effects:
    • Increase in all cardiac functions (tachycardia)
    • Increased resistance of peripheral vessels (predominance of α receptors) resulting in an increase in blood pressure
    • Marked bronchial dilatation
    • Predisposition for hyperglycaemia secondary to glycogenolysis
    The following adrenaline concentrations are commonly used in dentistry:
    • 1:100,000 =0.01 mg/mL
    • 1:200,000 =0.005 mg/mL
    Conversion of the maximum dose of 0.25 mg adrenaline:
    1:200,000 means:1g/200,000 mL
    Equivalent to:1,000 mg/200,000 mL
     =1 mg/200 mL
     =0.25 mg/50 mL
     =0.005 mg/mL

    Noradrenaline

    Noradrenaline is a sympathomimetic agent that preferably stimulates α receptors, and only to a lesser extent β1 receptors.

    It leads to pronounced vasoconstriction (α).
    The systemic effects of this vasoconstriction are a reflectory reduction in the heart rate.

    In contrast to adrenaline, noradrenaline has more side effects, such as:
    Headaches, strong hypertension, and bradycardia.
    The side effect ratio of noradrenaline compared to adrenaline is 9:1; therefore, adrenaline should be preferred!

    Derivatives of the hypophyseal hormone vasopressin

    • Felypressin (octapressin), the synthetic analogue of vasopressin
    • Milder effect than catecholamines
    • No systemic cardiac side effects, but increase in blood pressure
    • Suitable for treatment of compromised patients
    • Vasoconstriction via direct effect on smooth muscles in blood vessels
    • Contraindication: pregnancy, due to their labour-inducing effects.
    • Dose: 0.02-0.03 IU/mL
    • Maximum dose: 0.3 IU/treatment

    Mechanism of action of added vasoconstrictors

    All local anaesthetics (LAs) cause vasodilatation that has a longer-lasting effect than analgesia.
    Vasoconstrictors are frequently used as additives to prevent rapid absorption of LA solution from the site of injection and action.
    Advantages:
    • Increased duration and effectivity of anaesthesia
    • Reduced maximum concentration in serum
    • Less blood in area of surgery
    • Total LA dose can be reduced
    • Antagonistic effect to vasodilatation
    Use of added vasoconstrictor in case of cardiovascular disorders

    A strong sympathetic activation may be induced by higher amounts of a vasoconstrictor within a short period of time, or by accidental intravascular injection.
    However, heavy strain or pain may lead to a strongly increased release of endogenous adrenaline which may then exceed the by far lower amount of adrenaline given during dental treatment (Little 2000).
    Therefore, the advantages of local anaesthesia with a vasoconstrictor exceed the presumed or potential dangers and disadvantages.
    If local anaesthetics containing adrenalin are used, the quantity of added adrenaline should be as low as possible (1:200,000).
    The maximum dose of adrenaline as a vasoconstrictor for patients with cardiovascular disorders, however, should not exceed 40 micrograms (8mL of a solution of 1:200,000).
    22.5 microgram adrenaline as addition to local anaesthetics (4.5mL of a solution of 1:200,000) were tolerated well by patients with cardiovascular disorders of different degrees (Niwa, 2001).
    1:200,000 equals 0.005mg adrenaline/mL, or 5µl/mL.
    But: No topical use of vasoconstrictors
    Vasoconstrictors should not be used for local haemostasis in patients with cardiovascular hypertensive agents, neither should adrenaline-containing retraction cords be used.

    Absolute contraindications for using vasoconstrictors

    • Closed angle glaucoma
    • High-rate absolute arrhythmia
    • Tricyclic antidepressants (3-fold increase of the adrenaline effect)

    Limited total dose if vasoactive additives are included

    Caveat: if chatecholamine concentrations of > 1: 100,000 are added, the maximum dose is rather determined by the vasoconstrictor and not by the LA.
    Total dose of epinephrine (adrenaline): 0.2 mg/70kg/treatment =20mL

    Adrenaline intoxication

    Mild intoxication

    Symptoms
    • Increased blood pressure
    • Tachycardia
    • Hypoxia of myocardium (angina pectoris)
    • Heterotopic excitation stimulus (extra systoles, ventricular tachycardia, ventricular fibrillation)
    • Diabetogenic effect (increased blood sugar level)
    • Vegetative symptoms (paleness, agitation, cold sweat)
    • Occasional paroxysmal opposite reactions (bradycardia, vasovagal syncope)
    Measures
    • Administer oxygen via a nasal tube
    • Monitor blood pressure and pulse
    A mild intoxication is transient because of the short duration of action (1-2 minutes).

    Severe intoxications

    Symptoms
    • Sudden paleness
    • Strong agitation, sometimes loss of consciousness
    • Cold sweating
    • Pupil dilatation
    • High rate tachycardia
    • Coronary insufficiency
    • Cardiac and cerebral hypoxia
    • High grade increase in blood pressure, sometimes reflectory fall of blood pressure
    Measures
    • Administration of high oxygen doses via nasal tube
    • Have somebody call the emergency service
    • Obtain venous access
    • Administer two puffs of nitro-glycerine spray