Patient History

Patient History : Smoker's melanosis (Photo credit: Wikipedia)

An adequate patient history should be taken. Certain diseases or the concurrent use of some drugs accentuate the undesirable side effects of adrenaline or nor-adrenaline.

Their use is absolutely contra-indicated in the following conditions:

1. Sensitivity to catecholamines.
2. Thyrotoxicosis - Their use is also contra-indicated where the patient is receiving the following drugs:

• Sympathomimetic agents
• Tricyclic antidepressant drugs, MAOI inhibitors.
• Certain general anaesthetic agents (halothane, chloroform, trichlorethylene).

In these conditions felypressin (octapressin) is a safe alternative vasoconstrictor to adrenaline and nor-adrenaline, and may be used in circumstances where adverse reaction to these drugs is anticipated. Felypressin is the vasoconstrictor of choice should one be required in patients with cardiovascular disease and hypertension.

Antidepressants

Antidepressants  - Tricyclic antidepressants. Monoamine oxidase inhibitors (MAOI).
Tetracyclic antidepressants.

Dangers - Interaction with narcotics and catecholamines.

Precautions  - Narcotics - Cautious use of pethidine, morphine, omnopon etc. Catecholamines - Avoid adrenaline, nor-adrenaline; use felypressin.

These may be divided into three categories: 

• Direct stimulants.
• Monoamine oxidase inhibitors.
• Tricyclic antidepressants.

All three categories may cause adverse drug reactions with other drugs.

Reactions to the monoamine oxidase (MAO) inhibitor drugs include hypertensive episodes accompanied by severe headache. Such episodes can be precipitated by sympathomimetic drugs. Administration of sympathomimetic drugs or ephedrine to patients taking MAO inhibitors, or who have taken the within the preceding month, is contra-indicated.

As the widely used tricyclic see these details antidepressant drugs also potentiate the pressor effects of adrenaline and nor-adrenaline, the administration of sympathomimetic drugs in this group should also be avoided.

Standard doses of narcotics, e.g. morphine, pethidine and Omnopon, when administered to patients on MAO inhibitors, may provoke hypertension and an accentuation of their normal depressive effect on respiration: this may result in severe respiratory depression and loss of consciousness.

Felypressin (Octapressin) is the vasoconstrictor of choice for patients taking antidepressants.

Hypoglycaemic Agents

Drugs -  Insulin by injection. Oral hypoglycaemics.

Dangers -  Hypoglycaemia.

Precautions - Aaequate dietary intake to be maintained at all times. Medical consultation. Consider admission to hospital.

Diabetic patients are treated either by diet alone (the elderly, obese diabetic patient) or by diet in combination with an oral hypoglycaemic agent or insulin. Minor dental procedures can be undertaken in most patients with diabetes without any alteration being made to their treatment, but hypoglycaemia may occur in patients taking the longer-acting oral hypoglycaemics if their aental treatment causes them to restrict unduly their usual daily food intake.

Incipient hypoglycaemia may be manifest by slurred speech, aggressive or argumentative behaviour, pallor and sweating. If this occurs, the dentist should cease operating and give the patient a drink containing sugar or glucose.

Insulin treatment also renders a patient liable to hypoglycaemia, while starvation and vomiting may lead to acidosis. The presence of infection may necessitate altered dosage of insulin and increase the incidence of vomiting. This will not only increase the risk of hypoglycaemia, but food deprivation and vomiting will lead to acidosis. For these reasons, diabetics who require insulin must be individually assessed and their medical practitioner must always be consulted prior to treatment. If not admitted to hospital, the diabetic patient should be discharged to the care of a responsible adult.

Dental treatment should be planned to permit adequate dietary intake post-operatively. If this is not possible, e.g. if multiple tooth removal or extensive oral surgery is required, this is a further  indication for admission to hospital.

Indications for admission to hospital for dental treatment are: dental cronulla

• Unstable diabetes.
• Serious infection.
• Those in whom adequate dietary intake cannot be assured.
• Multiple tooth extractions.
• Extensive oral surgery.
• General anaesthesia.

Anticoagulants

Anticoagulants are used to prevent occurrence and recurrence of thromboembolic disease and may also be used following coronary and cerebral thrombosis.

In patients treated with anticoagulants, there is a danger that any trauma may result in prolonged bleeding. The patient's medical practitioner should be consulted prior to performing tooth removal or surgery as in some patients a reduction in the dose of the anticoagulant drug may be required. The aentist should not adjust the dose, nor should vitamin K be used.

Where major dental surgery is to be performed, the patient should be treated in hospital where post-operative supervision is available.

Corticosteroids

Corticosteroias - Maintenance therapy for arthritis, asthma, allergic diseases, ulcerative colitis, eye and skin diseases. Replacement therapy for adrenal and pituitary disease.

Dangers - Inability to respond to stress: provide steroid 'cover'.

A wide variety of diseases are treated with corticosteroids given for long periods of time; in some patients this may result in suppression of the adrenal glands and a resultant inability to respond to stress.
For this reason, while routine dental procedures under local anaesthesia should not require additional steroid cover, consultation with the patient's physician is vital when a general anaesthetic or major dental procedure is contemplated. In these circumstances, when additional corticosteroids are needed, the patient should be admitted to hospital.

The dentist should also bear in mind that corticosteroid therapy may predispose the patient to infection.

Antihypertensive Drugs

The vasoconstrictor of choice in patients with hypertension is felypressin (Octapressin).
Hypertension reduces the patient's ability to maintain a stable blood pressure and the dentist's attention is drawn to the need to take the following precautions:

• A precise history of all patients being treated for 'heart condition' or 'blood pressure', including the type and dosage of drugs taken, should be obtained and evaluated carefully.
  
• Care should be taken in the selection and administration of local anaesthetics, and preparations free of adrenaline and nor-adrenaline should be used. Felypressin is a safe and effective alternative. Where the dentist considers it essential to use adrenaline or nor-adrenaline its concentration should not exceed 1:200 000 (i.e. 5.0 ug/mL) and a maximum  dose of 2 mL (1.0 ug) should be observed. Meticulous care should be taken to avoid intravenous injection.
  
• In addition to their effect on blood pressure some antihypertensive drugs, e.g. Rauwolfia, have a sedative effect, which reduces the dose of sedative drug needed during dental treatment. This should considered when selecting sedatives to allay anxiety.
  
• Undesirable fluctuations in blood pressure may be avoided by using appropriate sedation to reduce anxiety.
  
• Patients with hypertension may develop respiratory distress in the supine position; they may need to be treated in a more upright position. Sudden changes in position should be avoided, but if the blood pressure falls, the patient should be placed in the horizontal position.
  
• Patients who require major dental treatment or surgery should be treated where there are adequate staff and facilities for their care both during treatment and in the post-operative period. It is wise to arrange for such patients to be admitted to hospital.

Inhalational Methods - Nitrous Oxide - Oxygen

The analgesic potency of nitrous oxide and its lack of toxicity give it special advantages over narcotics and other analgesics. The degree of analgesia increases with the inhaled concentration, and the rapid onset of the effects are useful when pain relief is required urgently. Recovery from its effects is rapid.

If nitrous oxide-oxygen is administered for 10 minutes, an initial plateau concentration is reached and four zones of analgesia are recognised:

• Moderate analgesia - 6-25 percent nitrous oxide: Normal and full contact may be maintained with the patient.
  
• Dissociation analgesia - 26-45 percent nitrous oxide: Marked analgesia is present, increasing with increasing concentration.
  
• Analgesic anaesthesia - 46-65 percent nitrous oxide: Spoken contact can be maintained until the level reached 65 percent, but the patient exhibits amnesia.
  
• Light anaesthesia - 66-80 percent nitrous oxide: This is not recommended, as 33 percent oxygen is necessary to maintain appropriate oxygen tension in the arterial blood during anaesthesia.

Nitrous oxide-oxygen may be administered as a pre-mixed mixture - 50 percent nitrous oxide - 50 percent oxygen - Entonox.

Intravenous Techniques

The most commonly used drugs are:

• Thiopentone.
• Methohexital.
• Diazepam.

None of the above has any analgesic properties. There is always a risk of respiratory depression and respiratory obstruction. The depression of laryngeal and pharyngeal reflexes outlasts the apparent return of consciousness.

When any sedative or hypnotic drugs are administered, the patient must be warned about the dangers of driving a motor vehicle that day, and warned against ingestion of alcohol.

They should be discharged to the care of a responsible adult.

Potent (Narcotic) Analgesics

Analgesics : Oralmedic swabs (Photo credit: Wikipedia)

• Morphine
• Pethidine
• Papaveretum (Omnopon)
• Methadone (Physeptone)
• Pentazocine (Fortral)
• Codeine Oxycodone

All these drugs are capable of producing dependence.

As well as pain relief their pharmacological effects are respiratory depression, vasomotor depression, postural hypotension, vomiting and depression of cough reflex, and patients on pentazocine frequently experience hallucinations.

Their use should be limited to: 

• Pre- and post-operative pain relief.
• Control of very acute pain.
• Relief of intractable pain of malignancy.
• Acute surgical and medical emergencies, of which there are a number.
• Pre-medication.

Mild (Non-Narcotic) Analgesics

A number of drugs are available that act peripherally, probably by inhibition of prostaglandin synthesis, and these drugs are used extensively for relief of less severe pain, particularly skeletal pain. They are effective by mouth. 

Aspirin is the most commonly used, and alternative drugs and mixtures have little advantage over aspirin, but tolerance varies from patient to patient.  Gastric irritation is a problem with aspirin, especially if the patient has a gastric ulcer or alcoholic gastritis.

Renal damage from phenacetin, and the possibility of hepatic damage from paracetamol has been recognised. Milder analgesics should not be combined with sedatives, it is necessary to use the drugs independently in the optimum dose for each.

For adults the usual dose is:  aspirin - 600 mg  paracetamol - 1 G  (repeated after 4 hours if necessary, up to 24 hours.) If these doses do not give relief, further investigation of the cause of the pain is necessary.

Sedatives, Hypnotics and Analgesics

Sedative - A drug which allays apprehension, but does not produce analgesia.

Hypnotic - A drug which induces sleep, but does not produce analgesia.

Analgesic - A drug which reduces the patient's perception of pain. The response to hypnotic drugs is dose dependent and many hypnotics given in small doses will act as sedatives.
Long-continued use of depressant drugs produces tolerance to the psychic effects of sedative drugs. Caution is always needed because metabolic disturbances or drug interaction may lead to depression of respiration which may, in turn, permit respiratory obstruction and respiratory failure as well as circulatory depression. As well as the specific sedatives and hypnotics, all tranquillisers, some antihypertensive drugs, antidepressant and antihistamines may have sedation as a side effect.watch it here www.youtube.com/watch?v=iWis-ZPuL-Q

Aspiration Prior to Injection

Aspiration should always be performed prior to injection of any local anaesthetic solution. The toxic effect of both local anaesthetic and vasoconstrictor are increased where they are injected intravenously, so aspiration should always be performed prior to injection.

Inadvertent intravenous injection may occur not only with mandibular and maxillary block injections, but also in infiltration of both facial and palatal sites. An adequate aspirating syringe with a needle no finer than 26 gauge should be used for all injections and at least 2 seconds should be allowed for the aspiration.

Dose

Local Anaesthetic - The maximum dose of local anaesthetic base should be calculated from the weight of the patient particularly in infants and children. The maximum dose will depend on whether the local anaesthetic is plain or has vasoconstrictor added, as the latter will lessen the rate of absorption of the base.

Catecholamines - Clinically effective vasoconstriction for dental anaesthesia can be obtained with concentration in the range of 1:300 000 (3.3 ug/mL) adrenaline to 1:100 000 (10.0 ug/mL), and in order to minimise toxic effects the lowest effective concentration should be used. Where adrenaline is used a concentration of 1:80 000 (12.5 ug/mL) should not be exceeded and where nor-adrenaline is used a maximum of1:50 000 (20.0 ug/mL) is suggested.