Pain and anxiety Flashcards
What is sedation?
It is a continuum which extends from normal consciousness to complete unresponsiveness. There is minimal, moderate, deep and general. Conscious sedation is a technique where a drug depresses the CNS to allow operative treatment with the minimum physiological and psychological stress. Modify patients state of mind and allow communication and the patients response to commands. Both verbal contact and protective reflexes are maintained in the patient throughout sedation. You need a good safety margin so that consciousness is maintained and airway protected.
How are gases transported in and out of the body by the respiratory system?
Ventilation is the moving of gas into and out of the lungs. Diffusion is the transfer of gases from the lungs into the blood. Oxygen is transported by haemoglobin in the blood. It is involved in energy metabolism to produce energy for the body. Oxidation is the use of oxygen to produce energy within the cell and the production of carbon dioxide. The waste product is carbon dioxide which is collected by diffusion into the veins. It goes back to the lungs inot the alveoli and out of the body.
What are the structures in the upper airway?
The nasal cavity contains the superior, middle and inferior turbinates. There is the hard and soft palates. The nasopharynx contains the tonsils/adenoids and uvula. The oropharynx contains the tongue. The laryngopharynx/hypopharynx contains the vallecula and epiglottis. The larynx contains the oesophagus and trachea. There is also the glottic opening, vocal cords, thyroid cartilage, cricothyroid cartilage, cricoid cartilage and thyroid gland.
What are the structures in the lower airway?
There is the primary, secondary and tertiary bronchus. There is the bronchiole, terminal bronchiole and alveoli.
What is inspiration and expiration?
Inspiration is an active process initiated by the diaphragm. It is supported by intercostals. Accessory muscles are used for more vigorous inhalation. The normal rate is 10-18 per minute. Expiration is a passive process and it is the elastic recoil of lungs. Forced expiration involves abdominal and intercostals.
Air is inhaled when the diaphragm contracts. The intercostals pull the ribs away and expand the lungs. When relaxed they recoil back and air is exhaled.
How does gas exchange occur?
Gas exchange occurs within the alveoli. The wall is a single layer thick and it is 0.2 micrometers. It is adjacent to the pulmonary capillary wall. Gases diffuse down concentration gradients.
How is oxygen transported around the body and used in the tissues?
The oxygen binds to haemoglobin. Each molecule can carry 4 oxygen (O2) molecules. It is carried within red blood cells. CaO2= 1.34 x Hb x SpO2. We rely on adequate circulation to transport to tissues. Delivery = CaO2 x Cardiac Output. Properties of haemoglobin mean it releases O2 when it gets to the tissues. The mitochondria uses the oxygen for metabolism. Glucose is the main energy source and combined with oxygen it produces CO2.
How does anaemia affect sedation?
People with anaemia have less haemoglobin so care is needed with sedation as reduced oxygen will affect them more.
What is CaO2?
CaO2 is arterial oxygen content and refers to the volume of oxygen delivered to the tissues per unit blood volume.
How is the respiratory system controlled?
It is by the autonomic nervous system - brainstem, medulla and pons. There is the respiratory centre which responds to blood CO2 levels.
What is the basic function of the cardiovascular system?
The basic function is to deliver oxygenated blood to the body organs and tissues for metabolism. There is tissue perfusion.
How does blood pass through the cardiovascular system?
There is a parallel pumping system. The right side is oxygenated blood. It carries oxygen from the lungs. From the left ventricle it pumps up through the aorta and goes to the head and the rest of the body. Then the blood comes back through the superior and inferior vena cava to the right atrium and ventricle. It is then pumped back through the pulmonary vessels back to the lungs.
What happens with inadequate perfusion?
With inadequate perfusion, organs and tissues quickly begin to fail. Cardiac ischaemia leads to angina and myocardial infarction. Cerebral ischaemia leads to faint/collapse and stroke. Lung – hypoxia.
What is the main determinant of organ perfusion?
Blood pressure.
How is BP displayed and how is this calculated?
BP is displayed as systolic, diastolic and mean MAP. 120/60 (80). The mean is calculated as diastolic + 1/3 (systolic-diastolic). Thankfully modern machines will calculate it for you. Normal MAP is 80mmHg.
How is blood pressure regulated?
Blood pressure has autoregulation. There is the sympathetic and parasympathetic system. Sympathetic will increase the blood flow and parasympathetic will decrease the blood flow and heart rate. When the tissue perfusion reduces autoregulation will try to increase the perfusion. When the person gets older and arteries get clogged (arteriosclerosis) so blood pressure will be higher to ensure perfusion. Autoregulation ensures adequate perfusion over a range of MAPs. Limits will shift in people with chronic hypertension.
What is blood pressure determined by?
Blood pressure is determined by 2 main components which are cardiac output CO and systemic vascular resistance SVR. Cardiac output is the amount of blood ejected by the heart per minute. The average is 5 litres per minute. It is determined by the heart rate HR and the stroke volume SV. HR between 50-180 have little effect. SV is reduced by dehydration/blood loss, ischaemic heart disease/heart failure and anaesthetic drugs.
Systemic vascular resistance is the resistance produced by the vascular system to the flow of blood. It is mainly small arterioles in the body. Constriction increases SVR and hence BP. Dilation decreases SVR and hence BP. SVR decreased by sedative drugs, anaphylaxis and sepsis/infection.
What is the acute and chronic control of blood pressure?
Acute:
- Baroreceptors in aortic arch and internal carotids
- Send signals to brain stem
- Autonomic nervous system alters rate and strength of heart contraction and constriction of blood vessels.
Chronic:
- Renin-angiotensin system
- Aldosterone
- Chronic regulation of blood sodium concentration and body fluid retention
What are the commonly used drugs in sedation?
- Benzodiazepines e.g. midazolam which acts on GABA receptors
- Opiates - fentanyl, remifentanil (opioids) act on Mu receptors
- Others - propofol (potent and short acting so continuous infusion), ketamine, dexomethomedine (alpha2 agonist)
What are the advantages and adverse effects of midazolam?
Advantages: - Quick onset - Short action of duration - Minimal cardiovascular effects Adverse: - Respiratory depression - Airway obstruction
What is fentanyl?
Fentanyl is a man made synthetic opiate drug. It provides analgesia and sedation. The onset is 1-2 minutes and the peak is 10-15 minutes and the duration is 30-60 minutes. The dosing is 25mcg (0.5ml) bolus up to 200mcg max.
What are the advantages and adverse effects of fentanyl?
Advantages: - Provides analgesia as well as sedation - Fast onset - Short duration of action Adverse: - Hypotension and bradycardia - Respiratory depression - Nausea and vomiting
What is remifentanil?
Remifentanil is an ultra short acting opiate. It has a very potent analgesic effect. It has to be administered by continuous infusion via syringe driver. Will stop working within a minute of ending infusion.
What are the advantages and adverse effects of remifentanil?
Advantages: - Excellent analgesic properties - Extremely short duration of action 8 minutes Adverse: - Hypotension - Bradycardia - Respiratory depression and apnoea
What is propofol?
Propofol is an intravenous anaesthetic induction agent. The onset is 30 seconds and the duration is 10-15 minutes. The dosage is 10-20mg (1-2mls) every 5 minutes or by continuous infusion.
What are the advantages and adverse effects of propofol?
Advantages:
- Very potent sedative
- Rapid onset
Adverse:
- Only for use by trained sedationist or anaesthetic staff
- Can rapidly progress to general anaesthesia
- Significant cardiovascular and respiratory depression
What is polypharmacy and the benefits and risks?
Polypharmacy is the use of more than one drug. It can have advantages as different drugs give different effects e.g. opiate and benzodiazepine gives both sedation and analgesia. Giving a second drug means you can use less of the first drug and so potentially reducing side effects. But there is greater risk of overdosing and over-sedating patients. Drugs with the same side effects will have synergistic action and make those side effects even more likely.
Why is knowledge of time to peak effect even more important with polypharmacy?
Must be aware of time to peak effect of the drugs you are using. Midazolam 5-7 minutes, fentanyl 10-15 minutes and propofol 1minute. Not waiting for full effect of first drug may lead to dosing of second drug peaking with first drug. Leads to significant over-sedation and side effects.
What is the history of drugs used for GA?
- 1846 ether
- 1847 chloroform
- Problems of sudden death/liver damage
- 1877 cocaine
- LA infiltration, nerve blocks, spinal and epidural
- 1920-30 intubation
- Barbiturates as induction agents
- 1943 muscle relaxants
- 1950 halothane – reduced toxicity
What can cause difficulty with dental treatment?
- Co-operation
- Anxiety/phobia
- Medical conditions/mental health issues
- Involuntary movements
- More complex treatments/quadrant dentistry
- MDAs phobia 19 or above
What are some basic behavioural management strategies?
- Tell, show, do
- Positive distraction e.g. music, ipod, TV
- Relaxation
- Systematic desensitisation - gradual acclimatisation
- Hypnosis
What are some alternative behaviour management strategies?
- Acupuncture
- Drugs - oral/HIS/IV sedation
What is premedication?
Diazepam is in the DPF/ask GMP. Diazepam can be irritant to the skin and has a hangover effect so takes longer to wear off. 2mg oral dose of diazepam can be prescribed to be taken a few hours before or the night before. Safer to ask GMP to prescribe it.
What are the properties of an ideal sedation agent?
- Simple to administer
- Rapid onset
- Predictable action/duration
- Rapid recovery
- Rapid metabolism/excretion
- Low incidence of side effects
How can oral sedation be used in dentistry?
The patient can have oral premedication at home:
- Reduces anxiety in advance of treatment and facilitates attendance
- Diazepam 2-5mg in the morning of treatment/attendance
- Temezepam 10mg the night before
- Ask GMP for advice/to prescribe
The patient can have oral sedation in the surgery with monitoring. It will be 10-20mg Temazepam.
Oral sedation is simple to administer, predictable action/duration and low incidence of side effects. There is no rapid onset, rapid recovery or rapid metabolism/excretion. You need specialist monitoring/training.
What are the features of inhalation sedation?
- Specialist equipment/training and surgery requirements (scavenging)
- Need patent nasal airway
- Good for children
- Minimal intervention
- Analgesic
- Hazards of chronic exposure
- Simple to administer
- Rapid onset
- Predictable action/duration
- Rapid recovery and metabolism
- Low incidence of side effects
What are the features of IV sedation?
- Requires pulse oximeter monitoring
- Midazolam titrated according to response
- Anxiolytic
- Anterograde amnesia
- Muscle relaxant
- Anticonvulsant
- Minimum effect on cardiovascular/respiratory depression
- No analgesic effects
- Reversal agent - flumazenil
- Requires escort to go home for safety
- Requires cannulation and associated risks
What disorders can IV sedation be useful for?
- Epilepsy
- Movement disorders
- Stress related medical conditions
What are the side effects of IV sedation?
- Over sedation
- Cardiovascular depression
- Respiratory depression
- Specific drug interactions
- Tolerance – some patients may take diazepam outside of dentistry so may have tolerance
- Sexual fantasy – make sure there are others in the same room who can be a witness
What are the advantages of IV sedation?
- Simple to administer
- Rapid onset
- Predictable action/duration
- Rapid recovery
- Rapid metabolism/excretion
- Low incidence of side effects
- Specialised training/monitoring
How many trained people should be in the room during sedation?
There needs to be a second appropriate person at all times. A second person trained in sedation is required for sedation to be undertaken, this may be a DN/dentist/anaesthetist. This is for monitoring and as a chaperone.
What are the costs due to sedation?
- Materials
- Staff
- Work time lost to patient/escort
What are the medicolegal aspects of sedation?
- Written consent
- Escort requirements
- Appropriate post-operative care
Where can sedation be undertaken?
- Registered and inspected premises
- With appropriately trained staff
- Appropriate equipment and drugs
Why is there a demand for sedation?
- Visiting the dentist is the second most common fear after public speaking (USA 1987)
- Child dental health survey 2013 - 50% moderately anxious, 10% extremely anxious
- The control of anxiety and pain is fundamental to the practice of dentistry - GDC 2002
- Deaths at dentist from GA in practice
What are the sedation techniques?
- Inhalation - nitrous oxide/oxygen, sevoflurane
- Intravenous - midazolam, propofol
- Transmucosal - midazolam (intranasal, buccal)
- Oral - temazepam, diazepam, midazolam, ketamine
- Intramuscular - ketamine
- Combination of above
Who discovered nitrous oxide?
Horace Wells in 1844. Today people use it recreationally as it is a legal high but there are deaths due to hypoxia.
What are the properties of nitrous oxide?
- Volatile
- Denser than air – 1.0:1.5
- Least potent – MAC50 is 104 (minimum amount of gas you need to give somebody for 50% of population to not feel scalpel incision) sevoflurane has a MAC50 of 2
- Often used in anaesthesia as carrier/induction gas
- Poorly soluble – rapid onset/rapid recovery – don’t need a recovery room like you do with IV sedation
What are the pharmacokinetics of nitrous oxide/oxygen sedation?
It is inhaled into the lungs with oxygen through a nasal mask. It travels down partial pressure gradient from alveolus to capillaries. It is hardly metabolised - 0.004%. It is excreted through the lungs. The elimination half life is approximately 5 minutes.
What are the pharmacodynamics of nitrous oxide/oxygen?
- Analgesic
- Anaesthetic
- Hypnotic
- Anxiolytic - GABA - more relaxed feeling for patient
What are the stages of anaesthesia?
1 Analgesia
- A Plane 1 is moderate sedation and analgesia (5-25 N2O)
- Plane 2 - dissociation sedation and analgesia (20-55% N2O) patient can imagine they are somewhere else
- Plane 3 - total analgesia (50-70% N2O) losing consciousness
2 Excitement
3 Surgical analgesia
4 Respiratory paralysis
With conscious sedation we want to be in stage 1. With surgery we would want stage 3, never stage 4. Give 30% nitrous oxide.
What are the signs of adequate sedation?
- Awake
- Feels relaxed
- Suggestive state
- Giggling – give more or less as this is not helpful
- Verbal responses
- Maintaining mouth open
- Reduced blink rate
- Spontaneous respiration
What are the signs of over sedation?
- Patient no longer enjoying the effects
- Hysterical laughter, tears
- Decreased cooperation
- Nausea/vomiting
- Mouth closing – repeatedly
- Snoring
- Incoherent speech
- Irrational and sluggish responses
- Loss of consciousness
What are the indications for inhalation sedation?
Social: - Mild anxiety/needle phobias/gagging/fainting - To enable cannulation Medical: - Conditions aggravated by stress - Conditions where continuous oxygen delivery is beneficial - Conditions which affect cooperation Dental: - Unpleasant procedures - Avoid GA in medically compromised
What are the contraindications for inhalation sedation?
Social:
- Severe anxiety/claustrophobia/no escort
- Lack of understanding
Medical:
- Blocked nose/URTI/unable to nose breathe
- Recent eye/middle ear/sinus/intracranial surgery
- Bleomycin therapy/myasthenia Gravis
- Pregnancy - 1st and 3rd trimesters
Dental:
- Traumatic procedures/unsuitable for LA alone
- Treatment on upper anterior teeth - lip trapped
What are the safety features/checks for inhalation sedation?
- Pin index system - tube going from nitrous oxide and oxygen cannot get mixed up
- Scavenging at 40L/minute - removing air at level of nose mask
- Nasal mask and tubing - inner tube to nitrous oxide and oxygen and outer tuber to scavenging
- Oxygen failsafe - if oxygen cuts out the nitrous oxide will also automatically cut out
- Max 70% nitrous oxide and can’t give any more than this
- Oxygen flush - delivers 30L of oxygen in a second, not pleasant and only used in an emergency, 35 litres/minute
- Air entrainment valve - if bag goes flat this allows patient to breathe in normal fresh air, check valve is clear
- Reservoir bag needs to be changed on date written on bag as it is made of rubber
- 2 oxygen and 2 nitrous oxide cylinders on each machine
- Colour coded cylinders, tubing and flowmeters
- Diameter index safety system
- NIST pipeline (anti-static, non-compressible, colour coded)
- Touch coded knobs for individual flowmeters
- Pressure regulators 45-55psig
- 30% minimum oxygen
- One way valve in bag/tee
- Conducting tube minimises resistance to gas flow, prevents kinking
- One way valve on expiratory limb
- Scavenging active/passive
What are the pre-operative instructions for nitrous oxide?
- Light meal, avoid fizzy drinks
- Take routine medicines as usual
- Children must be accompanied to and form their appointment by a competent adult
- Do not bring other children
- Can cause dizziness/nausea/headaches at higher doses
What is the technique for inhalation sedation?
- Safety checks
- Introduce child (giggle gas, happy gas)
- Start O2 and turn up flow rate (5-6L/min)
- Fit mask and encourage nose breathing
- Titrate N2O 10% per minute to 30% and then 5% per min until sedated
- Hypnotic, suggestion, clinical monitoring
- 100% O2 minimum of 3 minutes to recover - preventing diffusion hypoxia (5 minutes in Sheffield)
What is diffusion hypoxia?
It was described by Fick 1955 and it is seen in the 10 minutes following the cessation of inhalation sedation. Nitrous oxide is poorly soluble in blood. When you stop giving it the partial pressure reduces in the lungs so the nitrous oxide travels from capillaries to the alveoli rapidly which floods the lungs with nitrous oxide. The rapid elimination of nitrous oxide into the lungs dilutes the oxygen within the alveoli and lowers the alveolar oxygen concentration. This is why oxygen needs to be given. It is responsible for most reports of headache, nausea and lethargy post-operatively. It is prevented by routine administration of 100% oxygen for 3-5 minutes post-operatively.
What needs to be recorded in the notes in inhalation sedation?
- Consent and escort
- Safety checks completed
- Second appropriate person (dental nurse)
- Mask size
- Flow rate
- Max dose
- Response/level of cooperation
- Recovery time
How do you reduce exposure during inhalation sedation?
- COSHH exposure limits for dentists - 100ppm TWA (time weighted average) over 8 hours
- Active scavenging at 45L/min - statuary requirement in UK, at level of nasal hood
- Passive scavenging - floor level extractor fan, opening window
- Supplementary high volume aspiration
- Rubber dam - inconclusive but seems logical
- Well-fitting mask
- Good technique - reduce mouth breathing/conversation/titrate carefully
- Good initial patient assessment
What are the types of occupational hazard with inhalation sedation?
- Reproductive
- Haematological
- Neurological
- Also reports of hepatic disease, renal disease, cytotoxicity, malignancy
