T2: Premeds Flashcards
What is a premed and why is it given (briefly)?
- Premedication refers to a drug treatment given to a patient before a (surgical or invasive) medical procedure.
- usually a combination of drugs that have different actions that are synergistic (they work together), not just additive.
- These drugs are usually given to provide sedation and analgesia.
Why is a premed given (extended reasons)?
- to relax patient prior to surgery, reducing restraint needed and causing less stress (reduced anxiety)
- to provide analgesia prior to the painful experience (pre-emptive analgesia)
- to reduce the induction agent dose and to give a smoother induction
- to help reduce the amount of anaesthesia maintenance agent used
- to help decrease the amount of saliva and respiratory secretions produced
- to prevent vomiting and possible aspiration of fluids
- to prevent bradycardia by increasing the heart rate
- to help reduce some of the side-effects of some anaesthesia drugs
- to assist with a smoother recovery period after a general anaesthesia
When choosing a premed, what influences your choice?
- age of the patient
- species
- breed
- procedure
- condition of the patient
- combination with the anaesthetic agent to be used
- personal preference of the vet and also the hospital
- what’s available in the hospital or clinic
Categorising the patient for anaesthesia
(how patients are categorised may be clinic dependant)
Describe a patient who is categorised as excellent
animal with no organic disease or in whom the disease is localised and is causing no systemic disturbance. e.g. healthy 3 year old neuter.
Categorising the patient for anaesthesia
(how patients are categorised may be clinic dependant)
Describe a patient who is categorised as good
animal with mild systemic disturbance which may or may not be associated with the planned procedure e.g. mildly anemic patient, obese patient, geriatric patient.
Categorising the patient for anaesthesia
(how patients are categorised may be clinic dependant)
Describe a patient who is categorised as fair
animal with moderate systemic disturbance which may or may not be associated with the planned procedure and which usually interferes with normal activity but is not incapacitating e.g. - mitral valve insufficiency, moderate anemia.
Categorising the patient for anaesthesia
(how patients are categorised may be clinic dependant)
Describe a patient who is categorised as poor
animal with extreme systemic disturbances which are incapacitating and are a constant threat to life and seriously interferes with the animal’s normal function e.g. uncompensated mitral valve insufficiency, severe pneumothorax.
Categorising the patient for anaesthesia
(how patients are categorised may be clinic dependant)
Describe a patient who is categorised as critical
animal presenting in a moribund condition, and is not expected to survive 24 hours with or without surgery. This implies that medical treatment cannot improve the animal’s condition and that surgery is required immediately e.g. – acute, severe intra-abdominal hemorrhage.
What are the four parts of the anaesthesia process?
- Pre-Anaesthesia (premed)
- Induction
- Maintenance
- Recovery
Common premeds
List the common types of premeds used and give examples
- Anticholinergics: atropine
- Sedatives & tranquillisers: ACP (acepromazine), diazepam, midazolam, xylazine, medetomidine
- Dissociatives: ketamine
-
Opioids: morphine, methadone, butorphanol, buprenorphine
*
Why are Anticholinergic drugs given?
to help maintain a normal heart rhythm by blocking the vasovagal reflex
Anticholinergic drugs
When does the vasovagal reflex occur?
- occurs when the vagal nerve (which innervates the abdomen, throat and eye) is stimulated.
- This reflex results in the slowing of the heart rate
- Vagal tone increase can be from drugs, vagal reflexes during surgery such as snapping the ovarian ligament, ocular surgery and hypothermia.
- It also increases the heart rate, which in turn improves blood pressure; this can in turn lead to tachycardia.
Anticholinergic drugs
Atropine is a anticholinergic drug, how does it work?
- Atropine is used to help prevent vagally-mediated arrhythmias such as bradycardia and bradyarrthymias by decreasing vagal tone.
- It also prevents excessive salivation and bronchial secretions.
- Atropine also causes mydriasis (dilated pupils) so its use is contraindicated in animals with glaucoma, with a pyloric obstruction, pre-exisiting tachycardia or ventricular arrhythmias.
Name a drug that is classed as a PHENOTHIAZINE
How does it work?
Used in?
Where is it metabolised?
Time of onset?
Duration?
- Acepromazine (ACP2, ACP 10)
- CNS depressant that gives sedation of long duration. It is a dose-dependant sedation.
- It gives no analgesia.
- Used in dogs, cats, horses, cattle, sheep, pigs
- It is a potent vasodilator so is contraindicated in low blood pressure and poor cardiac output patients, and patients with epilepsy.
- It is metabolised in the liver.
- 30mins time of onset
- 2 - 4 hours duration
Name a drug that is a Benzodiazepine
How does it work?
Used in?
what are its effects?
- anaesthesia effects
- others?
Route of admin?
time of onset?
duration of action?
- Diazepam (Pamlin eg Valium)
- binds to benzodiazepine receptors in CNS
- Used in cats, dogs, horses
- has sedative, muscle relaxing and anticonvulsive effects. There are no significant cardiovascular effects.
- reversal agent in flumazenil
- Diazepam can cause behaviour changes in cats such as aggression or anxiety and can also cause excitement in young healthy animals.
- contraindicated in pregnant animals.
- Given: IM or IV
- Onset of action: 1-2 minutes following IV
- Duration of action: ±20-30 minutes.
