Sedation monitoring and post sedation recovery and discharge
Safe Feline Sedation and Anesthesia · •Cardiovascular effects include vasoconstriction,...
Transcript of Safe Feline Sedation and Anesthesia · •Cardiovascular effects include vasoconstriction,...
Safe Feline Sedation and Anesthesia
Katy W. Waddell, LVT, VTS
(ECC) (Anesthesia/Analgesia)
Normal Behavior
• Many clients do not understand that cats are genetically programmed to hide signs of illness and injury
• Cats are unique as the only companion animals that are solitary hunters, as well as being both predators and prey.
Common stressors for cats in veterinary hospitals
• Other animals and humans
• Noise (eg, medical equipment, telephones, barking, human conversation)
• Smells and odors (eg, other animals, disinfectants)
ASA Status Class I
• Minimal Risk
• Normal healthy animal, no underlying disease
Class II
• Slight risk, minor disease present
• Animal with slight to mild systemic disturbance, animal able to compensate
• Neonate or geriatric animals, obese
Class III
• Moderate risk, obvious disease present
• Animal with moderate systemic disease or disturbances, mild clinical signs
• Anemia, moderate dehydration, fever, low-grade heart murmur or cardiac disease
Class IV
• High risk, significantly compromised by disease
• Animals with preexisting systemic disease or disturbances or a severe nature
• Severe dehydration, shock, uremia, or toxemia, high fever, uncompensated heart disease, uncompensated diabetes, pulmonary disease, emaciation
Class V
• Extreme risk, moribund
• Surgery often performed in desperation on animal with life threatening systemic disease
• Advance cases of heart, kidney, liver or endocrine disease, profound shock, sever trauma, pulmonary embolus, terminal malignancy
ASA Status
• One feline study that evaluated age and ASA physical status as risk factors for perianesthetic morbidity and mortality found that ASA status rather than age was a better predictor of perianesthetic complications.
• Cats with an ASA status of 3 or higher had a significantly increased risk of complications.
• Another study found that age (>12 years) was a risk factor independent of ASA status.
Neonates
• The neonate's physiologic differences from the adult
• The cardiac output is rate dependant in the neonate. The resting output is very near the maximum potential output. Cardiac reserve is minimal.
• High metabolic rate leads to high oxygen consumption.
• Neonates poorly regulate their body temperature.
• The blood-brain barrier is more highly permeable.
• Neonates have low protein binding of drugs due to reduced albumin.
• High body water content, low body fat. Extracellular fluid volume higher than adult.
• Decreased renal function, reduced renal clearance
• Immature hepatic enzyme function leads to reduced hepatic clearance.
0-6 months
• minimal glycogen stores in the liver of the pediatric patient,
• withholding of food should be kept to a minimum.
• Unweaned puppies and kittens should not be fasted,
• patients older than 6 weeks of age fast only for a maximum of 3 to 4 hours before general anesthesia.
• Prolonged fasting of these patients may result in hypoglycemia and dehydration and predispose them to hypothermia.
• Withholding of water is unnecessary.
Junior 6 months to 2 years
• Teenagers to young adult equivalent
• Minimum data base vs Big 4
Prime 3-6 years
• 28 – 40 human equivalent
• Prime for data base?
• Always ascertain BCS and MCS
Mature 7 – 10 years
• 44 – 56 human equivalent
• Data base include thyroid panel?
• Always ascertain BCS and MCS
Senior 11 – 14 years
• 60 – 72 human equivalent
• Thyroid ?
• Activity level
• Always ascertain BCS and MCS
Geriatric 15 + years
• 76 + human equivalent years
Develop a plan
• Working with the owner
• Less hectic schedule
• Meds to be given at home
Patient physical examination
• signalment, physiologic parameters and all body systems
• BCS, MCS
• identify any potential trends
Fearful patients
• Can you identify fearful cats prior to visit?
• Yes – consider gabapentin to be given at home
• No – always use feline friendly handling methods
• Especially with unknown health status
• On admission
• Move to quiet exam room
• IF amenable – physical exam with FF handling
• IF unsafe to patient/staff – consider chemical restraint
• Have all supplies ready at hand!
• Be flexible, each patient is an individual
• Remain calm
• Synthetic pheromones
• The increased release of catecholamines in fearful or stressed cats leads to • tachycardia,
• systemic hypertension
• and/or tachypnea, • all of which can increase the risks associated with
anesthesia
Physiological Effects of Stress
• Hyperglycemia
• Hypokalemia
• Increased CPK
• Lymphopenia
• Neutrophilia
• Hypertension
• Cardiac murmurs
• Improper response to drugs
Gabapentin
• Gabapentin (50 – 100 mg per cat or 150 mg if big cat, PO, 2 – 3 hours before arrival)
• May be given twice, evening before appointment and morning of appointment
• Geriatric or senior cats may try lower dose (50mg)
• Does have some analgesic effects
Alfaxalone IM
• 1-2 mg/kg
• Better results with addition of midazolam or butorphanol
• Usually manageable within 7-10 minutes
• Short duration
Kitty magic
• Gazillion recipes !!!!!
• TBD
• Premed or mild to moderate sedation:
• Telazol@ 1mg/kg
• [email protected] mg/kg
• Dexmedetomidine @ 2.5 mcg/kg
• TBD
• Profound ! Sedation
• Telazol @ 2 mg/kg
• Butorphanol @ 0.1 mg/kg
• Dexmedetomedine @ 5 mcg/kg
My usual combination if necessary
• Dexmedetomedine @ 2mcg/kg
• Butorphanol @ 0.3 mg/kg
• Ketamine @ 4 mg/kg
For geriatric or ill cats
• Butorphanol (0.2 – 0.4 mg/kg, IM) or Methadone (0.3 – 0.5 mg/kg, IM) +
• Alfaxan (1 – 2 mg/kg, IM)
• Butorphanol (0.2 – 0.4 mg/kg, IM) +/- Midazolam (0.2 mg/kg, IM)
Box or mask inductions
• hazardous approach to “sedating” the fearful feline.
• should be avoided
• 1) scary and stressful for patients,
• 2) dangerous to personnel (exposure to inhalants associated with numerous adverse health effects including impaired reproductive function), and
• 3) dangerous to the patient
Kitty would prefer some chemicals
I’m a good boy
Purpose of premedication
• Prevention of: – Increase of sympathetic tone caused by:
• Fright
• Excitation
• Difficult restraint
Which lead to: • Increased metabolism
• Increased cardiac work/oxygen demand
• Predisposition to arrhythmias
• All of which may lead to hypoxia
Premedication options
• Drug dosages used for premedication should be tailored to the individual cat.
• opioids are useful for premedication and as part of procedural sedation
• Morphine and buprenorphine undergo hepatic metabolism with glucuronidation, so the duration of action of these tends to be longer because of the lack of functional glucuronyl transferase in cats.
• At the low doses of opioids generally used for premedication, the heart rate may decrease slightly.
• Anticholinergics can be used to reverse this effect if deemed necessary.
• Atropine (0.02 mg/kg) and glycopyrrolate (0.01 mg/kg) SC may increase heart rate by about 10% in combination with an opioid
Benzodiazepines
Midazolam and diazepam: Cause little or no myocardial depressant effects
May see increase in heart rate due to excitation with inadequate use of adjunctive agent i.e. mu opioid
• Buprenorphine – mixed agonist/antagonist
• Duration of action 4-6 hours, good for mild to moderate pain
• 0.01 - 0.02 mg /kg IM or IV
• Butorphanol – mixed agonist/antagonist
• 0.1 -0.4 mg/kg IM or IV
• Duration 60 – 90 minutes
• Better sedation in cats than dogs
• Mild – moderate pain
Alpha 2 agonists
• Used in veterinary medicine to produce:
• sedation,
• analgesia
• Anxiolysis
• Reduce requirements of anesthetics
Fentanyl • Pure mu agonsist
• Causes dose dependant bradycardia (increase in vagal tone)
• Bradycardia is responsive to anticholinergics – atropine/glycopyrrolate
• Single dose IV is very short acting – up to 20 minute duration
Hydromorphone:
• morphine-like agonist, primary activity at the mu receptors.
• bradycardia due to central vagal stimulation,
• alpha-adrenergic depression causing peripheral vasodilaiton, decreased peripheral resistance
• baroreceptor inhibition.
• 0.02 -0.1 mg/kg
• Moderate duration 2-4 hours
Oxymorphone
• Similar effects to hydromorphone
• Case management of side effects the same
• 0.02 – 0.1 mg/kg
• 2 – 4 hour duration
Methadone
• Increase in vagal tone – dose dependent
• 0.2 – 0.5 mg/kg
• 2 – 4 hour duration
Alpha 2 adrenergic agonists
• Cardiovascular effects include vasoconstriction, decreased heart rate (by 40%) and cardiac output (by 60%) and increased systemic vascular resistance (300%) with minimal change in blood pressure.
• If α -adrenergic agonists are used for premedication, the decreased cardiac output may slow the onset of subsequent intravenous induction drugs.
Dexmedetomidine
• Alpha 2 agonist
– 0.00025 – 0.04 mg/kg
higher doses may induce vomiting which may be prevented by combining with butorphanol or giving maropitant pre-operatively
– Reversal: Atipamezole
Induction agents
• Propofol – hypnotic
• Dose dependent on effect of premedication
• 2 – 6 mg/kg titrated to effect
Alfaxalone
• Neuroactive steroid
• Calculated/titrated dose over 60 seconds
• Myocardial depression with higher end of dose range
DISSOCIATIVE AGENTS
• Will indirectly stimulate the cardiovascular system by increasing sympathetic tone
• cause an increase in heart rate, cardiac output, mean arterial pressure, pulmonary arterial pressure and central venous pressure.
• Increase in rate causes an increase in myocardial work and oxygen demand/consumption
Ketamine
• Does not produce a true anesthetic state – disassociation from the environment with analgesia and sensory loss
• Heart rate and arterial pressure increase due to an increase in sympathetic tone (CNS derived)
• Peripheral vascular resistance is unchanged
• Prior administration of benzodiazepine, acepromazine and/or inhalant agents may decrease or prevent cardiovascular effects
Telazol
• Tiletamine
• Zolazepam - benzodiazepine
• Clinical effects similar to ketamine
• Draw 2mg/kg and titrate to effect
• Prolonged or rough recovery when used as a sole agent
Inhalant anesthetics
• High cardiac output can delay anesthetic induction – blood flow through the lungs maintains the diffusion gradient between the alveoli and blood.
• i.e. – slower induction in excited patients vs. more rapid induction in decreased output patients – shock, hypovolemia, etc.
MAC
• MAC = minimal alveolar concentration. Produces immobility in 50% of patients receiving noxious stimuli
• Varies with agents and species
• The lower the MAC, the higher potency of the anesthetic agent.
Isoflurane
• MAC for cats is 1.63%
• Heart rate is seen to increase slightly
• Decrease in arterial blood pressure – main cause is decreased vascular resistance vs decreased cardiac output
Sevoflurane
• Causes mild myocardial depression (decreased contractility)
• Mild systemic vascular resistance and arterial blood pressure depression
• Less likely to see an increase in heart rate, vasodilation when compared to isoflurane
• MAC for cats = 2.58%
Nursing Care Goals
• Make the cat feel safe and secure in the clinical setting and at home following discharge
• Minimize stress to the patient during in-clinic and at-home treatment
• Contribute to successful recovery from illness, surgery or other treatment, and injury