Ch 21 + 22 Anaesthesia monitoring and conditions Flashcards
Describe the 5 ASA grades
What is the rate of anaesthetic-related death in animals?
1 : 500 - 1000
Humans 1:10,000
What medications are contraindicated in animals with cardiac disease?
alpha-2 agonists
Acepromazine should only be used if they can tolderate vasodilation
Caution wth ketamine in HCM (increases sympathetic activity)
Propofol/alfax should be used cautiously due to vasodilation. Etomidate is ideal.
Some animals wont be able to tolerate gas vasodilation
What medications are contradicted in the face of thyroid disease?
Ketamine due to potential cardiomyopathy and possibility of thyroid storm
Avoid NSAIDs and maintain normal/slightly elevated BP due to potential for underlying renal disease
May have cardiomyopathy
What is the hypoxic pulmonary vasoconstriction?
A compensatory mechanism that results in vasoconstriction of the blood flow to the alveoli that do not have an adequate oxygen supply. Helps to balance a V/Q mismatch in awake patients
Inhalant anaesthetic agents impair or eliminate this compensatory mechanism causing V/Q mismatch to worsen in the anaesthetised patient
What are some potential benefits of ketamine when used on patients with airway disease?
Causing bronchodilation (good for allergic airway disease)
Maintains the respiratory center sinsitivty to PaCO2
Maintains respiration making is a useful indiction agent
What considerations should be made when making a plan for a patient with liver disease?
lower doses of drugs if hypoalbuminaemic as many anaesthetic drugs are highly protein bound to albumin
Propofol has extrahepatic metabolism and so is a good choice, as is remifentanyl (plasma esterase)
Inhalants undergo very little hepatic metabolism and are also a good choice
List some drugs which are renally excreted and therefore effects may be prolonged in patients with renal disease
Ketamine
benzodiazepines
opioids
acepromazine
What anaesthetics should be avoided in renal disease?
Ketamine
Sevofluorane (Compound A)
Epidural contraindicated due to potential coagulopathies in severe uraemia
What are the main risks after relieveing a urinary obstruction?
Post-obstructive diuresis
Dialysis disequilibrium - seen if BUN drops rapidly causing a decrease in serum osmolality and associated fluid shifts resulting in cerebral oedema
What is the maximal allowable pressure during laparoscopy?
At what pressure is there an association with anuria and acute renal failure?
-14cmH20 maximum allowable
- 25cmH2O anuria, AKI
What patient positioning is used for laparoscopic surgeries?
Trendelenburg positioning (head-down)
What is the only anaesthetic drug which has been shown to adversely effect neonate survival in C-sections?
xylazine
For lumbosacral epidurals, what volume is appropriate for the HLs? For abdominal/thoracic?
0.2ml/kg for HLs
0.3ml/kg for abdomen/thorax
What considerations need to be made when anaesthetising for an ophtho procedure?
Maintaining central eye position (low dose neuromuscular blockade)
Avoiding spikes in IOP such as can be caused by propofol and ketamine
What are the effects of hypothermia?
Prolonged recovery
Decreased immune defense
Prolonged healing
Altered drug metabolism
Cognitive depression
Arrhythmias
Really Inadequate Heat Does Cool Animals
List five possible caused of hypoxaemia
Hypoventilation
Right-to-left shunting
Decreased inspired oxygen
Diffusion barrier impairment
V/Q mismatch
What are the effects of hypercarbia?
Initial hypertension, tachycardia and tachypnoea
Eventual sympathetic collapse causing bradycardia, ventricular arrhythmias and hypotension when over 85mmHg
List some potential cause of hypercarbia?
Expired or exhausted absorbent
Malfunctioning expiratory valve
Inadequate flow rate in non-rebreathing system
Increased metabolism that can occur with hyperthermia or seizure
What is the ideal tidal volume?
8-12ml/kg (should not exceed 15)
anaesthetic principles
Administration of drug is balanced by
* Redistribution to other areas of body
* Metabolism and excretion of drug
Lipid soluble drugs take longer to reach steady state as they rapidly redistribute (large volume of distribution)
Anaesthetic distribution in body is divided into 3 groups
* Vessel-rich group – (heart/brain/kidney) up to 75% CO + increased O2 consumption
* Muscle group
* Vessel-poor group – (fat) tissue with low metabolic rates
induction occcurs folowing rapid distribution to vessel rich group, awakening dt redistribution > both depnednet on CO
maintenance therefore dependent on constant delivery either as CRI or inhalent
minimum aveolar conc to produce anaethesia depends on: type, other drugs, pateint factors (CO, temp, ventilation + redistribution)
MAC
MAC is the minimum concentration of an inhaled anesthetic agent required to prevent movement in 50% of subjects exposed to a supramaximal stimulus.
dose of inhalant to be administered is related to the minimum alveolar concentration value for the species and the physical properties of the inhalant used
minimum aveolar conc to produce anaethesia depends on: type, other drugs, pateint factors (CO, temp, ventilation + redistribution)
The partial pressure of inhalant in the alveoli parallels the concentration of inhalant in the brain, as long as cardiac output is adequate.
if a higher dose of inhalant is delivered at the start of anesthesia, the drug level in the brain will increase more rapidly, resulting in a faster time to effect.
iso MAC 1.3
circuits
- rebreathing
Use of a CO2 absorbent to remove CO2 from system, therefore allows exhaled gases to be re-inhaled (soda lime etc)
Incorporates one way valves to prevent rebreathing of expired CO2
increased flow rate (1L/min) creates a semi-closed circuit with pop-valve open
closed circuit = low flow acccording to metabolic need with pop-valve closed
dead-space in circle circuit may cause CO2 re-breathing in small patient, thus not use if <5kg - non-rebreathing
prevent rebreathing of CO2 by high O2 flow rate > rebreating of expired aire reduced due to high incoming gas rate
recommended flow rate 3 x minute volume (15ml/kg)
offer minimal flw resistance and dead space, thus ideal for small patients
T=piece, bain - ventilator
IPPV can supplied by manual or mechanical
indications: hypoventilation (hypercapnia)
hypoxaemia
atelectasis
monitoring equipment
Ga must maintain:
- DO2 (CO and O2 content)
- acid-base (ventilation)
- narcosis, analgesia + muscle relax
- temperature
induction can casue apnea and hypoventilation
1.depth: (jaw/eye/hr/rr)
2.blood pressure
BP is idirect measure of CO (therefore DO2)
if BP <60mmhg, DO2 and tissue perfirsion likely insufficent to kidney and brain (prolonged hypotension result in reduce brain function and AKI)
INDIRECT: less accurate/precise, affected by (cuff size, movement, position), dopppler or oscillometric
DIRECT: arterial catherisation, complications (haemorrhage, thrombosis)
- ECG (arrythmia, electrolyte imbalance)
- ventilation
drugs cause reduce ventilation > hyopventilation/hypercapnia (increase CO2)
hypercapnia results in: resp. acidosis, vasodilation, increase ICP, arrythmias
aveolar CO2 approx arterial CO2
ET-CO2: capnograph, WNL 35-65mmHg, monitors vent as well as (extubation/leak, cardiac arrestm resus effort, CO2 rebreathing)
PULSE-OX: estimates % of Hb that are saturated with O2, patient breathing 100% O2 should have spO2 100% . PaO2 checked if <98%
inaccurate dt (vasoconstriction, reduced CO, anaemia, hypothermia, hypervolaemia)
5.CVP
indection = rik of fluid overload (heart or kideny dz), hypavolaemic
measure vascular volume (cr. vena cava via jugular)
measure indirect arterial P with manometer (0-5mmHg)
ET CO2 + pulse Ox
- phase 0- inspiration, 0mm Hg
- phase 1- start expiration, increase in waveform
- phase 3- end expiration, CO2 peak
- phase 4- just before inspiration, fresh gas 0 mmHg
pulse ox: 100% inspired O2 =PaO2 500 mm Hg. Fall to less than 90 mm Hg to show a change in the pulse oximeter reading
opiods
act on 3 receptors (m, k, d)
- µ-receptor regulates the majority of clinical effects, including analgesia and side effects
- δ-receptor seems to primarily play a modulating role on the µ-receptor
MOA: triggers influx of K+ and decrease in intracellular Ca++ > decreases substance P and glutamate which hyperpolarizes post synaptic cell > decreases pain signaling
MAC sparing in GA
pros: minimal CV effects
SE: ileus, nausea/V+, regurgitation, excitment
resp depression under GA
reverseal: naloxone or butorphanol
morphine (12-24hr epidural)
methadone (3-4hr)
hydromorphone
fentanyl (CRI or transdermal) 40min bradycardia/apnea after bolus
Tramadol: Codeine analogue with weak μ receptor, Analgesic effects due to serotonin and adrenergic receptor effects within the central nervous system
buprenorphoine (partial agnoists) 4-6hr
butorphanol (κ-receptor agonist; µ-receptor antagonist) 1/2-2hr
sedatives -benzo
ii. Benzodiazepines: enhance the effects of GABA channels which is an inhibitory neurotransmitter within the CNS
a. Cause muscle relaxation, narcosis, amnesia, no analgesia, anti convulsant
b. Do not cause CV or respiratory depression
c. Schedule III
d. Reversal Flumazenil
Diazepam
a. Lasts 2 hours, adsorbs to plastic tubing and sensitive to light
b. IV, IM, PO, rectal
Midazolam
a. Lasts 1 hour
b. Breakdown products not effective (unlike diazepam), better for liver disease
Acepromazine
- Depresses dopamine in the reticular activating system
- Lasts 4-6 hours, moderate sedation, some muscle relaxation
- α-1 antagonist: hypotension, protects the heart from some arrhythmias
α2 agonists
decrease norepinephrine release in the CNS
- sedation, analgesia, muscle relaxation
- some α1 activity causes vasocontriction, hypertension, arrhythmogenecity, and paradoxical excitation, hyperglycemia, diuresis, and respiratory depression
- Can see reflex bradycardia and subsequent hypotension
Xylazine
a. α2: α1 = 160:1, lasts 12-20 mins
b. Initial hypertension followed by hypotension, induces vomiting in cats
c. 44x increase in cardiac arrest in dogs; 92X increase in complications
Medetomidine
a. α2: α1 = 1600:1, lasts 60-90 mins
b. hypertension and reflex bradycardia, can cause arousal and aggression
c. analgesia and sedation
d. Cats: minimal hypertension although HR, CO, SV decrease
e. profound depression of cardiac output > healthy animals only
Dexmedetomidine
a. Same as previous except twice as potent, may cause less sedation and last slightly shorter
Drugs for Induction
Propofol:
agonism of GABA receptors
- Works in 30-60 seconds
- Rapidly redistributed and metabolized, safe for patients with liver disease
- Vasodilation/hypotension and occasionally compensatory tachycardia, apnea
- Preoxygenation prolongs effect
- Oxidative damage to red blood cells in cats
ketamine
- Antagonism of NMDA receptors
- dissociation between higher brain functions and unconscious functions
- Muscle rigidity common so often given with benzo for induction
- May induce salivation
- can increase myocardial work, increases intracranial and intraocular pressure
- In patients with shock it decreases CO
- Renal elimination
- May decrease dorsal horn windup responsible for hyperalgesia
Alphaxalone
- Steroid anesthetic enhancing GABA and glycine CNS depression
- Depresses CO but no clinical respiratory depression
Inhalant Anesthesia
Unknown MOA: likely influence receptor lipid bilayer
Minimum alveolar concentration (MAC): concentration (vol/vol percent) required to prevent purposeful movement in response to standard painful stimulus in 50% of normal patients. Surgical stimulus more intense
MAC iso: 1.3-1.7 sevo: 2.1-3.1
isoflurane, sevoflurane having 0.2%, 2% of their total amount being metabolized by the liver.
Side effects:
hypotension due to decreased CO and SVR, respiratory depressant,
increased intracranial pressure,
disrupted thermoregulation,
malignant hyperthermia
Local anaesthetics
atropine
neuromuscular blockade: atricurium
Lidocaine/bupivacaine
MOA: Dose and activity dependent blockade of fast sodium channels on afferent nerves
Lido: lipophilic, fast onset (5mins), lasts 45-60mins,
Bupiv: higher lipid solubility, lasts 6-8 hours, takes 45 mins to exert effect, cardio toxic IV
associated with chondrotoxicity
Can be used in thoracostomy tubes (1.5mg/kg q6-8)
Anticholinergic Agents: atropine, glycopyrrolate
Parasympatholytics: minimize vagal tone which decreases HR and BP
Pressors and Inotropes
- Many anesthetics impair vascular tone and CO -> low BP
- CO can be low because
1. low preload (hypotension)
2. poor contractility
3. excessive afterload (severe vasoconstriction)
Inhalent anesthetics and propofol
o Tx with positive inotropic drug
* Dobutamine (5-10mcg/kg/min) or dopamine (5-12mcg/kg/min)
* B-adrenergic agonists, Chronotropic effect on heart
Opioids -> vagally induced bradycardia
o Tx symptomatic (atropine, glycol)
Vasodilation -> relative hypovolemia
Tx
1. Usually responsive to fluid boluses
* Isotonic crystalloids (5-15ml/kg bolus) or isotonic colloid (2.5-5ml/kg bolus)
2. Decrease inhalant, use other adjunct drugs such as fentanyl
3. Reverse vasodilation a-Adrenergic vasopressors phenylephrine (0.5-1.5mcg/kg/min)
Cardiac dz
aimed at preserving cardiac output and systemic O2 delivery
RAAS activated -> increased BP and increased intravascular fluid retention and hypervolemia
HCM: diastolic dysfunction
DCM: systolic dysfunction, reduce contractility
MVD: regurgitant fraction, decreasing forward CO, spectrum of presentation
PDA o Branham reflex
* Associated w ligation of PDAs
* Reflexive decrease in HR after ligation of ductus arteriosus due to an abrupt increase in afterload
consdierations:
echo before sx
pre-O2
reduce stress
reduce IVFT dt overload risk
give medication except ACEI
premed: opiod +/- benzo
NOT (ACP/ketamine/medetomadine/atropine)
induction: propofol or alfaxan (will cuase vasodilation) +/- benzo to reduce doses
maint: ideally low MAC + mutimodal agens (fentanyl CRI, nerve blocks)
positive ionotropes to increase BP
procainamide for ventricular arrythmia
endocrine dz
thyroid
- carcinoma removal > monitor for laryngeal paralysis
- avoid ketamine in hyperthyroid
diabete mellitus
- 1/2 insulin dose morning
- monitor Glu q 1hr during sx (dextrose on hand)
insulinoma
- BG q 30min
- May use glucagon (5-13ng/kg/min) to help normalize BG after prolonged hypoglycemia, but may also drive insulin release
Adrenal gland
- phaechormocytoma have inc risk arrythmia/tachycardia,
- a-adrenergic blockade drugs (phenoxybenzamine) for ~1wk before anesthesia
- increased risk infection
- PU may lead to hypovoalemia
- adrenelectomy: peri-op pred
- haemorrhage risk > blood type/x-match
- * Nitroprusside for hyerptension
* Lidocaine for arrhythmias
premed: opiod + benzo (no ACP)
Respiratory dz
- Upper airway disease- difficult to intubate
- Pleural space disease- decreased residual capacity and tidal volume; rapid hypoxia after premeds
a. Thoracoscopy- may require higher resp rates
b. Chronic chylothorax- fibrosing pleuritis; monitor peak airway pressures (<10cm H2O) - Lower airway- asthma, bronchoconstriction, expiratory dyspnea and hyperinflated lungs; use bronchodilators
- Parenchymal disease- V/Q mismatch, hypoxemia, dyspnea, not usually hypercapneic
pre-op: rads/stabilise, blood gas (hypercapnia/hypoxia)
consdierations:
pre-oxygenate,
BOAS (no opiod, antiemetics/gastric protectants, vagal tone, delay extubate)
difficulty entubation (have tracheostomy ready)
premed: ketamine/benzo + ACP (monitor for hypovent)
induction: propofol (short actig + fast) ideal for BOAS
maint:
Thoracotomy
Bupivicaine 1.5mg/kg q8 locally; LS epidural- 0.2mg/kg morphine diluted to 0.3mL/kg volume
Likely to need PPV and PEEP
TIVA- fentanyl + propofol
Reexpansion pulmonary edema
start with peak pressure of 10cm H2O, slow inc
Post op
O2 at 100mL/kg/min via nasal cannulas = 40% FIO2
Combine sedation and analgesia for smooth recovery
monitor: ETCO2 + PaCO2 (ventilation)
SPO2 (oxygenation) + PaO2 (Hypoxaemia)
Hepatic dz
Evaluate function by:
- Albumin, total bili, glucose, BUN, and cholesterol
- Pre- and post-prandial bile acids
- Coagulation profile (If coagulopathic, FFP at 10ml/kg starting dose)
- Hepatic encephalopathy d/t shunts, microvascular dysplasia, or hepatic failure
- Decreased oncotic pressure from failure to produce proteins (albumin)
> Normal oncotic pressure = 18-22mmHg
> reduce Blood volume
consdierations
1. Ascites
- Increased pressure on diaphragm
- decreased functional residual capacity and ETV
- Ascites at equilibrium with intravascular > rapid removal > hypovolemia
2. hypoglycaemia
3. prolonged drug effect
diazepam: sedative effects prolonged
midazolam: less, choice with hepatic disease
4. reduced protien/decrease drug bound thus less dose
> Opioids, benzos, and Propofol bind to albumin > less drug required or increased sensitivity
5.Biliary tree manipulation > increased vagal tone so have anticholinergics, pressors ready
6. blood type
Premed: hydromorphone (do not require P450 microsomal enzymes) or fentanyl + Midazolam
- ½ regular dose starting point; pre-oxygenate
Induction: propofol (extra-hepatic metab)
Maintenance: inhalants (minimal hepatic metab)
> Remi-fentanyl CRI in addition to inhalant due to metabolism by plasma esterases and not hepatic biotransformation
Renal dz
Chronic renal failure
- 75% nephron dysfunction before visible on chemistry
- dehydration (polyuria, polydipsia)
- hypokalemia
- metabolic acidosis
- muscle wasting
- anemia (PCV < 20% result in reduced DO2)
Acute renal failure
- Vomiting, lethargy, overhydration,
- hyperkalemia
- metabolic acidosis
consdierations:
- 24 hr IVFT prior to anesthesia if elective
- NSAIDs contraindicated
- hypertensive or hypotensive (monitor BP)
- Caution with ketamine, benzos, opioids, and acepromazine
- Hyperkalemia (calcium gluconate 50-150mg/kg IV slowly, insulin, Glucose)
- monitor UO
Premed: opioids + acepromazine produces an effective neuroleptanalgesic effect
Induction: propofol
* Avoid ketamine unless obstruction rapidly resolved
Maintenance: inhalants
- Urine output decreased
- Mannitol 0.5g/kg IV – free rad scavenger can reduce swelling of renal epithelial cells and flush renal tubules
- Furosemide 0.2-2mg/kg IV or CRI 0.66mg/kg/hr
sepsis
- Inadequate oxygen delivery to tissues
- Distributive shock (relative hypovolemia)
> Compensatory shock – increased CO
> Decompensatory shock - cardiovascular collapse
consdierations
- Relative adrenal insufficiency
- inability to generate SVR
Premed: frequently not necessary
Avoid acepromazine and alpha 2 agonists
Induction: neurolept combo
Hydro 0.2mg/kg + diazepam 0.5mg/kg + ketamine 2mg/kg
Propofol 0.25-1mg/kg
Maintenance: multimodal
Fentanyl CRI 5-60mcg/kg/hr
Ketamine or lidocaine
- Laparoscopy
maximum allowable intraabdominal pressure (IAP) is 14 cm H2O
- above this threshold, renal blood flow, AKI
- increased intrathoracic pressure + hypoventilation (exacerbated by Trendelenburg (head-down) positioning)
- increased CO2 absorption may increase ETCO2 and PACO2
- reduce venous return and therefore BP
o Clinical signs of an air embolus include a sudden drop in the ETCO2 tracing, as well as a drop in blood pressure
o Therapy for air embolism:
- CPR (drive the air from the right ventricle > lungs)
- placing the patient in left lateral recumbency
C-section and neonates
- Cesarean Section (C-Section)
o only anesthetic drug that has been shown to adversely affect neonate survival is xylazine - Neonatal Patients
- heart rate is an important determinant of cardiac output
- anticholinergics are recommended
- sensitive to the resp depressant effects of opioids and inhalant anesthetics
- food withheld 2 to 4 hours
- dextrose (2.5% to 5%) may be necessary
- poorly developed liver function and renal concentrating ability consdier drugs
full or partial opioid agonist + midazolam induction with propofol,
maintenance with isoflurane
- ORTHOPEDIC
aggressive
consdierations:
potent opiod
local anaesthetic bloskcs
MAC sparing/multimodal
- total ear canal ablation or limb amputation, a soaker catheter can be fashioned
bupivicaine + morphine (0.1mg/kg) total volume 0.2 mL/kg
- procedures below the elbow are suited for local anesthesia using a brachial plexus block
- hindlimbs, lumbosacral epidural analgesia is
0.2 mL/kg should be adequate for analgesia of the hindlimbs
0.3 mL/kg can be used to provide adjunctive analgesia for abdominal or thoracic procedures
dexmedetomidine (0.01 to 0.02 mg/kg) and an opioid, monitor V+ and resp
anaesthetic complications (8)
V/Q ventilation/perfusion
1.hypothermia: due to reduce hypthalamic regulation + vasodilation
can result in: pronlonged recovery, reduce immmune, alterned drug metab, prolonged healing
TX: warm peripherals
2.hypoxaemia
causes: R>L shunt, V/Q mismatch, hypoventilation (during recovery)
V/Q most common, result in venous admixture (Interruption of pulmonary blood flow, or areas of lung collapse from disease or atelectasis)
TX: IPPV, increase O2
3.hypotension (pressor and inotrope)
4.hypercapnia
PaCO2 >85mmHg sympathetic stim wanes and bradycardia, ventricular arrhythmias, hypotension, narcosis, circulatory collapse
ETCO2 essential (+/- PaCO2)
machine cause: exhausted soda lime, iadequate O2 flow
patient cuases: hypoventilation (reduce RR or TV)
Tidal Volume = 8-12 mL/kg
5.malignant hyperthermia
Inherited condition (deficit in ryanodine receptor – involved in calcium release in muscle)
extreme hypermetabolic state during GA
hypercarbia
hyperthermia
muscle rigidity
can lead to arrhythmias and death
Dx: abrupt increase ETCO2 with inc HR and temp
TX: TIVA, dantrolene
6.cardiac arrest
Prolonged cardiac ischemia dt hypotension, anemia, hypoxemia
ETCO2 ID cardiac arrest (no ECG)
Tx: CPR (compressions, No more than 12 breaths per minute, atropine 0.05mg/kg, adrenaline 0.01mg/kg, V-fib > electrical defibrillation
7.tracheal tears
cause pneumothorax, pneumomediastinum, subcut emphysema
more common in cats dt ETT cuff
8.reflux
cause esophagitis (stricture risk)
to prevent aspiration > suction, check pH +/-lavage
metoclopramide CRI, omeprazole
Epidural anesthesia and analgesia in small animal practice: An update
F. Garcia-Pereira
extending the hind limbs cranially yielded an increase of close
to 100% on the cranial-caudal distance from the dorsal facets of the
lumbosacral space
The sacrococcygeal intervertebral space may also be used for
epidural delivery of drugs, which is beneficial, especially in cats (perineum)
assist in epidural
space identification, the two most commonly used are the
“hanging drop” and loss of resistance (LOR)
Distribution after epidural administration is not always
bilaterally homogeneous,
Effect of two different pre-anaesthetic omeprazole protocols on gastroesophageal reflux incidence and pH in dogs
Lotti 2021
prosepective
Omeprazole administered the evening and 3 hours before anaesthesia increased gastroesophageal reflux pH and decreased the incidence of strongly acidic reflux in dogs.
A single dose of omeprazole given the evening before anaesthesia had no effect on reflux pH.
Bendinelli 2019 – pre-op meloxicam vs robenacoxib after lap- and lap-assisted OHE
robenacoxib: composite pain score higher at 24hr, more dogs required rescue analgesia
- meloxicam more effective for pain relief
In the context of randomized controlled clinical trials, placebo
responses are improvements documented in a negative control
group (e.g. a group with no active intervention). The improvements
can be real for the patient, such as those associated with
regression-to-the-mean or a placebo by proxy (‘better care”)
effect; or merely perceived by the caregiver, such as those
associated with a care-giver placebo effect
CBPI
developed and validated in dogs with multiple joint OA receiving a systemic
analgesic (non-steroidal anti-inflammatory, NSAID)
Quality of life
variety are reported in the literature, with reference to chronic pain, most are not validated
Gait analysis
objective outcome measure that directly measures the function of the patient > directly ascribed to pain and pain relief where pain is causing the alteration in function (i.e. not mechanical).
when the biases that influence analysis are well controlled, can be both precise and accurate.
However, evaluation of clinical studies suggests there is room to improve in quality control and data evaluation, interpretation and reporting.
Overall, natural variability in ground reaction forces 5.0% or 10.0% is rare. Thus, changes in ground reaction forces of this amount are clinically important when associated with intervention because they rarely occur spontaneously.
Intraperitoneal and incisional analgesia in small animals: simple, cost-effective techniques
P. V. M. Steagall
Local anaesthetics inhibit membrane depolarisation, nerve excitation and conduction primarily by blocking inward Na+ currents through voltage-gated Na+ channels
bupivicaine: should be used for any type of abdominal surgery such as intestinal foreign body removal, enterotomy, splenectomy, etc.
IP and incisional anaesthesia
are simple, safe and cost-effective adjunct methods to reduce
pain after abdominal surgery in companion animals and are not
limited by geographical drug availability. However, readers should
be aware that some of our recommendations were based on a consensus
and low-level of evidence provided by the current literature
Validated pain scales
Glasgow feline/Canine composite measure pain scale
Feline Grimace Scale for acute pain assessment.
owner reported
CBPI, COI and LOAD sufficient evidence to support validity
Randomized controlled trial of pregabalin for analgesia
after surgical treatment of intervertebral disc disease
in dogs
Schmierer 2020
Prospective, randomized, controlled clinical trial with a blinded
observer.
Animals: Forty-six client-owned\
Conclusion: Postoperative signs of pain after surgical treatment of intervertebral
disc herniation (IVDH) were reduced when dogs received perioperative
pregabalin rather than opioids alone.
Cadaveric evaluation of fluoroscopy-assisted placement of
one-lung ventilation devices for video-assisted thoracoscopic
surgery in dogs
Mayhew
Experimental study.
Sample population: Canine cadavers (n = 8) weighing between 20.2 and 37.4 kg.
Advancement of a left-sided Robertshaw
double-lumen endobronchial tube (DLT) and the EZ-blocker (EZ) were evaluated
Clinical significance: Fluoroscopy-assisted placement of EZ and DLT is a useful
alternative to bronchoscopy-assisted placement of these OLV devices.
Liposomal bupivacaine:
- reports of efficacy variable – some support in ortho procedures over bupivacaine/saline
no additional efficacy reported in soft tissue/abdominal sx - increased rate of incisional/injection-site inflammation
Rahn 2023 – effect of liposomal bupivacaine on opioid use and sx-site complications after GI-FB sx
- liposomal bupivacaine – labelled for up to 72hr analgesia
- liposomal bupivacaine → lower post-op fentanyl use and rates, time in ICU and hospital
- wound complications: 7/65 (10.8%) LB vs 4/140 (2.9%) control
Pownall 2021 – influence of pre-emptive local analgesia on chronic post-surgical pain (CPSP)
- CPSP present after TPLO in 41% - assessed by Helsinki Chronic Pain Index
Evaluation of the analgesic efficacy
of grapiprant compared with
robenacoxib in cats undergoing
elective ovariohysterectomy in a
prospective, randomized, masked,
non-inferiority clinical trial
Pisack 2024
These results indicate that grapiprant was non-inferior to robenacoxib for mitigating
postsurgical pain in cats after OVH performed via ventral celiotomy
Grapiprant
selective prostaglandin E2 (PGE2) receptor antagonist, and therefore its mechanism of action is distinct from the cyclooxy-
genase (COX) inhibitors.
The EP4 receptor is one of four binding
sites for PGE2. By only targeting the EP4 receptor, production of the
homeostatic prostanoids, such as PGE2 is not reduced to the extent
seen with the more traditional NSAIDs
Two doses of subcutaneous methadone for postoperative analgesia in dogs undergoing tibial plateau levelling osteotomies
Upchurch 2024
prospective, 17 dogs
Two doses of methadone at either 0.25 or 0.5 mg/kg administered via subcutaneous injections pre-operatively and 4 hours later, along with 4.4 mg/kg carprofen subcutaneously 8 hours after the first methadone dose appear to provide sufficient pain control for up to 12 hours in dogs undergoing tibial plateau levelling osteotomy.
can use lower dose of methadone.
Bupivacaine liposomal injectable suspension
does not provide improved pain control in dogs undergoing abdominal surgery
Hixon 2024
BLIS or saline surgical incision infiltration
Use of BLIS for exploratory laparotomy did not provide improved pain control over postoperative opioid administration alone. Patients that received BLIS had no increase in short-term complications.
does not increase the chance of surgical site infection
Success of placement and
complications during v-gel
placement and maintenance
of anaesthesia
Kathrin Hecker-Turkovic 2022
Placement was possible at the first attempt in 136 cats, at the second attempt in eight cats
In about 7% of
the cases, replacement of the device was required due to mispositioning or dislocation
Effect of bupivacaine concentration and formulation on
canine chondrocyte viability in vitro
Rengert 2021
Controlled laboratory study.
in vitro toxicity of preservative-free bupivacaine concentration dependent
- clinically relevant concentrations may not → chondrotoxicity in vitro
- liposomal encapsulated bupivacaine → time-dependent chondrotoxicity
- not recommended for intra-articular use
Success Rate and Perioperative Complications of
Lumbosacral Extradural Anaesthesia in Dogs
Undergoing Total Hip Replacement: A Double-Centre
Retrospective Study
Inga Viilmann 2022
0.5% levo-/bupivacaine + morphine/buprenorphine
- success = low fentanyl CRI requirement, no additional analgesic infusions/opioids for 3hr
- success rate: 88.7%
- complications: intra-op: hypercapnia (75.2%), hypotension (46.1%), hypothermia (27.7%) regurgitation (6.3%)
short-term (<24hr): urinary retention (17.8%), sciatic neurapraxia (5.8%)
vomiting/regurg/diarrhoea (8.2%)
post-op: hip luxation 3/206 (1.5%) at 48hr (2) and 72hr (1)
cannot categorically rule out that some of them were intrathecal,
