Page 2213 - Cote clinical veterinary advisor dogs and cats 4th

1100.e2 Epidural Analgesia/Anesthesia

Epidural Analgesia/Anesthesia Client Education
Sheet
VetBooks.ir Preparation: Important

• Use of potent parenteral or systemic
Difficulty level: ♦♦
vasodilators Checkpoints
Synonym • Base dosages on lean body weight.
Extradural blockade Equipment, Anesthesia • Consider ratio of each component: opioid,
Most animals that receive an epidural are local anesthetic, alpha-agent, ketamine, and/
Overview and Goals heavily sedated or under general anesthesia or others; total volume should not exceed
Administration of drugs into the epidural space at the time of administration. Premedication 0.2 mL/kg.
to provide decreased sensory and sympathetic with both anxiolytic and analgesic drugs • Positioning of animal: sternal recumbency,
pain transmission, modulation (analgesia), and/ (opioid, alpha-agonist) is recommended even with hindlimbs pulled fully cranially
or complete motor blockade (anesthesia). Drugs if continued progression into general anesthesia under body or else flexed and stable under
can be administered in a single dose, repetitively, is not anticipated because of the pain of pelvis (frog-legged position). Because aged,
or by continuous infusion by catheter: positioning, approach, and administration of debilitated, or traumatized animals may be
• Epidural analgesia: injection of an opioid, epidural agents. uncomfortable in either position, lateral
a phencyclidine, an alpha-agonist, or a Equipment: positioning is also used. Obese animals are
nonsteroidal antiinflammatory drug • Hair clippers best placed in sternal recumbency because of
• Epidural anesthesia: injection of a local • Surgical scrub solution, isopropyl alcohol or ease in identifying LS space and for optimal
anesthetic saline, gauze/sponge oxygenation and ventilation.
• Epidural or spinal needle (Quincke, Hustead, • Premedication for surgery, general anesthesia,
Indications or Tuohy needles) 22 to 20 gauge; 1 - to or procedural sedation suggested below
2
Cesarean section; thoracotomy; pelvic, hindlimb, 3 2 -inch, small hypodermic needles (22 ○ Dexmedetomidine 3-10 mcg/kg canine,
1
perineal, or tail orthopedic manipulations; gauge) can also be used for smaller patients. 1-3 mcg/kg feline IM or IV, with
amputations (forelimb/hindlimb); abdominal • Sterile gloves ○ Midazolam 0.2-0.5 mg/kg IM or IV
procedures; diaphragmatic repair; pancreatitis; • Sterile saline for dilution of agents and either butorphanol 0.2 mg/kg or
peritonitis; intervertebral disc disease (IVDD); • “Test syringe” for saline and air mix hydromorphone 0.1 mg/kg IM or IV
management of chronic pain (e.g., lumbosa- • Syringe for administration of combination
cral [LS] disc disease, spinal or nerve root of local and/or opioid Possible Complications and
tumor) • A few 20-gauge needles (used for withdraw- Common Errors to Avoid
Advantages: ing drugs from vials) • The following can be seen with technical
• Lengthy, rapid-onset analgesia • Local anesthetics for epidural injection: difficulty in identifying (finding) the epidural
• Few systemic side effects due to limited 0.5% bupivacaine, 2% lidocaine, or 0.75% space: infection, hemorrhage, spinal or nerve
vascular uptake of substances ropivacaine (preferentially preservative free, root trauma.
• Reduced requirements for parenteral and must be epinephrine free) • The following can be seen with use of certain
inhalant analgesic/anesthetic drugs • Opioids for epidural injection: morphine, agents: respiratory depression, urinary retention,
• Alternative to general anesthesia for animals preferably preservative free (Duramorph, pruritus, nausea and vomiting (opioids), motor
at high risk Astramorph, preservative-free morphine); paralysis, systemic vasodilation (lidocaine or
buprenorphine, oxymorphone, hydromor- high doses of bupivacaine/ropivacaine).
Contraindications phone, dexmedetomidine, and ketamine may • Subarachnoid injection frequently results in
Absolute contraindications: also be used. superb analgesia but can cause respiratory
• Coagulopathy/bleeding disorder • A second operator (assistant) to allow strict depression.
• Localized infection/inflammation over entry attention to aseptic technique
to epidural space For epidural catheterization, the following also Procedure
• Increased intracranial/intraspinal pressure are required: • Find the entry site: The LS space is routinely
(head trauma, space-occupying mass) • Blunt-tipped, lateral-faced opening needle used for accessing the epidural space. It is
• Risk of or existing severe respiratory with curved bevel (Tuohy needle) identified by palpating the most craniodorsal
depression (phrenic nerve injury, tentorial • Continuous or indwelling epidural catheter aspects of each ilial wing, drawing an imagi-
herniation) • Injection port with screw or lock fitting to nary line between wings, and palpating the
Relative contraindications (requires alteration avoid inadvertent disconnection spinous process of L7 caudal to this line.
of dose, frequency, drugs, or placement site): • Sterile scissors to tailor-cut the catheter to The spinous process of L7 is smaller and
• Urinary retention proper length shorter than that of L6 and therefore is
• Meningitis, encephalitis, discospondylitis • Microfilter often more difficult to find, but it is always
• Severe anatomic/neurologic disturbance or • Sterile covering for site and/or part/total CAUDAL to this imaginary line. Staying
obesity at landmarks catheter (Tegaderm) directly on midline, the site of entry (LS
• Inexperienced administration • Suture material (3-0 nylon or other monofila- space) is identified by placing a fingertip on
Contraindications for use of local anesthetics ment, nonabsorbable suture) the spinous process of L7 and gently rocking
in epidurals: • Needle holders the finger caudally into the depression caudal
• Uncorrected hypovolemia or active • Suture scissors to the process. The needle entry site is in
hemorrhage this depression.
• Vasodilatory shock Anticipated Time • The animal is positioned appropriately, the
• Severe clinical cardiac disease or liver impair- • Experienced operator: 3-5 minutes approximate LS area clipped, and then asepti-
ment (third-space fluid disease, ascites) • Inexperienced operator, anatomic/animal cally prepped three times using alternating
• Acute kidney injury positioning issues, dermatologic uncleanli- chlorhexidine scrub and saline.
• Sympathetic disturbance (e.g., autonomic ness: 20 minutes; if it takes longer, consider • Sterile gloves are unwrapped, and the paper
disease, dysautonomia) alternative forms of analgesia instead sleeve is used as a sterile field; syringes,

www.ExpertConsult.com