AMVAC/RoSAVA 2014 How and why to do an epidural in dogs and cats? Which Indications and which drugs? Prof. Yves Moens Dipl ECVAA
Why do epidurals? A part of a balanced anesthesia A means to provide analgesia
Terminology is injection in the extradural space Peridural Extradural
Terminology injection in the subdural space subdural Subarachnoidal Spinal
Materials needed Anaesthetic Drugs Saline Spinal needle Ordinary needle Syringues : for drugs / for saline
Materials needed
Spinal needles 22 GA (O.7 x 40 mm) 22 GA (O.7 x 75 mm) 22 GA (O.7 x 120 mm) The mark on the needle hub indicates the direction of the bevel opening
Preparation and Clipping? Large area or conservative? (asepsis) Inform / consult the owner!!!! cases of slow hair regrowth cases of changed hair pigmentation
Positioning? Dorsal Recumbency Lateral recumbency
Where?: foramen lumbosacrale Liquor Dura Cauda equina Venous plexus! Dural sac is longer in the cat than in the dog!
landmarks for the foramen
landmarks for the foramen
Landmarks for the foramen TAIL
Where?: foramen lumbosacrale Dog 1/2 Cat 1/3
Landmarks for the foramen
Extradural penetration: how do I know? The pop -feeling (trough Lig. Flavum) The hanging drop technique The loss of resistance to saline or air
The Pop feeling POP!!
The Hanging drop sign The aspiration of fluid from the needle hub due to subatmospheric pressure in the extradural space Not always! Never in lateral recumbency If present: correct location If not present: no information
The Loss of resistance - test (LOR) Ideally with special syringues LOR-test preferred with saline Introduce an air bubble compression: false no change: correct!
The Loss of resistance - test (LOR)
how to proceed : part 1 Palpate the landmarks Advance the needle in direction foramen Pop feeling? If yes: adequate length of insertion of the needle? If yes: remove the stylet - LOR-test with saline If positive: inject slowly the drugs
how to proceed : part 2 Palpate the landmarks Advance the spinal needle in direction of the foramen Pop feeling?: No Touch bone? Yes adequate length of insertion of the needle? yes Withdraw a few mm Remove the stylet - LOR-test with saline If positive: inject slowly the drugs We have hit the bottom of the spinal canal
how to proceed : part 3 Palpate the landmarks Advance the spinal needle in direction of the FO Pop feeling?: No Touch bone? Yes Adequate length of insertion of the needle? NO walk the bone until sudden further penetration Touch bone again? Withdraw a few mm Remove stylet -LOR-test with saline If positive: inject slowly the drugs
walk the bone
walk the bone
problems Blood from the needle hub? abort Cerebrospinal fluid from the needle hub: inject slowly half the dose position head high No local anaesthetics spinally in hypovolemic patients Inject slowly
An Example 1
An Example 2
Contraindications for epidural analgesia Coagulopathies Severe bacteremia Infection at the site of needle placement Lumbosacral fractures or dislocations Thoracolumbal neurologic deficits Hypovolemia (to be corrected!!)
Advantages of epidural analgesia Long lasting pain relief possible (>10 hrs) not limited to the hindquarters!! somatic and visceral pain Can simplify pain management Less systemic side effects of epidurally administered analgesics less cardiorespiratory side effects less sedative side effects No or less systemic analgesics needed facit Y Moens
AMVAC/RoSAVA 2014 Disadvantages Risks of the epidural technique itself Infection mechanical or chemical damage to the cord Often need for heavy sedation or short general anesthesia to perform Side effects of the epidural drugs For prolongation repeated epidural puncture and injection necessary Increased risk facit Y Moens
AMVAC/RoSAVA 2014 Common drugs Opioids: MORPHINE Interfere with nociceptive processing by binding to opiate receptors in the dorsal horn of the spinal cord Local anesthetic: BUPIVACAINE stop nerve conduction and thus ascending nociceptive input by blocking ion channels of the nerve membranes wher they leave the spinal cord facit Y Moens
AMVAC/RoSAVA 2014 Common drugs : morphine More hydrophilic opioid easy cranial spread up to the forelimb-level!! slow onset (1-2 hrs) long action (10 hrs) No motor blockade! Side effects are seldom Interference with urination: bladder atony (m.detrusor) Bladder control necessary: assistance/catheter might be necessary facit Y Moens
Common drugs : bupivacaine motor blockade! 0.125 % < 0.25 % < 0.50 % quick onset (30 min) medium duration (4-6 hrs) autonomic blockade sympathicolysis and vasodilation risk for hypotension!!! If hypovolemic!! cranial spread depends on dosis and volume and body position up to mid thoracic level nociceptive block not always complete facit Y Moens
AMVAC/RoSAVA 2014 Common individual drug doses First choice : Morphine: 0.1-0.2 mg/kg Second choice: Bupivacaine: 0.25-0.5 mg/kg (degree of motor block) Drug volume: analgesic drugs are diluted if necessary to make up a volume of 0.1 ml to 0.2 ml/kg (cranial spread ± influenced ) facit Y Moens
Morphine PLUS bupivacaine Synergistic effect!! More analgesic potency Longer duration Reduction doses of individual drugs In presence of morphine bupivacaine 0.125 % or even 0.06 % can be used. eg 50/50 mixture of morfine (1mg/ml) and 0.25% bupivacaine can be used facit Y Moens
AMVAC/RoSAVA 2014 Some indications for epidural analgesia All trauma /surgery hind part of the body Limb amputations (for-and hindlimb) Thoracotomy - trauma thoracic wall Pancreatitis Peritonitis facit Y Moens
AMVAC/RoSAVA 2014 Remarks Cats: lower doses and volumes in general Use by preference preservative free drugs Inadvertent spinal puncture (csf fluid): abort or reduce the dose Systemic analgesics (can)remain necessary but at lower doses No cook book: pain evaluation (scoring) is the key of good pain management!!! facit Y Moens
AMVAC/RoSAVA 2014 Epidural analgesia via an epidural catheter Not the first procedure to learn Severe pain expecting to last long Same contraindications as epidural needle injection Absolute sterile conditions during placement 3 days in place is common Specific risks related to epidural catheter Protection to prevent removal by animal facit Y Moens
AMVAC/RoSAVA 2014 epidural analgesia via an epidural catheter 1 facit Y Moens
AMVAC/RoSAVA 2014 epidural analgesia via an epidural catheter 2 facit Y Moens
AMVAC/RoSAVA 2014 Questions possible but facit Y Moens
AMVAC/RoSAVA 2014 conclusion Epidural application of analgesic drugs is relatively simple The combination of drugs that act upon (loc anesth) and in (opiod) the spinal cord is synergistic Goal is improved analgesia with less side effects and faster recovery of normal behaviour the gain outweight the risks facit Y Moens
AMVAC/RoSAVA 2014 problems Blood from the needle hub? abort Cerebrospinal fluid from the needle hub: inject slowly half the dose position head high No local anaesthetics spinally in hypovolemic patients Inject slowly facit Y Moens
An example:dog sternal Cat lateral facit Y Moens
AMVAC/RoSAVA 2014 An example: Dog lateral facit Y Moens
AMVAC/RoSAVA 2014 An example:: Cat lateral facit Y Moens
AMVAC/RoSAVA 2014 epidural analgesia via an epidural catheter 3 facit Y Moens