Perioperative low dose

analgesic infusions

Dr Mike Foss

FANZCA FFPMANZCA

Aims of Peri-operative

analgesia

• Part of Holistic compassionate care

• Improved acute outcomes

• Reduce the burden of Persistent Post

operative Pain

• Reduce complications of surgery with

minimal side effects

• Manage short to long term complications

of therapy.

Persistent Post Operative Pain

• pain that “develops after surgical

intervention and lasts at least 2 months;

other causes for the pain have to be

excluded, in particular pain from a

condition preceding the surgery”

• Overall, the estimated incidence of severe

disabling pain after surgery is in the range

of 2–10%

Surgery and the chronic pain

patient/avoiding PPP

• Surgery – nice quick slickly done,

minimally invasive, nerve sparing

operation, in a high volume unit. Minimise

complications

• Anaesthesia and analgesia – Local

anaesthesic iv or regional, Nitrous,

Ketamine, NSAIDs…

• Patient factors– essentially not modified in

our current system

Opioid Husbandry

• North America “Bigger is better” in terms

of opioid therapy

• CDC Guideline for Prescribing Opioids for

Chronic Pain — United States, 2016

• A sea change in North American practice

to come more into line with the rest of the

developed world.

• ASRA purposing an “adjunct before

opioid” policy at most recent meeting

Adjuncts available peri

operatively in Canada

• IV NSAIDs (limited use to risk with renal

impairment in major surgery)

• Nitrous oxide

• IV magnesium

• IV ketamine

• Local anaesthetic

• (oral tramadol, clonidine, tylenol,

gabapentinoid)

Reducing Persistent Post

Operative pain

• Level One evidence for preventive effect

with ketamine and local anaesthetic (IV or

regional)

• Tylenol may also have a preventive effect

• Not shown for gabapentanoids or opioid

Ketamine

• NMDA receptor non competitive antagonist. High

trapping rate with slow off rate – leads to prolonged

tonic blockade

Ketamine Continued

• Advantages – Dissociative anaesthetic,

preventive analgesic/anti nociception,

opioid sparing, reduced PONV, maintains

airway tone/respiration. Antidepressant

effect

• Disadvantages – psychotomimetic effects,

abuse potential, long term bladder irritation

Ketamine continued

• Works on a multitude of receptors

• Potentiates opioid analgesia as well as

being an analgesic in its own right

• Change in gene expression which may be

responsible for anti depressant and anti

chronic pain effects

• Metabolised in liver to Norketamine then to

glucuronide conjugates – excreted in urine

• Elimination half time 3 hours

Ketamine cont

• Doses of less than 0.1mg/kg/hr

• Loading dose of 0.1-0.2 mg/kg

• Side effects can usually be managed by

reducing the infusion rate

Lidocaine

• Na Channel Blocker

• are opioid-sparing and significantly reduce

pain scores, nausea, vomiting and

duration of ileus after abdominal surgery

• Metabolised to MEGX (NA block and

?Anti-inflam properties) in liver, excreted in

urine

• Elimination half time 90-120mins

Lido cont

• Loading dose 1.5mg/kg

• Infusion rates variable 1.5-3mg/kg/hr

• Discussing a rate of 2mg/min for over 65

and 1mg/min for over 80 (or with risk

factors)

Glial effects

Multi modal in Recovery:

• Paracetamol – Cox 3/Endocannbinoids

• NSAIDs – Cox1/2

• Na Channel – Local anaesthetic

The 3 Prongs of the pain system:

1. Opioid (possibility of ultra low dose

naloxone)

2. Glutamate –

N20/Ketamine/Gabapentanoids

3. Descending inhibition –

clonidine/Tramadol

references

• Sleigh, J etal. Ketamine – more mechanisms of action than just nmda blockade.. Trends in

anaesthesia and critical care 4(2014) 71-81

• Tong Yuan etal. Lidocaine attenuates lipopolysaccharide-induced inflammatory responses in

microglia.. Journal of Surgical Research 192- 1 (2014) 150-162

• Loftus etal. Intraoperative Ketamine reduces perioperative opioid consumption in HOT patients..

Anaesthesiology V113 (3) 639-646.

• ANZCA/FPM. (2015). Other patient groups - the opioid tolerant patient. In P. Macintyre, D. Scott,

S. Schug, E. Visser, & S. Walker (Eds.), Acute Pain Management: Scientific Evidence (pp. 569-

571). Melbourne, Australia: Australian and New Zealand College of Anaesthetists 2015.

• ANZCA/FPM. (2015). Analgesic medications. In P. Macintyre, D. Scott, S. Schug, E. Visser, & S.

Walker (Eds.), Acute Pain Management: Scientific Evidence (pp. 69-178). Melbourne, Australia:

Australian and New Zealand College of Anaesthetists 2015.

• Khan, J. etal. (2015, September). An estimation of the appropriate end time for intraoperative

intravenous lidocaine infuion in bowel surgery; a comparative meta analysis. Journal of Clinical

Anaesthesia , http://dx.doi.org/10.1016/j.jclinane.2015.07.007 .

• Laskowski, etal. (2011, Oct). A systematic review of intravenous ketamine for post operative

analgesia. Canadian Journal of Anaesthesia , 911-923.

• IASP. Chronic pain after surgery. Pain – clinical updates, Volume XIX – 1, 2011. http://www.iasp-

pain.org/files/Content/ContentFolders/Publications2/PainClinicalUpdates/Archives/PCU_19-

1_for_web_1390260524448_6.pdf