This topic was selected because an evidence synthesis beats a textbook on it: the trials disagree, or the guidance has moved recently.
THE EVIDENCE
What each source contributes, and how strong it is
Study design first — a cohort and a randomised trial do not carry the same weight.
Design
Year
Journal
What it found
Guideline
2018
Regional anesthesia and pain medic
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
Meta-analysis
2018
The Cochrane database of systemati
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid
Randomised trial
2017
England)
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce
Cohort
2025
Anaesthesia
Ketamine's relationship with delirium is U-shaped
Meta-analysis
2022
Journal of clinical anesthesia
In patients already taking opioids, ketamine reduced cumulative opioid consumption
Randomised trial
2017
Pain
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced
6 resolved citations behind this deck; every point above traces to one of them.
WHERE THE GUIDANCE SITS
What the guidelines and pooled evidence say
3 findings, each on the slide that follows.
Regional anesthesia and pain medicine 2018
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a stand-alone treatment and as an adjunct to opioids, with…
The Cochrane database of systematic reviews 2018
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid consumption by about 8 mg morphine equivalents — roughly 19% — with…
Journal of clinical anesthesia 2022
In patients already taking opioids, ketamine reduced cumulative opioid consumption
In patients already taking opioids, ketamine reduced cumulative opioid consumption by roughly 97 mg at 24 hours and lowered sedation
WHERE THE GUIDANCE SITS
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
Guideline · Regional anesthesia and pain medic
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a stand-alone treatment and as an adjunct to opioids, with contraindications similar to those for chronic pain.
Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists, Regional anesthesia and pain medicine 2018 · PMID 29870457
WHERE THE GUIDANCE SITS
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid
Meta-analysis · The Cochrane database of systemati
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid consumption by about 8 mg morphine equivalents — roughly 19% — with bolus doses mostly 0.25 to 1 mg and infusions 2 to 5 micrograms per kilogram per minute.
Perioperative Intravenous Ketamine for Acute Postoperative Pain in Adults, The Cochrane database of systematic reviews 2018 · PMID 30570761
THE NUMBERS
Ketamine's opioid-sparing effect is modest but consistent
130 trials, 8,341 patients.
About 19% less opioid at both time points — real, and smaller than the enthusiasm suggests.
Perioperative Intravenous Ketamine for Acute Postoperative Pain in Adults, The Cochrane database of systematic reviews 2018 · PMID 30570761
WHERE THE GUIDANCE SITS
In patients already taking opioids, ketamine reduced cumulative opioid consumption
Meta-analysis · Journal of clinical anesthesia
In patients already taking opioids, ketamine reduced cumulative opioid consumption by roughly 97 mg at 24 hours and lowered sedation, while the effect on pain intensity itself was small and low-certainty.
Perioperative Ketamine for Postoperative Pain Management in Patients With Preoperative Opioid Intake: A Systematic Review and Meta-Analysis, Journal of clinical anesthesia 2022 · PMID 35065394
WHAT THE TRIALS FOUND
Where randomised evidence moved the question
2 findings, each on the slide that follows.
England) 2017
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce delirium in older adults after major surgery (19.5% versus 19.8%) and…
Pain 2017
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced 24-hour morphine consumption from 121 mg to 79 mg and reduced…
WHAT THE TRIALS FOUND
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce
Randomised trial · England)
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce delirium in older adults after major surgery (19.5% versus 19.8%) and increased hallucinations and nightmares with rising dose.
Intraoperative Ketamine for Prevention of Postoperative Delirium or Pain After Major Surgery in Older Adults: An International, Multicentre, Double-Blind, Randomised Clinical Trial, Lancet (London, England) 2017 · PMID 28576285
THE NUMBERS
PODCAST: no delirium benefit, more hallucinations
672 patients over 60 after major surgery.
No difference in delirium, and hallucinations and nightmares rose with dose — this is a negative trial.
Intraoperative Ketamine for Prevention of Postoperative Delirium or Pain After Major Surgery in Older Adults: An International, Multicentre, Double-Blind, Randomised Clinical Trial, Lancet (London, England) 2017 · PMID 28576285
WHAT THE TRIALS FOUND
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced
Randomised trial · Pain
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced 24-hour morphine consumption from 121 mg to 79 mg and reduced sedation, without more hallucinations or nightmares.
Intraoperative Ketamine Reduces Immediate Postoperative Opioid Consumption After Spinal Fusion Surgery in Chronic Pain Patients With Opioid Dependency: A Randomized, Blinded Trial, Pain 2017 · PMID 28067693
THE NUMBERS
In opioid-dependent patients the effect is larger
147 patients having lumbar spinal fusion.
Where tolerance is the problem, the opioid-sparing effect is worth having.
Intraoperative Ketamine Reduces Immediate Postoperative Opioid Consumption After Spinal Fusion Surgery in Chronic Pain Patients With Opioid Dependency: A Randomized, Blinded Trial, Pain 2017 · PMID 28067693
IN PRACTICE
Ketamine's relationship with delirium is U-shaped
Cohort · Anaesthesia
Ketamine's relationship with delirium is U-shaped: cumulative doses at or below 0.35 mg/kg were associated with less delirium, higher doses with none, and the minimum risk fell at 0.25 to 0.34 mg/kg.
Dose-Dependent Relationship Between Intra-Operative Ketamine Administration and Postoperative Delirium: A Retrospective Cohort Study, Anaesthesia 2025 · PMID 40619168
IN THE ROOM
What this changes about the next case
Colour is the strength of the evidence behind each step, not the urgency.
1
1
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a stand-alone treatment and as an adjunct to opioids, with contraindications similar to those for chronic pain.
2
2
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid consumption by about 8 mg morphine equivalents — roughly 19% — with bolus doses mostly 0.25 to 1 mg and infusions 2 to 5 micrograms per kilogram per minute.
3
3
In patients already taking opioids, ketamine reduced cumulative opioid consumption by roughly 97 mg at 24 hours and lowered sedation, while the effect on pain intensity itself was small and low-certainty.
4
4
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce delirium in older adults after major surgery (19.5% versus 19.8%) and increased hallucinations and nightmares with rising dose.
5
5
In opioid-dependent patients having lumbar fusion, intraoperative S-ketamine reduced 24-hour morphine consumption from 121 mg to 79 mg and reduced sedation, without more hallucinations or nightmares.
The oral-boards stem on the next slide puts these into one scenario.
KEY TAKEAWAYS
What to carry into the next case
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
Regional anesthesia and pain medicine 2018
Across 130 trials and 8,341 patients, perioperative ketamine cut 24-hour opioid
The Cochrane database of systematic reviews 2018
In the PODCAST trial a single subanaesthetic dose of ketamine did not reduce
England) 2017
Ketamine's relationship with delirium is U-shaped
Anaesthesia 2025
The ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
Questions I'll ask you in the room
How does your plan change if the patient is not optimised?
What is the physiology behind what we just did?
Talk me through the trade-off you made there.
What would make you abandon this plan and do something else?
Oral boards stem
A 48-year-old on high-dose oxycodone for chronic back pain presents for revision spinal surgery, and the resident proposes a low-dose ketamine infusion for the duration.
Board questions
1. The ASRA/AAPM/ASA consensus guideline addresses intravenous ketamine infusions for acute pain. In one or two sentences, state the two roles in which that guideline supports ketamine for acute pain, and how it characterizes ketamine's contraindications relative to those for chronic pain use.
Show answer
The consensus guideline supports ketamine for acute pain both as a stand-alone treatment and as an adjunct to opioids, and it states that the contraindications are similar to those for chronic pain.
Ketamine is endorsed by that consensus document in both roles, stand-alone and opioid adjunct, and you screen for the same contraindications you would apply in the chronic pain setting.
Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists, Regional anesthesia and pain medicine 2018 · PMID 29870457
2. A randomized, blinded trial gave intraoperative S-ketamine to opioid-dependent patients undergoing lumbar spinal fusion. State what happened in that trial to 24-hour morphine consumption (give both values), to sedation, and to hallucinations and nightmares.
Show answer
Intraoperative S-ketamine reduced 24-hour morphine consumption from 121 mg to 79 mg and reduced sedation, without an increase in hallucinations or nightmares.
In that opioid-dependent fusion population the trial showed a roughly 40 mg morphine reduction over 24 hours and less sedation, with no excess hallucinations or nightmares.
Intraoperative Ketamine Reduces Immediate Postoperative Opioid Consumption After Spinal Fusion Surgery in Chronic Pain Patients With Opioid Dependency: A Randomized, Blinded Trial, Pain 2017 · PMID 28067693
3. In the PODCAST trial, older adults having major surgery received a single subanaesthetic dose of ketamine intraoperatively. State the trial's finding for postoperative delirium, giving both event rates, and state what happened to hallucinations and nightmares as the dose rose.
Show answer
A single subanaesthetic dose of ketamine did not reduce delirium in older adults after major surgery, 19.5% versus 19.8%, and hallucinations and nightmares increased with rising dose.
PODCAST is the reason not to give ketamine for delirium prevention: no reduction in delirium at all, and more hallucinations and nightmares as the dose went up.
Intraoperative Ketamine for Prevention of Postoperative Delirium or Pain After Major Surgery in Older Adults: An International, Multicentre, Double-Blind, Randomised Clinical Trial, Lancet (London, England) 2017 · PMID 28576285
4. A systematic review and meta-analysis of perioperative ketamine in patients with preoperative opioid intake reported a large reduction in cumulative opioid consumption. A resident concludes from it that ketamine clearly makes these patients hurt less. Using only what that meta-analysis reported, state what it actually found for opioid consumption, sedation, and pain intensity, and comment on the certainty of the pain finding.
Show answer
It found that ketamine reduced cumulative opioid consumption by roughly 97 mg at 24 hours and lowered sedation, but the effect on pain intensity itself was small and low-certainty, so the resident's conclusion overstates it: the robust signal is opioid sparing, not a demonstrated meaningful reduction in pain scores.
Opioid-sparing and less sedation are what this meta-analysis supports in opioid-tolerant patients; the effect on pain intensity itself was small and low-certainty, so do not promise the patient less pain on this evidence.
Perioperative Ketamine for Postoperative Pain Management in Patients With Preoperative Opioid Intake: A Systematic Review and Meta-Analysis, Journal of clinical anesthesia 2022 · PMID 35065394
The bottom lineThe ASRA/AAPM/ASA consensus guideline supports ketamine for acute pain as a
Sources
[1] Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists, Regional anesthesia and pain medicine 2018 · PMID 29870457 open
[2] Perioperative Intravenous Ketamine for Acute Postoperative Pain in Adults, The Cochrane database of systematic reviews 2018 · PMID 30570761 open
[3] Intraoperative Ketamine for Prevention of Postoperative Delirium or Pain After Major Surgery in Older Adults: An International, Multicentre, Double-Blind, Randomised Clinical Trial, Lancet (London, England) 2017 · PMID 28576285 open
[4] Dose-Dependent Relationship Between Intra-Operative Ketamine Administration and Postoperative Delirium: A Retrospective Cohort Study, Anaesthesia 2025 · PMID 40619168 open
[5] Perioperative Ketamine for Postoperative Pain Management in Patients With Preoperative Opioid Intake: A Systematic Review and Meta-Analysis, Journal of clinical anesthesia 2022 · PMID 35065394 open
[6] Intraoperative Ketamine Reduces Immediate Postoperative Opioid Consumption After Spinal Fusion Surgery in Chronic Pain Patients With Opioid Dependency: A Randomized, Blinded Trial, Pain 2017 · PMID 28067693 open