VetMedDogs after major surgery: does a ketamine constant-rate infusion added to opioid therapy improve pain scores versus opioid therapy alone? — POSSIBLE
In dogs after major surgery, does a ketamine constant-rate infusion vs opioid therapy alone improve pain scores?
Shelf #525 · gate-verified and displayed under the developer's blinded-trial rule
POSSIBLE: Adding a low-dose ketamine constant-rate infusion (CRI) to opioid therapy lowered pain scores after forelimb amputation — a major surgery — in a prospective, randomised, blinded clinical study of 27 dogs (Wagner 2002, PMID: 12420827): every dog received a fentanyl infusion (1 to 5 µg/kg/h) for the first 18 hours after surgery, and the ketamine group (0.5 mg/kg bolus before surgery, 10 µg/kg/min during surgery, then 2 µg/kg/min for 18 hours after surgery) had significantly lower pain scores at 12 and 18 hours after surgery and was significantly more active on postoperative day 3 than the saline-infusion group. A second randomised trial, after mastectomy in bitches (Sarrau 2007, PMID: 17725589), found no significant difference in additional opioid requirements between placebo, low-dose ketamine CRI (2 µg/kg/min for 6 hours) and high-dose ketamine CRI (10 µg/kg/min for 6 hours) groups — for that outcome the treatment made no difference — although high-dose ketamine improved feeding behaviour at 20 hours (per cent coverage of basal energy requirements differed versus low-dose, P = 0.014, and versus placebo, P = 0.038). Design class (a): the pivotal record (Wagner 2002) is randomised and blinded by its own wording (MeSH: Double-Blind Method) and answers the shelf's own comparison — ketamine CRI added to an opioid infusion versus the same opioid infusion alone — after a major operation. The stamp is POSSIBLE, not higher, because the two trials point in different directions on their pain-related endpoints (lower pain scores in Wagner; no opioid-sparing in Sarrau), both are small, neither abstract reports the actual pain-score values, and each tests a different operation, dose and infusion duration, so there is no single replicated protocol. Evidence for operations other than amputation and mastectomy, and for infusions longer than 18 hours, was not found. Drafted Nov 10, 2026 (VetMed build, topic #525); all figures from the abstract fetched and verified at drafting.
Wagner 2002: ketamine CRI added to a fentanyl infusion gave significantly lower pain scores at 12 and 18 hours after forelimb amputation, and dogs were more active on day 3, in a randomised blinded study of 27 dogs
Prospective, randomized, blinded clinical study (record's own wording; MeSH includes Double-Blind Method; publication types: Clinical Trial, Journal Article, Randomized Controlled Trial)
Who: Dogs: 27 dogs undergoing forelimb amputation (major surgery), in a prospective, randomized, blinded clinical study at a referral setting. All dogs were anesthetized with glycopyrrolate, morphine, propofol and isoflurane, and all received a fentanyl infusion (1 to 5 µg/kg/h) for the first 18 hours after surgery. Thirteen dogs received ketamine IV (0.5 mg/kg bolus before surgery, 10 µg/kg/min during surgery, and 2 µg/kg/min for 18 hours after surgery); 14 dogs received the same volume of saline (0.9% NaCl) solution on the same schedule. Pain was evaluated before surgery, at extubation, and 1, 2, 3, 4, 12 and 18 hours after extubation; owners evaluated appetite, activity and wound soreness on postoperative days 2, 3 and 4.
Result: Dogs that received ketamine infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day 3 than dogs that received saline solution infusions. No significant differences at the earlier postoperative time points are reported in the abstract, and the abstract does not report the pain-score values themselves. The authors conclude that perioperative administration of low doses of ketamine to dogs may augment analgesia and comfort in the postoperative surgical period.
Watch out: The comparator is opioid therapy alone only in the specific sense that both groups received the same fentanyl infusion plus either ketamine or saline — the trial does not compare ketamine against a dog receiving no opioid. Small (13 versus 14 dogs), one operation type (forelimb amputation), one dosing regimen, and the benefit appears only at 12 and 18 hours and on day-3 activity — not at the 1–4 hour assessments — and the abstract gives significance statements without the underlying pain-score values, so the size of the pain reduction cannot be judged from the record.
Wagner AE, Walton JA, Hellyer PW, Gaynor JS, Mama KR. Use of low doses of ketamine administered by constant rate infusion as an adjunct for postoperative analgesia in dogs. J Am Vet Med Assoc. 2002;221(1):72-5. PMID: 12420827. Registry ID: none in the record. MeSH: Amputation, Surgical/veterinary · Analgesia/methods, veterinary* · Analgesics/administration & dosage* · Animals · Dogs/physiology*, surgery · Double-Blind Method · Forelimb/surgery* · Infusions, Intravenous/veterinary · Ketamine/administration & dosage* · Pain Measurement/veterinary · Postoperative Pain/drug therapy, veterinary* · Prospective Studies · Time Factors
Sarrau 2007: after mastectomy, ketamine CRI made no difference to additional opioid requirements versus placebo (the treatment made no difference) at either dose, though high-dose ketamine improved feeding at 20 hours
Randomised three-group trial (record's own wording: 'The bitches were randomised into three groups'; publication type: Randomized Controlled Trial) — the record does not state blinding
Who: Bitches (female dogs) undergoing mastectomy (major surgery), randomised into three groups in a clinical setting: a placebo group (0.09 ml/kg isotonic saline IV followed by a 6-hour CRI of 0.5 ml/kg/hour), a low-dose ketamine group (150 µg/kg ketamine IV followed by a 6-hour CRI of 2 µg/kg/minute) and a high-dose ketamine group (700 µg/kg ketamine IV followed by a 6-hour CRI of 10 µg/kg/minute). Ketamine or placebo was administered at the end of the mastectomy. Any additional opioids given were recorded at extubation and at intervals after extubation; food intake was evaluated 8 (T8) and 20 (T20) hours after extubation as per cent coverage of basal energy requirements (BER). The abstract does not state the total number of bitches or the per-group sizes.
Result: No significant difference was observed for opioid requirements between the three groups (the treatment made no difference to opioid requirements). The mean percentages of BER coverage did not differ significantly at T8, but at T20 the difference between the high-dose and low-dose ketamine groups (P = 0.014) and between the high-dose ketamine and placebo groups (P = 0.038) was significant. The authors conclude that 700 µg/kg ketamine IV postoperatively followed by a 6-hour ketamine CRI of 10 µg/kg/minute improved patient feeding behaviour.
Watch out: This trial's pain-related endpoint is additional opioid requirement, not a pain score, and on that endpoint ketamine was null at both doses — it should not be quoted as showing ketamine improves pain control after mastectomy. The positive finding is a feeding-behaviour outcome (BER coverage at 20 hours) in the high-dose group only, ketamine was given for only 6 hours starting at the end of surgery (unlike Wagner's perioperative 18-hour postoperative infusion), and group sizes are not stated in the abstract, so the trial's precision cannot be judged from the record.
Sarrau S, Jourdan J, Dupuis-Soyris F, Verwaerde P. Effects of postoperative ketamine infusion on pain control and feeding behaviour in bitches undergoing mastectomy. J Small Anim Pract. 2007;48(12):670-6. PMID: 17725589. Registry ID: none in the record. MeSH: Anesthetics, Dissociative/administration & dosage, therapeutic use* · Animals · Dog Diseases/pathology, surgery* · Dogs · Feeding Behavior* · Female · Infusions, Intravenous/veterinary · Ketamine/administration & dosage, therapeutic use* · Mammary Neoplasms, Animal/pathology, surgery · Mastectomy/veterinary* · Pain Measurement/veterinary · Postoperative Pain/prevention & control, veterinary* · Treatment Outcome
Synthesis: ketamine CRI lowered pain scores after amputation on top of fentanyl, but did not reduce opioid requirements after mastectomy — POSSIBLE
Synthesis
Who: Synthesis of the cards above: Wagner 2002 (27 dogs, forelimb amputation, ketamine CRI versus saline CRI, both on a fentanyl infusion, randomised and blinded) and Sarrau 2007 (bitches, mastectomy, low- or high-dose ketamine CRI for 6 hours versus placebo, randomised, blinding not stated).
Result: (1) Pain scores: significantly lower at 12 and 18 hours after amputation with ketamine CRI added to fentanyl, with greater activity on postoperative day 3 (Wagner). (2) Opioid requirement: no significant difference between placebo, low-dose and high-dose ketamine CRI after mastectomy — the treatment made no difference on this endpoint (Sarrau). (3) Feeding: high-dose ketamine improved BER coverage at 20 hours after mastectomy versus low-dose (P = 0.014) and placebo (P = 0.038), with no difference at 8 hours (Sarrau). (4) Unanswered: pain-score effects after major operations other than amputation and mastectomy, and any protocol longer than 18 hours, were not found in the carded records.
Watch out: One-home check at drafting: neither carded PMID appears in any other pack on disk. Records deliberately not carded as claim-carriers: Gutierrez-Blanco 2014 (PMID: 25039918), a randomised blinded CRI comparison after ovariohysterectomy — an elective, less major operation, in which the ketamine arm was not separated from control on pain scores in the abstract (rescue analgesia in 3 ketamine dogs versus 8 control/butorphanol dogs) — and Lewis 2014 (PMID: 24739113), in which ketamine was only one component of a morphine-lidocaine-ketamine CRI compared with epidural and other protocols after stifle surgery, so no ketamine-specific effect can be read from it (that record already homes on Shelf #523 and is not re-carded here). Neither record would change the amputation/mastectomy picture above.
Synthesis of Wagner AE et al. PMID: 12420827; Sarrau S et al. PMID: 17725589. Registry IDs as on the individual cards.
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