VetMedAnaesthetised horses: does partial intravenous anaesthesia (alpha-2/ketamine infusions) vs inhalant alone improve recovery quality? — POSSIBLE
In anaesthetised horses, does partial intravenous anaesthesia (alpha-2/ketamine infusions) vs inhalant alone improve recovery quality?
Shelf #834 · gate-verified and displayed under the developer's blinded-trial rule
POSSIBLE: Whether partial intravenous anaesthesia improves recovery quality depends on the agent infused — the blinded randomised evidence says yes for a dexmedetomidine infusion and no for a detomidine infusion, and the ketamine-based protocols were shown only not to impair recovery. In Marcilla 2012 (PMID: 22151875; prospective, randomized, blinded clinical study; 40 adult healthy horses undergoing elective surgery under isoflurane), a dexmedetomidine constant rate infusion (1.75 µg/kg/hour) vs a saline infusion produced significantly better recovery scores, with fewer attempts to stand and significantly longer times to sternal position and first attempt to stand; the abstract reports no numeric recovery scores, so the size of the improvement cannot be stated. In Schauvliege 2011 (PMID: 21988809; prospective, randomized, blinded clinical trial; 20 adult healthy horses undergoing elective surgery under isoflurane, the anaesthetist unaware of the treatment), a detomidine constant rate infusion (5 µg/kg/hour) vs saline left recovery quality and duration comparable between treatments (the treatment made no difference). In Nannarone 2012 (PMID: 22738046; 45 client-owned horses randomly allocated to isoflurane alone or to isoflurane at 1% supplemented with a guaifenesin–ketamine or romifidine–ketamine infusion), both PIVA protocols maintained surgical anaesthesia with an isoflurane-sparing effect and, in the authors' conclusion, PIVA did not impair recovery quality — an absence of demonstrated harm, with no recovery scores in the abstract and no blinding established by that record, not a demonstrated improvement. Design class (a) for this shelf's own comparison: two carded records (Marcilla 2012; Schauvliege 2011) each establish randomisation and blinding — each record's own wording is 'randomized, blinded' and each record's MeSH carries Single-Blind Method, disclosed exactly as stated — and each answers this shelf's comparison and population, an intravenous infusion added to inhalant anaesthesia vs inhalant anaesthesia with a saline infusion; because the two class-(a) records disagree by agent, the stamp is POSSIBLE and agent-specific rather than a class-wide LIKELY. In both blinded trials every horse also received an alpha-2 agonist for the recovery period itself (dexmedetomidine 0.875 µg/kg in Marcilla 2012; detomidine 2.5 µg/kg in Schauvliege 2011), a co-intervention shared by both arms. Tier C is not engaged: no mortality or survival claim is made anywhere on this shelf. This shelf is distinct from the unbuilt triple-drip question (#843), a different regimen. Drafted Nov 10, 2026 (VetMed build, topic #834); figures from the abstracts, fetched and verified at drafting.
Marcilla 2012: a dexmedetomidine CRI significantly improved recovery scores vs saline in isoflurane-anaesthetised horses (randomised, blinded; 40 horses)
Prospective, randomized, blinded, clinical study (record's own wording; publication types include Randomized Controlled Trial; MeSH carries Single-Blind Method)
Who: Horses: 40 adult healthy horses (mean weight 491 ± SD 102 kg) undergoing elective surgery. After sedation with dexmedetomidine (3.5 µg/kg intravenously) and induction with midazolam (0.06 mg/kg) and ketamine (2.2 mg/kg) intravenously, anaesthesia was maintained with isoflurane in oxygen/air; horses were ventilated, and dobutamine was administered for hypotension as described in the record. During anaesthesia, horses were randomly allocated to receive a constant rate infusion of dexmedetomidine (1.75 µg/kg/hour; group D) or saline (group S). All horses received dexmedetomidine 0.875 µg/kg intravenously for the recovery period. Recovery scores, duration of recovery and attempts to stand were compared between groups.
Result: Recovery scores were significantly better in group D than in group S, with fewer attempts to stand and significantly longer times to sternal position and first attempt to stand in group D. Heart rate and arterial partial pressure of oxygen were significantly lower in group D compared with group S, and an interaction between treatment and time was present for cardiac index, oxygen delivery index and systemic vascular resistance. The authors concluded that a dexmedetomidine constant rate infusion produced limited cardiopulmonary effects, but significantly improved recovery quality. The abstract reports no numeric recovery scores, recovery times or attempt counts, so the size of the improvement cannot be quoted from the fetched record.
Watch out: Blinding is disclosed exactly as the record states it: the study is described as blinded and its MeSH carries Single-Blind Method; the record does not specify every masked party, and no fuller masking claim is made here. Every horse received dexmedetomidine sedation before induction and a dexmedetomidine bolus for the recovery period, in both arms — so the comparison is an intra-operative dexmedetomidine infusion vs saline on a shared dexmedetomidine background, not dexmedetomidine-naive vs dexmedetomidine anaesthesia. Healthy horses undergoing elective surgery; emergency and colic caseloads are not represented. With no numeric recovery scores in the abstract, this card carries the direction and significance the authors report, not an effect size.
Marcilla MG, Schauvliege S, Segaert S, Duchateau L, Gasthuys F. Influence of a constant rate infusion of dexmedetomidine on cardiopulmonary function and recovery quality in isoflurane anaesthetized horses. Vet Anaesth Analg. 2012;39(1):49-58. PMID: 22151875. Registry ID: none in the record. MeSH: Anesthesia Recovery Period · Anesthesia, Inhalation/methods, veterinary* · Anesthetics, Inhalation* · Animals · Blood Gas Analysis/veterinary · Blood Pressure/drug effects · Dexmedetomidine/administration & dosage*, pharmacology · Dobutamine · Heart/drug effects* · Heart Rate/drug effects · Horses · Hypnotics and Sedatives/administration & dosage*, pharmacology · Infusions, Intravenous/veterinary · Isoflurane* · Ketamine · Respiration/drug effects* · Single-Blind Method
Schauvliege 2011: a detomidine CRI left recovery quality and duration comparable to saline in isoflurane-anaesthetised horses — no improvement (randomised, blinded; 20 horses)
Prospective, randomized, blinded, clinical trial (record's own wording; publication types include Randomized Controlled Trial; MeSH carries Single-Blind Method)
Who: Horses: 20 adult healthy horses undergoing elective surgery. After sedation with detomidine (10 µg/kg intravenously) and induction of anaesthesia with midazolam (0.06 mg/kg) and ketamine (2.2 mg/kg) intravenously, anaesthesia was maintained with isoflurane in oxygen/air (inspiratory oxygen fraction 55%), with mechanical ventilation when indicated and dobutamine when mean arterial pressure fell below 70 mmHg. Horses were randomly allocated to a detomidine constant rate infusion (5 µg/kg/hour; group D) or a saline constant rate infusion (group S) throughout anaesthesia, with the anaesthetist unaware of the treatment. For recovery from anaesthesia, all horses received detomidine 2.5 µg/kg intravenously. Recovery quality and duration were recorded in each horse.
Result: Recovery quality and duration were comparable between treatments (the treatment made no difference). Heart rate (P = 0.0176) and oxygen delivery index (P = 0.0084) were lower, and systemic vascular resistance was higher (P = 0.0126), in group D compared with group S. Significant differences in isoflurane requirements were not detected. The authors concluded that a detomidine constant rate infusion produced cardiovascular effects typical for alpha-2 agonists, without affecting isoflurane requirements, recovery duration or recovery quality. The abstract reports no numeric recovery scores.
Watch out: A null result in 20 horses does not prove a detomidine infusion can never affect recovery — but it is a blinded randomised null on this shelf's own comparison, and it blocks any class-wide claim that alpha-2 agonist infusions improve recovery. As in the dexmedetomidine trial, both arms shared an alpha-2 background: detomidine sedation at induction and a detomidine bolus for recovery in every horse. Detomidine and dexmedetomidine are different agents at different infusion rates; the two blinded trials must not be pooled into a single 'alpha-2 infusions work' claim.
Schauvliege S, Marcilla MG, Verryken K, Duchateau L, Devisscher L, Gasthuys F. Effects of a constant rate infusion of detomidine on cardiovascular function, isoflurane requirements and recovery quality in horses. Vet Anaesth Analg. 2011;38(6):544-54. PMID: 21988809. Registry ID: none in the record. MeSH: Anesthesia Recovery Period · Anesthesia, Inhalation/veterinary* · Anesthetics, Inhalation/administration & dosage* · Animals · Elective Surgical Procedures/veterinary · Female · Hemodynamics/drug effects* · Horses/surgery* · Hypnotics and Sedatives/administration & dosage, pharmacology* · Imidazoles/administration & dosage, pharmacology* · Infusions, Intravenous/veterinary · Isoflurane/administration & dosage* · Male · Prospective Studies · Single-Blind Method
Nannarone 2012: guaifenesin–ketamine and romifidine–ketamine PIVA maintained anaesthesia and did not impair recovery quality vs isoflurane alone (randomised; 45 horses; no recovery scores in the abstract)
Randomised controlled trial (publication types: Comparative Study, Randomized Controlled Trial). The record establishes random allocation; it does not state blinding of recovery assessment, and none is claimed here — design class (b) for this record
Who: Horses: 45 client-owned horses requiring general anaesthesia for a variety of procedures of at least 1 hour's duration, randomly allocated to 3 groups of 15 that differed for the maintenance protocol: isoflurane with a starting end-tidal isoflurane concentration of 1.3% (isoflurane group), or isoflurane at a concentration of 1% supplemented with an adjustable continuous infusion of guaifenesin–ketamine (IGK group) or romifidine–ketamine (IRK group). A predefined scoring system was used to assess anaesthetic depth and to adjust anaesthetic delivery; the need for rescue anaesthetics and recovery quality were compared.
Result: A mean ± SD end-tidal isoflurane concentration of 1.36 ± 0.16% was necessary to maintain a surgical plane of anaesthesia in the isoflurane group; mean infusion rates of 5.0 ± 1.3 µL/kg/min (IRK) and 5.1 ± 0.8 µL/kg/min (IGK) were necessary to maintain a surgical plane of anaesthesia in the PIVA groups. A lower need for ketamine as a rescue anaesthetic was observed in the IGK group compared with the isoflurane group, and higher blood pressure and lower heart rates were found at selected time points for the IRK group compared with the IGK and isoflurane groups. The authors concluded that both PIVA protocols were satisfactory to maintain smooth and stable surgical anaesthesia, that the study supports previous findings in which PIVA has isoflurane-sparing effects, and that PIVA did not impair recovery quality. The abstract reports no recovery scores for any group, so neither improvement nor exact equivalence can be quantified from the fetched record.
Watch out: This record carries the ketamine-infusion half of the shelf's question: its PIVA arms are ketamine-based, one with guaifenesin and one with the alpha-2 agonist romifidine, tested in client-owned horses having real procedures — a broader population than the healthy elective-surgery horses of the two blinded trials. 'Did not impair recovery quality' is the authors' conclusion, published without recovery scores in the abstract; it is not evidence of improvement, and whether recovery scoring was blinded is simply not stated in the record.
Nannarone S, Spadavecchia C. Evaluation of the clinical efficacy of two partial intravenous anesthetic protocols, compared with isoflurane alone, to maintain general anesthesia in horses. Am J Vet Res. 2012;73(7):959-67. PMID: 22738046. Registry ID: none in the record. MeSH: Anesthesia, General/methods, veterinary* · Animals · Blood Gas Analysis/veterinary · Blood Pressure/drug effects · Electrocardiography/veterinary · Female · Guaifenesin/administration & dosage* · Heart Rate/drug effects · Horses/blood, physiology*, surgery · Imidazoles/administration & dosage* · Infusions, Intravenous/veterinary · Isoflurane/administration & dosage* · Ketamine/administration & dosage* · Male
Synthesis: dexmedetomidine CRI improved recovery in a blinded trial, detomidine CRI did not, and ketamine-based PIVA was shown only not to impair it — POSSIBLE, agent-specific
Synthesis
Who: Synthesis of the three carded records above (Marcilla 2012, randomised blinded dexmedetomidine-CRI trial, 40 horses; Schauvliege 2011, randomised blinded detomidine-CRI trial, 20 horses; Nannarone 2012, randomised ketamine-based PIVA trial, 45 horses) and of the near-miss records documented in the result, fetched at drafting and deliberately not carded as claim-carriers.
Result: (1) Agent-specific pattern across the carded records: a dexmedetomidine constant rate infusion improved recovery scores in a randomised blinded trial (Marcilla 2012, PMID: 22151875); a detomidine constant rate infusion did not improve recovery quality or duration in a randomised blinded trial (Schauvliege 2011, PMID: 21988809) (the treatment made no difference); ketamine-based PIVA (guaifenesin–ketamine or romifidine–ketamine) did not impair recovery quality in a randomised trial whose record does not establish blinding and reports no recovery scores (Nannarone 2012, PMID: 22738046). (2) Near-miss, not carded: Risberg 2016 (PMID: 26488527), a sequential, blinded, randomised, balanced crossover study in 8 horses, compared cardiovascular status at equivalent depths of anaesthesia with and without a dexmedetomidine constant rate infusion (cardiac index 48 ± 10 with dexmedetomidine vs 61 ± 12 mL/kg/minute without, P = 0.047) — a cardiopulmonary endpoint, not a recovery-quality comparison, so it neither adds to nor subtracts from the recovery claim, though it cautions that the dexmedetomidine protocol was the more cardiovascularly compromised at equivalent depth. (3) Near-miss, not carded: Menzies 2016 (PMID: 26915545), a randomised blinded trial of medetomidine vs S-ketamine infusions, both under isoflurane in 50 horses, found recoveries shorter and of poorer quality with S-ketamine and recovery quality significantly better with medetomidine — a PIVA-vs-PIVA comparison with no inhalant-alone arm, so it cannot carry this shelf's comparison. (4) A further medetomidine constant-rate-infusion study in sevoflurane-anaesthetised Thoroughbred racehorses undergoing arthroscopic surgery (Tokushige et al., Journal of Equine Veterinary Science, 2015) has no PubMed record and is therefore noted qualitatively here only, not carded and given no figures. (5) Design class (a) for the shelf: two carded records establish randomisation and blinding (each disclosed as 'randomized, blinded' in its record, with MeSH Single-Blind Method) for this shelf's own comparison and population; they disagree by agent, so the claim is POSSIBLE and agent-specific, not a class-wide benefit.
Watch out: One-home check at drafting: none of PMIDs 22151875, 21988809, 22738046, 26488527 or 26915545 appears in any other pack on disk, and no prior shelf homes this question. Do not quote a class-wide 'PIVA improves recovery' claim from this shelf: the two blinded trials point in opposite directions for two different alpha-2 agonists, none of the three carded abstracts reports numeric recovery scores, and in both blinded trials every horse also received an alpha-2 agonist bolus for the recovery period itself, which is shared by both arms and may itself shape recovery quality.
Synthesis of Marcilla MG et al. PMID: 22151875; Schauvliege S et al. PMID: 21988809; Nannarone S, Spadavecchia C. PMID: 22738046; Risberg ÅI et al. PMID: 26488527; Menzies MP et al. PMID: 26915545. Registry IDs as on the individual cards (none in the records).
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