For horses undergoing general anaesthesia, are rope recoveries or free recoveries better?

a Knowledge Summary by

Ffion Lloyd BVSc MRCVS ^1*

Pamela Murison BVMS PhD DipECVAA DVA PGCert(HE) FHEA MRCVS ^1*

¹University of Glasgow Small Animal Hospital, 464 Bearsden Rd, Bearsden, Glasgow G61 1BD
^*Corresponding Author (f.lloyd.1@research.gla.ac.uk)

The evidence

Only three studies were found that address the PICO question directly by comparing rope-assisted and unassisted recoveries in horses, thereby comprising a limited evidence base for this clinical question. Of these studies, one is a single-centre randomised controlled trial (Arndt et al., 2020) involving 301 horses, representing the highest level in the hierarchy of evidence; the others are single-centre retrospective analyses of case records from 200 horses (Rüegg et al., 2016) and 1252 horses (Nicolaisen et al., 2020) (hereafter referred to as the ‘three identified studies’). The difference in population size in Nicolaisen et al. (2020) and Rüegg et al. (2016) (1252 horses versus 200 horses respectively) lends Nicolaisen et al. (2020) a higher evidential status, and so it could be argued that its results are more valid. Thus the ‘weighting’ of the studies in terms of consideration of results would therefore be first, second and third for Arndt et al. (2020), Nicolaisen et al. (2020) and Rüegg et al. (2016).

Auer & Huber’s 2012 study presented as an abstract at a conference directly addresses the PICO question in addition to the three identified studies. It compares rope-assisted recoveries with unassisted recoveries in a cohort containing both elective and emergency cases. A lack of any demonstrable benefit of rope assistance for any sub-group of horses was reported, and the unassisted group recovered significantly faster. However, only brief details are described and therefore the study cannot be critically appraised.

Each of the three identified studies were conducted at different institutions. The nature of the populations in each study vary considerably; the Arndt et al. (2020) cohort was comprised of healthy horses, ASA grade I or II, undergoing a variety of elective surgical procedures. In contrast, Rüegg et al. (2016) examines a population of horses that presented for emergency colic surgery that may be in a critical clinical condition; Nicolaisen et al. (2020) includes horses presenting for both elective and emergency procedures. Significant differences in peri-anaesthetic morbidity and mortality, and crucially, recovery, between the study populations can therefore be expected. The rope systems examined in each study are similar in description (head and tail ropes passed through rings attached to the wall and controlled by two people), but are not depicted, making detailed comparison difficult. Arndt et al. (2020) and Rüegg et al. (2016) excluded horses weighing under 200 kg, perhaps reflecting the opinion that lighter horses do not require this type of assistance in recovery. Nicolaisen et al. (2020) excluded horses under 1 year of age, possibly because this cohort may be smaller and/or less likely to be accustomed to handling and headcollars.

Summary of the evidence

Appraisal, application and reflection

Assisting equine anaesthetic recoveries is a common practice: approximately 35% of respondents to a recently conducted questionnaire utilise head and tail ropes for horses in their clinical practice (de Miguel Garcia et al., 2021), making the critical appraisal of this intervention worthwhile. Opposing results provided by the evidence base makes it difficult to arrive at a firm conclusion regarding the utility of rope-assistance in equine anaesthesia recoveries. The findings from Rüegg et al. (2016) fail to suggest any appreciable clinical benefit of rope-assistance: there was no difference between recovery scores or timings between the assisted and unassisted groups, and several rope-associated injuries were reported. In contrast, results from Arndt et al. (2020) and Nicolaisen et al. (2020) favour rope-assistance, demonstrating significantly improved recovery quality, shorter duration of recovery and fewer attempts to stand in the rope-assisted group of Arndt et al. (2020), and a reportedly lower risk of fatal recovery complications in the assisted group of Nicolaisen et al. (2020). Duration of recovery and attempts to stand were not included in the analysis of the latter study due to inconsistencies with reporting these outcomes in the retrospective data.

It is important to consider the results of the three identified studies within the wider context of veterinary literature pertaining to the general issue of equine peri-anaesthetic morbidity and mortality. The current largest study of this subject, the Confidential Enquiry into Perioperative Equine Fatalities (CEPEF), was published in 2002 (Johnston et al., 1995; and Johnston et al., 2002), and included results from 41,824 horses undergoing general anaesthesia from 62 international clinics. Results from this analysis revealed a 1.9% mortality rate within 7 days of anaesthesia and surgery; this decreased to 0.9% when colic cases were excluded (Johnston et al., 2002). Unfortunately, rope assistance in recovery was not evaluated in CEPEF and could be a worthwhile addition to the CEPEF study model as it begins its next round of data collection (Gozalo-Marcilla et al., 2020).

A recently published retrospective analysis of equine anaesthesia-related morbidity and mortality in one university clinic (Laurenza et al., 2020) did differentiate between assisted and unassisted recoveries in its population of 1,161 horses, but the authors ‘could not observe the effect of recovery method on the risk of complication’, citing the retrospective nature of the study as the reason for this. Of complications reported in this study, 92% occurred in recovery, highlighting the need for improvements to safety in this period (Laurenza et al., 2020).

The increased risk of perioperative mortality for horses undergoing colic surgery in comparison to elective procedures is clear. The increased rate of intraoperative complications in colic cases could be expected to negatively impact recovery, potentially increasing the risk of morbidity and mortality in this period for this cohort. Perhaps this goes some way to contextualising the lack of appreciable benefit from rope assistance witnessed in the colic group in Rüegg et al. (2016). If recovery-related injury and risk of poor recovery is generally higher in these horses, rope assistance as a sole intervention may be less likely to overcome these risks completely, and clear benefits of such an intervention may therefore be difficult to demonstrate, particularly in a small population. However, for horses undergoing elective procedures, for which the expectation of a successful recovery is much higher, an opportunity is created to prevent accidental recovery complications and associated injuries, as demonstrated by Arndt et al. (2020).

Whilst the objective outcome measures such as fatalities, time to first activity, duration of recovery and attempts to stand are easy to compare between the three identified studies, direct comparison of the numerical scores that produce the measure of ‘recovery quality’ is more challenging. Different scoring systems are used: a descriptive scale giving a score from 1 to 5 in both retrospective analyses offers a perhaps less nuanced method of scoring than the composite scoring system used in Arndt et al. (2020), which gives a possible score between 11 and 100. The difference between average scores was 10 for the assisted and unassisted groups in Arndt et al. (2020), but the significance of this difference is difficult to quantify in clinical terms and therefore whether it conferred a real benefit to the horses in the rope-assisted group is impossible to state with any certainty. Nicolaisen et al. (2020) did not assign recovery scores to the unassisted group, making comparisons in recovery quality impossible to deduce between the assisted and unassisted cohorts. It is also important to note that none of the scoring systems used have been validated for clinical use. The challenges of using subjective scoring measures to assess recoveries in horses, namely the lack of agreement between scorers, have been illustrated for both simple and composite scoring systems (Carter & Anderson, 2017), highlighting the potential weakness of these systems as a qualitative outcome measure.  

The influence of anaesthetic duration on recovery outcomes is an important consideration: longer anaesthetics increase the risks of recovery injuries and fatality (Johnston et al., 1995). Average anaesthetic duration was considerably shorter for the horses included in Arndt et al. (2020) (all undergoing elective procedures) than for horses in both retrospective analyses (all emergency or emergency and elective surgeries). Although anaesthetic duration did not differ significantly between assisted and unassisted groups within each individual study, the effect of duration may have been responsible for differences in recovery outcomes between study populations. This calls into question the purported positive contribution of rope assistance to producing safe recoveries in Arndt et al. (2020). Nicolaisen et al. (2020) also reinforces this relationship within its own data: median anaesthetic time was significantly longer for horses with fatal and non-fatal complications than for horses without complications, across both assisted and unassisted groups.

An interesting finding from Rüegg et al. (2016) links hypoxaemia (PaO₂ <60 mmHg) to an increased risk of an ‘unsafe’ recovery. By contrast, hypotension (defined as MAP <70 mmHg for ≥15 minutes) was not associated with worse recoveries. This finding highlights an important limitation of Arndt et al. (2020) and Nicolaisen et al. (2020): the incidence of hypotension and hypoxaemia are not reported. The lack of this clinical information makes it difficult to be confident that differences in recovery quality between the assisted and unassisted groups in these studies can be solely attributed to rope assistance and not a reduced incidence of anaesthetic-related problems such as hypoxaemia or hypotension. It could be presumed that due to the low ASA grade of the horses in the Arndt et al. (2020) population, complications like these are less likely to occur; but they are not impossible, even in healthy horses, due to the hazards incumbent in equine anaesthesia and recumbency. Inclusion of horses undergoing emergency surgery in Nicolaisen et al. (2020) increases the likelihood of unreported hypotension and hypoxaemia. No correlation was found between hypotension or arterial blood gas tensions and recovery quality in a separate retrospective analysis of healthy horses (Young & Taylor, 1993), but hypotension has been repeatedly linked to an increased risk of peri-anaesthetic morbidity and mortality (Laurenza et al., 2020; Young & Taylor, 1993; and Bidwell et al., 2007), although further work is required to examine its effect on recovery quality specifically. 

The inherent risks of using ropes to assist recovery are illustrated by findings from all three studies. Reported complications included detachment and twisting of ropes and, more seriously, failure of a halter ring which resulted in suspected cervical dislocation and euthanasia in one horse in Rüegg et al. (2016). Although this is a singular incident, the potential for serious problems should not be ignored when considering the use of a rope recovery system for any particular horse. Additionally, complications such as detachment and twisting of ropes would present physical risk to personnel when intervening to correct these issues. Importantly, fatalities occurred in equal numbers in both assisted and unassisted groups in Arndt et al. (2020) and Rüegg et al. (2016), illustrating the inability of rope assistance to prevent catastrophic injuries. It would seem the value of rope assistance lies in the potential improvement of quantifiable recovery variables such as shorter recovery time and fewer attempts to stand, rather than absolute prevention of fatalities. However, because of the relative infrequency of fatality in equine anaesthesia, none of the three studies have sufficient power to detect statistically significant differences in this outcome between groups. Therefore, rope assistance may decrease fatalities, even if it cannot completely prevent them. Although Nicolaisen et al. (2020) reports a statistically significant reduction in fatalities in the rope-assisted group, no power calculation was performed and it is likely that a larger population would be required to detect a true difference in fatality rates.

In a 2016 retrospective study from one university clinic that reported similar mortality rates to CEPEF for colic and non-colic populations (1.6% and 0.9% respectively), fractures were identified as the most frequent cause of recovery fatality at 71.4% (Dugdale et al., 2016). All but two of the 1,416 horses included in this study had unassisted recoveries, and the authors concluded that ‘improvements to the recovery process that can reduce fracture occurrence are still required’ ( Dugdale et al., 2016). The possibility for rope assistance to be one such improvement has been postulated in a review of equine anaesthesia-associated mortality (Dugdale & Taylor, 2016), however the risk of fracture in recovery was no different between the assisted and unassisted groups in Nicolaisen et al. (2020). A much lower incidence of fracture in recovery (0.04%) was reported by a private clinic where rope-assisted recoveries were standard protocol (Bidwell et al., 2007). However, overall mortality was also significantly lower at 0.24%, so these results are likely to reflect a general difference in hospital and team circumstances (a private clinic with a high caseload of healthy horses, mostly undergoing elective orthopaedic procedures lasting under 1 hour) rather than any one specific factor. Therefore, the contribution of rope assistance to producing these results should not be overstated. The influence of the interplay between hospital and team factors here highlights the importance of individual clinic dynamics: rope assisted recoveries may be more suitable for one hospital over another, given inherent differences in teams, equipment and caseload.

Although all of the three identified studies discuss a ‘traditional’ one or two-person head-and-tail rope recovery system, other iterations do exist in clinical practice. A two-rope system with the tail rope under constant tension by way of a belay device was described in a retrospective analysis of rope-related complications (Niimura Del Barrio et al., 2018). The system performed well for the particular clinic involved in the study: an overall complication rate of 0.51% was reported, with very few complications directly attributed by the authors to the use of ropes (Niimura Del Barrio et al., 2018). A three-rope, two-person system, with one rope attached to either side of a headcollar and one rope attached to the tail, has been studied retrospectively and appeared to provide a ‘safe recovery without any catastrophic injury’ (da Silva et al., 2018). Neither of these studies, however, included a control group, and so meaningful conclusions about their utility over and above unassisted recoveries cannot be drawn.

Equine anaesthesia carries inherent risks, especially during the recovery period (Laurenza et al., 2020), and the mortality rate is much higher than that reported for small animals (Johnston et al., 2002). Ultimately, the decision to perform a rope-assisted recovery must be made considering individual patient, team and clinic factors. Taking the three identified studies and their respective weightings appointed by the hierarchy of evidence into consideration, rope assistance does appear likely to confer a benefit in the recovery of horses (sick and healthy) from general anaesthesia. However, it must be recognised that injuries can result from the use of a rope recovery system and rope assistance does not prevent catastrophic injury (including fracture) in either healthy or sick horses. Additionally, the effect of peri-operative hypotension and hypoxaemia, as well as the duration of anaesthesia, are likely to affect recovery outcome significantly, regardless of whether or not rope assistance is employed. The suitability of a rope recovery system for excitable or unhandled horses has been questioned (Niimura Del Barrio et al., 2018); the behaviour and temperament of an individual horse must be taken into account when considering an assisted recovery – but these variables are inevitably difficult to predict accurately following general anaesthesia. A ‘blanket’ policy of rope recovery is not recommended due to the inherent variability in the temperament of horses and capabilities and experience of personnel.

Methodology Section

Search Strategy
Databases searched and dates covered:	CAB Abstracts on OVID Platform: 1973–2021 Week 14 PubMed accessed via NCBI: 1920–April 2021
Search strategy:	CAB Abstracts: horse* or ponies or pony or equid* or equine or gelding* or mare* or stallion* or exp horses/ or exp mares/ or exp stallions/ anaesthe* or anesthe* or exp anaesthesia/ or exp anaesthetics rope* or roping or assist* or support* or hoist or 'head-and-tail' unassisted or unsupported or 'free recovery' Search 1: 1 and 2 and 3 and 4 Search 2: 1 and 2 and (3 or 4)   PubMed: horse or ponies or pony or equid or equine or gelding* or mare* or stallion anaesthesia or anesthesia or anaesthetic or anesthetic rope or roped or roping or assist or support or hoist or 'head-and-tail' unassisted or unsupported or 'free recovery' Search: 1 and 2 and 3 and 4
Dates searches performed:	14 Apr 2021

Exclusion / Inclusion Criteria
Exclusion:	Not available in English. Not relevant to PICO question. Non-peer-reviewed journal. Case reports/case series. Expert opinions. Book chapters/sections.
Inclusion:	Peer-reviewed material including retrospective and prospective clinical trials and systematic reviews comparing rope assistance during recovery and ‘free’/unassisted recovery from general anaesthesia in horses.

Search Outcome
Database	Number of results	Excluded – Irrelevant	Excluded – Not peer-reviewed	Excluded – Case report/series	Excluded – Opinion	Excluded – Book	Excluded – Not English	Total relevant papers
CAB Abstracts: Search 1	6	3	1	0	1	0	0	1
CAB Abstracts: Search 2	356	272	0	54	12	14	1	3
PubMed	13	12	0	0	0	0	0	1
Total relevant papers when duplicates removed						3

The authors declare no conflicts of interest.

1. Arndt, S., Hopster, K., Sill, V., Rohn, K. & Kästner, S.B.R. (2019). Comparison between head-tail-rope assisted and unassisted recoveries in healthy horses undergoing general anesthesia for elective surgeries. Veterinary Surgery. 49(2), 329–338. DOI: https://doi.org/10.1111/vsu.13347
2. Auer, U & Huber, C. (2013). A comparision of head/tail rope-assisted versus unassisted recoveries of horses after patrial intravenous general anaesthesia. Abstracts presented at the Association of Veterinary Anaesthetists Spring meeting, 22^nd–23^rd March 2012, Davos, Switzerland. (2013). Veterinary Anaesthesia Analgesia. 40(1), 1–28. DOI: https://doi.org/10.1111/vaa.12001
3. Bidwell, L.A., Bramlage, L.R. & Rood, W.A. (2007). Equine perioperative fatalities associated with general anaesthesia at a private practice - a retrospective case series. Veterinary Anaesthesia and Analgesia. 34(1), 23–30. DOI: https://doi.org/10.1111/j.1467-2995.2005.00283.x
4. Carter, E. & Anderson, F. (2017). Assessment of agreement among diplomates of the American College of Veterinary Anesthesia for scoring the recovery of horses from anesthesia by use of subjective grading scales and development of a system for evaluation of the recovery of horses from anesthesia by use of accelerometry. American Journal of Veterinary Research. 78(6), 668–676. DOI: https://doi.org/10.2460/ajvr.78.6.668
5. da Silva, D.R.P., Silva, G.B., de la Côrte, F.D., Brass, K.E., Pozzobon, R., Dau, S.L., de Gasperi, D, & Freitas, G.C. (2018). Anesthetic recovery assisted by rope at three points in horses. Ciéncia Rural. 48(11), 1–6. DOI: http://dx.doi.org/10.1590/0103-8478cr20180154
6. de Miguel Garcia, C., Campoy, L., Parry, S., Miller, J.E., Martin-Flores, M. & Gleed, R.D. (2021). Questionnaire on the process of recovering horses from general anesthesia and associated personnel injury in equine practice. Veterinary Anaesthesia and Analgesia. 48(2), 223–229. DOI: https://doi.org/10.1016/j.vaa.2020.12.005
7. Dugdale, A.H., Obhrai, J. & Cripps, P.J. (2016). Twenty years later: a single-centre, repeat retrospective analysis of equine perioperative mortality and investigation of recovery quality. Veterinary Anaesthesia and Analgesia. 43(2), 171–178. DOI: https://doi.org/10.1111/vaa.12285
8. Dugdale, A.H.A. & Taylor, P.M. (2016). Equine anaesthesia-associated mortality: where are we now? Veterinary Anaesthesia and Analgesia. 43(3), 242–255. DOI: http://dx.doi.org/10.1111/vaa.12372
9. Gozalo-Marcilla, M., Redondo, J.I., Johnston, M., Taylor, P. & Bettschart-Wolfensberger, R. (2020). A new equine anaesthetic mortality study two decades after CEPEF2: CEPEF4 is going live! Equine Veterinary Journal. 52(6), 891–892. DOI: http://dx.doi.org/10.1111/evj.13327
10. Johnston, G.M., Eastment, J.K., Wood, J.L.N. & Taylor, P.M. (2002). The confidential enquiry into perioperative equine fatalities (CEPEF): mortality results of Phases 1 and 2. Veterinary Anaesthesia and Analgesia.29(4), 159–170. DOI: https://doi.org/10.1046/j.1467-2995.2002.00106.x
11. Johnston, G.M., Taylor, P.M., Holmes, M.A. & Wood, J.L.N. (1995). Confidential enquiry of perioperative equine fatalities (CEPEF‐1): preliminary results. Equine Veterinary Journal. 27(3), 193–200. DOI: http://dx.doi.org/10.1111/j.2042-3306.1995.tb03062.x
12. Laurenza, C., Ansart, L. & Portier, K. (2020). Risk factors of anesthesia-related mortality and morbidity in one equine hospital: a retrospective study on 1,161 cases undergoing elective or emergency surgeries. Frontiers Veterinary Science. 6, 1–10. DOI: http://dx.doi.org/10.3389/fvets.2019.00514
13. Nicolaisen, A.S.K., Bendix Nygaard, A., Christophersen, M.T., Jensen, D.B. & Lindegaard, C. (2020). Effect of head and tail rope-assisted recovery of horses after elective and emergency surgery under general anaesthesia. Equine Veterinary Education. 1–8. DOI: https://doi.org/10.1111/eve.13397
14. Niimura Del Barrio, M.C., David, F., Hughes, J.M.L., Clifford, D., Wilderjans, H. & Bennett, R. (2018). A retrospective report (2003–2013) of the complications associated with the use of a one-man (head and tail) rope recovery system in horses following general anaesthesia. Irish Veterinary Journal. 71(1), 1–9. DOI: http://dx.doi.org/10.1186/s13620-018-0117-1
15. Rüegg, M., Bettschart-Wolfensberger, R., Hartnack, S., Junge, H.K., Theiss, F. & Ringer, S.K. (2016). Comparison of non-assisted versus head and tail rope-assisted recovery after emergency abdominal surgery in horses. Pferdeheilkunde. 32(5):469–478. DOI: http://dx.doi.org/10.21836/PEM20160508
16. Young, S.S. & Taylor, P.M. (1993). Factors influencing the outcome of equine anaesthesia: a review of 1,314 cases. Equine Veterinary Journal. 25(2), 147–151. DOI: http://dx.doi.org/10.1111/j.2042-3306.1993.tb02926.x