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Vessel sealing versus suture ligation for canine ovarian pedicle haemostasis: a randomised clinical trial
  1. I. Schwarzkopf, DVM PhD1,
  2. B. Van Goethem, DVM, DipECVS2,
  3. P. M. Vandekerckhove, DVM, DipECVS1 and
  4. H. de Rooster, DVM PhD, DipECVS2
  1. 1DAC Malpertuus, Leenstraat 2a, Heusden, OVL 9070, Belgium
  2. 2Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Science, University of Ghent, Salisburylaan 133, Merelbeke 9820, Belgium
  1. E-mail for correspondence: ilona.schwarzkopf{at}gmail.com

Abstract

Vessel sealing (VS) is well established in laparoscopic ovariectomy (OVE) in dogs. The objectives of this study were to evaluate the efficacy of ovarian pedicle haemostasis by VS using a commercially available VS tool in open OVE and compare it with suture ligation (SL). A prospective, randomised clinical trial including 20 female dogs was designed. Open OVE was performed via a standard mid-line celiotomy by a single surgeon using a standardised protocol. At random, the right ovarian pedicle was sealed (VS) or ligated (SL) whereas the left pedicle was treated by the alternative technique. Surgical times for procedural stages and intra-operative complications were recorded and statistically evaluated. Total surgical time was 29.28±11.13 minutes (range 12.50–62.13 minutes) and time from identification to removal of the ovary was significantly less when sealing (VS 2.22±0.58 minutes) than when ligating (SL 4.10±1.13 minutes P=0.0001). Intra-operative complications were rare for both techniques (failure of the electrode of the VS device (n=3); ovarian pedicle haemorrhage due to ligature slippage (n=1)). The results of the current study indicate that ovarian pedicle haemostasis achieved by VS is significantly faster than by placement of ligatures without appearing to compromise safety.

  • Abdominal
  • Dogs
  • Reproduction
  • Soft tissue surgery
  • Accepted October 2, 2014.

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Vessel sealing (VS) is well established in laparoscopic ovariectomy (OVE) in dogs. The objectives of this study were to evaluate the efficacy of ovarian pedicle haemostasis by VS using a commercially available VS tool in open OVE and compare it with suture ligation (SL). A prospective, randomised clinical trial including 20 female dogs was designed.

Open OVE was performed via a standard mid-line celiotomy by a single surgeon using a standardised protocol. At random, the right ovarian pedicle was sealed (VS) or ligated (SL) whereas the left pedicle was treated by the alternative technique. Surgical times for procedural stages and intra-operative complications were recorded and statistically evaluated. Total surgical time was 29.28±11.13 minutes (range 12.50–62.13 minutes), and time from identification to removal of the ovary was significantly less when sealing (VS 2.22±0.58 minutes) than when ligating (SL 4.10±1.13 minutes P=0.0001). Intra-operative complications were rare for both techniques (failure of the electrode of the VS device (VSD) (n=3); ovarian pedicle haemorrhage due to ligature slippage (n=1)).

The results of the current study indicate that ovarian pedicle haemostasis achieved by VS is significantly faster than by placement of ligatures without appearing to compromise safety.

Gonadectomy of healthy female dogs is a routine and frequently performed procedure in small animal veterinary practice (Howe 2006, Adin 2011). Neutering is the most reliable method of pet population control and also has advantages for the dog's health (Root Kustritz 2012). Although other approaches have been described (Howe 2006), the most widely performed technique is mid-line celiotomy for either OVE or ovariohysterectomy (OVH) (Van Goethem and others 2006). In European countries, other than the UK, OVE is preferred to OVH for elective cases, and the uterus is only removed if uterine pathology is present (Okkens and Kooistra 1997, Howe 2006, De Tora and Mc Carthy 2011, Peeters and Kirpensteijn 2011).

Throughout the years, adaptations to the standard OVE technique have been proposed, offering benefits to the surgeon (faster procedure) or to the animal (decreased morbidity). Limiting the length of the celiotomy incision will decrease visualisation and can thus result in longer rather than shorter surgical times (Pukacz and others 2009). Laparoscopic OVE combines a small incision with good visualisation, and although surgical times decrease rapidly once experience is gained, total procedural time will be longer compared with open OVE in the hands of novice laparoscopic surgeons (Mayhew and Brown 2007).

In laparoscopic OVE, different techniques for ovarian pedicle haemostasis have been evaluated and compared: extra-corporeal or intra-corporeal SL, vascular clips, monopolar and bipolar electrocoagulation, laser energy and VSDs (Harold and others 2003, van Nimwegen and others 2005, Mayhew and Brown 2007, van Nimwegen 2007, Öhlund and others 2011).

VSDs use high-current and low-voltage bipolar radiofrequency energy to desiccate collagen and elastin in the vessel wall and surrounding connective tissue interposed between the jaws of the device (Heniford and others 2001, Carbonell and others 2003). This results in the safe sealing of vessels up to and including 7 mm in diameter during a two to four seconds seal cycle (Landman and others 2003, Person and others 2008).

Laparoscopic VSDs consist of a 20–45 cm hand instrument with integrated cutting mechanism, while devices used in open surgery have shorter hand pieces, often without a divider. Since VSDs provide excellent ovarian pedicle haemostasis in addition to a fast surgical time during laparoscopic-assisted OVH in dogs (Mayhew and Brown 2007), the authors hypothesised that open OVE in dogs using a VSD would result in shorter procedural times compared with SL, without increasing the risk of surgical complications.

The aim of the current study was to compare ovarian pedicle haemostasis during open OVE in dogs performed with VS (LigaSure) and with the conventional SL technique in terms of safety and surgical time. Furthermore, the time needed for ovarian pedicle haemostasis of the right versus the left side was studied for both techniques (VS and SL).

Materials and methods

The study protocol was approved by the local Ethical Committee (Faculty of Veterinary Medicine, Ghent University, Belgium); legal and ethical requirements have been met with regard to the humane treatment of animals described in the study.

Groups

Healthy female dogs presented for elective OVE were admitted in the study. Dogs that presented with abnormal anatomy of the uterus or ovaries during celiotomy were subsequently excluded. A total of 20 bitches were included. The dogs were randomly divided into two treatment groups by following a random list for 20 items created by a random number generator. One group had VS performed on the right ovary first followed by SL on the left ovary; the other group had SL performed on the right ovary first followed by VS on the left ovary. In this way, each dog also served as its own control.

A questionnaire was completed before surgery to obtain information on age, general health, number of oestrous cycles, date of last oestrous and occurrence of pseudopregnancy. A body condition scoring system ranging from body condition score (BCS) 1 (thin) to BCS 5 (obese) (Baldwin and others 2010) was used by one observer (IS) to objectively differentiate normal from overweight dogs (BCS 4 and BCS 5).

Anaesthetic technique

The dogs were classified as ASA (American Society of Anaesthesiologists) class I (a patient with no systemic disease) patients (http://www.asahq.org (2014)). They were premedicated with medetomidine (0.01 mg/kg, Dorbene vet, Pfizer) and methadone (0.1 mg/kg, Mephenon, Oterop), both intramuscularly. Induction was performed with diazepam (0.5 mg/kg, Valium, Roche) intravenously, immediately followed by ketamine (5 mg/kg, Anesketin, euroVet) intravenously. Cefazoline (22 mg/kg, Cefazolin Sandoz, Sandoz) was administered intravenously at the time of induction as was carprofen (4 mg/kg, Rimadyl, Pfizer) or meloxicam (0.2 mg/kg, Metacam, Boehringer Ingelheim).

Lactated Ringer's solution (Hartmann's Lactated Ringers, B. Braun) was infused at 10 ml/kg/hour intravenously during the surgery.

The dogs were intubated and after clipping, prepping and transfer to the surgical theatre, they were positioned in dorsal recumbency on a heating pad. Anaesthesia was maintained by isoflorane and oxygen. Buprenorphine (20 μg/kg, Vetergesic Multidose, Ecuphar nv) was administered intravenously at the end of the surgery. An adhesive bandage (Hypafix, BSN Medical) was used for wound coverage and the dogs were placed in a recovery cage with soft padding until full recovery.

Surgical technique

All surgeries were performed by the same surgeon (IS), assisted by one of two experienced technicians. A standard mid-line celiotomy approach was used. The celiotomy incision was made just cranial to the umbilicus until halfway the distance between umbilicus and pubis. The procedure started with identification of the right ovary. A haemostat was placed on the proper ligament and held under mild caudomedial traction by the technician. The suspensory ligament was left intact since all ovaries could be retracted from the abdomen. With a closed haemostat, a window was created in the broad ligament just caudal to the ovarian pedicle. In group 1, the right ovarian pedicle was sealed with a VSD. A pean-styled, 18 cm long reusable instrument with 30° curved jaws (LS 2070, Valleylab/Covidien) was used with a snap-in electrode (LS 2071, Valleylab/Covidien) connected to a generator (LigaSure, Valleylab/Covidien). The electrodes are available in sterile packages for single use but were reused multiple times after cold sterilisation with paraformaldehyde (Asphalin B, Becht). The left ovary was removed after double ligation of the ovarian pedicle with polydioxanone (USP 3/0-0 according to the body weight) and single ligation of the tip of the uterine horn (SL). In both groups, Mayo scissors were used to transect the tissues cranial and caudal to the ovary. In group 2, the order of the haemostatic techniques was reversed.

After removal of both ovaries and inspection for bleeding, the abdomen was closed in a routine fashion (linea alba in a continuous pattern using polydioxanone, subcutaneous tissues with a continuous mattress suture using polyglecaprone and skin intradermally using polyglecaprone).

Test variables

The length of the procedure was recorded using a stopwatch. Recording started at the time of first incision and the following time points were recorded: identification of the right ovary, start of pedicle haemostasis of the right ovary, removal of the right ovary, identification of the left ovary, start of pedicle haemostasis of the left ovary, removal of the left ovary and end of the surgery. Any intra-operative problems encountered were recorded. When instrument failure of the VSD occurred, the stopwatch was paused and restarted when adaptive changes were made.

Follow-up

Dogs were sent home the same day as surgery after recovery from anaesthesia with instructions for postoperative care. Postoperative analgesia was provided by the administration of carprofen (2 mg/kg, Rimadyl, Pfizer) orally every 12 hours or meloxicam (0.2 mg/kg, Metacam, Boehringer Ingelheim) orally every 24 hours, for five days. The owner was contacted 10 days after the surgery and was asked about the recovery of the dog.

Statistical analysis

For the statistical evaluation, SPSS V.21 (IBM, USA) was used. The surgical time from identification of the ovary to its removal with the use of VS or SL was compared within each dog, using a paired t test (two-tailed). Because the data were not normally distributed, a Mann-Whitney U test was performed to compare the surgical time needed for identification with removal of the right versus left ovaries for each of the VS and SL techniques. The significance level for all statistical tests was set at P<0.05.

Results

The 20 intact female dogs belonged to the following breeds: Golden Retriever (n=4), Border collie, mixed breed, Chihuahua, Dachshund (n=2 each) and Yorkshire Terrier, White Shepherd, Lhasa Apso, Dalmatian, Cavalier King Charles Spaniel, Leonberger, Shi-Tsu and Bichon Frise (n=1 each). Mean age was 29 months (range 5–121 months). Mean bodyweight was 15.7 kg (range 1.8–52.9 kg), whereas the median BCS was 3/5 (range 2/5–5/5). Eleven dogs were prepubertal, one dog had only had one oestrous cycle and eight dogs had had multiple oestrous cycles before being presented for gonadectomy. At presentation, 10 dogs were two to three months after the last oestrous cycle whereas the stage of the cycle was unknown to the owner in the remaining dogs.

Intra-operative complications were rare. One dog developed bleeding at the left ovarian pedicle after SL. An extra ligature was placed to ensure haemostasis. In three cases VSD malfunctioning occurred. Replacement of the re-used electrode by a new one immediately solved the problem in all cases.

Mean duration of the complete surgical procedure was 29.28±11.30 minutes (range 12.50–62.13 minutes). Time from identification to removal of the ovary was significantly faster when VS was performed than when SL was done (2.22±0.58 v 4.10±1.13 minutes; P=0.0001).

Statistical analyses failed to identify a difference between the time from isolation to removal of right versus left ovaries with VS (P=0.143) as well as with SL (P=0.971).

No postoperative complications after discharge were reported by the owners when they were contacted 10 days after the surgery.

Discussion

The present study on open OVE in healthy dogs demonstrated that the use of a VSD significantly shortened the procedural time for ovarian pedicle haemostasis. Meanwhile, its use was found to be similarly safe and efficient in terms of haemostasis and intra-operative and short term complications as the conventional SL.

Previous studies evaluated different techniques for ovarian pedicle haemostasis in laparoscopic OVE procedures in dogs (van Nimwegen and others 2005, Mayhew and Brown 2007, van Nimwegen 2007, Öhlund and others 2011), amongst which VSDs have successfully been used. They not only do reliably seal large vessels (up to and including 7 mm), but also rely on a feedback-controlled response system that automatically discontinues the electrocoagulation process when the tissue is adequately sealed (Richter and others 2006). This technology reduces thermal necrosis and collateral damage when compared with traditional systems in which the amount of energy is subjectively dictated by the surgeon (Santini and others 2006, Pastore and others 2013). The LigaSure system demonstrated histologically milder side thermal injury than conventional monopolar and bipolar VSDs (Diamantis and others 2006). The seal created by the LigaSure is an intrinsic part of the vessel wall, which cannot be dislodged (Kennedy and others 1998).

Effective ligation is essential to assure adequate haemostasis, avoiding subsequent bleeding. Haemorrhage has been reported the most common complication of open OVE/OVH (Pearson 1973, Berzon 1979, Pollari and others 1996) and can potentially be fatal (Kyles and others 1996). Identified causes of ovarian pedicle haemorrhage are vessel rupture during strumming of the suspensory ligament (Burrow and others 2005), during pedicle handling and manipulations due to improper knot-tying technique (e.g. placement, spacing, tightness of the knot) in combination with excessive amount of fat in the ovarian pedicle (Adin 2011). Observations suggest that many seasoned veterinarians are still anxious about their ligation technique in bitch spays, especially in overweight dogs with bulky pedicles (Leitch and others 2012). Bleeding of the ovarian pedicle stump only occurred in one dog (the largest dog of the case series) after SL, necessitating placement of an additional ligature. It is hypothesised by the authors that the use of a VSD will reduce the risk of ovarian pedicle haemorrhage in open OVE in dogs compared with SL, especially in the hands of novice surgeons.

Notwithstanding the higher cost associated with a VSD than with the use of suture material, the authors believe that VS is very attractive for neutering bitches. It is a safe technique (also avoiding postoperative suture complications), easy to apply (and not operator dependent) and time-efficient (faster technique). Furthermore, the VSD will prove beneficial for many other surgical indications (e.g. splenectomy, tumour resection).

Although not studied specifically in the present study, it can also be argued that some of the complications observed after ovari (ohyster) ectomy (Adin 2011) are less likely to occur when VS is used compared with when SL is performed. Long term studies including large case numbers are needed to demonstrate whether LS indeed would result in lower complication rates.

The advantage of the LigaSure device used in the current study was the relatively large size of the electrodes (18 mm) allowing large bites of tissue being taken. In this regard, the number of seal cycles needed to bridge the ovarian pedicle was limited. The fact that there was no built-in divider, however, necessitated alternation between the VSD instrument and scissors. An additional disadvantage was that the single use electrodes that needed to be mounted on to the re-usable hand piece were very pliable and prone to twisting. If not assembled with care, an electric contact failure will occur, as was encountered in the present study in three out of 20 cases. Another potential issue after repeated re-sterilisation of the electrodes is the increase in stickiness to the tissues after sealing (Gracia-Calvo and others 2012). However, this issue was not observed in the current study.

Because of its more cranial location and its relatively shorter suspensory ligament (Wildt and others 1977), the right ovary is more tightly fixed in the abdomen. It was therefore hypothesised that, irrespective of the technique used, less time would be needed for ovarian pedicle haemostasis of left ovaries than right ovaries. Yet the current study failed to identify a significant difference in time. Potentially, the sample size was too limited to provide enough power to detect small time differences.

The current study showed that, in the hands of the first author, SL took approximately twice as long as VS. It is obvious that the surgeon is likely to have the biggest impact on the time to achieve haemostasis and efficacy of ligation. Therefore, the data obtained in this study can only be applied to the conditions in this study. Nevertheless, the first author is a seasoned surgeon and therefore it is expected that time differences between VS and SL OVE would even be more pronounced if both procedures were to be performed by novice surgeons.

Antibiotic use is not indicated for prophylactic use in these clean surgeries. However, at the time of conduction, at the first author's institution, antibiotic prophylaxis was routinely given irrespective of the type of surgery. The authors agree that this is not necessary and therefore it is not done any longer.

A limitation of this study included the re-use of the single use LigaSure electrodes. It was chosen not to take the time lost by replacing the re-used electrode in cases of technical failure into account when calculating the surgical times since single use of the disposable electrodes would most likely have prevented this issue. However, it can be argued that the time needed for swapping the hand piece when technical failure occurred should have been included in the respective procedural times. For veterinary purposes, the single use electrodes will be re-used in practice.

Finally, the sample size of the current study was rather small. The last is less relevant for the comparison of the procedural time required for VSD versus SL because the paired study design allowed for detailed comparison within the same animal. Nevertheless, it is plausible that differences in the isolation times for right versus left ovaries would have been observed if the study would have had more statistical power. Since surgical site complications might be expected to occur with a frequency of less than 1:20, any difference between the two techniques with regard to complications could not be evaluated.

In summary, it can be said that OVE using a VSD allows pedicle haemostasis with great ease. It simplifies OVE by negating the need for ligations and is safe and reliable. The results of the current study on open OVE in dogs indicated that ovarian pedicle haemostasis achieved by VS was significantly faster than by SL. The clinical implication of the current study may be a more widespread use of VS for routine surgeries such as open OVE/OVH amongst practitioners. The reluctance amongst (inexperienced) surgeons to neuter obese bitches may decrease.

  • Accepted October 2, 2014.

References

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Footnotes

  • Provenance: not commissioned; externally peer reviewed.

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