Laparoscopic Ovariohysterectomy in Nine Dogs
Minimally invasive surgery has been found in humans to reduce pain, incidence of infections, and duration of hospitalization. Minimally invasive procedures are also being described in veterinary medicine. Laparoscopic ovariohysterectomy (OHE) was performed on nine, healthy, intact female dogs using a Harmonic scalpel. Creatine kinase values were determined both before and 12 hours following the laparoscopic OHE; the magnitude of the difference between preoperative and postoperative creatine kinase values did not correlate with length of operative time, length of incisions, or amount of hemorrhage. Complications included one dog that had an omental herniation that was primarily repaired and one dog with seroma formation. Median surgical time for all dogs was 60 minutes (range, 35 to 100 minutes).
Introduction
There have been several reports documenting the advantages of minimally invasive surgical procedures in humans when compared to open surgical procedures. Thoroscopic procedures have been found to reduce pain-associated morbidity in humans.1 Laparoscopy is reported to reduce postoperative infections in the repair of perforated appendicitis in humans,2 and decreased recovery time has been reported in laparoscopic nephrectomies.3 Because of the advantages reported in humans, similar minimally invasive techniques are being explored in veterinary medicine. Thoracoscopic pericardectomy, laparoscopic gastropexy, and laparoscopic renal biopsy techniques have been demonstrated to be technically feasible, and they produced similar results when compared to open procedures.4–7
Ovariohysterectomy (OHE) is a necessity for many of our domestic companion animals, aiding in population control, disease prophylaxis, therapeutics, and behavior modification.8 Laparoscopic hysterectomy has been found in humans to reduce postoperative pain, blood loss, duration of hospital stays, time until return to normal gastric motility, and recovery time when compared to open hysterectomies.9–12 In veterinary medicine, laparoscopic OHE is an alternative approach that has the potential for less morbidity to be associated with its use than the traditional open procedure; reasons for this are many and are the same as those that have been defined in humans.
While the open technique is commonly performed in veterinary medicine, and it is taught in many veterinary schools as a basic surgery, there are benefits to the development of alternative techniques. Open procedures are often performed with small incisions, which decrease visualization and increase the risk of incomplete resection of ovarian tissue. This, in turn, could potentially lead to ovarian remnant syndrome and increased risk of mammary cancer and pyometra.13 A repeat surgery is technically challenging, as the anatomical landmarks are distorted with the formation of scar tissue. One of the advantages of laparoscopic techniques is superior visualization,14 which may reduce the risk of incomplete ovary resection.
In human medicine, minimally invasive surgical procedures are not only being developed as alternatives to the open approach, but some are becoming the preferred approach due to decreased pain and postoperative hospital stays.15 It is unlikely that the postoperative stay for OHE would be altered much by the use of minimally invasive techniques; however, the impact of decreased pain is a potential benefit that should be available to veterinary patients. Veterinarians are becoming better aware of the pain suffered by their patients, and approaches to assessing and addressing this are being implemented.16 A potential benefit of minimally invasive surgery in dogs is decreased pain. To determine if the potential benefits of decreased pain and risk of ovarian remnant syndrome are in fact real, the technique to perform laparoscopic OHE must be developed. Then, studies comparing laparoscopic OHE to open OHE should be performed, examining differences in pain and incidence of return to estrus. This study describes a laparoscopic technique for routine OHE in the dog.
While pain assessment techniques can be used to compare postoperative pain of open to laparoscopic OHE, human studies have relied primarily on immunological stress indicators in comparison studies.15 Future comparisons between laparoscopic and open procedures in dogs would benefit from the establishment of indicators of surgical stress. Creatine kinase is clinically used in small animal medicine as an indicator of muscle damage.17 It also has been used as an indicator of immunological stress in the comparison of laparoscopic to open surgical procedures in human infants.18 Preoperative and postoperative creatine kinase blood level samples were obtained to determine if this data might be an appropriate indicator of surgical stress in the dog.
Materials and Methods
Dogs
Nine female intact dogs with a mean body weight of 17.7 kg (range, 10 to 26 kg) were brought from the local humane society to the Virginia-Maryland Regional College of Veterinary Medicine (VMRCVM). All animal use was preapproved through the Animal Use Committee at VMRCVM. Ages were approximated based on dental eruption and wear and ranged from 5 months to 5 years. All dogs were found to be healthy on physical examination and minimum database of packed cell volume (PCV), total solids (TS), and blood urea nitrogen. Approximately 5 hours before induction and 12 hours after surgery, samples for serum creatine kinase were obtained on all dogs by lateral saphenous venapuncture.
Anesthetic Protocol
Dogs were sedated with acepromazine maleate (0.1 mg/kg body weight, intramuscularly). An intravenous (IV) catheter was placed in the right cephalic vein in all dogs. Dogs were then induced with propofol (4 mg/kg body weight, IV), and tracheal intubation was performed for general anesthesia. Anesthesia was maintained with isoflurane in oxygen delivered via a semiclosed circle system. The dogs were placed in sternal recumbency with the hind limbs extended forward. The lumbosacral area was clipped and scrubbed in preparation for sterile injection. A 20-gauge, 2.5-inch spinal needle was placed in the lumbosacral epidural space, and proper needle placement was confirmed by the hanging drop technique.19 Ketamine (3 mg/kg body weight) was diluted with sterile saline to a total volume of 3 mL for better distribution and cranial diffusion and was injected epidurally.2021 The patient was placed on a ventilator for the duration of the laparoscopic procedure. Ventilation was adjusted to maintain end-tidal carbon dioxide (CO2) between 35 and 45 mm Hg. Pulse, respiration, end-tidal CO2, and arterial hemoglobin saturation were monitored and recorded every 5 minutes throughout the procedure.
Surgical Technique
The patient was repositioned to be in dorsal recumbency, and the ventral abdomen (from the xiphoid to the pubis and to each inguinal fold) was clipped and aseptically prepared for laparoscopic surgery. Positioning of the patient, anesthetist, surgeon, and laparoscope operator is depicted in Figure 1. The patient was placed in the Trendelenburg position (head approximately 30° below the sacrum) to facilitate craniad displacement of the visceral contents of the abdominal cavity. A 1-cm, skin incision was made over the umbilicus, exposing the linea alba. Subcutaneous fat was excised to clearly visualize the linea alba, and two stay sutures of 3-0 nylon were placed parallel on either side of the linea alba. Traction was placed on the stay sutures to lift the body wall away from the viscera, and the cannula port was placed into the abdominal cavity through the linea alba using the Hasson technique.22 Pneumoperitoneum was established with an insufflatora through the cannula port to a pressure of 13 mm Hg using CO2 gas, and a 5-mm, 30° laparoscopeb was placed through the cannula port.c The light sourced was used to transilluminate the abdominal wall and identify the caudal superficial epigastric blood vessels prior to instrument port placement. Two skin incisions were made in a nonvascular area, paramedian to the midline and at the level of the inguinal fold [Figure 2]. Two 5-mm instrument trocarse were used to penetrate the abdominal wall and place the 5-mm cannulasf through the skin incisions. The laparoscope was used to visualize the entrance of the trocars into the abdominal cavity and direct placement away from viscera. Babcock forcepsg were inserted into the left paramedian trocar and were used to retract the intestines medially to facilitate visualization of the right uterine horn, proper ligament of the ovary, ovary, and suspensory ligament. An alligator grasperh inserted through the right paramedian trocar was then used to grasp the proper ligament of the ovary. The ovarian ligament was lifted such that traction was placed on the suspensory ligament. The Babcock forceps were then removed from the left paramedian trocar, and the harmonic ultrasonic scalpeli was introduced into the abdominal cavity. The laparoscope was placed such that the blades of the ultrasonic scalpel were in the center of the video monitorj at all times during the procedure. The harmonic scalpel was positioned such that the upper blade was toward the laparoscope, and therefore the tissue being transected was entirely visualized; this was done to avoid collateral damage to other abdominal viscera. The harmonic scalpel was used to transect the suspensory ligament, ovarian vascular pedicles, and the broad ligament of the uterus [Figure 3]. The coagulation mode was used on blood vessels >1 mm until approximately 2 to 3 mm of the surrounding tissue and blood vessels blanched, and then the cutting mode was applied to transect the vessel and associated tissue. As the broad ligament was transected, the alligator grasper was retracted to maintain tension on the ligament and associated blood vessels. The laparoscope was continuously repositioned to maintain the harmonic scalpel in the center of the video monitor. Transection of the uterus and associated uterine arteries was performed from left to right. The left middle uterine artery was coagulated and transected. The cervix was identified visually, and the uterus was transected and sealed closed approximately 1 cm proximal to the cervix using the cutting mode of the harmonic scalpel [Figure 4]. The right uterine artery was coagulated and transected. The left uterine horn was then identified at the origin of the uterus, lifted with the alligator grasper, and visualized to the left ovary and proper ligament of the ovary. Grasping the proper ligament of the ovary with the Babcock forceps, the suspensory ligament was again identified and transected using the harmonic scalpel. The Babcock forceps were clamped to the uterine body and were withdrawn through the left paramedian incision, which was extended by approximately 1 cm to allow for tissue removal. The uterine stump and ovarian artery remnants were assessed for bleeding using the laparoscope, and the abdominal cavity was visualized for blood. Once it was determined that there was no gross hemorrhage, the body wall of each paramedian incision was closed individually using 3-0 polydioxanone (PDS) in a cruciate pattern. The laparoscope was withdrawn, and pressure was applied to each side of the abdominal wall to facilitate the escape of CO2 gas from within the abdominal cavity through the umbilical incision prior to closure. Subcutaneous tissues were closed together using 3-0 PDS in a figure-eight pattern, making sure the knot was buried.
Postoperative Care
Patients were recovered from anesthesia uneventfully and were given one dose of morphine sulfate (0.5 mg/kg body weight, subcutaneously) approximately 2 hours following surgery.
Results
All of the patients’ preoperative values were within reference ranges. Median length of surgery was 60 minutes and ranged from 35 to 100 minutes (standard deviation [SD], ±18.45 minutes). The median intraoperative saturation of oxygen was 97% (SD, ±0.32), while end-tidal CO2 ranged from 31 to 42 mm Hg (median, 39.3; SD, ±3.82). The difference between pre- and postoperative creatine kinase varied greatly between patients, ranging from 123 to 2195 U/L (SD, ±719.69) [see Table]. There was not a direct correlation between length of surgery and change in creatine kinase. The harmonic scalpel effectively sealed all the vessels that were coagulated prior to transection. On rare occasions when larger vessels buried in the fat of the broad ligament were transected without coagulation, it was necessary to coagulate the ends of the transected vessels using the harmonic scalpel. This coagulation provided adequate hemostasis.
In all dogs, the flank incisions were subjectively judged to produce greater swelling in the postoperative period than the umbilical incision. In all but one dog, the left paramedian incision was extended to facilitate the removal of the reproductive organs, and this incision was subjectively judged to have greater swelling than the right paramedian incision in the postoperative period. In one dog, the removal of the gravid (approximately 45 to 50 days gestation) reproductive tract was facilitated by extension of the umbilical incision. This dog had equal swelling of the paramedian incisions, and the swelling of the umbilical incision was not greater than the swelling of the umbilical incisions of the other spayed dogs.
Complications
Problems encountered included increased postoperative swelling of the right paramedian incision of one dog. The dog was anesthetized and taken to surgery, which revealed the swelling to be a herniation of omentum through the abdominal wall. The herniation was thought to be due to incomplete closure of the rectus sheath, which at the time of surgery was not considered to be consequential. The hernia was closed using 3-0 PDS in a simple interrupted pattern, and the dog recovered from anesthesia. Another dog formed a seroma at the site of the left flank incision. Both dogs were placed on antibiotics for 10 days (cephalexin, 25 mg/kg body weight, per os, q 12 hours). Follow-up 6 weeks later determined that these initial complications had resolved, and no further complications were seen. Follow-up 8 months later on three dogs, including the dog that had experienced herniation of omentum, found no further complications. The remaining six dogs had been adopted and were not available for examination.
Discussion
Laparoscopic OHE is a viable alternative to the traditional open approach. Superior visualization is provided by the laparoscopic camera’s ability to get close to structure and magnify the image to the level desired based on distance. The duration of the operative time in this study was reasonable and is likely to lessen with experience.
The harmonic scalpel was chosen for performance of this procedure based on the versatility demonstrated in preliminary work. The harmonic scalpel uses mechanical energy to cut and cauterize tissue. Electrical stimulation causes expansion and contraction of piezoelectric crystals stacked within the handpiece of the unit. This mechanical energy is transferred to the blade that vibrates 50 to 100 μm longitudinally at 55,500 cycles per second. Only the blade is able to cut and coagulate as the piezoelectric crystals causing the vibration of the blade are shielded from tissues. Collateral damage has also been reported to be minimal, and precautions (such as ensuring contact of the blade only with the target tissue and maintaining visualization of the entire blade at all times) are appropriate. Coagulation occurs because the mechanical energy of the blade on tissue causes breakage of intracellular hydrogen bonds, resulting in protein denaturation. Cutting occurs secondary to the motion of the blade. Cutting and coagulation both occur secondary to the vibration of the blade, and the degree to which each occurs is dependent on the shape of the surface of the blade, contact duration, and pressure applied. Vessels should be coagulated, which is visualized as blanching of the vessel, prior to transection to ensure adequate hemostasis. The reported maximum-size vessel that can be safely transected is 2 mm.23 The vessels transected in these procedures were not measured; however, no hemorrhage occurred in the mature animals or the one patient with a gravid uterus, despite enlarged vessels. Parenchymal tissue can be transected without coagulation, because sufficient hemostasis is obtained through the contact duration and pressure required to cut tissue. Dissection can be performed using the vibration of the blade tip to initiate cavitation. This effect results from transient low pressure causing vaporization of intercellular fluids that dissects along tissue planes.
The harmonic scalpel avoids the problems associated with the passing of electric current through a patient; however, it can still cause collateral tissue damage by contact with nontarget tissue. Maintaining visualization of the entire blade of the harmonic scalpel and holding tissues away from nontarget tissues will reduce the risk of collateral tissue damage. In the authors’ study, this was accomplished by maintaining the blade of the harmonic scalpel in the center of the monitor at a distance that included the entire blade along with surrounding tissue, grasping and retracting the target tissue away from other structures, and manipulating the blade to visualize all angles of the blade in contact with tissue before cutting and coagulating tissue.
Transection of the suspensory ligament on the left side was technically more challenging than the right side, because the laparoscope and instruments were pointing away from the monitor, resulting in paradoxical movement. Placing the monitor at the head of the patient and having the surgeon and laparoscope operator at the tail would not result in paradoxical movement and may decrease surgical time.
Serum creatine kinase levels have been used in the comparison of open extramucosal pyloromyotomy and laparoscopic fundoplications in human pediatrics.18 In this study, serum creatine kinase levels were determined both in the preoperative and postoperative periods. The degree of change between preoperative and postoperative creatine kinase levels varied greatly between dogs but did not correlate with duration of procedure or any other variable recorded in the authors’ study. It did seem to correlate with the subjective assessment of the degree of struggle the dog produced when samples were taken. Dogs that struggled more when preoperative samples were taken had higher postoperative samples than dogs that were quiet. In this study, creatine kinase was not a predictable indicator of surgical stress.
Because the dogs used in this study were maintained at an animal shelter, the animals were not kept quiet in the postoperative period. Therefore, the complications that occurred were not unexpected. However, the increased swelling of the paramedian incisions, especially the left incision that was extended during surgery, may be attributable to the decreased thickness of the epidermis in this region.24 In one dog, the umbilical incision that was extended to remove the gravid reproductive tract did not demonstrate increased swelling. Extension of the umbilical incision to facilitate exteriorization of the reproductive tract has been used in laparoscopic OHEs performed by the authors after completion of this study and appears to prevent the increased swelling seen in this study.
Conclusion
Laparoscopic OHE is an alternative surgical technique that deserves further investigation. Potential advantages of laparoscopic OHE that should be studied include reduced postoperative pain and reduction of the risk of incomplete ovarian tissue resection. The harmonic scalpel was a versatile tool in accomplishing the procedure, and the authors of this study recommend its use.
Electronic Laproflator; Karl Storz Endoscopy – America, Inc., Culver City, CA
Hopkins II, model #62006; Karl Storz Endoscopy, Culver City, CA
Veress Trocar, 355 m; Ethicon Endo-Surgery, Inc., Cincinnati, OH
Dyobrite 3000; Smith & Nephew, Andover, MA
5-mm instrument trocars; Applemed Medical Corp., Bolton, MA
5-mm cannulas; Applemed Medical Corp., Bolton, MA
Babcock, 5BB; Ethicon Endo-Surgery, Inc., Cincinnati, OH
Alligator grasper, 5DSG; Ethicon Endo-Surgery, Inc., Cincinnati, OH
Ultracision, LCS-K5; Ethicon Endo-Surgery, Inc., Cincinnati, OH
Trinitron Images, medical grade; Sony Corporation, Shinagawa-ku, Tokyo, Japan
Acknowledgment
The authors thank Erin Kasell for her technical assistance in this study.
Citation: Journal of the American Animal Hospital Association 39, 4; 10.5326/0390391
Citation: Journal of the American Animal Hospital Association 39, 4; 10.5326/0390391
Citation: Journal of the American Animal Hospital Association 39, 4; 10.5326/0390391
Citation: Journal of the American Animal Hospital Association 39, 4; 10.5326/0390391
Positioning of equipment and personnel during laparoscopic ovariohysterectomy in nine dogs.
Portal placement for abdominal laparoscopy.
Transection of the suspensory ligament using the harmonic scalpel, as viewed through the laparoscope in the umbilical portal.
Transection of the uterine body using the harmonic scalpel, as viewed through the laparoscope in the umbilical portal.
