Minimally invasive surgery -an overview by Helen North

ABSTRACT: Minimally invasive surgery (MIS) is not currently commonly performed in most general veterinary practices. Some veterinary surgeons {VS) may be reluctant to progress to MIS owing to limitations they may associate with it, such as: equipment set-up cost, the requirement for additional training, the learning curve and the initially increased surgical time.' MIS is, however, becoming favoured in specialist veterinary hospitals for performing several diagnostic and interventional procedures. This article will give a basic overview of what can be achieved using minimally invasive techniques and the equipment and patient care that is required.

Minimally invasive procedures

Many advanced laparoscopic procedures, such as adrenalectomy and cholecystectomy, were first performed in humans in the late 1980s and early 1990s;2 with video assisted thoracic surgery (VATS) for the treatment of chylothorax and patent ductus arteriosus (PDA) occlusion also being described during this period.3

Currently, there are at least a dozen laparoscopic and thoracoscopic techniques that have been developed and are being used in small animal practice (Tables 1 & 2).2

Many surgeries are carried out entirely within the abdomen, while others are laparoscopic-assisted procedures. During laparoscopic-assisted procedures, the surgical site is partially extracted through a lengthened trochar site. Laparoscopic surgery is very useful to aid in diagnosis – nearly every abdominal organ or mass can be examined or biopsied in this way.

The ability to place the ‘scope’ next to a mass produces superior images to those seen with the naked eye – the surfaces of organs can be viewed and focal lesions selectively biopsied. Thoracoscopic exploration is useful for intrathoracic conditions requiring diagnosis and treatment.

Thoracoscopy provides excellent exposure of the pleural space, with a much smaller incision than median sternotomy or lateral thoracotomy, and does not require the rib retraction – a major cause of morbidity with all thoracotomies (Figure 1).

Figure 1: Partial pericardectomy

Equipment and instrumentation

Rigid endoscopes, suitable for use in small animal laparoscopy and thoracoscopy, range from 2.7mm to 10mm in diameter (Figure 2). The size of endoscope used depends on the size of the patient, and where it is to be used.

Figure 2: Rigid endoscopes, 10mm, 5mm and 2.7mm

A 5mm scope is suitable for nearly all sizes of dog when performing thoracoscopy. For laparoscopy, the 5mm is suitable for cats and most dogs; whereas the 10mm can be used in dogs weighing over 10 – 15kg.

Various angles of vision are available with the 0-degree endoscopes giving a normal field of view. In thoracoscopy, the visual field can be increased by using a 30- degree endoscope, the surgeon can ‘look around corners’ using the offset angle and more of the cavity can be evaluated.

Endoscopes are notoriously fragile and expensive, so they require suitable care and attention during cleaning, sterilisation and storage. The best methods of sterilisation are either ethylene oxide gas or cold chemical sterilisation at the time that the scope is required; and then rinsed with sterile water or saline and dried with a sterile towel. Light-source cables and camera heads are normally also submersible in this solution, if gas sterilisation is not available.

There is a vast range of surgical instruments available for use in MIS; including biopsy forceps, scissors and atraumatic forceps (Figure 3). Other equipment and instruments available include stapling devices, pre-tied ligatures, specimen collection bags, endoscopic suturing devices and vessel- sealing devices. To enable the images from the surgery to be displayed on a monitor, the endoscope must be connected to a camera unit and a light source to provide illumination. Pictures and videos can be captured and recorded using a digital recording device.

Figure 3: Endoscopic instrumentation, biopsy forceps, a traumatic Babcock forceps and scissors

Insufflation of the abdomen is required in laparoscopy for adequate visualisation and surgical manipulation. High-flow insufflators are equipped with feedback mechanisms that regulate intra-abdominal pressure to a preset level. The pressure is generally maintained at 10 – 15mm Hg to avoid overinflation and compromise of venous return. Carbon dioxide (C02) is used, as it is inexpensive, does not support combustion and is diffusible in the blood.

The endoscope and surgical operating instruments are introduced into the abdominal or thoracic cavity via pre¬placed trocar/cannula. These must be airtight for laparoscopy to prevent the C02 from escaping; this is achieved via valves in the cannula.

The cannulae have side-ports on them to which the insufflation line is attached (Figure 4). In thoracoscopy this type of trochar is not necessary as insufflation is rarely used. Blunt trochar/cannulae are placed through ‘mini-thoracotomies’ allowing for establishment of pneumothorax prior to insertion, decreasing the risk of lung trauma (Figure 5).

Figure 4: Laparoscopic trochars and ports

Figure 5: Thoracoscopic trochars and ports

As with any surgery, during MI procedures the surgeon depends on team members and requires the complex equipment to function effectively and efficiently; therefore, it is recommended that the VN involved in surgery becomes familiar with the procedures and the equipment needed.

She or he should have a clear understanding of how all the instruments and equipment function and monitor for any damage to ensure the health and safety of patients and staff as equipment failures can adversely affect the quality of the surgical intervention.4

Minimally invasive surgery requires at least two people scrubbed in to perform it – the surgeon and an assistant to guide the endoscope providing the field of view (Figure 6). It is preferable for the surgeon if the assistant is someone who regularly performs the procedures alongside them, an ideal role for the VN who can become proficient in assisting – performing an important role in the development of a skilled surgical team.

Figure 6: Laparoscopy – the surgeon stands caudal to the patient with the screen directly ahead.

Perioperative care and anaesthesia

Patients undergoing minimally invasive surgery will have a routine work-up. The patient should be surgically prepared as for open surgery because the surgeon must be ready to convert at any time during the procedure should complications occur. Consent from the owner for conversion to open surgery should be sought prior to the procedure.

In preparation for a laparoscopy, the patients bladder should be emptied to prevent it from compromising visualisation of other abdominal organs and to prevent any inadvertent damage.

Patient positioning on the table should be secure and appropriate for the procedure. The ability to change position of the patient by tilting the operating table may be desirable to allow gravity to provide improved exposure of the surgical site.

Mechanical ventilation is standard practice for thoracoscopy owing to the establishment of a pneumothorax, and the anaesthesia protocol should be tailored to the individual needs of the patient. The lungs are intentionally underinflated to provide space in the thorax to work, or selective intubation may sometimes be performed allowing single lung ventilation. Mechanical or assisted ventilation is also important during laparoscopy.

Peritoneal insufflation with carbon dioxide applies pressure to the diaphragm, thereby reducing vital lung capacity. This, combined with carbon dioxide absorbed from the peritoneal surfaces, causes an increase in arterial tension of carbon dioxide (PaC02).

Arterial blood pressure is affected by the increased intrathoracic pressure produced by artificial ventilation decreasing venous return; ventilation is adjusted based upon the end-tidal carbon dioxide and blood pressure. Adequate monitoring equipment must be used to detect changes and make adjustments as required; this includes capnography, blood pressure, continuous electrocardiogram and pulse oximetery.

Any patient undergoing thoracoscopy should be treated as for a thoracotomy. Placement of a thoracoscopy tube is recommended to evacuate the pleural space following port closure and close monitoring of respiration should be undertaken on recovery.

Surgery will always result in tissue trauma, pain and physiological stress to varying degrees. A few comparative veterinary studies of MIS versus open surgery provide evidence that the MI approach does reduce postoperative pain and animals can return to normal function and activity levels sooner than those that have undergone open surgery. The smaller incisions may also result in fewer postoperative complications, such as wound infection and dehiscence, bleeding and seroma formation.

Postoperatively, all patients should be monitored and pain-scored as they would be for an open procedure and prescribed analgesia administered as required. Analgesia remains an important aspect of patient care and cannot be overlooked because the patient is considered to have been treated with a less painful procedure.

Summary

Patient stress is reduced after surgery with the use of analgesic drugs. However, this can also be achieved by decreasing the surgical insult to the body, as is achieved with MIS. As minimally invasive procedures become more popular in small animal practice and surgeons’ experience increases, more complex interventions are becoming available. With improved clinical outcomes, MIS is likely to become more in demand as many pet owners desire the same advanced medical and surgical treatments for their pets as they would for themselves.

Author

Helen North DipHE CVN RVN MBVNA

Helen has worked at Dick White Referrals for four years as a theatre nurse. She holds the Advanced Diploma in Veterinary Nursing for which she undertook a literature review in the use of minimally invasive surgery in small animals. Helen previously travelled to the University of Georgia, Atlanta, to take part in a two-day course on advanced laparoscopic and thoracoscopic surgery.

To cite this article use either

DOI: 10.1111/|.2045-0648 2012.00211.x or Veterinary Nursing Journal Vol 27 pp 328-330

References

1. HANCOCK. R B.. LANZ. O. I.. WALDRON. O R . DUNCAN. R B . BROARDSTONE, R. V and HENDRIX. P K [2005] Comparison of Postoperative Pain Alter Ovariohysterectomy by Harmonic Scalpel-Assisted Laparoscopy Compared with Median Celiotomy and Ligation in Dogs', Veterinary Surgery. 34: 273-282

2. MAYHEW. P. [2009] Advanced Laparoscopic Procedures (Hepatobiliary. Endocrme) in Dogs and Cats', Veterinary Clinics of North America Small Animal Practice, 39 925-939 3. ALLMAN. D. A , RADLINSKY. M G . RALPH, A. G and RAWLINGS. C A. [2010] 'Thoracoscopic Thoracic Duct Ligation and Thoracoscopic Pericardectomy for Treatment of Chylothorax in Dogs. Veterinary Surgery. 39:
21-27.

4 ULMER. B [2010] Best Practices for Minimally Invasive Procedures. Association of Perioperative Registered Nurses Journal. 91151: 558-572.

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