Trocars

Definition
Procedures Using Trocars
Description of Trocar Usage
Description of Trocar Designs
Risks
Morbidity and mortality rates

Definition

A trocar is a surgical instrument. It is a hollow cylinder into which fits another piece called an obturator with a pointed or blunt end. It is used to insert various surgical implements into a blood vessel or body cavity. Trocars were originally three-sided pointed instruments, but are now made in multiple designs with varying degrees of sharpness. Sometimes only the obturator portion is referred to as the trocar and the entire apparatus is referred to as trocar and cannula.

Procedures Using Trocars

Trocars may be used to insert surgical instruments during a laparoscopy, a procedure that allows for examination of the peritoneal cavity with minimal cutting of the body wall. Laparoscopic procedures in which trocars are used include hysterectomy, endometriosis ablation, and salpingectomy. Trocars can be used to help insert an intravenous cannula (flexible tube) into a blood vessel to allow for the administration of fluids or medication. Trocars may also be used on human cadavers during the embalming procedure to assist in draining bodily fluids in a process known as aspiration.

Description of Trocar Usage

Laparoscopy

The first trocar used in a laparoscopic procedure is called the primary trocar. A primary trocar is inserted into the peritoneal cavity, and the obturator portion is withdrawn. The insertion of the primary trocar into the peritoneal cavity requires enough force to penetrate the body wall with the obturator, while avoiding damage to the underlying structures. Appropriate training and skill is required to properly insert the primary trocar with guided force known as a “controlled jab”. The cannula remains in the insertion site and is used as an access port through which to put other instruments in place. Through the cannula, a laparoscope (camera), or other surgical tool may be inserted into the body cavity. Once the laparoscope is inserted, the surgeon can see the internal structures of the body. However, when the primary trocar is inserted, it is usually done without being able to view the structures lying just underneath it. Hence insertion of the primary trocar is sometimes referred to as a “blind jab” Potential for damage to internal organs is decreased by inflating the abdominal cavity with carbon dioxide gas before trocar insertion, to hold the body wall away from the organs. Multiple trocars may be used for each procedure. Laparoscopies commonly require two to five trocars for completion. Insertion of each trocar carries the risk for a life threatening injury.

Embalming

Trocars are used during the embalming of human cadavers to insert tubes for drainage of bodily fluids. Once the blood has been replaced with embalming chemicals, the trocar is inserted and attached to a suction hose for aspiration. The insertion is made near the umbilicus in order to aspirate the main body cavities. Once the fluid is drained the trocar is detached from the aspirating hose and attached to a bottle of cavity-embalming fluid. The trocar is then used to fill

the body cavities with the fluid. The trocar puncture is sealed with a plastic plug called a trocar button.

Description of Trocar Designs

Trocars have evolved from one to two basic designs to many. According to the last trocar review done by the FDA, in 2003 there were greater than 100 different brand names being produced from greater than 20 different manufacturers. Trocars may be pointed with a cutting blade at the tip, blunt and bladeless, fitted with a protective shield, or contain a tiny camera for guided, optical entry into the body.

Cutting Trocars

Cutting trocars have been designed with sharp tips in order to create an incision in the body wall and facilitate insertion of the cannula into the peritoneal cavity. Sharp trocar ends may be three-sided and pyramidal, or conical. Multiple types of cutting trocarsexist, most of which require blind entry into the peritoneal cavity. Cutting trocars require the least amount of force to insert into the body cavity. However, they cause the greatest amount of postsurgical insertion site pain, scarring, and sometimes hernia formation. Cutting trocars pose the greatest risk for damage to a major blood vessel or puncture of internal organs such as the intestines. Cutting trocars are associated with the greatest number of life threatening injuries, especially in patients for whom trocar insertion is difficult to perform.

Shielded Cutting Trocars

Trocars have been designed with a retractable, protective shield that covers the pointed tip before and after insertion into the peritoneal cavity. The shield was added to trocar designs in 1984 in an attempt to protect the abdominal and pelvic blood vessels and organs from accidental puncture with the trocar tip. For this reason shielded tips were originally called “safety trocars”. However, whether or not the shielded tip actually warrants the term “safety trocar” is controversial. Serious injuries as well as deaths have both been associated with shielded trocars. According to trocar safety reviews done by the FDA, shielded trocars may have a somewhat improved safety profile if used properly. However, a general concern for the use of shielded trocars is a mistaken sense of security on the part of the surgeon, leading to inadvertent injury despite the shield. The shield itself has been shown to damage blood vessels, and shielded trocars can still cause life threatening injury. Because of a lack of data proving shielded trocars as “safe” and concern for the issues previously described, in 1996 the FDA asked manufacturers to stop using the term “safety trocars” when describing a shielded trocars.

Bladeless Trocars

Trocars have also been designed in varying degrees of bluntness to help prevent accidental damage to blood vessels or internal organs when inserted into the peritoneal cavity. A Hasson trocar is very blunt and pushes through the layers of the abdominal wall instead of cutting them. The tissue fibers are merely separated instead of sliced, and can reposition naturally after the trocar is removed. Compared with cutting trocars, the blunt trocars require more force to insert into the peritoneal cavity. However, they create smaller trocar insertion tissue defects that take less time to heal, decrease the incidence of hernia formation, cause less scarring, and less postsurgical trocar insertion site pain. Bladeless trocars were designed in an attempt to minimize trocar-related injury or puncture of internal structures.

A Hasson trocar is implemented using the Hasson “cut-down” or “open” technique. Hasson trocars are so blunt-ended that they can only be inserted into the peritoneal cavity after the surgeon makes a small 2 to 3 cm incision through which to push the trocar (hence the term “cut-dow” technique). The surgeon can see the area through which the trocar is penetrating and so the procedure does not require blind insertion (hence the term “open” technique). The Hasson tro-car can then be used along with retractors to introduce other tools such as a laparoscope into the body cavity. The Hasson technique offers the advantage over traditional cutting trocars of being an open technique (as opposed to blind), and so may further minimize risk to blood vessels and internal organs. Whether or not the Hasson technique has succeeded as such is a matter of controversy, with studies especially differing on whether there is any real advantage regarding organ injury. Some types of blunt trocars are radially-expanding upon entry of the abdominal cavity to lift the abdominal wall up and away from the internal structures. Whether this design of trocar confers greater safety margins and reduces risk of injury is also controversial.

Optical Trocars

Each of the trocars discussed so far offer only blind access into the peritoneal cavity, potentially resulting in inadvertent, life threatening injury. In 1994, trocars were developed that have a tiny viewing “window” positioned at their tip for a laparoscope. This design of trocar enables the surgeon to observe the primary trocar insertion through the laparoscope and removes the necessity of a blind initial puncture. The surgeon can actually view each tissue layer being penetrated by the trocar device, as well as the underlying abdominal cavity and internal structures. While this design is an improvement over blind insertion trocars, injuries are still reported with optical trocars.

Risks

Trocar use is associated with risk of me-threatening injury. Injuries most commonly occur during the initial insertion of the primary trocar, often a blind insertion of the trocar before the laparoscope can be inserted. The risk is that the force being applied to penetrate the abdominal wall may accidentally propel the trocar into a blood vessel or puncture an internal organ such as the large intestine. Blood vessel hemorrhage or life threatening bacterial infections may result. Each patient and circumstance requires a different amount of force to be applied for trocar insertion. It requires skill and experience on the part of the surgeon insert the trocar with sufficient force to penetrate the abdominal cavity, while still maintaining enough control to stop the movement of the trocar once the abdominal wall has been traversed. The safety margin between the force required for troca insertion and trocar injury is very slim, especially for children and small, thin adults. Blunt trocars require more force for insertion than cutting trocars. Despite the blunt edges of these trocars, the extra force required for penetration contributes to risk of propelling the trocar into and injuring the bowels. Additionally, the larger a trocar is, the greater the risk of injury to the patient. For each patient, surgeons use the smallest trocar possible.

Patients who have had prior abdominal surgery have a higher risk of trocar injury. After abdominal surgery, the internal organs and other structures of the abdominal cavity sometimes develop scar tissue that causes them to adhere to the abdominal wall. If internal structures are attached to the site of trocar entry, even filling the abdomen with carbon dioxide gas is not sufficient to keep them out of the path of injury upon primary trocar insertion. For this reason, blind insertion trocars should not be used on patients with a history of abdominal surgery. If lower abdominal surgery is included in patient history, there is a location that may be safely used for trocar insertion known as Palmer’s Point. Palmer’s Point is located in the upper left quadrant of the abdomen, and usually does not contain internal structures that may be injured upon trocar insertion.

Morbidity and mortality rates

The most common types of trocar injury are blood vessel damage leading to hemorrhage and bowel injury leading to peritoneal infection. The morbidity and mortality of trocarrelated injuries increases when not caught early on. A delay in recognition or treatment of trocar injuries can be fatal for the patient. Injuries occur most frequently with insertion of the primary trocar, which may be the step in laparoscopies associated with the greatest risk.

Trocar use requires extensive training, experience, manual skill, muscular strength, control, and knowledge of the associated risks for each type of patient. Morbidity and mortality are due to a combination of the surgeon’s skill level, the type of trocar, and patient-based risk factors. Whether on the part of the patient or the doctor, the failure of recognition of the symptoms of injury in a timely manner contribute much to the morbidity and mortality of trocar usage.

Patient-based risk factors for injury with blind trocar insertion

• Prior abdominal surgery
• Children
• Small, thin body type
• Alterations in abdomen skin due to multiple pregnancies
• Atrophied abdominal musculature

Alternatives to procedures with blind trocar insertion

• Laparotomy
• Hasson open technique
• Radially-expanding and optical-access trocars

KEY TERMS

Atrophy— Wasting of body tissues.

Cadaver— A dead body.

Cannula— A tube inserted into a body cavity.

Endometriosis Ablation— Procedure of removing endometrial tissue from deposition on structures within the abdominal cavity.

Embalming— Process of treating a dead body with chemicals to preserve it from decay.

Hemorrhage— Excessive blood loss through blood vessel walls.

Hernia— Protrusion of a structure through the tissues normally containing it.

Hysterectomy— Removal of the uterus.

Laparoscope— Tiny camera inserted into the body and used in surgical procedures called laparoscopies.

Laparoscopy— A type of minimally invasive surgery performed in the peritoneal cavity.

Laparotomy— Incision into the loin.

Morbidity— A state of disease or illness.

Obturator— Any structure that occludes an opening. A trocar obturator has a tip used to penetrate the body wall while being held in the cannula of the trocar apparatus.

Peritoneal Cavity— Part of the abdominal cavity holding many organs.

Retractor— Surgical tool used to hold structures away from the surgical field.

Salpingectomy— Removal of the uterine tube.

• Use of Palmer’s point for trocar insertion (for patients with a history of prior abdominal surgery)

Potential signs and symptoms of internal hemorrhage into abdominal cavity

• Anemia, fatigue, and pallor
• Low-grade fever
• Increased heart rate
• Low blood pressure
• Shoulder pain
• Dizziness
• Faintness
• Nausea
• Lack of appetite

Potential signs and symptoms of untreated bowel injury

• Tender abdomen
• Pain
• Fever and chills
• Loss of appetite
• Nausea and vomiting
• Increased breathing rate
• Increased heart rate
• Low blood pressure
• Decreased urine production
• Inability to pass gas or feces

Resources

PERIODICALS

Fuller J, Scott W, Ashar B, Corrado J. Laparoscopic Trocar Injuries: A report from a U.S. Food and Drug Administration (FDA) Center for Devices and Radiological Health (CDRH) Systematic Technology Assessment of Medical Products (STAMP) Committee. FDA: Nov. 2003.

Maria Basile, PhD

Troponins test seeCardiac marker tests