Section 6.4: Arterial Injection & Cavity Treatment Procedures
Key Takeaways
- Arterial injection uses the vascular system to distribute preservative solution, requiring a balance of pressure and rate of flow.
- Venous drainage is essential to make room for arterial fluid, remove blood discoloration, and prevent post-embalming distension.
- Restricted cervical injection (RCI) provides independent control over facial preservation, minimizing swelling risk.
- Trocar guides provide precise anatomical pathways to aspirate hollow viscera and prevent purge.
- Cavity treatment involves two distinct phases: aspiration of fluids/gases and injection of concentrated cavity fluid.
Section 6.4: Arterial Injection & Cavity Treatment Procedures
The embalming process is split into two major phases: vascular (arterial) embalming and cavity embalming. Together, these procedures ensure the disinfection, preservation, and restoration of the deceased body. This section details the physiological principles, instrumentation, and practical protocols required for successful arterial injection, drainage, and cavity treatment.
1. Principles of Arterial Injection
Arterial injection is the introduction of embalming chemical solutions into the arteries of the deceased to distribute them throughout the vascular system and into the tissues.
Injection Pressure and Rate of Flow
To achieve optimal distribution without damaging the vascular structure, the embalmer must carefully regulate two key variables:
- Injection Pressure: The force required to distribute the embalming solution through the vascular system. It is measured in pounds per square inch (psi).
- Rate of Flow: The amount of embalming solution injected in a given period, typically measured in ounces per minute (oz/min).
Understanding these pressure types is critical for the national board exam:
- Potential Pressure: The pressure reading on the gauge of the embalming machine when the motor is running but the injector valve is closed.
- Actual Pressure: The pressure reading on the gauge when the injector valve is open and the fluid is actively flowing into the body.
- Differential Pressure: The difference between potential pressure and actual pressure (Potential - Actual = Differential). Differential pressure represents the resistance in the vascular system and is directly proportional to the rate of flow.
Rule of Thumb: The embalmer should always inject at the lowest pressure and lowest rate of flow that will achieve uniform distribution without causing tissue distension (swelling), particularly in the facial tissues.
2. Venous Drainage & Instrumentation
Venous drainage is the removal of blood, blood clots, interstitial fluid, lymph, and embalming solution from the vascular system. It is impossible to inject arterial fluid without concurrently or sequentially draining venous blood, as the vascular system is a closed loop.
Purpose of Drainage
- To make room for the arterial preservative solution.
- To reduce secondary dilution of the embalming fluid by removing blood and interstitial fluid.
- To remove blood discolorations (such as livor mortis and post-mortem stain).
- To prevent post-embalming distension and accelerated decomposition.
Drainage Instrumentation
- Drain Tubes: Metal tubes inserted directly into veins (commonly the internal jugular or femoral). They help keep the vein open, allow the embalmer to control drainage flow via a plunger, and reduce splatter.
- Spring Forceps: Used to grasp and open veins, allowing blood to flow freely into the drain table drain.
Methods of Drainage
Embalmers utilize three primary techniques to manage drainage during injection:
| Method | Description | Advantages & Indications |
|---|---|---|
| Alternate Drainage | The arterial fluid is injected with the drain tube closed. Once a desired pressure is reached, injection is stopped, and the drain tube is opened. The process is repeated. | Prevents short-circuiting; maximizes fluid distribution and tissue saturation. |
| Concurrent (Continuous) Drainage | Injection and drainage occur simultaneously throughout the entire procedure. | Good for cases with low vascular resistance; saves time. However, it can lead to 'short-circuiting' (fluid path of least resistance). |
| Intermittent Drainage | Injection is continuous, while the drain tube is opened and closed at regular intervals. | Encourages pressure buildup to open collapsed capillaries and distribute fluid to extremities. |
3. Restricted Cervical Injection (RCI)
Restricted Cervical Injection (RCI) is a specialized injection technique that involves raising both the right and left common carotid arteries, along with the right internal jugular vein.
The RCI Protocol
- Isolate Vessels: Both common carotid arteries are isolated and raised.
- Ligation of the Left Carotid: The left common carotid is tied off (ligated) inferiorly (towards the heart) and a cannula is placed pointing superiorly (towards the head). The cannula remains closed during trunk injection.
- Ligation of the Right Carotid: The right common carotid is ligated inferiorly, and a cannula is placed pointing superiorly (towards the head). A second cannula is placed pointing inferiorly (towards the trunk).
- Trunk Injection: The body (trunk and limbs) is injected through the inferior tube in the right common carotid. During this phase, both superior cannulas (pointing to the head) remain closed, preventing fluid from entering the head.
- Head Injection: The left and right sides of the head are injected independently using the superior cannulas.
Advantages of Restricted Cervical Injection
- Independent Control: The embalmer can use a different fluid mixture, volume, pressure, and rate of flow for the head than for the rest of the body.
- Prevention of Facial Swelling: High pressure and rapid flow can be used on the body to overcome blockage or edema, while a very gentle, low-pressure injection is used for the head.
- Customized Cosmetology: Active dyes can be added to the facial injection without discoloring the trunk, or a stronger solution can be used to treat facial trauma or jaundice.
- Recommended for Challenging Cases: Always indicated in cases of trauma, facial edema, jaundice, renal failure, or when restorative art is anticipated.
4. Cavity Treatment & Trocar Guides
Arterial injection does not reach the contents of the hollow viscera (stomach, intestines, bladder, lungs). To prevent decomposition, gas formation, and purge, cavity treatment is mandatory. It consists of two steps: aspiration (removal of gas, fluids, and semi-solids) and injection of concentrated cavity chemical.
The Trocar
A trocar is a long, hollow metal instrument (typically 18 inches long with a threaded point) used to aspirate and inject the thoracic, abdominal, and pelvic cavities.
Anatomical Trocar Guides
To safely navigate the internal organs, the trocar is inserted two inches superior and two inches to the left of the umbilicus (navel). From this insertion point, the embalmer directs the trocar toward four key anatomical targets:
| Target | Trocar Guide (Path of Insertion) |
|---|---|
| Stomach | Direct the trocar point toward the intersection of the fifth intercostal space and the left mid-axillary line (established by a line from the left anterior superior iliac spine to the lobe of the right ear). |
| Cecum | Direct the trocar point toward a point one-fourth of the distance from the right anterior superior iliac spine to the pubic symphysis. |
| Urinary Bladder | Direct the trocar point toward the intersection of the median line and the pubic symphysis (symphysis pubis). |
| Right Atrium of the Heart | Direct the trocar point along a line from the left anterior superior iliac spine to the lobe of the right ear, keeping the trocar close to the anterior chest wall and piercing the diaphragm. |
5. Cavity Aspiration & Fluid Injection
Cavity Aspiration
Aspiration utilizes a suction device (a hydroaspirator or electric aspirator) connected to the trocar via flexible tubing. The embalmer systematically guides the trocar through the three main cavities to evacuate contents:
- Thoracic Cavity: Piercing the lungs, trachea, esophagus, and heart to remove blood and gases.
- Abdominal Cavity: Piercing the stomach, liver, gall bladder, pancreas, spleen, kidneys, and small/large intestines.
- Pelvic Cavity: Piercing the colon, bladder, and uterus/prostate.
Cavity Fluid Injection
Following thorough aspiration, concentrated cavity fluid (typically index 30+) is injected into the cavities.
- Instrumentation: The cavity fluid bottle is connected to a gravity injector, which is attached to the trocar. The bottle is inverted, allowing the fluid to flow by gravity through the trocar.
- Volume: A minimum of 16 ounces of cavity fluid is typically injected into the thoracic cavity, and another 16 ounces is injected into the abdominal/pelvic cavities. For obese or autopsied cases, additional cavity fluid (32–48 ounces total) is recommended.
- Distribution: The embalmer must move the trocar during injection to ensure the fluid is distributed over the visceral organs, rather than pooling in a single spot.
Which pressure type is defined as the difference between the potential pressure and the actual pressure in the embalming machine?
When performing a Restricted Cervical Injection (RCI), what is the correct configuration for the left common carotid artery?
Which trocar guide requires directing the trocar point toward a point one-fourth of the distance from the right anterior superior iliac spine to the pubic symphysis?