ET-16 will deal with Injection Apparatus and Methodology which creates similar intravascular pressure as created by the heart during life to force preservative chemical through the body.
Normal heart action pressure at the aorta is 3 to 5 pounds. With death, heart action ceases and the blood pressure decreases. Embalming must recreate as close to possible intravascular pressures plus. The arch of the aorta becomes the center of the embalming process.
The major concern to the embalmer is the thickening of the blood, development of sludge and/or plugging portions of the capillary network. To overcome the vascular systems deficiency and natural obstructions, it must be rehydrated to establish a pathway for the pre-injection preparatory and preservative chemicals. Following are various methods of injecting into the vascular network.
• Gravity – ½ lb. of pressure per foot above the point of injection
• Gravity and Bulb Syringe Combination – create variable pressures
• Bulb Syringe – variable pressure throughout the process
• Hand Pump – variable pressure throughout process
• Air Pressure – aspirating adaption
• Motorized Centrifugal Force Pump – 3 to 12 psi considering intravascular and extravascular resistance based on embalmer’s/practitioner’s judgment.
• Embalming Machines – wide range of pressures and models
Pressure Terminology
• Potential – The predetermined estimated pressure setting based on the opinion of the embalmer/practitioner on pre-analysis of the body condition. Set with pressure gauge and rate of flow gauge closed
• Actual – The initial reading indicated on the pressure gauge at the time of opening the rate of flow. Indicator needle will drop lower than the predetermined estimated reading.
• Differential – Indicates the difference between the potential and the actual pressure. This indicates the degree of vascular and extravascular resistance.
Pressure is the force to distribute pre-injection and preservative chemicals throughout the vascular network.
Resistance is determined by intravascular and extravascular factors:
Intravascular Extravascular
Congestion Contact Pressure
Clots Ascites
Sludge Visceral Weight
Emboli Gas in Viscera
Bacterial Gas Tumors
Rigor Mortis
Post-Mortem Stain (hematin)
Decomposition
Rate of Flow – amount of embalming solution injected over a specific time period. This is determined through pre-analysis of the overall condition of the body. It is to achieve a uniform distribution without distention or swelling. High rate of flow can create swelling.
Time (minutes) Ounces per minute
5 25.6
6 21.3
7 18.2
8 16.0
9 14.2
10 12.8*
11 11.6*
12 10.5*
13 9.8*
14 9.1*
15 8.5*
16 8.0*
17 7.5*
18 7.1*
19 6.7
20 6.4
*Recommended period of time in ounces. Variable latitude for embalmer/practitioner
Methodology
• Calculate percentage according to pre-analysis of the individual body.
• Determine injection pressure
• Primary Dilution - mix concentrated arterial fluid in embalming machine tank
• Potential pressure – initial injection
• Actual pressure – mixture of fluid with body fluids
• Secondary dilution – stabilized injection within the body
• Differential pressure – Mixture of fluid with abnormal amounts (anasarca) Tertiary dilution
An early preservative criterion of 1 gallon to 50 pounds of body weight was a rule of thumb. This was based on 40% formaldehyde to 60% water concentrate of pure formalin (100%). Modern formulations of embalming chemicals do not meet the same criteria.
A modern specially formulated 30 index arterial fluid used to inactivate a 150 pound body would require 56 ounces of concentrate if it was all retained in the tissue. This equals 3.35 bottles of concentrated fluid. Continuous injection and drainage which is a common practice would not meet the preservation requirements.
Next month’s article, ET-17 will cover Preparation of the Vascular System and Cavity Embalming.