Generalised oedema, ascites and a 36-hour viewing deadline
A 74-year-old woman died in a nursing home and was refrigerated at 4 °C within two hours; she is now four days post-mortem. Her history includes chronic heart failure and nephrotic syndrome. On admission to the preparation room she has marked pitting oedema to mid-thigh, a grossly distended abdomen with a fluid thrill, and taut, shiny skin over both legs. Her recorded weight is 18 kg above her last documented dry weight. The family have asked for an open-casket viewing in 36 hours and a full burial. The preparation room is at 20 °C. You have a gravity-fed injection set, a centrifugal pump, a trocar and standard drainage equipment.
1. Explain why generalised oedema alters both arterial injection and venous drainage in this body, and describe what you would expect to see at the drainage point.
Read the worked answer
Mechanism. Oedema is an expansion of the interstitial compartment. Raised interstitial hydrostatic pressure and reduced plasma oncotic pressure (nephrotic syndrome) both push fluid out of the capillaries, and the same interstitial pressure compresses the thin-walled venules and lymphatics. So two things happen at once:
- Arterial side: capillaries and small vessels are splinted and compressed by surrounding fluid, so resistance to flow rises. Fluid also tracks into tissue planes outside the vascular tree, so a proportion of what you inject is 'lost' to the interstitium rather than perfusing tissue.
- Venous side: low-pressure veins are the first to be occluded. Drainage depends on a patent venous route and on the injected volume displacing fluid back into it; when veins are collapsed, drainage is sluggish even though the body is waterlogged.
What I would expect at the drain. Initially little or nothing, then a copious watery, serous, pale drainage once the vascular tree opens and interstitial fluid is mobilised. I would not read early poor drainage as 'no drainage route'.
Consequence for planning. Fluid demand will be high, fixation will be diluted by tissue fluid, and there is a real risk of over-distension and skin rupture if I try to force the issue with pressure. The answer is volume, time and drainage, not force.
2. Set out your injection and drainage plan: site selection, fluid choice, pressure and rate, and how you will judge when to stop.
Read the worked answer
Site. A single femoral injection on the less oedematous side, with the femoral vein used for drainage, gives the shortest route to the trunk and avoids loading the head and neck early. If the legs are too waterlogged to cannulate, I would use the right common carotid for the head only and the femoral or external iliac for the trunk - a split or restricted injection rather than one point trying to do everything.
Fluid. A moderate-to-strong solution, in the region of a 2% formaldehyde index, with a co-injection of a good diffusing and draining agent. I would avoid humectants: this body has too much water already. Dye helps me see how far I have got, since colour change alone is unreliable in oedematous tissue.
Pressure and rate. Low and slow - around 1–1.5 psi (roughly 50–75 mmHg), which is at the bottom of the normal range. Slow injection allows time for interstitial fluid to move back into the venous side; high pressure in oedematous tissue causes extravasation and blistering rather than distribution.
Drainage. Continuous, aided by elevation of the limb, light massage from distal to proximal, and intermittent closure of the drain to let pressure build and then release. I would plan a second drainage point (e.g. jugular) if the trunk remains firm-but-wet.
Stopping point. Not colour. I would judge by firmness and loss of pitting across the trunk and limbs, the volume and character of drainage, and the return of the skin from a pressed thumbprint. If firmness plateaus while drainage is still pouring, I stop and reassess rather than add more volume.
3. How will you manage the ascitic abdomen before, during and after arterial injection?
Read the worked answer
Before. The ascites is compressing the inferior vena cava and the abdominal viscera, which is one reason drainage from a femoral point may be poor. Aspirating the peritoneal cavity with a trocar before injection relieves that pressure and improves venous return from the legs. I would do it slowly, with the trocar directed away from the aorta and liver, and I would measure and record the volume.
During. Relieving the pressure first means I can then inject at a lower pressure and get better distribution to the abdominal wall and viscera. I would not aspirate again mid-injection unless the abdomen re-tenses, because re-entering a distended, fluid-filled abdomen while the vascular tree is pressurised risks puncturing a vessel and losing fluid into the cavity.
After. Once arterial injection is complete, I re-aspirate any residual fluid, then instil cavity fluid to fix the viscera and the parietal peritoneum. The puncture site needs careful sealing - a small aperture, dried margins and a suitable sealant - because a leaking trocar site in an oedematous, ascitic body will stain the clothing and is very difficult to correct later.
Cosmetic consequence. Removing the fluid will leave loose, redundant abdominal skin. That is manageable with packing and positioning; leaving the fluid in is not, because it will continue to leak and distort the viewing. I would also warn the family that the abdominal contour will change and that a tightly fitted garment will show it.