Loss of endothelium mediated vascular relaxation as a response to various clamping pressures. Part II. Direct measurements of clamping pressures and scanning electron microscope study.
BACKGROUND
We used novel equipment for measuring the direct tip pressure (P) of a clamp arm on the vessel wall and studied the relationship between endothelial injuries and various clamping pressures.


METHODS
A strain gauge was applied to the surgical clamp arm and connected via amplifier to a 12-bit analogue-digital converter on a PC--MSDOS computer. In the on-line in vivo measurements on rat thoracic aorta a momentary peak clamping pressure (MPCP) as well as the lower stationary clamping pressure (SCP) was defined. Clamping forces of two clamps commonly used in cardiovascular microsurgery were tested in the experiment on rat thoracic aortas: clamp A had the tip pressure p = 0.60 N/mm2 and clamp B p = 5.16 N/mm2. After 15 minutes of occlusion, the thoracic aorta was excised and scanning electron microscopy studies for aortas clamped with clamp A and clamp B were performed.


RESULTS
Great endothelial lacerations with complete disruption of the endothelial layer in the rings clamped with the clamp B were seen, but no disruption in rings clamped with clamp A.


CONCLUSIONS
The clamping vessel wall injuries, particularly in endothelial layers, depend on the momentary peak clamping pressure as well on the lower stationary clamping pressure.
Gersak
B
B
Department of Cardiovascular Surgery, Medical Center Ljubljana, Slovenia.
Trobec
R
R
Psenicnik
M
M
D000818:Animals; D001013:Aorta, Thoracic / Q000293:injuries / Q000502:physiology / Q000648:ultrastructure; D003250:Constriction; D004730:Endothelium, Vascular / Q000293:injuries / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009126:Muscle Relaxation / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology* / Q000648:ultrastructure; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D013525:Surgical Instruments