Harkness (1993), Jenkins (2000), Harkness et al. (2010).
| Species | 20% of blood volume (ml) |
|---|---|
| Gerbil | 1.2 |
| Hamster | 1.4 |
| Rat | 4.0 |
| Guinea pig | 4.5 |
Twenty percent of the approximate blood volume of rodents.
Sterile CTAs are useful for atraumatic tissue dissection and manipulation. They can be used to apply pressure to damaged vessels allowing a clot to form. Use moistened CTAs when using them for tissue manipulation and dissection and dry ones to absorb fluids.
Absorbable gelatin sponge is made from treated purified gelatin solution. It is capable of absorbing many times its weight in blood and also provides a scaffolding for clot formation. It is completely absorbed in 4–6 weeks. Surgicel (Ethicon, Inc., Sommerville, NJ) is oxidized regenerated cellulose resembling cloth. It is a hemostatic aid that adheres nicely to moist tissues, but is not capable of absorbing much fluid and does not adhere well to dry tissue. Gelatin sponges are thick and absorb more fluid than oxidized regenerated cellulose but are prone to becoming dislodged from the tissue.
Topical thrombin is commercially available and when applied uses the patient's fibrinogen to form a fibrin clot. It is most useful for oozing and minor bleeding from capillaries and venules where standard surgical techniques are ineffective at halting the hemorrhage. It can be applied directly to the source of hemorrhage or can be applied onto gelatin sponge that is then placed over the site of hemorrhage. A hemostatic “taco” can be made of gelatin sponge wrapped in oxidized regenerated cellulose and soaked in topical thrombin and is very effective for controlling hemorrhage (Figure 1.4).
Electronic Hemostatic Devices
Electrocautery
Electrocautery uses direct current electricity to heat metal until it is red hot. The red hot tip is applied to the source of hemorrhage to heat and coagulate tissues. Electrocautery causes heat damage to adjacent tissues that then undergo necrosis minimizing its value in many situations. Cautery pens (Convenient Cautery Kit; Jorgensen Labs; www.jorvet.com) may be useful to cauterize small vessels in small exotic mammals if electrosurgery is not available. They have a fine wire tip and are battery‐operated. Keep in mind that the longer the heat is applied to the tissue, the more thermal necrosis occurs.
Figure 1.3 Straight and right‐angled hemostatic clip appliers are available. Compared with the standard applier (a), the right‐angled appliers (b) can be inserted into a small body cavity to place a hemostatic clip at nearly a right angle, while the standard applier requires the handles to be almost perpendicular to the vessel, making it difficult to place through a small approach into a body cavity.
Figure 1.4 A “hemostatic taco” made of gelatin sponge (G) wrapped in oxidized, regenerated cellulose (S) and soaked in topical thrombin has been applied to the caudal vena cava (arrow) after right adrenalectomy.
Electrosurgery
Electrosurgery uses high‐frequency alternating current to generate energy. There is an active electrode and an indifferent electrode or ground. With monopolar electrosurgery the current exits the generator, passes to the active electrode, and concentrates at the tip which contacts the patient. After creating a thermal event at the tip, the current disperses throughout the patient's body, exits through the ground plate, and is carried back to the generator to complete the electrical circuit. Therefore, the patient is within the electrical circuit. If the ground plate only contacts a small area of the patient’s skin burns and subsequent necrosis can result because the current concentrates where it exits the patient. The Surgitron® Dual Frequency 120 (Ellman International, Inc., Hewlett, NY) generates 4.0 MHz current which is in the radio frequency wavelength. Current is received by the indifferent electrode acting as an antenna. Because the current is in the radio frequency, the area of contact between the patient and the ground plate is irrelevant and thermal injury should not occur. This is helpful with small patients where it might be difficult to disperse the current exiting the patient adequately.
The bipolar electrosurgical forceps are primarily used for hemostasis, but can also be used for tissue dissection resulting in minimal hemorrhage. The same generator is used, but the patient is not within the electrical circuit so the current only affects tissue within the tips of the forceps. Bipolar forceps are most useful near structures that would be adversely affected by the current such as the heart, brain, spinal cord, etc., or for hemostasis deep within body cavities. When using bipolar to dissect or cut tissue, grasp the tissue in the forceps and activate the current while pulling the forceps. The tissue within the tips will be affected by the current providing hemostasis for small vessels within the tissue grasped. In birds, this technique is useful for making a skin incision. Grasp the skin with the forceps and activate the current to create a small defect in the skin. Then insert one limb of the forceps under the skin for 1–2 cm, oppose the other limb of the forceps, activate the current, and withdraw the forceps, thus cutting the skin. Bipolar mode is available on most electrosurgical units including the Surgitron®.
Vessel Sealing Devices
LigaSure™ (Medtronic, Minneaplis, MN) is a vessel/tissue sealing system that is commonly used in veterinary surgery. The ForceTriad™ (Medtronics, Minneapolis, MN) combines the LigaSure technology with monopolar and bipolar electrosurgery. While the specific technology is proprietary, LigaSureTM is a type of bipolar electrosurgery. The generator senses the electrical impedance of the tissues within the tips and delivers the amount of current needed to melt the elastin and collagen; it then allows the elastin and collagen to re‐form, creating a permanent seal in a single application. It generates less than 1 mm of heat lateral to the seal and is Food and Drug Administration (FDA)‐approved to seal vessels up to 7 mm diameter. A wide range of handpieces are available for open surgical procedures and for minimally invasive surgeries.
Harmonic Scalpel
Ethicon® Harmonic Scalpel (Ethicon US, LLC, www.ethicon.com/na) is an ultrasonically activated cutting instrument that converts electrical energy to mechanical energy. The blade vibrates at 55,500 Hz creating heat that coagulates vessels and cuts tissue. Hand pieces are available in various sizes and types for both open surgical procedures and minimally invasive surgery. It is FDA‐approved to seal vessels up to 5 mm diameter and does not create smoke. The
