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Blood collection and administration of fluids and drugs (Guinea Pig)Blood collection and administration of fluids and drugs (Guinea Pig):Administration of Fluids and Drugs (Overview):Gastro-Intestinal Tract:Parenteral Administration
Blood Collection:
Administration of Fluids and Drugs (Overview):When drugs, vaccines, injectable anesthetics or other agents are to be administered, one of several different routes may be selected. The route is governed by the nature of the agent being administered, the animal, and the purpose of the administration, among other factors. Gastro-Intestinal Tract:Oral: Substances may be administered orally by addition to the food or the drinking water. The amount of drug consumed by an animal will vary between each individual. If the drug imparts an unpleasant taste, affecting palatability, the drug will be consumed in decreased amounts. Also, environmental conditions such as the ambient temperature will also affect both water and food consumption. The general rule of thumb is that 6 grams of food and 10 mls of water will be consumed daily per 100 grams of body weight5. Often syringe administration of a substance directly into the oral cavity is a successful technique and should be attempted before utilizing gavage. Gavage: If it is necessary to administer exact amounts of a substance gastric feeding needles can be used. This procedure is stressful to guinea pigs and it is recommended that sedatives be administered prior to gavage. Also, the soft palate of Guinea pigs is continuous with the base of the tongue and provides only a small opening in which to pass a tube or feeding needle. Trauma will result if meticulous care is not taken. Feeding needles with a ball tip helps prevent introduction of the needle into the trachea and prevents trauma to the oral cavity (future picture). Flexible or plastic tubes may be bitten or chewed and therefore require a mouth gag if they are to be used. Feeding needles are inserted through the mouth into the stomach or lower esophagus. Placing the needle next to the guinea pig so that the end of the needle is adjacent to the last rib and marking the position on the needle that is adjacent to the tip of the nose will determine the distance the feeding needle should be advanced into the oral cavity to insure administration of the compound into the stomach (future picture). Care must be taken that the tube or needle does not enter the trachea or puncture the esophagus or stomach, therefore knowledge of the oropharyngeal anatomy is necessary. In most cases, introduction of the tube toward the rear of the mouth will induce swallowing and the tube will readily enter the esophagus. A violent reaction (coughing, gasping) usually follows accidental introduction of the tube into the larynx or trachea. With the sedated guinea pig restrained in one hand the the feeding needle is introduced in the space between the incisors and the beginning of the molars (diastema)(future picture). If introduced from the left diastema the needle should be directed caudally toward the right ramus of the mandible. As the needle approaches the pharynx the mouse will usually swallow allowing introduction into the esophagus. Using the feeding needle to gently extend the neck facilitates introduction into the stomach. With a stomach tube fitted to a syringe or aspirator, materials may be administered or withdrawn as required. Parenteral Administration: General Considerations
General Considerations: Parenteral routes of administration involve injections into various compartments of the body. Sites used for collection of blood from veins may also be used for intravenous administration. Intraperitoneal administration is one of the most frequently-used parenteral routes in rodents. Other locations are the musculature and subcutis. Materials given intramuscularly must be in very small volumes and is generally not recommended unless necessary. Absorption by this route is more rapid than from subcutaneous administration. Regardless of the route used, it is essential that the subject be securely restrained to prevent unnecessary struggling by the animal and to avoid injury to personnel by dislodged needles. The investigator should know the physiological and chemical properties of the substance that he/she plans to inject. Considerable tissue damage and discomfort can be caused by irritating vehicles, drugs or solutions when injected into animals. The use of the foot pad as an injection site for antigens with or without adjuvant is discouraged since it is a needless and painful procedure. More suitable sites for antigen injections are subcutaneously in the axilla or lateral thoracic wall, deep in large muscle masses, or into the popliteal lymph node. Demonstration/instruction sessions can be arranged with the ACU. Site Preparation:The area of injection or incision should be cleaned with alcohol or other suitable disinfectant. Some procedures will require sedation or anesthesia; others may be carried out without anesthesia provided suitable restraint is used. In order to better visualize veins dilation can be accomplished warming the animal with a low-wattage light bulb for 5 to 15 minutes prior to venipuncture. This also aids by providing additional light. Intravenous:Equipment: 27 to 30 g, 1-inch needle. Volume: 0.5 ml in an adult guinea pig. Several veins are used, but there is considerable variation among individual animals in their size and usefulness. Among the veins used are the lateral saphenous and cephalic veins (in which a 27 g needle is used), and the marginal ear vein which may be used with a very small (30 g) needle if the ear is not pigmented. Chronic indwelling catheters may be surgically placed in the jugular vein. Intraperitoneal:Equipment: 19 to 22 g needle with appropriate size syringe; restraining board if working alone. Volume: 10-15 ml in an adult guinea pig. Light anesthesia is recommended. Injections are made in the lower abdominal quadrant, off the midline, taking care to avoid the urinary bladder, bowel and liver. Aspirate before injection to insure proper placement. If clear/yellow (urine) or brown/green (intestinal contents) fluid is obtained the needle is improperly positioned and contamination of the needle, syringe and contents has occurred. discard the needle, syringe and contents and start over. Subcutaneous:Equipment: 20 to 22 g, 3/4 to 1-inch needles with appropriate size syringe. The skin of the guinea pig is thick and tough, especially over the shoulders. The use of short, heavy gauge needles are recommended, e.g. 20 g, 1-inch. Good restraint is necessary to avoid injury. Intramuscular:Equipment: 20 to 22 g, 1-inch needles with a 1 to 5 ml syringe. Volume: 0.3 ml in an adult guinea pig. Intramuscular injections are not frequently used; however, if care is taken not to injure adjacent structures, injections can be made into the lower back (lumbar) muscles and caudal muscles of the thigh and the quadriceps. The lower back muscles should be used to avoid self-induced foot trauma that may result from ischiatic nerve irritation from injection of the thigh muscles. Aspirate before injection to insure proper needle placement. If blood is obtained upon aspiration partially withdraw the needled to a subcutaneous position and redirect the needle into the muscle. An assistant is usually needed. Blood CollectionThe amount of blood needed and other factors will govern the method and sites of collection. Descriptions of the various techniques for venipuncture in different species is available in the Office of Animal Resources (400 ML; 335-7985) in text and videotape format. Proper insertion of the needle into a vein or other part of the vascular system is normally the most difficult part of the procedure. Certain guidelines can be given, but only practice provides proficiency. Veins may be expected to roll, collapse, or shift, making entrance difficult. A precise, careful introduction of the needle is best and several attempts may be required. Starting at distal sites will allow repeat attempts more proximally. The needle is inserted parallel to the vein and the tip directed into the lumen along the longitudinal axis. When withdrawing blood from a vein, aspiration should be slow so the vessel does not collapse. Site Preparation:The area of injection or incision should be cleaned with alcohol or other suitable disinfectant. Some procedures will require sedation or anesthesia; others may be carried out without anesthesia provided suitable restraint is used. In order to better visualize veins dilation can be accomplished warming the animal with a low-wattage light bulb for 5 to 15 minutes prior to venipuncture. This also aids by providing additional light. Lateral saphenous vein venipuncture in guinea pigs:Equipment: 22 gauge needle or scapel blade A small amount of blood can be obtained by puncturing the lateral saphenous vein while applying pressure in the thigh region to create venous stasis. Blood which pools at the site can be collected utilizing a capillary tube. Apply pressure to the site after blood collection to enhance hemostasis. Lateral saphenous vein (vacuum assisted): A larger amount of blood can be obtained by using a vacuum device to prolong blood flow. Equipment:
Technique:
Toe clipping to obtain blood samples: Clipping toes is an unacceptable method of blood collection. Tail clipping is not a preferable method for blood collection. Cranial vena cava:Equipment: 22-23 gauge needle; 3-6 cc syringe The cranial vena cava is an acceptable site to repetitively collect more than a one milliliter of blood. Animals must be anesthetized and restrained in dorsal recumbency. The manubrium of the sternum is palpated and needle is inserted lateral to the manubrium under the first right rib at a 30 to 35 degree angle to the horizontal axis of the animal. Insert the needle one-half inch, apply slight negative pressure and slowly withdraw until blood flows. If not blood is obtained, withdraw the needle and start over. Do not try to reposition the needle while inserted to avoid laceration of vessels and other vital structures. Blood should be withdrawn slowly, and the amount must be limited (up to 7 ml/kg in an adult guinea pig) unless euthanasia is planned. Cardiac puncture:Equipment: 20-22 gauge needle; 12-20 cc syringe Cardiac puncture represents an accepted method of blood collection from guineas when more than a few drops are required. However, this method also carries considerable risk to the animal and occasionally deaths occur. It is not recommended as a repetitive blood sampling procedure. Animals must be anesthetized and restrained in dorsal recumbency. The needle is inserted under the xyphoid cartilage slightly to the left of midline. The needle is advanced at a 20 to 30 degree angle from the horizontal axis to the sternum to enter the heart. Aspirate lightly while advancing. Blood should be withdrawn slowly, and the amount must be limited (up to 7 ml/kg in an adult guinea pig) unless euthanasia is planned. |
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