Arterial Catheterization

Chapter 49 Arterial Catheterization

Elisa M. Mazzaferro, MS, DVM, PhD, DACVECC

• Arterial catheters can be placed in the dorsopedal, radial, femoral, coccygeal, and auricular arteries.

• Arterial catheters can be used for direct blood pressure monitoring and procurement of arterial blood samples for blood gas and other analyses.

• Arterial catheters are generally well tolerated, but they can become dislodged easily with excessive patient movement.

• Arterial catheters should be avoided in patients with severe coagulation abnormalities whenever possible because of the risk of arterial hemorrhage.

• Arterial catheters are not well tolerated in cats and should be kept in place no longer than 6 to 8 hours.

• All arterial catheters should be labeled “Arterial Catheter—Not for IV Infusion” to prevent inadvertent injection of fluids or drugs into the arterial line.

INTRODUCTION AND INDICATIONS FOR ARTERIAL CATHETERIZATION

An indwelling arterial catheter is a necessary and useful procedure for many critically ill veterinary patients. Arterial catheters can be used to collect arterial blood samples when measuring an animal’s arterial oxygenation and ventilation and for invasive direct arterial blood pressure monitoring. To avoid complications associated with hemorrhage or arterial thrombosis, the animal’s coagulation status should be checked before considering placement of a catheter in any artery. Ideally, a platelet count or estimate, activated partial thromboplastin time, and prothrombin time should be evaluated before catheter placement. If severe thrombocytopenia (<50,000 platelets/μl) or prolonged activated partial thromboplastin time and prothrombin time are present, the patient may be at risk for hemorrhage from the site of arterial catheterization.

Arterial catheters are placed most frequently in the dorsopedal artery.¹ This location is technically the simplest, and it enables easy hemostasis. Alternative locations for arterial catheter placement include the auricular artery on the dorsal surface of the ear pinna,² and the femoral, coccygeal, radial, and brachial arteries.³ With practice, arterial catheterization and maintenance is not technically difficult and can provide information that helps guide lifesaving therapeutic interventions in the most critically ill veterinary patients.³

PATIENT PREPARATION

A patient’s coagulation status should be considered carefully before arterial catheter placement. If a coagulopathy is not found or suspected, the site should be chosen based upon the patient’s anatomy and consideration of underlying diseases, such as vomiting, diarrhea, pyoderma, or aural hematomas. For example, a radial arterial catheter may be inappropriate in a vomiting patient because of the risk of contamination. Similarly, femoral, coccygeal, or dorsopedal placement may be inappropriate in a patient with severe diarrhea. Patients with aural hematomas frequently shake their heads, and thus can easily dislodge an auricular arterial catheter, even when placed in a healthy ear. Because of the increased risks of auricular, coccygeal, and radial catheter dislodgement in ambulatory patients, dorsopedal catheters are preferred whenever possible.¹

PERCUTANEOUS ARTERIAL CATHETER PLACEMENT

Once the proposed site of arterial catheterization has been chosen, the operator should become familiar with the animal’s anatomy, palpating over the artery as it courses along the leg, tail, or ear while simultaneously feeling carefully for the arterial pulse. The designated site of catheterization should be clipped, then scrubbed aseptically with antimicrobial soap. The operator should perform careful hand washing and wear gloves to maintain aseptic technique during the procedure.

Percutaneous Dorsopedal Artery Catheterization

For dorsopedal artery placement, the patient should be positioned in lateral recumbency, and the leg with the proposed catheter site located down, adjacent to the table. The furshould be shaved on the anteromedial portion of the limb from the level of the tarsus distally along the length of the metatarsal bones. The artery usually is palpable just distal to the hock, between the second and third metatarsal bones.¹ Once the artery has been palpated and the site clipped and aseptically prepared, a 20- to 24-gauge over-the-needle catheter can be placed percutaneously or via percutaneous facilitation technique.

Percutaneous facilitation refers to the practice of making a small nick in the skin using the bevel of a 20-gauge needle. Use care to not penetrate the artery during this process because arterial spasm is common, and prevent cannulation until a palpable pulse returns. Whether the over-the-needle catheter is placed directly through the skin or through a nick incision formed by percutaneous facilitation, the needle and catheter should be inserted through the skin at a 15-degree to 30-degree angle over the palpable pulse.¹ The needle and catheter should be directed dorsally and laterally to the metatarsals over the site of a palpable pulse in small maneuvers, watching for a flash of blood in the catheter hub. Once a flash of blood is observed, the catheter should be pushed off of the stylet into the artery. Pulsatile arterial blood should be observed as soon as the stylet is withdrawn from the arterial catheter, if it is placed correctly.¹ Vasospasm may preclude further advancement in very small animals or cats, in which case a drop of papaverine hydrochloride can be flushed into the catheter to cause local vasodilation. If the catheter snags or does not feed easily, it can be pulled gently over the stylet and another attempt at catheterization performed (being careful not to pierce the catheter with the stylet).

In some cases when the original attempt catheterizes a vein, the catheter can be left in its original place and a second attempt performed proximally, if an arterial pulse is still palpable (Color Plate 49-1). Leaving the original catheter in place prevents hematoma formation that may preclude catheterization. Should all attempts at arterial catheterization fail, a pressure bandage should be placed for a minimum of 15 minutes to prevent hemorrhage and hematoma formation.¹

Once the dorsopedal arterial catheter is in place, it should be flushed and secured as indicated in Box 49-1.

Tags: Small Animal Critical Care Medicine

Sep 10, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access