Christopher R. Kennedy DVM, Dipl. ACVECC
The intraosseous (IO) compartment provides convenient access to the vascular space. Catheterization is faster1,2 than the jugular venous cut-down technique.3
Indications and patient selection
Intraosseous catheterization can be used when direct intravascular catheterization cannot be achieved in a timely manner or cannot be maintained. Patients in critical condition (e.g., cardiopulmonary arrest, extreme trauma or shock, marked hypothermia) and patients with veins difficult to identify/access (e.g., tissue injury, peripheral edema, thrombosis, obesity or small patients) are candidates for IO catheterization.
Hypodermic needles are suitable for most cats, particularly neonates with softer bone cortices. A bone core may occur during placement, obstructing catheter flow: replacing the catheter using a larger gauge needle overcomes this. Spinal needles have a stylet preventing bone coring. Large, adult cats may be difficult to catheterize with hypodermic or spinal needles: commercially available intraosseous needles are preferable (e.g., JamshidiTM needle, Cardinal Health, Ohio, USA); alternatively, an assistive device may be used.
Assistive devices include the EZ-IO® (Teleflex, Co Westmeath, Ireland), the bone injection gun (B.I.G.) and the NIO® (PerSys Medical, Texas, USA). The EZ-IO® is a battery-powered drill (fig. 92.1); the B.I.G. and NIO® are spring-loaded devices. A feline cadaver study demonstrated faster placement using EZ-IO® versus the B.I.G.1
Sites and site selection
Proposed sites include the proximal humerus, femur, tibia, and the ileal wing.1 The tibial crest is suggested in cats when using needles; the proximal medial tibia when using assistive devices, and the proximal humerus for both modalities. Other considerations influencing site selection include obesity (more complicated at the femoral level), local pathology, and the desired longevity (tibial catheters may dislodge more easily).
Confirmation of placement
Different criteria are suggested to indicate successful placement (table 92.1). Confirmation of placement is best achieved via radiology (fig. 92.2) or by aspirating marrow. Operator perception of success and other criteria are inaccurate (table 92.1).3 Novel confirmation techniques, such as Point-of-Care ultrasonography (POCUS) and pulsatile waveform tracings, have not been evaluated in cats. Figure 92.3 shows an example of proper placement of an intraosseous catheter.
Using an intraosseous catheter
Blood sampling via the catheter is possible. Higher potassium and phosphorous levels, as well as lower glucose and inconsistent calcium measurements, are reported.4,5 Packed cell volumes appear unreliable.5 Hemodynamic instability (shock, cardiopulmonary arrest)6,7 and infusion via the catheter may decrease reliability.
Most intravascular medications can be administered via the intraosseous route (box 92.1), although safety studies have not been performed in cats. Extravasation, that is medications delivered outside the capillaries but within the medullary cavity, occurs necessarily when using this route: hypertonic substances should therefore be used sparingly. Flow rates are affected by the diameter and length of the catheter and the size of the bone. Wider, shorter catheters and bigger bones allow increased flow rates; however, the bone marrow itself may limit achievable rates.8 Tibial flow rates via a 20-gauge 2.5-inch (6.35 cm) needle in puppies averaged 2 mL/kg/min (120 mL/kg/h), i.e., are sufficient for fluid resuscitation.
Catheter care is similar to intravascular catheters. Diluted 2% lidocaine has been suggested for analgesia, although lidocaine in cats should be dosed cautiously: neither efficacy nor safety have been evaluated in cats.9 Questionable catheter function – subcutaneous fluid accumulation, dislodgement, increased resistance, pain – necessitates reconfirmation of placement. Contaminated catheters should be removed.
Contraindications and complications
Fractured bones cannot be used. Compromised soft tissue health is a contraindication unless no better option is available. Repeated catheterizations at the same site should be avoided. Complications occur infrequently (< 1%).10 Dislodgement and leaking around the catheter lead to therapeutic failure. Osteomyelitis, local infection, fat embolism, fracture, nerve injury, and compartment syndrome occur infrequently.10
In box 92.2 there is a recap of the protocol for emergency intraosseous catheter placement in a cat.
1. Bukoski A, Winter M, Bandt C, et al. Comparison of three intraosseous access techniques in cats. J Vet Emerg Crit Care (San Antonio) 20:393-397, 2010.
2. Kennedy CR, Gladden JN, Rozanski EA. Comparison of 3 intraosseous catheter sites and methods of determining placement success in cadaver rabbits. Can J Vet Res 84:33-36, 2020.
3. Allukian AR, Abelson AL, Babyak J, et al. Comparison of time to obtain intraosseous versus jugular venous catheterization on canine cadavers. J Vet Emerg Crit Care (San Antonio) 27:506-511, 2017.
4. Dhein CR, Barbee DD. Use of bone marrow serum for biochemical analysis in healthy cats. J Am Med Assoc 206:487-490, 1995.
5. Ackert L, Boysen SR, Schiller T. A pilot study comparing bone marrow aspirates and venous blood for emergency point-of-care blood parameters in healthy dogs. J Vet Emerg Crit Care (San Antonio) 29:399-304, 2019.
6. Jousi M, Skrifvars M, Nelskylä A, et al. Point-of-care laboratory analyses of intraosseous, arterial and central venous samples during experimental cardiopulmonary resuscitation. Resuscitation 137:124-132, 2019.
7. Strandberg G, Larsson A, Lipcsey M, et al. Comparison of intraosseous, arterial, and venous blood sampling for laboratory analysis in hemorrhagic shock. Clin Lab 65, 2019.
8. Hodge 3rd D, Delgado-Paredes C, Fleisher G. Intraosseous infusion flow rates in hypovolemic “pediatric” dogs. Ann Emerg Med 16:305-307, 1987.
9. O’Brien TQ, Clark-Price SC, Evans EE, et al. Infusion of a lipid emulsion to treat lidocaine intoxication in a cat. J Am Vet Med Assoc 237:1455-1458, 2010.
10. Tyler JA, Perkins Z, De’Ath HD. Intraosseous access in the resuscitation of trauma patients: a literature review. Eur J Trauma Emerg Surg 47:47-55, 2020.
11. Allukian AR, Abelson AL. Intraosseous catheters. In Drobatz KJ, Hopper K, Rozanski EA, Silverstein DC, editors. Textbook of small animal medicine, 2019, Wiley Blackwell, pp 1169-1172.
12. Petitpas F, Guenezan J, Vendeuvre T, et al. Use of intra-osseous access in adults: a systematic review. Crit Care 20:102, 2016.
13. Buck ML, Wiggins BS, Sesler JM. Intraosseous drug administration in children and adults during cardiopulmonary resuscitation. Ann Pharmacother 41:1679-1686, 2020.