480
EQUINE VETERINARY JOURNAL
Equine vet. J . (1992) 24 ( 6 )480-481
Short Communications Catheterisation of carotid artery in horses using ultrasonography J. D. HARKINS, L. MITCHELL, R. P. HACKETT and N. G. DUCHARME Department of Clinical Sciences, Veterinary Medical Teaching Hospital, New York College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Introduction Arterial blood samples are often obtained during slllgery and exercise physiology studies to measure arterial blood pressure and blood-gas concentrations (Kelso et a1 1987; Wagner 1991; Harkins et al 1992b).The most commonly catheterised arteries are the facial, accessible along the cranial border of the masseter muscle, and the dorsal metatarsal on the lateral aspect of the hind limb (Wagner 1991). During exercise, arterial blood samples are obtained most frequently by catheterising the facial, transverse facial (Harkins et al 1992b) or carotid arteries, (Bayly et al 1983; Wagner er al 1989). Because the catheter is inserted in sensitive portions of the face, catheterisation of the facial and transverse facial arteries requires some co-operation from the horse. Furthermore, only small-gauge catheters (20-gauge) can be used in some horses with smaller arteries. Resulting complications include restricted blood flow and clotting of the catheter. Removal of the catheter frequently causes formation of at least a small haematoma, which impedes recatheterisation of the artery for several days. In studies using the carotid artery for blood sample collection, frequently one or both arteries are translocated to a subcutaneous position to facilitate catheterisation. The original translocation surgery (Tabemor 1969) was modified subsequently (Harkins et a1 1992a). Disadvantages of this procedure are: 1) expense of surgery and anaesthesia; 2) occasional complications from surgery; 3) a recovery period of 2-3 weeks when the carotid artery cannot be catheterised. Further, it is impractical to translocate the carotid artery of client-owned animals or horses that are tested only a few times. This paper describes a method for catheterising the carotid artery of horses using ultrasonography. The procedure requires no tranquillisation or surgery and minimal co-operation from the horses. Materials and methods Horses Six client-owned Thoroughbred racehorses ranging in age from 2 to 5 years and weighing 456-520 kg (489 & 16.7 kg) were used in studies requiring arterial blood-gas samples to evaluate the effects of various experimental factors on oxygen (02)and carbon dioxide (COz) concentrations. Catheterisation technique The hair over the jugular groove was clipped and the skin scrubbed with an antiseptic solution (Betadine Surgical Scrub,
Purdue Frederick Co., Norwalk, CT, USA). A generous amount of alcohol was applied to the skin as a transmission medium instead of ultrasonic coupling gel. A 7.5 MHz linear probe of the ultrasound unit (Aloka SOOV, Aloka Co. Ltd., Tokyo, Japan) was placed transversely on the neck to visualise a cross-sectional area of the jugular groove. Blood vessels are seen as anechoic circular images (Figs 1-3). The location of the vessels of the neck varies slightly between horses, but the carotid artery is 1-3 crn below the skin and deep to the jugular vein. On ultrasonography, the carotid artery is more circular and less collapsible than the vein. Also, the shape of the artery is consistent, whereas the more compliant vein may collapse from pressure of the ultrasound probe or distend if occluded below the level of imaging. The artery is usually directly under the vein in the cranial and middle parts of the neck which increases the difficulty of arterial catheterisation. Our experience suggests that the right carotid artery is easier to catheterise than the left because the right jugular vein and carotid artery diverge in the caudal portion of the neck. The artery usually deviates slightly lateral to the vein, although the artery of one horse deviated medially. In either case, the carotid artery can be entered without penetrating the jugular vein. The ultrasound probe is positioned so that the carotid artery is in the middle of the screen (Fig I). The skin is anaesthetised with 1 ml lignocaine (Lidocaine HCI-2%: Pan Vet, Inc., Springfield, MO, USA). A 16-gauge, 5.25-inch (1.7 mm x 13.3 cm) intraarterial catheter (Angiocath, Becton Dickinson Deseret Medical, Sandy, UT, USA) is inserted through the skin and a lignocaine bleb deposited at a 90' angle to the skin. The catheter can not be seen on the screen, but gentle pressure on the stilette and catheter disrupts the tissue directly in line with them, and the intended line of movement of the advancing catheter is visualised easily (Fig 3). The catheter is aimed towards the centre of the artery by redirecting the line of tissue displacement. When the catheter reaches the outside of the arterial wall, moderate pressure on the stilette forces the catheter into the lumen and arterial blood appears in the catheter. The catheter is sutured to the skin to secure it during experimentation. Results and discussion Figures 1-3 are thermal prints of the ultrasound screen. Figure 1 is a mid-cervical view of the jugular groove vessels showing the carotid artery directly below the vein. In Figure 2 the carotid artery is still deep but lateral to the jugular vein, allowing the artery to be entered without penetrating the vein. The tracheal
48 I
EQUINE VETERINARY JOURNAL
3: Verrical line of r i m e disruption Fig
the from carheter movement above the carotid artery ( a ) (hetufeen
Fig I : A midcervical view of the carotid artery ( a ) a n d j u g u l a r vein (v)
arrowi
following day. The catheter was flushed with heparinised saline then filled with heparin (1:lOOO) every 4 h to maintain patency. Blood was always aspirated into the syringe before injecting the heparinised saline to clear heparin from the tubing and prevent the introduction of a clot into the arterial circulation. Rarely, a clot would form in the catheter preventing further use of the catheter in subsequent experiments. The catheter remained in the artery a maximum of 30 h. There were no apparent complications from nerve damage, infection, or embolus formation.
Conclusion Ultrasonography can be used to catheterise the carotid artery as an alternative method for arterial blood collection. No complications from infection, emboli formation, or perceptible nerve damage was evident in 6 horses in which laryngeal function remained normal.
Acknowledgements rings are visible on the right side of the print. Figure 3, also a view of the caudal cervical area seen in Figure 2, is of the arterial catheter which has penetrated the skin and subcutaneous tissue. Gentle pressure is being applied to the stilette to disrupt the underlying tissue. Note the line of tissue disruption directly above the carotid artery. Because the video screen displays movement and not a still image, this phenomenon is visualised easily with the ultrasound screen. One concern associated with blood collection from the carotid artery is possible damage to the recurrent laryngeal nerves. The recurrent laryngeal, vagus, and sympathetic trunk nerves lie in close association with the carotid artery. These nerves are not visualised with ultrasound, and damage to the recurrent laryngeal nerve, via puncture or entrapment from scar tissue formation, can result in laryngeal paralysis (Derksen 1991). Each carotid artery of the 6 horses used in this study was catheterised '2-8 times within a 4-week period for different experimental procedures. Occasionally, the same artery was catheterised on consecutive days. However, there was usually an interval of 2-4 days between catheterisation of the same artery. At the end of the 4-week period, the larynxes were visualised by a flexible videoendoscope (Welch-Allyn Corp, Skaneateles Falls, NY, USA), and no perceptible nerve damage was evident since laryngeal function remained normal. Rose and Rossdale ( I 98 1) collected blood from the carotid artery over 200 times with no apparent complications. To minimise the number of times the carotid artery was traumatised from catheterisation in our studies, experimental procedures for the same horse were frequently scheduled on consecutive days. After completing one experimental procedure, the catheter was left in the artery overnight and used again the
These studies were supported by grants from the Horsemen's Benevolent and Protective Association (NY Division) and the Harry M. Zweig Memorial Fund for Equine Research.
References Bayly, W.M., Grant, B.D., Breeze, R.G. and Kramer. J.W. (1983) The effects of maximal exercise on acid-base balance and arterial blood gas tension in Thoroughbred horses. In: Equine Physiology, Eds: D. H. Snow, S. G. B. Persson and R. J. Rose. Granta Editions, Cambridge, UK. pp 400-415. Derksen. EJ. (1991) Diseases of the respiratory system. In: Equine Medicine and Sirrqery. 4th edn. Eds: P. T. Colahan. I. G . Mayhew. A. M. Merritt and J. N. Moore. American Veterinary Publications Inc.. Goleta, CA. pp 414-417. Harkins, J.D.. Rehder, R.S.. Hackett. R.P. and Ducharme, N.G. (1992a) Development of a nondisruptive face mask for measurement of respiratory airflow in exercising horses. J. appl. Physiol. (in press) Harkins. J.D., Beadle, R.E. and Kamerling, S.G. (1992b) The correlation of run times and physiological variables in Thoroughbreds. Equine vet. J. 24 (In Press) Kelso, T.B.. Hodgson. D.R.. Witt. E.H. and Bayly. W.M. (1987) Bicarbonate administration and muscle metabolism during high-intensity exercise. In: Equine Exercise Physiology I / . Eds: J. R. Gillespie and N. E. Robinson. KEEP. Davis, CA. pp 438-447. Rose, R.J. and Rossdale, P.D. ( 198 I)Techniques and clinical application of arterial blood collection in the horse. Equine wr. J. 13. 70-73. Tavernor, W.D. (1969) Technique for the subcutaneous relocation of the common carotid artery in the horse. Am. J. ref. Res. 30, 1881-1883. Wagner, A.E. (1991) Venous and arterial catheterization and fluid therapy. In: Equine Anesfhesia. Eds: W. W. Muir and J. A. Hubbell. Mosby-Year Book Inc.. St. Louis. MO. pp 140-145. Wagner. P.D.. Gillespie, J.R., Landgren, G.L.. Fedde. M.R.. Jones, B.W.. DeBowes, R.M., Pieschl. R.L. and Erickson, H.HJ. ( 1989) Mechanism of exercise-induced hypoxemia in horses. J. oppl. Physiol. 66, 1227-1233.
Received for pub,licution: 4.2.92 Accented: 11.4.92
EQUINE VETERINARY JOURNAL
Equine vet. J . (1992) 24 ( 6 )480-481
Short Communications Catheterisation of carotid artery in horses using ultrasonography J. D. HARKINS, L. MITCHELL, R. P. HACKETT and N. G. DUCHARME Department of Clinical Sciences, Veterinary Medical Teaching Hospital, New York College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Introduction Arterial blood samples are often obtained during slllgery and exercise physiology studies to measure arterial blood pressure and blood-gas concentrations (Kelso et a1 1987; Wagner 1991; Harkins et al 1992b).The most commonly catheterised arteries are the facial, accessible along the cranial border of the masseter muscle, and the dorsal metatarsal on the lateral aspect of the hind limb (Wagner 1991). During exercise, arterial blood samples are obtained most frequently by catheterising the facial, transverse facial (Harkins et al 1992b) or carotid arteries, (Bayly et al 1983; Wagner er al 1989). Because the catheter is inserted in sensitive portions of the face, catheterisation of the facial and transverse facial arteries requires some co-operation from the horse. Furthermore, only small-gauge catheters (20-gauge) can be used in some horses with smaller arteries. Resulting complications include restricted blood flow and clotting of the catheter. Removal of the catheter frequently causes formation of at least a small haematoma, which impedes recatheterisation of the artery for several days. In studies using the carotid artery for blood sample collection, frequently one or both arteries are translocated to a subcutaneous position to facilitate catheterisation. The original translocation surgery (Tabemor 1969) was modified subsequently (Harkins et a1 1992a). Disadvantages of this procedure are: 1) expense of surgery and anaesthesia; 2) occasional complications from surgery; 3) a recovery period of 2-3 weeks when the carotid artery cannot be catheterised. Further, it is impractical to translocate the carotid artery of client-owned animals or horses that are tested only a few times. This paper describes a method for catheterising the carotid artery of horses using ultrasonography. The procedure requires no tranquillisation or surgery and minimal co-operation from the horses. Materials and methods Horses Six client-owned Thoroughbred racehorses ranging in age from 2 to 5 years and weighing 456-520 kg (489 & 16.7 kg) were used in studies requiring arterial blood-gas samples to evaluate the effects of various experimental factors on oxygen (02)and carbon dioxide (COz) concentrations. Catheterisation technique The hair over the jugular groove was clipped and the skin scrubbed with an antiseptic solution (Betadine Surgical Scrub,
Purdue Frederick Co., Norwalk, CT, USA). A generous amount of alcohol was applied to the skin as a transmission medium instead of ultrasonic coupling gel. A 7.5 MHz linear probe of the ultrasound unit (Aloka SOOV, Aloka Co. Ltd., Tokyo, Japan) was placed transversely on the neck to visualise a cross-sectional area of the jugular groove. Blood vessels are seen as anechoic circular images (Figs 1-3). The location of the vessels of the neck varies slightly between horses, but the carotid artery is 1-3 crn below the skin and deep to the jugular vein. On ultrasonography, the carotid artery is more circular and less collapsible than the vein. Also, the shape of the artery is consistent, whereas the more compliant vein may collapse from pressure of the ultrasound probe or distend if occluded below the level of imaging. The artery is usually directly under the vein in the cranial and middle parts of the neck which increases the difficulty of arterial catheterisation. Our experience suggests that the right carotid artery is easier to catheterise than the left because the right jugular vein and carotid artery diverge in the caudal portion of the neck. The artery usually deviates slightly lateral to the vein, although the artery of one horse deviated medially. In either case, the carotid artery can be entered without penetrating the jugular vein. The ultrasound probe is positioned so that the carotid artery is in the middle of the screen (Fig I). The skin is anaesthetised with 1 ml lignocaine (Lidocaine HCI-2%: Pan Vet, Inc., Springfield, MO, USA). A 16-gauge, 5.25-inch (1.7 mm x 13.3 cm) intraarterial catheter (Angiocath, Becton Dickinson Deseret Medical, Sandy, UT, USA) is inserted through the skin and a lignocaine bleb deposited at a 90' angle to the skin. The catheter can not be seen on the screen, but gentle pressure on the stilette and catheter disrupts the tissue directly in line with them, and the intended line of movement of the advancing catheter is visualised easily (Fig 3). The catheter is aimed towards the centre of the artery by redirecting the line of tissue displacement. When the catheter reaches the outside of the arterial wall, moderate pressure on the stilette forces the catheter into the lumen and arterial blood appears in the catheter. The catheter is sutured to the skin to secure it during experimentation. Results and discussion Figures 1-3 are thermal prints of the ultrasound screen. Figure 1 is a mid-cervical view of the jugular groove vessels showing the carotid artery directly below the vein. In Figure 2 the carotid artery is still deep but lateral to the jugular vein, allowing the artery to be entered without penetrating the vein. The tracheal
48 I
EQUINE VETERINARY JOURNAL
3: Verrical line of r i m e disruption Fig
the from carheter movement above the carotid artery ( a ) (hetufeen
Fig I : A midcervical view of the carotid artery ( a ) a n d j u g u l a r vein (v)
arrowi
following day. The catheter was flushed with heparinised saline then filled with heparin (1:lOOO) every 4 h to maintain patency. Blood was always aspirated into the syringe before injecting the heparinised saline to clear heparin from the tubing and prevent the introduction of a clot into the arterial circulation. Rarely, a clot would form in the catheter preventing further use of the catheter in subsequent experiments. The catheter remained in the artery a maximum of 30 h. There were no apparent complications from nerve damage, infection, or embolus formation.
Conclusion Ultrasonography can be used to catheterise the carotid artery as an alternative method for arterial blood collection. No complications from infection, emboli formation, or perceptible nerve damage was evident in 6 horses in which laryngeal function remained normal.
Acknowledgements rings are visible on the right side of the print. Figure 3, also a view of the caudal cervical area seen in Figure 2, is of the arterial catheter which has penetrated the skin and subcutaneous tissue. Gentle pressure is being applied to the stilette to disrupt the underlying tissue. Note the line of tissue disruption directly above the carotid artery. Because the video screen displays movement and not a still image, this phenomenon is visualised easily with the ultrasound screen. One concern associated with blood collection from the carotid artery is possible damage to the recurrent laryngeal nerves. The recurrent laryngeal, vagus, and sympathetic trunk nerves lie in close association with the carotid artery. These nerves are not visualised with ultrasound, and damage to the recurrent laryngeal nerve, via puncture or entrapment from scar tissue formation, can result in laryngeal paralysis (Derksen 1991). Each carotid artery of the 6 horses used in this study was catheterised '2-8 times within a 4-week period for different experimental procedures. Occasionally, the same artery was catheterised on consecutive days. However, there was usually an interval of 2-4 days between catheterisation of the same artery. At the end of the 4-week period, the larynxes were visualised by a flexible videoendoscope (Welch-Allyn Corp, Skaneateles Falls, NY, USA), and no perceptible nerve damage was evident since laryngeal function remained normal. Rose and Rossdale ( I 98 1) collected blood from the carotid artery over 200 times with no apparent complications. To minimise the number of times the carotid artery was traumatised from catheterisation in our studies, experimental procedures for the same horse were frequently scheduled on consecutive days. After completing one experimental procedure, the catheter was left in the artery overnight and used again the
These studies were supported by grants from the Horsemen's Benevolent and Protective Association (NY Division) and the Harry M. Zweig Memorial Fund for Equine Research.
References Bayly, W.M., Grant, B.D., Breeze, R.G. and Kramer. J.W. (1983) The effects of maximal exercise on acid-base balance and arterial blood gas tension in Thoroughbred horses. In: Equine Physiology, Eds: D. H. Snow, S. G. B. Persson and R. J. Rose. Granta Editions, Cambridge, UK. pp 400-415. Derksen. EJ. (1991) Diseases of the respiratory system. In: Equine Medicine and Sirrqery. 4th edn. Eds: P. T. Colahan. I. G . Mayhew. A. M. Merritt and J. N. Moore. American Veterinary Publications Inc.. Goleta, CA. pp 414-417. Harkins, J.D.. Rehder, R.S.. Hackett. R.P. and Ducharme, N.G. (1992a) Development of a nondisruptive face mask for measurement of respiratory airflow in exercising horses. J. appl. Physiol. (in press) Harkins. J.D., Beadle, R.E. and Kamerling, S.G. (1992b) The correlation of run times and physiological variables in Thoroughbreds. Equine vet. J. 24 (In Press) Kelso, T.B.. Hodgson. D.R.. Witt. E.H. and Bayly. W.M. (1987) Bicarbonate administration and muscle metabolism during high-intensity exercise. In: Equine Exercise Physiology I / . Eds: J. R. Gillespie and N. E. Robinson. KEEP. Davis, CA. pp 438-447. Rose, R.J. and Rossdale, P.D. ( 198 I)Techniques and clinical application of arterial blood collection in the horse. Equine wr. J. 13. 70-73. Tavernor, W.D. (1969) Technique for the subcutaneous relocation of the common carotid artery in the horse. Am. J. ref. Res. 30, 1881-1883. Wagner, A.E. (1991) Venous and arterial catheterization and fluid therapy. In: Equine Anesfhesia. Eds: W. W. Muir and J. A. Hubbell. Mosby-Year Book Inc.. St. Louis. MO. pp 140-145. Wagner. P.D.. Gillespie, J.R., Landgren, G.L.. Fedde. M.R.. Jones, B.W.. DeBowes, R.M., Pieschl. R.L. and Erickson, H.HJ. ( 1989) Mechanism of exercise-induced hypoxemia in horses. J. oppl. Physiol. 66, 1227-1233.
Received for pub,licution: 4.2.92 Accented: 11.4.92
