Cardiovascular stabilization of critically ill and high-risk camelids undergoing anesthesia remains a challenge and has not been adequately reported in the literature.1,2 Camelids are preferentially nasal breathers and prone to airway obstruction following prolonged inhalant anesthesia.3 Poor anesthetic recovery may be worsened by systemic hypotension. Present estimates suggest that approximately 0.1% to 0.2% of healthy and 0.5% to 2% of sick dogs and cats die from anesthetic-related causes,4 which indicates an improvement, compared with previous reports.5,6 In comparison, a human study7 reveals an overall anesthetic-associated mortality rate of only 0.01%. In part, high death rates in veterinary patients have been associated with considerable cardiovascular depression during inhalant anesthesia. Although similar data have not been published for New World camelids to the authors' knowledge, anesthesia for these species is considered challenging.
The use of vasoactive medication, such as catecholamines, is indicated for the support of the cardiovascular system in critically ill animals (ie, patients with sepsis, endotoxemia, or trauma) and those receiving general anesthesia when goal-directed fluid therapy alone does not improve hypotension.8 The catecholamines dobutamine and norepinephrine are commonly used in critically ill horses9,10 and companion animals11,12 to treat hypotension. Dobutamine, an inotropic agent with predominant effects on β1- and β2-receptors and minor α1-adrenergic receptor effects, is indicated to increase CO and is often used to enhance tissue DO2 during general anesthesia and in critically ill patients.8 Dobutamine increases MAP and CI in foals,10,13,14 horses,15–18 lambs,19 and sheep.20,21 Norepinephrine primarily acts as a vasopressor with α1-, α2-, and β1-adrenergic receptor activity8 and is principally indicated for treatment of vasodilatory shock to maintain organ perfusion.8 Norepinephrine increases MAP and CI in sheep20–23 and foals.10,13,14
Despite the empiric use of dobutamine and norepinephrine in camelids, the specific effects of these agents have not been objectively evaluated and compared in those species. Anatomic, metabolic, and physiologic differences among camelids, equids, and ruminants24 have the potential to result in different cardiopulmonary responses to catecholamines in alpacas, compared with other domestic species. The purpose of the study reported here was therefore to characterize the cardiopulmonary effects of dobutamine and norepinephrine infusion in healthy adult alpacas undergoing isoflurane inhalant general anesthesia. We hypothesized that these catecholamines would cause similar cardiopulmonary responses in anesthetized alpacas as those reported in anesthetized adult horses and foals at comparable doses.10,13,14,17 More specifically, MAP, SAP, DAP, DO2, and Hb concentrations were expected to increase with both infusion rates of dobutamine and norepinephrine. We further hypothesized that SVI, CI, and O2 content would increase in a dose-dependent manner, whereas ERO2 would decrease in a dose-dependent manner. Enhanced SVR was only expected following norepinephrine infusion.
Central venous pressure
Diastolic arterial pressure
Dobutamine high infusion rate
Dobutamine low infusion rate
Oxygen extraction ratio
End tidal CO2
End tidal isoflurane
Mean arterial pressure
Norepinephrine high infusion rate
Norepinephrine low infusion rate
Pulmonary artery pressure
Systolic arterial pressure
Stroke volume index
Systemic vascular resistance
14 G × 130 mm, Milacath, Mila International, Florence, Ky.
Livestock Industries Inc, Lebanon, Ore.
Fort Dodge Animal Health, Fort Dodge, Iowa.
Hospira Inc, Lake Forest, Ill.
North American Drager Narkovet, Teleford, Pa.
Baxter Healthcare Corp, Deerfield, Ill.
Lifewindows 6000, Digicare, West Palm Beach, Fla.
Gaymar Industries Inc, Orchard Park, NY.
18 G × 48 mm Insyte Autoguard Catheter, Becton, Dickinson and Co, Franklin Lakes, NJ.
7.5 F, 110 cm, Arrow International, Reading, Pa.
8.5 F, 10 cm, Arrow International, Reading, Pa.
Spectrum, Datascope Corp, Mahwah, NJ.
Stat Profile, Critical Care Xpress, Nova Biomedical, Watham, Mass
Formulas used for calculated variables in a study of the cardiopulmonary effects of dobutamine and norepinephrine infusion in isoflurane-anesthetized healthy alpacas.
BW = Body weight. CaO2 = Arterial oxygen content. CcvO2 = Central venous oxygen content. SaO2 = Arterial oxygen saturation. O2 = Oxygen consumption.
Grubb TL, Schlipf JW, Riebold TW, et al. Minimum alveolar concentration of desflurane in llamas and alpacas. Vet Anaesth Analg 2006;33:351–355.
Brodbelt D. Perioperative mortality in small animal anaesthesia [published online ahead of print Jul 26, 2008]. Vet J doi:10.1016/j.gtvjl.2008.06.011.
Brodbelt DC, Pfeiffer DU, Young LE, et al. Risk factors for anaesthetic-related death in cats: results from the confidential enquiry into perioperative small animal fatalities (CEPSAF). Br J Anaesth 2007;99:617–623.
Lagasse RS. Anesthesia safety: model or myth? A review of the published literature and analysis of current original data. Anesthesiology 2002;97:1609–1617.
Dugdale AH, Langford J, Senior JM, et al. The effect of inotropic and/or vasopressor support on postoperative survival following equine colic surgery. Vet Anaesth Analg 2007;34:82–88.
Valverde A, Giguére S, Sanchez LC, et al. Effects of dobutamine, norepinephrine, and vasopressin on cardiovascular function in anesthetized neonatal foals with induced hypotension. Am J Vet Res 2006;67:1730–1737.
Pascoe PJ, Ilkiw JE, Pypendop BH. Effects of increasing infusion rates of dopamine, dobutamine, epinephrine, and phenylephrine in healthy anesthetized cats. Am J Vet Res 2006;67:1491–1499.
Dyson DH, Sinclair MD. Impact of dopamine or dobutamine infusions on cardiovascular variables after rapid blood loss and volume replacement during isoflurane-induced anesthesia in dogs. Am J Vet Res 2006;67:1121–1130.
Hollis AR, Ousey JC, Palmer L, et al. Effects of norepinephrine and a combined norepinephrine and dobutamine infusion on systemic hemodynamics and indices of renal function in normotensive neonatal thoroughbred foals. J Vet Intern Med 2006;20:1437–1442.
Craig CA, Haskins SC, Hildebrand SV. The cardiopulmonary effects of dobutamine and norepinephrine in isoflurane-anesthetized foals. Vet Anaesth Analg 2007;34:377–387.
Gehlen H, Weichler A, Bubeck K, et al. Effects of two different dosages of dobutamine on pulmonary artery wedge pressure, systemic arterial blood pressure and heart rate in anaesthetized horses. J Vet Med A Physiol Pathol Clin Med 2006;53:476–480.
Lee YH, Clarke KW, Alibhai HI, et al. Effects of dopamine, dobutamine, dopexamine, phenylephrine, and saline solution on intramuscular blood flow and other cardiopulmonary variables in halothane-anesthetized ponies. Am J Vet Res 1998;59:1463–1472.
Swanson CR, Muir WW III, Bednarski RM, et al. Hemodynamic responses in halothane-anesthetized horses given infusions of dopamine or dobutamine. Am J Vet Res 1985;46:365–370.
Toorop GP, Hardjowijono R, Dalinghaus M, et al. Comparative circulatory effects of isoproterenol, dopamine, and dobutamine in conscious lambs with and without aortopulmonary left-toright shunts. Circulation 1987;75:1222–1228.
Teboul JL, Douguet D, Mercat A, et al. Effects of catecholamines on the pulmonary venous bed in sheep. Crit Care Med 1998;26:1569–1575.
Di Giantomasso D, Morimatsu H, May CN, et al. Increasing renal blood flow: low-dose dopamine or medium-dose norepinephrine. Chest 2004;125:2260–2267.
Lascola KM, Hoffman AM, Mazan MR, et al. Respiratory mechanics in sedated and nonsedated adult llamas. Am J Vet Res 2007;68:676–684.
Mama KR, Wagner AE, Parker DA, et al. Determination of the minimum alveolar concentration of isoflurane in llamas. Vet Surg 1999;28:121–125.
Linton RA, Young LE, Marlin DJ, et al. Cardiac output measured by lithium dilution, thermodilution, and transesophageal Doppler echocardiography in anesthetized horses. Am J Vet Res 2000;61:731–737.
Giussani DA, Riquelme RA, Sanhueza EM, et al. Adrenergic and vasopressinergic contributions to the cardiovascular response to acute hypoxaemia in the llama fetus. J Physiol 1999;515:233–241.
Sillau AH, Cueva S, Valenzuela A, et al. O2 transport in the alpaca (Lama pacos) at sea level and at 3,300 m. Respir Physiol 1976;27:147–155.
Garcia-Pereira FL, Greene SA, Keegan RD, et al. Effects of intravenous butorphanol on cardiopulmonary function in isoflurane-anesthetized alpacas. Vet Anaesth Analg 2007;34:269–274.
Jurgens KD, Pietschmann M, Yamaguchi K, et al. Oxygen binding properties, capillary densities and heart weights in high altitude camelids. J Comp Physiol 1988;158:469–477.
Young LE, Blissitt KJ, Clutton RE, et al. Temporal effects of an infusion of dobutamine hydrochloride in horses anesthetized with halothane. Am J Vet Res 1998;59:1027–1032.
Schiffer ER, Schwieger IM, Gosteli P, et al. Systemic and splanchnic oxygen supply-demand relationship with fenoldopam, dopamine and noradrenaline in sheep. Eur J Pharmacol 1995;286:49–60.