46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
87
General anaesthetic maintenance
tips to improve and maintain
perfusion during colic surgery in the
horse
Zeiler, GE
*
Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of
Pretoria, South Africa.
Horses suffering from colic often present with a myriad of physiological disturbances
which include: pain; cardiovascular -, respiratory -, acid/base -, and electrolyte
derangements that often require aggressive emergency medical and/or surgical
intervention (Thoefner et al. 2001, Dukti et al. 2009, Boesch 2013). Horses requiring
general anaesthesia for surgical intervention to manage colic are at increased risk
(Dukti et al. 2008); up to 50% of mortalities in this class are due to cardiovascular
collapse (Senior 2013). This proceeding will focus on perfusion management during
surgical intervention while the patient is under general anaesthesia.
Brief introduction to applicable physiology
The critical concern is to ensure that adequate oxygen (O2) is being delivered to the
metabolically active tissue beds (by-product of metabolism includes the formation
carbon dioxide; CO2) in order to maintain energy production to sustain normal
tissue activity. The cardiovascular system is the principle transport system of oxygen
to the metabolically active tissue. Oxygen is mainly (97%) transported bound to
haemoglobin (Hb). Haemoglobin is the major contributor for determining the
oxygen content (CaO2) of the blood (Table 1).
Equations to calculate certain cardiovascular variables
Oxygen
Content
(CaO2)
CaO2 = [1.34
(mL/100mL) x SaO2 (%)
x Hb (g/dL)] + [0.003 x
PaO2 (mmHg)]
SaO2 – Haemoglobin saturation of
oxygen in systemic artery
Hb – Haemoglobin content
PaO2 – Partial pressure of oxygen in
systemic arterial blood
SV – Stoke volume
HR – Heart rate
SVR – Systemic vascular resistance
Cardiac
CO = SV x HR
Output (CO)
Mean Arterial MAP = CO x SVR
Pressure
(MAP)
Delivery of
DO2 = CaO2 x CO
Oxygen to
tissue (DO2)
Table 1: Equations used to calculate cardiovascular variables
mentioned in the text.
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