Levels of consciousness will affect the premedication choices for these patients – patients that are very obtunded ( or worse ) may not require a premedication . After pre-anaesthetic medication has been administered , the patient ’ s head should be mildly elevated at an angle of approximately 30 °. This maximises the arterial blood supply to , and venous drainage from , the brain ( Platt & Olby , 2013 ), limiting venous congestion and causing minimal changes to ICP ( Armitage-Chan et al ., 2007 ). This can be achieved through resting the patient ’ s head on a foam wedge or sandbag , ensuring the jugular veins are not compressed ( Figures 5 and 6 ).

Figure 3 . Patients should be walked using a harness rather than a collar or slip-lead .

Induction and positioning of the head

Patients with intracranial disease should be preoxygenated for a minimum of 3 minutes ( McNally et al ., 2009 ) ( causing minimal stress ), in order to fill the functional residual capacity of the lungs with 100 % oxygen ( O ₂

) and prevent hypoxaemia during induction ( Figure 4 ) ( Leece , 2016 ).

Figure 5 . Patient ’ s head raised at an approximately 30 ° angle using a foam wedge .

Figure 6 . Patient ’ s head raised using a foam wedge , ensuring the jugular vein is not compressed .

Figure 4 . Preoxygenation of a patient after premedication , using a mask with a tight-fitting seal , producing a capnography trace .

On induction of anaesthesia , an adequate depth should be reached before attempting endotracheal intubation , as coughing and gagging can increase ICP . This risk can be minimised by using a pre-anaesthetic medication that provides adequate sedation and has antitussive effects , and by suppressing the laryngeal reflexes through the administration of a sufficient amount of anaesthetic induction agent ( Armitage-Chan et al ., 2007 ).

48 Veterinary Nursing Journal