List of Figures

Figure 1.1 Pin index system - the pins in the mounting block fit into the holes in the gas cylinder. 5 Figure 1.2 Pressure gauges for nitrous oxide (left) and oxygen (right) cylinders. 5 Figure 1.3 Cylinders are opened and closed either using a ratchet spanner (left), cylinder key (centre) or hand-operated valve (right). 6 Figure 1.4 Oxygen concentrator suitable for providing oxygen supplementation for small animal anaesthesia. 7 Figure 1.5 The gas flow rate is read from the position of the top of the bobbin of the flow meter. In flow meters with a ball, rather than a bobbin (right), the reading is taken from the centre of the ball. 8 Figure 1.6 Turret-type flow meters can be used as a simple means of providing a controlled source of oxygen, during both anaesthesia and recovery. 8 Figure 1.7 An example of a system designed to prevent filling of a vaporizer with the incorrect anaesthetic agent. The end of the filling tube fits into a slot in the vaporizer (left), and the other end of the tube fits onto a collar on the bottle (right). 8 Figure 1.8 Vaporizer mounting system (Selectatec) that allows vaporizers to be exchanged quickly and easily between machines. 9 Figure 1.9 A double-chamber system that is designed to minimize exposure of personnel to waste anaesthetic gases (VetTech Solutions). 11 Figure 1.10 Anaesthetic chamber for use with small mammals (VetTech Solutions) - the anaesthetic agent is piped in at the bottom of the chamber, and an exhaust port at the top is connected to a gas-scavenging device. 11 Figure 1.11 (a) Diagram of a simple face mask - rebreathing of exhaled gases is prevented by use of relatively high fresh gas flow rates. (b) Face masks for use with a range of laboratory species. The rubber diaphragm helps provide a seal around the animal's nose to prevent breathing of room air around the mask. 15 Figure 1.12 Concentric mask system for rodents and rabbits that combine delivery of anaesthetic gases with removal of waste gas through an outer tube. An extraction fan and activated charcoal absorber are used to remove the anaesthetic gases and prevent exposure of personnel (Harvard Instruments). 17 Figure 1.13 Low flow face masks: side view right top and end-view of mask left (AAS), and below, low flow mouse mask (Flair designs) 18 Figure 1.14 Down-draft operating table - a heating blanket has been added to maintain the animal's body temperature. Anaesthetic is being delivered via a nasal catheter, and a pulse oximeter is in use. 18 Figure 1.15 Ayre's T-piece to show gas flow pattern. 19 Figure 1.16 T-pieces with low-dead space connectors. Above, standard T-piece; below, Jackson Rees modified T-piece. 19 Figure 1.17 Standard (left) and low-dead space (right) endotracheal tube connectors and T-pieces. 20 Figure 1.18 Low dead space T-piece for use with small rodents, constructed from a disposable Y connector and 'Bubble-tubing'. 20 Figure 1.19 Bain's circuit (a) and modified Bain circuit (b) to show gas flow patterns. 21 Figure 1.20 Bain's circuit (a) and modified Bain circuit (b). 22 Figure 1.21 Magill circuit to show gas flow patterns. 23 Figure 1.22 Magill circuit. 23 Figure 1.23 Circle system Unidirectional valves (a) control the flow of gas, carbon dioxide is absorbed by a soda-lime canister (b) and then exhaled gas is rebreathed by the animal. A reservoir bag is included in the circuit (c). 25 Figure 1.24 Circle system. Both disposable systems (as shown) and re-usable circuits are available. 25 Figure 1.25 Elastic band used to help maintain the position of a rat or mouse in a face mask. The attachment is made from the components of a protective face mask (Segre, Sweden). (Concentric mask supplied by VetTech Solutions.) 28 Figure 1.26 Endotracheal tubes of different sizes and designs. (a) Re-usable cuffed tube, (b) Disposable uncuffed tube, (c) Disposable armoured, cuffed, tube and (d) introducer. 29 Figure 1.27 Endotracheal tubes for rodents and other small mammals can be constructed from intravenous catheters. A small piece of Silastic tubing is placed approximately 1cm from the tip, and acts as a seal on the larynx to reduce leakage of gas around the tube. A flexible wire (from a Seldinger catheter) is used to guide the tube into the trachea. 29 Figure 1.28 Laryngoscope blades of various designs. Macintosh (a, b), Wisconsin (c, d), Soper (e, f) and Miller (g, h). 31 Figure 1.29 Intubation of the rabbit by using a laryngoscope and a modified Wisconsin blade. 33 Figure 1.30 Blind intubation of a rabbit. Listening to the animal's breathing as the tube is advanced aids correct placement. 34 Figure 1.31 Apparatus for intubation of rats and mice, available from Hallowell instruments. 36 Figure 1.32 Rat positioned for intubation. (Tilting table from Hallowell instruments.) 36 Figure 1.33 Fibre optic system for illuminating the larynx during intubation. An intravenous catheter which will be used as the endotracheal tube has been placed over the tip of the illuminated guide. 36 Figure 1.34 Intranasal catheters used for delivery of anaesthetic agents or oxygen (guinea pig, left, with cat urinary catheter; rat, right, with paediatric nasogastric tube). 38 Figure 1.35 Oxygen bubble tubing used for connecting a nasal catheter to an anaesthetic trolley, for delivery of oxygen or anaesthetic agents. 38 Figure 1.36 Laryngeal mask. 39 Figure 1.37 Insulin syringe, 'butterfly' infusion set, catheters and anaesthetic extension line. 40 Figure 1.38 Method of anchoring intravenous catheters on a rabbit ear. One wing of the catheter is removed (a), a piece of tape is laid along the ear across the remaining wing (b) and two further pieces of tape are wrapped around the ear (c). 42 Figure 1.39 Sleep time in different strains of mice given pentobarbital. Data redrawn from Lovell (1986a,b,c). 43 Figure 1.40 Duration of anaesthesia and sleep times in rats with different anaesthetics (data from various studies). Ket/Xyl - ketamine and xylazine; Ket/Med - ketamine and medetomidine; Ket/Diaz - ketamine and diazepam; Innovar-Vet - fentanyl and droperidol; Hyp/Mid - hypnorm and midazolam; Etorphine/ACP - etorphine and acepromazine; pentobarbital; Fent/Med - fentanyl and medetomidine. 44 Figure 2.1 Anchoring system for breathing circuits, infusion lines and monitoring cables (intersurgical). 78 Figure 2.2 Methods of protecting an animal's eyes during anaesthesia, by application of ophthalmic ointment or 'liquid tears' (right), or by taping the eyes shut (left) (or by using both methods, left). 79 Figure 2.3 Respiratory monitor using a pressure sensor. The device shown is designed for use during MRI procedures. 84 Figure 2.4 Pulse oximeter suitable for use in mice (Mouse PhysioSuite, Kent Scientific) (model shown includes capnography, temperature maintenance and monitoring and a ventilator). 85 Figure 2.5 The 'MouseOx' pulse oximeter in use (STARR instruments). 86 Figure 2.6 Placement of pulse oximeter probes on a guinea pig and a rabbit. 86 Figure 2.7 Placement of pulse oximeter probes on a rat and a...