Plus-Hex CLINICAL
After the patient assessment in this case, the information collected was used to assign an American Society of Anesthesiologists( ASA) physical status classification( Table 2).
Table 2. American Society of Anesthesiologists physical status classification system [ 10 ].
Classification ASA I
ASA II ASA III
ASA VI
ASA V
Description
A normal, healthy patient with no underlying disease
A patient with mild systemic disease
A patient with obvious systemic disease
A patient with a severe systemic disease that is a constant threat to life
A patient not expected to survive without the procedure
The ASA physical status classification system is used to assess and communicate a patient ' s pre-anaesthesia medical comorbidities [ 10 ]. Each patient that undergoes a general anaesthetic is assigned an ASA score as part of the hospital ' s pre-examination protocol. This patient was assigned ASA grade I.
An anaesthetist will use the preoperative assessment and the assigned ASA score to create and prescribe an individual anaesthesia plan for a patient, and they will make sure sufficient analgesia is prescribed for the patient, taking into consideration the planned procedure / surgery.
During the preoperative assessment, the anaesthetist will ensure the patient has been adequately fasted. Patients are fasted before surgery so they have an empty stomach; this reduces the likelihood of gastrooesophageal reflux. If this were to occur during the anaesthesia the patient would be at risk of developing oesophagitis, irritation of the pharyngeal tissues, oesophageal stricture formation and aspiration of the acidic gastric contents, with subsequent pneumonia [ 11 ]. To reduce the likelihood of these events occurring, the American Animal Hospital Association( AAHA) recommends fasting a healthy, mature patient for 4 – 6 hours before a general anaesthetic, with free access to water until the premedication is given [ 12 ].
Premedication and induction
In this case, the anaesthetist prescribed a combined sedation of 5 µ g / kg medetomidine, 0.01 mg / kg acepromazine and 0.2 mg / kg methadone, to be administered intramuscularly, which provided mild sedative effects. A 20 G intravenous catheter was placed in the left cephalic vein once the sedation had taken effect.
Before the patient was induced, the veterinary team completed a pre-anaesthesia checklist( Appendix 1 [ 13 ], see link on page 56). Pre-anaesthetic and surgical checks are vital for anaesthetic and surgical processes. They encourage communication within the team and improve patient safety by reducing the risk of human error [ 13 – 16 ].
A pre-anaesthesia checklist should be completed before the patient receives any induction agent. The full team assigned to the procedure / surgery should assemble and each member of staff should introduce themselves before the team works through the checklist verbally together. By completing the checklist and discussing the procedure together, the team will be better prepared, which will limit the number of preventable incidents and improve the outcome for the patient.
This patient was induced with propofol intravenously to effect; a total of 48 mg was given slowly. Propofol is an induction agent that interacts with gammaaminobutyric acid( GABA) receptors. It causes a potentiation of these receptors that results in a depression of brain and spinal cord activity and a loss of consciousness. This induction agent can, however, cause‘ marked respiratory depression and hypercapnia’ [ 17 ], but this is not normally a problem if the patient is quickly intubated and supplied with oxygen( O 2
). Intermittent positive-pressure ventilation( IPPV) may be started if the patient does not begin ventilating spontaneously.
Veterinary nurses( VNs) cannot induce anaesthesia by administering induction agents to effect unless directed by a VS who has developed a patient-specific protocol-driven pre-anaesthetic plan with the VN [ 18, 19 ]. However, it is common for a VS to induce anaesthesia while a VN assists and supports them during this process. The VN can assist during induction and intubation in many ways; for example, they can support and restrain the patient during intubation so the airway is visible, or they can intubate the patient themselves. Once the patient has a secured airway, the VN can connect the patient to the appropriate anaesthetic circuit and begin the delivery of O 2 and the inhalational agent, and connect the patient to the appropriate monitoring devices [ 17 ].
Once the patient in this case was sufficiently induced, he was intubated with a polyvinylchloride endotracheal tube( ETT). Intubating anaesthetised patients is important for many reasons: it secures the airway so anaesthetic gases can be supplied, protects the airway from regurgitated matter, reduces pollution of the volatile agent to the environment, and allows IPPV to be delivered [ 20 ]. In this case, the ETT was measured before induction to ensure it was the correct length, and different sizes were made available for intubation. Once
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