Canis ISSN: 2398-2942

Anesthesia: in respiratory impairment

Contributor(s): John Dodam, Marieke de Vries

General

Factors

  • Highest risks are associated with period between sedation and endotracheal intubation, and during the recovery period after extubation.
  • Priority is maintenance of tissue oxygenation.
  • Dogs with reduced pulmonary reserve are less able to cope with the sudden changes associated with the onset of general anesthesia.
  • Increased work of breathing because of respiratory compromise is very exhausting for the patient.
  • Accurate diagnosis of any condition causing respiratory impairment is essential in planning management of anesthesia for these cases. Anticipation and planning ahead are essential for a good outcome.
  • Extrapulmonary causes of respiratory insufficiency affect pulmonary ventilation:
  • Intrapulmonary conditions affect the normal balance between ventilation and perfusion in the lung, eg pulmonary edema Lung: pulmonary edema, neoplasia Lung: pulmonary neoplasia, contusions Lung: contusion, embolism Lung: pulmonary thromboembolism, pneumonia Lung: bacterial pneumonia.
  • Brachycephalic breeds are predisposed to upper airway obstruction because of stenotic nares, elongated soft palate, everted laryngeal saccules and hypoplastic trachea.
  • Respiratory distress often results in very distressed patients, especially when onset is acute. Sedation Sedation sedative protocols should be considered to prevent patient entering vicious circle and becoming more dyspneic.
  • Dyspneic patients, especially brachycephalic breeds, tend to quickly become hyperthermic.
  • Cyanosis in the conscious animal occurs with severe pathophysiological changes and indicates high anesthetic risk. It results from increased deoxyhemoglobin and may indicate hypoxia. Cyanosis may be difficult to detect. However, when diagnosed, immediate oxygen therapy is indicated.
  • Respiratory insufficiency is relatively difficult to assess in the abscence of severe signs, eg cyanosis. Pulmonary function tests are difficult in animals. An estimate of alveolar ventilation can be obtained in a cooperative subject by determining the tidal volume (Vt) with a face mask and simple respirometer, eg Wright's respirometer. Assume dead space volume (Vd) is 30% of Vt. Alveolar ventilation = (Vt-Vd) x respiratory rate. Values of 100-130 ml/kg/min are enough to maintain normal blood gas concentrations in the absence of ventilation/perfusion imbalance.

Pre-operative assessment

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Pre-operative preparation

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Pre-anesthetic preparation

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Induction and maintenance

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Monitoring during anesthesia

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Recovery of anesthesia

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Miscellaneous

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Further Reading

Publications

Referred papers

Other sources of information

  • Grubb T (2016) Respiratory compromise. In: BSAVA Manual of Canine and Feline Anaesthesia and Analgesia. 3rd edn. Duke-Novakovski T, de Vries M, Seymour C J (eds). Chapter 22.
  • Dugdale A (2010) Some respiratory considerations. In: Veterinary Anesthesia Principles to Practice. Wiley Blackwell, Chapter 47.
  • Muir, Hubbell, Skarda & Bednarski (2000) eds.Veterinary Anesthesia. 3rd edn. St Louis: Mosby Year Book. pp 455-474.


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