Clinical Commentary
Aspiration pneumonitis: Can we prevent it?
A. J. Bennell* and J. M. Senior
Philip Leverhulme Equine Hospital, University of Liverpool, Neston, UK.
*Corresponding author email: bennell@liverpool.ac.uk
Keywords:horse; aspiration; nasogastric intubation; colic; anaesthesia
Introduction
The case report in this issue by Monticelli and Adami describes
two cases of aspiration pneumonitis (Monticelli and Adami
2019). It is a condition well recognised in human patients
(Engelhardt and Webster 1999; Marik 2001) and aspiration of
gastro-oesophageal re flux associated with anaesthesia has
been reported in other veterinary species (Kogan et al.2008;
Obvey et al.2014). It has not previously been reported in
horses. This case report highlights another potential
complication in anaesthetising the emergency colic case and
discusses the best way to minimise respiratory complications
secondary to the presence of nasogastric (NG) re flux in the
perioperative period. Prompt recognition of hypoxaemia and
the presence of re flux within the endotracheal tube are key
events which should lead to a presumption of the likelihood of
aspiration pneumonitis while under general anaesthesia. In the
two reported cases, once aspiration of gastric contents had
occurred, treatment was challenging and success was
limited. Guidelines (BMJ Best Practice Guidelines, 2017) for
treating aspiration in human patients includes suctioning of
the oropharynx, tilting to a head up position, bronchoscopy
and suctioning within a few hours of the incident. Positive end-
expiratory pressure and positive-pressure ventilation are not
recommended until endotracheal suctioning is performed .
Many of these treatments are currently impractical in the
horse. As this protocol would not be appropriate in horses, we
need to consider methods of reducing the risk of aspiration.
Clearly, prevention of aspiration pneumonitis caused by
gastric contents is preferable to being faced with having to
treat this complication.
Anaesthetic risk and nasogastric intubation
It is well recognised that anaesthesia for colic surgery carries
signifi cant risk. CEPEF-1 and 2 showed anaesthesia for colic
surgery had a greater mortality rate of approximately 7.9%
compared with 0.9% for healthy horses (Johnston et al.2002).
Smaller, single-centre studies have reported similar mortality
rates for anaesthesia in colic cases (Hodgson and Dunlop
1990; Young and Taylor 1993; Mee et al.1998; Bidwell et al.
2004). Complications following general anaesthesia for colic
surgery are varied but there is little data regarding respiratory
complications in the perioperative period for colic cases. Nasogastric intubation is technically easy to perform and
is generally well tolerated by most horses. Reports regarding
complications of NG intubation in horses are rare and are
limited to trauma of the oesophagus and pharynx (Hardy
et al. 1992). Epistaxis can occur secondary to NG intubation
but is usually self-limiting. To our knowledge, this case report is
the first report of aspiration pneumonitis in colic cases,
although it may be that this condition is under-reported. The case report by Monticelli and Adami (2019) raises the
question of how to best manage the risk of gastric re
flux in
the perioperative period to reduce morbidity and mortality
due to aspiration in colic cases.
Risk factors for aspiration
The risk for aspiration of gastric contents in horses is generally
considered to be lower than human patients or many other
veterinary species due to equine gastric anatomy (Budras
and Henschel 2008). The risk factors for aspiration
hypothesised by Monticelli and Adami include gastric
impaction, abdominal distention and the presence of an
indwelling NG throughout the induction and maintenance
phases of anaesthesia.
Gastric impaction
Transabdominal ultrasonography of the stomach may be
useful in assessing gastric distention or impaction. It is, however,
subjective and there is confl icting evidence of the sensitivity
and repeatability of this method (Lores et al.2007; Le Jeune
and Whitcomb 2014). A rapid ultrasonographic scanning
technique which can be employed during investigation,
known as fast localised abdominal ultrasonography of horses
(FLASH) scanning, also has potential to help identify cases
where gastric distention is present while helping with decision
making as to whether surgery may be required (Busoni et al.
2011; Naylor 2015). This may also help quickly identify horses
where passage of a NG tube is bene ficial.
Abdominal distention
Abdominal distention is often assessed subjectively in cases
with an acute abdominal emergency. Transabdominal
ultrasonography has value in the diagnosis of tympany and
gaseous distention of the small intestine (Freeman 2003).
Percutaneous trocharisation of the large colon or caecum
can be undertaken to relieve gaseous distention in cases
which have been identifi ed on palpation per rectum. This is
not without risk and should not be performed in cases where
surgery is an option, whenever possible (Rowe 2008).
Presence of an indwelling NG tube throughout
the induction and maintenance phases of
anaesthesia
Re flux, either spontaneous or a positive yield on the passage
of a NG tube, occurs in 13% of the horses presented to the
Philip Leverhulme Equine Hospital for investigation of acute
colic (Philip Leverhulme Equine Hospital Colic Database).
© 2017 EVJ Ltd
188 EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2019)31(4) 188-190
doi: 10.1111/eve.12818