Page 207 - Basic Monitoring in Canine and Feline Emergency Patients

VetBooks.ir 10 Manometer-based Monitoring

AdesolA odunAyo*

Department of Small Animal Clinical Sciences, University of Tennessee,
Knoxville, Tennessee, USA

A manometer is one of the earliest pressure- interference with tissue perfusion of the intra-
monitoring devices. It measures the difference in abdominal organs, which may lead to ischemia or
liquid or air pressure by comparing it to an outside circulatory changes. Intra-abdominal hypertension
source, commonly the earth’s atmospheric pressure. (IAH) is defined as markedly increased IAP and is
A water manometer is commonly utilized in veteri- a life-threatening complication that occurs after
nary patients to provide critical information on major abdominal trauma or abdominal surgery.
pressures, including intra-abdominal pressure and IAH may occur as a result of increased intra-
central venous pressure. In some institutions, elec- abdominal volume (e.g. hemorrhage or other
tronic pressure transducers are used more com- ascites), inflammation, mass effect, or a combina-
monly, despite their increased cost. Electronic tion of these. In human patients, there has been
pressure transducers allow for continuous pressure correlation between IAP and organ dysfunction,
monitoring, as long as they are connected to the which ultimately leads to increased morbidity and
patient. mortality. As the intra-abdominal pressure rises, a
A water manometer, used for intermittent pres- condition called abdominal compartment syn-
sure monitoring, is easy to set up and is reasonably drome (ACS) can occur. IAH is defined as sustained
inexpensive to utilize for monitoring the critically IAP over 20 mmHg, which is associated with new
ill patient. It consists of a plastic or glass tube, organ dysfunction/failure.
marked in centimeters, which is usually filled with The reason that elevated IAP and ACS can lead to
a sterile isotonic fluid solution (0.9% NaCl is organ dysfunction is due to interference with the
used most commonly but lactated Ringers solu- abdominal perfusion pressure (APP), which is defined
tion, plasmalyte, and normosol can all be utilized). as the mean arterial pressure (MAP) minus the IAP.
A 12–60 mL syringe attached to the plastic tube Abdominal perfusion pressure should be maximized
via a three-way stopcock and extension tubing so that there is adequate delivery of oxygen and
completes the set up (Fig. 10.1). nutrients to the intra-abdominal organs. In general,
APP is compromised when there is IAH and ACS.
Maximizing APP usually involves maximizing MAP
10.1 Intra-abdominal Pressure and minimizing IAP.
Monitoring Consequences of IAH and ACS include decreases
in venous return, leading to decreased cardiac out-
Basic anatomy and physiology
put and hypotension (Fig. 9.2). Affected patients
Intra-abdominal pressure (IAP) is defined as the may also develop acute kidney injury, hepatic insuf-
steady-state pressure contained within the periton- ficiency and gastrointestinal signs because of
eal space that results from the interaction of the decreased blood flow and poor tissue perfusion.
abdominal wall and viscera. Abdominal compli- The increased abdominal pressure also pushes the
ance is quite limited because of skeletal structures, diaphragm cranially, which may result in increased
the diaphragm, internal organs, and the abdominal intrathoracic pressure, affecting ventilation and
wall. Thus when elevated IAP develops, there is oxygenation. Clinical consequences of IAH may

* Corresponding author: aodunayo@utk.edu

© CAB International, 2020. Basic Monitoring in Canine and Feline Emergency Patients 199
(eds E.J. Thomovsky, P.A. Johnson and A.C. Brooks)