Biomedical Engineering Reference
In-Depth Information
McMichael, 2008; Neumar et al., 2010
). If it is necessary
to discontinue chest compressions, they should not be
delayed more than 10 seconds, if possible. Interruption in
chest compressions may allow a decrease in intrathoracic
pressure, intravascular pressure, and coronary perfusion
pressure (
Neumar et al., 2010
). Correct positioning of the
patient is critical to the success and effectiveness of chest
compressions. Since most species of nonhuman primates
have thoraxes that are similar anatomically to dogs and
cats (laterally flattened), positioning the animal in right
lateral recumbency will allow effective compressions to
be applied to the left lateral thorax. The compression is
administered from directly above the animal. Great apes,
who have a thoracic anatomy similar to humans, should
be placed in dorsal recumbency with chest compressions
applied over the sternum.
Chest compressions should be started immediately after
recognition of CPA. While chest compressions are initi-
ated, other members of the team should access the crash
cart for supplies such as endotracheal tubes and intravenous
catheters. For small nonhuman primates, the hand of the
person administering CPCR should be placed on one side
of the thorax and the thumb on the other. Medium to large
nonhuman primates should have compression performed
over the fourth to sixth intercostal space at the costochon-
dral junction. Nonhuman primates greater than 10 kg
should have compressions performed over the widest
diameter of the thoracic cage, just dorsal to the costo-
chondral junction. The chest wall should completely recoil
following compression, and the rescuer should aim for
approximately 30% compression of the thoracic wall.
Compressions should be administered at a rate of 80
subcutaneous tissues to the level of the intercostal muscles.
A blunt, stab incision is made in the sixth intercostal muscle
at the same time as ventilation is discontinued in order to
minimize the chances of traumatizing the lung. The inci-
sion is extended dorsally and ventrally to the level of the
sternum staying toward the caudal aspect of the intercostal
space to minimize the chance of lacerating the intercostal
artery on the caudal aspect of the rib. A rib retractor is used
to enhance exposure and visualization of the thorax. The
pericardium is sharply incised ventral to the phrenic nerve.
Once the heart is exposed it is grasped and gently squeezed
from apex to base, allowing time for the ventricle to fill
between contractions. If the ventricles are not filling, fluids
can be administered intravenously or directly into the right
atrium. Some advocate cross-clamping of the descending
aorta using a Rummel tourniquet to increase coronary and
cerebral blood flow (
Ford and Mazzaferro, 2005
). If a cross
clamp is used it should be removed after less than 10
minutes of use (
Barton and Crowe, 2000
).
Orotracheal intubation with a low pressure, high
volume endotracheal tube is the most common method for
establishing an airway in veterinary medicine. Visual
confirmation of placement with a laryngoscope is recom-
mended, and, in some cases, secretions and blood may
require suction to clear the oropharynx. Use of a laryngo-
scope will also minimize the amount of time necessary for
intubation. While intubation is taking place, ECG leads and
peripheral venous catheters can be placed. Tracheostomy
may be necessary if oral intubation is impossible. Breaths
should be provided by the second person on the team while
the first team member continues with chest compressions.
Once an endotracheal tube has been placed there is no need
to pause chest compressions for ventilation. Chest
compressions should continue at a rate of 80
100
per minute, with 1:1 compression to relaxation ratio. A
team member should palpate for a pulse to assure that the
compression technique is effective. If no pulse is detected,
the animal and/or rescuer's hands should be repositioned.
The person performing chest compressions should change
every 2 minutes in order to maintain adequate force and
rate (
Neumar et al., 2010
).
Internal cardiac massage should be considered in
patients where a pathological condition exists that prevents
enough of a change in intrathoracic pressure that closed
chest CPCR will not be effective in promoting forward
blood flow. These conditions include penetrating chest
wounds, chest wall trauma including fractured ribs, pleural
space disease, pericardial effusion, obesity, and diaphrag-
matic hernia. An additional indication for internal cardiac
massage is a lack of ROSC following 2
e
100 per
e
minute while ventilations are provided every 6
8 seconds
(
Neumar et al., 2010
). The use of doxapram to stimulate
respiration is not currently recommended as it has been
shown to decrease cerebral blood flow and increase cere-
bral oxygen demand (
Dani et al., 2006
). If the patient only
has respiratory arrest and spontaneous respiration does not
occur after stimulation with two breaths, one could
consider acupuncture of the Jen Chung (GV26) point. This
technique has been effective in stimulating respiration in
canine and feline patients and is performed by twirling a 25
gauge, 5/8 inch needle inserted to the bone in the nasal
philtrum at the ventral aspect of the nares (
Davies et al.,
1984; Hackett and Van Pelt, 1995
). If after these attempts
spontaneous respiration does not occur, 10
e
5 minutes of
external compressions (
Ford and Mazzaferro, 2005; Plun-
kett and McMichael, 2008; Wells, 2008
).
To perform open CPCR, the patient is placed in right
lateral recumbency and a surgical preparation is performed
over the left fifth to seventh intercostal spaces. An incision
is made over the fifth intercostal space through skin and
15 breaths per
minute, at no greater than 20 cmH
2
O airway pressure
should be administered. Excessive ventilatory rates can
lead to decreased coronary perfusion pressure, decreased
cardiac preload, decreased cardiac output, increased intra-
thoracic pressure, and decreased venous return and lowers
the success rate for CPRC in humans and animal models
e
e
