Biomedical Engineering Reference
In-Depth Information
(
Aufderheide and Lurie, 2004
). Use of end tidal CO
2
(ETCO
2
) monitoring, or capnography, has been proven
useful in evaluation of CPCR efforts in humans (Neumar
et al., 2010). An increase in ETCO
2
to the 18
used to provide access after the stylet has been removed.
The skin overlying the area to be accessed should have
a surgical preparation. In mature animals a 0.5-cm skin
incision should be made with a scalpel over the site of
access to facilitate use of a bone marrow biopsy needle.
Intraosseous access sites should be protected after emer-
gency CPRC to prevent manipulation and removal of the
catheter by the animal and/or breakage of the needle/
catheter device.
The intratracheal route is favored by some clinicians
because it is present once an airway is established and does
not require additional placement of catheters, which may
delay the time to administration of drugs. Several emer-
gency medications are well absorbed via the intratracheal
route including: atropine, epinephrine, lidocaine, naloxone,
and vasopressin. Bicarbonate should not be administered
by the intratracheal route because it is irritating to the
respiratory mucosa and inactivates surfactant (
Ford and
Mazzaferro, 2005
). Drugs administered by the intratracheal
route should be diluted, preferentially by sterile water, to
enhance absorption (
Naganobu et al., 2000
). If sterile water
is not available, 0.9% NaCl is acceptable. For most drugs,
the intratracheal dose is 2
e
2.5 times the intravenous doses
(
Ford and Mazzaferro, 2005; Plunkett and McMichael,
2008; Neumar et al., 2010
). For epinephrine, the dose
should be increased 3
24 mmHg
range is associated with the return of spontaneous circu-
lation. During continued provision of basic life support
(chest compressions and ventilation) it is important to
continually monitor the effects of CPCR by checking pul-
ses, ECG, and ETCO
2
. Pulses can be difficult to palpate and
some pulses may be a result of retrograde venous flow
during CPRC. Pulses palpated when chest compressions
are paused are a reliable indicator of ROSC, but no more
than 10 seconds should be allowed to attempt to palpate
a pulse after ceasing chest compressions (
Neumar et al.,
2010
). Pulse oximetry is not an effective tool to monitor
CPCR because peripheral pulsatile blood flow is often
inadequate, but it is a good indicator of clinical condition
once ROSC is achieved (
Neumar et al., 2010
). Central
venous oxygen saturation is a good measure of the
adequacy of blood flow during CPCR and can be measured
using an oximetric tipped central venous catheter placed in
the cranial vena cava. If after assessing the effects of CPCR
it is found that the procedure is not resulting in improve-
ment, then repositioning the patient or changing team
members' roles may improve outcome.
After basic life support is underway and deemed effective,
advanced measures and monitoring should be undertaken.
Advanced cardiac life support (ACLS) includes pharmaco-
logical support and defibrillation, if necessary. ACLS in
combination with ongoing basic life support measures
increases the likelihood of resuscitation and survival.
A central line is the preferred route for administration of
medication during CPCR, but is rarely in place at the time
of CPA. Other routes of administration include peripheral
vein catheterization, intraosseous (i.o.), and intratracheal
(i.t.). Blind intracardiac injections are discouraged because
of potential complications, including coronary artery
laceration and resultant myocardial ischemia, hemorrhage,
induction of arrhythmias, and pneumothorax. Intracardiac
injections may be performed if open chest cardiac
compressions are being administered and the ventricles are
visible. Administration of medication through a peripheral
vein catheter should be followed by 0.9% NaCl while
elevating the extremity to use gravity to assist infusion. If
drugs are administered intravenously to treat arrhythmias,
two minutes of chest compressions should be performed
after administration prior to checking the ECG.
Intraosseous administration sites in nonhuman primates
include the proximal humerus, tibial crest, and femoral
trochanteric fossa. In neonatal and new world primates
these spaces can be accessed using a large bore (16 or 18
gauge) 1-inch needle, which is directly attached to an
infusion set. In larger species and adult nonhuman
primates, a bone marrow biopsy needle (Jamshidi) may be
e
10 times the intravenous dosage
(
Ford and Mazzaferro, 2005; Plunkett and McMichael,
2008; Neumar et al., 2010
).
Intravenous fluid therapy should be instituted at shock
rates only in cases where the patient was hypovolemic prior
to CPA as in episodes of substantial hemorrhage and pre-
existing dehydration (
Neumar et al., 2010
). The recom-
mended rate of intravenous fluid administration in
euvolemic patients is 20 ml/kg as a bolus. This dose rate
has also been used in nonhuman primates successfully. The
bolus should be administered as quickly as possible.
Recognition of common cardiac rhythm disturbances is
critical to monitoring and treating CPA. Placement of ECG
leads should occur early after arrest for timely assessment
as well as to avoid excessive interruptions to chest
compressions. Although asystole is one of the most
common rhythm disturbances seen in veterinary medicine,
pulseless electrical activity (PEA, also known as electro-
mechanical dissociation) also occurs and is typified by
bizarre electrical complexes on ECG with no associated
mechanical contraction of the ventricles. Pharmacological
intervention alone has not proved to be absolutely effective
in the treatment of asystole and PEA (
Neumar et al., 2010
).
The treatment of asystole and PEA is best approached by
a combination of CPCR basic life support measures and
pharmacological intervention.
Ventricular fibrillation may occur as a primary
arrhythmia causing CPA or may result from conversion of
asystole or PEA. Ventricular fibrillation may be either fine
e
