Anesthesia Student Survival Guide.pdf - Index of

136 ● AnesthesiA student survivAl Guide
In most short cases, automatic blood pressure monitoring is done at least
every 5 min. Many automatic blood pressure machines also have a “stat” mode
where measurements are done immediately one after the other for a short
period of time. Many anesthesiologists also put a manually operated blood
pressure cuff on a second arm, in case the automatic blood pressure monitor
fails to provide reasonable numbers. This may occur when the patient’s arms
are tucked and the surgeon is leaning against the pressure cuff. This second cuff
is usually placed on the arm with the pulse oximeter. When this cuff is inflated
to the point that the pulse oximeter waveform is extinguished, the dial will
indicate the patient’s systolic pressure. Alternatively, a second blood pressure
cuff may be placed on a patient’s lower extremity.
In longer, complex cases or in very sick patients, invasive blood pressure
monitoring via an arterial line is frequently utilized. Arterial lines are most
often inserted into one of the radial arteries, although it may less commonly
be placed in a brachial, femoral, ulnar, or dorsalis pedis artery. This method
involves connecting an arterial catheter (usually a 20 gauge for adults) to
an electronically amplified pressure transducer via a narrow fluid-filled
tube (Fig. 11.2). This arrangement provides beat-to-beat pressure information
that is helpful, for instance, in patients with poor ventricular function.
In addition, since arterial blood gases are easily drawn from an arterial
line, they can be particularly useful in patients with pulmonary disease or
patients with acid–base disorders. Also, the ease with which blood samples
can be sent for hemoglobin or glucose levels makes arterial lines useful in
patients whose condition is changing rapidly over time or in which large
blood losses are anticipated.
Electrocardiographic Monitoring
All anesthetized patients undergo electrocardiographic monitoring. This provides
the clinician with three types of information: (1) heart rate, (2) cardiac
rhythm, and (3) information about possible myocardial ischemia (via ST segment
analysis). In addition, ECG monitoring can help assess the function of a
cardiac pacemaker.
The most common electrocardiographic system used during anesthesia is
a 5-electrode lead system. This arrangement (Fig. 11.3) allows for the recording
of any of the six limb leads plus a single precordial (V) lead.