Secrets Flashcards
Best way to maintain renal function during surgery?
To ensure an adequate intravascular volume, maintain cardiac output and avoid drugs known to decrease renal perfusion.
Measures to acutely decrease intracranial pressure (ICP) include
Measures to acutely decrease intracranial pressure (ICP) include elevation of the head
of the bed; hyperventilation (PaCO2 25 to 30 mm Hg); diuresis (mannitol and/or
furosemide); and minimized intravenous fluid. In the setting of elevated ICP, avoid
ketamine and nitrous oxide.
Malignant hyperthermia: what it is, presentation, treatment, consequences
Malignant hyperthermia (MH) is an inherited disorder that presents in the perioperative
period after exposure to inhalational agents and/or succinylcholine. The disease may be
fatal if the diagnosis is delayed and dantrolene is not administered. The sine qua non of
MH is an unexplained rise in end-tidal carbon dioxide with a simultaneous increase in
minute ventilation in the setting of an unexplained tachycardia.
Special considerations for diabetics?
Patients with diabetes have a high incidence of coronary artery disease with an atypical or
silent presentation. Maintaining perfusion pressure, controlling heart rate, continuous ECG
observation, and a high index of suspicion during periods of refractory hypotension are
key considerations.
Malignant hyperthermia may be mimicked by:
Thyroid storm may mimic MH. It is confirmed by an increased serum tetraiodothyronine
(T4) level and is treated initially with b-blockade followed by antithyroid therapy.
Universal donors for packed RBCs, for plasma?
O-negative blood is the universal donor for packed red blood cells; for plasma it is AB positive.
What are the benefits of cardiovascular drugs?
All of the components of organ perfusion, including preload (end-diastolic volume), afterload,
inotropy, heart rate, and myocardial oxygen supply and demand can be pharmacologically
modified. An underlying concept is the Frank-Starling principle, which states that increased
myocardial fiber length (i.e., end-diastolic volume) improves contractility up to a point of optimal
contractile state, further stretching results in declining performance
Discuss the limitations of drugs that alter vascular tone.
Preload can be altered with intravascular volume shifts and with drugs that change vascular
tone, most notably the venous capacitance vessels. In addition, arterial vasodilators may shift
failing myocardium to a more effective contractile state as a result of afterload reduction and
decreased impedance to ventricular ejection. However, the intrinsic contractile state is not
improved by vasodilators, in contrast to the effect of positive inotropic agents.
What are the general goals of inotropic support and the characteristics of the
ideal inotrope?
The goal is increasing cardiac output by improving myocardial contractility to optimize endorgan
perfusion. In addition, for enlarged hearts a decrease in ventricular diameter, wall
tension, and myocardial oxygen demand is also desirable and should enhance the contractile
state and myocardial perfusion. Some inotropic agents also decrease pulmonary vascular
resistance, improving right heart output and forward flow
Discuss the hemodynamic profile of the phosphodiesterase III inhibitors
amrinone and milrinone.
Amrinone and milrinone are approximately equipotent to dopamine and dobutamine in increasing
cardiac output through increased inotropy and improved lusitropy (myocardial relaxation). In
addition to direct myocardial effects, vasodilation typically occurs, making it difficult to separate the
relative contributions of these effects on enhanced cardiac output. Right ventricular function can be
favorably impacted as these agents decrease pulmonary vascular resistance (comparable to
20 ppm of nitric oxide in cardiac surgery patients), thus improving forward flow. Coronary vessels
and arterial bypass grafts (internal mammary and gastroepiploic arteries and radial artery grafts)
become dilated; furthermore, in the presence of these drugs they are less subject to the
vasoconstrictive effects of concomitantly administered a-adrenergic agonists.
What untoward effects can result from use of phosphodiesterase inhibitors?
How are these minimized?
Because the vasodilator effects may be profound, concurrent use of vasoconstrictors
(e.g., epinephrine, norepinephrine, and phenylephrine) is often necessary, particularly after
cardiopulmonary bypass. Prolonged infusion of amrinone, but not milrinone, may cause significant
thrombocytopenia through nonimmune-mediated peripheral platelet destruction.
Cardiac conditions (active) that require special consideration before anaesthesia
Active cardiac conditions are serious cardiac conditions that warrant immediate evaluation and
treatment before undergoing surgery. There are four active cardiac conditions:
1. Unstable coronary syndromes, which include unstable or severe angina and recent
myocardial infarction
2. Decompensated heart failure
3. Significant arrhythmias such as symptomatic ventricular arrhythmias, high-grade
atrioventricular block, and symptomatic bradycardia
4. Severe valvular disease such as symptomatic mitral stenosis or severe aortic stenosis
What nerves may be affected from lithotomy positioning?
n Femoral nerve: A reasonable practice is to avoid hip flexion >90 degrees, although it
remains a matter of debate whether extreme flexion predisposed the patient to a femoral
neuropathy. The femoral nerve is also at risk from pelvic retractors.
n Common peroneal nerve: May be injured when the head of the fibula is insufficiently padded
and compressed against the stirrup canes.
n Sciatic nerve: Avoid stretching the hamstring muscle group by avoiding hip flexion
>90 degrees.
n Saphenous nerve: May become injured if the medial tibial condyle is compressed.
n Obturator nerve: May be stretched as it exits the obturator foramen during thigh flexion.
n Lateral femoral cutaneous nerve: Would always present with only sensory findings.
What is the role of positive end-expiratory pressure?
PEEP has been a cornerstone in the management of respiratory failure for over 40 years.
Specifically it is applied to the exhalation circuit of the mechanical ventilator. The main goals of
PEEP are to:
n Increase functional residual capacity by preventing alveolar collapse and recruiting
atelectatic alveoli.
n Decrease intrapulmonary shunting.
n Reduce the work of breathing.
PEEP adjustments should be considered in response to periods of desaturations (after
common causes for hypoxemia have been ruled out) such as mucous plugging and
barotrauma) to assess recruitment potential.
What are the side effects of PEEPe and PEEPi?
n Barotrauma may result from overdistention of alveoli.
n Cardiac output may be decreased because of increased intrathoracic pressure, producing an
increase in transmural right atrial pressure and a decrease in venous return. PEEP also increases
pulmonary artery pressure, potentially decreasing right ventricular output. Dilation of the right
ventricle may cause bowing of the interventricular septum into the left ventricle, thus impairing
filling of the left ventricle, decreasing cardiac output, especially if the patient is hypovolemic.
n Incorrect interpretation of cardiac filling pressures. Pressure transmitted from the alveolus
to the pulmonary vasculature may falsely elevate the readings.
n Overdistention of alveoli from excessive PEEP decreases blood flow to these areas,
increasing dead space (VD/ VT).
n Work of breathing may be increased with PEEP because the patient is required to generate a
larger negative pressure to trigger flow from the ventilator.
n Increase in intracranial pressure (ICP) and fluid retention
