Vasoactive Drugs in Intensive Care Unit

Shock, defined by inadequate tissue perfusion, is a common problem in critically ill
patients. Most patients who have shock have hypotension and this is typically treated
initially with intravenous fluid resuscitation in patients who are fluid responsive. If
patients remain hypotensive, they are typically treated with vasoactive medications. Four of
the commonly used FDA approved vasoactive medications are norepinephrine, phenylephrine,
epinephrine, and vasopressin. Apart from a 2010 trial comparing norepinephrine to dopamine,
there are no studies to date that have shown one of the four above-mentioned vasoactive
medications to be superior to another. Accordingly, choice of vasoactive medication is based
upon individual physician preference, without an outcomes-related evidence base.

Two of the four above mentioned vasoactive medications (norepinephrine and epinephrine) have
chronotropic effects (i.e. the tendency to increase heart rate), while the other two
(phenylephrine and vasopressin) have less of a propensity to chronotropy. The potential
benefits of the chronotropic effects in patients with shock (increasing cardiac output) are
offset by the potential detriments (predilection to tachydysrhythmias and myocardial
ischemia).

Recent evidence suggests that tachydysrhythmias are associated with worse outcomes in ICU
patients. One study demonstrated that administration of the beta blocking agent esmolol
improved hemodynamic outcomes and survival in patients with septic shock. It is not clear if
a vasoactive drug regimen that utilizes phenylephrine and vasopressin will be associated with
lower heart rates compared to a regimen that utilizes norepinephrine and epinephrine.

The investigators hypothesis is that for ICU patients with shock, the use of the vasoactive
drugs phenylephrine and vasopressin will reduce tachydysrhythmias when compared to
norepinephrine and epinephrine. To investigate this hypothesis, we are conducting a
randomized double blind controlled trial comparing phenylephrine and vasopressin vs.
norepinephrine and epinephrine in ICU patients with shock that is not responsive to IV
fluids. All patients admitted to the adult intensive care units at the University of Chicago
will be screened for eligibility.

Patients will be randomized to receive either phenylephrine (0.3-3.0 mcg/kg/minute), with the
addition of vasopressin (0.1-0.6 milliunits/kg/minute) if a second vasopressor is required,
or norepinephrine (0.03 to 0.3 mcg/kg/minute), with the addition of epinephrine (0.03 to 0.3
mcg/kg/minute) if a second vasopressor is required. These drugs will be mixed and blinded by
the research pharmacy. Only the research pharmacist will know the identity of the particular
vasoactive drug. As per current standard practice, the medical team in charge of the patient
will determine the target blood pressure.

In either group, if two vasoactive drugs are not adequate to raise the blood pressure to the
target level, open-label norepinephrine will be added. If three vasoactive drugs are
inadequate to raise the blood pressure to the target level, open-label epinephrine will be
added.

There will be up to a twelve-hour period from initiation of standard, non-study vasoactive
support during which the patient can be consented and enrolled. This will allow the research
team to contact the patient and/or family in order to obtain informed consent. Once
randomized, all patients will be initiated on study drug vasoactive support at 50 percent of
the maximal infusion rate. The study drug will be titrated to maintain blood pressure and the
initial non-study drug will be titrated off. The primary team will direct other aspects of
patient care.

We plan to examine the following pre-specified sub-groups:

1. Patients who received corticosteroids during their ICU stay vs. patients who did not
receive corticosteroids during their ICU stay

2. Patients with depressed left ventricular ejection fraction (< 40%) vs. patients with
normal left ventricular ejection fraction

3. Patients with coronary artery disease vs. patients without known coronary artery disease

4. Patients with different etiologies of shock (i.e. septic, cardiogenic, hypovolemic)

Inclusion Criteria:

1. Age greater than or equal to 18 years old

2. Requirement for vasoactive drugs via a central venous catheter for the treatment of
shock. Shock will be defined as mean arterial pressure less than 70 mmHg or systolic
blood pressure less than 100 mmHg despite administration of at least 1000 mL of
crystalloid or 500 mL of colloid, unless there is an elevation in the central venous
pressure to > 12 mmHg or in the pulmonary artery occlusion pressure to > 14 mmHg
coupled with signs of tissue hypoperfusion (e.g. altered mental state, mottled skin,
urine output < 0.5 mL/kg body weight for one hour, or a serum lactate level of > 2
mmol per liter).

Exclusion Criteria:

1. Cardiopulmonary arrest

2. Pregnancy

3. Severe right heart failure