Beneficial effects of alkaline phosphatase in septic shock
Fuhong Su, MD; Ruud Brands, PhD; Zhen Wang, MD; Colin Verdant, MD; Alejandro Bruhn, MD;
Ying Cai, MD; Willem Raaben, MD; Marty Wulferink, PhD; Jean-Louis Vincent, MD, PhD, FCCM
L
ipopolysaccharide (LPS) can be
detected in the blood of up to
78% of patients with severe
sepsis (1). This is associated
with higher mortality rates, and removal
of LPS has been viewed as a possible ap-
proach to improve patient outcome from
sepsis (2). Alkaline phosphatase is a consti-
tutive ecto-enzyme present in different tis-
sues (3) with different activities. Alkaline
phosphatase has several natural substrates,
including phosphoethanolamine, inorganic
phosphate, and pyridoxal 5'-phosphate (4).
Alkaline phosphatase can also convert lipid
A (5), the main toxic part of LPS, to mono-
phosphoryl lipid A, which is virtually non-
toxic in vitro and in vivo (6). Pretreatment
with monophosphoryl lipid A even reduced
endotoxin-induced mortality in the rat (7).
Some studies in rodents have suggested
a protective role of alkaline phosphatase in
sepsis. Poelstra et al. (6, 8) demonstrated
that renal alkaline phosphatase extracts
limited the localized intradermal inflam-
matory reaction elicited by LPS injection in
rats. These authors also reported that le-
vamisole, an inhibitor of intestinal alkaline
phosphatase, increased mortality in a rat
intraperitoneal Escherichia coli sepsis
model (6, 8). Other studies have indicated
that exogenous administration of placental-
alkaline phosphatase improves survival in
mouse endotoxemia (9) and intraperitoneal
E. coli models (10). However, recently van
Veen et al. (11) showed that alkaline phos-
phatase administration did not improve
survival in a mice model of cecal ligation
and puncture (CLP), despite an attenuated
inflammatory response.
The goal of the present study was to
investigate the effect of administration of
alkaline phosphatase on mortality and out-
come in a clinically relevant model of septic
shock secondary to peritonitis (12, 13).
METHODS
The study was conducted in accordance
with the guidelines established by the Institu-
tional Review Board for animal care of the
Free University of Brussels. Care and handling
of the animals were in accordance with Na-
tional Institutes of Health guidelines (Insti-
tute of Laboratory Animal Resources). Four-
teen female sheep (27.6 3.9 kg) were fasted
for 24 hrs with free access to water before the
experiment.
Instrumentation. On the day of the exper-
iment, the animals were initially weighed, pre-
medicated with intramuscular midazolam
(Dormicum, Roche, Attikis, Greece; 0.25 mg/
kg) and ketamine hydrochloride (Imalgine,
Merial, Lyon, France; 20 mg/kg), and placed in
the supine position. The cephalic vein was
cannulated with a peripheral venous 18-gauge
catheter (Surflo IV Catheter, Terumo, Bel-
gium). Following intravenous administration
of fentanyl (Janssen, Berchem, Belgium; 30
g/kg) and pancuronium bromide (Pavulon,
Organon, Oss, the Netherlands; 0.1 mg/kg),
the trachea was intubated (tracheal tube, 8.0;
Hi-Contour, Mallinckrodt Medical, Ireland).
Mechanical ventilation was started in con-
trolled volume mode (Servo Ventilator 900 C,
Siemens-Elema, Sweden) with a tidal volume
of 9 mL/kg, a positive end-expiratory pressure
of 5 cm H
2
O, an FIO
2
of 1, an inspiratory-
expiratory time of 1:2, and a square wave pat-
tern. Respiratory rate was adjusted to main-
tain end-tidal carbon dioxide pressure (47210
A Capnometer, Boehlingen, Germany) be-
tween 35 and 45 mm Hg. A 60-cm plastic tube
(inner diameter 1.8 cm) was inserted into the
stomach to drain its content and prevent ru-
men distension. A Foley catheter (14-Fr,
Beiersdorf AG, Germany) was placed to mea-
sure urine output. The right femoral artery
From the Department of Intensive Care, Erasme
Hospital (FS, ZW, CV, AB, JLV) and the Diabetes Centre
(YC), Free University of Brussels, Belgium; and IRAS,
Department of Immunotoxicology, University Utrecht,
Utrecht, The Netherlands (RB, WR, MW).
Supported, in part, by PharmAAware Sepsis, The
Netherlands, which kindly provided the alkaline phos-
phatase.
The authors have not disclosed any potential con-
flicts of interest.
Copyright © 2006 by the Society of Critical Care
Medicine and Lippincott Williams & Wilkins
DOI: 10.1097/01.CCM.0000229887.70579.29
Objective: Alkaline phosphatase may decrease the harmful ef-
fects of lipopolysaccharide by detoxifying lipid A. The aim of this
study was to investigate whether administration of alkaline phos-
phatase is beneficial in a clinically relevant septic shock model.
Design: Interventional laboratory study.
Setting: University hospital animal research laboratory.
Subjects: Fourteen fasted, anesthetized, invasively monitored,
mechanically ventilated, female sheep (27.6 3.9 kg).
Interventions: Each animal received 1.5 g/kg body weight of
feces intraperitoneally to induce sepsis. Ringer’s lactate and a 6%
hydroxyethyl starch solution were infused throughout the experiment
to prevent hypovolemia. Two hours after feces injection, animals
were randomized to alkaline phosphatase (60 units/kg intravenous
bolus followed by a continuous infusion of 20 units/kg/hr for a total
of 15 hrs) or no alkaline phosphatase (control group).
Measurements and Main Results: All animals were studied until
their spontaneous death or for a maximum of 30 hrs. Plasma alkaline
phosphatase concentrations decreased in the control group but in-
creased in the treatment group following alkaline phosphatase ad-
ministration. In the treatment group, the PaO
2
/FIO
2
ratio was higher
(p < .05), blood interleukin-6 concentrations were lower (p < .05),
and the survival time was longer (median time 23.8 vs. 17 .0 hrs,
p < 0.05) than in the control group. There were no significant
differences in systemic hemodynamics or diuresis.
Conclusions: In this clinically relevant septic shock model, alka-
line phosphatase administration improved gas exchange, decreased
interleukin-6 concentrations, and prolonged survival time. (Crit Care
Med 2006; 34:2182–2187)
KEY WORDS: peritonitis; lipopolysaccharide; gas exchange; sheep
2182 Crit Care Med 2006 Vol. 34, No. 8