Microbubble contrast agents: a new era in ultrasound

Sir,
A growing interest has been raised by microbubble contrast agents for
transabdominal ultrasonography (US) which allows detecting and
characterizing hepatic focal lesions as well as controlling the effect of
loco-regional therapies in the short term. Our experience with this
investigation shows very high values of sensitivity and specificity when
spiral computered tomography is used as gold standard with an impressive
gain in comparison to conventional transabdominal US. Controindications of
US with counter agent are few and rare and the method is considered to be
safe even when used in patients with chronic organ failure. For these
reasons, we believe of interest to report the case of a life threatning
event observed during the performance of this investigation.

A 77 year old female patient was admitted to our Unit for the onset
of ascites and oedemas at lower limbs. Physical examination revealed
hepatomegaly and laboratory tests showed mild anemia and marked increase
(7.2 times) of g-glutamil-transpeptidase. Conventional US demonstrated a
picture of a chronic liver disease with a dishomogeneous ultrasonographic
pattern associated to a focal lesion (14 x 10 cm) whose nature was decided
to be better defined with the use of a counter agent (Sono-Vue, Bracco –
Italy). Additionally, the patient was affected by chronic disorders such
as obstructive pulmonary disease, hypertension, atrial fibrillation and
diabetes. All these diseases did not represent active clinical problems at
the moment of hospitalization, since an appropriate medical treatment was
assumed.

About 5 minutes after the injection of 4.8 ml of Sono-Vue diluted in
saline solution, acute severe dyspnea and fall of blood pressure until
undetectable values occurred. Basic life support manouvres associated to
steroid and plasma expander intravenous administration allowed reaching a
normalization of cardiac and respiratory functions within 20 minutes.
Successively, a complete restoration of general conditions was observed.

This case suggests that Sono-Vue administration and acute cardio-
respiratory failure could be related, since the onset of the event
directly followed the injection. Nevertheless, our observation regards
only one patient with chronic disorders, which may represent a confounding
variable, whose role cannot be clearly adrressed. Indeed, Sono-Vue leaflet
reports that special care should be taken in patients with hearth failure
and lung diseases with breath shortage. Nevertheless, the bases of these
recommandations are only theoretically hypothesized and not supported by
clinical evidences. In fact, the safety of this counter agent has been
assessed in a large series of patients with chronic hearth disorders and
obstructive pulmonary disease. In these last subjects, Sono-Vue did not
change the results of respiratory function tests.
On these bases, although a direct relationship between Sono-Vue
administration and the onset of the event we observed cannot be clearly
established, our report has the aim to alert the readers and stimulate
them to describe similar cases for a better knowledge not only of the
possibilities of US with contrast agents but of its limits too.

Competing interests:
None declared