CLINICAL PHARMACOLOGY
Action
GELFOAM has hemostatic
properties. While its mode of action is not fully understood, its effect
appears to be more physical than the result of altering the blood clotting
mechanism.
When not used in excessive
amounts, GELFOAM is absorbed completely, with little tissue reaction. This
absorption is dependent on several factors, including the amount used, degree
of saturation with blood or other fluids, and the site of use. When placed in
soft tissues, GELFOAM is usually absorbed completely in from four to six weeks,
without inducing excessive scar tissue. When applied to bleeding nasal, rectal
or vaginal mucosa, it liquefies within two to five days.
Animal Pharmacology
Surface-acting hemostatic devices, when applied directly
to bleeding surfaces, arrest bleeding by providing a mechanical matrix that
facilitates clotting.6,8,13,14 Due to their bulk, surface-acting
hemostatic agents slow the flow of blood, protect the forming clot, and offer a
framework for deposition of the cellular elements of blood.6,7,8,13 MacDonald
and Mathews12 studied GELFOAM implants in canine kidneys and reported
that it assisted in healing, with no marked inflammatory or foreign-body reactions.
Jenkins and Janda13 studied the use of GELFOAM
in canine liver resections and noted that the gelatin sponge appeared to offer
a protective cover and provide structural support for the reparative process.
Correll et all14 studied the histology of
GELFOAM Sterile Sponge when implanted in rat muscle and reported no significant
tissue reaction.
Clinical Studies
GELFOAM Sterile Powder is a water-insoluble, hemostatic
device prepared from purified skin gelatin, and capable of absorbing up to 45
times its weight of whole blood.4 The absorptive capacity of GELFOAM
is a function of its physical size, increasing as the amount of the gelatin
powder increases.5
The mechanism of action of surface-mediated hemostatic
devices is supportive and mechanical.5 Surface acting devices, when
applied directly to bleeding surfaces, arrest bleeding by the formation of an
artificial clot and by producing a mechanical matrix that facilitates clotting.6
Jenkins et al7 have theorized that the clotting effect of GELFOAM
may be due to release of thromboplastin from platelets, occurring when platelets
entering the sponge become damaged by contact with the walls of its myriad of
interstices. Thromboplastin interacts with prothrombin and calcium to produce thrombin,
and this sequence of events initiates the clotting reaction. The authors suggest
that the physiologic formation of thrombin in the sponge is sufficient to produce
formation of a clot, by its action on the fibrinogen in blood.7 The
spongy physical properties of the gelatin sponge hasten clot formation and
provide structural support for the forming clot.6,8
Several investigators have claimed that GELFOAM becomes
liquefied within a week or less and is completely absorbed in four to six
weeks, without inducing excessive scar formation.4,7,9,10,11 Barnes10
reviewed experiences with GELFOAM in gynecologic surgery. No excessive scar
tissue, attributable to the absorption of GELFOAM, could be palpated at
postoperative examination.
Bone Hemostasis Study
The efficacy of GELFOAM Sterile Powder as a bone
hemostatic agent during cardiopulmonary bypass surgery was evaluated.
Study Design
Two randomized open-label clinical studies were conducted
at separate investigative sites. The objectives were as follows:
- To evaluate the effectiveness of GELFOAM Sterile Powder
as a hemostatic agent in the treatment of sternal bone bleeding during
cardiopulmonary bypass surgery.
- To identify any deleterious effects of GELFOAM Sterile
Powder on interference with bone healing.
- To determine any systemic or local wound side effects
from leaving GELFOAM Sterile Powder in situ.
Patients between the ages of 18 to 74 years old undergoing
cardiopulmonary bypass surgery were randomly assigned to either a GELFOAM group
or a Control group. The GELFOAM group (composed of 108 patients) had a paste
made up of sterile saline solution and GELFOAM Sterile Powder applied to the
cut sternal surface immediately following sternotomy. The Control group
(composed of 107 patients received no treatment applied to the cut surface.
Blood loss was monitored both during surgery and
postoperatively. Blood loss during surgery was determined by measuring the weight
of the powder before and after application to the cut edge of the sternum.
Postoperative blood loss was collected from the mediastinal drainage tubes. The
total blood loss (in milligrams) over 72 hours was determined for each patient.
Study Endpoints
Patients were evaluated upon admission (preoperative),
during surgery (intraoperative), after surgery (postoperative), upon hospital
discharge (7 to 10 days after surgery), and at the 3-month follow-up visit. An
additional poststudy follow-up was required if a patient reported an ongoing
medical event at the 3-month follow-up visit.
Study Results
In both studies, the amount of blood loss was
significantly less in the GELFOAM group than in the Control group. In Study
001, the mean blood loss in the GELFOAM group was 13727.7 mg while the mean
blood loss in the Control group was more than double at 27712.0 mg. Similar
results were found in Study 002, where the mean blood loss in the GELFOAM group
was 9514.8 mg while the mean blood loss in the Control group was 22687.5 mg.
Table 2: Blood Loss in Sternotomy Patients
|
Site 001 |
Site 002 |
GELFOAM |
Control |
GELFOAM |
Control |
Mean Blood Loss (mg) |
13727.7 |
27712.0 |
9514.8 |
22687.5 |
Median Blood Loss (mg) |
11561.0 |
24798.0 |
6950.0 |
16900.0 |
Minimum Blood Loss (mg) |
2922.0 |
10748.0 |
800.0 |
900.0 |
Maximum Blood Loss (mg) |
87448.0 |
61535.0 |
46000.0 |
89800.0 |
Patients in the GELFOAM and Control groups were similar
with regard to sterna bone healing. At hospital discharge, normal bone healing
was reported for 105 patients (97%) in the GELFOAM group and 104 patients (97%)
in the Control group. At the 3-month follow-up, 103 patients (95%) in the
GELFOAM group and 100 patients (93%) in the Control group were healed.
Few patients in either treatment group had sternotomy
infection or other postoperative infection complications related to sternotomy.
At hospital discharge, two patients treated with GELFOAM had mediastinitis. No
Control patients had any infections at hospital discharge. One patient treated
with GELFOAM had a non-infection related complication.
At the 3-month follow-up, one of the original patients
treated with GELFOAM who had mediastinitis still showed signs of infection. In
addition, two additional patients treated with GELFOAM developed mediastinitis
at the 3-month follow-up.
One patient in the Control group experienced sternal
osteomyelitis at the 3-month follow-up but recovered with no residual effects.
No patients from the GELFOAM arm of the study had reported complications of
sternal osteomyelitis.
There was a total of four Control patients who had
non-infection-related complications.
One Control patient had serous/sanguineous wound drainage
from the left leg and sternum incisions at hospital discharge. This
complication was non-infectious and the patient recovered with no residual side
effects.
Three Control patients all experienced chronic pain
syndrome, a symptom which can occur following thoracic/cardiac surgery.
Evaluation sternal bone healing at the 3-month follow-up for these patients
showed no evidence of non-union of the sternum. In all three cases, bone
healing at the 3-month follow-up was reported as being normal. A summary of
sternotomy infection information is located in Table 3.
Table 3: Summary of Postoperative Infection
Complications
|
Hospital Discharge |
3-Month Follow-up |
GELFOAM |
Control |
GELFOAM |
Control |
N |
% |
N |
% |
N |
% |
N |
% |
Any Infection |
yes |
1 |
(1) |
0 |
(0) |
5 |
(5) |
0 |
(0) |
no |
104 |
(99) |
106 |
(100) |
95 |
(95) |
105 |
(100) |
Superficial Wound |
yes |
0 |
(0) |
0 |
(0) |
2 |
(2) |
0 |
(0) |
no |
105 |
(100) |
106 |
(100) |
98 |
(98) |
105 |
(100) |
Sternal Osteomyelitis |
yes |
0 |
(0) |
0 |
(0) |
1 |
(1) |
1 |
(1) |
no |
105 |
(100) |
106 |
(100) |
99 |
(99) |
105 |
(99) |
Mediastinitis |
yes |
1 |
(1) |
0 |
(0) |
2 |
(2) |
0 |
(0) |
no |
104 |
(99) |
106 |
(100) |
98 |
(98) |
105 |
(100) |
Complication Related to Sternotomy |
yes |
0 |
(0) |
0 |
(0) |
1 |
(1) |
3 |
(3) |
no |
105 |
(100) |
106 |
(100) |
99 |
(99) |
102 |
(97) |
Study Conclusions
These studies demonstrate that a paste made from GELFOAM
Sterile Powder is safe and effective in treating intraoperative bleeding when
applied to the cut surface of cancellous bone and has shown superior hemostasis
versus no treatment at all to the cut bone surface. The benefit to patients is
that a reduction in bleeding will make surgery easier to perform by reducing
the time the surgeon needs to revisit cut bone surfaces to clean up the
bleeding. This study also demonstrated that GELFOAM Sterile Powder could be
left in situ without increased risk of bone infection or nonunion of the
sternum.
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