Conclusions
+ Compared with 6% hetastarch in saline, Hextend, was effective at
treating hypovolemia. In fact, treatment goals were more commonly
achieved and heart rate was better maintained in Hextend treated
patients.
+ Hextend was as safe as 6% hetastarch in saline as judged by the
incidence of adverse events.
+ These data suggest that Hextend has more favorable effects on
coagulation compared with 6% hetastarch in saline. This finding
warrants further study.
Excuse me but where does it say "that the reduced blood loss
in the Hextend arm can be explained by the continuous calcium infusion with Hextend.
Eureka!"? The separate observations
+ Hextend treated patients had higher ionized calcium measurements
even though they required calcium therapy less often (Table 4).
AND
+ There were fewer study-drug related bleeding complications in
Hextend treated patients.
were two of many observations noted in the results section of the study. Nowhere in the
poster publication are those two observations linked by cause and effect by the authors.
Homeboy says: <<Parenthetically, this issue resembles the post-op heart rate results, i.e.,
statistically significant differences without any clinical implication whatsoever.>>
No clinical implications? The study was designed to assess the efficacy (and safety) of
Hextend as a volume expander in the treatment of hypovolemia as compared with the gold
standard, hespan. The hemodynamic parameters measured to determine efficacy were
heart rate, blood pressure, and urine output. An elevated heart rate is a clinically significant
sign of hypovolemia. What more clinically significant hemodynamic parameters would you
have
suggested?
Homeboy says: <<All that said, then why do surgeons administer an ampoule of calcium
during surgery in those patients who have bled significantly? The answer is rather simple. It
is the citrate in transfused blood, which is routinely used as an anticoagulant when the blood
is donated, that binds serum calcium.>>
After your long-winded explanation of why calcium plays such a minute, if any, role in
blood coagulation, I find it ironic that you point out that the anticoagulant used in donated
blood acts by binding calcium. Also, you imply that the amount of calcium administered
during surgery is dependent exclusively on the amount of anticoagulated blood
administered. If that were the case, why did so many more hespan patients require calcium
administration
than Hextend patients in this double-blinded trial despite requiring only a slightly (and a
statistically insignificant) greater quantity of anticoagulated blood product?
Homeboy says: <<Furthermore, for the isolated clinical occasions where intravenous
calcium is required, physicians can administer a very
inexpensive and readily obtainable ampoule of calcium to whichever volume replacement
solutions they choose.>>
So you and your cohorts have said ad nauseum. But the fact remains the study participants
did have IV calcium available to use and did use it much more frequently (in this
double-blinded study) in the hespan patients. Still, the hespan arm (and not some subgroup
thereof) had a statistically significant higher incidence bleeding complications. So no, it's not
as simple as adding calcium to hespan or giving calcium in addition to hespan, and BTIM
never said it was just the calcium. You guys keep saying that. Hextend's aqueous
component is not simple saline solution with calcium added, but a more complex solution of
salts, sugars, buffers etc, that more closely mimics the chemistry of natural human plasma
than does hespan's saline solution. Preclinical and clinical studies have shown that Hextend
does not cause coagulation problems beyond those expected by simple dilution. Hespan's
dose limiting association with bleeding complications, with or without a "readily obtainable
ampoule (sic) of calcium", is well known. |
