CONTACT: JENNIFER CRONIN
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-5661; fax (319) 335-9917
Release: April 8, 1999
UI researcher determines vital sign norms for cesarean
IOWA CITY, Iowa -- A University of Iowa researcher, with
data and assistance from Duke University, has found that it is quite normal
for blood pressures in women to drop or increase dramatically during cesarean
Using records of 1,300 women who had cesarean sections,
Franklin Dexter, M.D., Ph.D., UI associate professor of anesthesia, and Duke
researchers sought to establish how vital signs changed during such deliveries.
The investigators are among the first to look at how anesthetics affect vital
signs during a surgical procedure. Because anesthetics are safe, nobody had
felt the need to establish surgery vital sign benchmarks.
"People talk about normal blood pressure being 120/80
millimeters mercury, which results in an average blood pressure of 100 millimeters
mercury," said Dexter, the principal investigator for the analysis. "But,
in women with high blood pressures who have regional anesthesia and are awake
when their babies are born, the decrease in the average blood pressure with
the start of anesthesia can be as much as 70 millimeters mercury."
In healthy women who have general anesthesia and are asleep
when their babies are born, the average blood pressure with the start of anesthesia
can increase to as much as 160 millimeters mercury, Dexter added.
"What's dramatic is very large changes in blood pressure
occur in the operating room yet women and their babies do well," he said.
Duke researchers contacted Dexter to perform the record
analysis because the institution wanted to see if there was a way to improve
patient outcomes. Duke researchers also understood that establishing acceptable
levels for surgery could have important implications in malpractice cases.
Duke University is unique because it has used an automated information system
for collecting vital sign information during all of its anesthetics, including
cesarean sections, for many years.
Although malpractice involving cesarean sections is not
a huge problem, vital sign reference limits may play a role in such cases
when an expert, using recorded vital signs as evidence, claims that an anesthesiologist's
care was substandard. Until now, experts have relied on their own clinical
judgment to estimate reference limits. Dexter's analysis of the data from
Duke provides a benchmark to either confirm or refute these claims.
"The importance in terms of malpractice cases is that
when you see very large, seemingly abnormal changes in vital signs in the
operating room, it does not necessarily indicate that care has somehow been
substandard," Dexter said.
Dexter examined records from 1,300 women who underwent
cesarean section at Duke with general or spinal anesthesia between April 21,
1992 and July 9, 1997. Dexter and his associates evaluated normal values for
the minimum and maximum heart rate, oxyhemoglobin saturation, minimum and
maximum mean arterial pressure, and increases and decreases in mean arterial
Dexter's work appears in a recent issue of the Journal
of Clinical Monitoring and Computing.