Massachusetts General Hospital (MGH)
researchers have found that medications currently used to immobilize
patients during surgery can increase the risk of postoperative
respiratory complications. Their study being published online in the
journal BMJ also found that the agent most commonly used to reverse
the action of the immobilizing drug does not prevent and may
possibly increase the risk that patients will need to receive
postoperative respiratory support.
"Neuromuscular blocking agents are used
during surgery for a variety of reasons, including allowing
placement of a breathing tube and preventing patients from moving
during a procedure, says Matthias Eikermann, MD, PhD, director of
Research in the Critical Care Division of the MGH Department of
Anesthesia, Critical Care and Pain Medicine, senior author of the
BMJ report. "Unfortunately, these agents do not stop working
immediately at the end of surgery, leading to residual muscle
weakness which can decrease postoperative respiratory function. Our
findings suggest that we need to develop better blocking agents and
improved methods of monitoring their effects."
Drugs that prevent transmission of
signals from nerves to muscles are commonly used in surgical
patients and in intensive care patients on mechanical ventilators.
Long-acting neuromuscular blocking agents can increase the risk of
respiratory complications, so in recent years they have been
replaced with newer, intermediate-acting drugs.
Eikermann's team focuses on developing new strategies in general
anesthesia that can stablize and improve respiratory function.
Their previous work suggested that intermediate-acting agents may be
responsible for a high incidence of muscle weakness in patients
recovering from surgery, leading to respiratory difficulties that
lengthen a patient's time in the recovery room.
The current study analyzed data on
surgeries involving general anesthesia conducted at the MGH from
March 2006 to September 2010.
The researchers compared data on more
than 20,000 surgeries in which intermediate-acting neuromuscular
blocking agents were used with an equal number of procedures that
did not use the drugs, looking at recordings of patients' blood
oxygen levels after the removal of breathing tubes and whether it
became necessary to replace a breathing tube within 72 hours of
surgery, a procedure requiring intensive care unit admission.
They also analyzed the strategies used to monitor neuromuscular
function during surgery and whether a drug was administered that
reverses the action of the immobilization agent.
Their results showed that patients who
received intermediate-acting neuromuscular blocking agents had a 40
percent greater risk of requiring reintubation because of low blood
oxygen levels.
Functional monitoring of neuromuscular strength by means of visual
or tactile assessment of muscular response to an electric stimulus
had no significant effect on risk, but the use of the reversal agent
neostigmine made the risk of reintubation even greater.
Eikermann notes that patients with postoperative respiratory
complications have a significantly greater risk of death than those
without complications.
"Both neuromuscular blocking agents and
the blocker-reversing agent currently used have important roles in
perioperative medicine. But these medications have a narrow
therapeutic range and can have dangerous, unintended effects on the
respiratory system," says Eikermann, an associate professor of
Anaesthesia at Harvard Medical School. "The best way to reduce these
risks will be the development and use of shorter-acting
neuromuscular blockers and new reversal agents that directly halt
the effects of blocking agents." He and his team are currently
evaluating new reversal agents and interventions for preventing
perioperative respiratory complications.
Eikermann adds that the use of
monitoring equipment that can quantitatively measure neuromuscular
function, instead of the current qualitative estimates, should more
accurately reflect drug action, giving the kind of precise data
required to standardize procedures. His team is developing clinical
strategies to implement the type of monitoring that will help
anesthesia providers more appropriately dose and time the
administration of these powerful, necessary drugs.
Co-lead authors of the BMJ report are
Martina Grosse-Sundrup, MD, and Justin Henneman, MS, of the MGH
Department of Anesthesia, Critical Care and Pain Medicine.
Additional co-authors are Brian Bateman, MD, Jose Villa Uribe,
Nicole Thuy Nguyen and Elizabeth Martinez, MD, MGH Anesthesia;
Warren Sandberg, MD, and Jesse Ehrenfeld, MD, Vanderbilt University
School of Medicine; and Tobias Kurth, MD, Brigham and Women's
Hospital.
For more information
Massachusetts General Hospital
http://www.massgeneral.org/
(MDN) | 
