DELIVERING ANESTHESIA TO THREE PEOPLE AT ONCE: A NEW CHALLENGE
NEW ORLEANS -- Although a mounting body of evidence points to the benefits of regional anesthesia versus general anesthesia for many types of surgery, when it comes to fetal surgery on twins for a rare but potentially fatal condition called twin-twin transfusion syndrome (TTTS), general anesthesia exhibits some notable advantages over regional techniques.
This includes less stress on the twins and less anxiety for the mother, according to researcher Laura B. Myers, M.D., an anesthesiologist at the Children's Hospital of Philadelphia.
TTTS is a condition marked by abnormal connections between the placenta of twins and often results in the delivery of too much blood to one twin and too little to the other. The illness produces severe anemia in the twin receiving less blood, but taxes the heart of the twin receiving more.
Although TTTS puts both fetuses at serious risk, it affects the anemic twin more seriously. Without treatment, 60 to 80 percent of twins die, and those who survive without intervention have an elevated risk of developmental delays.
A procedure called selective fetoscopic laser photocoagulation (SFLP), pioneered five years ago at the University of California-San Francisco (UCSF) and performed today at UCSF, Vanderbilt University and the Children's Hospital of Philadelphia, allows fetal surgeons to remedy these abnormalities in utero during the pregnancy.
Using ultrasound images for guidance, the surgeon inserts a rounded instrument called a trocar into a small incision in the uterus. The trocar acts as a port for the insertion of a laser and other instruments to correct the twins' blood flow imbalance.
According to the results of a retrospective study of 17 patients who underwent SFLP at the Children's Hospital of Philadelphia from 1996 to 2001, both regional and general anesthesia offer safe, effective anesthetic options. Women who received regional blocks differed from women who received general anesthesia only in the amount of fluid such as saline, or salt solution, they required during surgery, Dr. Myers said.
But SFLP can cause considerable anxiety for the mother because two fetuses' lives are at stake. If the mother receives regional anesthesia and then becomes very anxious during the two- to three-hour surgery, the anesthesiologist may have to sedate her, and sedation increases the risk of aspiration in pregnant patients.
Regional anesthesia involves the insertion of a thin, plastic catheter into the epidural space, which is close to the spinal cord. Numbing medication is given through the catheter so that the mother remains awake but feels no sensations from the lower chest down. By contrast, general anesthesia involves putting the mother to sleep and inserting a breathing tube down her throat. The inhaled anesthetic used to keep the mother asleep during surgery also crosses over to the placenta, anesthetizing the twins. The twins move less, making corrective surgery easier.
General anesthesia also has advantages for women carrying twins toward the front of the uterus rather than toward the back. Surgeons often have more difficulty inserting the trocar when the placenta is near the front, so the mother often has to lie on her side or in another uncomfortable position for the safe insertion of the instruments. "In these cases, it's better for the mother to be asleep right from the start," Dr. Myers said.
"We need to study these patients prospectively to learn more about the best ways to manage their care," she said.
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