Conjoined twins are two humans who are born physically connected to each other.1 They develop when an early embryo only partially separates; though two fetuses develop from the embryo, they remain physically connected and may share multiple internal organs.1 Conjoined twins can be attached at various sites: via the chest (thoracopagus), abdomen (omphalopagus), base of the spine (pygopagus), length of the spine (rachipagus), pelvis (ischiopagus), trunk (parapagus), head (craniopagus; such twins may share some brain tissue, but have mostly separate brains) and head and chest combined (cephalopagus; such twins share an entire brain and rarely survive).1 Heteropagus twins are asymmetrically conjoined twins in which one twin, who has severely defective tissues, is dependent on the cardiovascular system of the other twin.2 Conjoined twins must often be separated given the inconvenience and often harmful nature of their connection, though separation is usually delayed until six months to one year of age to improve survival rates.3 Surgical separation of conjoined twins requires complex anesthetic management, which has been a focus of study for over 60 years.4,5 Anesthesia provision for conjoined twins is especially difficult because the anesthesiology practitioner must care for two patients at the same time, rather than one.6 The anesthesia provider must take precautions before, during and after surgery in order to limit complications and ensure success.
When elective separation (i.e., nonemergency) surgery is possible, the anesthesiologist is responsible for meticulous preoperative preparation.7 First, the anesthesia provider, along with a multidisciplinary team of health professionals, should determine the timing of the operation and separation plan based on the patients’ circumstances and shared organs.8 Depending on the complexity of the patients’ condition, two anesthesia providers and two complete anesthesia teams will likely be necessary.3,9 The anesthesia teams should focus preoperative planning on avoiding overcrowding and arranging the surgical space for optimal medication administration and monitoring.10 Also, preoperative preparation includes selection of appropriate anesthesia. The anesthesiologist should assess the circulatory and other anatomical connections between the patients with imaging,11 as these connections could influence the effects of anesthetic drugs.12,13 Anesthesia administration for conjoined twins must be well-planned, as it may involve multiple rounds of medication. For example, in one study of the separation of omphalopagus twins, the twins had to be anesthetized twice: once for insertion of skin expanders, and later for surgical separation.13 Then, they were provided with combined caudal epidural-general anesthesia.13 Other studies show that general anesthesia with tracheal intubation may be preferable for conjoined twins undergoing surgical separation,10,14,15 and one surgery even used local anesthesia.12 Overall, the preoperative priorities for the anesthesia teams should include organization of the operating room and selection of appropriate anesthetic drugs.
Anesthesia providers’ intraoperative duties for conjoined twins are complicated, as they involve two sets of vital signs and two bodies. In a pair of thoracopagus twins undergoing cardiac evaluation, anesthesiologists needed to keep their ventilation in sync with a special mechanical adaptor.16 Depending on the connection between the twins, intraoperative airway management, vascular access and temperature maintenance may pose challenges.9,10 Anesthesiologists must also be aware of the risk of massive blood loss.10,12 Monitoring equipment must be duplicated in the operating room,9 and coordination between all members of the surgical team is vital to reduce overcrowding and prevent complications.10 Circulatory and respiratory connections between conjoined twins make vitals monitoring complex, and anesthesia providers need to stay vigilant in a busy surgical room.10
After surgery, the anesthesiologist will continue to provide support to the separated twins.12 Given the large fluid shifts and blood loss that can occur with extensive separation procedures, anesthesia providers will need to replenish fluids and blood as quickly as possible after surgery.6 Postoperative care also includes mechanical ventilation, regulation of electrolyte balance, infection prevention and maintenance of hemodynamic stability.12 Anesthesia providers should also work with the rest of the medical team to plan for patients’ postoperative rehabilitation and potential reconstruction surgeries.10
Conjoined twins present unique challenges that may inform an anesthesiologist’s practice. Anesthesiology practitioners are responsible for preoperative evaluation of the patients’ organs, circulation and respiration; planning and organization of two anesthesia teams; monitoring intraoperative vital signs for patients who share various organ systems; and postoperative care that includes ventilation and fluid replenishment. Though prevalence of conjoined twins is only 1.47 per 100,000 births,17 anesthesia providers must do extensive research and preparation to provide medication during a surgical separation.
1. Mayo Clinic. Conjoined twins. Diseases & Conditions 2019; https://www.mayoclinic.org/diseases-conditions/conjoined-twins/symptoms-causes/syc-20353910.
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