|
Anesthesia Considerations in
Rubinstein-Taybi Syndrome
Theodore W. Striker, M.D.
Anesthesia and Pediatrics
Children’s Hospital Medical Center
Cincinnati, Ohio
In order to address the anesthetic challenges associated with Rubinstein-Taybi syndrome (RTS) it is appropriate to discuss general principles of anesthesia involved.
The anesthetic experience involves consideration of psychological, physical, and physiologic factors, all of which must be controlled if one is to expect a successful outcome.
The incidence of anesthesia in infants and children in this country is approximately 9-10 million anesthetics per year. Patients with Rubinstein-Taybi syndrome constitute an infinitesimal fraction
of this population and by virtue of their rarity require meticulous attention to the details of the limited information available.
The physical challenges to the anesthetist are centered about three main areas: skeletal anomalies, airway anomalies and cardiac anomalies. The first major skeletal problem is that of craniofacial
dysmorphism. The anomaly includes problems of the maxilla or upper jaw. There are narrowing of the palate and poor development of and malpositioning of the mandible or lower jaw. These in turn cause a small
mouth and poor ability to open the mouth.
The next area of major skeletal problems involves the vertebral column. We see that cervical hyper-kyphosis (humpback) is present in 62% of patients, as well as scoliosis in 38% of patients in a
study of 45 patients with R.T.S. in the Netherlands (Hennekam et al).
Moving from skeletal anomalies, the next large category of challenge is that of congenital cardiac anomalies. The series of 175 patients of Sautarel et al in the chart cited by Stirt contains a
15% incidence of serious anatomic abnormalities. The anesthetic process can be directly affected by congenital cardiac anomalies and in turn can cause substantial risk in this group of patients.
The final area of anatomic differences from the norm consists of abnormal upper and lower airway narrowing and collapse. This has been referred to by Hennekam et al as a cause of ventilatory
problems in non-anesthetized subjects with RT. syndrome.
Turning to the challenges of anesthesia in these patients, it is appropriate to discuss the process of anesthesia by way of introduction. The process of anesthesia in infants, children or adults
entails the alteration of consciousness for the purpose of preventing or relieving the discomfort of procedures performed, maintenance of immobility in patients who are unable to cooperative, or alleviation of psychological
trauma involved with many forms of diagnoses and/or treatment. The overall categories of objectives of this process include safety, finite duration, predictability and acceptability.
The first objective: safety is of paramount importance. In anesthesia, the concept of Physical Status describes the general risk category into which an individual fits based on the presence or
absence of other problems. Studies of closed insurance claims have been effective in analyzing the demography of problems encountered in the anesthetic experience based on physical status classification.
Highest among incidence of problems with negative outcomes is the category of airway and ventilation. The patient with Rubinstein-Taybi syndrome can present a formidable challenge to anyone
assuring a patient’s airway. This occurs when the patient is anesthetized with relaxation of airway and diaphragmatic muscle activity as well as with depression of protective airway reflexes which serve to guard the lungs
against the entry of foreign material. There are both skeletal (bony) and soft tissue abnormalities as described earlier which jeopardize the airway in these patients.
As one is able to secure the airway, the problem of airway collapse (Hennekam) distal to the secured area can manifest itself. Such collapse can compromise passage of O2 and anesthesia to the lung
and blood, the passage of CO2 from the blood via the lung to room air. The passage in both directions of these gasses is mandatory for successful conduct of anesthesia and for well-being of the patient in general. A
frequent mechanism of respiratory compromise includes aspiration of gastric contents. In R.T.S. patients, aspiration occurs frequently in the awake or sleeping state. Recurrent aspiration is frequently associated
with pneumonia on an acute and chronic basis. With preexisting pulmonary damage as a consequence of this problem, the anesthetic process has enhanced risk. If this is coupled with aspiration at the time of
anesthesia the combination can be calamitous.
The safe conduct of anesthesia depends upon delivery of gases to the brain by the heart and blood vessels. Along with this dependence comes a depressant effect on cardiovasculature in all patients
with or without disease entities. All anesthetics - gaseous or parenteral - depress the heart and blood vessels. This is usually well tolerated in the otherwise healthy patient, although it is quite possible to see
exaggerated undesirable effects of anesthetics manifested in healthy patients. Patients with pre-existing cardiac or vascular anomalies can have greater than usual negative effects of anesthetics, and this in turn
combined with a non-linear and unpredictable response. This combination can lead to excitement and/or terror for the anesthetist. The presence of cardiac anomalies can affect the delivery of gases to the body as a
whole and to the brain in particular. There is a delay in the uptake of anesthetics, resulting in prolongation of induction. Such a delay may be misinterpreted as inadequate concentration of anesthetic being
administered with the result that more agent is used, leading to pronounced depressant effect. Particular care should be exercised during the period of induction or onset of anesthesia when the physiologic chances are
most rapid and profound. It is quite possible to over-shoot the desirable end-point during induction. In a majority of cases, increasing the concentration of anesthetic directly depresses the heart muscular function
(contraction). It also frequently diminished heart rate. At the same time, it causes general relaxation of blood vessels throughout the body. The net result of these combined actions is a significant decrease
in overall perfusion or delivery of blood to tissues, particularly those of vital organs such as brain, kidney and the heart itself.
Passing through the induction phase of the anesthetic one proceeds to maintenance for the duration of the procedure. This is analogous to the eye of the storm. The requirements of the
patient usually can be met with minor adjustments of drug concentration and attention paid to fluid infusion and blood volume maintenance.
With the completion of the procedure it is necessary to terminate the anesthetic process. It is tempting to believe that this requires merely turning off of drugs and departing. Certainly,
anesthetic agents are stopped. However, it should be recalled that the beginning or induction of anesthesia are associated with profound physiologic alterations as a direct result of the anesthetic agents.
Discontinuing these agents causes equally abrupt changes in physiology - usually in the opposite direction. Depression of heart function does not merely resolve and return to normal. It is frequently replaced by
exaggerated activity before settling into the normal range. In a similar fashion, peripheral blood vessels which have relaxed or dilated can constrict abnormally, causing exaggerated blood pressure changes with compromise
and maldistribution of blood flow. Once again the problem of poor perfusion or delivery of blood to tissues is encountered.
During emergence from anesthesia one must also attend changes in airway function which can contribute to enhanced risk. Airway reactivity during emergence is usually exaggerated and can be
associated with bronchospasm and laryngospasm. In patients with anatomic airway problems, superimposing constrictive physiology can be life threatening.
The previous description of the anesthetic process is particularly related to safety. The next issue is that of duration. It is appropriate to tailor the anesthetic process to the duration
of the procedure and attempt to minimize prolonged effects. Getting rid of anesthetics always takes longer than introducing them. In addition, it always takes longer than one would predict or imagine. This has
to do with the solubility of the agents and their disposition in body fat. In a telling study at Stanford University, Dr. Whitcher examined the concentration of anesthetics in blood of operating room personnel after their
last exposure to travel levels of the anesthetics. Levels were detectable up to 80 hours following last exposure. Patients who have received anesthesia can be expected to have much higher concentrations for a longer
period of time. Such data might suggest that in patients with compromised central nervous system function there should be extended periods of monitoring of vital signs in the post-anesthetic period. It must be
stressed that there are no accurate data or guidelines to follow in this manner. There is a single case report4 of prolonged emergence from anesthesia with a variety of agents on several occasions - highlighting the
difficulty in predicting end points in these patients.
The idea that general anesthesia has many potential problems might suggest the possibility of other methodology such as regional anesthesia, acupuncture or other modalities. While each of these
has a place in dealing with the need for anesthesia, it is difficult to consider them because of the lack of predictability. Use of these modalities requires active participation by the patient including description and
interpretation and in the best of circumstances is not nearly as predictable as general anesthesia. Finally, the question of acceptability should be addressed. In U.S.A., induction of anesthesia is most often with
gas via mask. Such methods are less often employed in other countries where intravenous induction is utilized in most instances. Techniques can and should be tailored to the skills of the anesthetist and the comfort of
the patient and family. To search for a vein in a small patient who really doesn’t like the idea is unpleasant, but to utilize a gas or mask induction in a patient with compromised airway or serious aspiration
problems may well not be the safest technique. As in so many areas, compromise may be the only reasonable option. Use of premedication should be judicious. Sedative medications can be effective at ameliorating
psychological distress, but the risk of respiratory depression and/or airway compromise may make their use ill advised.
Management of pain in these patients presents a complex situation. The interpretation of pain and its communication are difficult. The assessment of pain relief and drug effect are marginal,
and the reduced margin of safety of analgesia drugs is a challenge. Regional techniques such as epidural anesthesia with or without catheter insertion are not available to these patients. Narcotics, the mainstay of
acute pain management, exhibit the same potential for exaggerated and non-linear responses as do anesthetic agents. Such problems should not preclude an effort at pain management but necessitate diligent meticulous
monitoring efforts to avoid poor outcome.
This introduction to the anesthetic process to which a significant portion of patients with Rubinstein-Taybi syndrome will need be exposed is an attempt to rationalize some of the many factors involved
and some of the decisions necessary. It is by no means exhaustive but perhaps it has been helpful.
References:
- Hennekam RCM, et al. Rubinstein-Taybi syndrome in the Netherlands. AM J Med Genet Suppl 1990; 6;17-29.
- Stirt JA. Anesthetic problems in Rubinstein-Taybi syndrome. Anesth Anolg 1981; 60 (7): 534-36.
- American Society of Anesthesia. New classification of physical status. Anesthesiology 1963:24,111.
- Dunkley CJA and Dearlove OR. Delayed recovery from anaesthesia in Rubinstein-Taybi syndrome [letter]. Paediatr Anaesth 1996; 6:245-46.
|
