chapter 8 Rectal Sedation
Interest in the rectal route of drug administration has increased in anesthesiology and, to a lesser extent, in dentistry in recent years.1 Historically the rectal route of drug administration was used for the administration of smoke (“fumigation”) for resuscitation2 and the administration of anesthetics. An ether boiler for rectal application was developed in 1847 by Pirogoff.3 With the advent of more reliable routes of drug administration (e.g., intravenous [IV] and inhalation), use of the rectal route decreased.
Certain situations remain in which rectal drug administration may be valuable. These include the administration of a drug to a patient who is unwilling or unable to take drugs orally. In most instances, this is a child or an adult with a disability requiring sedation either to permit treatment to proceed4–6 or as a preliminary to the induction of general anesthesia.7–9 Another situation in which rectal drugs are warranted is the administration of antiemetics to patients with nausea and vomiting. Although parenteral administration is preferred (if the patient is present in the office where the drug may be injected), rectal administration can be used if the patient objects to injection or if the patient is at home. Another indication for rectal administration of drugs is analgesics for postoperative control of pain.10
ADVANTAGES
In the past, it was thought that rectally administered drugs were absorbed directly into the systemic circulation via the vena cava, bypassing the enterohepatic circulation and thereby eliminating the hepatic first-pass effect, which so influences the clinical activity of most drugs administered enterally.11 The superior rectal vein empties into the inferior mesenteric vein and then into the portal system. The middle and inferior rectal veins empty into the internal iliac vein and the inferior vena cava.12,13 However, it has been demonstrated that hepatic clearance is the main factor affecting bioavailability of rectally administered drugs.1 This may be because blood flow occurs through anastomoses that interconnect the superior, middle, and inferior rectal venous systems, thereby producing a hepatic first-pass effect with rectally administered drugs. Other potential factors, such as adsorption by feces, intraluminal degradation by microorganisms, metabolism within the mucosal cell, and lymphatic drainage, do not significantly affect the fate of rectally administered drugs.
Comparing the oral, nasal, and rectal administration of the water-soluble benzodiazepine midazolam, Tolksdorf7 found that children aged 1 to 6 years accepted the oral drug better than rectal or nasal but that the rectally administered midazolam had the most rapid onset of action and fewest side effects in the postoperative period. In several studies, peak levels of clinical action were noted rapidly after rectal administration. Roelofse et al4 noted good anxiolysis, sedation, and cooperation 30 minutes after rectal administration of midazolam, whereas Kraus et al14 noted peak plasma levels of midazolam at 7.5 minutes.
DISADVANTAGES
The primary use of rectal drug administration in both medicine and dentistry is management of uncooperative patients, whether children or adults. It is strongly advised that rectally administered central nervous system (CNS) depressants be administered in the medical or dental office by the dentist or a staff person. Signs and symptoms of sedation develop rapidly with many rectal drugs; clinical sedation is evident at 15 to 30 minutes.4,14 Because the possibility of oversedation exists, it would be beneficial for the patient to be in an environment where oversedation could be easily recognized and the patient managed (“rescued”). An automobile en route to the dentist’s office is not a desirable location.
Because of the lack of control over the clinical actions of the drug, rectal administration ought not to be used in an effort to achieve deep sedation unless the dentist is well versed in general anesthesia and in airway management of the unconscious patient. The recommended use of rectal sedation is for the induction of minimal to moderate sedation when other, more controllable methods of anxiety control (IV, inhalation) may be added if needed during treatment. Rectally administered drugs may provide a level of patient management adequate for many procedures, such as root planing and curettage5 and restoration or extraction of primary teeth,6 but it may prove inadequate for procedures such as radiographs, which require a patient to remain immobile during exposure.15
The administration of rectal drugs is often considered difficult for the administrator and uncomfortable for the patient. Of 80 children receiving rectal premedication, deWaal, Huisman, and Veerman16 reported that 66 (82.5%) accepted rectal instillation well, 12 (15%) moderately well, and 2 (2.5%) poorly.
DRUGS
Many drugs have been administered rectally. Ideally a rectally administered drug will be available as a suppository, although in several cases (e.g., midazolam), drug formulations designed for parenteral administration have been successfully employed. Historically the two major drug groups that have been employed rectally are the barbiturates and opioids. More recently, the rectal administration of the benzodiazepine midazolam has received considerable attention. Because the barbiturates are no longer recommended for clinical use in sedation, the discussion to follow will focus primarily on nonbarbiturates. Full discussion of the rectal administration of barbiturates may be found in prior editions of this textbook.17
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