SPECIAL TOPIC OVERVIEW - A REVIEW OF LABORATORY-ANIMAL ANESTHESIA WITH CHLORAL HYDRATE AND CHLORALOSE

Chloral hydrate (CH) and alpha-chloralose (CS) are often used to anest hetize laboratory animals although, to our knowledge, there have been no controlled studies of their anesthetic or analgesic effects. Induct ion of and recovery from anesthesia can be stressful, and anesthesia a nd analgesic quality have been questioned. Intraperitoneal (i.p.) admi nistration of CH has resulted in adynamic ileus and peritonitis in rat s, gastric ulcers in rats, and peritonitis in swine. Light anesthesia is induced in rats. In dogs, CH induces sedation to deep anesthesia wh en given intravenously. Gastric irritation in dogs can occur when CH i s given orally. Chloral hydrate is considered a good sedative-hypnotic for farm animals. Intravenously administered CS anesthetizes dogs and cats for 5 to 10 hours, but the animals may require respiratory suppo rt. Chloralose appears to be a satisfactory anesthetic for dogs when s tage III thiobarbiturate anesthesia is first induced. It is difficult to gauge the depth of anesthesia and analgesia with CS. In our clinica l experience with swine and calves, CH given i.p. leads to adynamic il eus. We have found that CS given i.p. causes an inflammatory response in guinea pigs, rats, and calves. We observed that CS analgesia varies with the type of surgical procedure performed. Based on a literature review and our clinical experience, we suggest that CH or CS anesthesi a should be preceded by administration of barbiturates, opioids, alpha -2 agonists, or phenothiazine tranquilizers. Chloral hydrate should on ly be used as a sedative or hypnotic for dogs; CS should not be used a s a sole anesthetic agent. Neither drug should be used i.p. for surviv al surgery.