Ketamine was first introduced into general clinical practice in 1966.1 Its use for ocular examination under anesthesia has been generally accepted,2 but conflicting reports have appeared concerning its use in stabismus surgery.3'4 We wish to report on our use of Ketamine as the sole anesthetic agent in 44 consecutive strabismus operations in children.
MATERIALS AND METHODS
A total of 44 children, 24 males and 20 females, between the ages of six months and six years were operated on for strabismus using Ketamine as the sole anesthetic agent.
The surgical procedures performed are as shown in Table I. All children were hospitalized the day before surgery and examined by the pediatrician and anesthesiologist. The children were fasting for at least eight hours before surgery. Premedication with atropine 0.1 mg0.4 mg depending on age and weight was given to all and some of the children also received an injection of diazepam one hour before surgery.
Ketamine was given intramuscularly in a dose of 1 0-1 2 mg/kg in the operating room. We found that the second injection is usually required about 20 minutes after thefirst dose. If given later the patient begins to stir. The additional injection of Ketamine was given intramuscularly as 50 percent of the original dose, or intravenously in a dosage of 2 mg/kg over a period of 40-60 seconds. Surgery lasted between 20-90 minutes with an average of about 50 minutes and in no case was more than three injections necessary.
At the beginning of our study Ketamine was given in a dosage of 4-6 mg/kg, but because of inadequate anesthesia we gradually increased the dosage until anesthesia was satisfactory. The original cases who received the lower doses are not included in our study.
The surgeon and anesthetist were asked to observe the patient during surgery for breathing difficulties, nystagmus, unusual movements, or other complications. The recovery room nurse reported any retching, vomiting, or hallucinations. The surgeon and anesthetist then graded the anesthesia as good, fair, or poor. In the cases graded as fair there was nystagmus, increased muscle tonus of the extremities, or purposeless movements of the hands and head, which required additional injections of Ketamine in order to complete the surgery. Only in the "poor" cases was it impossible to complete the surgery even with additional Ketamine, and recourse had to be made to intubation and inhalation anesthesia.
The results as tabulated by the anesthesiologist and surgeon are shown in Table II.
In most cases good anesthesia was achieved within four to six minutes of intramuscular injection of Ketamine and was adequate for 2040 minutes. In 1 7 patients additional injections were needed. Seven of these were because of inadequate anesthesia, and in ten because of the length of the procedure. Only two patients were inadequately anesthetized after repeated injections and required general anesthesia.
KETAMINE ANESTHESIA IN STRABISMUS
EVALUATION OF KETAMINE ANESTHESIA
In all the children reflex blinking was retained, but did not interfere with the placement of the speculum. In two patients increased muscle tonus of the extremities was present. Three patients were observed to have purposeless movements of the extremities and head. An additional injection of Ketamine allowed continuance of the surgery without difficulty. Nystagmus was noted in six children, usually during the onset of anesthesia, and either ceased spontaneously or was easily controlled with a fixation suture. In no case was there any reaction to grasping to conjunctiva with forceps.
There were no breathing difficulties encountered. Excessive salivation was prevented by preoperative atropine. No local reaction to the Ketamine injection was observed. Since blood pressure and pulse were not monitored in all the cases they have not been included in this report.
Recovery was uneventful. Consciousness usually returned within 45-60 minutes, and no delirium or hallucinations were observed. A few instances of nausea or vomiting did occur in the recovery period. All patients were discharged the day after surgery.
Ketamine, a phencyclidine derivative, produces an unusual analgesic state in which the patient appears to be dissociated from his environment and does not respond to pain, yet maintains normal reflexes and muscle tonus.1 The patient breathes normally - the airway is patent and only rarely has apnoea been reported. After intramuscular injection, induction is prompt, repeated doses may be given, and wakefulness returns in a relatively short period of time.
The dosage recommended by Goodman and Gilman5 of 4-6 mg/kg intramuscularly was found to be inadequate and therefore 10-12 mg/kg as recommended by Apivor4 was used.
The use of Ketamine in extraocular muscle surgery has been controversial. Falls6 in a series of varied ocular procedures, reported the successful use of Ketamine in two strabismus operations. Mehta3 used Ketamine in 16 strabismus procedures but felt that there was an unacceptably high incidence of side effects. Apivor4 reported a series of 106 strabismus operations and recommended the use of Ketamine, but in conjunction with a mixture of 70 percent nitrous oxide and oxygen during induction.
We are satisfied with the effectiveness, safety, and ease of use of Ketamine as the sole anesthetic agent in extraocular muscle surgery. The mild nystagmus, increased muscle tonus, and purposeless movements previously reported are well controlled by the use of fixation sutures and the proper dosage of Ketamine, repeated when necessary. By using this anesthetic in young children only, we avoided the unpleasant occurrence of hallucinations and frightening dreams which is a known unpleasant side effect in older patients.7 Despite its relative safety, Ketamine should be administered only under the direction of trained anesthesia personnel because the occurrence of potentially severe side effects have been reported.8 Likewise, the drug should not be used in the presence of cardiac insufficiency, increased blood pressure, or increased intracranial pressure.
Though used in our series only in hospitalized patients, Ketamine has been shown to be appropriate for outpatient surgery.9 We feel that our experience warrants its use as an alternative to traditional intubation and inhalation anesthesia in strabismus surgery.
Because of the conflicting opinions in the ophthalmic literature concerning the efficacy of Ketamine anesthesia in strabismus surgery, we decided to report our experience in 44 children operated upon between the ages of six months and six years. Satisfactory anesthesia was achieved in all cases except two who required intubation and inhalation technique in order to complete the surgery. No serious side effects were observed during or after the surgery. Its ease of administration, freedom from side effects, and satisfactory anesthesia, make Ketamine our primary anesthetic choice for strabismus surgery in children.
Our thanks to Mrs. Bilha Savell for technical assistance.
1 . Corssen G, Domino EF: Dissociative anesthesia: further pharmacologic studies and first clinical experience with the phencyclidine derivative Cl581. Anesth Anaig Curr Res 45:29, 1966.
2. Brueggemann WG, Helveston EM: Ketamine anesthesia. Ophthalmic Surg 2:243, 1971.
3. Mehta S, Dugmore WN, Raichand M: Ketamine in pediatric ophthalmic practice. Anesth 27:460, 1972.
4. Apivor D: Ketamine in pediatric Ophthal mological surgery. Anesth 28:501, 1973.
5. Goodman LS, Gilman A: The Pharmacological Basis of Therapeutics, 5th ed. New York, MacMillan, 1975, ? 101.
6. Falls HF, Hoy JE, Corssen G: CI-581: an intravenous or intramuscular anesthetic. Am J Ophthalmol 61:1093, 1966.
7. Morgan M, Loh L, Singer L, et al: Ketamine as the sole anesthetic agent for minor surgical procedures. Anesth 26:158, 1971.
8. Hawks WN Jr, Levin KJ, Lowe E: Some side effects of Ketamine hydrochloride during ophthalmic examination. J Pediatr Ophthalmol 8:171, 1971.
9. Harris JE, Letson RD, Buckley JJ: The use of CI581, a new parenteral anesthetic in ophthalmic practice. Trans Am Ophthalmol Soc 66:206, 1968.
KETAMINE ANESTHESIA IN STRABISMUS
EVALUATION OF KETAMINE ANESTHESIA