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ANESTHESIA AND ANALGESIA . . . Current Researches VOL.54, No. 3, MAY-JUNE, 1975

Min imizing Emergence Phenomena: Subdissociat ive Dosage of Ketamine in Balanced Surgical Anesthesia HOWARD S. LIANG, M.D.* HOWARD G. LIANG, M.D. St. Louis, Missouri

Three hundred twelve patients, ranging in age from 14 to 89 years and undergoing various major and minor surgical procedures, were anesthetized by oxygen, nitrous oxide, and ketamine in sequence. Anesthesia was induced with thiopental (5.8 mg./kg.). The first 212 patients received a n initial dose of ketamine of 1.6 mg./kg. lean body mass; 100 other patients, a n initial (subdissociative) dose of ketamine of 0.4 mg./kg. body weight. Subsequent doses of ketamine, one-half t h e

I

continuing search for a technic of ketamine administration that minimizes postanesthetic emergence phenomena, we employed low-dose ketamine in combination with balanced anesthesia for various types of surgical procedures in post-pubertal patients. Following is a report of our experience. N THE

METHODS A N D MATERIALS Since ketamine has not been clearly defined as the agent of choice for certain clinical conditions, patients were selected because they exhibited one or more of the following criteria: a. Cardiopulmonary instability b. Multisystems diseases c. High-risk elderly with poor central/ peripheral response d. History of or anticipating multiple surgical procedures

initial dose, were given 20 to 40 minutes apart, a s needed. Postoperative subjective reactions were limited to slight confusion on emergence, with some disorientation t o time, and occurred in 10 patients ( 5 percent) in the first group and 4 (4 percent) in the latter group. No psychotomimetic reactions were noted in either group. The latter group unanimously found the anesthetic technic acceptable f o r future use.

e. Obesity f. Elevated serum hepatic enzymes g. Multiple drug allergies Three hundred twelve patients, ranging in age from 14 to 89 years and in weight from 38.6 to 170.5 kg. (mean _c S.D., 69.0 k 16.9 kg.) were studied. There were no restrictions as to sex or A.S.A. physical status. Premedication consisted of atropine, an opioid, and a tranquilizer intramuscularly (I.M.) 90 minutes before induction. Intravenous (I.V.) fluids, usually Hartmann’s solution, were started through a free-flowing cannula or needle. A Riva-Rocci sphygmomanometer was placed over the brachial artery for blood-pressure readings. In selected cases, electrocardiographic tracing, urine output, and rectal temperature were also monitored. Anesthesia was induced with 2 percent thiopental I.V. solution, 100 percent oxygen

*Attending Anesthesiologist, Department of Anesthesiology, St. John’s Mercy Medical Center, St. Louis, Missouri 63141. Paper received: 8/23/74 Accepted for publication: 12/23/74

Emergence Phenomena . . . Liang and Liang

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for denitrogenization, and then a 65 percent nitrous oxide-oxygen mixture. When endotracheal intubation was elected, a single I.V. dose (40 to 80 mg.) of succinylcholine plus 3 to 5 ml. of 2 percent lidocaine topical spray was used. Patients were allowed to resume spontaneous respiration thereafter. When muscular relaxation was required, a 0.2 percent succinylcholine solution in I.V. drip was provided, and either assisted or controlled ventilation was instituted. Ketamine was then administered I.V. in the predetermined dosage at a rate of 10 mg./15 sec., timed to be 1 to 2 minutes before the skin incision or other surgical intervention. The first 212 cases (series A, 75 men and 137 women) received an initial dose of ketamine of 1.6 mg./kg. lean body mass. Series B (100 cases, 32 men and 68 women) received a subdissociative or analgesic dose of ketamine of 0.4 mg./kg. body weight. Weight and age groupings were comparable in both series. Subsequent doses of ketamine, onehalf the initial dose, were given as needed at about 20 to 40 minutes apart. Except for a larger number of patients of the high-risk elderly class and with multisystems diseases in series A (20 percent) than in series B (11 percent), there were no significant differences between the two series in the percentage of patients with the previously stated criteria for use of ketamine. Nearly all types of major and minor orthopedic, gynecologic, vascular, and general surgical procedures were represented (table 1 ) . There were 11 emergency cases in series A and 7 in series B. Over 90 percent of the patients received atropine (0.3 to 1.0 mg.), meperidine (25 to 100 mg.) , or oxymorphone (0.5 to 1.5 mg.) and hydroxyzine (50 to 100 mg.) as preanesthetic medication. TABLE 1 Types of Surgical Procedures Series A

1. Body surface, soft tissues, and orthopedics 2. Intrathoracic

Series

B

Total

78

33

111

7

4

11

3. Upper abdominal

64

23

87

4. Lower abdominal

35

9

44

5. Perineal

22

26

48

6

5

11

212

100

312

6. Diagnostic Totals

At the end of the procedure, nitrous oxide was discontinued. Patients who had received a muscle relaxant were allowed to resume spontaneous respirations and were extubated as conditions permitted. In a few instances, when the muscle relaxant caused an extended period of subnormal ventilation, the endotracheal tube was left in place and the patient was transported to the recovery room for continuing respiratory care. Patients were given no special attention in the recovery room, no precautions being taken to maintain silence or to avoid disturbance during recovery. Vital signs and mental status were checked and recorded by the recovery-room nursing staff and any special event was noted on the chart. Patients were transported to the ward when fully oriented and in stable condition. A few patients in critical condition were sent to the surgical ICU for intensive care. Postoperative visits to all patients were made in the next 24 to 48 hours by one of the authors. Answers to a questionnaire were solicited from the patients in series B, as follows: 1. What was the last thing you remember happening before you went to sleep? 2. What was the first thing you remember happening when you woke up? 3. Do you remember a dream or other experience while you were asleep? 4. What was the worst thing about your operation? 5 . Would you like to have the same anesthetics again?

RESULTS Induction of anesthesia was smooth and gradual in all cases. Thiopental dosage was similar in both series (series A, mean 403 mg. or 5.9 mg./kg.; series B, mean 385 mg. or 5.5 mg./kg.). In series A, 124 patients (58 percent) and in series B, 44 percent were intubated. Muscle relaxant was required for 104 patients (49 percent) in series A and for 42 percent in series B. The mean total dosage of ketamine for series A patients was 135.6 mg. (range 50 to 500 mg.) and for series B, was 41.7 mg. (range 10 to 100 mg.) . By time-averaging, ketamine consumption was grossly 1mg./kg./hr. for series A and 0.4 mg./kg./hr. for series B. Because the mean duration of anesthesia was longer in series A (122 min.) than in series B (94 min.), the length of the procedure was compared with the number of

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ANESTHESIA AND ANALGESIA . . . Current Researches VOL.54, No. 3, MAY-JUNE, 1975

TABLE 2 Number of Injections of Ketamine in Relation to Duration of Procedure Series B

Series A

Potients

Surgical duration, min.

Patients

duration, Surgical min.

Initial dose only 1 additional 2 additional

45

64.1

27

47.0

83

109.8

37

90.8

53

119.5

24

108.8

3 or more additional

31

202.6

12

192.5

Total

212

doses of ketamine given (table 2) . At either dosage, there was no significant difference in the duration of anesthetic effect due to the drug for operations lasting 2 hours or less. After 2 hours, additional doses of ketamine seemed needed more frequently in series B than in series A. During the procedures, cardiovascular signs were stable in the majority of patients. With I.V. fluids infusing well, there was no significant change in blood pressure 5 to 10 minutes after thiopental administration, but a statistically significant (p