ANESTHESIA AND ANALGESIA. . Current Researches VOL.54, No. 6, Nov.-DEc.,1975

701

Cardiovasci lar Effects of Isoflurane and Halothane During Controlled Ventilation in Older Patients HARRY W. LINDE, Ph.D.* SEI OK OH, M.D.t JOHN HOMI, M.B., B.S.$ C. JOSHI, M.B., B.S.§ Chicago, Illinois 11

Isoflurane o r halothane was administered at twyo different inspired concentrations t o 21 surgical patients whose average a g e was 62 years. Most were in physical status (ASA) I1 o r 111. Patients were premedicated with diazepam and atropine, anesthesia was induced with thiopental, and tracheal intubation was facilitated with succinylcholine. Respiration was controlled manually o r with a ventilator. Anesthesia was maintained with 60 percent NiO and halothane 1 percent, then 0.5 percent, or with NzO-isoflurane 1.2 percent, then 0.6 percent in 0,.

Variations in t h e cardiovascular responses among patients given t h e s a m e anesthetic were a s g r e a t as t h e variation in responses between anesthetics. Both produced similar decreases in arterial pressure, cardiac output, and stroke volume. Changes in pulse r a t e were minimal, a n d t o t a l p e r i p h e r a l r e s i s t a n c e changes quite variable, for both drugs.

E

METHODS Twenty-one consenting male patients, ranging in age from 49 to 82 years (average 62) were studied. Physical status was I, 11, or I11 (ASA) , with 4 patients in status I. Operative procedures included most areas of the body except the thorax and cranium. Premedication, administered 1 to 11/2 hours before anesthesia, consisted of 10 mg of diazepam and 0.4 to 0.6 mg of atropine sulfate. Initial cardiovascular measurements were made just before induction of anesthesia with 5 mg/kg of thiopental.

people often require anesthesia. Despite this, there have been few studies of the cardiovascular effects of general anesthesia in the geriatric population.1 We felt it of interest to study, during clinical anesthesia, the effect of a new inhalation anesthetic agent, isoflurane," * on the cardiovascular system of older, less fit patients, and to compare their responses with those of a similar group anesthetized with halothane. LDERLY

**Isoflurane was supplied by Ohio Medical Products Division of Airco, Incorporated.

Both halothane and isoflurane appear satisfactory for inhalation anesthesia in the elderly.

*Associate Professor. IInstructor. $Associate Professor. $Assistant Professor. IlDepartments of Anesthesia, Northwestern University Medical School and Veterans Administration Research Hospital, Chicago, Illinois 60611. Read at the 49th Congress of the International Anesthesia Research Society, March 16-20,1975, Hollywood, Florida. This study was supported in part by a grant from Ohio Medical Products, Division of Airco, Inc. Paper received: 1/3/75 Accepted for publication: 4/25/75

702

ANESTHESIA AND ANALGESIA . . . Current Researches VOL.54, NO.6, Nov.-CEC.,1975

Tracheal intubation was facilitated, if necessary, with 1 mg/kg of succinylcholine. Anesthesia was maintained with N 2 0 - 0 2 (3:2) and either halothane 1 percent, then 0.5 percent, or with N,O-0,-isoflurane 1.2 percent, then 0.6 percent. Halothane was used with 9 patients and isoflurane with 12, 2 patients in the isoflurane group receiving only the higher concentration. Ventilation was controlled either with a mechanical ventilator or manually. At least 30 minutes elapsed at the stated inspired concentration of halothane or isoflurane before cardiac output was measured. Halothane was vaporized from a calibrated Fluotec@vaporizer and isoflurane from a calibrated Forte@ vaporizer. Vaporizers were calibrated by gas chromatography. Blood pressure and the ECG, lead I or 11, were recorded on a Grass Model 7 polygraph. Arterial pressure was measured from an indwelling radial artery cannula and transduced by a Statham strain gauge. Cardiac output was measured using indicator dilution technic with indocyanine green dye. The dye dilution curves were measured on a Gilford Model 103 IR dye densitometer and recorded on a modified Texas Instruments recorder. A measured dose of approximately 4 mg of dye was injected through an indwelling catheter whose distal end lay within the great veins in the thorax. The catheter was inserted either through an antecubital vein or the external jugular vein. All dye dilution curves were run at least in duplicate. Blood gases (Paco,, Pao,) and pH were measured in blood samples withdrawn from the arterial cannula at approximately the time of the cardiac output determinations. Six patients anesthetized with isoflurane were paired, retrospectively, with 6 patients anesthetized with halothane, on the basis of age, physical status, operation, control cardiac output, and ward blood pressure. Observations made during anesthesia were not considered in the pairing. No patient was considered for pairing unless he had observations made in the control period and during both the deeper and lighter anesthesia periods.

RESULTS The mean and standard deviation of the cardiovascular and other variables observed in the awake patients and during anesthesia at two inspired concentrations of halothane or isoflurane are presented in table 1. In *Serial #001, courtesy of Fraser Sweatman.

table 2, data from paired patients are presented as the differences and SD for the measured variable between isoflurane and halothane patients. The changes observed during isoflurane anesthesia, using each patient as his own control, are shown in table 3. Similar data for halothane are shown in table 4. No significant change occurred, with either agent, when inspired anesthesia concentrations were decreased, with the exception of a small increase in stroke volume during isoflurane. Arrhythmias rarely appeared during anesthesia in patients who did not have preexisting arrhythmias. One patient each had periods of nodal rhythm during isoflurane and halothane anesthesia. One additional patient (isoflurane) had ventricular extrasystoles when the surgeons were working near the carotid sinus. Cardiovascular data obtained during periods of dysrhythmia were not included in the tables.

DISCUSSION The objective of this investigation was to determine whether there was a difference between the cardiovascular response to isoflurane and to halothane anesthesia in older, less fit patients. Observations during anesthesia and operation were compared in two ways. First, the average response of all halothane patients was compared with all isoflurane patients before and twice during anesthesia. Second, patients paired on the basis of their preanesthesia status and operative procedure were compared in the awake and in the first and second anesthesia periods. In every comparison, differences between halothane and isoflurane observations are well within one standard deviation of one another. Both halothane and isoflurane did depress the cardiovascular system, as evidenced by a significant decrease in arterial pressure, cardiac output and stroke volume. Graves and others, studied a similar group of patients under nearly similar conditions of isoflurane anesthesia and found less overt cardiovascular depression. Although stroke volume decreased in their patients, a significant increase in heart rate kept arterial pressure and cardiac output at near-normal values. Their inspired anesthetic concentrations were similar to ours although, due to altitude differences, a greater proportion of our anesthetic consisted of N,O. We used

cardiovascular Effects. . . Linde, et a1

703

TABLE 1 Cardiovascular Measurements M e a n t SD Anesthetized Agent

Awake

1 yo halothone 1.2% iroflurane

0.5% halothane 0.6% iroflurane

H*

It

129 2 30 111 2 1 3

107 -C 21 96 2 23

107 -C 17 107 i 15

H e a r t rate, b e a t s h i n

H I

73 & 9 77 2 13

80 & 11 79 12

*

74 & 9 75 -t 15

Cardiac output, L/min

H

I

4.2 I+ 1.5 4.1 2 0.5

3.0 2 0.7 3.0 & 0.6

3.0 -C 1.0 3.0 t 0.5

Stroke volume, ml

H I

57 2 12 55 I+ 9

38 t 8 38 -C 5

41 2 9 41 & 3

TPR, t o r r x min/L

H

33 i 6 27 3z 6

37 k 15 33 rt 9

36 .+- 4 33 I+ 9

Paco,, t o r r

I H I

39 c 4 36 -C 4

38 zk 8 35 & 10

37 c 9 37 -C 10 100 2 23 118 2 30

Mean arterial pressure, t o r r

Elapsed time from induction of anesthesia, rnin Patient age, yr Number of observations

H I

-

59 5 17 59 & 17

H I H I

61 i 9 63 .+- 10

-

-

9 12

9 12

9 10

*H = Halathane f I = Isoflurane

TABLE 2 Average Differences: Paired Patients (Six Pairs) (Isoflurane-Halothane), M e a n Awake control

Mean arteriaI pressure, t o r r

-9225

Heart rate, beats/min

$9 -C 18

Cardiac output, L/min

$0.1 k 0.4

Stroke volume, ml

-4 2 9

TPR, t o r r x min/L

-4

Pace?, t o r r

-6 t 7

Elapsed time from induction of anesthesia, min Patient age, yr

diazepam as a premedicant and larger doses of thiopental and did not use nondepolar-

izing muscle relaxants. They used InnovaP as a premedicant in most patients and pancuronium in all. These drugs may produce increases in heart rate. Others3-5 have also reported increases in heart rate during isoflurane anesthesia. In the studies of Stevens and associates4 on volunteers during con-

c9 -

+- SD

1.2% iroflurane

0.6% iroflurane

versus 1 Yo hnlothane

versus 0 . 5 % halothone

-21 -C35

-7 i- 30

15

0 k 17

0.0 2 0.9

0.0 5 1.5

-2

C

O k 8

-2 2 14

-8 f 23

-6 2 16

-7 -C 15

-3 t- 5

$6 t 38

$8 t 34

$326

stant alveolar anesthetic concentrations and in the absence of other drugs, these increases in heart rate maintained a normal cardiac output in spite of a decreased stroke volume. The two agents, a t the concentrations chosen, appeared clinically to be equipotent. Originally, we had intended to ran-

ANESTHESIA AND ANALGESIA . . . Current Researches VOL.54, No. 6, Nov.-DEc., 1975

704

TABLE 3 Change From Preanesthetic Control M e a n Values

lsofl u rane

Inspired concentration 1.2% Mean arterial pressure, torr -15.1" Heart rate, beats/min +2.0 Cardiac output, L/min -1.104 Stroke volume, ml -16.44 TPR, torr x min/L +3.2

0.6% -9.2 -2.6

-1.lO-i -13.0* +5.8$

(Student's t , paired values). 'ip

Cardiovascular effects of isoflurane and halothane during controlled ventilation in older patients.

Isoflurane or halothane was administered at two different inspired concentrations to 21 surgical patients whose average age was 62 years. Most were in...
411KB Sizes 0 Downloads 0 Views