ORIGINAL ARTICLES
Does Preoperative Anxiety Influence Gastric Fluid Volume and Acidity? Per E. Haavik,
MD,
Eldar Smeide, MD, Bjmn Hofstad, MD, and Petter A. Steen, MD,
PhD
Departments of Anesthesiology, UllevAl Hospital and Rogaland Central Hospital, Stavanger, Norway
Preoperativeanxiety may increasegastric fluid acidity and volume. To pursue this possibility we evaluated the relationship between peroral premedication, preoperative anxiety, and gastric content in 246 consecutive patients presenting for elective gynecologic surgery. All patients fasted overnight and received either flunitrazepam 1 mg, oxazepam 25 mg, or placebo with 20 mL of water on the morning of surgery in a randomized, double-blind fashion. The patients assessed relief of anxiety usinga four-graded scale (excellent, good, fair, poor). Both flunitrazepam
T
he main goal of premedication is to relieve anxiety (1).A variety of benzodiazepines, including diazepam, oxazepam, and flunitrazepam, reduce anxiety preoperatively (14). Ideally, premedication should also minimize the risk of aspiration pneumonitis. Gastric fluid volumes > 25 mL with a pH < 2.5 have been widely used as critical indicators for the development of aspiration pneumonitis and thus should be avoided (5-8). Preoperative anxiety has been thought to delay gastric emptying and increase gastric addity and is therefore considered a risk factor in connection with aspiration pneumonitis (9-11). If preoperative anxiety does have a negative impact on gastric fluid volume and pH, we hypothesized that the anxiolytic effects seen with various benzodiazepineswould counteract this negative influence. The purpose of this placebo-controlled study was to evaluate the relationship between peroral benzodiazepine premedication with flunitrazepam and oxazepam, preoperative anxiety, and gastric content in patients scheduled for elective gynecologic surgery. This study was supported by a grant from Kabi Pharmacia, Norway. Accepted for publication February 20,1992. Address correspondence to Dr.h i d e , Department of Anesthesiology, Rogaland Central Hospital, Armauer Hansensvei 20, 4011 Stavanger,Norway.
and oxazepam decreasedanxiety (P < 0.01) compared with placebo. However, no mmlations between type of premedication or level of anxiety and gastric contents were found. The proportion of patients with gastric fluid volume > 25 mL and pH < 2.5 was not sigruficantly difhnt in any of the p u p s studied. These results suggest that neither p r a l benzodiazepine premedication nor preoperative anxiety have a clinically important impact on gastric content in patients presenting for elective gynecologic surgery. (Anesth Analg 1992;75914)
Methods The study protocol was approved by the hospital ethical committee and performed in accordance with the latest edition of the Declaration of Helsinki. Only patients scheduled for surgery in general anesthesia with endotracheal intubation were selected. During a 6-mo period, written informed consent was obtained from 246 consecutive patients, aged 18-70 yr, ASA physical status I and 11, all scheduled for gynecologic surgery. Patients with conditions known to affect gastric secretion and emptying, such as pain, secondor third-trimester pregnancy, a history of serious gastrointestinaldisease, or obesity (defined as a body weight exceeding 120%of ideal body weight [IBWin kg = Height in cm - 1001) were excluded. Patients who had used psychotropic drugs during the last 10 days or suffered from alcohol or drug addiction were excluded as well. Patients were randomized to receive either oxazepam 25 mg, flunitrazepam 1 mg, or placebo in a double-blind fashion. As no exact data were available to secure equipotent anxiolytic doses, the dosages recommended by the manufactures (oxazepam, Kabi Vitrum; flunitrazepam, Roche) were used. The study medications were placed in identical-looking soft gelatine capsules (capsugel). All patients fasted after midnight. Inpatients were hospitalized the day before surgery and received a single dose of the study drug
01992 by the International Anesthesia Research Society
ooo3-2999192155.00
Anesth Analg 1992;75:91-4
91
92
ANESTH ANALG
HAAVM ET AL. PREOPERATIVE ANXIETY AND GASTRIC VOLUME-ACIDITY
between 9 and 11 PM the evening before surgery and the same compound the following morning at 7 AM. Outpatients received only the morning dose of the study drug. The prernedication drugs were given with 20 mL of water at 7 AM. A minimum time lapse of 45 min from premedication to induction of anesthesia was required; no maximum length was set. On arrival in the operating room, the patients gave a subjective assessment of the anxiolytic effect by answering the following question: "How do you evaluate the effect of the tablet on your anxiety now just before the operation; excellent, good, fair, or poor relief of anxiety?" Immediately after induction of anesthesia and orotracheal intubation, a multiorificed polyvinyl orogastric tube size 22F was inserted to 60 crn from the incisors, and correct position was verified by air insufflation and auscultation. The tube was withdrawn under intermittent suction, and all aspirated fluid was collected in a mucus trap polyvinyl bottle, which collapsed at negative pressures exceeding -60 mm Hg. The procedure was repeated once, and total volume, pH, and color of aspirate were recorded. Gastric pH was measured using Merck pH paper (12).The pH of the first 50 samples were double-checked with a calibrated Radiometer pH meter 28 to ensure that no systematic error was added to the study during the measurement of pH. Results are given as means with standard deviation (sD), and range where appropriate. Statistical analysis was performed using one-way analysis of variance for parametric values and the ?-analysis to compare proportions of patients in the different groups. Differences were considered statistically significant when P < 0.05.
Results Of the 246 patients studied, 152 were hospitalized for laparotomy (inpatients) and 94 patients were scheduled for ambulatory laparoscopy (outpatients). No differences in age distribution were noted in the three groups studied, with mean ages of 41 f 14/40f 14, and 41 k 13 yr, respectively. The mean time from premedication to induction of anesthesia was 172 f 101 (range 45-380 min) for flunitrazepam, 140 f 88 (range 45-392 min) for oxazepam, and 171 +- 102 (range 45-380 min) for placebo (P > 0.05). In Table 1 the patients' own ratings of anxiolytic effects are presented. Both flunitrazepam and oxazepam had a sigruficantly better anxiolytic effect than placebo (P < 0.01). However, this difference in anxiolytic effect was not associated with any differences in gastric fluid volume and pH (Table 2). The gastric fluid volumes and pH found in inpatients did not significantly differ from those found in
1992;75914
Table 1. Patients' Assessment of Anxiolytic Effect Effect
Flunitrazepam
Oxazepam
Placebo
Sum
Excellent Good Fair Poor
15 41 19 7
16 33 26 6
6 25 29 17
37 99 74 30
Sum
82
81
77
240
Flunitrazepam = oxazepam > placebo (P < 0.01). Data lacking in six patients.
outpatients (Table 2). Furthermore, no significant difference was found in pH between bile-stained, green aspirate and aspirate described as clear, bright yellow. The proportion of patients with gastric fluid volumes > 25 mL and pH e 2.5 were not different for flunitrazepam, oxazepam, or placebo, whether the whole group was studied or inpatients or outpatients were studied separately (Table 3).To look at the effect of anxiety, independently of the drug given, the proportion of patients with gastric fluid volume > 25 mL and pH < 2.5 was compared between patients reporting poor or fair relief of anxiety and those reporting excellent or good relief (Table 3).No si&icant difference could be detected using these criteria either.
Discussion This is the first placebo-controlled study of the relationship between prernedication with peroral benzodiazepines, preoperative anxiety, and gastric content. Peroral prernedication with benzodiazepines may influence gastric content in different ways. Some studies have shown an increase in gastric emptying and pH after intake of diazepam (13-16).These changes are probably due to effects on regulatory functions in the central nervous system (15)and could be present with other benzodiazepines as well. Further, the volume of fluid ingested with the premedication seems to play a role in determining the total gastric volume (5-8). In previous studies, 5CL150 mL of water has been ingested. We allowed only 20 mL of water ("a sip of water") to be taken, thereby minimizing, if not eliminating, the effect of any water intake on the results. When studying anxiolytic effects of drugs given preoperatively, the placebo effect should be separated from the phannacologic effect (1). Madej and Paasku (1) believe the most reliable way to test for anxiolytic effects is to let the patient in some form assess the level of anxiety, as we did in the present study. Preoperative anxiety has been asserted as a risk
ANESTH ANALG
HAAVIK ET AL.
1992;75914
PREOPERATIVE ANXIETY AND GASTFJC VOLUME-ACIDITY
93
Table 2. Volume and pH of Aspirated Liquids Flunitazepam
Oxazepam
Placebo
All
2.0 2 1.1 23 f 21
2.2 f 1.1 18 r?: 18
2.4 ? 1.3 18 r?: 18
2.2 ? 1.2 20 2 18
2.1 f 1.1
2.1 f 1.2 19 f 17
2.3 2 1.3 23 2 13
2.2 5 1.2 19 ? 16
2.1 f 1.1 15 f 13
2.4 f 1.4 22f23
2.2 ? 1.2 21 ? 20
All patients (n = 246) PH Vol (mL) Inpatients (n = 152) PH Vol (mL) Outpatients (n = 94) PH Vol (mL)
22 f 19 2.0 f 0.9
25 f 24
Vol, volume. There were no statistically significant differencesbetween any of the listed groups (P > 0.1).
Table 3. Proportion of Patients With Gastric Volume > 25 mL and pH < 2.5 Prernedication Flu (n All patients (n = 246) Inpatients (n = 152) Outpatients (n = 94)
Relief of anxiety
Ow (n = 88)
Pla (n = 73)
All (n = 246)
Exdent-gd
Fair-poor
26/85(31%)
21/88 (24%)
18/73(25%)
65/246(26%)
401141 (28%)
241103 (23%)
16/52(31%)
13/55(24%)
9/45(20%)
381152 (25%)
22/92(24%)
15/59(25%)
lorn (30%)
8/33(24%)
9/28(32%)
27/94(m)
18/49(37%)
9/44(21%)
=
85)
Flu, BuNhzepam; Oxa, oxazepam; Pla, placebo. There were no statistidy sigruficant difkrences (P > 0.1) between any of the listed groups.
factor in connection with gastric content and aspiration pneumonitis (9,17). As previously reported (4), we found that flunitrazepam had a better overall anxiolytic effect than oxazepam and placebo. However, with the dosages used we could not detect any differences in gastric fluid volume and acidity between patients receiving flunitrazepam, oxazepam, or placebo. Neither could we find any differences in gastric contents between patients reporting good versus those reporling poor relief of anxiety, irrespectively of which drug they had received. Hence, our results do not support the existence of any association between the level of preoperative anxiety and gastric fluid volume and pH. One could speculate that the doses given where too small to achieve adequate anxiolysis and thereby sipficant effects on gastric fluid volume and pH. However, previous studies have not shown significant differences in anxiolytic effect between flunitrazepam 2 mg and 1 mg (3), or between flunitrazepam 1 mg and oxazepam 30 mg (2). Further, the values for gastric fluid volume and pH found with oxazepam 25 mg corresponded very well to the results in an earlier study where twice as much oxazepam (50 mg) was given (18).
Perhaps we need to better differentiate various types of anxiety in order to define patients in whom preoperative anxiety may influence gastric content. Simpson and Stakes (11) found that "gastric stasis occurred only in patients with a low predisposition to anxiety who became apprehensive whilst awaiting surgery." Our study did not make such distinctions possible. On the other hand, the rate of gastric emptying is just one of the many factors determining the volume of gastric fluid present at induction of anesthesia. Interestingly, we did not observe any differences in gastric fluid volume and pH between inpatients, all scheduled for laparotomy, and outpatients, all scheduled for laparoscopy. Our findings contrast with the long-held assumption that outpatients as a group have increased gastric volumes (9,17). Similar to Brock-Utne et al. (19), we did not find bile-stained aspirate to be more alkaline than clear aspirate. The accuracy of blind aspiration for studies of gastric content has been questioned by several authors (20,21) and has been a source of discussion in numerous studies (5-8,13). We used a larger multiorificed gastric tube (22F) than was used in many previous studies (5-8).Further, the suction system
94
HAAVIKETAL.
PREOPERATIVE ANXIETY AND GASTRIC VOLUME-ACIDITY
was modified to prevent excessive negative pressure and sticking of the tube to the gastric wall. We believe these measures, together with the fact that one investigator performed the majority of aspirations, minimized the systemic error of blind aspiration in our study. We used Merck pH paper for the pH measurements, which has a high degree of accuracy compared with electronic pH meters (12,19), something that is in accordance with our own experience. In summary, the results of this placebo-controlled study suggest that neither premedication with flunitrazepam and oxazepam in the present dosages nor the level of preoperative anxiety have any notable effects on gastric fluid volume and acidity. The mean gastric pH was C2.5 in all groups studied. Large proportions of patients in all groups had a combination of gastric fluid volume and acidity disposing for aspiration pneumonitis should regurgitation occur. Other measures than relieving preoperative anxiety must therefore be considered if the risk of aspiration pneumonitis is to be minimized.
References 1. Madej TM, Paasku RT. Anesthetic premedication: aims, assessment and methods. Can J Anaesth 1987;34:259-73. 2. Pakkanen A, Kangas L, Kanto J. A comparative study on the clinical effects of flunitrazepam and oxazepam as oral premedication. Int J Clin Pharmacol Ther Toxicol1981;19:275-8. 3. Male CG, Lim YT, Male M, et al. A comparison of three benzodiazepines for oral premedication in minor gynaecological surgery. Br J Anaesth 1980;52:429-35. 4. Hofstad B, Haavik PE, Wickstrem E, Steen PA. Benzodiazepines as oral premedication. A comparison between oxazepam, flunitrazepam and placebo. Acta Anesthesiol Scand 1987;31:2959. 5. Maltby JR, Sutherland AD, Sale JP, et al. Preoperative oral fluids: is a five-hour fast justified prior to elective surgery? Anesth Analg 1986;65:1112-6.
ANESTH ANALG 1992;75914
6. Manchikanti L, Canella MC, Hohlbein L, et al. Assessment of effect of various modes of premedication on add aspiration risk factors in outpatient surgery. Anesth Analg 1987;66814. 7. Brocks K, Jensen S, Schmidt JF, et al. Gastric content and pH after oral premedication. Acta Anesthesiol S a n d 1987;31: 448-9. 8. Hardy JF. Large volume gastro-esophagalreflux: a rationale for risk reduction in the preoperative period. Can J Anaesth 1988;35162-73. 9. Lichtor JL. Psychological preparation and preoperative medication. In: Miller RD, ed. Anesthesia. New York Churchill Livingstone, 1990:913. 10. Guyton AC. Textbook of medical physiology. 7th ed. Philadelphia: Saunders, 1986:774-8. 11. Simpson KH, Stakes AF. Effect of anxiety on gastric emptying in preoperative patients. Br J Anaesth 1987;595404. 12. Chaffe A. Which pH paper? Br J Anaesth 1987;59118%91. 13. Hjortse E, Mondorf T. Does oral premedication increase the risk of gastric aspiration? Acta Anaesthesiol Scand 1982;26 505-6. 14. Bimbaum D, Karmelli F, Tefera M. The effect of diazepam on human gastric secretion. Gut 1971;12:61M. 15. Schurizek BA, Kraglund K, Andreasen, et al. Gastrointestinal motility and gastric pH and emptying following ingestion of diazepam. Br J Anaesth 1988;61:712-9. 16. Lehot JJ, Delat-Besson R, Bastien 0, et al. Should we inhibit gastric acid secretion before cardiac surgery? Anesth Analg 1990;70185-90. 17. Ong BY, Palahniuk RJ, Cumming M. Gastric volume and pH in out-patients. Can Anaesth SOCJ 1978;253&9. 18. Ssreide E, Reiestad F, Stremskag KE, et al. Oral oxazepam vs. intramuscular morphine-hyoscine for premedication: a study of gastric content using fibre-optic gastroscopy. Eur J Anaesthesiol 1990;7375-80. 19. Brock-Utne JG, Rout C, Moofley J, et al. Influence of preoperative gastric aspiration on the volume and pH of gastric contents in obstetric patients undergoing caesarean section. Br J Anaesth 1989;62:397-401. 20. Adelhej B, Petring OU, Hagelsten JO. Inaccuracy of peranesthetic gastric intubation for emptying liquid stomach contents. Acta Anaesthesiol Scand 1986;30:41-3. 21. Taylor WJ, Champion MC, Barry AW, et al. Measuring gastric contents during general anaesthesia: evaluation of gastric blind aspiration. Can J Anaesth 1989;3651-4.
Does Preoperative Anxiety Influence Gastric Fluid Volume and Acidity? Per E. Haavik,
MD,
Eldar Smeide, MD, Bjmn Hofstad, MD, and Petter A. Steen, MD,
PhD
Departments of Anesthesiology, UllevAl Hospital and Rogaland Central Hospital, Stavanger, Norway
Preoperativeanxiety may increasegastric fluid acidity and volume. To pursue this possibility we evaluated the relationship between peroral premedication, preoperative anxiety, and gastric content in 246 consecutive patients presenting for elective gynecologic surgery. All patients fasted overnight and received either flunitrazepam 1 mg, oxazepam 25 mg, or placebo with 20 mL of water on the morning of surgery in a randomized, double-blind fashion. The patients assessed relief of anxiety usinga four-graded scale (excellent, good, fair, poor). Both flunitrazepam
T
he main goal of premedication is to relieve anxiety (1).A variety of benzodiazepines, including diazepam, oxazepam, and flunitrazepam, reduce anxiety preoperatively (14). Ideally, premedication should also minimize the risk of aspiration pneumonitis. Gastric fluid volumes > 25 mL with a pH < 2.5 have been widely used as critical indicators for the development of aspiration pneumonitis and thus should be avoided (5-8). Preoperative anxiety has been thought to delay gastric emptying and increase gastric addity and is therefore considered a risk factor in connection with aspiration pneumonitis (9-11). If preoperative anxiety does have a negative impact on gastric fluid volume and pH, we hypothesized that the anxiolytic effects seen with various benzodiazepineswould counteract this negative influence. The purpose of this placebo-controlled study was to evaluate the relationship between peroral benzodiazepine premedication with flunitrazepam and oxazepam, preoperative anxiety, and gastric content in patients scheduled for elective gynecologic surgery. This study was supported by a grant from Kabi Pharmacia, Norway. Accepted for publication February 20,1992. Address correspondence to Dr.h i d e , Department of Anesthesiology, Rogaland Central Hospital, Armauer Hansensvei 20, 4011 Stavanger,Norway.
and oxazepam decreasedanxiety (P < 0.01) compared with placebo. However, no mmlations between type of premedication or level of anxiety and gastric contents were found. The proportion of patients with gastric fluid volume > 25 mL and pH < 2.5 was not sigruficantly difhnt in any of the p u p s studied. These results suggest that neither p r a l benzodiazepine premedication nor preoperative anxiety have a clinically important impact on gastric content in patients presenting for elective gynecologic surgery. (Anesth Analg 1992;75914)
Methods The study protocol was approved by the hospital ethical committee and performed in accordance with the latest edition of the Declaration of Helsinki. Only patients scheduled for surgery in general anesthesia with endotracheal intubation were selected. During a 6-mo period, written informed consent was obtained from 246 consecutive patients, aged 18-70 yr, ASA physical status I and 11, all scheduled for gynecologic surgery. Patients with conditions known to affect gastric secretion and emptying, such as pain, secondor third-trimester pregnancy, a history of serious gastrointestinaldisease, or obesity (defined as a body weight exceeding 120%of ideal body weight [IBWin kg = Height in cm - 1001) were excluded. Patients who had used psychotropic drugs during the last 10 days or suffered from alcohol or drug addiction were excluded as well. Patients were randomized to receive either oxazepam 25 mg, flunitrazepam 1 mg, or placebo in a double-blind fashion. As no exact data were available to secure equipotent anxiolytic doses, the dosages recommended by the manufactures (oxazepam, Kabi Vitrum; flunitrazepam, Roche) were used. The study medications were placed in identical-looking soft gelatine capsules (capsugel). All patients fasted after midnight. Inpatients were hospitalized the day before surgery and received a single dose of the study drug
01992 by the International Anesthesia Research Society
ooo3-2999192155.00
Anesth Analg 1992;75:91-4
91
92
ANESTH ANALG
HAAVM ET AL. PREOPERATIVE ANXIETY AND GASTRIC VOLUME-ACIDITY
between 9 and 11 PM the evening before surgery and the same compound the following morning at 7 AM. Outpatients received only the morning dose of the study drug. The prernedication drugs were given with 20 mL of water at 7 AM. A minimum time lapse of 45 min from premedication to induction of anesthesia was required; no maximum length was set. On arrival in the operating room, the patients gave a subjective assessment of the anxiolytic effect by answering the following question: "How do you evaluate the effect of the tablet on your anxiety now just before the operation; excellent, good, fair, or poor relief of anxiety?" Immediately after induction of anesthesia and orotracheal intubation, a multiorificed polyvinyl orogastric tube size 22F was inserted to 60 crn from the incisors, and correct position was verified by air insufflation and auscultation. The tube was withdrawn under intermittent suction, and all aspirated fluid was collected in a mucus trap polyvinyl bottle, which collapsed at negative pressures exceeding -60 mm Hg. The procedure was repeated once, and total volume, pH, and color of aspirate were recorded. Gastric pH was measured using Merck pH paper (12).The pH of the first 50 samples were double-checked with a calibrated Radiometer pH meter 28 to ensure that no systematic error was added to the study during the measurement of pH. Results are given as means with standard deviation (sD), and range where appropriate. Statistical analysis was performed using one-way analysis of variance for parametric values and the ?-analysis to compare proportions of patients in the different groups. Differences were considered statistically significant when P < 0.05.
Results Of the 246 patients studied, 152 were hospitalized for laparotomy (inpatients) and 94 patients were scheduled for ambulatory laparoscopy (outpatients). No differences in age distribution were noted in the three groups studied, with mean ages of 41 f 14/40f 14, and 41 k 13 yr, respectively. The mean time from premedication to induction of anesthesia was 172 f 101 (range 45-380 min) for flunitrazepam, 140 f 88 (range 45-392 min) for oxazepam, and 171 +- 102 (range 45-380 min) for placebo (P > 0.05). In Table 1 the patients' own ratings of anxiolytic effects are presented. Both flunitrazepam and oxazepam had a sigruficantly better anxiolytic effect than placebo (P < 0.01). However, this difference in anxiolytic effect was not associated with any differences in gastric fluid volume and pH (Table 2). The gastric fluid volumes and pH found in inpatients did not significantly differ from those found in
1992;75914
Table 1. Patients' Assessment of Anxiolytic Effect Effect
Flunitrazepam
Oxazepam
Placebo
Sum
Excellent Good Fair Poor
15 41 19 7
16 33 26 6
6 25 29 17
37 99 74 30
Sum
82
81
77
240
Flunitrazepam = oxazepam > placebo (P < 0.01). Data lacking in six patients.
outpatients (Table 2). Furthermore, no significant difference was found in pH between bile-stained, green aspirate and aspirate described as clear, bright yellow. The proportion of patients with gastric fluid volumes > 25 mL and pH e 2.5 were not different for flunitrazepam, oxazepam, or placebo, whether the whole group was studied or inpatients or outpatients were studied separately (Table 3).To look at the effect of anxiety, independently of the drug given, the proportion of patients with gastric fluid volume > 25 mL and pH < 2.5 was compared between patients reporting poor or fair relief of anxiety and those reporting excellent or good relief (Table 3).No si&icant difference could be detected using these criteria either.
Discussion This is the first placebo-controlled study of the relationship between prernedication with peroral benzodiazepines, preoperative anxiety, and gastric content. Peroral prernedication with benzodiazepines may influence gastric content in different ways. Some studies have shown an increase in gastric emptying and pH after intake of diazepam (13-16).These changes are probably due to effects on regulatory functions in the central nervous system (15)and could be present with other benzodiazepines as well. Further, the volume of fluid ingested with the premedication seems to play a role in determining the total gastric volume (5-8). In previous studies, 5CL150 mL of water has been ingested. We allowed only 20 mL of water ("a sip of water") to be taken, thereby minimizing, if not eliminating, the effect of any water intake on the results. When studying anxiolytic effects of drugs given preoperatively, the placebo effect should be separated from the phannacologic effect (1). Madej and Paasku (1) believe the most reliable way to test for anxiolytic effects is to let the patient in some form assess the level of anxiety, as we did in the present study. Preoperative anxiety has been asserted as a risk
ANESTH ANALG
HAAVIK ET AL.
1992;75914
PREOPERATIVE ANXIETY AND GASTFJC VOLUME-ACIDITY
93
Table 2. Volume and pH of Aspirated Liquids Flunitazepam
Oxazepam
Placebo
All
2.0 2 1.1 23 f 21
2.2 f 1.1 18 r?: 18
2.4 ? 1.3 18 r?: 18
2.2 ? 1.2 20 2 18
2.1 f 1.1
2.1 f 1.2 19 f 17
2.3 2 1.3 23 2 13
2.2 5 1.2 19 ? 16
2.1 f 1.1 15 f 13
2.4 f 1.4 22f23
2.2 ? 1.2 21 ? 20
All patients (n = 246) PH Vol (mL) Inpatients (n = 152) PH Vol (mL) Outpatients (n = 94) PH Vol (mL)
22 f 19 2.0 f 0.9
25 f 24
Vol, volume. There were no statistically significant differencesbetween any of the listed groups (P > 0.1).
Table 3. Proportion of Patients With Gastric Volume > 25 mL and pH < 2.5 Prernedication Flu (n All patients (n = 246) Inpatients (n = 152) Outpatients (n = 94)
Relief of anxiety
Ow (n = 88)
Pla (n = 73)
All (n = 246)
Exdent-gd
Fair-poor
26/85(31%)
21/88 (24%)
18/73(25%)
65/246(26%)
401141 (28%)
241103 (23%)
16/52(31%)
13/55(24%)
9/45(20%)
381152 (25%)
22/92(24%)
15/59(25%)
lorn (30%)
8/33(24%)
9/28(32%)
27/94(m)
18/49(37%)
9/44(21%)
=
85)
Flu, BuNhzepam; Oxa, oxazepam; Pla, placebo. There were no statistidy sigruficant difkrences (P > 0.1) between any of the listed groups.
factor in connection with gastric content and aspiration pneumonitis (9,17). As previously reported (4), we found that flunitrazepam had a better overall anxiolytic effect than oxazepam and placebo. However, with the dosages used we could not detect any differences in gastric fluid volume and acidity between patients receiving flunitrazepam, oxazepam, or placebo. Neither could we find any differences in gastric contents between patients reporting good versus those reporling poor relief of anxiety, irrespectively of which drug they had received. Hence, our results do not support the existence of any association between the level of preoperative anxiety and gastric fluid volume and pH. One could speculate that the doses given where too small to achieve adequate anxiolysis and thereby sipficant effects on gastric fluid volume and pH. However, previous studies have not shown significant differences in anxiolytic effect between flunitrazepam 2 mg and 1 mg (3), or between flunitrazepam 1 mg and oxazepam 30 mg (2). Further, the values for gastric fluid volume and pH found with oxazepam 25 mg corresponded very well to the results in an earlier study where twice as much oxazepam (50 mg) was given (18).
Perhaps we need to better differentiate various types of anxiety in order to define patients in whom preoperative anxiety may influence gastric content. Simpson and Stakes (11) found that "gastric stasis occurred only in patients with a low predisposition to anxiety who became apprehensive whilst awaiting surgery." Our study did not make such distinctions possible. On the other hand, the rate of gastric emptying is just one of the many factors determining the volume of gastric fluid present at induction of anesthesia. Interestingly, we did not observe any differences in gastric fluid volume and pH between inpatients, all scheduled for laparotomy, and outpatients, all scheduled for laparoscopy. Our findings contrast with the long-held assumption that outpatients as a group have increased gastric volumes (9,17). Similar to Brock-Utne et al. (19), we did not find bile-stained aspirate to be more alkaline than clear aspirate. The accuracy of blind aspiration for studies of gastric content has been questioned by several authors (20,21) and has been a source of discussion in numerous studies (5-8,13). We used a larger multiorificed gastric tube (22F) than was used in many previous studies (5-8).Further, the suction system
94
HAAVIKETAL.
PREOPERATIVE ANXIETY AND GASTRIC VOLUME-ACIDITY
was modified to prevent excessive negative pressure and sticking of the tube to the gastric wall. We believe these measures, together with the fact that one investigator performed the majority of aspirations, minimized the systemic error of blind aspiration in our study. We used Merck pH paper for the pH measurements, which has a high degree of accuracy compared with electronic pH meters (12,19), something that is in accordance with our own experience. In summary, the results of this placebo-controlled study suggest that neither premedication with flunitrazepam and oxazepam in the present dosages nor the level of preoperative anxiety have any notable effects on gastric fluid volume and acidity. The mean gastric pH was C2.5 in all groups studied. Large proportions of patients in all groups had a combination of gastric fluid volume and acidity disposing for aspiration pneumonitis should regurgitation occur. Other measures than relieving preoperative anxiety must therefore be considered if the risk of aspiration pneumonitis is to be minimized.
References 1. Madej TM, Paasku RT. Anesthetic premedication: aims, assessment and methods. Can J Anaesth 1987;34:259-73. 2. Pakkanen A, Kangas L, Kanto J. A comparative study on the clinical effects of flunitrazepam and oxazepam as oral premedication. Int J Clin Pharmacol Ther Toxicol1981;19:275-8. 3. Male CG, Lim YT, Male M, et al. A comparison of three benzodiazepines for oral premedication in minor gynaecological surgery. Br J Anaesth 1980;52:429-35. 4. Hofstad B, Haavik PE, Wickstrem E, Steen PA. Benzodiazepines as oral premedication. A comparison between oxazepam, flunitrazepam and placebo. Acta Anesthesiol Scand 1987;31:2959. 5. Maltby JR, Sutherland AD, Sale JP, et al. Preoperative oral fluids: is a five-hour fast justified prior to elective surgery? Anesth Analg 1986;65:1112-6.
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