Qualify Assurance m Health Care. Vol. 4. No. 4. pp. 289-303. 1992 Printed in Great Britain
1040-6166/92 $5.00 + 0.00 © 1992 Pergamon Press Ltd
OUTCOMES OF CARE FOR ANESTHESIA SERVICES: A PILOT STUDY Steven T. Fleming Assistant Professor Health Services Management University of Missouri-Columbia Columbia, MO 65211, USA
(First submitted 28 May 1991; accepted after revision 8 April 1992)
This paper describes a pilot study involving 4347 patient abstracts collected by anesthesia providers during the first quarter of1991 under the auspices of the American Association of Nurse Anesthetists. Descriptive statistics are presented on surgical site, type of provider and utilization of anesthetic agents as well as the prevalence of 87 preexisting conditions and the incidence of 103 adverse events. Key words: Quality assurance, quality of health care, anesthesia.
INTRODUCTION
Adverse outcomes associated with the use of anesthesia has been a topic of interest for over a hundred years since Snow published his monograph on the inhalation of ether in 1847 [1]. Hundreds of articles have appeared in the literature which purport to examine the adverse outcomes of anesthesia. The use of epidemiological methods in anesthesia has been explored by Lunn [2], whose work includes an excellent summary of the studies relating anesthesia to mortality. In the book edited by Hirsh et al. [3] important methodological advances are discussed, such as the critical incident technique, and the relationship between health care organization and anesthesia outcomes is demonstrated. A literature search for studies involving human subjects that were published in English during the time period 1981 through 1991 was conducted using MEDLINE. There were 207 citations during 1981 to 1985 and 239 citations between 1986 and 1990, including 23 studies which were classified as review articles. These reviews focus on either specific adverse outcomes, such as emesis [4], respiratory insufficiency [5] or perioperative myocardial infarction [6]; on specific types of patients, such as the elderly [7,8] or cardiac patients [9]; or on
First presented to the 8th Congress of ISQA. Washington, 29-31 May 1991.
289
290
S. T. Fleming
specific anesthesia methods including subdural anesthesia [10] and spinal anesthesia [11]. Out of the 239 citations between 1986 and 1990 40 (16.7%) were letters to the journal, virtually all of which were case studies involving a single patient. Forty-six (19.2%) others were empirical research. Of the remaining studies which appeared as journal articles 41 (17.1%) involved 10 or less patients, 48 (20.1%) between 11 and 100 patients, and 32 (13.4%) between 101 and 1000 patients. Only eight (3.3%) studies included more than 1000 patients, the point being that much of the research on anesthesia/anesthetics is based on very small patient cohorts. The 17 larger studies which included at least 500 patients are summarized in Table 1. Some of these studies focused on specific techniques, such as epidural [12] or caudal [13] anesthesia; specific anesthetics, such as nitrous oxide [16] or propofol [21]; or specific types of patients, such as hip fracture patients [14,26], coronary artery bypass patients [23] or women who had had a caesarian section [12]. Others compared regional anesthesia, such as subarachnoid blockage [14] or spinal [26], to general anesthesia, in terms of adverse outcomes. Most of these studies reported on a number of adverse outcomes, such as mortality [14,15,18,19,20,23,25,26] or nausea/vomiting [13,16,21], whereas some studies were concerned with a specific misadventure such as bronchospasm [17], post-operative urinary retention [24] or hepatitis [27].
DATA AND METHODS This study analyses data collected from the "Alpha Phase" of the Quality and Risk Management Practice Profile Clearinghouse and Data Processing Service of the American Association of Nurse Anesthetists (AANA). The file consists of 4347 patient records collected by participating anesthetists using a standardized form. Table 2 below presents the number of surgical episodes by site of care and by type of provider. In this sample most operations are performed in a surgical suite (78.3%) or ambulatory surgery center (11.9%) by a board certified surgeon (70.6%) or intern/ resident (17.5%). The primary anesthesia provider is typically a certified nurse anesthetist (67.0%) or student nurse anesthetist (26.8%). For each surgical episode, data are collected on respiratory, cardiovascular, central nervous system, gastrointestinal, endocrine/renal and other preexisting conditions. The particular type of anesthesia technique and agent is recorded as well as nearly 100 specific adverse outcomes. These outcomes are identified and categorized as either equipment failures, airway incidents or respiratory, cardiovascular, central nervous system, endocrine/renal or integumentary problems. These outcomes can be recorded at either the induction, maintenance, emergent or recovery stages. Patient characteristics are presented in Table 3 below in terms of pre-existing conditions. Note that, unlike discharge abstract data, these conditions are present prior to surgery and could therefore be used to measure the risk associated with patient health status. The most prevalent pre-existing conditions are smoking (26.7%), hypertension (22.5%), obesity (10.6%), obstructive respiratory disease (8.2%), diabetes (7.3%) and cancer (7.3%).
Outcomes of Anesthesia
291
Table 4 summarizes the choice of anesthetic technique and agents. In most cases general endotracheal anesthesia was the technique chosen (51.8%) whereas spinal anesthesia was done in 8.4% of the cases. Anesthetic agents are somewhat more difficult to analyse inasmuch as multiple agents were used in numerous different combinations. Table 4 lists the percentages of patients who received each of the agents (not necessarily alone). Most patients received either oxygen (93.4%) or air (4.2%) and one out of two patients was given nitrous oxide (47.7%). Isoflurane was the inhalation agent of choice (49.3%) whereas thiopental was selected most frequently as the induction agent (38.4%). In terms of muscle relaxants and benzodiazepines, succinylcholine (34.1%) and Midazolam (48.3%} had the highest use. The opioid fentanyl was given in six out of 10 cases. Iidocaine (26.7%) and Bipivacaine (11.9%) were the most frequently administered local anesthetics and a relaxant antagonist was given to 16.1% of the patients. Table 5 summarizes pre-induction and patient monitoring activities. This gives some indication of the variation in process of care with regards to the provision of anesthesia services. Note that some activities are carried out virtually all the time such as equipment checks (93.8%), obtaining patient consent (93.8%), BP cuff, stethoscope or electrocardiogram (EKG) (97.6%), and pulse oximetry (96.1%), while others are done much less frequently. For instance, only 11.4% of patients were monitored with mass spectrometry and 6.3% had an arterial line.
RESULTS Adverse outcomes of anesthesia can occur during one or more of the four stages, induction, maintenance, emergence and recovery. Table 6 presents the frequency of adverse outcomes during each of these stages for the 4347 patients in the study. The most frequent patient incidents are cardiovascular in nature: hypertension (67 cases), hypotension (72 cases) and sinus tachycardia (44 cases). Many of the conditions occurred in each of the four stages of anesthesia. Some outcomes such as hypertension and hypotension were most prevalent during the induction and maintenance stages. Laryngospasm occurred most frequently during the emergence stages (although the total numbers are small). Protracted nausea and vomiting tended to occur during the recovery phase. Tables 7 and 8 aggregate adverse outcomes across categories, such as respiratory and cardiovascular, and report the percentage of patients with at least one adverse outcome. Table 7 reports the relationship between adverse outcomes by category and elapsed time (under anesthesia and in surgery) as well as patient characteristics. One might expect more adverse outcomes to occur as elapsed time increases. The data offer some support for this hypothesis, particularly for respiratory and cardiovascular adverse outcomes. For those patients under anesthesia for less than 30 min, only 5.1% develop some adverse outcome. If the elapsed time increases to 4 hr or more, 16.2% of the patients experienced an adverse outcome. In terms of patient characteristics, the differences by sex are not striking. Although females had somewhat more respiratory, cardiovascular and central nervous system adverse outcomes, males had more airway incidents. One might predict more adverse outcomes as age increases. This relationship was not strong in
Four anesthesia protocols Many types
780
Muir [16]
Pedersen [18]
1016
92.1% general; 7.9% spinal/epidural
Various techniques
General anesthesia (493 cases) and regional anesthesia (7 cases)
500
Heino [15]
136,929
Hip fracture surgery
Subarachnoid blockage vs general anesthesia
538
Davis [14]
Olsson [17]
Pediatric
Caudal anesthesia
750
Dalens [13]
Many types
Many types
Renal transplantations
Coesarean section
Patient type
Epidural
Anesthetic techniques
993
Sample size
Many types
Bronchospasm
Nausea and vomiting
Cardiovascular and respiratory; mortality
28-day mortality rates
Breathing difficulty; post-op vomiting
Hypotension; blood transfusion
Adverse outcome(s)
Results Epidural failure: 2.5% total, 12% partial; blood transfusion less for epidural than for general anesthesia; 14.4% hypotension 96% caudal success rate; 94% of patients had light general anesthesia (12% breathing difficulties, 17% vomiting); motor block in 54% patients (10% had poor post-op tolerance) 28-day mortality; 6.6% subarachnoid, 5.9% general; 20.4% 1 year mortality; higher mortality due to: age, ischaemic heart disease, cardiac failure, perioperatived arrhythmias, poor ASA 49.6% hypotension; 26.8% hypertension; 9.4% cardiac arrhythmias; 2% pheumotorax; 2% haemothorax; 2% hydrothroax; 0.4% large haematomas; 2.2% pneumonia (only in general anesthesia); 0.6% mortality in first week post-op No association nitrous oxide and post-op nausea/vomiting; more nausea/vomiting: female gender, young age, previous post-op nausea/vomiting history; nausea or vomiting in 24 hr for four anesthesia groups (37.6%, 37.0%, 37.6%, 33.35%) 0.17% bronchospasm; for young (age 0-9) higher incidence if: pathological pre-op EKG (2.4%), obstructive lung disease (2.19%), ASA III (2.38%), tracheal intubation (0.91%) or rectal anesthesia (3.57%); for old (50-69) higher incidence if: airway obstruction (0.88.%), obstructive lung disease (0.77%), previous MI (54%), bronchoscopy (0.76%), mediastinoscopy (0.78%) 0.2% Life-threatening complications; 6% minor complications: 55% of respiratory failure patients died
Studies of anesthesia with 500 or more patients during 1986 to 1990
Crawford [12]
Study
TABLE 1.
50 loss 0.35% hepatitis (much higher than previous estimates) only 44.7% halothane; 9.3% Many types Hepatitis with halothane enflurane; 46% IV, spinal, epidural
85.7% general; 14.3% regional
MI, myocardial infarction; PMI, post-op MI; EKG, electrocardiogram.
2609
5220
Tammela [24]
1012
588
7306
Pedersen [19]
8
I I
a
294
S. T. Fleming TABLE 2.
Surgical episodes by site and provider
No. of episodes
(%)
Site of care Surgery suite Labor and delivery Birthing room Radiology Intensive care unit Other bospitaJ site Doctor's office Ambulatory surgical center Other outpatient site Missing or multiple sites
3405 140 3 6 2 14 132 518 58 69
(0.1) (
1040-6166/92 $5.00 + 0.00 © 1992 Pergamon Press Ltd
OUTCOMES OF CARE FOR ANESTHESIA SERVICES: A PILOT STUDY Steven T. Fleming Assistant Professor Health Services Management University of Missouri-Columbia Columbia, MO 65211, USA
(First submitted 28 May 1991; accepted after revision 8 April 1992)
This paper describes a pilot study involving 4347 patient abstracts collected by anesthesia providers during the first quarter of1991 under the auspices of the American Association of Nurse Anesthetists. Descriptive statistics are presented on surgical site, type of provider and utilization of anesthetic agents as well as the prevalence of 87 preexisting conditions and the incidence of 103 adverse events. Key words: Quality assurance, quality of health care, anesthesia.
INTRODUCTION
Adverse outcomes associated with the use of anesthesia has been a topic of interest for over a hundred years since Snow published his monograph on the inhalation of ether in 1847 [1]. Hundreds of articles have appeared in the literature which purport to examine the adverse outcomes of anesthesia. The use of epidemiological methods in anesthesia has been explored by Lunn [2], whose work includes an excellent summary of the studies relating anesthesia to mortality. In the book edited by Hirsh et al. [3] important methodological advances are discussed, such as the critical incident technique, and the relationship between health care organization and anesthesia outcomes is demonstrated. A literature search for studies involving human subjects that were published in English during the time period 1981 through 1991 was conducted using MEDLINE. There were 207 citations during 1981 to 1985 and 239 citations between 1986 and 1990, including 23 studies which were classified as review articles. These reviews focus on either specific adverse outcomes, such as emesis [4], respiratory insufficiency [5] or perioperative myocardial infarction [6]; on specific types of patients, such as the elderly [7,8] or cardiac patients [9]; or on
First presented to the 8th Congress of ISQA. Washington, 29-31 May 1991.
289
290
S. T. Fleming
specific anesthesia methods including subdural anesthesia [10] and spinal anesthesia [11]. Out of the 239 citations between 1986 and 1990 40 (16.7%) were letters to the journal, virtually all of which were case studies involving a single patient. Forty-six (19.2%) others were empirical research. Of the remaining studies which appeared as journal articles 41 (17.1%) involved 10 or less patients, 48 (20.1%) between 11 and 100 patients, and 32 (13.4%) between 101 and 1000 patients. Only eight (3.3%) studies included more than 1000 patients, the point being that much of the research on anesthesia/anesthetics is based on very small patient cohorts. The 17 larger studies which included at least 500 patients are summarized in Table 1. Some of these studies focused on specific techniques, such as epidural [12] or caudal [13] anesthesia; specific anesthetics, such as nitrous oxide [16] or propofol [21]; or specific types of patients, such as hip fracture patients [14,26], coronary artery bypass patients [23] or women who had had a caesarian section [12]. Others compared regional anesthesia, such as subarachnoid blockage [14] or spinal [26], to general anesthesia, in terms of adverse outcomes. Most of these studies reported on a number of adverse outcomes, such as mortality [14,15,18,19,20,23,25,26] or nausea/vomiting [13,16,21], whereas some studies were concerned with a specific misadventure such as bronchospasm [17], post-operative urinary retention [24] or hepatitis [27].
DATA AND METHODS This study analyses data collected from the "Alpha Phase" of the Quality and Risk Management Practice Profile Clearinghouse and Data Processing Service of the American Association of Nurse Anesthetists (AANA). The file consists of 4347 patient records collected by participating anesthetists using a standardized form. Table 2 below presents the number of surgical episodes by site of care and by type of provider. In this sample most operations are performed in a surgical suite (78.3%) or ambulatory surgery center (11.9%) by a board certified surgeon (70.6%) or intern/ resident (17.5%). The primary anesthesia provider is typically a certified nurse anesthetist (67.0%) or student nurse anesthetist (26.8%). For each surgical episode, data are collected on respiratory, cardiovascular, central nervous system, gastrointestinal, endocrine/renal and other preexisting conditions. The particular type of anesthesia technique and agent is recorded as well as nearly 100 specific adverse outcomes. These outcomes are identified and categorized as either equipment failures, airway incidents or respiratory, cardiovascular, central nervous system, endocrine/renal or integumentary problems. These outcomes can be recorded at either the induction, maintenance, emergent or recovery stages. Patient characteristics are presented in Table 3 below in terms of pre-existing conditions. Note that, unlike discharge abstract data, these conditions are present prior to surgery and could therefore be used to measure the risk associated with patient health status. The most prevalent pre-existing conditions are smoking (26.7%), hypertension (22.5%), obesity (10.6%), obstructive respiratory disease (8.2%), diabetes (7.3%) and cancer (7.3%).
Outcomes of Anesthesia
291
Table 4 summarizes the choice of anesthetic technique and agents. In most cases general endotracheal anesthesia was the technique chosen (51.8%) whereas spinal anesthesia was done in 8.4% of the cases. Anesthetic agents are somewhat more difficult to analyse inasmuch as multiple agents were used in numerous different combinations. Table 4 lists the percentages of patients who received each of the agents (not necessarily alone). Most patients received either oxygen (93.4%) or air (4.2%) and one out of two patients was given nitrous oxide (47.7%). Isoflurane was the inhalation agent of choice (49.3%) whereas thiopental was selected most frequently as the induction agent (38.4%). In terms of muscle relaxants and benzodiazepines, succinylcholine (34.1%) and Midazolam (48.3%} had the highest use. The opioid fentanyl was given in six out of 10 cases. Iidocaine (26.7%) and Bipivacaine (11.9%) were the most frequently administered local anesthetics and a relaxant antagonist was given to 16.1% of the patients. Table 5 summarizes pre-induction and patient monitoring activities. This gives some indication of the variation in process of care with regards to the provision of anesthesia services. Note that some activities are carried out virtually all the time such as equipment checks (93.8%), obtaining patient consent (93.8%), BP cuff, stethoscope or electrocardiogram (EKG) (97.6%), and pulse oximetry (96.1%), while others are done much less frequently. For instance, only 11.4% of patients were monitored with mass spectrometry and 6.3% had an arterial line.
RESULTS Adverse outcomes of anesthesia can occur during one or more of the four stages, induction, maintenance, emergence and recovery. Table 6 presents the frequency of adverse outcomes during each of these stages for the 4347 patients in the study. The most frequent patient incidents are cardiovascular in nature: hypertension (67 cases), hypotension (72 cases) and sinus tachycardia (44 cases). Many of the conditions occurred in each of the four stages of anesthesia. Some outcomes such as hypertension and hypotension were most prevalent during the induction and maintenance stages. Laryngospasm occurred most frequently during the emergence stages (although the total numbers are small). Protracted nausea and vomiting tended to occur during the recovery phase. Tables 7 and 8 aggregate adverse outcomes across categories, such as respiratory and cardiovascular, and report the percentage of patients with at least one adverse outcome. Table 7 reports the relationship between adverse outcomes by category and elapsed time (under anesthesia and in surgery) as well as patient characteristics. One might expect more adverse outcomes to occur as elapsed time increases. The data offer some support for this hypothesis, particularly for respiratory and cardiovascular adverse outcomes. For those patients under anesthesia for less than 30 min, only 5.1% develop some adverse outcome. If the elapsed time increases to 4 hr or more, 16.2% of the patients experienced an adverse outcome. In terms of patient characteristics, the differences by sex are not striking. Although females had somewhat more respiratory, cardiovascular and central nervous system adverse outcomes, males had more airway incidents. One might predict more adverse outcomes as age increases. This relationship was not strong in
Four anesthesia protocols Many types
780
Muir [16]
Pedersen [18]
1016
92.1% general; 7.9% spinal/epidural
Various techniques
General anesthesia (493 cases) and regional anesthesia (7 cases)
500
Heino [15]
136,929
Hip fracture surgery
Subarachnoid blockage vs general anesthesia
538
Davis [14]
Olsson [17]
Pediatric
Caudal anesthesia
750
Dalens [13]
Many types
Many types
Renal transplantations
Coesarean section
Patient type
Epidural
Anesthetic techniques
993
Sample size
Many types
Bronchospasm
Nausea and vomiting
Cardiovascular and respiratory; mortality
28-day mortality rates
Breathing difficulty; post-op vomiting
Hypotension; blood transfusion
Adverse outcome(s)
Results Epidural failure: 2.5% total, 12% partial; blood transfusion less for epidural than for general anesthesia; 14.4% hypotension 96% caudal success rate; 94% of patients had light general anesthesia (12% breathing difficulties, 17% vomiting); motor block in 54% patients (10% had poor post-op tolerance) 28-day mortality; 6.6% subarachnoid, 5.9% general; 20.4% 1 year mortality; higher mortality due to: age, ischaemic heart disease, cardiac failure, perioperatived arrhythmias, poor ASA 49.6% hypotension; 26.8% hypertension; 9.4% cardiac arrhythmias; 2% pheumotorax; 2% haemothorax; 2% hydrothroax; 0.4% large haematomas; 2.2% pneumonia (only in general anesthesia); 0.6% mortality in first week post-op No association nitrous oxide and post-op nausea/vomiting; more nausea/vomiting: female gender, young age, previous post-op nausea/vomiting history; nausea or vomiting in 24 hr for four anesthesia groups (37.6%, 37.0%, 37.6%, 33.35%) 0.17% bronchospasm; for young (age 0-9) higher incidence if: pathological pre-op EKG (2.4%), obstructive lung disease (2.19%), ASA III (2.38%), tracheal intubation (0.91%) or rectal anesthesia (3.57%); for old (50-69) higher incidence if: airway obstruction (0.88.%), obstructive lung disease (0.77%), previous MI (54%), bronchoscopy (0.76%), mediastinoscopy (0.78%) 0.2% Life-threatening complications; 6% minor complications: 55% of respiratory failure patients died
Studies of anesthesia with 500 or more patients during 1986 to 1990
Crawford [12]
Study
TABLE 1.
50 loss 0.35% hepatitis (much higher than previous estimates) only 44.7% halothane; 9.3% Many types Hepatitis with halothane enflurane; 46% IV, spinal, epidural
85.7% general; 14.3% regional
MI, myocardial infarction; PMI, post-op MI; EKG, electrocardiogram.
2609
5220
Tammela [24]
1012
588
7306
Pedersen [19]
8
I I
a
294
S. T. Fleming TABLE 2.
Surgical episodes by site and provider
No. of episodes
(%)
Site of care Surgery suite Labor and delivery Birthing room Radiology Intensive care unit Other bospitaJ site Doctor's office Ambulatory surgical center Other outpatient site Missing or multiple sites
3405 140 3 6 2 14 132 518 58 69
(0.1) (
