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ANALGESIA

Cardiac Arrest After Spinal Anesthesia in Thailand: A Prospective Multicenter Registry of 40,271 Anesthetics

Somrat Charuluxananan, MD^*, Somboon Thienthong, MD, Mali Rungreungvanich, MD, Thavat Chanchayanon, MD, Thitima Chinachoti, MD^||, Oranuch Kyokong, MD^*, and Yodying Punjasawadwong, MD^¶

From the *Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, Khon-Kaen University, Ramathibodi Hospital Mahidol University, Prince of Songkla University, ||Siriraj Hospital Mahidol University, and ¶Chiang Mai University, Thailand.

Address correspondence and reprint requests to Somrat Charuluxananan, MD, Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Pathumwan, Bangkok 10330, Thailand. Address e-mail to somratcu{at}hotmail.com.

Abstract

BACKGROUND AND OBJECTIVES: As part of the Thai Anesthesia Incidents Study of anesthetic adverse outcomes, we evaluated the incidence and factors related to cardiac arrest during spinal anesthesia.

METHODS: During a 12-mo period (March 1, 2003, to February 28, 2004), a prospective, multicenter registry of patients receiving anesthesia was initiated in 20 hospitals (7 university, 5 tertiary, 4 general, and 4 district hospitals) across Thailand. Anesthesia personnel reported patient-, surgery-, and anesthetic-related variables and adverse outcomes, including cardiac arrest during spinal anesthesia (defined as the time period from induction of spinal anesthesia until the end of operation). Adverse event specific forms were recorded within 24 h of an anesthetic procedure whenever a specific adverse event occurred. Univariate and multivariate analysis were used to identify factors related to cardiac arrest during spinal anesthesia. A P value <0.05 was considered significant.

RESULTS: In the registry of 40,271 cases of spinal anesthesia, there were 11 cardiac arrests, corresponding to an incidence of 2.73 (95% CI: 1.12–4.34) per 10,000 anesthetics. The mortality rate was 90.9% among patients who arrested. Among 11 patients who arrested, there were 5 cases of cesarean delivery and 6 cases of extremity surgery, including hip surgery. In 4 patients (36.3%), the anesthetic contributed directly to the arrest (high sympathetectomy, local anesthetic overdose, or lack of electrocardiography monitoring), whereas some arrests were associated with specific events (cementing of prosthesis, massive bleeding, suspected pulmonary embolism, and suspected myocardial infarction). From multivariate analysis, the risks of cardiac arrest during anesthesia were shorter stature (odds ratio 0.944 [95% CI: 0.938–0.951], P < 0.001), longer duration of surgery (odds ratio 1.003 [95% CI: 1.001–1.005], P = 0.002), and spinal anesthesia administered by the surgeon (odd ratio 23.508 [95% CI: 6.112–90.415], P < 0.001), respectively.

CONCLUSION: The incidence of cardiac arrest during spinal anesthesia was infrequent, but was associated with a high mortality rate. If the surgeon performed the spinal anesthetic, this was a significant factor associated with cardiac arrest. Increasing the number of anesthesiologists, improving monitoring guidelines for spinal anesthesia and improving the nurse-anesthetist training program may decrease the frequency of arrest and/or improve patient outcome.

The incidence and causes of cardiac arrest related to anesthesia in the perioperative period have been studied over two decades in many countries.1–6 However, much of the literature regarding cardiac arrest related to regional anesthesia involves retrospective studies or case reports.7–11 Few prospective surveys assessing a large number of patients have been published.12–14 The Royal College of Anesthesiologists of Thailand (RCAT) sponsors the Thai Anesthesia Incidents Study (THAI Study) of anesthetic adverse outcomes for evaluating incidences and factors related to anesthesia-related complications.15,16 In Thailand, spinal anesthesia may legally be conducted by board certified anesthesiologists or other physicians. The aims of this study were to determine the incidences and to identify risk factors for cardiac arrest during spinal anesthesia.

METHODS

The THAI Study of anesthetic adverse outcomes was a prospective multicenter study of consecutive anesthesia procedures performed in 20 hospitals (7 university hospitals: Chiang Mai University, Chulalongkorn University, Khon-Kaen University, Siriraj Hospital and Ramathibodi Hospital Mahidol University, Pramonkutklao Medical College, Prince of Songkla University), 5 tertiary hospitals (Buddhachinaraj Hospital, Ratchaburi Hospital, Nakorn Sri Thammarat Hospital, Khon Kaen Hospital, and Neurological institute), 4 general hospitals (Lampoon Hospital, Pichit Hospital, Baanpong Hospital, and Trang Hospital), and 4 district hospitals (Sanpatong Hospital, Nakorn-Thai Hospital, Kranuan Hospital, and Nampong Hospital) across Thailand. This study was approved by all institutional ethical review boards, with no additional written informed consent required.

For each patient undergoing a surgical procedure, the anesthesiologist or nurse-anesthetist completed a preplanned structured data collection form (Form 1: Appendix 1; available at www.anesthesia-analgesia.org) which included a series of patient-related, surgical-related, and anesthesia-related variables. Anesthesiologists or nurse-anesthetists completed Form 1 in addition to the usual anesthetic record. After constructing Form 1 and defining the variables, research staff and personnel were trained through workshops and internal audits. This form was piloted in six university hospitals before adoption at other sites with a 1-mo practice period before recruitment of each site in the registry. This study was confined to patients scheduled to receive spinal anesthesia only.

The attending anesthesia personnel were requested to record preoperative medical conditions, ASA physical status classification, demographic characteristics of the patients, and surgical procedure (classified by site of surgery). Patient monitors, main anesthetic technique, additional anesthetic technique, airway equipment, status of performer of anesthesia, and anesthetics used were also recorded. The anesthesia personnel or research nurses recorded all intraoperative cardiac arrests on Form 2 (Appendix 2; available at www.anesthesia-analgesia.org).

All forms were reviewed by a research nurse or site manager for completeness. Corrections were then made by each center, including the verification of any major event recorded. Incomplete forms after this step were not included in the study.

All Form 1s from each hospital during the 12-mo period between March 2003 to February 2004 were entered at the data management center at Chulalongkorn University with a double-entry technique to ensure the reliability of the database. All Form 2s (adverse events specific form) were reviewed by three independent senior anesthesiologists for the cause of cardiac arrest. Discrepancies among the three members were resolved by discussion.

The frequency of cardiac arrest during spinal anesthesia (from induction of spinal anesthesia until the end of operation) was calculated and presented with point estimates and 95% confidence intervals (CI). Comparison of categorical variables and continuous variables was done by using ² test and Student's t-test respectively. Binary logistic regression with a forward stepwise approach was then used to identify risk factors of cardiac arrest during spinal anesthesia. All analyses were performed with SPSS (version 11.5). In all cases, two-tailed tests were performed, and P value 0.05 was considered statistically significant.

RESULTS

Between March 1, 2003, and February 28, 2004, 172,697 anesthetic procedures were performed in 20 hospitals. Of these, 40,271 (23.3%) spinal anesthetics were conducted for 22,851 (56.7%) male, 17,382 (43.2%) female, and for 38 patients (0.1%) the gender date were missing. The frequency of ASA physical status classification 1, 2, 3, and 4 in patients receiving spinal anesthesia were 23,653 (58.7%), 14,603 (36.3%), 1892 (4.7%), and 123 (0.2%), respectively. Spinal anesthesia was scheduled for emergency conditions in 13,807 patients (34.3%). There were 11 cases of cardiac arrest during spinal anesthesia, with an incidence of 2.73 (95% CI: 1.14–4.34) per 10,000 spinal anesthetics and the mortality rate was 90.9%. The demographic, surgical, and anesthetic characteristics of patients, with and without cardiac arrest during spinal anesthesia in the registry, are presented in Table 1.

From univariate analysis, shorter stature (P = 0.041), longer duration of operation (P = 0.001), ASA physical status classification (P < 0.001), and status of performer of spinal block (P < 0.001) were statistically significant factors associated with cardiac arrest during spinal anesthesia. From multivariate analysis, the risks of cardiac arrest were shorter stature (odds ratio 0.944 [95% CI: 0.938–0.951], P < 0.001), longer duration of surgery (odds ratio 1.003 [95% CI: 1.001–1.005], P = 0.002), and surgeon as performer of spinal anesthesia (odds ratio 23.508 [95% CI: 6.112–90.415], P < 0.001), respectively.

There were two groups of patients who experienced cardiac arrest during spinal anesthesia: (1) general or orthopedic extremity surgery (nonobstetric group); (2) cesarean delivery patients (obstetric group). Characteristics of patients experiencing cardiac arrest during spinal anesthesia for extremity surgery and cesarean delivery are shown in Tables 2 and 3, respectively. The preoperative conditions of six patients in the nonobstetric group were diabetes mellitus (33%), ischemic heart disease (33%), abnormal electrocardiography or arrhythmia (50%), ASA physical status II (66%) and III (33%), respectively. There was no statistical difference in ASA physical status (P = 1.000), gender (P = 0.455), emergency condition (P = 0.080), and duration of surgery (P = 0.868) between the two groups, but the nonobstetric group had older age (67.8 ± 17.8 y vs 32.0 ± 6.4 y; P = 0.003), shorter onset of cardiac arrest since induction of spinal anesthesia with no statistical significant difference (36.5 ± 28.7 min vs 61 ± 74.8 min; P = 0.521), compared with the obstetric group.

The frequency of cardiac arrest during spinal anesthesia was 2.73 per 10,000 spinal anesthetics, which confirms previous studies reporting that cardiac arrest after spinal anesthesia is rare. Sprung et al. stated that the overall incidence of perioperative cardiac arrest was 4.3 per 10,000 for all types of anesthesia and 1.5 per 10,000 for patients receiving regional anesthesia.2 Auroy et al. reported an incidence of 6.4 cardiac arrests per 10,000 spinal anesthetics with a survival rate of 77%.14 Biboulet et al. reported 11 cardiac arrests among 101,769 anesthetics with an incidence of 6 cardiac arrests per 10,000 neuraxial anesthetics with only a 20% survival rate.17 Kopp et al. reported 2.9 cardiac arrest per 10,000 spinal anesthetics.11 Therefore, the incidence of cardiac arrest during spinal anesthesia in our study is comparable to those studies.

From univariate analysis, our study revealed that intraoperative cardiac arrest occurred frequently in shorter stature, higher ASA physical status patients, with longer duration of operation and when spinal anesthesia was performed by a surgeon. Likewise, from multivariate analysis shorter stature patients (odds ratio 0.944 [95% CI: 0.938–0.951]), longer duration of surgery (odds ratio 1.003 [95% CI: 1.001–1.005]), and surgeon as performer of spinal anesthesia (odds ratio 23.508 [95% CI: 6.11–90.415]) were statistically significant risk factors for intraoperative cardiac arrest. However, it is unlikely that patient height is a true risk for cardiac arrest, but rather a surrogate. For example, 9 of 11 patients having cardiac arrest were female. We also noted that longer surgical procedures were associated with cardiac arrest. However, our study was unique in identifying the surgeon a significant risk factor when he or she administered the spinal anesthetic, including a 23-fold increased likelihood of cardiac arrest. It is interesting that 5% of patients in this spinal anesthesia registry were anesthetized by surgeons because of a shortage of anesthesiologists (no anesthesiologist or few anesthesiologists in the hospital).

We separated patients who experienced cardiac arrest during spinal anesthesia into nonobstetric and obstetric groups. Our results are similar to those of Auroy et al. in which hip surgery was a common surgical procedure related to cardiac arrest.14 In the ASA closed claims project, Lee et al. also revealed that most nonobstetric neuraxial cardiac arrests were associated with surgical procedures in the lower extremity or the pelvis.10 As in previous surveys, we noted that the arrest often occurred well after establishment of spinal block (five of six patients) and was associated with intraoperative events, such as cementing of prosthesis or bone retraction.

Obstetric patients are a unique group of patients of similar age, ASA physical status, and physiology who routinely receive regional anesthesia. The subgroup analysis of cardiac arrest during spinal anesthesia in obstetric patients revealed a frequent incidence of 4.43 (95% CI: 0.5–8.3) per 10,000 spinal anesthetics with a high mortality rate of 80%. Two of five obstetric patients suffered cardiac arrest after significant bleeding from uterine atony. Moreover, severe hypovolemia may have made the resuscitation more difficult. The other three cases of cardiac arrest might have been due to a high level of sympathetic blockage. One of these patients received repeated intrathecal injections of 10 mg bupivacaine because of inadequate analgesia after the first spinal injection. Another patient had a cardiac arrest with an early onset of 5 min and the highest dermatome level had not been recorded. It is noteworthy that two of these patients were not monitored with electrocardiography during the prearrest period. Therefore, the lack of electrocardiography monitoring might have been cause of late detection of cardiac arrest resulting in a resuscitation failure. In these two cases, spinal anesthesia was performed by surgeons and monitored by nurse-anesthetists.

Fatal outcome from cardiac arrest occurred in 9 of the 11 cardiac arrests (90.9%) in our study. Sedation was not performed before any of the cardiac arrests, whereas 6 of 11 cardiac arrests were reported to have been preceded by bradycardia. In contrast, Caplan et al. reported 14 cases of fatal cardiac arrest during spinal anesthesia in which sedation was found to be a risk factor in 12 of those patients, whereas bradycardia was cited as an initial factor in 7 patients.7 Before the widespread use of pulse oximetry, it was argued that over-sedation played a key role in cardiac arrests during anesthesia. It is now difficult to invoke hypoxemia as the primary cause of cardiac arrests during spinal anesthesia because they frequently occur without evidence of oxygen desaturation. Although our study revealed a comparable incidence of cardiac arrest to a study by Kopp et al., our study had a higher mortality rate (90.9% vs 35%).11

It is noteworthy that 7 of 11 (63.6%) cardiac arrest patients received spinal anesthesia conducted by surgeons because of the shortage of anesthesiologists in Thailand. This result agreed with previous studies showing that lack of board-anesthesia certifications was associated with worse outcomes18 and that anesthesiologist-directed anesthesia care had a lower mortality rate.19 In Thailand, spinal anesthesia may be legally performed by anesthesiologists, medical doctors, or medical students under the supervision of anesthesiologists. In some rural hospitals, surgeons or anesthesiologists had to initiate regional anesthesia after which the nurse-anesthetist monitored the patients with noninvasive arterial blood pressure monitoring and/or pulse oximetry and/or electrocardiography according to the hospital's monitoring guidelines during the study period. The curriculum of the nurse-anesthetist training program requires 1-yr practice of a minimum of 100 general anesthetics. The practice of perianesthetic care after regional anesthesia is not included in the minimal requirement of this curriculum. Therefore, the possible explanations for high mortality rate in this study were as follows: (1) lack of anesthesiologists; (2) inability to manage the perianesthetic hemodynamics by nonanesthesiologists; (3) suboptimal monitoring, such as the absence of electrocardiography monitoring before cardiac arrest; (4) severe hypovolemia or massive bleeding; (5) suboptimal conditions during resuscitation, such as inadequately trained staff available for resuscitation; or (6) suboptimal care after resuscitation or system error, such as no space available in the intensive care unit.

The limitations of our study are: (1) there were missing data due to incompleteness of data collection as shown in the text and tables; (2) there was no autopsy in fatal cases because autopsy was not allowed by relatives of those patients; and (3) the three reviewers were not blinded as to the performer of the spinal anesthetic when they reviewed the incidents for causality. The lack of blinding may have biased the determination of causality. The impact of this registry in the THAI Study were as follows: (1) policy-maker in the Ministry of Public Health agreed to increase the number of anesthesiologists in Thai public hospitals; (2) the RCAT recommended pulse oximeters to be mandatory intraoperative monitoring in every patient receiving anesthesia instead of being optional; and (3) the RCAT issued clinical practice guidelines for spinal anesthesia and held training activities regarding perianesthetic care after spinal anesthesia for Thai anesthesia personnel.

In summary, this prospective multicenter registry showed that the occurrence of cardiac arrest during spinal anesthesia in Thailand was uncommon with an incidence of 2.73 per 10,000 anesthetics and high mortality rate for the arrests of 90.9%. Two major groups of patients having cardiac arrest during spinal anesthesia were patients undergoing cesarean delivery and surgery to the lower extremity. Surgeon as the performer of spinal anesthesia was a significant factor associated with the occurrence of cardiac arrest. The suggested strategies are to increase the number of anesthesiologists, improve monitoring guidelines, and improve the nurse-anesthetist training program to decrease the frequency of cardiac arrest during spinal anesthesia and/or improve patient outcome.

ACKNOWLEDGMENTS

The manuscript was edited for English by Mettanando Bhikkhu. This research was accomplished with the assistance of attending anesthesiologists and with the guidance of department heads at all sites in this multicenter study. The Royal College of Anesthesiologists of Thailand and the THAI Study group wish to express deep gratitude to project advisors Professor Chitr Sitthi-Amorn and Associate Professor Joranit Kaewkungwal for their encouraging criticism and advice. We also thank Professor Pyatat Tatsanavivat head of the Clinical Research Collaborative Network (CRCN) for continued support, encouragement, and helpful suggestions.

Footnotes

This article has supplementary material on the Web site: www.anesthesia-analgesia.org.

Accepted for publication April 3, 2008.

Supported by the Health Systems Research Institute (HSRI); Faculty of Medicine of Chiangmai University, Chulalongkorn University, Khon-kaen University, Mahidol University (Ramathibodi Hospital and Siriraj Hospital), Prince of Songkla University, and National Research Council of Thailand.

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This Article Abstract Full Text (PDF) Data Supplement Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Charuluxananan, S. Articles by Punjasawadwong, Y. Search for Related Content PubMed PubMed Citation Articles by Charuluxananan, S. Articles by Punjasawadwong, Y. Related Collections Cardiovascular Complications Outcomes Regional Anesthesia