Frequency of intraoperative cardiac arrest and medium-term survival

CONTEXT AND OBJECTIVE: Although advances in surgical and anesthetic techniques have reduced perioperative morbidity-mortality, the survival rate following cardiac arrest remains low. The aim of this study was to evaluate, over the course of one year, the prevalence of intraoperative cardiac arrest and the 30-day survival rate after this event in a tertiary teaching hospital. DESIGN AND SETTING: Prospective cohort study in a tertiary teaching hospital. METHODS: Following approval by the institutional ethics committee, anesthetic procedures and cases of intraoperative cardiac arrest between January and December 2007 were evaluated. Patients undergoing cardiac surgery were excluded. The data were gathered prospectively using the modified Utstein model, with evaluation of demographic data, pre-arrest conditions, intraoperative care, care during arrest and postoperative outcome up to the 30th day. The data were recorded by the attending anesthesiologist. RESULTS: During the study period, 40,379 anesthetic procedures were performed, and 52 cases of intraoperative cardiac arrest occurred (frequency of 13:10,000). Among these, 69% presented spontaneous return of circulation after the initial arrest, and only 25% survived for 30 days after the event. The following factors were associated with shorter survival: American Society of Anesthesiologists physical status IV and V, emergency surgery, hemorrhagic events, hypovolemia as the cause of arrest and use of atropine during resuscitation. CONCLUSIONS: Although the frequency of cardiac arrest in the surgical environment has declined and resources to attend to this exist, the survival rate is low. Factors associated with worst prognosis are more frequent in critical patients.


INTRODUCTION
Despite great advances in intraoperative physiological monitoring and surgical anesthesia techniques, perioperative cardiopulmonary arrest (CPA) is still the most catastrophic complication during surgery and compromises the postoperative recovery of many patients.The mechanisms relating to intraoperative CPA differ from those responsible for out-of-hospital events.
[3][4][5][6] However, it is difficult to assess the quality of cardiopulmonary resuscitation (CPR) because of an absence of standardized templates for describing resuscitation efforts and for classifying the intraoperative complexity of such cases.Furthermore, limited data are available regarding the predictors of CPA survival and 30-day clinical outcomes.
In 1990, a group of CPR experts met at the International Resuscitation Conference in Utstein, Norway, and developed a set of guidelines, known as Utstein-style reporting, to standardize CPR reports. 7On the basis of these consensus guidelines, we developed a questionnaire to assess cases of intraoperative CPA.

OBJECTIVE
The aim of this study was to evaluate the frequency and outcomes of intraoperative CPA cases over a one-year period in a tertiary teaching hospital, using Utstein-style reporting.

METHODS
Following approval by the institutional ethics committee for human research, the CPA frequency was evaluated in the operating rooms or diagnostic procedure rooms of all the units of the hospital.

Design and location
This was a prospective single-center cohort study, in a tertiary teaching hospital.

Sample size:
A time-limited convenience sample was used, covering the period from January to December 2007 and totaling 40,379 anesthetic procedures.

Inclusion criteria
Among all the patients who underwent surgical anesthetic procedures, including regional anesthesia alone, those who experienced CPA and were subjected to cardiopulmonary resuscitation maneuvers with external or internal thoracic compressions and/or those who underwent cardiac defibrillation were included in the study.

Exclusion criteria
Patients who were undergoing cardiac surgery and those who did not receive CPR were excluded.In addition, "do not resuscitate" (DNR) cases were not included.The criteria for DNR were defined previously, in cases of palliative care undergoing minor surgeries for supportive procedures; or in the operating room, by the surgical team, in cases of failure of all life support efforts before the cardiac arrest.

Intervention and outcome
Cardiac arrest was defined as the cessation of cardiac mechanical activity, as determined by the absence of a palpable central pulse.Patients experiencing CPA were treated using advanced cardiac life support (ACLS) maneuvers.Among the patients with more than one cardiac arrest, only the first arrest was analyzed.
A data-gathering form, based on the Utstein model, 8,9 was completed during and after each cardiac arrest by the attending anesthesiologist, together with one of the present authors.This form was used to collect information relating to the following: age; gender; preoperative clinical status, i.e. the American Society of Anesthesiologists (ASA) physical status, including the hemodynamic conditions, presence of infection and use of sedation and mechanical ventilation; types of anesthetic drugs used; type of surgery; clinical signs and symptoms before, during and after CPA; causes of CPA; interventions during CPR; and patient outcome.All patients were followed up on a daily basis until the 30 th day after the event or until the patient's death.
For the primary aim of this study, the frequency of cardiac arrest was defined as the number of occurrences of this adverse event divided by the total number of anesthetic procedures performed in the hospital over the period considered.From the anesthesia records and the data-gathering form, the causes of cardiac arrest and death were retrospectively assigned by three of the present authors as one of the following: entirely related to anesthesia when anesthesia was the only or the major contributory factor; partially related to anesthesia when the patient's disease/condition or the surgical procedure was a contributory factor, but anesthesia represented an additional factor; entirely related to surgery; or entirely related to the patient's disease/condition. 10The cause of the event was deemed to have been established when there was a majority conclusion.There was some discussion in relation to a few cases.
The outcome was evaluated in terms of the return of spontaneous circulation, 24-hour and 30-hour survival after the procedure, and the Glasgow Coma Scale score 30 days after surgery.

Statistical analysis
Quantitative values were presented as means ± standard deviation (SD), and discontinuous values as percentages.Quantitative values were compared using the two-sided, unpaired Student's t test or Mann-Whitney U test for non-Gaussian distributions.
Discontinuous variables were compared using chi-square tests or Fisher's exact test, as indicated.All data analyses were performed using the Statistical Package for the Social Sciences (SPSS) software (version 17.0, SPSS Inc., Chicago, United States) for Windows.Differences with P < 0.05 were considered statistically significant.

RESULTS
Between January and December 2007, 40,379 anesthetic procedures were performed, and 52 cases of intraoperative cardiac arrests occurred (a frequency of 13:10,000).The frequency of CPA for each unit of the hospital is presented in Table 1.The CPA frequency was highest in the Central Institute, which is the site of the emergency and trauma unit, where it was 15:10,000 for emergency cases.This frequency was associated with shorter survival than in elective cases (P = 0.008).Excluding the emergency cases, the CPA frequency among the elective cases in the Central Institute was similar to that of the other units (5:10,000).
The presence of hemorrhagic events before or during surgery (P = 0.024) also correlated with reduced survival.Overall, the incidence of deaths that occurred up to 30 days after CPA was 10 per 10,000 anesthetic procedures.
Forty-eight cases of CPA occurred in adults (92%), and four cases occurred in children (8%).The distribution of CPA according to gender and age among adults and children is presented in Table 2, along with the patients' preexisting conditions.Among these, preoperative hypertension, heart failure and renal insufficiency, were the most prevalent ones.The more decompensated the basal disease or general clinical condition was, more frequently it led to decreased survival, as shown in Table 3 (P = 0.002 for ASA physical status IV and V, compared with ASA  The data are presented as number (n) and percentage (%) or means ± standard deviation (SD).COPD = chronic obstructive pulmonary disease.
ASA classification: I = a normal healthy patient; II = a patient with mild systemic disease; III = a patient with severe systemic disease; IV = a patient with severe systemic disease that is a constante threat to life; V = a moribund patient who is not expected to survive without the operation; VI = a declared brain-dead patients whose organs are being removed for donor puposes.adverse event and anesthesia.According to the classifications used in this study, 10 the majority of the cases were considered to be completely related to the patient's condition or only partially related to the anesthesia.Cardiac arrest attributable to anesthesia occurs in 0.5 to 1.0 case per 10,000 interventions, 5,11 with higher incidence in pediatric cases (1-5 per 10,000), 11 but also higher survival rates. 5This information suggests that the patient's age, preexisting diseases or traumas and new surgical interventions play important roles in the risk of CPA.The results from the present study did not indicate any association between age and outcome.

ASA
Understanding "anesthesia-related/caused" mortality remains challenging. 12Increasing the awareness of the rate of perioperative mortality, and specifically anesthesia-related mortality, may improve the ability to predict which patients are at increased risk of cardiac arrest and to provide the management necessary to prevent this adverse event or to improve the outcome. 13 Use of atropine during resuscitation efforts was associated with higher mortality in our study.The available evidence suggests that routine use of atropine during cardiac arrest treatment is unlikely to provide a therapeutic benefit. 14Recently, atropine was removed from the cardiac arrest algorithm, in the 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. 15 observed that although return of spontaneous circulation occurred frequently, it was not related to a better outcome, considering that only 36.1% of those patients achieved 30-day survival.The high incidence of pulseless electrical activity could be related to hypovolemia, which was the most frequent cause of CPA in this study.The poor neurological outcomes observed in this study provide corroboration that there is a need to improve postarrest care, as emphasized in the 2010 American Heart Association Guidelines. 15

CONCLUSIONS
Our findings indicate that the frequency of intraoperative cardiac arrest is decreasing and are in accordance with previous data.
Additionally, intraoperative cardiac arrest was seen to be related to high mortality, especially in patients with previous comorbidities, emergency procedures, hypovolemia, respiratory complications and metabolic/electrolytic disturbances.

Table 1 .
Frequency of cardiopulmonary arrest (CPA) during anesthetic procedures according to hospital unit SC = surgical center; En = endoscopy; ECT = electroconvulsive therapy.

Table 2 .
Patients' characteristics before cardiac arrest

Table 3 .
American Society of Anesthesiologists (ASA) physical status classification and type of surgery.Numbers of patients and survival at 30 days, n (%)