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EDITORIAL

When Assessing What We Know We Don't Know Is Not Enough: Another Perspective on Pediatric Outcomes

From the Department of Anesthesia, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania.

Address correspondence to Peter J. Davis, MD, Department of Anesthesia, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213. Address e-mail to davispj{at}anes.upmc.edu.

There are known knowns; there are things we know we know. We also know there are known unknowns. That is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know.

—Donald Rumsfeld, February 12, 2002

Two papers in this issue of Anesthesia & Analgesia report on the perioperative incidence of cardiac arrest in infants and children (1,2). These papers highlight strengths and weaknesses in our efforts to better define anesthetic outcomes in infants and children.

Bhananker et al. (1) present an update from the Pediatric Perioperative Cardiac Arrest (POCA) registry. Odegard et al. (2) report outcomes in a specific pediatric patient population (congenital heart disease patients) from a single institution. Both papers used databases to retrospectively analyze the numbers of perioperative cardiac arrests in children, and although both databases provide demographics, neither paper can truly associate causation with an effect.

These papers are windows into Rumsfeld's "unknown unknowns." Both papers question whether there are the correct assessment tools and infrastructure to determine the outcomes, and particularly the adverse outcomes, we don't know we don't know.

Bhananker et al.'s paper from the POCA registry serves as an update of the 1994–1997 perioperative cardiac arrests previously reported (1,3). The POCA registry captures voluntary reporting by institutions in a centralized registry. The present paper encompasses a 6-yr update period and extends the data from the original 1994 to 1997 publication (3). In the original report from 1994 to 1997, there were 63 participating institutions and 289 reported perioperative cardiac arrests (3). The present report captures data from more than 80 participating institutions in North America, and reports 397 perioperative cardiac arrests in pediatric patients undergoing both cardiac and noncardiac surgery. Of the 397 reported cardiac arrests, 193 cases (49%) were thought to be related to anesthesia care. Medication-related cardiac arrests accounted for 18% of all cardiac arrests, compared with those for 37% from 1994 to 1997 (P < 0.05). Cardiovascular causes of cardiac arrest were the most common (41%) of all arrests, with hypovolemia from blood loss and hyperkalemia from transfusion of stored blood the most common identifiable cardiovascular causes. Among respiratory causes of arrest (27%), airway obstruction from laryngospasm was the most common. The overall incidence of cardiovascular and respiratory causes did not appear to change from the earlier report. Vascular injury incurred during placement of central venous catheters was the most common equipment-related cause of arrest. There was a decrease in the number of ASA 1 and 2 cardiac arrests and arrests in infants <1 yr compared to the 1994–1997 report (1).

The limitations of a voluntary registry have been reported (3,4). These include accuracy of information (individuals reporting the cardiac arrest were not necessarily the individuals involved with the arrest) and selective reporting of cardiac arrests and other bad outcomes by institutions. By definition, the latter limitation can result in an unrepresentative sample of pediatric anesthetic practice. Additionally, such retrospective analysis can only determine association, not causation. However, the advantage of a voluntary reporting registry is that if enough institutions participate and adequate safeguards of data reliability can be ensured, important trends can be detected. Since the type of pediatric perioperative event that the registry follows is uncommon, multiple centers may be more reflective of the incidence of these uncommon events and, more importantly, may provide insight into causes for their occurrences.

Although registries allow large sample sizes to detect rare events, the question remains as to what one can learn from a databank where no true denominator or numerator can be ascertained? When comparing POCA data from 1994 to 1997 to the present paper, medication-related causes apparently declined. This was attributed to the decrease in cardiovascular depression associated with the decreased use of halothane and the increased administration of sevoflurane (1,3). However, no data support this conclusion. Specifically, we have no data on the number of anesthetics administered to children, or of the type of anesthetics used. An equally plausible explanation with different implications is the use of laryngeal mask airways in infants and young children. These airway devices, along with the more frequent use of spontaneous ventilation irrespective of the anesthetics, could also explain the findings. Thus, retrospective database analysis can offer insight into trends and help identify unknown unknowns, but provide little causal insight.

Analysis of data from a single institution suffers from a very different problem. Single-site data provide precise information on the numerator (every cardiac arrest, every cardiac anesthetic, every anesthetic with sevoflurane, etc.), and the denominator (total cases, total cardiovascular cases, total cases with halothane, etc.). However, the data only represent a single institution, and thus may not be representative of other pediatric practices.

The paper by Odegard et al. reports on children with congenital heart disease who have undergone corrective or palliative cardiac surgical repair at the Children's Hospital of Boston. This paper reports the incidence of cardiac arrest in patients whose anesthetics are managed by a select group of pediatric anesthesiologists. Patients who were unable to be weaned from cardiopulmonary bypass and patients anesthetized for diagnostic or interventional cardiac catheterization procedures were not included in the analysis. Data for these cardiac surgical patients were derived from the Boston Children's Hospital, the Boston Children's Hospital cardiac anesthesia department quality assurance system and the Boston Children's Hospital anesthesia billing system. Most impressive is the large number of patients undergoing surgery (>860/yr) and the incidence (0.79%) of cardiac arrests. Of the 41 cardiac arrests in this 6-yr period, 11 (26.8%) were determined to be likely related or possibly related to anesthesia. The mortality from the anesthesia-related cardiac arrests was zero (2).

How do the data of Odegard et al. compare to the single institution data recently published by Flick et al. from the Mayo Clinic (5)? Flick et al. reported on 92,881 anesthetics administered to children over a 17-yr period. For children having noncardiac procedures, 88,639 anesthetics were administered and 4242 anesthetics were administered to infants and children having cardiac procedures (both operative procedures and cardiac catheterizations). Flick et al. noted that the incidence of cardiac arrests in patients having noncardiac surgery was 26 in 88,639 anesthetics (2.9/10,000 anesthetics), while in patients undergoing cardiac procedures and excluding patients who could not be weaned off bypass, there were 17 arrests in 4205 patients (40.1/10,000 anesthetics). Of the 17 cardiac arrests, none was attributed to anesthesia causes (5). If we compare both institutions' cardiac anesthesia experiences, significant differences (79 vs 40.1 per 10,000 anesthetics) appear. In one institution, 26% of the arrests were anesthesia-related, and at the other, none was anesthesia-related. Is the care really better at one institution compared with the other?

Is it fair to compare these two institutions? Are we measuring the right outcomes and are we using the same language to define patient severity and to determine causation? Although both Odegard et al. and Flick et al. used ASA classification to categorize the patients, does the ASA status adequately classify children in physical status 3, 4, and 5 with congenital heart disease? Levels of agreement between the ASA PS classes by different anesthesiologists vary (6–8). Lack of agreement by anesthesiologists regarding ASA classification has also been noted in children (9). Is an otherwise healthy 7-yr-old child who is discovered during a school physical to have a murmur and needs open heart surgery to repair an atrial septal defect, an ASA 1, 2, 3, or 4? For pediatric cardiac surgical patients, what does it mean to attribute cardiac arrest to anesthetic causes? For patients with esophageal intubations or cardiac arrests that occur under controlled ventilation with the patient inspiring 5% halothane, the cause may be obvious. But what about the case of the congenital heart disease patient with single ventricle physiology, whose arrest occurs with a Pco₂ of 33 and PSO₂ 90. Is the increased Q_p:Q_s ratio an anesthesia-related cause of arrest? What if the patient undergoing a Stage 1 Norwood repair arrests while receiving low dose fentanyl? Is that an anesthesia-related event (10)? Odegard et al. noted that the surgical procedures with the highest association of arrest (truncus arteriosus, modified Blalock-Taussig shunt for pulmonary atresia with intact ventricular septum, neonates with coarctation and interrupted aortic arch with ventricular septal defect repair and Stage 1 palliation of hypoplastic left heart syndrome) are also the more technically and intellectually challenging anesthetics to manage with regard to balancing the systemic and pulmonary circulations. Might the anesthetic choices and/or anesthetic management decisions and not the surgical procedure, affect the likelihood of cardiac arrest or even the possibility of whether the patient did not come off bypass? Should physiology, not surgical procedure or ASA classification, be the risk factor? There are also nonuniform definitions of anesthesia-related causes of perioperative cardiac arrest in comparing the noncardiac surgical patients in the Bhananker et al. and Flick et al. papers (1,5). In the Bhananker et al. paper of the POCA Registry, the consequences of massive transfusion and embolic events were considered as anesthesia-related causes, but in the paper by Flick et al., this was not considered an anesthesia-related issue. Definitions and the use and meaning of words become important in how we assess problems. Consequently, we are left with two descriptions of observed events using definitions that are unique to each reporting institution.

At a time when technological advances make anesthesia record keeping and patient tracking less cumbersome, perhaps the time has come for us to have a central database that includes perioperative outcomes that are risk-adjusted. In this way, we can determine the number of anesthetics a year that are administered to children, the personnel who are involved in administering anesthesia to children, the effect of specialized pediatric training on the perioperative care of children, and whether subspecialty training and subspecialty practice (pediatric cardiac anesthesia) and case volume further enhance patient safety and patient outcome. As we ask these questions, we must first be prepared to develop a registry with meaningful outcomes. The registry must use outcomes that are risk adjusted, and must use language with common definitions.

We need not reinvent such a registry. Our surgical colleagues have established the National Surgical Quality Improvement Program (11–17), which provides data on comparative preoperative and risk-adjusted outcomes. They have created an infrastructure to monitor process improvement while proactively advancing patient safety. The National VA Surgical Risk Study validated preoperative risk factors and postoperative adverse events, and used these as tools for quality improvement in both the Veterans Affairs system hospitals as well as in private hospitals. Thirty-day mortality and morbidity rates decreased in the decade after the inception of the National Surgical Quality Improvement Program.

To advance the practice of pediatric anesthesia and surgery, surgeons and anesthesiologists must function as a team. The ultimate outcome involves the well-being of the patient. It is hard to believe that changes in pediatric cardiac arrest will evolve based solely on the development of new dugs. It is more likely that improvements in preventing perioperative cardiac arrest will evolve through changes in infrastructures that can monitor these events.

Our literature focuses on the known knowns and the known unknowns. However, our future depends on our knowing the currently unknown unknowns. It is time to develop uniform pediatric standards and centralize pediatric registries. It is time to establish benchmarks and implement these benchmarks to further improve care and patient safety for children. And it is time to develop the infrastructure to capture all outcomes in a way that permits exploration of trends and associations.

It is time to know the unknown unknowns.

	Footnotes

 
Accepted for publication April 19, 2007.

	REFERENCES

Top REFERENCES

 

1. Bhananker SM, Ramamoorthy C, Geiduschek JM, Posner KL, Domino KB, Haberkern CM, Campos JS, Morray JP. Anesthesia-related cardiac arrest in children: update from the pediatric perioperative cardiac arrest (POCA) registry. Anesth Analg 2007;105:344–50[Abstract/Free Full Text]
2. Odegard KC, DiNardo JA, Kussman BD, Shukla A, Harrington J, Casta A, McGowan FX, Hickey PR, Bacha EA, Thiagarajan RR, Laussen PC. Frequency of anesthesia-related cardiac arrest in patients with congenital heart disease undergoing cardiac surgery. Anesth Analg 2007;105:335–43[Abstract/Free Full Text]
3. Morray JP, Geiduschek JM, Ramamoorthy C, Haberkern CM, Hackel A, Caplan RA, Domino KB, Posner K, Cheney FW. Anesthesia-related cardiac arrest in children: Initial findings of the Pediatric Perioperative Cardiac Arrest (POCA) Registry. Anesthesiology 2000;93:6–14[Web of Science][Medline]
4. Morray J, Posner K. Pediatric perioperative cardiac arrest. Anesthesiology 2007;106:207–8[Web of Science][Medline]
5. Flick RP, Sprung J, Harrison TE, Gleich SJ, Schroeder DR, Hanson AC, Buenvenida SL, Warner DO. Perioperative cardiac arrests in children between 1988 and 2005 at a tertiary referral center. Anesthesiology 2007;106:226–37[Web of Science][Medline]
6. Owens WD, Felts JA, Spitznagel EL Jr. ASA Physical Status Classifications: a study of consistency of ratings. Anesthesiology 1978;49:239–43[Web of Science][Medline]
7. Mak PH, Campbell RC, Irwin MG. The ASA Physical Status Classification: inter-observer consistency. Anaesth Intensive Care 2002;30:633–40[Web of Science][Medline]
8. Davenport DL, Bowe EA, Henderson WG, Khuri SF, Mentzer RM. National surgical quality improvement program (NSQIP) risk factors can be used to validate American Society of Anesthesiologists Physical Status Classification (ASA PS) Levels. Ann Surg 2006;243:636–44[Web of Science][Medline]
9. Aplin S, Baines D, DeLima J. Use of the ASA physical status grading system in pediatric practice. Paediatr Anaesth 2007;17:216–22[Medline]
10. Hickey PR, Hansen DD. High Dose fentanyl reduces intraoperative ventricular fibrillation in neonates with hypoplastic left heart syndrome. J Clin Anesth 1991;3:295–300[Medline]
11. Daley J, Henderson WG, Khuri SF. Risk-adjusted surgical outcomes. Annu Rev Med 2001;52:275–87[Web of Science][Medline]
12. Khuri SF. Safety, Quality, and the National Surgical Quality Improvement Program. Am Surg 2006;72:994–8[Web of Science][Medline]
13. Khuri SF, Daley J, Henderson W, Hur K, Demakis J, Aust JB, Chong V, Fabri PJ, Gibbs JO, Grover F, Hammermeister K, Irvin G, McDonald G, Passaro E, Phillips L, Scamman F, Spencer J, Stremple JF. The participants in the National VA Surgical Quality Improvement Program. Ann Surg 1998;228:491–507[Web of Science][Medline]
14. Best WR, Khuri SF, Phelan M, Hur K, Henderson WG, Demakis JG, Daley J. Identifying patient preoperative risk factors and postoperative adverse events in administrative databases: results from the Department of Veterans Affairs National Surgical Quality Improvement Program. J Am Coll Surg 202;194:257–66
15. Daley J, Khuri SF, Henderson W, Hur K, Gibbs JO, Barbour G, Demakis J, Irvin G, Stremple JF, Grover F, McDonald G, Passaro E, Fabri PJ, Spencer J, Hammermeister K, Aust JB, Oprian C; for participants in the National VA Surgical Risk Study. Risk adjustment of the postoperative morbidity rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study. J Am Coll Surg 1997;185:339–52
16. Khuri SF, Daley J, Henderson W, Hur K, Gibbs JO, Barbour G, Demakis J, Irvin G, Stremple JF, Grover F, McDonald G, Passaro E, Fabri PJ, Spencer J, Hammermeister K, Aust JB; for the participants in the National VA Surgical Risk Study. Risk adjustment of the postoperative mortality rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study. J Am Coll Surg 1997;185:325
17. Stoelting RK, Khuri SF. Past accomplishments and future directions: risk prevention in anesthesia and surgery. Anesthesiol Clin North Am 2006;24:235–53

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