Society of Cardiovascular Anesthesiologists

PRO: Selective Early Extubation is Appropriate in Neonates and Infants

Laura K. Diaz, M.D.

Cook Children's Medical Center

Fort Worth, TX

The perioperative management of infants and children with congenital heart disease has evolved rapidly over the past several years with continuing advances in surgical, anesthetic and extra corporeal perfusion techniques. Early extubation after cardiac surgery has been well documented in adults ¹and children ^{2, 3} to avoid the potentially deleterious effects of mechanical ventilation, including laryngotracheal trauma, barotrauma or pneumothorax, mucus plugging, incorrect positioning or kinking of the endotracheal tube, accidental extubation, infection and pulmonary hypertensive crises secondary to manipulation or suctioning of the endotracheal tube ⁴. In addition, the postoperative use of sedative and analgesic drugs to facilitate tolerance of the endotracheal tube may also prolong the duration of intubation. In order to reduce or eliminate the adverse effects of prolonged intubation the concept of early extubation (in the operating room or within three hours of arrival in the ICU) in neonates and infants has been examined at our institution ⁶.

Early extubation is appropriate after cardiac surgery in many neonates and infants. A primarily opioid based anesthetic technique may be used with a morphine (Duramorph TM) caudal (50-70 mcg/kg) ⁵, and either fentanyl < 10 mcg/kg or remifentanil infusion. A low concentration of inhaled agent may be added as clinically indicated along with midazolam .1 mg/kg prior to cardiopulmonary bypass. Ultrafiltration during the rewarming phase of cardiopulmonary bypass allows the removal of priming and cardioplegic volume and a reduction in the concentration of inflammatory mediators that would otherwise contribute to postoperative edema and decreased pulmonary compliance ⁷. In the absence of severe pulmonary dysfunction, hemodynamic instability, excessive bleeding or anatomic concerns regarding the airway, the patient's neuromuscular blockade is reversed at the conclusion of surgery and he is allowed to awaken. Upon evidence of adequate ventilatory effort and satisfactory gas exchange the patient is extubated, either in the operating room or the ICU. Postoperative pain is managed by the pediatric intensivists, using fentanyl 1 mcg/kg/hr in incremental doses as clinically indicated. No patient in our experience thus far has required reintubation secondary to decreased ventilatory effort nor has there been a statistically significant difference in the overall rate of reintubation following initial extubation in those patients extubated early when compared to those patients ventilated postoperatively.

Successfully achieving early extubation in neonates and infants requires the close cooperation of the surgeon, anesthesiologist, perfusionist and pediatric intensivists. Patients operated on in the first week of life and those with single ventricle physiology undergoing an initial palliative procedure are less likely to be suitable for early extubation and special care should be taken in evaluating them prior to extubation. The most important factor involves approaching all patients as if they have the potential for early extubation and optimizing their intraoperative and perioperative management in order to achieve this goal. Our experience indicates that it is clearly safe in the proper setting to evaluate infants and neonates for early extubation following cardiac surgery ⁶. An anesthetic may easily be converted to a high dose narcotic technique should the patient prove unsuitable for extubation at the conclusion of surgery. However, when possible, early extubation can result in fewer pulmonary complications, a shorter ICU and hospital stay and a more positive convalescence for the patient and family.

References:

1. Karski JM: Practical Aspects of Early Extubation in Cardiac Surgery. J of Cardio and Vas Anes, Vol 9, No 5, Suppl 1 10/95: pp30-33

2. Barash PG, Lescovich F, Katz JD, Talner NS, Stansel HC: Early Extubation Following Pediatric Cardiothoracic Operation: A Viable Alternative. Ann Thorac Surg Vol 29 No 3, 1980

3. Schuller JL, Bovill JG, Nijveld A, Patrick MR, Marcelletti C: Early Extubation of the Trachea after Open Heart Surgery for Congenital Heart Disease. A review of 3 years' experience. Br. J. Anaesth. 56:1101, 1984

4. Heard GG, Lamberti JJ, Park SM, Waldman JD, Waldman J: Early Extubation after Surgical Repair of Congenital Heart Disease. Crit Care Med 1985; vol 13, no 10, pp 830

5. Rosen KR, Rosen DA: Caudal Epidural Morphine for Control of Pain Following Open Heart Surgery in Children. Anesthesiology 70:418-421, 1989

6. Heinle JS, Diaz LK, Fox LS: Early Extubation after Cardiac Operations in Neonates and Young Infants. J Thor Cardiovac Surg 1997; 114

7. Wang MJ, Chiu IS, Hsu CM, Wang CM, Lin PL, Chang CI, Huang Ch, Chu SH. Efficacy of ultrafiltration in removing inflammatory mediators during pediatric cardiac operations. Ann Thorac Surg 1996; 61:651-656.

CON: Early Extubation is Not Appropriate after Some Congenital Heart Surgery

Denise Joffe, MD

Children's Hospital of Pittsburgh

Pittsburgh, PA

The recent rediscovered trend in cardiac surgery is early extubation (in the operating room or within six hours of surgery) and this philosophy is extending to the pediatric and now neonatal populations. The driving force seems to be financial; it is felt that patients who are extubated early have shorter ICU and total hospital stays and therefore lower cost of care¹.

In order to be able to safely extubate a patient after congenital heart surgery, they should fulfill similar extubation criteria to the adult "fast track" cardiac patient. They must be breathing well, conscious enough to safely maintain an airway, hemodynamically stable, not bleeding, warm, and have a procedure amenable to early extubation ^{2, 3}. In addition, in the case of the pediatric patient, I argue that they must also be old enough. An infant is not a small adult, nor is a neonate a small infant. This is not a homogeneous group of patients. Pediatric patients have different cardiac lesions; the younger patients present with more serious disease and immature organ system development. Of the criteria listed above, not one is straightforward with the exception that few would argue about extubating a patient with an ongoing bleeding diathesis.

Extubation requires that the patient be awake enough to maintain an airway. The latter is easily within the realm of possibility. However, the younger the patient the more difficult it is to provide adequate pain relief without risking respiratory depression. Recently, caudal narcotics have been used with success; patients require minimal systemic narcotics for adequate analgesia. However, the study by Valley and Bailey⁴ demonstrated that patients less than 1 year old have an almost 10% risk of caudal narcotic induced respiratory depression that required treatment. In another study, a large percentage of patients treated with low dose intravenous morphine infusions alone were shown to have an elevated PaC02 (13-70%) ⁵. The elevated PaC02 in these patients coupled with studies that have demonstrated that patients up to a few weeks old exposed to high pulmonary pressures and flows have an increased incidence of pulmonary hypertensive crisis, suggest that narcotic induced hypoventilation may have dangerous cardiac consequences ⁶. It is not just a matter of monitoring these patients for the central nervous system effects of narcotic depression.

The neonate and infant are at a tremendous disadvantage when it comes to their baseline respiratory function. The entire respiratory system of the neonate is affected ⁷. Neonatal lungs behave physiologically like geriatric emphysematous lungs. They are overly compliant and prone to premature airway closure. The chest wall in babies is also very compliant and hinders inflation. Because of anatomic reasons, infants are prone to airway obstruction and when this happens, the chest wall collapses inward since it is "pulled" in by the negative pleural pressure. The addition of secretions or edema can dramatically increase the resistance to flow through their airways. The respiratory muscle fibers of infants are less endurance oriented and fatigue resistant than adults and are prone to muscle fatigue. Respiratory control is also immature. These patients do not respond to hypoxia or hypercarbia as well as adults. In addition to these baseline limitations, cardiopulmonary bypass, and a sternotomy, cause an increase in lung water, lung trauma, atelectasis, effusions, phrenic nerve dysfunction, respiratory muscle weakness and uncoordinated ribcage expansion ^{8, 9, 10}. This leads to further decreases in lung and chest wall compliance and function. In adults, these abnormalities have been shown to increase the work of breathing and 02 consumption by 20% ¹¹. Most lung volumes in adults have been shown to decrease by 30-50% post sternotomy ⁹. The neonate and small infant have 02 consumptions 2-3 times greater than adults. In addition, the majority of their lung volumes are at least 20 ml/kg less than adults. Thus one can assume a much lower degree of pulmonary reserve in the neonate. Although the pulmonary effects of cardiac surgery have not been well studied in the neonatal and infant population, their respiratory system have been shown to suffer even more derangements because of their immaturity ¹².

It is not clear when the noncompliant, rate-dependent myocardium of the neonate matures. During this transition there are many biochemical and metabolic changes that result in anatomic and functional development of the heart. The immature myocardium may be more susceptible to ischemia as demonstrated in some studies in which more intracellular injury occurred in neonates undergoing cardiac repairs than in older children. Postoperatively, the neonatal myocardium recovers slowly from the insult of surgery and cardiopulmonary bypass ⁶. Studies in neonates who underwent the arterial switch procedure have shown that almost all patients have a decrease in cardiac output at about six hours. The addition of afterload reduction and inotropic support help mitigate these adverse effects ⁶ and there is no reason to believe that the heart in neonates with other lesions recovers any differently. The increase in 02 consumption or decrease in 02 delivery present in the extubated patient can have devastating consequences. Although adult cardiac patients also demonstrate delayed postoperative decreases in cardiac output, the decrease is not as dramatic. Furthermore, although both adult and neonatal surgical groups undergo cardiopulmonary bypass, that is where the similarities stop. The typical neonatal procedure involves significant intracardiac remodeling, often a ventriculotomy, profound hypothermia, and often circulatory arrest.

Studies that have examined early extubation in infants and neonates have been disappointing. Neonates have not fared well^14-17. Serious complications resulting directly from early extubation have been reported. Furthermore, the reintubation rates have been up to 25%. Reintubations are not always the result of respiratory failure. The cardiorespiratory systems are so interrelated that this is not surprising. Studies make issue of the cost savings. However, serious problems with study design limit their conclusions. For example, studies categorize all patients together. However, neonatal patients cannot be compared to other children since their diseases are so different. It is indisputable that neonates are sicker patients, and their care regardless of time of extubation costs more.

At what age neonatal organs mature to the point when the benefits outweigh risks of early extubation is not known and deserves more study. Most older children have the advantage of having a "better" disease and it makes sense to consider early extubation. However, given the limitations of the neonate and young infant it makes no sense to me to test their reserve in an attempt to cut costs.

References:

1. Cheng DCH. Early extubation after cardiac surgery decreases intensive care unit stay and cost. J Cardiothorac Vasc Anesth 9:460-464, 1995

2. Karski JM. Practical aspects of early extubation in cardiac surgery. J Cardiothorac Vasc Anesth 9:30-33, 1995

3. Higgins TL. Safety issues regarding early extubation after coronary artery bypass surgery. J Cardiothorac Vasc Anesth 9: 24-29, 1995

4. Valley RD, Bailey AG. Caudal morphine for postoperative analgesia in infants and children: A report of 138 cases. Anesth Analg 72:120-124, 1991

5. Lynn Am, Nespeca MK, Opheim KE et al. Respiratory effects of intravenous morphine infusions in neonates, infants, and children after cardiac surgery. Anesth Analg 77:695-701, 1993

6. Casteneda AR, Jonas RA, Mayer et al. Perioperative Care. In: Cardiac Surgery of the Neonate and Infant. WB Saunders, Philadelphia, 1994

7. Motoyama EK. Respiratory physiology in infants and children in: Smith's anesthesia for infants and children. Mosby, Philadelphia, 1996

8. VanBelle AF, Wesseling GJ, Penn OC et al. Postoperative pulmonary function abnormalities after coronary artery bypass surgery. Respir Med 86:195-9, 1992.

9. Berrizbeitia LD, Tessler S, Jacobowitz IJ et al. Effects of sternotomy and coronary bypass surgery on postoperative pulmonary mechanics. Chest 96:873-6, 1989.

10. Shapira N, Zabatino SM, Ahmed S et al. Determinants of pulmonary function in patients undergoing coronary bypass operations. Ann Thorac Surg 50:268-73, 1990.

11. Wilson RS, Sulivan SF, Malm JR et al. The oxygen cost of breathing following anesthesia and cardiac surgery. Anesthesiology 99:387-93, 1973.

12. Serraf A, Robotin M, Bonnet N et al. Alteration of the neonatal pulmonary physiology after total cardiopulmonary bypass. J Thorac Cardiovasc Surg 114:1061-9, 1997

13. Mills AN, Haworth SG. Greater permeability of the neonatal lung. J Thorac Cardiovasc Surg 101:909-16, 1991

14. Heinle JS, Diaz LK, Fox LS. Early extubation after cardiac operations in neonates and young infants. J Thorac Cardiovasc Surg 114:413-8, 1997

15. Schuller JL, Bovill JG, Nijveld A et al. Early extubation of the trachea after open heart surgery for congenital heart disease. Br J Anaesth 56:1101-1108, 1984

16. Barash PG, Lescovich F, Katz JD et al. Early extubation following pediatric cardiothoracic operation: A viable alternative. Ann Thorac Surg 29:228-233, 1980

17. Heard GG, Lamberti JJ, Park SM et al. Early extubation after surgical repair of congenital heart disease. Crit Care Med 13:830-832, 1985

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