Postoperative ByBarbara
Apnea in Infants
Naylor, Jayant Radhakrishnan, and Desmond McLaughlin Park Ridge, Illinois and Chicago, Illinois
l This is a review of 127 neonates evaluated for postoperative apnea and bradycardia (A&B) after inguinal surgery. The patients could be divided into three groups based on postconceptional age (PCA) at operation. Ten of 29 patients operated on at PCA of 33 to 39 weeks developed episodes of A&B. Preoperative assessment was not reliable in their identification. In the second group of 54 patients at PCA 40 to 44 weeks, 9 developed A&B, whereas in the third group of 44 patients at PCA of 45 to 50 weeks 1 patient developed A&B. In the latter two groups preoperative assessment identified all patients at high risk. We conclude that after PCA of 40 weeks patients at risk for A&B can be identified preoperatively. Patients operated on up to 39 weeks PCA should all be observed in the hospital. Copyright o 1992 by W.B. Saunders Company INDEX WORDS:
Apnea, bradycardia,
postoperative.
S
TEWARD’S observation that expremature infants have a high incidence of postoperative apnea has taken on great importance with the increasing popularity of outpatient surgery. Kurth et al2 reported that preterm infants were at high risk up to 60 weeks postconceptional age (PCA) and recommended monitoring for at least 12 hours postoperatively. We undertook this retrospective review because it was our impression that unexpected episodes of apnea and bradycardia (A&B) were uncommon. MATERIALS AND METHODS At our hospital we monitor all expremature infants up to a PCA of 60 weeks and all full-term infants up to a PCA of 44 weeks for postoperative apnea with continuous pulse oximetry and apnea monitors. This study group consisted of expremature and full-term infants meeting the above admission criteria who underwent inguinal surgery between 1984 and 1991 by one surgeon (J.R.). Patients circumcised under the same anesthetic were included but patients subjected to other major procedures concomitantly were excluded. Charts were reviewed for the following information: gestational age, birth weight, weight at operation, Apgar scores, PCA at operation, associated medical conditions and medications, presence or absence of home apnea monitoring, ASA physical status, anesthesiologist, anesthetic techniques and agents used, operative procedure, and operating time. Presence of postoperative apnea and/or bradycardia in the first 24 hours postoperatively and measures used to terminate these episodes were recorded. Charts of hospitalized patients were also reviewed for evidence of A&B in the 24 hours immediately prior to operation. Apnea was defined as episodes lasting greater than 10 seconds and bradycardia was defined as a heart rate below 80 beats/min. RESULTS
One hundred twenty-seven ASA physical status I to IV patients met the above criteria (107 boys and 20 girls). One hundred two were exprematures, whereas Journal of Pediatric Surgery, Vol27,
No 8 (August),
1992:
pp 955-957
Table 1. Patient Population GrLXlp
PCA bk)
I
33-39
29
25
it
40-44
54
38
III
45-60
44
39
127
102
Tota
I
Total
Premature
25 were full-term infants. Seventy-one patients were admitted for monitoring. A majority of the remaining 56 patients who were hospitalized were premature infants having elective herniorrhaphies prior to discharge. There was no death or serious morbidity in the study. Immediate postoperative reintubation was required in 1 patient. Postoperative A&B was noted in only 19 (15%) patients, all of whom were exprematures. Based on PCA our patients could be divided into three groups (Table 1). Ten of 29 (34.5%) of group I patients developed postoperative A&B (Table 2). Seven of these 10 were considered high risk by preoperative evaluation. Three patients developed postoperative A&B without any preoperative indication of risk factors. Conversely there were 6 patients whose preoperative evaluation rendered them in the high-risk category yet they did not develop postoperative problems. Eight of 54 (14.8%) patients in group II who demonstrated postoperative A&B were all identified as high-risk patients based on one or more of the following: history of A&B, anemia (hemoglobin < 10 g%), chronic respiratory disease, or need for theophylline. All episodes of A&B either resolved spontaneously or responded to stimulation. In addition, there were 7 patients with preoperative indicators who did not develop postoperative A&B. No patient in this group developed postoperative A&B if preoperative indicators were absent. Of 44 patients in group III, the only patient who developed postoperative A&B had chronic renal failure and anemia at the time of operation. He had one short episode that resolved From the Lutheran General Hospital. Pork Ridge. IL, and the University of Chicago, Chicago, IL. Presented at the Jens G. Rosenkranz Resident Competition at the 43rd Annual Meeting of the Surgical Section of the American Academy of Pediatrics, New Orleans, Louisiana, October 26-27, 1991. Address reprint requests to Jayant Radhakrishnan, MD, 2454 E Dempster, Suite 406. Des Plaines, IL 60016. Copyright o I992 by W.B. Saunders Company 0022-3468/92/2708-0004$03,00l0 955
NAYLOR, RADHAKRISHNAN.
956
Table 2. Group
I (PCA
Table 3. Groups II and Ill
33 to 39 Weeks)
Total
29
A&B
10 (34.5%)
Group II (PCA 40 to 44 weeks) Total Postoperative A&B
Postoperative A&B without preoperative 3
indicators
AND McLAUGHLlN
54 8 (14.8%)
Group III (PCA 45 to 60 wk) Total Postoperative A&B
spontaneously. Twelve other patients with preoperative risk factors did not demonstrate any postoperative problems (Table 3). Therefore, correlation was seen between postoperative A&B and gestational age, PCA, associated medical conditions, need for preoperative apnea monitoring and medications, and ASA physical status. There was no correlation with birth weight, weight at surgery, operative procedure, operating time, presence or absence of endotracheal intubation, the type of anesthetic agent used, and the anesthesiologist carrying out the procedure. DISCUSSION
In 1982 Steward’ reported that 6 of 33 expremature infants under 48 weeks PCA had episodes of apnea after herniorrhaphy, whereas no such episodes occurred in 38 full-term infants. Following this report other studies attempted to define the risk of prematurity3” and anemia.6 The use of spinal anesthesia7,8 and caffeine9 have been suggested to reduce this risk. The above-mentioned authors only found evidence of increased apnea in the early postoperative period in expremature infants up to 48 weeks PCA. In 1987 Kurth et al* reported unexpected life-threatening episodes in 6 of 24 infants 49 to 60 weeks PCA causing serious concern that many older expremature infants may be unsuitable for outpatient anesthesia. We believe this discrepancy occurred because they included patients with serious medical problems in their series and also used the same patient on more than 1 occasion. Patients requiring placement of ventriculoperitoneal shunts or central lines, or being subjected to laparotomy can not be compared with those who undergo outpatient surgery. Additionally, the use of the same patient twice falsely increases the incidence of postoperative A&B. To compare our results with theirs we regrouped exprematures by the same age cut-offs and we redefined prolonged A&B as that lasting more than 15 seconds or requiring resuscitative measures such as reintubation or me-
44 1 (2.3%)
NOTE. All patients in groups II and Ill with postoperative A&B had preoperative indicators and were exprematures.
chanical ventilation. In our series prolonged apnea only occurred in infants under 42 weeks PCA. Furthermore, only 3 of 50 expremature infants 43 to 60 weeks PCA and 1 of 24 infants 49 to 60 weeks PCA had any such episodes. Kurth et al2 reported A&B in 13 of 36 in the 43- to 60-week group and 8 of 24 in the 49- to 60-week group, with 10 of 13 episodes being “prolonged.” Using Fisher’s exact test, our results are significantly different (P < .OOl for the 43- to 60week group and P < .03 for the 49- to 60-week group). Our findings are consistent with those of Melone et a1,l0 who, in a similar study, looked at 124 expremature infants up to 59 weeks PCA undergoing inguinal herniorrhaphy and saw brief episodes of A&B in only 4 patients, none of which resulted in serious morbidity. Bell et al” cautioned that a few apneic events are missed when infants are monitored using real-time apnea monitoring and intermittent nursing observation but the significance of these short apneic events is not clear. Finally, neither our study nor those of otherG3-11 demonstrated postoperative A&B in fullterm patients as reported by Kurth et al* and Tetzlaff et al.‘* The latter authors presented a case report of significant postoperative apnea in a full-term baby at 42 weeks PCA after two separate operations for congenital cataracts. Therefore, we believe that the following conclusions are warranted: (1) there is an increased incidence of A&B in all infants under 39 weeks PCA; hence, all these infants should be monitored in hospital for 24 hours postoperatively; and (2) expremature infants over 39 weeks PCA are at a higher risk of postoperative A&B only if they have preoperative indicators such as a history of A&B, hemoglobin below 10 g%, chronic respiratory disease, or are taking theophylline at the time of operation.
REFERENCES 1. Steward DJ: Preterm infants are more prone to complications following minor surgery than are term infants. Anesthesiology 56:304-306,1982 2. Kurth CD, Spitzer AR, Broennle AM, et al: Postoperative apnea in preterm infants. Anesthesiology 66:483-488, 1987
3. Liu LMP, Cote CJ, Goudsouzian NG, et al: Life-threatening apnea in infants recovering from anesthesia. Anesthesiology 59:506510,1983 4. Welborn LG, Ramirez N, Oh TH, et al: Postanesthetic apnea and periodic breathing in infants. Anesthesiology 65:658-661,1986
POSTOPERATIVE
APNEA IN INFANTS
957
5. Tashiro C, Matsui Y, Nakano S, et al: Respiratory outcome in extremely premature infants following ketamine anaesthesia. Can J Anaesth 38:287-291,199l 6. Welborn LG, Hannallah RS, Luban NLC, et al: Anemia and postoperative apnea in former preterm infants. Anesthesiology 74:1003-1006.1991 7. Welborn LG, Rice LJ, Hannallah RS, et al: Postoperative apnea in former preterm infants: Prospective comparison of spinal and general anesthesia. Anesthesiology 72:838-842,199O 8. Webster AC. McKishnie JD. Kenvon CF. et al: Suinal , anesthesia for inguinal hernia repair in high-risk neonates. Can J Anaesth 38:281-286, 1991
9. Welborn LG, Hannallah RS, Fink R, et al: High-dose caffeine suppresses postoperative apnea in former preterm infants. Anesthesiology 71:347-349, 1989 10. Melone JH, Schwartz MZ, Tyson KRT: Outpatient inguinal herniorrhaphy in premature infants: Is it safe? J Pediatr Surg 27:203-208,1992 11. Bell C, Dubose R, Seashore J, et al: Infant apnea detection after herniorrhaphy. Anesthesiology 75:A1047.1991 (suppl3A) 12. Tetzlaff JE, Annand DW, Pudimat MA, et al: Postoperative apnea in a full-term infant. Anesthesiology 69:426-428, 1988
Discussion Richard Azizkhan (Chapel Hill, NC): From this and other studies, premature infants less than 40 weeks’ postconceptual age (PCA) are clearly at risk for postoperative apnea regardless of whether predisposing risk factors have been identified. Virtually everyone agrees that these patients should be carefully monitored for a minimum period of 12 to 24 hours after surgery. However, there is less agreement in the extent of postoperative monitoring in children between 40 and 60 weeks PCA. Dr Naylor and her colleagues confirmed the previously reported findings of Mestad and coworkers from Kansas City. Those premature infants with risk factors such as chronic lung disease, preexisting apnea, anemia, or theophylline requirements may be at risk for up to 60 weeks PCA for postanesthetic apnea. These patients should be monitored in the hospital. If no risk factors are identified, less stringent postoperative monitoring and shorter observation times for patients greater than 44 weeks PCA may be appropriate. I have a few questions for the authors. Based on your data, do you plan to modify your current criteria for postoperative monitoring in preterm infants? If so, what are your recommendations in this regard? What are you doing to reduce the apnea risks in high-risk prematures ? We have been performing most of our hernia repairs in these high-risk patients under spinal and caudal anesthesia and have been very pleased with our results with a very low incidence of apnea. Do you have any comments regarding this approach for selected patients? Dennis Vane (Burlington, VT): Your rates of postoperative apnea are pretty much the same as others, between 11% and 37%, depending on the patient population. 1 think what’s important to note here is
that it’s neither PCA nor prematurity that increase the incidence of apnea, but rather a combination of the two. Patients less than 36 weeks’ gestation clearly have a higher incidence of apnea than full-term babies, putting them in a higher ASA group. Patients older than 36 weeks’ gestation have a lower incidence, and full-term babies probably even less than they do. The 60-week PCA requirement comes from studies that were done on premature infants and does not appear to apply to full-term infants. In addition, other anesthetic techniques are available that appear to alleviate the risk of postoperative apnea. My question is, have you explored some of these other techniques? Barbara Naylor (response): In regard to your first question, I would say that prior to our reviewing the charts from the institution, we had been very strict about admitting all patients under 60 weeks PCA. Now I think we have become a lot more flexible and basically look at patients at risk as you mentioned. We continue to admit the very young infants. As far as spinal and caudal anesthesia, I found this to be an excellent approach in the young premature infants. It does have its limitations. The success rate is not as high as with general anesthesia, obviously, and some parents may object to this procedure. I think that our data give us confidence that there may not be as great a problem with using general anesthesia, and so perhaps spinal anesthesia is not that much better than general anesthesia as other authors have found. I agree with Dr Vane’s statement that the 60-week cutoff only applied to premature infants. At times we performed surgical procedures on full-term newborns. We considered 40-week PCA full-term infants at risk.
Apnea in Infants
Naylor, Jayant Radhakrishnan, and Desmond McLaughlin Park Ridge, Illinois and Chicago, Illinois
l This is a review of 127 neonates evaluated for postoperative apnea and bradycardia (A&B) after inguinal surgery. The patients could be divided into three groups based on postconceptional age (PCA) at operation. Ten of 29 patients operated on at PCA of 33 to 39 weeks developed episodes of A&B. Preoperative assessment was not reliable in their identification. In the second group of 54 patients at PCA 40 to 44 weeks, 9 developed A&B, whereas in the third group of 44 patients at PCA of 45 to 50 weeks 1 patient developed A&B. In the latter two groups preoperative assessment identified all patients at high risk. We conclude that after PCA of 40 weeks patients at risk for A&B can be identified preoperatively. Patients operated on up to 39 weeks PCA should all be observed in the hospital. Copyright o 1992 by W.B. Saunders Company INDEX WORDS:
Apnea, bradycardia,
postoperative.
S
TEWARD’S observation that expremature infants have a high incidence of postoperative apnea has taken on great importance with the increasing popularity of outpatient surgery. Kurth et al2 reported that preterm infants were at high risk up to 60 weeks postconceptional age (PCA) and recommended monitoring for at least 12 hours postoperatively. We undertook this retrospective review because it was our impression that unexpected episodes of apnea and bradycardia (A&B) were uncommon. MATERIALS AND METHODS At our hospital we monitor all expremature infants up to a PCA of 60 weeks and all full-term infants up to a PCA of 44 weeks for postoperative apnea with continuous pulse oximetry and apnea monitors. This study group consisted of expremature and full-term infants meeting the above admission criteria who underwent inguinal surgery between 1984 and 1991 by one surgeon (J.R.). Patients circumcised under the same anesthetic were included but patients subjected to other major procedures concomitantly were excluded. Charts were reviewed for the following information: gestational age, birth weight, weight at operation, Apgar scores, PCA at operation, associated medical conditions and medications, presence or absence of home apnea monitoring, ASA physical status, anesthesiologist, anesthetic techniques and agents used, operative procedure, and operating time. Presence of postoperative apnea and/or bradycardia in the first 24 hours postoperatively and measures used to terminate these episodes were recorded. Charts of hospitalized patients were also reviewed for evidence of A&B in the 24 hours immediately prior to operation. Apnea was defined as episodes lasting greater than 10 seconds and bradycardia was defined as a heart rate below 80 beats/min. RESULTS
One hundred twenty-seven ASA physical status I to IV patients met the above criteria (107 boys and 20 girls). One hundred two were exprematures, whereas Journal of Pediatric Surgery, Vol27,
No 8 (August),
1992:
pp 955-957
Table 1. Patient Population GrLXlp
PCA bk)
I
33-39
29
25
it
40-44
54
38
III
45-60
44
39
127
102
Tota
I
Total
Premature
25 were full-term infants. Seventy-one patients were admitted for monitoring. A majority of the remaining 56 patients who were hospitalized were premature infants having elective herniorrhaphies prior to discharge. There was no death or serious morbidity in the study. Immediate postoperative reintubation was required in 1 patient. Postoperative A&B was noted in only 19 (15%) patients, all of whom were exprematures. Based on PCA our patients could be divided into three groups (Table 1). Ten of 29 (34.5%) of group I patients developed postoperative A&B (Table 2). Seven of these 10 were considered high risk by preoperative evaluation. Three patients developed postoperative A&B without any preoperative indication of risk factors. Conversely there were 6 patients whose preoperative evaluation rendered them in the high-risk category yet they did not develop postoperative problems. Eight of 54 (14.8%) patients in group II who demonstrated postoperative A&B were all identified as high-risk patients based on one or more of the following: history of A&B, anemia (hemoglobin < 10 g%), chronic respiratory disease, or need for theophylline. All episodes of A&B either resolved spontaneously or responded to stimulation. In addition, there were 7 patients with preoperative indicators who did not develop postoperative A&B. No patient in this group developed postoperative A&B if preoperative indicators were absent. Of 44 patients in group III, the only patient who developed postoperative A&B had chronic renal failure and anemia at the time of operation. He had one short episode that resolved From the Lutheran General Hospital. Pork Ridge. IL, and the University of Chicago, Chicago, IL. Presented at the Jens G. Rosenkranz Resident Competition at the 43rd Annual Meeting of the Surgical Section of the American Academy of Pediatrics, New Orleans, Louisiana, October 26-27, 1991. Address reprint requests to Jayant Radhakrishnan, MD, 2454 E Dempster, Suite 406. Des Plaines, IL 60016. Copyright o I992 by W.B. Saunders Company 0022-3468/92/2708-0004$03,00l0 955
NAYLOR, RADHAKRISHNAN.
956
Table 2. Group
I (PCA
Table 3. Groups II and Ill
33 to 39 Weeks)
Total
29
A&B
10 (34.5%)
Group II (PCA 40 to 44 weeks) Total Postoperative A&B
Postoperative A&B without preoperative 3
indicators
AND McLAUGHLlN
54 8 (14.8%)
Group III (PCA 45 to 60 wk) Total Postoperative A&B
spontaneously. Twelve other patients with preoperative risk factors did not demonstrate any postoperative problems (Table 3). Therefore, correlation was seen between postoperative A&B and gestational age, PCA, associated medical conditions, need for preoperative apnea monitoring and medications, and ASA physical status. There was no correlation with birth weight, weight at surgery, operative procedure, operating time, presence or absence of endotracheal intubation, the type of anesthetic agent used, and the anesthesiologist carrying out the procedure. DISCUSSION
In 1982 Steward’ reported that 6 of 33 expremature infants under 48 weeks PCA had episodes of apnea after herniorrhaphy, whereas no such episodes occurred in 38 full-term infants. Following this report other studies attempted to define the risk of prematurity3” and anemia.6 The use of spinal anesthesia7,8 and caffeine9 have been suggested to reduce this risk. The above-mentioned authors only found evidence of increased apnea in the early postoperative period in expremature infants up to 48 weeks PCA. In 1987 Kurth et al* reported unexpected life-threatening episodes in 6 of 24 infants 49 to 60 weeks PCA causing serious concern that many older expremature infants may be unsuitable for outpatient anesthesia. We believe this discrepancy occurred because they included patients with serious medical problems in their series and also used the same patient on more than 1 occasion. Patients requiring placement of ventriculoperitoneal shunts or central lines, or being subjected to laparotomy can not be compared with those who undergo outpatient surgery. Additionally, the use of the same patient twice falsely increases the incidence of postoperative A&B. To compare our results with theirs we regrouped exprematures by the same age cut-offs and we redefined prolonged A&B as that lasting more than 15 seconds or requiring resuscitative measures such as reintubation or me-
44 1 (2.3%)
NOTE. All patients in groups II and Ill with postoperative A&B had preoperative indicators and were exprematures.
chanical ventilation. In our series prolonged apnea only occurred in infants under 42 weeks PCA. Furthermore, only 3 of 50 expremature infants 43 to 60 weeks PCA and 1 of 24 infants 49 to 60 weeks PCA had any such episodes. Kurth et al2 reported A&B in 13 of 36 in the 43- to 60-week group and 8 of 24 in the 49- to 60-week group, with 10 of 13 episodes being “prolonged.” Using Fisher’s exact test, our results are significantly different (P < .OOl for the 43- to 60week group and P < .03 for the 49- to 60-week group). Our findings are consistent with those of Melone et a1,l0 who, in a similar study, looked at 124 expremature infants up to 59 weeks PCA undergoing inguinal herniorrhaphy and saw brief episodes of A&B in only 4 patients, none of which resulted in serious morbidity. Bell et al” cautioned that a few apneic events are missed when infants are monitored using real-time apnea monitoring and intermittent nursing observation but the significance of these short apneic events is not clear. Finally, neither our study nor those of otherG3-11 demonstrated postoperative A&B in fullterm patients as reported by Kurth et al* and Tetzlaff et al.‘* The latter authors presented a case report of significant postoperative apnea in a full-term baby at 42 weeks PCA after two separate operations for congenital cataracts. Therefore, we believe that the following conclusions are warranted: (1) there is an increased incidence of A&B in all infants under 39 weeks PCA; hence, all these infants should be monitored in hospital for 24 hours postoperatively; and (2) expremature infants over 39 weeks PCA are at a higher risk of postoperative A&B only if they have preoperative indicators such as a history of A&B, hemoglobin below 10 g%, chronic respiratory disease, or are taking theophylline at the time of operation.
REFERENCES 1. Steward DJ: Preterm infants are more prone to complications following minor surgery than are term infants. Anesthesiology 56:304-306,1982 2. Kurth CD, Spitzer AR, Broennle AM, et al: Postoperative apnea in preterm infants. Anesthesiology 66:483-488, 1987
3. Liu LMP, Cote CJ, Goudsouzian NG, et al: Life-threatening apnea in infants recovering from anesthesia. Anesthesiology 59:506510,1983 4. Welborn LG, Ramirez N, Oh TH, et al: Postanesthetic apnea and periodic breathing in infants. Anesthesiology 65:658-661,1986
POSTOPERATIVE
APNEA IN INFANTS
957
5. Tashiro C, Matsui Y, Nakano S, et al: Respiratory outcome in extremely premature infants following ketamine anaesthesia. Can J Anaesth 38:287-291,199l 6. Welborn LG, Hannallah RS, Luban NLC, et al: Anemia and postoperative apnea in former preterm infants. Anesthesiology 74:1003-1006.1991 7. Welborn LG, Rice LJ, Hannallah RS, et al: Postoperative apnea in former preterm infants: Prospective comparison of spinal and general anesthesia. Anesthesiology 72:838-842,199O 8. Webster AC. McKishnie JD. Kenvon CF. et al: Suinal , anesthesia for inguinal hernia repair in high-risk neonates. Can J Anaesth 38:281-286, 1991
9. Welborn LG, Hannallah RS, Fink R, et al: High-dose caffeine suppresses postoperative apnea in former preterm infants. Anesthesiology 71:347-349, 1989 10. Melone JH, Schwartz MZ, Tyson KRT: Outpatient inguinal herniorrhaphy in premature infants: Is it safe? J Pediatr Surg 27:203-208,1992 11. Bell C, Dubose R, Seashore J, et al: Infant apnea detection after herniorrhaphy. Anesthesiology 75:A1047.1991 (suppl3A) 12. Tetzlaff JE, Annand DW, Pudimat MA, et al: Postoperative apnea in a full-term infant. Anesthesiology 69:426-428, 1988
Discussion Richard Azizkhan (Chapel Hill, NC): From this and other studies, premature infants less than 40 weeks’ postconceptual age (PCA) are clearly at risk for postoperative apnea regardless of whether predisposing risk factors have been identified. Virtually everyone agrees that these patients should be carefully monitored for a minimum period of 12 to 24 hours after surgery. However, there is less agreement in the extent of postoperative monitoring in children between 40 and 60 weeks PCA. Dr Naylor and her colleagues confirmed the previously reported findings of Mestad and coworkers from Kansas City. Those premature infants with risk factors such as chronic lung disease, preexisting apnea, anemia, or theophylline requirements may be at risk for up to 60 weeks PCA for postanesthetic apnea. These patients should be monitored in the hospital. If no risk factors are identified, less stringent postoperative monitoring and shorter observation times for patients greater than 44 weeks PCA may be appropriate. I have a few questions for the authors. Based on your data, do you plan to modify your current criteria for postoperative monitoring in preterm infants? If so, what are your recommendations in this regard? What are you doing to reduce the apnea risks in high-risk prematures ? We have been performing most of our hernia repairs in these high-risk patients under spinal and caudal anesthesia and have been very pleased with our results with a very low incidence of apnea. Do you have any comments regarding this approach for selected patients? Dennis Vane (Burlington, VT): Your rates of postoperative apnea are pretty much the same as others, between 11% and 37%, depending on the patient population. 1 think what’s important to note here is
that it’s neither PCA nor prematurity that increase the incidence of apnea, but rather a combination of the two. Patients less than 36 weeks’ gestation clearly have a higher incidence of apnea than full-term babies, putting them in a higher ASA group. Patients older than 36 weeks’ gestation have a lower incidence, and full-term babies probably even less than they do. The 60-week PCA requirement comes from studies that were done on premature infants and does not appear to apply to full-term infants. In addition, other anesthetic techniques are available that appear to alleviate the risk of postoperative apnea. My question is, have you explored some of these other techniques? Barbara Naylor (response): In regard to your first question, I would say that prior to our reviewing the charts from the institution, we had been very strict about admitting all patients under 60 weeks PCA. Now I think we have become a lot more flexible and basically look at patients at risk as you mentioned. We continue to admit the very young infants. As far as spinal and caudal anesthesia, I found this to be an excellent approach in the young premature infants. It does have its limitations. The success rate is not as high as with general anesthesia, obviously, and some parents may object to this procedure. I think that our data give us confidence that there may not be as great a problem with using general anesthesia, and so perhaps spinal anesthesia is not that much better than general anesthesia as other authors have found. I agree with Dr Vane’s statement that the 60-week cutoff only applied to premature infants. At times we performed surgical procedures on full-term newborns. We considered 40-week PCA full-term infants at risk.
