The ontogeny of cerebrovascular pressure autoregulation in premature infants.

OBJECTIVE: To quantify cerebrovascular autoregulation as a function of gestational age (GA) and across the phases of the cardiac cycle. STUDY DESIGN: The present study is a hypothesis-generating re-analysis of previously published data. Premature infants (n=179) with a GA range of 23 to 33 weeks were monitored with umbilical artery catheters and transcranial Doppler insonation of the middle cerebral artery for 1-h sessions over the first week of life. Autoregulation was quantified by three methods, as a moving correlation coefficient between: (1) systolic arterial blood pressure (ABP) and systolic cerebral blood flow (CBF) velocity (Sx); (2) mean ABP and mean CBF velocity (Mx); and (3) diastolic ABP and diastolic CBF velocity (Dx). Comparisons of individual and cohort cerebrovascular pressure autoregulation were made across GA for each aspect of the cardiac cycle. RESULTS: Systolic, mean and diastolic ABP increased with GA (r=0.3, 0.4 and 0.4; P<0.0001). Systolic CBF velocity was pressure-passive in infants with the lowest GA, and Sx decreased with advancing GA (r=-0.3; P<0.001), indicating increased capacity for cerebral autoregulation during systole during development. By contrast, Dx was elevated, indicating dysautoregulation, in all subjects and showed minimal change with advancing GA (r=-0.06; P=0.05). Multivariate analysis confirmed that both GA (P<0.001) and 'effective cerebral perfusion pressure' (ABP minus critical closing pressure (CrCP); P<0.01) were associated with Sx. CONCLUSION: Premature infants have low and usually pressure-passive diastolic CBF velocity. By contrast, the regulation of systolic CBF velocity by pressure autoregulation developed in this cohort between 23 and 33 weeks GA. Elevated effective cerebral perfusion pressure derived from the CrCP was associated with dysautoregulation.

Mesenteric oxyhemoglobin desaturation improves with patent ductus arteriosus ligation.

Near-infrared spectroscopy was used to monitor cerebral and mesenteric regional oximetry in a preterm neonate undergoing surgical ligation of a patent ductus arteriosus. This patient initially demonstrated severe mesenteric oxyhemoglobin desaturation, which improved immediately following ductal ligation.

Anesthetic and perioperative outcome of teenagers and adults with congenital heart disease.

OBJECTIVE: To compare the perioperative outcome of patients >or=13 years old undergoing surgery for congenital heart disease in a children's hospital by a dedicated congenital heart surgery and anesthesia team with procedure-matched younger control patients. DESIGN: Retrospective medical record review study. From October 1997 to July 2000, medical records of all patients >12 years old requiring cardiopulmonary bypass were reviewed. A control group of patients

Perioperative care of the adult with congenital heart disease in a free-standing tertiary pediatric facility.

Adult patients with congenital heart disease are presenting more frequently for cardiac surgery. Frequently, pediatric congenital heart surgeons perform these procedures at pediatric hospitals. Between July 1995 and June 2000, a retrospective review of adult patients (> or = 18 years old) who had undergone cardiothoracic operations was performed. A total of 112 operations were performed and divided into two groups--81 cardiac operations in 79 patients and 31 noncardiac operations in 23 patients. One patient had a cardiac and noncardiac operation performed. The overall early operative mortality was 6% (6/101). There were 3 late deaths. New-onset cardiac arrhythmias requiring treatment were diagnosed after 5/81 (6%) cardiac operations. Six of 79 (7%) patients were diagnosed with postoperative clinical depression. An acceptable mortality can be achieved when adult patients undergo cardiothoracic operations at a pediatric facility. New-onset arrhythmias necessitating treatment are relatively common, and postoperative clinical depression should be anticipated.

The optimal length of insertion of central venous catheters for pediatric patients.

UNLABELLED: Incorrect positioning of central venous catheters (CVC) in infants and children may lead to serious complications such as perforation of the heart or great vessels. CVC position is not usually assessed until the first postoperative chest radiograph, potentially leaving malposition undetected for several hours. We studied a series of 452 right internal jugular and subclavian catheter placements in infants and children undergoing surgery for congenital heart disease, and measured the distance from the skin insertion site to the radiographic junction of the superior vena cava and right atrium (RA). Based on these data, the following formulae predict that a CVC will be positioned above the RA 97% of the time: correct length of insertion (cm) = (height in cm/10) - 1 for patients < or =100 cm in height, and (height in cm/10) - 2 for patients >100 cm in height. Weight-based recommendations were also developed which predict placement of CVC above the RA 98% of the time. IMPLICATIONS: This study assessed central venous catheter placement in 452 infants and children undergoing cardiac surgery. Simple, clinically useful guidelines based on height and weight were developed to prevent malposition of these catheters, which may cause serious complications such as perforation of the heart or great vessels.

Cardiovascular effects of sevoflurane, isoflurane, halothane, and fentanyl-midazolam in children with congenital heart disease: an echocardiographic study of myocardial contractility and hemodynamics.

BACKGROUND: The cardiovascular effects of halogenated anesthetic agents in children with normal hearts have been studied, but data in children with cardiac disease are limited. This study compared the effects of halothane, isoflurane, sevoflurane, and fentanyl-midazolam on systemic and pulmonary hemodynamics and myocardial contractility in patients with congenital heart disease. METHODS: Fifty-four patients younger than age 14 scheduled to undergo congenital heart surgery were randomized to receive halothane, sevoflurane, isoflurane, or fentanyl-midazolam. Cardiovascular and echocardiographic data were recorded at baseline and at randomly ordered 1 and 1.5 minimum alveolar concentrations, or predicted equivalent fentanyl-midazolam plasma concentrations. The shortening fraction and ejection fraction (using the modified Simpson rule) were calculated. Cardiac index was assessed by the velocity-time integral method. RESULTS: Halothane caused a significant decrease in mean arterial pressure, ejection fraction, and cardiac index, preserving only heart rate at baseline levels. Fentanyl-midazolam in combination caused a significant decrease in cardiac index secondary to a decrease in heart rate; contractility was maintained. Sevoflurane maintained cardiac index and heart rate and had less profound hypotensive and negative inotropic effects than halothane. Isoflurane preserved both cardiac index and ejection fraction, had less suppression of mean arterial pressure than halothane, and increased heart rate. CONCLUSIONS: Isoflurane and sevoflurane preserved cardiac index, and isoflurane and fentanyl-midazolam preserved myocardial contractility at baseline levels in this group of patients with congenital heart disease. Halothane depressed cardiac index and myocardial contractility.

Volume ventilation of infants with congenital heart disease: a comparison of Dräger, NAD 6000 and Siemens, Servo 900C ventilators.

UNLABELLED: We compared the ventilation and pulmonary mechanics produced by a new anesthesia ventilator (NAD 6000) using a circle system with that produced by a critical care ventilator (Servo 900C) using a nonrebreathing circuit in infants with congenital heart disease. Twenty patients, aged 1 day to 7 mo, weighing 2.1 to 4.6 kg, were studied. The NAD 6000 had improved alveolar ventilation: PaCO(2) 43 +/- 8 vs 47 +/- 5 mm Hg (P = 0.005), end-tidal CO(2) 34 +/- 7 vs 37 +/- 5 mm Hg (P = 0.042); larger inspired tidal volumes 12.9 +/- 2.8 vs 11.3 +/- 2.2 mL/kg (P < 0.001), but with higher mean airway pressures 9.7 +/- 1.6 vs 8.6 +/- 1.3 cm H(2)O (P < 0.001). These differences in ventilation and airway pressures were not clinically significant. Although there were differences in observed ventilatory variables, both machines provided adequate ventilation when set in the volume control mode. IMPLICATIONS: We compared two ventilators for use in infants. Twenty infants undergoing surgery for congenital heart defects were randomized to receive ventilation first with one ventilator, then with the other. Although there were differences in observed ventilatory variables, both machines provided adequate ventilation when set in the volume control mode.

Pressure control ventilation: three anesthesia ventilators compared using an infant lung model.

UNLABELLED: We compared three ventilators-Servo 900C (Siemens Medical Systems, Danvers, MA), Aestiva 3000 (Datex-Ohmeda, Madison, WI), and NAD 6000 (North American Dräger, Telford, PA)-set to deliver pressure control ventilation using an infant test lung model. Ventilator settings were selected to test "near-maximum" settings that would be used for a neonatal patient (peak inspiratory pressure [PIP] 30 cm H(2)O) or older child (PIP 60 cm H(2)O). When adjusted for set inspiratory pressure and compliance, the average tidal volume (V(t)) produced by the NAD 6000 was 5.8 mL less than the Servo 900C (P: = 0. 103), and the average V(t) produced by the Aestiva 3000 was 18.9 mL less than the Servo 900C (P: < 0.001). The Servo 900C generated increased peak pressures, tending to overshoot the set maximum inflating pressures, especially during rapid respiratory rates with decreased inspiratory times. The Aestiva 3000 did not achieve the set PIP during testing conditions of decreased inspiratory times, and the NAD 6000 was not greatly affected by changes in inspiratory time. All three ventilators measured expiratory V(t) to be larger than the actual V(t) delivered to the lung; however, the NAD 6000 was more accurate. IMPLICATIONS: There are differences in performance of ventilators when set to deliver pressure control ventilation to an infant test lung model.

The effects of transesophageal echocardiography on hemodynamic variables in small infants undergoing cardiac surgery.

OBJECTIVE: To assess the effects of transesophageal echocardiography (TEE) on hemodynamic variables during cardiac surgery in small infants. DESIGN: A prospective clinical study. SETTING: A medical college-affiliated tertiary care children's hospital. PARTICIPANTS: Twenty-three infants weighing 2 to 5 kg undergoing cardiac surgery. INTERVENTIONS: Baseline heart rate, arterial pressure, and central venous pressure were recorded. A pediatric TEE probe was inserted, and the hemodynamic variables were again recorded. Postoperatively the hemodynamic measurements were measured again before and after probe removal, with the addition of left atrial pressure and pulmonary artery pressure when available. Hemodynamic parameters were carefully observed during all phases of the TEE examinations for any changes attributable to probe manipulation. MEASUREMENTS AND MAIN RESULTS: No statistically significant changes occurred in this group of patients during TEE. No clinically significant changes in any individual patient occurred during the measurement or during manipulation of the TEE probe for the complete examination. CONCLUSION: Although hemodynamic compromise can occur in small infants, this study suggests that it is infrequent. Fear of hemodynamic compromise should not prevent use of intraoperative TEE in small infants when otherwise indicated.

Comparison of NAD 6000 and servo 900C ventilators in an infant lung model.

UNLABELLED: We compared the ability of the NAD 6000 (North American Dräger, Telford, PA) and the Servo 900C (Siemens-Elema AB, Solna, Sweden) anesthesia ventilators to maintain precise delivery of small tidal volumes (V(t)) and positive end-expiratory pressure using an infant test lung model. A variety of ventilator and lung model settings were selected to test clinical conditions simulating normal and extremely compromised lung function. Differences in ventilator output were analyzed by using an independent t-test with P <0.05 considered significant. With the ventilators set to deliver a V(t) of 30 mL, the actual delivered V(t) was significantly better for the NAD 6000 (25 +/- 2 mL) compared with the Servo 900C (18 +/- 3 mL), P <0.001. When the ventilators were set to deliver 100 mL V(t), their delivered V(t) were not significantly different, NAD 6000 (66 +/- 19 mL) and Servo 900C (60 +/- 12 mL), P = 0.09. The exhaled V(t) read by the anesthesia machines was significantly closer to the delivered V(t) for the NAD 6000 (11 +/- 9 mL) compared with the Servo 900C (37 +/- 11 mL), P < 0.001. Both ventilators maintained the end expiratory pressure delivered to the test lung within 2 cm H(2)O of the set positive end-expiratory pressure on average. As the conditions changed requiring the ventilator to develop a higher peak inflating pressure, both ventilators showed a decrease in V(t) delivered, which was proportionate to the tubing compression volume loss. IMPLICATIONS: The NAD 6000 (North American Dräger, Telford, PA) and Servo 900C (Siemens-Elema AB, Solna, Sweden) are able to precisely deliver small Tidal Volumes. They both decreased in performance when tested under extreme conditions. Earlier studies of traditional anesthesia ventilators suggest that the NAD 6000 and Servo 900C are superior pediatric ventilators.

The effect of transesophageal echocardiography on ventilation in small infants undergoing cardiac surgery.

UNLABELLED: Transesophageal echocardiography (TEE) is frequently used during congenital cardiac surgery. Complications are infrequent, but interference with ventilation has been reported, especially in small infants. Ventilation variables were measured prospectively in 22 infants, 2-5 kg, undergoing heart surgery with TEE. Measurements were made preoperatively before and after TEE probe insertion and postoperatively before and after TEE probe removal. The variables measured included arterial blood gases, expired tidal volume, peak inspiratory pressure, positive end-expiratory pressure, minute ventilation, airway resistance, dynamic compliance, and peak inspiratory and expiratory flow rates. No significant change in any ventilatory variable at either time period was noted in the infants. IMPLICATIONS: Ventilatory compromise is infrequent in small infants undergoing transesophageal echocardiography (TEE) examination. Careful ventilatory monitoring rapidly detects changes in ventilation during TEE examination. Small infants who benefit from TEE during heart surgery should not be excluded from receiving a TEE examination because of concern of ventilatory compromise.

A controlled study of transesophageal echocardiography to guide central venous catheter placement in congenital heart surgery patients.

UNLABELLED: Transesophageal echocardiography (TEE) and central venous catheter (CVC) placement are often used during congenital cardiac surgery. Complications of CVC placement include cardiac perforation, inadvertent arterial placement, and erroneous hemodynamic data from unrecognized malposition. In this study, we used a prospective, randomized, controlled design to evaluate the use of TEE to guide depth of insertion and confirm superior vena cava cannulation, and to improve the percentage of correctly placed CVCs and reduce complications of CVC placement. One hundred forty-five patients were studied. Eighty patients were randomized to have subclavian vein insertion, 64 to have internal jugular insertion, and 1 to have external jugular insertion of CVC. TEE-guided CVC placement resulted in 100% correct placement when assessed by preoperative TEE, versus 86% in the control group (72 of 72 vs. 63 of 73; P = 0.01). There was no difference in correct placement between the two groups when assessed by postoperative chest radiograph (81.9% TEE versus 75.3% control; P = not significant). One significant complication, a superior vena cava perforation, occurred in the control group. Time to placement was 9.6 min in the TEE group versus 8.0 min in the control group (P = 0.015). IMPLICATIONS: Transesophageal echocardiography can be used to guide central venous catheter placement in congenital heart surgery. Central venous catheters that seem to be located high in the right atrium by chest radiograph in these patients are often actually in the superior vena cava and pose little risk of cardiac perforation.

Anaesthetic and surgical airway management during tracheo-oesophageal fistula repair.

A retrospective review of 61 cases of airway management for newborn tracheo-oesophageal fistula (TOF)/oesophageal atresia repair is presented. Standard management included induction of general anaesthesia and muscle relaxation before tracheal intubation, rigid bronchoscopy, careful placement of the tracheal tube below the TOF if possible, and occlusion of the fistula with a Fogarty embolectomy catheter in certain high risk cases. Gastrostomy was not routinely performed. Ventilation proceeded without difficulty in 48 cases. Ventilation difficulties were encountered in 13 cases. Eight of the 13 cases had large TOF, and four had other causes of difficult ventilation not related to the fistula. No patient with a small TOF had ventilation problems because of the TOF. Three patients had a large TOF successfully occluded with an embolectomy catheter through the bronchoscope. There were no complications ascribed to this technique. An algorithm is suggested for anaesthetic-surgical airway management in these cases.