Continuous oesophageal aortic blood flow echo-Doppler measurement during general anaesthesia in infants

Clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock: 2007 update from the American College of Critical Care Medicine

BACKGROUND

The Institute of Medicine calls for the use of clinical guidelines and practice parameters to promote "best practices" and to improve patient outcomes.

OBJECTIVE

2007 update of the 2002 American College of Critical Care Medicine Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock.

PARTICIPANTS

Society of Critical Care Medicine members with special interest in neonatal and pediatric septic shock were identified from general solicitation at the Society of Critical Care Medicine Educational and Scientific Symposia (2001-2006).

METHODS

The Pubmed/MEDLINE literature database (1966-2006) was searched using the keywords and phrases: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation (ECMO), and American College of Critical Care Medicine guidelines. Best practice centers that reported best outcomes were identified and their practices examined as models of care. Using a modified Delphi method, 30 experts graded new literature. Over 30 additional experts then reviewed the updated recommendations. The document was subsequently modified until there was greater than 90% expert consensus.

RESULTS

The 2002 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and AHA sanctioned recommendations. Centers that implemented the 2002 guidelines reported best practice outcomes (hospital mortality 1%-3% in previously healthy, and 7%-10% in chronically ill children). Early use of 2002 guidelines was associated with improved outcome in the community hospital emergency department (number needed to treat = 3.3) and tertiary pediatric intensive care setting (number needed to treat = 3.6); every hour that went by without guideline adherence was associated with a 1.4-fold increased mortality risk. The updated 2007 guidelines continue to recognize an increased likelihood that children with septic shock, compared with adults, require 1) proportionally larger quantities of fluid, 2) inotrope and vasodilator therapies, 3) hydrocortisone for absolute adrenal insufficiency, and 4) ECMO for refractory shock. The major new recommendation in the 2007 update is earlier use of inotrope support through peripheral access until central access is attained.

CONCLUSION

The 2007 update continues to emphasize early use of age-specific therapies to attain time-sensitive goals, specifically recommending 1) first hour fluid resuscitation and inotrope therapy directed to goals of threshold heart rates, normal blood pressure, and capillary refill 70% and cardiac index 3.3-6.0 L/min/m.

The transesophageal Doppler and hemodynamic effects of epidural anesthesia in infants anesthetized with sevoflurane and sufentanil

BACKGROUND

It is thought that pediatric epidural anesthesia (EA) provides hemodynamic stability in children. However, when compared with information relating to adults, little is known about the hemodynamic effects of epidural EA on cardiac output (CO) in infants.

METHODS

Using transesophageal Doppler to monitor CO, we prospectively studied 14 infants <10 kg who were scheduled for abdominal surgery. During sevoflurane general anesthesia, CO transesophageal Doppler monitoring was performed before and after lumbar EA with 0.75 mL/kg of 0.25% bupivacaine and 1:200,000 adrenaline. CO, arterial blood pressure, and heart rate were measured before and 5, 15, and 20 min after performance of EA.

RESULTS

In patients anesthetized with sevoflurane and sufentanil, EA resulted in an increase in stroke volume by 29% (P < 0.0001) and a decrease in heart rate by 13% (P < 0.0001). EA also induced a significant decrease in systolic, diastolic, mean arterial blood pressure, and systemic vascular resistance by 11%, 18%, 15%, and 25%, respectively. Conversely, CO remained unchanged.

CONCLUSIONS

The increase in stroke volume observed is probably explained by optimization of afterload because of the sympathetic blockade induced by EA. These results confirm that EA provides hemodynamic stability in infants weighing <10 kg and supports the use of EA in this pediatric population.

Comparison of invasive and less-invasive techniques of cardiac output measurement under different haemodynamic conditions in a pig model

BACKGROUND AND OBJECTIVE

Despite the introduction of various less-invasive concepts of cardiac output measurement, pulmonary arterial thermodilution is still the most common measurement technique.

METHODS

This prospective controlled study was designed to compare different methods of cardiac output measurement simultaneously. Pulmonary arterial thermodilution, transpulmonary thermodilution (PiCCO), trans-oesophageal echo-Doppler probe (HemoSonic) and partial carbon dioxide rebreathing technique (NICO monitor) were evaluated against a peri-aortic transit-time flow-probe as reference method in a clinically relevant animal model. After approval from the Local Ethics Committee on Animal Research, the investigations were conducted in nine anesthetized domestic pigs. Systemic haemodynamics were modulated systematically by the application of catecholamines, caval occlusion and exsanguination. Statistical analysis was performed with Bland-Altman and linear regression.

RESULTS

A total of 366 paired cardiac output measurements were carried out at a reference cardiac output between 0.5 and 7 L min(-1). The correlation coefficients for pulmonary arterial and transpulmonary thermodilution against reference were 0.93 and 0.95, for trans-oesophageal Doppler and partial rebreathing technique 0.84 and 0.77. Pulmonary arterial thermodilution and transpulmonary thermodilution showed comparable bias and limits of agreement. Where HemoSonic showed an overestimation of cardiac output at a higher precision, NICO overestimated low and underestimated higher cardiac output values.

CONCLUSIONS

Our data suggest that pulmonary arterial thermodilution and PiCCO may be interchangeably used for cardiac output measurement even under acute haemodynamic changes. The method described by Bland and Altman demonstrated an overestimation of cardiac output for both thermodilution methods. HemoSonic and NICO offer non-invasive alternatives and complementary monitoring tools in numerous clinical situations. Trend monitoring and haemodynamic optimizing can be applied sufficiently, when absolute measures are judged critically in a clinical context. The use of the NICO system seems to be limited during acute circulatory changes.

Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock

BACKGROUND

The Institute of Medicine has called for the development of clinical guidelines and practice parameters to develop "best practice" and potentially improve patient outcome.

OBJECTIVE

To provide American College of Critical Care Medicine clinical guidelines for hemodynamic support of neonates and children with septic shock.

SETTING

Individual members of the Society of Critical Care Medicine with special interest in neonatal and pediatric septic shock were identified from literature review and general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (1998-2001).

METHODS

The MEDLINE literature database was searched with the following age-specific keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, and extracorporeal membrane oxygenation. More than 30 experts graded literature and drafted specific recommendations by using a modified Delphi method. More than 30 more experts then reviewed the compiled recommendations. The task-force chairman modified the document until <10% of experts disagreed with the recommendations.

RESULTS

Only four randomized controlled trials in children with septic shock could be identified. None of these randomized trials led to a change in practice. Clinical practice has been based, for the most part, on physiologic experiments, case series, and cohort studies. Despite relatively low American College of Critical Care Medicine-graded evidence in the pediatric literature, outcomes in children have improved from 97% mortality in the 1960s to 60% in the 1980s and 9% mortality in 1999. U.S. hospital survival was three-fold better in children compared with adults (9% vs. 27% mortality) in 1999. Shock pathophysiology and response to therapies is age specific. For example, cardiac failure is a predominant cause of death in neonates and children, but vascular failure is a predominant cause of death in adults. Inotropes, vasodilators (children), inhaled nitric oxide (neonates), and extracorporeal membrane oxygenation can be more important contributors to survival in the pediatric populations, whereas vasopressors can be more important contributors to adult survival.

CONCLUSION

American College of Critical Care Medicine adult guidelines for hemodynamic support of septic shock have little application to the management of pediatric or neonatal septic shock. Studies are required to determine whether American College of Critical Care Medicine guidelines for hemodynamic support of pediatric and neonatal septic shock will be implemented and associated with improved outcome.

The hemodynamic effects of pediatric caudal anesthesia assessed by esophageal Doppler

Pediatric caudal anesthesia is an effective method with an infrequent complication rate. However, little is known about its cardiovascular consequences. Transesophageal Doppler, a noninvasive method, provides the opportunity for a reappraisal of the hemodynamic effects of this technique. After parental informed consent, we studied 10 children aged 2 mo to 5 yr who were scheduled for lower abdominal surgery. General anesthesia was induced using sevoflurane and was followed by the insertion of a transesophageal Doppler probe. Caudal anesthesia was performed using 1 mL/kg of 0.25% bupivacaine with 1/200,000 epinephrine. Hemodynamic variables were collected before and after caudal anesthesia. No complications arose during insertion of the probe. The mean time between the two sets of measurements was 15 min. Heart rate, systolic, diastolic, and mean arterial blood pressures were not modified by caudal anesthesia. Descending aortic blood flow increased significantly from 1.14 to 1.92 L/min. (P = 0.0002). Aortic ejection volume increased from 8.5 to 14.5 mL (P = 0.0002). Aortic vascular resistances decreased from 6279 to 3901 dynes. s(-1) x m(-5) (P = 0.005). Caudal anesthesia did not affect heart rate and mean arterial blood pressure but induced a significant increase in descending aortic blood flow.

IMPLICATIONS

Although pediatric caudal anesthesia does not alter heart rate nor arterial blood pressure, significant changes occur in regional blood flow distribution. Descending aortic blood flow increases significantly after caudal anesthesia, whereas lower body vascular resistances decrease.

Accuracy and limitations of continuous oesophageal aortic blood flow measurement during general anaesthesia for children: comparison with transcutaneous echography-Doppler

BACKGROUND

Because it is noninvasive and easy to use, oesophageal Doppler ultrasonography appears to be a worthwhile alternative for continuous assessment of cardiac output measurement during anaesthesia. A new oesophageal Doppler-echography device (Dynemo 3000, Sometec, Paris, France) can simultaneously determine aortic diameter and aortic blood flow at the same anatomical level (DEeso). The purpose of this study was to assess the accuracy and the potential limitations of this device during general anaesthesia among 20 children, using transcutaneous Doppler-echocardiography for comparison (DEtra).

METHODS

The reproducibility of paired measurements of mean aortic blood flow velocity (MAFV), aortic diameter (ØAo) and aortic blood flow (ABF) was analysed with both methods. Second, haemodynamic values were measured simultaneously in a blinded manner by both methods before and after surgery.

RESULTS

The percent change (%Delta) in MAFV and ABF was calculated with both methods for each child. The age and weight of children included in this study was 8.3 +/- 2.5 years and 27 +/- 8 kg, respectively. Intraoperator reproducibility of MAFVtra, ABFtra, MAFVeso and ABFeso, was 5.0 +/- 4.1%, 7.0 +/- 5.6%, 20.1 +/- 17.5% and 22.0 +/- 16.6%, respectively. ABFtra was significantly linked to ABFeso (R=0.55, P < 0.01). Bias +/- SD of ABF measurements between both methods was 2.2 +/- 1.1 l. min-1. %DeltaABFtra was significantly linked to %DeltaABFeso (R=0.62, P < 0.01). The bias +/- SD inherent to %DeltaABF measurements with both methods was -0.02 +/- 18%.

CONCLUSION

These results suggest that this new oesophageal Doppler method is unsuitable to measure accurately absolute CO values and relative CO changes in children during anaesthesia.

Non-invasive aortic blood flow measurement

Invasive monitoring is rarely used for children undergoing routine anaesthesia, whereas usual non-invasive haemodynamic measurements such as heart rate and blood pressure monitoring are unable to detect cardiovascular changes rapidly and precisely. In contrast, oesophageal aortic blood flow echo-Doppler is an easy, non-invasive and accurate method to monitor cardiac performance properly and continuously. Therefore, it could represent a useful addition to peri-anaesthetic monitoring techniques, particularly in infants and small children.

Continuous noninvasive measurement of aortic blood flow in critically ill patients with a new esophageal echo-Doppler system

PURPOSE

Determination of aortic blood flow (ABF) using esophageal Doppler has been proposed as a low invasive hemodynamic monitoring method. The esophageal echo-Doppler Dynemo 3000 (Sometec Inc., Paris, France) system, recently available on the market, is an original device measuring simultaneously, and at the same anatomic level, aortic diameter, and blood flow velocity. Until now, this material has been used exclusively for peroperative monitoring. The objectives of the study were to assess the feasibility and reliability of use for continuous measurements of ABF in hemodynamically compromised intensive care unit patients; and to compare ABF values and its change induced by preload manipulation with the cardiac output (CO) values measured simultaneously by the standard thermodilution method.

MATERIALS AND METHODS

Sixty simultaneous measurements of ABF and CO were performed in 22 intensive care unit patients. In 16 hypovolemic patients, Doppler and thermodilution measurements were repeated after fluid replacement.

RESULTS

Applicability of the method was 84.6% (failure of the echo-Doppler method in 4 of 26 eligible patients). Coefficient of variation of echo-Doppler-derived ABF was 3.25 +/- 2.26%. Interobserver variability was 3.3 +/- 1.6%. Close linear relationship was found between ABF and CO (r = 0.92). Average ABF/CO ratio was 73 +/- 10%, but significant variation was observed after fluid replacement.

CONCLUSIONS

The echo-Doppler Dynemo 3000 system allows reliable continuous measurements of ABF in intensive care unit patients, both easily and safely.

Myocardial effects of isoflurane in healthy infants and small children. Assessment by continuous oesophageal aortic blood flow echo-Doppler

BACKGROUND

In paediatric healthy patients and in real peroperative conditions, the cardiovascular effects of isoflurane have been poorly described.

METHODS

We have evaluated the myocardial effects of 1% end-expired concentration (EEC) of isoflurane in 25 healthy infants or small children undergoing superficial surgical therapy for small burns with a continuous aortic blood flow echo-Doppler device. Aortic blood flow (ABF) was measured with a small oesophageal probe specially designed for infants. The aortic flowmeter was connected with satellite devices to visualize the haemodynamic profile variations during the isoflurane inhalation period.

RESULTS

Isoflurane significantly decreased ABF and increased pre-ejection period/left ventricular ejection time (PEP/LVET), when compared with control values previously recorded 5 min after induction with halothane-fentanyl and atracurium (respectively, 80 +/- 7%, mean +/- SD; P < 0.001 and 111 +/- 11%; P = 0.017, 5 min after EEC of isoflurane reached 1%, then respectively, 75 +/- 12%; P < 0.001 and 119 +/- 16%; P < 0.001, at the end of the isoflurane inhalation period). These variations reversed to a great extent when isoflurane was switched off (97 +/- 17% for ABF; P = 0.08 and 105 +/- 12% for PEP/LVET; P = 0.75). Among the usual parameters, 1% EEC of isoflurane caused no significant changes in heart rate, moderately decreased mean arterial pressure (successively, 88 +/- 12%; P = 0.045 and 87 +/- 19%; P = 0.049), but belatedly decreased end-tidal CO2 pressure (87 +/- 11% at the end of the inhalation period (P < 0.001) which persisted 5 min after isoflurane was turned off (90 +/- 11%; P < 0.001)).

CONCLUSIONS

These findings suggest that isoflurane can transiently depress cardiac function in healthy infants.

The hemodynamic effects of pneumoperitoneum during laparoscopic surgery in healthy infants: assessment by continuous esophageal aortic blood flow echo-Doppler

Cardiovascular changes due to pneumoperitoneum during laparoscopic surgery are established in adult patients, but not known in infants. We investigated the hemodynamic effects of laparoscopy during general anesthesia in 12 ASA physical status I infants by using noninvasive continuous esophageal aortic blood flow (ABF) echo-Doppler monitoring. During the laparoscopic procedure, intraabdominal pressure was maintained automatically at 10 mm Hg by a CO2 insufflator, and minute ventilation was adjusted to avoid hypercapnia. Hemodynamic changes were continuously recorded on soft magnetic support and assessed at three time intervals: t0 (after the initiation of anesthesia), t1 (5 min after peritoneal insufflation), and t2 (5 min after exsufflation). The induction of pneumoperitoneum resulted in a significant decrease in ABF and stroke volume, and in a significant increase in systemic vascular resistance, compared with control values: 67% +/- 9% (P < 0.001), 68% +/- 10% (P < 0.001), and 162% +/- 34% (P < 0.001), respectively. These changes were completely reversed after peritoneal exsufflation. Pneumoperitoneum caused no significant changes in mean arterial pressure or in end-tidal CO2 pressure. These findings demonstrate that laparoscopy is associated with hemodynamic changes without clinically deleterious consequences in healthy infants during a short duration of pneumoperitoneum.

IMPLICATIONS

The peritoneal insufflation achieved during laparoscopic surgery is associated with cardiovascular impairments (decrease in cardiac performance and increase in vascular resistance). We found that these changes had no clinically deleterious effects in healthy infants.