Simultaneous monitoring of noninvasive hemodynamic profile and capnography for tissue perfusion evaluation

Esophageal Doppler and thermodilution are not interchangeable for determination of cardiac output

PURPOSE

This study compares thermodilution cardiac output (TD-CO) and esophageal Doppler cardiac output (ED-CO) during periods of hemodynamic stability and after heart stabilization during off-pump coronary artery bypass (OPCAB) surgery.

METHODS

After Institutional Review Board approval, 58 patients undergoing OPCAB had simultaneous comparison of TD-CO and ED-CO at three time periods. Measurements were recorded, in a blinded manner, after probe insertion (T0), immediately before and after (T1,T2) heart displacement and before starting any pharmacological treatment (if needed) to maintain systolic blood pressure to its value before heart mobilization. Measurements were also taken before sternal closure (Tfinal).

RESULTS

Three hundred and two pairs of data were analyzed using the Bland and Altman method. Bias, standard deviation (SD) of the bias (precision), and degree of agreement (bias +/- 2 SD) were calculated. Based on published literature, we considered that the highest degree of agreement should be < 0.5 L.min(-1) to consider both methods as interchangeable. At T0, bias and SD of bias between TD-CO and ED-CO were -0.1 +/- 1.0 L.min(-1). Immediately before heart stabilization, bias +/- SD was 0.6 +/- 1.0 L.min(-1) and after heart displacement, 0.5 +/- 0.8 L.min(-1). At Tfinal, bias +/- SD was 0.7+/- 0.7 L.min(-1).

CONCLUSION

Because the degree of agreement was > 0.5 L.min(-1) at all measurement periods except T0, we conclude that TD and ED are not interchangeable at any time during OPCAB surgery.

Noninvasive cardiac output monitoring by aortic blood flow determination: evaluation of the Sometec Dynemo-3000 system

OBJECTIVE

The Sometec Dynemo-3000 system allows the permanent measurement of descending aorta diameter by an echographic (A-scan) device and the blood flow velocity by a pulse Doppler velocimeter. The Dynemo-3000 then furnishes a new hemodynamic parameter, i.e., descending aortic blood flow (ABF), which is a fraction of the cardiac output (CO). We evaluate the ability of this system to measure the aortic diameter and to accurately detect ABF changes.

DESIGN

A case study prospective trial.

SETTING

A 24-bed medical intensive care unit of a 1,100-bed university hospital.

PATIENTS

Twenty critically ill patients fully sedated, mechanically ventilated, and monitored by a pulmonary artery catheter.

INTERVENTIONS

CO values determined by conventional thermodilution method (TD-CO) and ABF were recorded during the study, which included two initial baseline periods, a dobutamine infusion (5 microg/kg/min) interval of 30 mins, and a third baseline period. To assess the accuracy of A-scan, aortic diameter was measured by transesophageal echocardiography. The difference between echocardiography and A-scan was used to determine bias and precision for aortic diameter measurements. TD-CO and ABF variations were analyzed using Kruskal-Wallis and Wilcoxon tests. Association between TD-CO and ABF values was determined by calculating the linear correlation coefficient. The ability of ABF to detect a TD-CO >6.0 L/min and its variations >13% was analyzed by determination of sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values.

MEASUREMENTS AND MAIN RESULTS

Aortic diameter measurements by A-scan and bidimensional methods were 23.0+/-2.8 mm (SD) and 24.2+/-2.7 mm, respectively. Bias and precision were 1.1 mm and 1.4 mm (95% confidence interval: -1.9 to 3.7), respectively. During the course of dobutamine infusion, we observed a significant increase of TD-CO mean value from 6.65+/-1.53 L/min to 9.30+/-2.5 L/min (p=.0008), and a parallel and significant increase in ABF mean value from 4.34+/-1.18 L/min to 5.70+/-1.63 L/min (p= .0029). Absolute TD-CO and ABF values had a correlation coefficient of 0.80. For detection of an increased TD-CO, PPV and NPV were 87% and 86%, respectively. For detection of TD-CO changes >13%, PPV and NPV were 80% and 94%, respectively.

CONCLUSIONS

The Dynemo-3000 system is able to display the real aortic diameter, which is one of the most important components of this noninvasive ultrasonic technique. When compared with TD-CO, the ABF determination provided by this ultrasonic device constitutes a reliable noninvasive tool for estimating CO and tracking its changes.

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.

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

PURPOSE

Invasive haemodynamic monitoring during general anaesthesia in infants is usually limited to very high risk operations, such as cardiac surgery. Nevertheless, different surgical procedures and/or anaesthetic techniques justify additional monitoring for children, as for adults. The aim of this preliminary study was to evaluate the feasibility of using a new echo-Doppler device (Dynemo 3000) capable of measuring continuous aortic blood flow during general anaesthesia in infants.

METHODS

Aortic blood flow (ABF) was measured with a small oesophageal probe designed for newborns and infants. The aortic flowmeter was connected with satellite devices to visualise the haemodynamic profile which included ABF, pre-ejection period (PEPi), left ventricular ejection time (LVETi), mean arterial pressure, heart rate, stroke volume and systemic vascular resistance. Twelve infants, aged 8-26 mo, undergoing surgery under general anaesthesia were successively included in the evaluation of this device. Isoflurane (1% end-expired concentration) was introduced to maintain anaesthesia after induction with halothane, midazolam, fentanyl and atracurium.

RESULTS

Correct positioning of the probe was easily obtained in all cases and the recording quality was excellent, whatever the operative position. Recordings of haemodynamic data showed some myocardial depression from isoflurane: decreased ABF (indexed to body surface area) and lengthened PEP/LVET (2.24 +/- 0.53 L.min-1.m-2 and 0.32 +/- 0.05 respectively, before introduction of isoflurane and 1.71 +/ 0.53 L.min-1.m-2 (P = 0.027) and 0.39 +/- 0.06 (P = 0.007) with isoflurane).

CONCLUSION

These preliminary results suggest that this continuous ABF echo-Doppler device may be valuable for peri anaesthetic monitoring in infants.

[Diagnosis of heart arrest caused by CO2 embolism during laparoscopic surgery by monitoring of aortic blood flow and capnography]

We report the case of a 25-year-old woman undergoing a laparoscopic cholecystectomy, who suffered, one min after the beginning of intraperitoneal insufflation of CO2 (2.5 L at a pressure of 10 mmHg), a sudden decrease to 0.8 L.min-1 of the aortic blood flow (ABF), monitored in the descending aorta by an oesophageal echo-Doppler probe, associated with a decrease of PetCO2 to 15 mmHg and of SpO2 readings to 88%. Despite the lack of simultaneous changes in heart rate and arterial pressure, pulmonary gas embolism (GE) was suspected. The pneumoperitoneum was exsufflated and CPR was started because of circulatory inefficiency. Ten min later, efficient spontaneous cardiac activity restarted, whereas PetCO2 and ABF returned rapidly to normal values. At this time, a typical gas noise was clearly obtained through the oesophageal Doppler transducer. The patient remained in deep coma (GCS:6) with a left sided hemiplegia. However, she fully recovered after four sessions of hyperbaric oxygenation. Simultaneous continuous monitoring of ABF and PetCO2 allows an undelayed recognition of major circulatory disturbances, before significant changes in heart rate and arterial pressure occur.