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Cardiovascular response to hyperoxemia, hemodilution and burns: a clinical and experimental study
Linköping University, Department of Medicine and Health Sciences, Anesthesiology . Linköping University, Faculty of Health Sciences.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The last decades less invasive monitoring and analytical tools have been developed for the evaluation of myocardial mechanics in clinical praxis. In critical care, these are longed-for complements to pulmonary artery catheter monitoring, additionally offering previously inaccessible information. This work is aimed, during fluid-replacement and oxygen therapy, to determine the physiological interface of ventricular and vascular mechanical properties, which result in the transfer of blood from the heart to appropriate circulatory beds. In prospective clinical studies we investigated previously cardiovascular healthy adults during hyperoxemia, and during preoperative acute normovolemic hemodilution or early fluid resuscitation of severe burn victims. Echocardiography was used in all studies, transthoracic for healthy volunteers and transesophageal for patients. For vascular parameters and for control purposes pulmonary artery Swan-Ganz catheter, calibrated external pulse recordings, whole body impedance cardiography, and transpulmonel thermodilution method were applied.

We detected no significant change in blood pressure or heart rate, the two most often used parameters for patient monitoring. During preoperative acute normovolemic hemodilution a reduction of hemoglobin to 80 g/l did not compromise systolic or diastolic myocardial function. Cardiac volumes and flow increased with a concomitant fall in systemic vascular resistance while oxygen delivery seemed maintained. Supplemental oxygen therapy resulted in a linear dose-response between arterial oxygen and cardiovascular parameters, suggesting a direct vascular effect. Cardiac flow decreased and vascular resistance increased from hyperoxemia, and a decrease of venous return implied extracardial blood-pooling. Severe burns result in hypovolemic shock if not properly treated. The commonly used Parkland fluid replacement strategy, with urinary output and mean arterial pressure as endpoints, has recently been questioned. Applying this strategy, only transient early central hypovolemia was recorded, while dimensional preload, global left ventricular systolic function and oxygen delivery or consumption remained within normal ranges during the first 36 hours after accident. Signs of restrictive left ventricular diastolic function were detected in all patients and regional unstable systolic dysfunction was recognized in every other patient, and was consistent with myocardial marker leakage. Severe burns thereby cause myocardial stiffness and systolic regional dysfunction, which may not be prevented only by central normovolemia and adequate oxygenation.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik , 2007.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1013
Keyword [en]
Anesthesia, general, Burns, Echocardiography, transesophageal, Hemodilution, emodynamic processes, Hyperoxia
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:liu:diva-10633ISBN: 978-91-85831-11-1 (print)OAI: oai:DiVA.org:liu-10633DiVA: diva2:17348
Public defence
2007-10-25, Elsa Brännströmssalen Universitetssjukhuset i Linköping, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Note
On the day of the defence date the status of article II was: In Press.Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2009-08-22
List of papers
1. Transesophageal echocardiographic hemodynamic monitoring during preoperative acute normovolemic hemodilution
Open this publication in new window or tab >>Transesophageal echocardiographic hemodynamic monitoring during preoperative acute normovolemic hemodilution
2000 (English)In: Anesthesiology, ISSN 0003-3022 (print), 1528-1175 (online), Vol. 92, no 5, 1250-1256 p.Article in journal (Refereed) Published
Abstract [en]

Background: Preoperative acute normovolemic hemodilution may compromise oxygen transport. The aims of our study were to describe the hemodynamic effects of normovolemic hemodilution and to determine its effect on systolic and diastolic cardiac function by multiplane transesophageal echocardiography.

Methods: In eight anesthetized patients (aged 13-51 yr) without heart disease, hemoglobin was reduced in steps from 123 ± 8 (mean ± SD) to 98 ± 3 and to 79 ± 5 g/l. Hemodynamic measurements (intravascular pressures, thermodilution cardiac output, and echocardiographic recordings) were obtained during a stabilization period and at each level of hemodilution. Left ventricular wall motion was monitored continuously, and Doppler variables, annular motion, and changes in ejection fractional area were analyzed off-line.

Results: During hemodilution, cardiac output by thermodilution increased by 16 ± 7% and 26 ± 10%, corresponding well to the increase in cardiac output as measured by Doppler (difference, 0.32 ± 1.2 l/min). Systemic vascular resistance fell 16 ± 14% and 23 ± 9% and pulmonary capillary wedge pressure increased slightly (2 ± 2 mmHg), whereas other pressures, heart rate, wall motion, and diastolic Doppler variables remained unchanged. Ejection fractional area change increased from 44 ± 7% to 54 ± 10% and 60 ± 9% as a result of reduced end-systolic and increased end-diastolic left ventricular areas.

Conclusions: A reduction in hemoglobin to 80 g/l during acute normovolemic hemodilution does not normally compromise systolic or diastolic myocardial function as determined by transesophageal echocardiography. Preload, left ventricular ejection fraction, and cardiac output increase with a concomitant fall in systemic vascular resistance.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-12898 (URN)
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2009-08-17
2. Human cardiovascular dose-response to supplemental oxygen
Open this publication in new window or tab >>Human cardiovascular dose-response to supplemental oxygen
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2007 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 191, no 1, 15-24 p.Article in journal (Refereed) Published
Abstract [en]

Aim: The aim of the study was to examine the central and peripheral cardiovascular adaptation and its coupling during increasing levels of hyperoxaemia. We hypothesized a dose-related effect of hyperoxaemia on left ventricular performance and the vascular properties of the arterial tree.

Methods: Oscillometrically calibrated arterial subclavian pulse trace data were combined with echocardiographic recordings to obtain non-invasive estimates of left ventricular volumes, aortic root pressure and flow data. For complementary vascular parameters and control purposes whole-body impedance cardiography was applied. In nine (seven males) supine, resting healthy volunteers, aged 23–48 years, data was collected after 15 min of air breathing and at increasing transcutaneous oxygen tensions (20, 40 and 60 kPa), accomplished by a two group, random order and blinded hyperoxemic protocol.

Results: Left ventricular stroke volume [86 ± 13 to 75 ± 9 mL (mean ± SD)] and end-diastolic area (19.3 ± 4.4 to 16.8 ± 4.3 cm2) declined (P < 0.05), and showed a linear, negative dose–response relationship to increasing arterial oxygen levels in a regression model. Peripheral resistance and characteristic impedance increased in a similar manner. Heart rate, left ventricular fractional area change, end-systolic area, mean arterial pressure, arterial compliance or carbon dioxide levels did not change.

Conclusion: There is a linear dose–response relationship between arterial oxygen and cardiovascular parameters when the systemic oxygen tension increases above normal. A direct effect of supplemental oxygen on the vessels may therefore not be excluded. Proximal aortic and peripheral resistance increases from hyperoxaemia, but a decrease of venous return implies extra cardiac blood-pooling and compensatory relaxation of the capacitance vessels.

Keyword
arterial compliance, end-diastolic area, hyperoxaemia, hyperoxia, normocapnia, stroke volume, vascular resistance
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-12899 (URN)10.1111/j.1748-1716.2007.01710.x (DOI)
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2017-12-13
3. Hemodynamic Changes During Resuscitation After Burns Using the Parkland Formula
Open this publication in new window or tab >>Hemodynamic Changes During Resuscitation After Burns Using the Parkland Formula
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2009 (English)In: Journal of Trauma, ISSN 0022-5282, E-ISSN 1529-8809, Vol. 66, no 2, 329-336 p.Article in journal (Refereed) Published
Abstract [en]

Background: The Parkland formula (2-4 mL/kg/burned area of total body surface area %) with urine output and mean arterial pressure (MAP) as endpoints; for the fluid resuscitation in burns is recommended all over the world. There has recently been a discussion on whether central circulatory endpoints should be used instead, and also whether volumes of fluid should be larger. Despite this, there are few central hemodynamic data available in the literature about the results when the formula is used correctly.

Methods: Ten burned patients, admitted to our unit early, and with a burned area of >20% of total body sur-face area were investigated at 12, 24, and 36 hours after injury. Using transesophageal echocardiography, pulmonary artery catheterization, and transpulmonary thermodilution to monitor them, we evaluated the cardiovascular coupling when urinary output and MAP were used as endpoints.

Results: Oxygen transport variables, heart rate, MAP, and left ventricular fractional area, did not change significantly during fluid resuscitation. Left ventricular end-systolic and end-diastolic area and global end-diastolic volume index increased from subnormal values at 12 hours to normal ranges at 24 hours after the burn. Extravascular lung intrathoracal blood volume ratio was increased 12 hours after the burn.

Conclusions: Preload variables, global systolic function, and oxygen transport recorded simultaneously by three separate methods showed no need to increase the total fluid volume within 36 hours of a major burn. Early (12 hours) signs of central circulatory hypovolemia, however, support more rapid infusion of fluid at the beginning of treatment.

Keyword
Cardiovascular coupling, Echocardiography, Hemodynamic monitoring, Fractional area change, Global end-diastolic volume
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-17146 (URN)10.1097/TA.0b013e318165c822 (DOI)
Available from: 2009-03-07 Created: 2009-03-07 Last updated: 2017-12-13
4. Cardiac dysfunction after burns
Open this publication in new window or tab >>Cardiac dysfunction after burns
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2008 (English)In: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 34, no 5, 603-609 p.Article in journal (Refereed) Published
Abstract [en]

Objectives

Using transoesophageal echocardiography (TEE) we investigated the occurrence, and the association of possible abnormalities of motion of the regional wall of the heart (WMA) or diastolic dysfunction with raised troponin concentrations, or both during fluid resuscitation in patients with severe burns.

Patients and methods

Ten consecutive adults (aged 36–89 years, two women) with burns exceeding 20% total burned body surface area who needed mechanical ventilation were studied. Their mean Baux index was 92.7, and they were resuscitated according to the Parkland formula. Thirty series of TEE examinations and simultaneous laboratory tests for myocyte damage were done 12, 24, and 36 h after the burn.

Results

Half (n = 5) the patients had varying grades of leakage of the marker that correlated with changeable WMA at 12, 24 and 36 h after the burn (p ≤ 0.001, 0.044 and 0.02, respectively). No patient had WMA and normal concentrations of biomarkers or vice versa. The mitral deceleration time was short, but left ventricular filling velocity increased together with stroke volume.

Conclusion

Acute myocardial damage recorded by both echocardiography and leakage of troponin was common, and there was a close correlation between them. This is true also when global systolic function is not deteriorated. The mitral flow Doppler pattern suggested restrictive left ventricular diastolic function.

Keyword
Diastolic and regional systolic dysfunction; Echocardiography; Myocardial injury; Fluid resuscitation in burns; Myocardial infarction; Troponin
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-12901 (URN)10.1016/j.burns.2007.11.013 (DOI)
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2017-12-13

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