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A simple and novel method to monitor breathing and heart rate in awake and urethane-anesthetized newborn rodents.

Zehendner CM, Luhmann HJ, Yang JW - PLoS ONE (2013)

Bottom Line: Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state.However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal.Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. Zehendner@uni-mainz.de

ABSTRACT
Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state. However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal. Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal. These techniques can be easily installed and are used in the present study in unrestrained awake and anesthetized neonatal C57/Bl6 mice and Wistar rats between postnatal day 0 and 7. In line with previous reports from awake rodents we demonstrate that heart rate in rats and mice increases during the first postnatal week. Respiratory frequency did not differ between both species, but heart rate was significantly higher in mice than in rats. Further our data indicate that urethane, an agent that is widely used for anesthesia, induces a hypoventilation in neonates whilst heart rate remains unaffected at a dose of 1 g per kg body weight. Of note, hypoventilation induced by urethane was not detected in rats at postnatal 0/1. To verify the detected hypoventilation we performed blood gas analyses. We detected a respiratory acidosis reflected by a lower pH and elevated level in CO2 tension (pCO2) in both species upon urethane treatment. Furthermore we found that metabolism of urethane is different in P0/1 mice and rats and between P0/1 and P6/7 in both species. Our findings underline the usefulness of monitoring basic cardio-respiratory parameters in neonates during anesthesia. In addition our study gives information on developmental changes in heart and breathing frequency in newborn mice and rats and the effects of urethane in both species during the first postnatal week.

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Monitoring setup, ECG and breathing detection.Rodents were placed on a temperature monitored heating pad and connected to ECG electrodes. A thermal probe was used to control the body temperature of the animal. Data of heart and breathing rates were collected with analog digital converters (ADC, A). Recordings from an awake P7 mouse showing a raw data trace of breathing movements including breathing cycle duration (B, trace 1). Heart rate recordings in awake animals (raw data: B,trace 2) were filtered at 10–200 Hz band pass which allowed identification of QRS complexes (B,trace 3). Effect of urethane on breathing and heart rate in representative recordings of the same animal 30–60 minutes after urethane administration (C). Note the different pattern of the PZT signal (C, trace 1) in comparison with the awake state in B trace 1. After filtering the ECG raw data (C, trace 2) in some recordings beside QRS complexes P and T waves could be identified (C, trace 3 inset).
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pone-0062628-g001: Monitoring setup, ECG and breathing detection.Rodents were placed on a temperature monitored heating pad and connected to ECG electrodes. A thermal probe was used to control the body temperature of the animal. Data of heart and breathing rates were collected with analog digital converters (ADC, A). Recordings from an awake P7 mouse showing a raw data trace of breathing movements including breathing cycle duration (B, trace 1). Heart rate recordings in awake animals (raw data: B,trace 2) were filtered at 10–200 Hz band pass which allowed identification of QRS complexes (B,trace 3). Effect of urethane on breathing and heart rate in representative recordings of the same animal 30–60 minutes after urethane administration (C). Note the different pattern of the PZT signal (C, trace 1) in comparison with the awake state in B trace 1. After filtering the ECG raw data (C, trace 2) in some recordings beside QRS complexes P and T waves could be identified (C, trace 3 inset).

Mentions: Mice or rats were placed on a PZT element equipped with a temperature monitored heating pad. Body temperature was monitored by a thermal probe and maintained at 37°C. Two soft electrodes were attached to the right paw and the left hind limb or tail (Figure 1A). We recorded breathing in awake animals by detection of movements of the thorax or abdomen (Figure 1B, trace 1) with the help of the PZT. Via electrocardiographic recording we determined heart frequency in the awake animals (Figure 1B, traces 2 and 3). Similar results were obtained in urethane anesthetized animals (Figure 1C). After 10 to 200 Hz band pass filtering of the ECG raw data (Figure 1B, C, trace 2) QRS complexes could be better identified (Figure 1B, C, trace 3). In some recordings a P-wave followed by a QRS complex and a T wave could be detected (Figure 1C, inset).


A simple and novel method to monitor breathing and heart rate in awake and urethane-anesthetized newborn rodents.

Zehendner CM, Luhmann HJ, Yang JW - PLoS ONE (2013)

Monitoring setup, ECG and breathing detection.Rodents were placed on a temperature monitored heating pad and connected to ECG electrodes. A thermal probe was used to control the body temperature of the animal. Data of heart and breathing rates were collected with analog digital converters (ADC, A). Recordings from an awake P7 mouse showing a raw data trace of breathing movements including breathing cycle duration (B, trace 1). Heart rate recordings in awake animals (raw data: B,trace 2) were filtered at 10–200 Hz band pass which allowed identification of QRS complexes (B,trace 3). Effect of urethane on breathing and heart rate in representative recordings of the same animal 30–60 minutes after urethane administration (C). Note the different pattern of the PZT signal (C, trace 1) in comparison with the awake state in B trace 1. After filtering the ECG raw data (C, trace 2) in some recordings beside QRS complexes P and T waves could be identified (C, trace 3 inset).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3643944&req=5

pone-0062628-g001: Monitoring setup, ECG and breathing detection.Rodents were placed on a temperature monitored heating pad and connected to ECG electrodes. A thermal probe was used to control the body temperature of the animal. Data of heart and breathing rates were collected with analog digital converters (ADC, A). Recordings from an awake P7 mouse showing a raw data trace of breathing movements including breathing cycle duration (B, trace 1). Heart rate recordings in awake animals (raw data: B,trace 2) were filtered at 10–200 Hz band pass which allowed identification of QRS complexes (B,trace 3). Effect of urethane on breathing and heart rate in representative recordings of the same animal 30–60 minutes after urethane administration (C). Note the different pattern of the PZT signal (C, trace 1) in comparison with the awake state in B trace 1. After filtering the ECG raw data (C, trace 2) in some recordings beside QRS complexes P and T waves could be identified (C, trace 3 inset).
Mentions: Mice or rats were placed on a PZT element equipped with a temperature monitored heating pad. Body temperature was monitored by a thermal probe and maintained at 37°C. Two soft electrodes were attached to the right paw and the left hind limb or tail (Figure 1A). We recorded breathing in awake animals by detection of movements of the thorax or abdomen (Figure 1B, trace 1) with the help of the PZT. Via electrocardiographic recording we determined heart frequency in the awake animals (Figure 1B, traces 2 and 3). Similar results were obtained in urethane anesthetized animals (Figure 1C). After 10 to 200 Hz band pass filtering of the ECG raw data (Figure 1B, C, trace 2) QRS complexes could be better identified (Figure 1B, C, trace 3). In some recordings a P-wave followed by a QRS complex and a T wave could be detected (Figure 1C, inset).

Bottom Line: Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state.However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal.Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. Zehendner@uni-mainz.de

ABSTRACT
Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state. However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal. Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal. These techniques can be easily installed and are used in the present study in unrestrained awake and anesthetized neonatal C57/Bl6 mice and Wistar rats between postnatal day 0 and 7. In line with previous reports from awake rodents we demonstrate that heart rate in rats and mice increases during the first postnatal week. Respiratory frequency did not differ between both species, but heart rate was significantly higher in mice than in rats. Further our data indicate that urethane, an agent that is widely used for anesthesia, induces a hypoventilation in neonates whilst heart rate remains unaffected at a dose of 1 g per kg body weight. Of note, hypoventilation induced by urethane was not detected in rats at postnatal 0/1. To verify the detected hypoventilation we performed blood gas analyses. We detected a respiratory acidosis reflected by a lower pH and elevated level in CO2 tension (pCO2) in both species upon urethane treatment. Furthermore we found that metabolism of urethane is different in P0/1 mice and rats and between P0/1 and P6/7 in both species. Our findings underline the usefulness of monitoring basic cardio-respiratory parameters in neonates during anesthesia. In addition our study gives information on developmental changes in heart and breathing frequency in newborn mice and rats and the effects of urethane in both species during the first postnatal week.

Show MeSH
Related in: MedlinePlus