Tissue pH: A New Clinical Tool

Wolpert, Paul W.; Noller, Kenneth L.; Shaughnessy, Dennis; Houchin, Donald N.; Baccari, Manuel; Miller, Fletcher A.

doi:10.1001/archsurg.1970.01340260212031

Cited by 18 publications

(4 citation statements)

References 4 publications

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“…The development of a medical device able to detect the fetal hypoxia-acidosis status in a precise and continuous manner would be a big step forward in the clinical managing of this population. To this end, previous evidence has demonstrated the feasibility of sensor devices being inserted in different tissues, including in the vascular system [10][11][12][13], the brain [14][15][16][17], the gastric system [18], subcutaneously and intramuscularly [19][20][21][22] to monitor and detect acid-base status. However, most of these sensors are not designed to be used during the intrauterine period.…”

Section: Introductionmentioning

confidence: 99%

Non-invasive monitoring of pH and oxygen using miniaturized electrochemical sensors in an animal model of acute hypoxia

et al. 2021

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Background One of the most prevalent causes of fetal hypoxia leading to stillbirth is placental insufficiency. Hemodynamic changes evaluated with Doppler ultrasound have been used as a surrogate marker of fetal hypoxia. However, Doppler evaluation cannot be performed continuously. As a first step, the present work aimed to evaluate the performance of miniaturized electrochemical sensors in the continuous monitoring of oxygen and pH changes in a model of acute hypoxia-acidosis. Methods pH and oxygen electrochemical sensors were evaluated in a ventilatory hypoxia rabbit model. The ventilator hypoxia protocol included 3 differential phases: basal (100% FiO2), the hypoxia-acidosis period (10% FiO2) and recovery (100% FiO2). Sensors were tested in blood tissue (ex vivo sensing) and in muscular tissue (in vivo sensing). pH electrochemical and oxygen sensors were evaluated on the day of insertion (short-term evaluation) and pH electrochemical sensors were also tested after 5 days of insertion (long-term evaluation). pH and oxygen sensing were registered throughout the ventilatory hypoxia protocol (basal, hypoxia-acidosis, and recovery) and were compared with blood gas metabolites results from carotid artery catheterization (obtained with the EPOC blood analyzer). Finally, histological assessment was performed on the sensor insertion site. One-way ANOVA was used for the analysis of the evolution of acid-based metabolites and electrochemical sensor signaling results; a t-test was used for pre- and post-calibration analyses; and chi-square analyses for categorical variables. Results At the short-term evaluation, both the pH and oxygen electrochemical sensors distinguished the basal and hypoxia-acidosis periods in both the in vivo and ex vivo sensing. However, only the ex vivo sensing detected the recovery period. In the long-term evaluation, the pH electrochemical sensor signal seemed to lose sensibility. Finally, histological assessment revealed no signs of alteration on the day of evaluation (short-term), whereas in the long-term evaluation a sub-acute inflammatory reaction adjacent to the implantation site was detected. Conclusions Miniaturized electrochemical sensors represent a new generation of tools for the continuous monitoring of hypoxia-acidosis, which is especially indicated in high-risk pregnancies. Further studies including more tissue-compatible material would be required in order to improve long-term electrochemical sensing.

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Section: Introductionmentioning

confidence: 99%

Non-invasive monitoring of pH and oxygen using miniaturized electrochemical sensors in an animal model of acute hypoxia

et al. 2021

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“…Going in this line, previous evidences have demonstrated the feasibility of sensors devices inserted in different tissues, including vascular system [10][11][12][13], brain [14][15][16][17], gastric system [18], subcutaneous or intramuscular [19][20][21][22], to monitor and detect acid-base status. However, most of these sensors are not designed to be used in fetuses during intrauterine period.…”

Section: Introductionmentioning

confidence: 99%

Non-Invasive Monitoring of pH and Oxygen Using Miniaturized Electrochemical Sensors in an Animal Model of Acute Hypoxia

Pla

Berdún

Mir

et al. 2020

Preprint

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BackgroundOne of the most prevalent causes of fetal hypoxia leading to stillbirth is placental insufficiency. Hemodynamic changes evaluated with Doppler ultrasound have been used as a surrogate marker of fetal hypoxia. However, Doppler evaluation cannot be performed continuously. As a first step, the present work aimed to evaluate the performance of miniaturized electrochemical sensors in continuous monitoring of oxygen and pH changes in a model of acute hypoxia-acidosis. MethodspH and oxygen electrochemical sensors were evaluated in a ventilatory hypoxia rabbit model. The ventilator hypoxia protocol included three differential phases: basal (100% FiO2), hypoxia-acidosis period (10% FiO2) and recovery (100% FiO2). Sensors were tested in blood tissue (ex vivo sensing) and in the muscular tissue (in vivo sensing). pH electrochemical and oxygen sensors were evaluated at the same day of insertion (short-term evaluation) and pH electrochemical sensors were also tested after 5 days of insertion (long-term evaluation). pH and oxygen sensing were registered during all the ventilatory hypoxia protocol (basal, hypoxia-acidosis and recovery) and were compared with blood gas metabolites results from carotid artery catheterization (EPOC® blood analyzer). Finally, histological assessment was performed on the site of the sensor’s insertion. One-way ANOVA was used for the analysis of the evolution of acid-based metabolites and electrochemical sensor signaling results; T-test was used for pre and post calibration analyses; and chi-square analyses for categorical variables. ResultsAt the short-term evaluation, both pH and oxygen electrochemical sensors distinguished the basal and hypoxia-acidosis periods in the in vivo and ex vivo sensing. However, only the ex vivo sensing detected recovery period. At the long-term evaluation, pH electromechanical sensor signal seemed to lose sensibility. Finally, histological assessment revealed no signs of alteration at the same day of evaluation (short-term), whereas at the long-term evaluation sub-acute inflammatory reaction adjacent to the site of the implantation was detected. ConclusionsThe use of miniaturized electrochemical sensors open a new generation of tools for continuous monitoring of hypoxia-acidosis, especially indicated in high risk pregnancies. Further studies including more tissue-compatible material would be required in order to improve the long-term electromechanical sensing.

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“…The presence of lactate contributes to an increase in H þ ion activity, which is proportional to a decrease in pH. Thus, pH can be used as an indication of a reduction of tissue perfusion [6,7,9].…”

Section: Introductionmentioning

confidence: 99%

“…For this purpose, small devices with low drift, easy calibration, immunity to electrode fouling and long life-time are required. Wolpert et al compared serum pH measurements to that of tissue pH [7]. They found that tissue pH, when compared to serum pH, had the advantages of reacting earlier to changes in tissue perfusion and it could be measured with minimal invasiveness.…”

Section: Introductionmentioning

confidence: 99%

Physiological monitoring of tissue pH: In vitro characterisation and in vivo validation of a quinone-modified carbon paste electrode

Herdman

Breslin

Finnerty

2019

Electrochimica Acta

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The fluctuation of physiological pH from homeostatic levels has the potential to cause life threatening complications unless counteracted in a timely manner. Therefore, the development of reliable and accurate sensors for the continuous monitoring of pH is of vital importance for clinical monitoring. Herein, we describe the extensive in vitro characterisation of a quinone-modified carbon paste electrode (CPE) and its subsequent in vivo validation in the peripheral tissue of anaesthetised rats. Sensocompatibility investigations identified stable and accurate measurements in lipid (phosphatidylethanolamine; PEA) and protein (bovine serum albumin; BSA) solutions when the pH sensor was continuously cycled for nine hours in the physiological contaminants. The influence of endogenous electroactive molecules e.g., ascorbic acid and uric acid and pharmacological interferents e.g., acetaminophen and acetylsalicylic acid was deemed negligible on the pH sensitive peak. Furthermore, there was no impact of ionic strength and the quinone oxidation peak remained selective for H þ over other endogenous cations. The effect of temperature and a pseudo reference electrode (PRE) on the sensor performance have also been elucidated. The efficacy of the modified-CPE to respond to in vivo tissue pH dynamics was demonstrated using a model of peripheral ischaemia and sodium bicarbonate injections. Collectively, this body of evidence clearly support the ability of the quinone-modified CPE to continuously measure pH fluctuations under physiological conditions.

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Tissue pH: A New Clinical Tool

Cited by 18 publications

References 4 publications

Non-invasive monitoring of pH and oxygen using miniaturized electrochemical sensors in an animal model of acute hypoxia

Non-invasive monitoring of pH and oxygen using miniaturized electrochemical sensors in an animal model of acute hypoxia

Non-Invasive Monitoring of pH and Oxygen Using Miniaturized Electrochemical Sensors in an Animal Model of Acute Hypoxia

Physiological monitoring of tissue pH: In vitro characterisation and in vivo validation of a quinone-modified carbon paste electrode

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