Continuous intrapartum pH, pO2, pCO2, and SpO2 monitoring

Endogenous brain-sparing responses in brain pH and PO2 in a rodent model of birth asphyxia

AIM

To study brain-sparing physiological responses in a rodent model of birth asphyxia which reproduces the asphyxia-defining systemic hypoxia and hypercapnia.

METHODS

Steady or intermittent asphyxia was induced for 15-45 minutes in anaesthetized 6- and 11-days old rats and neonatal guinea pigs using gases containing 5% or 9% O₂ plus 20% CO₂ (in N₂ ). Hypoxia and hypercapnia were induced with low O₂ and high CO₂ respectively. Oxygen partial pressure (PO₂ ) and pH were measured with microsensors within the brain and subcutaneous ("body") tissue. Blood lactate was measured after asphyxia.

RESULTS

Brain and body PO₂ fell to apparent zero with little recovery during 5% O₂ asphyxia and 5% or 9% O₂ hypoxia, and increased more than twofold during 20% CO₂ hypercapnia. Unlike body PO₂ , brain PO₂ recovered rapidly to control after a transient fall (rat), or was slightly higher than control (guinea pig) during 9% O₂ asphyxia. Asphyxia (5% O₂ ) induced a respiratory acidosis paralleled by a progressive metabolic (lact)acidosis that was much smaller within than outside the brain. Hypoxia (5% O₂ ) produced a brain-confined alkalosis. Hypercapnia outlasting asphyxia suppressed pH recovery and prolonged the post-asphyxia PO₂ overshoot. All pH changes were accompanied by consistent shifts in the blood-brain barrier potential.

CONCLUSION

Regardless of brain maturation stage, hypercapnia can restore brain PO₂ and protect the brain against metabolic acidosis despite compromised oxygen availability during asphyxia. This effect extends to the recovery phase if normocapnia is restored slowly, and it is absent during hypoxia, demonstrating that exposure to hypoxia does not mimic asphyxia.

Intrauterine resuscitation during the second stage of term labour by maternal hyperoxygenation versus conventional care: study protocol for a randomised controlled trial (INTEREST O2)

BACKGROUND

Perinatal asphyxia is, even in developed countries, one the major causes of neonatal morbidity and mortality. Therefore, if foetal distress during labour is suspected, one should try to restore foetal oxygen levels or aim for immediate delivery. However, studies on the effect of intrauterine resuscitation during labour are scarce. We designed a randomised controlled trial to investigate the effect of maternal hyperoxygenation on the foetal condition. In this study, maternal hyperoxygenation is induced for the treatment of foetal distress during the second stage of term labour.

METHODS/DESIGN

This study is a single-centre randomised controlled trial being performed in a tertiary hospital in The Netherlands. From among cases of a suboptimal or abnormal foetal heart rate pattern during the second stage of term labour, a total of 116 patients will be randomised to the control group, where normal care is provided, or to the intervention group, where before normal care 100% oxygen is supplied to the mother by a non-rebreathing mask until delivery. The primary outcome is change in foetal heart rate pattern. Secondary outcomes are Apgar score, mode of delivery, admission to the neonatal intensive care unit and maternal side effects. In addition, blood gas values and malondialdehyde are determined in umbilical cord blood.

DISCUSSION

This study will be the first randomised controlled trial to investigate the effect of maternal hyperoxygenation for foetal distress during labour. This intervention should be recommended only as a treatment for intrapartum foetal distress, when improvement of the foetal condition is likely and outweighs maternal and neonatal side effects.

TRIAL REGISTRATION

EudraCT, 2015-001654-15; registered on 3 April 2015. Dutch Trial Register, NTR5461; registered on 20 October 2015.

Comparison of epidural tramadol-ropivacaine and fentanyl-ropivacaine for labor analgesia: a prospective randomized study

BACKGROUND

To test the hypothesis that 5 mg/mL tramadol is superior to 3 ?g/mL fentanyl when combined with 0.125% ropivacaine in parturients undergoing labor during epidural analgesia.

METHODS

Sixty-one parturients undergoing labor selected for delivery with epidural analgesia were randomized into two groups: Group tramadol (0.125% ropivacaine plus tramadol 5 mg/mL) and Group fentanyl (0.125% ropivacaine plus fentanyl 3 ug/mL). Hemodynamics, rate of cesarean delivery, sensory block level, Bromage motor scale scores, instrument-assisted delivery, oxytocin use, visual analog scale (VAS) scores, Apgar scores, umbilical cord artery gas analysis, and maternal side-effects including nausea, vomiting, pruritus, urinary retention, shivering, hypotension, and respiratory depression were recorded.

RESULTS

The two groups had no significant differences with respect to maternal hemodynamics, neonatal heart rate, VAS scores, rate of cesarean delivery, sensory block level, Bromage motor scale scores, instrument-assisted delivery, oxytocin use, hypotension, nausea, vomiting, and respiratory depression (p > 0.05). The incidence of pruritus, shivering, and urinary retention were more commonly observed in Group fentanyl despite there was no significant difference between the two groups. Umbilical artery pH was significantly lower while PCO(2) was higher in Group fentanyl than Group tramadol (p = 0.003 and p = 0.026, respectively). Birth-weight, umbilical artery PO(2) and base deficit, and Apgar scores at 1 and 5 min were comparable between the two groups (p > 0.05).

CONCLUSIONS

Our observations suggest that tramadol seems to be a safe alternative to fentanyl for labor analgesia due to its similar analgesic efficacy.

Real-time intraoperative detection of tissue hypoxia in gastrointestinal surgery by wireless pulse oximetry

OBJECTIVE

Dehiscence or leakage after bowel anastomoses is associated with high morbidity and mortality. Perfusion and local tissue oxygenation (StO2), independent of systemic oxygen saturation, are fundamental determinants of anastomotic viability. Because current technology is limited for monitoring local StO2 at bowel anastomoses, our goal was to construct a wireless pulse oximeter (WiPOX) to monitor real-time intraoperative tissue oxygenation, permitting identification of compromised anastomotic perfusion.

METHODS

We have: (a) designed a handheld device capable of real-time monitoring of serosal and mucosal StO2 through endoscopic ports with wireless data transmission to standard intraoperative monitors, (b) constructed the WiPOX using materials meeting FDA regulations for intraoperative use and reuse, (c) performed accuracy testing in humans by comparing the WiPOX to standard pulse oximeters, and (d) tested WiPOX efficacy for detecting early tissue hypoxia in stomach, intestines, and kidneys in anesthetized rats and swine.

RESULTS

In humans, WiPOX demonstrated accuracy within 3% compared with commercially available pulse oximeters. Application of the WiPOX in rats and swine demonstrated normal serosal and mucosal StO2 and pulse rates in healthy small bowel and stomach. Within 30 s of compromised perfusion, the WiPOX detected bowel hypoxia over a wide range of oxygen saturation (p<0.005). A greater degree of hypoxia was detected in mucosal versus serosal measurements during early ischemia, despite normal appearance of tissue. The onboard sensor-processor unit permitted noninvasive pulse oximetry and integration with current intraoperative monitoring. The contact pressure-sensing head allowed for consistent, high-quality StO2 waveform readouts despite the presence of body fluids.

CONCLUSIONS

We have constructed, validated, and successfully tested a novel wireless pulse oximeter capable of detecting intraoperative tissue hypoxia in open or endoscopic surgery. This device will aid surgeons in detecting anastomotic vascular compromise and facilitate choosing an ideal site for bowel anastomosis by targeting well-perfused tissue with optimal healing capacity.

Genomic approaches in the identification of hypoxia biomarkers in model fish species

Eutrophication leading to hypoxic water conditions has become a major problem in aquatic systems worldwide. Monitoring the levels and biological effects of lowered oxygen levels in aquatic systems may provide data useful in management of natural aquatic environments. Fishes represent an economically important resource that is subject to hypoxia exposure effects. Due to the extreme diversity of fish species and their habitats, fishes in general have evolved unique capabilities to modulate gene expression patterns in response to hypoxic stress. Recent studies have attempted to document quantitative changes in gene expression patterns induced in various fish species in response to reduced dissolved oxygen levels. From a management perspective, the goal of these studies is to provide a more complete characterization of hypoxia responsive genes in fish, as molecular indicators (biomarkers) of ecosystem hypoxic stress.The molecular genetic response to hypoxia is highly complex and overlaps with other stress responses making it difficult to identify hypoxia specific responses using traditional single gene or low throughput approaches. Therefore, recent approaches have been aimed at developing functional genomic (e.g. high density microarray and real-time PCR) and proteomic (two-dimensional fluorescence difference in gel electrophoresis coupled with mass spectrometry based peptide identification) technologies that employ fish species. Many of the fish species utilized in these studies do not have the advantages of underlying genome resources (i.e., genome or transcriptome sequences). Efforts have attempted to establish correlations between discreet molecular responses elicited by fish in response to hypoxia and changes in the genetic profiles of stressed organs or tissues. Notable progress in these areas has been made using several different versions of either cDNA or oligonucleotide based microarrays to profile changes in gene expression patterns in response to hypoxic stress.Due to these efforts, hundreds of hypoxia responsive genes have been identified both from laboratory reared aquaria fish and from feral fish derived from both fresh and saltwater habitats. Herein, we review these reports and the emergence of hypoxia biomarker development in aquatic species. We also include some of our own recent results using the medaka (Oryzias latipes) as a model to define genetic profiles of hypoxia exposure.

Toward quantitative fetal heart rate monitoring

Continuous electronic fetal heart rate (FHR) monitoring during labor is motivated by the clinical experience that fetal distress causes loss of FHR variation and the occurrence of decelerations late during uterine contraction. This practice is of uncertain clinical benefit, perhaps because the interpretation is qualitative. We have developed new quantitative measures and analyzed cardiotocograph records from 148 consecutive patients, 44 of whom had at least one "nonreassuring" epoch. In multivariate regression models, measures of deceleration and variability were significantly associated with the obstetrician's diagnosis (receiver operating characteristic area 0.84, p < 0.05). This approach may be useful clinically.

Comparison of entropy-based regularity estimators: application to the fetal heart rate signal for the identification of fetal distress

This paper considers the multiscale entropy (MSE) approach for estimating the regularity of time series at different scales. Sample entropy (SampEn) and approximate entropy (ApEn) are evaluated in MSE analysis on simulated data to enhance the main features of both estimators. We applied the approximate entropy and the sample entropy estimators to fetal heart rate signals on both single and multiple scales for an early identification of fetal sufferance antepartum. Our results show that the ApEn index significantly distinguishes suffering from normal fetuses between the 30th and the 35th week of gestation. Furthermore, our data shows that the MSE entropy values are reliable indicators of the fetal distress associated with the presence of a pathological condition at birth.

Intrapartum Assessment of the Fetus: Historical and Evidence-Based Practice

The principal purpose of intrapartum fetal assessment is to detect hypoxemia-ischemia, which may lead to fetal jeopardy. A quarter century ago, electronic fetal monitoring replaced intermittent auscultation as the primary method of intrapartum fetal assessment in the United States. It seems that electronic fetal monitoring will continue to be the primary mode of intrapartum fetal assessment, with intermittent auscultation used in some centers primarily for low-risk parturients. From this abridged history of intrapartum fetal monitoring, it is recognized that all surveillance methods bear inherent limitations.

Childbirth and Myoma Treatment by Uterine Artery Occlusion: Do They Share a Common Biology?

When the uterine arteries are bilaterally occluded, either by uterine artery embolization or by laparoscopic obstruction, women with myomas experience symptomatic relief. After the uterine arteries are occluded, most blood stops flowing in myometrial arteries and veins, and the uterus becomes ischemic. It is postulated that myomas are killed by the same process that kills trophoblasts: transient uterine ischemia. When the uterine arteries are bilaterally occluded, either by uterine artery embolization (UAE) or by laparoscopic obstruction, women with myomas experience symptomatic relief. After the uterine arteries are occluded, most blood stops flowing in myometrial arteries and veins, and the uterus becomes ischemic. Over time, stagnant blood in these arteries and veins clots. Then, tiny collateral arteries in the broad ligament (including communicating arteries from the ovarian arteries) open, causing clot within myometrium to lyse and the uterus to reperfuse. Myomas, however, do not survive this period of ischemia. This is unique organ response to clot formation and ischemia. What allows the uterus to survive a relatively long period of ischemia while myomas perish? Childbirth appears to be the predicate biology. Following placental separation, the uteroplacental arteries and the draining veins of the placenta are torn apart at their bases in the junctional zone of the myometrium and bleed directly into the uterine cavity. Left unchecked, every woman would bleed to death in less than 10 minutes after placental delivery. Most women do not bleed to death because vessels in the uterus clot after placental delivery. During pregnancy, clotting and lytic factors in blood increase many fold. Following delivery, uterine contractions continue, intermittently, periodically slowing the velocity of flowing blood through myometrium. The combination of slowed blood flow, elevated clotting proteins, and torn placental vessels (known as Virchow's triad) causes blood in myometrial arteries and veins to clot. Fibrinolytic enzymes later lyse clot in arteries and veins not associated with placenta perfusion, and the uterus is reperfused. Remnant placental tissue - primarily uteroplacental arteries and veins - does not survive this period of ischemia. Placental tissue dies and over weeks is sloughed into the uterine cavity. At the same time, residual endometrial tissue grows under the sloughing placental tissue thus re-establishing the endometrial lining. It is postulated that myomas are killed by the same process that kills trophoblasts - transient uterine ischemia.

Nucleated red blood cells in human fetal scalp capillary blood samples: a feasibility study

OBJECTIVE

Elevated umbilical cord nucleated red blood cell (NRBC) counts have been suggested as a predictor of adverse perinatal outcome. We sought to evaluate the feasibility of obtaining fetal scalp capillary blood NRBC counts during labor and to assess their correlation with umbilical cord NRBC counts.

METHODS

Fetal scalp capillary blood specimens were prospectively collected in laboring patients who underwent scalp sampling because of the presence of an abnormal fetal heart rate pattern. Matched umbilical cord blood samples were collected immediately after birth. Outcome measures were the feasibility of obtaining fetal scalp NRBC counts and their correlation with umbilical cord NRBC counts.

RESULTS

Thirteen term singleton pregnancies formed the study population. In four patients, fetal scalp capillary blood sampling was performed twice. Of the attempts to evaluate fetal scalp capillary samples for NRBC counts, 16 out of 17 (94.1%) were successful. The mean fetal scalp capillary blood NRBC count per 100 white blood cells was 12.6 +/- 7.6 (+/- SD). Umbilical cord mixed, venous and arterial NRBC counts were 15.5 +/- 8.8, 13.4 +/- 10.7 and 12.6 +/- 10.7, with p = 0.09, p = 0.59 and p = 0.68, respectively, when compared to the corresponding scalp sample. The Spearman rank correlation between fetal scalp capillary samples and umbilical cord mixed, venous and arterial NRBC counts were r = 0.86, r = 0.92 and r = 0.95, respectively, with all p values < 0.001.

CONCLUSION

Previous studies have established the clinical utility of umbilical cord NRBC counts. Our study demonstrated that it was possible to obtain NRBC counts from a fetal scalp capillary sample and that these counts correlated highly with umbilical cord NRBC counts. Future studies are needed to evaluate fetal scalp NRBC counts as a predictor of perinatal outcome.

The effects of epidural analgesia and uterine contractions on fetal oxygen saturation during the first stage of labour

The aim of this study was to investigate the effects of (1) maternal epidural analgesia and (2) uterine contractions on fetal oxygen saturation. After informed consent 18 women were included in our prospective, non-blinded, observational study. After 30 min of monitoring fetal oxygen saturation and uterine contractions, all the parturients, at cervical dilatation >/= 3 cm, received epidural analgesia for labour: a Pajunk epidural catheter was passed through a 17-gauge Tuohy needle and left in the lumbar epidural space (insertion level L3-4 or L2-3). Sufentanil 10 microg and 0.1% ropivacaine 15 mL were injected into the epidural catheter. A second and third 15-mL epidural dose of 0.1% ropivacaine were administered on patient demand. Fetal oxygen saturation was unaffected by epidural analgesia and there was no change in fetal SpO(2)following an uncomplicated epidural top-up. SpO(2)values (%) 30 s before, during and after contraction were 47.6 +/- 2.4, 52.5 +/- 5.3 and 42.9 +/- 7.2 respectively. These changes were significant. A contraction appeared to inject a bolus of oxygenated blood into the fetus, causing an initial increase in fetal oxygenation followed by a decline. The lowest SpO(2)values observed occurred 120 s after the start of contractions.