The influence of different electrode temperatures on the recorded transcutaneous Po2 level.

The technique of transcutaneous monitoring of oxygen partial pressure (PtcO2), first described in 1969, provided a new clinical possibility for continuous and noninvasive surveillance of changes in the oxygenation of the organism. To obtain optimal arterialization of the skin and thus a relieable recording, the electrodes used have been supplied with microheating elements. The electrode temperature used implies the risk of producing burns; this is especially true when the measurements are performed in patients with decreased skin circulation or in immature children with a thin and vulnerable skin. Thus, a careful choice of the electrode temperature is important in PtcO2 recording; a higher temperature is desirable for obtaining adequate arterialization, whereas a lower temperature is preferred for reducing the risk of burns. The electrode temperatures described for PtcO2 measurements range from 42--45 C. A systematic study with the Radiometer TCM 1 equipment showed that changing the electrode temperature influences the OtcO2 in a systematic way within the temperature range 43.0--45.0 C. The study also showed that simultaneous measurements obtained from two electrodes with different temperatures showed a highly parallel course and a comparable oscillating pattern within this temperature range. The results of the present study suggest that an electrode temperature of 44.5 C may be the most appropriate for this equipment in clinical applications with newborns.

Acute effects of maternal smoking on fetal breathing and movements.

The acute effects of cigarette smoking on fetal breathing movements and fetal movements were determined with a real-time ultrasound system in 10 healthy habitually smoking women in late gestation. The study was carried out for 1 hour before and 1 hour after the woman smoked a single cigarette. The maternal blood glucose concentration was maintained at a raised postprandial level through the study. After smoking, a significant increase in the rate of fetal breathing movements (P less than .05) appeared together with a reduction in the short time variability of the breath-to-breath intervals (P less than .05). The number of epochs without fetal breathing movements or fetal trunk and limb movements increased after smoking (P less than .05), indicating a change in the spacing of these fetal activities. The increased breathing rate and number of apneic epochs were both correlated to maternal nicotine levels. These observations suggest an acute influence on the fetal behavioral state of maternal smoking.

Intrathecal CGRP(8-37) results in a bilateral increase in hindpaw withdrawal latency in rats with a unilateral thermal injury.

The present study was performed to explore the effects of intrathecal administration of calcitonin gene-related peptide8-37 (CGRP(8-37)) on the hindpaw withdrawal latency (HWL) to pressure in rats with one thermally injured hindpaw. Furthermore, the interaction of CGRP(8-37)and naloxone was studied. Thermal injury was performed by dipping the left paw into 60 degrees C for 20 s. This induced a significant increase in the volume of the left hindpaw (P<0.001) and significant bilateral decreases of the latency of hindpaw withdrawal response to mechanical stimulation (Left: P<0.001; right: P<0.05). Intrathecal administration of 10, 20 and 40 nmol of CGRP(8-37), but not of 1 or 5 nmol, induced a significant bilateral increase in HWLs (P<0.001). The effect of CGRP(8-37) was partly reversed by intrathecal injection of naloxone at a dose of 32 and 64 microg respectively. Using radioimmunoassay, we found a significant bilateral increase in the concentration of CGRP-like immunoreactivity in the perfusate of both hindpaws 24 h after unilateral thermal injury (left: P< 0.001; right: P< 0.05). There was also an increase in the amount of CGRP-like immunoreactivity in the cerebrospinal fluid (P< 0.001), but not in plasma. The results indicate that CGRP plays a role in the transmission of nociceptive information in the spinal cord of thermally injured rats. Furthermore, our findings suggest that opioids can modulate CGRP-related effects in the spinal cord.

Opioids modulate the calcitonin gene-related peptide8-37-mediated hindpaw withdrawal latency increase in thermally injured rats.

The present study was performed to explore the modulatory potential of different endogenous opioid systems on transmission of presumed nociceptive information at the spinal cord level in thermally injured rats. Thermal injury was performed by dipping the left paw into water 60 degrees C for 20 s. This induced a significant bilateral decrease in hindpaw withdrawal latency HWL to pressure. Intrathecal administration of 10 nmol of CGRP8-37 induced a significant bilateral increase in HWL in the thermally injured group and in the intact controls. The effect of different opioid receptor antagonists on the increased latency to withdrawal response induced by intrathecal injection of 10 nmol of CGRP8-37 was explored in the thermally injured rats. The effect was reversed by intrathecal injection of 40 and 80 nmol of: b-funaltrexamine (mu opioid receptor antagonist) and naltrindole (delta opioid receptor antagonist), but not by norbinaltorphimine (kappa opioid receptor antagonist). The results of the present study show that intrathecal CGRP8-37 increases hindpaw withdrawal latency in thermally injured rats, an effect reduced by a mu as well as by a delta opioid receptor antagonist.

Site tenacity and nomadism in Tengmalm's owl (Aegolius funereus (L.)) in relation to cyclic food production.

In northern Sweden breeding males of Tengmalm's owls (Aegolius funereus (L.)) were site tenacious during and between the peaks of the vole (staple food) cycles, but females only during the peaks. Most of these adults shifted nest boxes between successive years. They selected nest boxes randomly in a radius of 3 km. Juveniles, in contrast to site tenacious adults, dispersed outside their natal area. The females moved longer than the males prior to their first breeding. Five adult females were found to be nomadic. One of these nomadic females previously bred site tenaciously as long as food was abundant. Juveniles and adult males were not found to be nomadic. Emigration of adult females and juveniles occurred most frequently when vole populations declined. The breeding population increased sharply and received immigrants suggesting that nomadism may be essential in the population dynamics. Site tenacity and nomadism are discussed in terms of costbenefit to males and females, respectively. Emphasis is on the main functional roles of males (feeding femle and young) and females (incubation).

Cycles in voles and small game in relation to variations in plant production indices in Northern Sweden.

Population dynamics for voles (Cricetidae), Tengmalm's owl (Aegolius funereus (L.)), red fox (Vulpes vulpes (L.)) willow grouse (Lagopus lagopus (L.)), black grouse (Lyrurus tetrix (L.)), capercaillie (Tetrao urogallus L.), hazel hen (Tetrastes bonasia (L.)), mountain hare (Lepus timidus L.) and tularemia (Francisella tularensis (McCoy & Chapin)) and game bird recruitment were studied by index methods in northern Sweden. In addition contemporary temperature records and spruce (Picea abies (L.) Karst.) and pine (Pinus silvestris L.) cone crops (as indices for plant production) and the occurrence of forest damage, caused by voles eating bark, were studied.During 1970-80 two synchronous 4-year cycles were observed for voles, predators (Tengmalm's owl and red fox) and their alternative prey species (grouse and mountain hare). In grouse the change of numbers was correlated with that of recruitment. Autumn vole numbers peaked about a year before the other species and extensive forest damage occurred at winter peak densities of voles. These population fluctuations are consistent with a predator-prey model for their regulation. In short the model suggests that vole-food plant interactions trigger the cycle of voles, that voles generate the cycle of predators and that these in turn synchronize alternative prey populations to the others at vole declines.For voles, grouse and red fox the amplitude was higher in the first cycle compared to the second one whilst the opposite was true for the mountain hare. Although temperature and cone crops showed large interannual variations they still implied that herbivore food conditions were 'better' during the former cycle. Hence, the reduction of the amplitude of the vole cycle may be explained by inter-cyclic differences in plant food conditions, implying food shortage (as indicated by bark-eating) at different population levels. The similar decrease of grouse and red fox populations may also be explained by deteriorated food conditions and/or for the fox by an outbreak of sarcoptic mange (Sarcoptes scabiae var. vulpes). The increased amplitude of the mountain hare cycle was part of a long-term rise in numbers after a tularemia epidemic in 1967. This is interpreted as a recovery, probably towards the generally higher pre-epidemic population level.

Inhibitory effects of tachykinin receptor antagonists on thermally induced inflammatory reactions in a rat model.

Recent studies have proposed that activation of the sensory nervous system after thermal injury induces the release of vasoactive neuropeptides, including tachykinins which contribute to the local inflammatory reaction as well as to the nociceptive transmission at the spinal cord level. Effects of the tachykinins substance P and neurokinin A are mediated by the neurokinin 1 and 2 (NK1, NK2) receptors. The aim of the present study was to investigate the modulatory role of NK1 and NK2 antagonists on edema formation, and on hindpaw withdrawal latency to experimentally asses nociception. Thermal injury was inflicted on the anaesthetized rat by dipping the right hindpaw into hot water at 60 degrees C for 20 s. The amount of edema formation was calculated by measuring the hindpaw volume with a plethysmograph before and during 420 min after scalding. In other studies scalding was inflicted under brief anesthesia, and hindpaw withdrawal latencies (HWL) to mechanical stimulation were recorded before injury and at 180 min after. The effect on edemic reactions of rats treated locally with NK1 and NK2 receptor antagonist were studied, as well as the effect of the same compounds on HWL after intrathecal injection. Scalding induced a progressive edema formation which was reduced significantly in rats treated with local injection of 100 nmol of NK1 and NK2 antagonists 45 min after the injury. The thermally induced inflammation was followed by significant decrease of the latency of hindpaw withdrawal response to mechanical stimulation. Intrathecal injection of 30 nmol of the same drugs 180 min after scalding was followed by significant increase in HWL. The results indicate that SP and NKA contribute to the inflammatory reactions after thermal injury and that the tachykinin receptor antagonists possess the ability to reduce both the local edemic reaction as well as the nociceptive transmission at the spinal cord level.

Contribution of the sensory and sympathetic nervous system to scalding-induced edema in the rat paw.

It has recently been hypothesized that both the sensory and sympathetic nervous system contribute to the inflammatory reaction. A scalding model was developed in anaesthetized rats to investigate the contribution of neuropeptides in heat-induced edema localized to the hindpaw. After immersing the paw in water at 60 degrees C for 10, 20, 30 and 60 s, edemic reactions were registered as change of paw volume in a plethysmograph and hindpaw perfusates collected to measure the content of neuropeptides by radioimmunoassay. A scalding period of 30 s induced the most prominent edemic reaction. There was a marked increase of the sensory neuropeptide neurokinin A and the sympathetic related transmitter neuropeptide Y in hindpaw perfusates after scalding. The effect of peripheral nerve ligation on edemic reaction and on the release of neuropeptides was investigated in rats scalded for 30 s at 60 degrees C. There was a significant decrease of edema formation in the scalded nerve ligated paw as compared with the scalded paw on the non-ligated side. Neurokinin A was not detected in nerve ligated rats before or after scalding, whereas mononeuropathic rats showed increased concentrations of neuropeptide Y. The present results indicate that the sensory as well as the sympathetic nervous system, possibly through the release of neuropeptides, may contribute to scald-induced edema.

pH measurement from the fetus during labor--a task for the midwife?

After theoretical education on the development of fetal acidosis and the fetal blood sampling technique, 12 midwives in a training program carried out or assisted in 40 fetal blood sampling procedures. Sampling was possible at a cervical dilatation of 1.5 cm. 11/12 midwives were successful in their first sampling attempt. The instrument used for analysis was an automated microprocessor device with a minimum sampling volume of 15 microliter of blood. There was a statistically highly significant correlation between the results obtained with the instrument tested and the reference device (r = 0.9; n = 36). 82% of the measurements fell within +/- 0.04 pH units of the reference device. With the instrument placed in the labor room, and using the current technique with very small blood samples, it is possible to obtain a fetal pH value within 10 minutes after the development of a pathological fetal heart rate pattern.

The effect of fibrin deposition on the sensitivity of the continuous monitoring pH electrode and on the recorded pH value: an in vitro study.

One of the problems concerning the continuous pH-monitoring technique is whether the relationship between pH measured by the electrode and pH in central and/or capillary fetal blood is constant. To test to what extent a fibrin clot deposited on the pH-electrode influenced the recorded value and the sensitivity of the electrode, the following in vitro study was performed. Fibrin was deposited on the pH-electrode by means of thromboplastin and fibrinogen, or by thromboplastin and whole blood. The deposition of a clot was verified by inspection of the electrode in a microscope. The time for stabilization of the recorded pH-value and the recorded pH-value was measured in standard calibration solutions before and after deposition of the fibrin clot and after decomposition of the fibrin clot by plasmin. FDP was measured in the decomposition solution. From the study it was obvious that the stabilization time of the electrode was considerably influenced by deposition of an "unphysiological" fibrin clot, less so if the clot was deposited by means of whole blood. The recorded pH-value was not influenced.

Continuous transcutaneous oxygen monitoring in fetal surveillance during labor.

Continuous transcutaneous oxygen (PtcO2) monitoring is a noninvasive technique for recording changes in central oxygenation. PtcO2 monitoring has been for some years a routine method in neonatal and adult intensive care. The technique is a potential tool in fetal surveillance during labor. Some recently published studies which have been critical of the use of PtcO2 monitoring in the delivery room reveal a lack of thorough understanding of the limitations of the technique. From the author's experience with the technique, it is obvious that, when the PtcO2 electrode is attached according to recommendations and when the monitoring situation fulfills certain criteria, PtcO2 reliably reflects changes in the fetal oxygenation during labor and may be used for the diagnosis of true hypoxemia. PtcO2 monitoring does not replace any other available routine monitoring for fetal surveillance, but when the technique is refined, it may become an additional means of diagnosing fetal jeopardy. As a research parameter, PtcO2 monitoring has already contributed to a more diversified understanding of the process of fetal asphyxia.

Transcutaneous oxygen monitoring from the fetus during labor: a study of the TcPO2 levels and comparison of two electrode application techniques.

The technique for transcutaneous oxygen (TcPO2) monitoring is now routine in neonatal intensive care. The method was presented earlier as a potential tool for fetal surveillance during labor. The current study reports on two techniques generally used for the application of the electrode to the fetus. The application of the electrode by a suction instrument does not influence the TcPO2 level recorded and the use of this technique is very simple. However, the main disadvantage of the suction instrument is that the electrode is easily detached. Application of the electrode by glue is technically a little more difficult but has the advantage of being much more efficient. If the criteria for a reliable recording presented in the study are fulfilled, the technique may be used as an additional parameter to diagnose true fetal hypoxemia.

The effect on responsivity of the PtcO2 electrode by an increased pressure on the electrode membrane.

At application of the electrode for continuous transcutaneous oxygen monitoring, a superatmospheric pressure may be produced between the skin and the electrode membrane. Such a pressure may change the electrode characteristics resulting in a slower reacting electrode. A superatmospheric pressure may also influence on the subepidermal capillaries and on the oxygen diffusion through the skin. The results in the current in vitro study show that an increase of the pressure between the electrode membrane and the skin results in a slower reacting electrode, only when the pressure also produces an increased diffusion distance from the capillaries to the electrode membrane. Thus, the PtcO2 electrode seems rather rough and different PtcO2 levels recorded among patients or in the same patient at two applications are not produced by the application procedure per se but by physiological differences in the skin at the electrode application site.

Transcutaneous oxygen measurement in adult intensive care.

Transcutaneous oxygen measurement (PtcO2-measurement) gives by a non-invasive technique continuous information about central PO2. The method has as yet been tested mainly on newborns, and systematic studies of the applicability of the method on adults are still few. The current systematic study reports on consecutive PtcO2 measurements in 15 patients, all with indwelling arterial catheters: 13 of the patients were artificially ventilated; 5 patients had normal body structure and normal skin circulation; 5 patients were obese and had normal skin circulation; and 5 patients were hypothermic with a normal heart frequency or slight bradycardia. The Radiometer equipment TCM1 was used. The electrode surface tempertaure was 45.0 degrees C (within +/- 0.2 degrees C). The oxygen concentration in the inspired air was altered several times for all patients, and arterial samples were drawn at a stable PtcO2 level. On average, seven samples were drawn from each patient. The correlation between PtcO2 and PaO2 was highly significant in 4/5 patients, in both the "obese patient" group and the "normal patient" group. In the "hypothermic patient" group, the correlation between PtcO2 and PaO2 was highly statistically significant in 2/5 patients. The regression line between PtcO2 and PaO2 was calculated for each patient, and a mean regression line was obtained for each group. It was found that the regression line in the "obese patient" group was displaced to the right and parallel to the regression line in the "normal patient" group, while the regression line in the "hypothermic patient" group was less sloping and showed a higher intercept. The PtcO2 monitoring technique reliably reflects changes in the central oxygenation of adult intensive care patients. In some patients with decreased skin circulation, the relationship between PtcO2 and PaO2 seemed to be constant for the same patient, yielding statistically sifnificant correlations. However, the study cannot determine whether this would be true in all clinical situations; the relationship betwee PtcO2 and PaO2 should therefore be checked frequently when measruements are performed in patients with decreased skin circulation. The author's experience with the PtcO2 monitoring method in patients near death has been consistent with the obvious fact that the reliability of the method decreases with decreased skin circulation.

Continuous transcutaneous carbon dioxide measurement from the fetal scalp during labor and during first minutes of extrauterine life.

An electrode for continuous transcutaneous carbon dioxide (tcPco2) monitoring was attached to the fetal scalp in 25 consecutive vaginal deliveries. In six patients the electrode fell off or was deliberately removed when the fetal head was on the pelvic floor, while eight patients were delivered with the electrode in situ, making it possible to study changes in the fetal carbon dioxide level when the fetus changed from placental to lung breathing. The mean recording time was 136 minutes (range 10-348). Fifteen patients were recorded until delivery and analysis of cord blood showed a statistically highly significant correlation between tcPco2 in both umbilical venous and arterial blood. The mean fetal tcPco2 during the late first stage of labor was 56 torr (range 40-75; n = 18). The post partum tcPco2 level in newborns was stable 20 minutes after delivery with a mean level of 51 torr (range 40-60). Fetuses with a normal fetal heart rate tracing showed a lower mean tcPco2 level than fetuses with fetal heart rate tracing abnormalities. The experience with the current technique indicates that both Apgar score and fetal heart rate tracing are rather crude methods to judge fetal blood gas status.

Perinatal mortality: changes in the diagnostic panorama 1974-1980.

During the period 1974-1980, all late abortions (greater than 19 completed gestational weeks) (LA), late fetal deaths (LFD) and early neonatal deaths (END) were surveyed in a continuous material of 17813 births with an ascertained gestational age established by early ultrasound fetometry. There was no maternal death during the period. The total perinatal mortality (PM) was 0.98% with an END rate of 0.51%. In about 45% of LFD no diagnosis was found. Intrapartum death was extremely rare as was END caused by asphyxia or infection. In END, death from immaturity constituted the major group in the beginning of the period, while after 1977 lethal malformations was the dominating diagnosis. There was a continuous decrease in Idiopathic Respiratory Distress Syndrome (IRDS) as a cause of END. The proportion of END in extremely premature children showed a constant decrease in the beginning of the period. No difference in sex was found in END except for lethal malformations where there was a significant male preponderance. As a consequence of a more active obstetrical care, some fetuses who would previously have been classified as LA were probably delivered liveborn, extremely premature and appeared as END. The question of where to set the limits for what should be included in PM is thus highly relevant.

Transcutaneous monitoring of PO2 in different skin areas in the neonate and in the scalp of the fetus during labor - methodological and physiological observations.

The reliability and physiological significance of continuous non-invasive PO2 recording by means of skin electrodes was studied by comparing simultaneous tracings from different skin areas in a series of 40 newborns with normal labor and birth. A new measuring equipment - the Radiometer prototype unit TPM 1 - was used. In addition, the applicability of the method to the fetus was tested in a primary series of 11 labor cases. Certain technical and physiological factors that can influence the tracings were identified.