History of blood pressure measurement in newborns and infants.

The development of methods for measuring blood pressure (BP) in newborns and small children has a rich history. Methods for BP measuring in adults had to be adapted to this age group. For measuring BP in direct invasive way, a suitable approach had to be found to access the arterial circulation through the umbilical and later radialis artery. Currently, results obtained from direct invasive BP measurement are considered the "gold standard". The development of non-invasive methods for BP measuring in newborns and children began with the use of von Basch's sphygmomanometer (1880). In 1899, Gustav Gärtner constructed the device, which was the basis for the flush method. After the discovery of the palpation and auscultation methods, these methods were also used for BP measurement in newborns and children, however, the BP values obtained in these ways were typically underestimated using excessively wide cuffs. From the auscultation method, methods utilizing ultrasound and infrasound to detect arterial wall movement and blood flow were later developed. The oscillometric method for BP measurement was introduced by E. J. Marey so early as in 1876. In 1912, P. Balard used the oscillometric technique to measure blood pressure in a large group of newborns. Through different types of oscillometers using various methods for detecting vascular oscillations (such as xylol method, impedance and volume plethysmography, etc.), the development has continued to assessment of vascular oscillations by modern sensor technology and software. For continuous non-invasive blood pressure measurement, the volume-clamp method, first described by Jan Penáz in 1968, was developed. After modification for use in newborns, application of the cuff to the wrist instead of the finger, it is primarily used in clinical physiological studies to evaluate beat-to-beat BP and heart rate pressure variability, such as in the determination of the baroreflex sensitivity.

Mechanisms of Cardiovascular Changes of Phototherapy in Newborns with Hyperbilirubinemia.

During phototherapy of jaundiced newborns, vasodilation occurs in the skin circulation compensated by vasoconstriction in the renal and mesenteric circulation. Furthermore, there is a slight decrease in cardiac systolic volume, and blood pressure, as well as an increase in heart rate and discrete changes in the heart rate variability (HRV). The primary change during phototherapy is the skin vasodilation mediated by multiple mechanisms: 1) Passive vasodilation induced by direct skin heating effect of the body surface and subcutaneous blood vessels, modified by myogenic autoregulation. 2) Active vasodilation mediated via the mechanism provided by axon reflexes through nerve C-fibers and humoral mechanism via nitric oxide (NO) and endothelin 1 (ET-1). During and after phototherapy is a rise in the NO:ET-1 ratio. 3) Regulation of the skin circulation through the sympathetic nerves is unique, but their role in skin vasodilation during phototherapy was not studied. 4) Special mechanism is a photorelaxation independent of the skin heating. Melanopsin (opsin 4) - is thought to play a major role in systemic vascular photorelaxation. Signalling cascade of the photorelaxation is specific, independent of endothelium and NO. The increased skin blood flow during phototherapy is enabled by the restriction of blood flow in the renal and mesenteric circulation. An increase in heart rate indicates activation of the sympathetic system as is seen in the measures of the HRV. High-pressure, as well as low-pressure baroreflexes, may play important role in these adaptation responses. The integrated complex and specific mechanism responsible for the hemodynamic changes during phototherapy confirm adequate and functioning regulation of the neonatal cardiovascular system, including baroreflexes.

Cardiovascular changes during phototherapy in newborns.

Phototherapy is the most effective non-invasive method of neonatal hyperbilirubinemia treatment. Application of this method can be associated with side effects including changes in the cardiovascular system. During phototherapy, the primary effects in the cardiovascular system include cutaneous vasodilation leading to skin hyperperfusion and subsequent redistribution of blood. The increased blood flow through the skin is associated with increased transepidermal water loss. Further effects include an increase in cerebral blood flow. Redistribution of blood to the cutaneous bed is compensated by hypoperfusion in the splanchnic area (mostly postprandial) and a significant reduction of the renal blood flow. Regarding closure/reopening of the ductus arteriosus, the results suggest that that phototherapy does not affect ductal patency. During phototherapy the cardiac output can be slightly reduced due to a decreased stroke volume, especially in preterm newborns. Systemic blood pressure is decreased and heart rate is elevated in both preterm and term newborns during phototherapy. The heart rate variability is slightly reduced. Symbolic dynamics analysis of the short-term HRV showed that during phototherapy the activity of the ANS regulating the heart rate is shifted towards the dominancy of the sympathetic activity. The responses in the cardiovascular system of premature/mature newborns without other pathology confirm a well physiologically functioning control of this system, even under specific conditions of phototherapy.

Baroreflex sensitivity and blood pressure in premature infants - dependence on gestational age, postnatal age and sex.

To characterize the differences in baroreflex sensitivity (BRS), blood pressure (BP), heart rate (HR) and respiration rate (RR) in preterm infants with a similar postconceptional age reached by various combinations of gestational and postnatal ages. To detect potential sex differences in assessed cardiovascular parameters. The study included 49 children (24 boys and 25 girls), postconceptional age 34.6+/-1.9 weeks. Two subgroups of infants were selected with the similar postconceptional age (PcA) and current weight, but differing in gestational (GA) and postnatal (PnA) ages, as well as two matched subgroups of boys and girls. Blood pressure (BP) was recorded continuously using Portapres device (FMS). A stationary segment of 250 beat-to-beat BP values was analyzed for each child. Baroreflex sensitivity (BRS) was calculated by cross-correlation sequence method. Despite the same PcA age and current weight, children with longer GA had higher BRS, diastolic and mean BP than children with shorter GA and longer PnA age. Postconceptional age in preterm infants is a parameter of maturation better predicting baroreflex sensitivity and blood pressure values compared to postnatal age. Sex related differences in BRS, BP, HR and RR were not found in our group of preterm infants.

Investigation of association between genetic polymorphisms of MMP2, MMP8, MMP9 and TIMP2 and development of varicose veins in the Slovak Population - pilot study.

Matrix metalloproteinases (MMPs) are a family of zinc-dependent metalloendopeptidases that degrades extracellular matrix (ECM) components. MMPs are associated with venous wall remodelling, proliferation, migration, phenotypic and functional transformation of vascular smooth muscle cells and ECM organization under the physiological and pathophysiological conditions. We investigated possible association of genetic promoter polymorphisms of MMP2 (rs243866), MMP8 (rs11225395), MMP9 (rs3918242) and TIMP2 (rs8179090) to varicose veins development in the Slovak population. Genomic DNA from 276 Slovak individuals (138 cases, 138 controls) was genotyped for selected SNPs (rs243866, rs11225395, rs3918242 and rs8179090) using the PCR-RFLP analysis. The data were analysed by chi-squared (chi2) test, logistic regression, and Mann-Whitney test. The risk of varicose veins development was evaluated in dominant, codominant and recessive genetic models. The statistical evaluation of selected polymorphisms in patients in all three genetic models has not shown a significant risk of varicose veins development. Our study has not shown the association between selected polymorphisms and increased risk of varicose veins development in Slovak population. More evidence with broaden sample size is needed.

Heart rate variability in newborns.

Heart rate (HR) and heart rate variability (HRV) in newborns is influenced by genetic determinants, gestational and postnatal age, and other variables. Premature infants have a reduced HRV. In neonatal HRV evaluated by spectral analysis, a dominant activity can be found in low frequency (LF) band (combined parasympathetic and sympathetic component). During the first postnatal days the activity in the high frequency (HF) band (parasympathetic component) rises, together with an increase in LF band and total HRV. Hypotrophy in newborn can cause less mature autonomic cardiac control with a higher contribution of sympathetic activity to HRV as demonstrated by sequence plot analysis. During quiet sleep (QS) in newborns HF oscillations increase - a phenomenon less expressed or missing in premature infants. In active sleep (AS), HRV is enhanced in contrast to reduced activity in HF band due to the rise of spectral activity in LF band. Comparison of the HR and HRV in newborns born by physiological vaginal delivery, without (VD) and with epidural anesthesia (EDA) and via sectio cesarea (SC) showed no significant differences in HR and in HRV time domain parameters. Analysis in the frequency domain revealed, that the lowest sympathetic activity in chronotropic cardiac chronotropic regulation is in the VD group. Different neonatal pathological states can be associated with a reduction of HRV and an improvement in the health conditions is followed by changes in HRV what can be use as a possible prognostic marker. Examination of heart rate variability in neonatology can provide information on the maturity of the cardiac chronotropic regulation in early postnatal life, on postnatal adaptation and in pathological conditions about the potential dysregulation of cardiac function in newborns, especially in preterm infants.

Impact of early aggressive nutrition on retinal development in premature infants.

The normal retinal development is interrupted by preterm birth and a retinopathy of prematurity (ROP) may develop as its consequence. ROP is characterized by aberrant vessel formation in the retina as a response to multiple risk factors influencing the process of retinal angiogenesis. Insulin-like growth factor I (IGF-1) and vascular endothelial growth factor (VEGF) play an important role in the process of normal retinal vascularization. Insufficient nutrition during the first 4 postnatal weeks results in low serum levels of IGF-1, which is essential for correct retinal vessels formation, ensuring survival of the newly formed endothelial cells. Low IGF-1 level results in stop of angiogenesis in the retina, leaving it avascular and prompting the onset of ROP. Keeping the newborns in a positive energetic balance by providing enough nutrients and energy has a beneficial impact on their growth, neurodevelopment and decreased incidence of ROP. The best way to achieve this is the early parenteral nutrition with the high content of nutrients combined with early enteral feeding by the own mother´s breast milk. Multiple studies confirmed the safety and efficacy of early aggressive nutrition but information about its long-term effects on the metabolism, growth and development is still needed.

Baroreflex sensitivity in premature infants - relation to the parameters characterizing intrauterine and postnatal condition.

At present, there are insufficient information about baroreflex sensitivity (BRS) and factors that determine BRS in premature newborns. The objective of this study was to determine the relationship between BRS and the characteristics that reflecting the intrauterine development (gestational age and birth weight), as well as postnatal development (postconception age and the actual weight of the child at the time of measurement). We examined 57 premature infants, who were divided into groups according to gestational age and postconception age as well as birth weight, and weight at the time of measurement. Continuous and noninvasive registration of peripheral blood pressure (BP) was performed in every child within 2-5 min under standard conditions using a Portapres (FMS) device. The results showed a close correlation of baroreflex sensitivity, heart rate and respiratory rate with gestational age, postconception age, birth weight and actual weight at the time of measurement premature newborns. An increase in the characteristics (ages and weights) resulted in increased BRS and diastolic arterial pressure (DAP), and in decreased heart and respiratory rates. Baroreflex sensitivity in the first week was in the group of very premature newborns the lowest (4.11 ms/mmHg) and in the light premature newborns was almost double (8.12 ms/mmHg). BRS increases gradually in relation to postnatal (chronological) and to postconception age as well as to birth and actual weight. The multifactor analysis of BRS identified birth weight and postconception age as the best BRS predictors. The two independent variables together explained 40 % of interindividual BRS variability.

Associations of CYP1A2 Polymorphisms with the Risk Haplotypes in Lung Cancer in the Slovak Population.

Phase I enzymes, including cytochrome P450, family 1, subfamily A, and polypeptide 2 (CYP1A2), are involved in the activation of carcinogens to reactive intermediates that are capable of binding covalently to DNA to form DNA adducts, potentially initiating the carcinogenic process. The aim of present study was to investigate the association of CYP1A2 gene polymorphisms and haplotypes with lung cancer risk. A case-control study was carried out on 105 lung cancer patients and 189 controls. To investigate three CYP1A2 polymorphisms: rs2472299, rs2470890, rs11072508 we used a high resolution melting analysis. We found significant allele associations (rs2470890 and rs2422299) with lung cancer risk. We searched for meaningful associations for all variants in the dominant, recessive, and additive genetic models. Genotype associations in the recessive model were of marginal significance for the same single nucleotide polymorphisms. A haplotype analysis included five variants with the frequency higher than 1 %. The haplotype "acc", present with the highest frequency, was associated with increased lung cancer risk (38.7 % vs. 31.5 %; OR 1.38; 95 %CI 0.95-2.01). On the contrary, rare haplotype "gtc" was significantly associated with decreased lung cancer risk in the Slovak population. In conclusion, the present study identified the risk alleles and haploid genotype associations of the CYP1A2 gene in lung cancer.

Diagnostic significance of a mild decrease of baroreflex sensitivity with respect to heart rate in type 1 diabetes mellitus.

Decreased baroreflex sensitivity is an early sign of autonomic dysfunction in patients with type-1 diabetes mellitus. We evaluated the repeatability of a mild baroreflex sensitivity decrease in diabetics with respect to their heart rate. Finger blood pressure was continuously recorded in 14 young diabetics without clinical signs of autonomic dysfunction and in 14 age-matched controls for 42 min. The recordings were divided into 3-min segments, and the mean inter-beat interval (IBI), baroreflex sensitivity in ms/mm Hg (BRS) and mHz/mm Hg (BRSf) were determined in each segment. These values fluctuated in each subject within 42 min and therefore coefficients of repeatability were calculated for all subjects. Diabetics compared with controls had a decreased mean BRS (p=0.05), a tendency to a shortened IBI (p=0.08), and a decreased BRSf (p=0.17). IBI correlated with BRS in diabetics (p=0.03); this correlation was at p=0.12 in the controls. BRSf was IBI independent (controls: p=0.81, diabetics: p=0.29). We conclude that BRS is partially dependent on mean IBI. Thus, BRS reflects not only an impairment of the quick baroreflex responses of IBI to blood pressure changes, but also a change of the tonic sympathetic and parasympathetic heart rate control. This is of significance during mild changes of BRS. Therefore, an examination of the BRSf index is highly recommended, because this examination improves the diagnostic value of the measurement, particularly in cases of early signs of autonomic dysfunction.

Spectral peak frequency in low-frequency band in cross spectra of blood pressure and heart rate fluctuations in young type 1 diabetic patients.

In this study we tested whether joint evaluation of the frequency (f(cs)) at which maxima of power in the cross-spectra between the variability in systolic blood pressure and inter-beat intervals in the range of 0.06-0.12 Hz occur together with the quantification of baroreflex sensitivity (BRS) may improve early detection of autonomic dysfunction in type 1 diabetes mellitus (T1DM). We measured 14 T1DM patients (age 20.3-24.2 years, DM duration 10.4-14.2 years, without any signs of autonomic neuropathy) and 14 age-matched controls (Co). Finger arterial blood pressure was continuously recorded by Finapres for one hour. BRS and f(cs) were determined by the spectral method. Receiver-operating curves (ROC) were calculated for f(cs), BRS, and a combination of both factors determined as F(z)=1/(1+exp(-z)), z=3.09-0.013*BRS-0.027*f(cs). T1DM had significantly lower f(cs) than Co (T1DM: 88.8+/-6.7 vs. Co: 93.7+/-3.8 mHz; p<0.05), and a tendency towards lower BRS compared to Co (T1DM: 10.3+/-4.4 vs. Co: 14.6+/-7.1 ms/mm Hg; p=0.06). The ROC for Fz showed the highest sensitivity and specificity (71.4 % and 71.4 %) in comparison with BRS (64.3 % and 71.4 %) or f(cs) (64.3 % and 64.3 %). The presented method of evaluation of BRS and f(cs) forming an integrated factor Fz could provide further improvement in the risk stratification of diabetic patients.

The effect of orthostasis on recurrence quantification analysis of heart rate and blood pressure dynamics.

The purpose of this paper is to investigate the effect of orthostatic challenge on recurrence plot based complexity measures of heart rate and blood pressure variability (HRV and BPV). HRV and BPV complexities were assessed in 28 healthy subjects over 15 min in the supine and standing positions. The complexity of HRV and BPV was assessed based on recurrence quantification analysis. HRV complexity was reduced along with the HRV magnitude after changing from the supine to the standing position. In contrast, the BPV magnitude increased and BPV complexity decreased upon standing. Recurrence quantification analysis (RQA) of HRV and BPV is sensitive to orthostatic challenge and might therefore be suited to assess changes in autonomic neural outflow to the cardiovascular system.

Respiratory sinus arrhythmia is reduced in adolescent major depressive disorder.

OBJECTIVE: Although the emotion regulatory difficulties in patients with major depressive disorder (MDD) are predicted to associate with impaired cardiovascular autonomic regulation, the changes of cardiac vagal regulation MDD are incompletely understood. The aim of the study was to evaluate the respiratory sinus arrhythmia (as an index of cardiac vagal regulation) using the spectral analysis in high frequency band of the heart rate variability and the indices of deep breathing test in adolescent patients with major depressive disorder. MATERIAL AND METHOD: Twenty-eight adolescent girls were examined - 14 patients with major depressive disorder without pharmacological treatment (average age: 16.4 +/- 0.2 yr) and 14 healthy probands (control group) matched for age and gender. The respiratory sinus arrhythmia was evaluated using the spectral analysis in high frequency band of the heart rate variability (HF-HRV) and the parameters of deep breathing test (I-E, I/E). In addition, mean R-R interval was calculated. RESULTS: The adolescent patients with MDD has significantly reduced spectral activity in the HF-HRV and lower I/E, I-E parameters compared to marched health subjects (P<0.05). CONCLUSIONS: We conclude that the adolescents girls with MDD have reduced respiratory sinus arrhythmia indicating cardiac vagal dysregulation. Since impaired cardiac vagal regulation is associated with increased risk of cardiovascular morbidity, this finding underscores the importance of impaired autonomic neuro-cardiac integrity already in adolescents with major depressive disorder without pharmacological treatment.

Reduced short-term complexity of heart rate and blood pressure dynamics in patients with diabetes mellitus type 1: multiscale entropy analysis.

Multiscale entropy (MSE) analysis provides information about complexity on various time scales. The aim of this study was to test whether MSE is able to detect autonomic dysregulation in young patients with diabetes mellitus (DM). We analyzed heart rate (HR) oscillations, systolic (SBP) and diastolic blood pressure (DBP) signals in 14 patients with DM type 1 and 14 age- and sex-matched healthy controls. SampEn values (scales 1-10) and linear measures were computed. HR: among the linear measures of heart rate variability significant differences between groups were only found for RMSSD (p = 0.043). MSE was significantly reduced on scales 2 and 3 in DM (p = 0.023 and 0.010, respectively). SBP and DBP: no significant differences were detected with linear measures. In contrast, MSE analysis revealed significantly lower SampEn values in DM on scale 3 (p = 0.039 for SBP; p = 0.015 for DBP). No significant correlations were found between MSE and linear measures. In conclusion, MSE analysis of HR, SBP and DBP oscillations is able to detect subtle abnormalities in cardiovascular control in young patients with DM and is independent of standard linear measures.

Cardio-respiratory interaction and autonomic dysfunction in obesity.

We aimed to test whether the evaluation of the cardio-respiratory interaction using the analysis of heart rate and blood pressure variabilities and respiratory maneuvers can reveal cardiovagal dysfunction in obese adolescents 12-18 years old. The spectral power in high frequency band of the heart rate variability (HRV) reflecting respiratory sinus arrhythmia was used as an index of the cardiac vagal control, and the spectral power in high frequency band of the blood pressure variability (BPV) as an indicator of mechanical effects of respiration. The deep breathing test and Valsalva maneuver were applied. The obese group had a reduction in spectral power in high frequency band of the HRV. Differences in high frequency band spectral power of the BPV between the obese and control groups were not found. The finding of lower respiratory sinus arrhythmia, indicating a cardiovagal dysfunction in obese adolescents, can provide important diagnostic information about early subclinical autonomic dysfunction in obesity.

Effects of hypovolemia on hypercapnic ventilatory response in experimental hyperthermia.

The present study was undertaken to evaluate the effects of hypercapnia on the cardiorespiratory control in normovolemic and hypovolemic rabbits during exogenous hyperthermia. Hypovolemia was induced by administration of furosemide, the body temperature (Tb) was gradually elevated to 42 degrees C by body surface heating. Subsequently, Tb was lowered back to the initial values by gradual cooling. Recordings were done at normothermia (TN=38 degrees C), during heating at 40 degrees C (TH1) and 42 degrees C (TH2), and in the course of Tb reverting toward the baseline values back at 40 degrees C (TC1), and finally after full return to the initial temperature value (TC2). The hypercapnic ventilatory response (HCVR) was estimated as the slope of minute volume (VE) on end-tidal CO2 (ETCO2) curves. We found that heating caused an increase in the VE slope in the normovolemic (NV), but not in hypovolemic (HV), rabbits. Between-group comparison revealed a significant increase in HCVR at TH2 and TC1 in NV vs. HV rabbits. Hypercapnia in hyperthermia (at TC2) was accompanied by a significant decrease in heart rate only in the hypovolemic group. Recovery of Tb was unaccompanied by appreciable changes in HCVR in either NV or HV groups. In the course of cooling, a decrease in heart rate during hypercapnic challenge was present in both group, in HV the drop was less prominent. We conclude that hypercapnia during heat stress in both normovolemic and hypovolemic rabbits is associated with altered cardiorespiratory responses. HCVR during exogenous hyperthermia is augmented in normovolemic, but not in hypovolemic, rabbits.

Cystic dysplasia of the rete testis. Case report.

Cystic dysplasia of the rete testis (CDRT) is a very rare cause of a paediatric scrotal mass often associated with renal and other genitourinary tract anomalies. These complex malformations are probably due to a developmental defect of the mesometanephric system during embryogenesis. A case of asymptomatic scrotal swelling in a 4-year-old boy is presented. Ultrasonography, showed a cystic lesion of the left testis associated with absence of the left kidney. Orchiectomy was performed because of extensive gonad involvement. Pathologic examination revealed multiple, anastomosing, irregular cystic spaces of varying sizes and shapes predominantly located in the region of the rete testis. The cysts had spread irregularly, displacing the testicular parenchyma, which was subsequently compressed under the tunica albuginea. Preoperative diagnosis of CDRT is easy if age, precise localisation, characteristic ultrasonographic features and other genitourinary malformations are considered. Other paediatric cystic lesions should be included in the differential diagnosis. It is possible to cure CDRT by orchiectomy or by conservative treatment. Nowadays the later option is preferred, but diagnosis of CDRT must be precisely established and followed by careful monitoring.

Surfactant lung lavage using asymmetric high-frequency jet ventilation followed by conventional ventilation in rabbits with meconium aspiration.

BACKGROUND: Severe impairment of lung functions in meconium aspiration syndrome (MAS) often needs the application of combined therapeutic approach. In our recent study, surfactant lung lavage during asymmetric high-frequency jet ventilation (HFJV) removed more meconium than surfactant lavage during conventional ventilation, however, after the lavage excessive CO2 elimination was observed during HFJV. OBJECTIVES: We hypothesized that the combination of asymmetric HFJV during surfactant lung lavage and conventional ventilation in the post-lavage period may be of benefit in a rabbit model of MAS. METHODS: Suspension of human meconium in saline (25 mg/ml, 4 ml/kg) was instilled into the tracheal tube of conventionally ventilated (frequency, f, 30/min, inspiration time, Ti, 50%) anesthetized rabbits to cause a respiratory failure. Animals were then lavaged (10 ml/kg in 3 portions) with diluted surfactant (Curosurf, 100 mg of phospholipids/ml) or saline during asymmetric HFJV (f, 300/min, Ti, 70%). After the lavage, animals were ventilated conventionally (f, 30/min, Ti, 50%) for next 1 hour. RESULTS: Surfactant lung lavage during asymmetric HFJV removed more meconium pigments and solids than saline with HFJV (p < 0.05 or p < 0.01, respectively). Moreover, application of asymmetric HFJV facilitated the lavage fluid removal in both groups. In the post-lavage period, improved oxygenation, lung compliance, right-to-left pulmonary shunts, and reduced ventilatory requirements were found in the surfactant group (p < 0.05), while pCO2 was kept in the normal range. CONCLUSIONS: Surfactant lung lavage by asymmetric HFJV followed by conventional ventilation is advantageous combination in rabbits with MAS and may be tested in neonatal MAS (Tab. 2, Fig. 2, Ref. 12).

Effects of acute normovolemic haemodilution on cardiorespiratory changes in hyperthermia and its physical treatment.

As only one experimental study examining the effects of haemodilution on circulatory responses to hyperthermia has so far been published and there is no information on respiratory responses to hyperthermia during haemodilution or anaemia, this paper studied the effects of acute normovolemic haemodilution on cardiorespiratory changes during 42 degrees C hyperthermia and its recovery by body surface cooling in 16 anaesthetized adult rabbits. The animals were divided into two groups: haemodiluted group (Hct = 18.6 +/- 0.4%) and control group (Hct = 41.1 +/- 0.9%). In the haemodiluted group, acute normovolemic haemodilution was induced by 60% replacement of total blood volume with dextran. Haemodilution produced significant increases in minute volume (V(E), p < 0.02), heart rate (HR, p < 0.02) and central venous pressure (CVP, p < 0.02), but there was no significant change in mean arterial pressure (MAP). Hyperthermia caused significant increases in V(E) and HR in both the groups; however, V(E) and HR values were significantly higher in the haemodiluted group compared to the controls. CVP decreased (p < 0.05) during 42 degrees C hyperthermia only in the controls in the panting phase. MAP did not significantly change during over-heating in controls, but it significantly (p < 0.02) rose in the haemodiluted group. In the recovery phase, cooling led to significant decreases in HR and MAP in both the groups and to further increases in V(E) (p < 0.05) in controls, whereas V(E) decreased in the haemodiluted animals. There were found no significant cardiorespiratory differences between the two groups during cooling. Hyperthermia was accompanied by the higher values of minute volume and heart rate in the haemodiluted animals, indicating a greater activation of the respiratory and cardiovascular systems, which could result in diminished functional cardiorespiratory reserve and a higher risk of respiratory and circulatory failures in haemodiluted/anaemic animals during hyperthermia. In the phase of recovery of the body temperature there were no significant cardiorespiratory differences found between the two groups.

Lung lavage using high-frequency jet ventilation in rabbits with meconium aspiration.

AIM: To determine the efficacy of the expulsion effect of high-frequency jet ventilation (HFJV) on meconium clearance from the airways in comparison with conventional suctioning in adult rabbits with meconium aspiration. METHODS: Experiments were carried out on tracheotomized, anaesthetized and paralysed adult rabbits. A suspension of human meconium in saline (25 mg ml(-1), 4 ml kg(-1)) was instilled into the tracheal cannula. When respiratory failure developed, saline lavage (10 ml kg(-1) in 3 portions) was performed during conventional ventilation or by means of the inpulsion and expulsion regime of HFJV. Animals were further ventilated for 2 h with either conventional ventilation or HFJV. RESULTS: There was no significant difference between groups in the amount of meconium recovered by lavage. Compared to conventional ventilation, the application of HFJV enhanced the elimination of carbon dioxide, increased lung compliance and diminished right-to-left shunts after 30 min of ventilatory treatment. Oxygenation also improved during HFJV, although this was not a consistent finding during the ventilation period. CONCLUSION: HFJV improved gas exchange, lung compliance and reduced right-to-left pulmonary shunts, but saline lung lavage by HFJV was not found to be more efficient than lavage during conventional ventilation in rabbits with meconium aspiration.