Arterial Blood pH Research Articles

Quantitative analysis of acid-base balance in Bos indicus steers subjected to transportation of long duration.

There is a lack of information pertaining to the effects of transport stress on the acid-base physiology of ruminants. The effect of transportation and/or feed and water deprivation on acid-base balance was studied using 19 2-yr-old Bos indicus steers. The steers were allocated to one of three groups: 1) control, offered ad libitum access to feed and water (n = 8); 2) water and feed deprived, offered no feed or water for 60 h (n = 6); and 3) transported, offered no feed or water for 12 h, and then transported for 48 h (n = 5). Blood gases, electrolytes, lactate, total protein, albumin, anion gap, strong ion difference, and total weak acids were determined at the conclusion of transportation. Arterial blood pH did not differ among the experimental groups. Partial pressure of carbon dioxide (pCO2) was lower for the water and feed deprived (P = 0.023) group than for the control group. Plasma total protein, albumin and total weak acid concentrations were higher for the transported (P = 0.001, P = 0.03, P = 0.01) and water- and feed-deprived (P = 0.000, P = 0.003, P = 0.001) groups, respectively, compared with the control group. Transported animals had a lower plasma concentration of potassium (P = 0.026) compared with the control animals. This study demonstrates that although blood pH remains within normal values in transported and fasted steers, the primary challenge to a transported or feed- and water-deprived animal is a mild metabolic acidosis induced by elevated plasma proteins, which may be the result of a loss of body water. The loss of electrolytes had little effect on the acid-base balance of the animals.

Efeito da heparina liofilizada e da líquida sobre a medida do pH do sangue do cordão umbilical

OBJETIVO: avaliar o efeito da heparina liofilizada e da liquida sobre a medida do pH do sangue do cordao umbilical. METODOS: estudo prospectivo que incluiu cento e duas amostras de sangue arterial do cordao umbilical de recem-nascidos no Servico de Obstetricia do Hospital Geral de Caxias do Sul. As amostras foram divididas em 51 seringas previamente preparadas com heparina liofilizada (seringa A) e 51 seringas preparadas com heparina liquida (seringa B) no momento da coleta sanguinea. A obtencao das amostras foi realizada por duplo clampeamento do cordao entre pincas, imediatamente apos o desprendimento fetal. O pH arterial do sangue obtido foi analisado em no maximo 20 minutos, em analisador de pH da marca AVL OMNI (Viena, Austria). RESULTADOS: a media dos valores de pH no sangue contido nas seringas dos grupos A e B foi de 7,246±0,086 e 7,244±0,084, respectivamente. A analise estatistica demonstrou nao haver diferenca significante entre os valores de pH entre as amostras de sangue contidas em ambos os conjuntos de seringas. CONCLUSAO: as duas formas de heparinizacao de seringas assemelham-se quanto aos efeitos sobre o pH do sangue dos vasos umbilicais, o que permite a escolha daquela de menor custo.

Aeromedical Transfer to Belgium of Severely Burned Patients during the Initial Days following the Volendam Fire

Nineteen critical burn patients were transferred to burn centers in Belgium soon after an indoor fire in The Netherlands. This evacuation was done by helicopter and by ambulance. The first arterial blood gases and pH measurements of the patients on arrival in the burn centers were analyzed and compared. All patients were in metabolic acidosis, but the respiratory component to the pH and the resulting pH was variable. Although an efficient fluid resuscitation to maintain an adequate urine output and arterial pressure is essential, the arterial blood gases and pH should also be monitored during the early evacuation of severe burn patients. Because hyperkaliemia is associated with a low pH value, we suggest that during the evacuation of these patients the ventilation setting should maintain the pH between 7.35 and 7.45. The comparison of the measurements between the group of patients transferred by air and the group transferred by road showed here differences in favor of a road transfer.

Effects of lethal levels of environmental hypercapnia on cardiovascular and blood-gas status in yellowtail, Seriola quinqueradiata.

The cardiorespiratory responses were examined in yellowtail, Seriola quinqueradiata exposed to two levels of hypercapnia (seawater equilibrated with a gas mixture containing 1% CO(2) (water PCO(2) = 7 mmHg) or 5% CO(2) (38 mmHg)) for 72 hr at 20 degrees C. Mortality was 100% within 8 hr at 5% CO(2), while no fish died at 1% CO(2). No cardiovascular variables (cardiac output, Q; heart rate, HR; stroke volume, SV and arterial blood pressure, BP) significantly changed from pre-exposure values during exposure to 1% CO(2). Arterial CO(2) partial pressure (PaCO(2)) significantly increased (P < 0.05), reaching a new steady-state level after 3 hr. Arterial blood pH (pHa) decreased initially (P < 0.05), but was subsequently restored by elevation of plasma bicarbonate ([HCO(3)(-)]). Arterial O(2) partial pressure (PaO(2)), oxygen content (CaO(2)), and hematocrit (Hct) were maintained throughout the exposure period. In contrast, exposure to 5% CO(2) dramatically reduced Q (P < 0.05) through decreasing SV (P < 0.05), although HR did not change. BP was transiently elevated (P < 0.05), followed by a precipitous fall before death. The pHa was restored incompletely despite a significant increase in [HCO(3)(-)]. PaO(2) decreased only shortly before death, whereas CaO(2) kept elevated due to a large increase in Hct (P < 0.05). We tentatively conclude that cardiac failure is a primary physiological disorder that would lead to death of fish subjected to high environmental CO(2) pressures.

Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine-buprenorphine combination in standing horses

ObjectiveTo assess the hormonal, metabolic and physiological effects of laparascopic surgery performed under a sedative analgesic combination of detomidine and buprenorphine in standing horses. Study designProspective study. AnimalsEight healthy adult Dutch Warmblood horses and five healthy adult ponies undergoing laparoscopy were studied. Five healthy adult horses not undergoing laparoscopy were used as a control group. MethodsThe sedative effect of an initial detomidine and buprenorphine injection was maintained using a continuous infusion of detomidine alone. The heart and respiratory rate, arterial blood pH and arterial oxygen and carbon dioxide tensions were monitored, while blood samples were taken for the measurement of glucose, lactate, cortisol, insulin and nonesterified fatty acids (NEFA). The same variables were monitored in a control group of horses which were sedated, but which did not undergo surgery. At the end of the sedation period the effects of detomidine were antagonized using atipamezole. ResultsThe protocol provided suitable conditions for standing laparoscopy in horses. Laparoscopy induced obvious metabolic and endocrine responses which, with the exception of NEFA values, were not significantly different from changes found in the control group. While atipamezole did not produce detectable adverse effects, it is possible that anatagonism may not be essential. ConclusionsThe technique described reliably produces adequate sedation and analgesia for laparoscopic procedures. The level of sedation/analgesia was controlled by decreasing or increasing the infusion rate. Antagonism of the effects of detomidine may not be necessary in all cases.

Fiberoptic bronchoscopy during noninvasive positive pressure ventilation delivered by helmet.

Abstract Objective. To evaluate the feasibility and safety of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) during noninvasive positive pressure ventilation (NPPV) delivered by helmet in patients with acute respiratory failure (ARF) and suspected pneumonia. Design and setting. Prospective, clinical investigation in a general intensive care unit (ICU) of a university hospital. Patients and participants. Four adult patients with ARF who underwent NPPV via the helmet and required fiberoptic BAL for suspected pneumonia. Interventions. NPPV was delivered through the helmet in the pressure support ventilation mode. The specific seal connector placed in the plastic ring of the helmet allowed the passage of the bronchoscope, maintaining assisted ventilation. Arterial blood gas levels, pH, oxygen saturation, respiratory rate, heart rate, and mean arterial blood pressure were monitored during the study. Results. Helmet NPPV avoided gas exchanges deterioration during FOB and BAL, with good tolerance. During the procedure heart rate increased by 5% and mean arterial blood pressure by 7% over baseline; these levels returned to prebronchoscopic values immediately after the withdrawal of the bronchoscope. Endotracheal intubation was never required during the 24 h after the procedure. BAL yielded diagnostic information in three of four patients. Conclusions. NPPV through the helmet allows a safe diagnostic FOB with BAL in patients with hypoxemic ARF, avoiding gas exchange deterioration, and endotracheal intubation. Electronic supplementary material is available if you access this article at http://dx.doi.org/10.1007/s00134-002-1554-5. On that page (frame on the left side), a link takes you directly to the supplementary materials.

Evaluation of bone mineral density with dual x-ray absorptiometry for osteoporosis in children with bladder augmentation

Background/Purpose: Osteoporosis can appear as a result of metabolic acidosis in patients with bladder augmentation and total bladder replacement. These patients must be monitored for early diagnosis and osteoporosis to avoid related complications such as fracture. The current method for diagnosis of osteoporosis mainly involves bone densitometry. Dual x-ray absorptiometry (DXA) provides bone mineral content and bone mineral density (BMD). The purpose of this report is to determine the value of BMD measurement with DXA in the diagnosis and follow-up of osteoporosis and evaluation of response to treatment in the patients with bladder augmentation and total bladder replacement. Methods: Six patients with bladder extrophy and neurogenic bladder underwent colocystoplasty, ureterocystoplasty, and total bladder replacement. The Sigmoid colon segment was used for colocystoplasty. DXA (Hologic 2000 DXA) was used for measuring bone mineral content and density. Results for lumbar spinal BMD were expressed as the average of L1 through L4 values. Each patient's BMD was compared with the mean BMD in the young normal population (T score) and in the age- and sex-matched group (Z score). But because our patients were children, BMD was evaluated according to Z score. Arterial blood gas analysis was obtained periodically with BMD measurement. Arterial blood pH and HCO3 levels of the patients were compared with normal values, which ranged from 7.35 to 7.45 for pH and from 22 to 27 mmol/L for HCO3. Results: Arterial blood pH of 5 of 6 patients (83.3%) and HCO3 levels of all patients were low. Ten BMD measurements were obtained for 6 children. One patient underwent BMD measurement 3 times, 2 patients underwent twice, and the others once. Z scores of 4 of 6 patients (66.6%) were decreased. Blood pH, HCO3 level, and BMD of 2 patients increased after oral bicarbonate intake. Two patients had normal BMD. One of these patients had ureterocystoplasty. The other had undergone colocystoplasty but was incontinent. Conclusions: Intestinal segments have been used for bladder augmentation and total bladder replacement. Exposure of highly absorptive intestinal mucosa to urine has been associated with electrolyte abnormalities and metabolic acidosis. Hyperchloremic acidosis leads to bone demineralization. DXA provides bone mineral content and BMD for diagnosis of osteoporosis. DXA is preferred because the low radiation dose (average, 2 to 4 mrem), accuracy, low price, and short examination time. Not only can BMD confirm the diagnosis of osteoporosis, but it also can be used to monitor the course of the disease and the effectiveness of treatment. J Pediatr Surg 38:230-232. Copyright 2003, Elsevier Science (USA). All rights reserved.

Severe renal tubular acidosis in a renal transplant recipient with repeated acute rejections and chronic allograft nephropathy

Renal tubular acidosis in renal transplant recipients usually is asymptomatic and subclinical. The authors report a case of severe renal tubular acidosis manifested as muscle weakness in a renal transplant recipient. The patient received a renal transplant 30 months ago and had a history of successive episodes of acute rejection during the past 2 months. On admission, arterial blood (arterial blood pH, 7.11; pco2, 12.8 mm Hg; and bicarbonate, 4 mEq/L [4 mmol/L]) and urine gas analysis were compatible with distal renal tubular acidosis. The graft biopsy findings showed superimposed acute rejection on chronic allograft nephropathy, and immunohistochemical staining and electron microscopic findings showed the reduced immunoactivity of H+ATPase pump and anion exchanger 1. The patient was treated successfully with intravenous bicarbonate and oral steroid pulse therapy. This finding suggests that rejection-related renal tubular acidosis should be considered a cause of severely affected metabolic acidosis in renal transplant recipients. Am J Kidney Dis 41:E6.

Hemodynamic changes during complete umbilical cord occlusion in fetal sheep related to hippocampal neuronal damage

Objectives: The purpose of our study was to examine the physiologic changes caused by 10 minutes of umbilical cord occlusion in fetal sheep and to determine the correlation between fetal acidemia or cerebral ischemia and hippocampal neuronal damage. Study design: Thirteen fetal sheep were instrumented and catheterized. Carotid artery blood flow (CaF), fetal mean arterial blood pressure (FMABP), pH, PCO2, base excess, oxygen saturation (SatO2), and PO2 were monitored throughout the occlusion study. Brain sections were examined for the hippocampal neuronal damage. Results: Our data showed severe ischemia (CaF: 10 ± 7 mL/min; FMABP: 29 ± 8 mm Hg) and acidemia (pH: 7.0 ± 0.05; base excess: −9.9 ± 2.4 mEq/L) at the end of occlusion. The neuronal damage score had significant correlations with ischemia and also with reperfusion, but not with the acidemic or hypoxic parameters. Conclusion: We demonstrated that the degree of hippocampal damage was correlated with the degree of ischemia and reperfusion. (Am J Obstet Gynecol 2003;188:413-8.)

Chronic metabolic acid load induced by changes in dietary electrolyte balance increased chloride retention but did not compromise bone in growing swine.

The effects of chronic dietary acid loads on shifts in bone mineral reserves and physiological concentrations of cations and anions in extracellular fluids were assessed in growing swine. Four trials were conducted with a total of 38 (8.16 +/- 0.30 kg, mean +/- SEM) Large White x Landrace x Duroc pigs randomly assigned to one of three dietary treatments. Semipurified diets, fed for 13 to 17 d, provided an analyzed dietary electrolyte balance (dEB, meq/kg diet = Na+ + K+ - Cl-) of -35, 112, and 212 for the acidogenic, control, and alkalinogenic diets, respectively. Growth performance, arterial blood gas, serum chemistry, urine pH, mineral balance, bone mineral content gain, bone-breaking strength, bone ash, and percentage of bone ash were determined. Dietary treatments created a range of metabolic acid loads without affecting (P > 0.10) growth or feed intake. Urine pH was 5.71, 6.02, and 7.65 +/- 0.48 (mean +/- SEM) and arterial blood pH was 7.478, 7.485, and 7.526 +/- 0.006 for pigs fed acidogenic, control, and alkalinogenic treatments, respectively. A lower dEB resulted in an increased (P < 0.001) apparent Cl- retention (106.6, 55.4, and 41.2 +/- 6.3 meq/d), of which only 1.6% was accounted for by expansion of the extracellular fluid Cl- pool as calculated from serum Cl- (105.5, 103.4, 101.6 +/- 0.94 meq/L (mean +/- SEM) for pigs fed acidogenic, control, and alkalinogenic treatments, respectively. A lower dEB did not decrease (P > 0.10) bone mineral content gain, bone-breaking strength, bone ash, percentage of bone ash, or calcium and phosphate balance. In conclusion, bone mineral (phosphate) was not depleted to buffer the dietary acid load in growing pigs over a 3-wk period.

Fiberoptic bronchoscopy during noninvasive positive pressure ventilation delivered by helmet.

To evaluate the feasibility and safety of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) during noninvasive positive pressure ventilation (NPPV) delivered by helmet in patients with acute respiratory failure (ARF) and suspected pneumonia. Prospective, clinical investigation in a general intensive care unit (ICU) of a university hospital. Four adult patients with ARF who underwent NPPV via the helmet and required fiberoptic BAL for suspected pneumonia. NPPV was delivered through the helmet in the pressure support ventilation mode. The specific seal connector placed in the plastic ring of the helmet allowed the passage of the bronchoscope, maintaining assisted ventilation. Arterial blood gas levels, pH, oxygen saturation, respiratory rate, heart rate, and mean arterial blood pressure were monitored during the study. Helmet NPPV avoided gas exchanges deterioration during FOB and BAL, with good tolerance. During the procedure heart rate increased by 5% and mean arterial blood pressure by 7% over baseline; these levels returned to prebronchoscopic values immediately after the withdrawal of the bronchoscope. Endotracheal intubation was never required during the 24 h after the procedure. BAL yielded diagnostic information in three of four patients. NPPV through the helmet allows a safe diagnostic FOB with BAL in patients with hypoxemic ARF, avoiding gas exchange deterioration, and endotracheal intubation. is available if you access this article at http://dx.doi.org/10.1007/s00134-002-1554-5. On that page (frame on the left side), a link takes you directly to the supplementary materials.

Continuous venovenous renal replacement therapy using a pulsatile blood pump.

The objective of this study was to evaluate the efficacy of a pulsatile pump for continuous renal replacement therapy in a pediatric-size animal model. A vacuum-driven, tubular, blood-pumping device was used in 13 pigs weighing 10.4+/-1.5 kg, connected to a neonatal hemofiltration circuit with an FH22 filter and a flow sensor. Three different flow rates [30 ml/min (8 cases), 15 ml/min (3 cases), and 5 ml/min (2 cases] were used over 2-h periods. Aspiration pressure, frequency of pulsation, blood flow rate, ultrafiltrate volume, pre- and post-filter pressures, heart rate, arterial blood pressure, temperature, pH, sodium, potassium, chloride, urea, creatinine, glucose, and hematocrit were measured at 30-min intervals. The mean ultrafiltrate flow was 0.54+/-0.33 ml/kg per min. The aspiration pressure and pulsation frequency needed to maintain blood flow remained stable throughout the experiment. There were no complications secondary to the use of this technique and no significant changes in heart rate, blood pressure, or analytical determinations. In conclusion, in this animal model, the pulsatile pump has been shown to be an effective method for continuous venovenous renal replacement therapy.

Fetal Tobacco Syndrome and Perinatal Outcome

Objective: The aim of this study was to evaluate perinatal outcome in newborns of mothers who are smokers. Methods: The study included 87 pregnant women with a single pregnancy in the cephalic position, 64 of them nonsmokers (group 1), 13 who smoked 5–20 cigarettes per day (group 2) and 10 who smoked more than 20 cigarettes per day (group 3). Maternal demographic variables and laboratory hemoglobin concentration, hematocrit and erythrocyte count in the last trimester were recorded. Perinatal outcome included type of delivery (vaginal or cesarean section), birth weight, occurrence of meconium in the amniotic fluid, 5-min Apgar score, umbilical arterial blood pH postpartum, sex of the newborn, need for treatment at a neonatal intensive care unit (NICU) and clinically and neurosonographically verified postpartum neurologic complications in the newborn. Results: A statistically significant correlation (p < 0.01) was found with the mean gestational age at delivery in all three groups of women, especially in those smoking >20 cigarettes per day, who had a higher incidence of premature deliveries. Maternal laboratory findings also differed significantly among the three groups of women, i.e. erythrocyte count (p < 0.01), hemoglobin concentration (p < 0.01) and hematocrit (p < 0.001). The rate of delivery by cesarean section was significantly higher in the groups of smokers, irrespective of the number of cigarettes per day (groups 2 and 3). Birth weight was lower by about 250 and 350 g (p < 0.001) in groups 2 and 3, respectively. Five-minute Apgar score and umbilical arterial blood pH were lower in group 3 as compared with groups 1 and 2 (p < 0.01). NICU treatment was required in more than 50% of infants born to group 3 mothers, in whom 70% of perinatal neurologic complications such as subependymal hemorrhage, periventricular hemorrhage, porencephalic cysts, intracranial hemorrhage and swallowing disturbance of the newborn were recorded (p < 0.001). The infants born to group 3 mothers had a longer and more difficult period of adaptation, thus often requiring an NICU stay. Conclusion: Our study confirmed that pregnancy burdened with smoking, especially in the case of >20 cigarettes a day, is associated with a high risk due to the development of maternal anemia and fetal hypoxia and polyglobulia, which in turn result in a significantly poorer perinatal outcome in infants born to smoking mothers and compromised subsequent development of the child, as evidenced by the morphological substrates on the brain resulting from the fetal mechanism of defense against hypoxia. Clinically, there was no other (etiologic) reason for (chronic) fetal hypoxia; thus, the clinical substrate of fetal tobacco syndrome could be presumed to have developed consequentially to chronic smoking during pregnancy, as a preuterine factor of fetal hypoxia. Other gestational or gestation-related diseases (e.g., gestosis, diabetes) that may potentially cause nutritional and respiratory insufficiency of the placenta were ruled out.

Gebären und geboren werden im Wasser - Vergleichende Studie nach 969 Wassergeburten

Purpose: The object of our study was to analyze 969 consecutive water births and compare them with other delivery positions. Methods: We compared 969 water births, 515 deliveries in the traditional bed, and 172 deliveries on the delivery stool. Duration of labor, rates of episiotomies and lacerations, arterial cord blood pH, analgesic requirements and postpartum maternal hemoglobin levels were analyzed. Results: The first stage of labor was significantly shorter in primiparas with water birth compared with the other delivery positions (381 vs. 473 min). There were no differences in the duration of the second stage. The low episiotomy rate with the water births (0,52% compared with 17,2% and 7,6% for the other two positions) was not associated with an increased rate of perineal lacerations (23% in all three groups). Of the primiparas, 58% had no lacerations with water birth compared with 36% and 48% for the other positions, respectively. No woman with water birth required analgesics. There were no differences among the groups in arterial cord blood pH, in base-excess or postpartal maternal hemoglobin level. Conclusions: Our results suggest that water birth is associated with a significantly shorter first stage of labor, a lower episiotomy rate, fewer perineal lacerations, and reduced analgesic requirements compared with other delivery positions. Water birth appears to be safe for the mother and the fetus-neonate if candidates are selected appropriately.

Fetal grasping of the umbilical cord and perinatal outcome.

This study assessed perinatal outcome in pregnancies with accidentally diagnosed fetal grasping of the umbilical cord (FGUC) on ultrasonography (US) in late gestation as a possible cause of fetal hypoxia due to mechanical occlusion of umbilical circulation. In this retrospective clinical study, routine antenatal US examination revealed FGUC from 32 to 41 weeks of gestation in seven normal single pregnancies. Upon FGUC findings, fetal condition was followed up every second day by repeat US findings of FGUC, and then by Doppler parameters of fetoplacental circulation measurement of resistance index in umbilical artery (URI) and middle cerebral artery (CRI), and cardiotocography (CTG), and perinatal outcome (peripartal cardiotocography, 5-min Apgar score, umbilical arterial blood pH, occurrence of meconium amniotic fluid, need of additional treatment at neonatal intensive care unit (NICU), and mode of pregnancy termination (cesarean section, forceps or vacuum extraction-VE for hypoxia). After delivery, neonatal neurosonography and neonatal complications related to pregnancy or birth were evaluated. All URI values were increased, resulting from persistent FGUC and elevated umbilical arterial RI. CRI showed great oscillations in the values for gestational age and decreased CRI. In two cases, cerebral/umbilical ratio was less than 1, indicating initial vasocentralization as a fetal compensatory mechanism for hypoxia. In these cases, a pathological peripartal CTG and pH 7.23, indicative of preacidosis, were verified. All children were discharged from NICU as healthy, free from neurological lesions, with the exception of the latter, who had dystonia syndrome and mild motor deficit as a sign of peripartal hypoxia. Although it probably belongs to normal reflexes, intermittent FGUC should be US controlled. Persistent FGUC should be considered pathological for its possible hypoxic effect and umbilical circulation obstruction. These pregnant women should be hospitalized and closely monitored, as in part confirmed by the present study.

Effects of underwater sound exposure on neurological function and brain histology

To evaluate the safety of sonar exposure from a neurological perspective, the vulnerability of the central nervous system to underwater exposure with high-intensity, low-frequency sound (HI-LFS) was experimentally examined. Physiological, behavioral and histological parameters were measured in anesthetized, ventilated rats exposed to brief (5 min), underwater HI-LFS. Exposure to 180 dB sound pressure level (SPL) re 1 μPa at 150 Hz ( n = 9) did not alter acute cardiovascular physiology (arterial blood pH, pO 2, pCO 2, heart rate, or mean arterial blood pressure) from that found in controls ( n = 11). Rats exposed to either 180 dB SPL re 1 μPa at 150 Hz ( n = 12) or 194 dB SPL re 1 μPa at 250 Hz ( n = 12) exhibited normal cognitive function at 8 and 9 days after sound exposure. Evaluation of neurological motor function revealed a minor deficit 7 days after 180 dB SPL/150 Hz exposure that resolved by 14 days, and no deficits after 194 dB SPL/250 Hz exposure. No overt histological damage was detected in any group. These data suggest that underwater HI-LFS exposure may cause transient, mild motor dysfunction.

Impact of carbon dioxide and helium insufflation on cardiorespiratory function during prolonged pneumoperitoneum in an experimental rat model.

Experimental studies on laparoscopic surgery are often performed in rats. However, the hemodynamic and respiratory responses related to the pneumoperitoneum have not been studied extensively in rats. Therefore, the aim of this study was to investigate in spontaneously breathing rats the effects of CO2 and helium, insufflation pressure, and duration of pneumoperitoneum on blood pressure, arterial pH, pCO2, pO2, HCO3-, base excess, and respiratory rate. Five groups of 9 Brown Norway rats were anesthetized and underwent CO2 insufflation (6 or 12 mmHg), helium insufflation (6 or 12 mmHg), or abdominal wall lifting (gasless control) for 120 min. Blood pressure was monitored by an indwelling carotid artery catheter. Baseline measurements of mean arterial pressure (MAP), respiratory rate, arterial blood pH, pCO2, pO2, HCO3-, and base excess were recorded. Blood gases were analyzed at 5, 30, 60, 90, and 120 min during pneumoperitoneum, and MAP and respiratory rate were recorded at 5 and 15 min and at 15-min intervals thereafter for 2 h. CO2 insufflation (at both 6 and 12 mmHg) caused a significant decrease in blood pH and increase in arterial pCO2. Respiratory compensation was evident since pCO2 returned to preinsufflation levels during CO2 insufflation at 12 mmHg. There was no significant change in blood pH and pCO2 in rats undergoing either helium insufflation or gasless procedures. Neither insufflation pressure nor the type of insufflation gas had a significant effect on MAP over time. The cardiorespiratory changes during prolonged pneumoperitoneum in spontaneously breathing rats are similar to those seen in clinical practice. Therefore, studies conducted in this animal model can provide valuable physiological data relevant to the study of laparoscopic surgery.

The anti-nociceptive and cardiopulmonary effects of extradural fentanyl–xylazine in sheep

ObjectiveTo compare the anti-nociceptive effects of extradural xylazine, fentanyl and a xylazine–fentanyl combination in sheep, and to measure the cardiopulmonary effects of the xylazine–fentanyl combination. Study designProspective, randomized study. AnimalsTwenty-five half-merino ewes 2–4 years of age and body mass 54.2 ± 1.1 kg. MethodsSix sheep in group 1 received 0.2 mg kg−1 xylazine by extradural injection, six in group 2 received fentanyl 1.5 μg kg−1 and 13 in group 3 received the combination of both treatments. In all groups, drugs were mixed with saline (0.15 mL kg−1 before injection). Pulmonary and carotid arterial catheters were placed in seven sheep of group 3 which were used to evaluate cardiopulmonary effects. Anti-nociception was determined by the response to electrical stimulation (40 V for 1.5 milliseconds) of the left flank and by superficial and deep muscular ‘pinpricking’ stimulation of the pelvic and thoracic limbs and thoracolumbar region. ResultsLack of response to electrical stimulation at the left flank was present in 10 ± 1.1 minutes (mean ± SEM) (group 1) and in 4.5 ± 0.5 minutes in group 3. The duration of lack of response to electrical stimulation at the left flank was 96 ± 6 minutes in group 1 and 315 ± 6 minutes in group 3. Responses persisted in group 3. Significant decreases (p < 0.05) in cardiac output 30, 45, 60 and 90 minutes after injection, and in cardiac work at 30 and 45 minutes were observed in the seven animals of group 3. Arterial blood pH was lowest at 90 minutes, arterial bicarbonate was lowest at 60 minutes and values for both arterial and mixed venous base excess increased significantly at 60 and 90 minutes. There was no significant change from baseline values in heart rate, mean arterial blood pressure, respiratory rate, body temperature, systemic vascular resistance, arterial and mixed venous PO2, PCO2, oxygen saturation, blood oxygen content, haemoglobin concentration, mixed venous blood bicarbonate and pH. ConclusionsFentanyl decreases the onset time and prolongs the duration of anti-nociception produced by xylazine. The combination decreases cardiac output but is without significant respiratory effects. Clinical relevanceFurther studies are required to show that surgery is possible in sheep after extradural xylazine–fentanyl injection.

Alveolar hypercapnia augments pulmonary C-fiber responses to chemical stimulants: role of hydrogen ion.

To determine whether the excitabilities of pulmonary C fibers to chemical and mechanical stimuli are altered by CO(2)-induced acidosis, single-unit pulmonary C-fiber activity was recorded in anesthetized, open-chest rats. Transient alveolar hypercapnia (HPC) was induced by administering CO(2)-enriched gas mixture (15% CO(2), balance air) via the respirator inlet for 30 s, which rapidly lowered the arterial blood pH from a baseline of 7.40 +/- 0.01 to 7.17 +/- 0.02. Alveolar HPC markedly increased the responses of these C-fiber afferents to several chemical stimulants. For example, the C-fiber response to right atrial injection of the same dose of capsaicin (0.25-1.0 microg/kg) was significantly increased from 3.07 +/- 0.70 impulses/s at control to 8.48 +/- 1.52 impulses/s during HPC (n = 27; P < 0.05), and this enhanced response returned to control within approximately 10 min after termination of HPC. Similarly, alveolar HPC also induced significant increases in the C-fiber responses to right atrial injections of phenylbiguanide (4-8 microg/kg) and adenosine (0.2 mg/kg). In contrast, HPC did not change the response of pulmonary C fibers to lung inflation. Furthermore, the peak response of these C fibers to capsaicin during HPC was greatly attenuated when the HPC-induced acidosis was buffered by infusion of bicarbonate (1.36-1.82 mmol. kg(-1). min(-1) for 35 s). In conclusion, alveolar HPC augments the responses of these afferents to various chemical stimulants, and this potentiating effect of CO(2) is mediated through the action of hydrogen ions on the C-fiber sensory terminals.

Meconium-Stained Amniotic Fluid in Labor: A Randomized Trial of Prophylactic Amnioinfusion

Puertas, Alberto; Paz Carrillo, M.; Moltó , Luis; Álvarez, Margarita; Sedeño, Salvador; Miranda, José