Arterial Blood pH Research Articles

Randomized Trial of Low-pressure Carbon Dioxide-elicited Pneumoperitoneum Versus Abdominal Wall Lifting for Laparoscopic Cholecystectomy

Two alternative surgical techniques for elective laparoscopic cholecystectomy (LC), low-pressure insufflation of the peritoneal cavity and abdominal wall lifting (AWL), have been developed over time to minimize the disadvantages associated with CO2-elicited pneumoperitoneum. To the best of our knowledge, the 2 methods have seldom been compared as regards their relative advantages and disadvantages. Eighty patients scheduled for elective LC were randomized into either a low-pressure (8 mmHg) CO2 insufflation method (LPLC) group, or a gasless technique using a subcutaneous abdominal wall lifting device (GLC group). The duration of the surgical procedure, the surgical results including level of postoperative pain, and perioperative cardiopulmonary function changes experienced by the members of both groups were compared. Laparoscopic surgery was completed for all but 1 patient from each group due to an inadequate surgical-site exposure. There was no mortality for study participants, and no major complications were noted for members of either group. The LPLC group evidenced a shorter surgical duration as compared to the GLC group (77 +/- 28 minutes vs. 98 +/- 27 minutes, respectively; p < 0.01) and a lower incidence of postoperative shoulder pain (2/38 vs. 8/39, respectively; p < 0.05), although significant differences in intraoperative pulmonary function were noted (an increased PaCO2, Pet CO2 and peak-airway pressure and decreased arterial blood pH; p < 0.01) for the LPLC group compared to the GLC group. Both alternative methods for this type of surgery appeared feasible and safe for LC. Low-pressure CO2 pneumoperitoneum had a shorter surgical duration and less postoperative shoulder pain compared to the GLC technique, but did not feature any other advantage over the AWL technique with regard to impact on cardiopulmonary function.

Comparative study of calculated and measured total carbon dioxide

Total carbon dioxide content (TCO2) can be calculated from measured values of pH and pCO2 according to a simplified and standardized form of the Henderson-Hasselbalch equation, or measured directly. We assessed the agreement between calculated TCO2 and measured TCO2 using a total of 74 blood samples. Calculated TCO2 was obtained using blood gas analysis of pH and pCO2 in arterial whole blood on a Nova Stat Profile Critical Care Xpress analyzer. Measured TCO2 was determined using a Dimension RxL analyzer on arterial plasma, and was used as the comparative method. Deming regression analysis, correlation coefficients, bias (Bland-Altman method) and Student's t-test were used for statistical analysis. Deming regression analysis showed a high degree of correlation between calculated and measured TCO2 (r=0.97). The slope (0.96; 95% CI=0.90- 1.02) of the regression line was close to 1 with a positive intercept (2.86 mmol/L; 95% CI=1.44-4.27), and the standard error of the estimate was 0.20 mmol/L. The mean bias was 1.94 mmol/L with a standard deviation of 1.69 mmol/L. The pCO2 values showed a significant effect on calculated TCO2. Most paired differences were within the 95% limits of agreement (-1.45 to 5.33 mmol/L). Calculated TCO2 determined using blood gas analysis agreed with measured TCO2 and may be used to assess acid-base imbalance. However, clinicians should be cautious if using this calculated value in the critically ill patient.

A new measure of acute physiological derangement for patients with exacerbations of obstructive airways disease: The COPD and Asthma Physiology Score

Decisions about how to treat patients with acute exacerbations of obstructive airways disease-chronic obstructive pulmonary disease (COPD), asthma or mixed diagnoses-often require an understanding of prognosis. This depends on the severity of the acute deterioration and the patient's functional reserve. There are currently no validated disease-specific scores that measure the severity of the acute exacerbation. To develop an acute physiology score for exacerbations of obstructive airways disease. Secondary analysis of a high-quality clinical database, the Case Mix Programme Database. One hundred and sixty-eight adult, general critical care units in England, Wales and Northern Ireland. A total of 8527 patients with obstructive airways disease were identified with a mean (SD) age of 65.9 (9.7) years and hospital mortality of 35.5%. The COPD and Asthma Physiology Score (CAPS) was developed using logistic regression. The CAPS included eight variables: heart rate, mean arterial blood pressure, pH, sodium, urea, creatinine, albumin and white blood cell count. The score had fair discrimination with an area under the receiver operating characteristic curve of 0.718. This performance was reproduced in a further validation dataset of 7957 patients. The discrimination of the CAPS in these validation data exceeded that of the acute physiology scores from APACHE II and III and the physiological components of SAPS II. The CAPS can be used to estimate the prognostic impact of physiological derangements accompanying an acute exacerbation of obstructive airways disease and has the potential for even greater predictive performance when combined with measures of a patient's functional reserve.

Antiretroviral agents and acid-base balance at delivery of the neonate

Limited evidence is available regarding antiretroviral (ARV) safety for uninfected infants exposed to these drugs in utero. Our objective was to determine if ARV administered to pregnant women is associated with decreasing umbilical arterial pH and base excess in uninfected infants. A prospective study was conducted on 57 neonates divided into three groups: ZDV group, born to mothers taking zidovudine (N = 20), triple therapy (TT) group, born to mothers taking zidovudine + lamivudine + nelfinavir (N = 25), and control group (N = 12), born to uninfected mothers. Umbilical cord blood was used to determine umbilical artery gases. A test was performed to calculate the sample by comparing means by the unpaired one-tailed t-test, with alpha = 0.05 and beta = 20%, indicating the need for a sample of 18 newborn infants for the study groups to detect differences higher than 20%. The control and ARV groups were similar in gestational age, birth weight, and Apgar scores. Values of pH, pCO2, bicarbonate, and base excess in cord arterial blood obtained at delivery from the newborns exposed to TT were 7.23, 43.2 mmHg, 19.5 mEq/L, and -8.5 nmol/L, respectively, with no significant difference compared to the control and ZDV groups. We conclude that intrauterine exposure to ARV is not associated with a pathological decrease in umbilical arterial pH or base excess. While our data are reassuring, follow-up is still limited and needs to be continued into adulthood because of the possible potential for adverse effects of triple antiretroviral agents.

A randomized controlled study evaluating the effects of the temperature of insufflated CO2 on core body temperature and blood gases (an experimental study)

Heated carbon dioxide (CO2) was used for pneumoperitoneum (Pp) to prevent hypothermia. This study aimed to investigate the relationship between the temperature of the insufflated CO2 and blood gases together with the core body temperature (CBT). A prospective controlled study was performed with 24 pigs weighing approximately 20 kg randomized into four groups of 6 pigs each. A pneumoperitoneum at 12 mmHg of pressure was applied for 60 min with the pig under general anesthesia. The CO2)temperature was 22 degrees C in group 1, 37 degrees C in group 2, and 7 degrees C in group 3. In the "sham" group, pneumoperitoneum was not applied. Arterial blood pH and partial pressure of CO2 (PaCO2) were analyzed before insufflation, every 15 min during the pneumoperitoneum, and 15 min after the desufflation. The CBT was recorded before the insufflation, every 20 min during pneumoperitoneum, and 20 min after the desufflation. Blood gas analyses and CBT records for the "sham" group were performed at the same intervals. Arterial blood pH gradually decreased during pneumoperitoneum. At the 60th minute of pneumoperitoneum, a minimum decrease in arterial blood pH (0.04; p = 0.027) and a minimum increase in PaCO2 (3.67; p = 0.027) were recorded in group 3, whereas a maximum decrease in arterial blood pH (0.18; p = 0.027) and a maximum increase in PaCO2 (17.17; p = 0.027) were recorded in group 2. There was a significant negative correlation between PaCO2 and arterial blood pH in all the groups (r = -0.993; p < 0.01). The mean values of CBT decreases were statistically significant in all the groups: group 1 (p = 0.023), group 2 (p = 0.026), group 3 (p = 0.026), and "sham" group (p = 0.024). The changes in PaCO2 were directly proportional and the changes in pH contrarily proportional to the temperature of the insufflated CO2. Significant differences in CBT decreases were found between the groups receiving heated gas and room temperature gas and the groups receiving heated gas and gas below room temperature.

Gebären im Wasser: Erfahrung nach 1825 Wassergeburten

We reviewed 1,825 water births at a single institution over a 9-year period.We compared 830 primipara deliveries in water with 424 primipara deliveries in the traditional bed and 136 on the delivery stool. We also evaluated the duration of labour, arterial cord blood pH and base excess in the primiparae, and perineal trauma, shoulder dystocia and deliveries after preceding caesarean section as well as rates of neonatal infection in all the 1,825 water births.The duration of the first stage of labour was significantly shorter with water births than with the other delivery positions. The episiotomy rate for all water births was found to be much lower compared to deliveries carried out in the bed or on the birthing stool. The rate of perineal tears was similar. There were no differences in the duration of the second stage, arterial cord blood pH and base excess. No woman using the water birth method required analgesics. There were 3 shoulder dystocias with water births. Sixty-eight women delivered in water after a preceding caesarean section.Water births appears to be associated with a significantly shorter first stage of labour, a lower episiotomy rate and reduced analgesic requirements when compared with other delivery positions. If women are selected appropriately, water birth appears to be safe for both the mother and neonate.

Hemogasometria e variáveis cardiopulmonares após administração do butorfanol em cães anestesiados pelo desfluorano sob ventilação espontânea

Este experimento teve por objetivos avaliar as possíveis alterações cardiopulmonares e hemogasométricas decorrentes do uso do butorfanol em cães submetidos à anestesia pelo desfluorano sob ventilação espontânea. Para tal, foram utilizados vinte cães adultos, clinicamente saudáveis, pesando 12±3kg. Os animais foram distribuídos igualmente em dois grupos, GS e GB, e induzidos à anestesia com propofol (8,4±0,8mg kg-1, IV), intubados e submetidos à anestesia inalatória pelo desfluorano (10V%). Decorridos 40 minutos da indução, foi administrado aos animais do GS 0,05mL kg-1 de solução fisiológica a 0,9% (salina), enquanto que, no GB, foi aplicado butorfanol na dose de 0,4mg kg-1, ambos pela via intramuscular. As observações das variáveis freqüências cardíaca (FC) e respiratória (f), pressões arteriais sistólica (PAS), diastólica (PAD) e média (PAM), pH arterial (pH), pressão parcial de oxigênio no sangue arterial (PaO2), pressão parcial de dióxido de carbono no sangue arterial (PaCO2), déficit de base (DB), bicarbonato (HCO3) e saturação de oxigênio na hemoglobina (SatO2) tiveram início imediatamente antes da aplicação do opióide ou salina (M0). Novas mensurações foram realizadas 15 minutos após a administração do butorfanol ou salina (M15) e as demais colheitas foram realizadas a intervalos de 15 minutos, por um período de 60 minutos (M30, M45, M60 e M75). Os dados numéricos dessas variáveis foram submetidos à Análise de Perfil (P&lt;0,05). A freqüência cardíaca apresentou alteração no GB, com média de M0 maior que as demais. As PAS, PAD e PAM, assim como a f e o pH, apresentaram valores menores após a administração do opióide no GB, em comparação ao GS. A PaO2 apresentou discretas alterações, entretanto sem significado clínico, enquanto que a PaCO2 e o DB apresentaram valores de M0 menores que os demais após a aplicação do butorfanol. Os resultados obtidos permitem concluir que a administração do butorfanol em cães submetidos à anestesia pelo desfluorano, sob ventilação espontânea, reduz a freqüência cardíaca e a pressão arterial e promove certo grau de hipoventilação.

Acid-base analysis of individuals following two weight loss diets

To examine the effects of low-carbohydrate, ketogenic (LCKD) and low-fat (LFD) diets on acid-base status. Prospective analysis of volunteers from two clinical trials. Subset of 39 volunteers from a randomized trial comparing the effects of an LCKD with an LFD, and a single-arm trial of an LCKD. Outpatient research clinic. LCKD (initially <20 g of carbohydrate daily) or LFD (<30% of energy from fat, 500-1000 kcal energy reduction) instruction. Arterial blood gas analysis, serum chemistries (electrolytes, urea nitrogen/creatinine, glucose, ketone bodies, lactate), anion gap, and urine ketone bodies measured at weeks 0, 2, 8, and 24. Participants had a mean (+/-standard deviation) age of 43.5+/-9.3 years; 28 (72%) were female, 29 (74%) were Caucasian. Using linear mixed-model analysis to examine blood test changes from baseline to 24 weeks, the LFD group experienced a decrease in arterial blood pH from a mean of 7.43 at week 0 to 7.40 at week 24 (P=0.03), and the LCKD group experienced a decrease from 7.42 at week 0 to 7.40 at week 24 (P=0.01). The lowest pH measurements observed were 7.34 in the LFD group and 7.37 in the LCKD group. Although serum bicarbonate appeared to decrease from baseline at weeks 2 and 8 in the LCKD group, the change at 24 weeks was not statistically significant in either diet group, and only four of 131 (two of 92 from the LCKD group) measurements were less than 22 mmol/l. The proportion of participants with elevated urine and serum ketone body levels rose in the LCKD group only, was highest at week 2, and decreased over the subsequent time points. In individuals following an LCKD or an LFD, blood pH decreased mildly and the LCKD group experienced a small, transient decrease in serum bicarbonate in conjunction with mild ketosis. This suggests that an LCKD induced a mild compensated metabolic acidosis, but no individual showed evidence of significant metabolic derangement.

A Typical Case of Fulminant Type 1 Diabetes Mellitus

Recently type 1 with acute onset and no evidence of islet autoantibodies have been showed as type 1 diabetes and as novel subtype of type 1B diabetes. The study was made progress in Japan. We report a typical case of fulminant type 1 diabetes.A 24 years old male to be in good condition visited our hospital because of flu-like symptom, diarrhea, and abdominal discomfort. He has no medical history and family history of diabetes. The level of plasma glucose is 962 mg/dL, serum ketone body 5.8 mmol/L, arterial blood pH 7.111 and he was diagnosed as diabetic ketoacidosis. Anti-GAD antibody and islet cell antibody were negative and HbA1c is 5.5%. All of them were compatible with the diagnostic criteria of fulminant type 1 diabetes.After the patient has been treated with insulin, his symptoms were improved and abnormal laboratory data were normalized. We report this case with a review of the literature. (J Kor Diabetes Assoc 31:175~179, 2007)

Epidural anesthesia with bupivacaine, bupivacaine and fentanyl, or bupivacaine and sufentanil during intravenous administration of propofol for ovariohysterectomy in dogs

To compare cardiovascular and systemic effects and analgesia during the postoperative period of epidural anesthesia performed with bupivacaine alone or with fentanyl or sufentanil in bitches maintained at a light plane of anesthesia with continuous infusion of propofol. Prospective randomized masked clinical trial. 30 female dogs of various breeds. Dogs were allocated into 3 groups of 10 each. One group received fentanyl (2 microg/kg [0.91 microg/lb]) and bupivacaine (1 mg/kg [0.45 mg/lb]), 1 group received sufentanil (1 microg/kg) and bupivacaine (1 mg/kg), and 1 group received bupivacaine (1 mg/kg). All dogs received acepromazine (0.1 mg/kg [0.045 mg/lb]) and continuous infusion of propofol for sedation. The agents were administered into the lumbosacral space and diluted in saline (0.9% NaCl) solution to a total volume of 0.36 mL/kg (0.164 mL/lb). Cardiac and respiratory rates, arterial blood pressures, pH, and blood gases were evaluated. Analgesia, sedation level, serum cortisol concentrations, and plasma catecholamine concentrations were measured regularly for 6 hours. No important changes in cardiovascular, respiratory, or sedation variables were observed. Degree of analgesia in the postoperative period was higher in the sufentanil group, although use of fentanyl and bupivacaine also resulted in a sufficient level of analgesia. Use of the 3 anesthetic techniques permitted ovariohysterectomy with sufficient analgesia and acceptable neuroendocrine modulation of pain with minimal adverse effects.

Relationship between Twin-to-twin Delivery Interval and Umbilical Artery Acid-base Status in the Second Twin

The purpose of this study was to determine the effect of twin-to-twin delivery interval on umbilical artery acid-base status of the second twin at birth. This was a retrospective cohort study of all live-born twins with measured acid-base status in umbilical arterial blood who were delivered after 34 weeks' gestation from June 2003 to February 2006. Twins with any maternal or fetal complications were excluded. Subjects were divided into two groups based on the mode of delivery of the first twin: normal cephalic vaginal deliveries (n=40) or cesarean deliveries (n=67). The inter-twin differences in umbilical arterial blood pH, PCO2, PO2, and base excess in twin newborns born vaginally were significantly greater than the corresponding differences in those born by cesarean section. A significant positive correlation was found between twin-to-twin delivery interval and inter-twin difference in umbilical arterial blood pH in twin newborns born vaginally. The umbilical arterial blood pH of the second twin was less than 7.0 in 14% (2/14) in cases delivered more than 20 min after the first twin. The umbilical arterial blood gas status of the second twin worsened with increasing twin-to-twin delivery interval, and pathologic fetal acidemia (pH < 7.0) might develop in the second twin when the twin-to-twin delivery interval was greater than 20 min.

Effect of stanford pouch and ileal conduit urinary diversions on bone mineral density and metabolism

After urinary-intestinal diversions metabolic complications may occur in long term follow up. We aimed to evaluate bone metabolism changes in urinary diverted patients. Nineteen patients with urinary diversions (11 Stanford pouch and 8 ileal conduit) performed with diagnosis of locally invasive bladder cancer and 19 age-sex matched healthy subjects were enrolled in the study. Bone mineral density (BMD), arterial blood pH, bicarbonate and base excess as well as bone mineralisation parameters at urine and serum were evaluated for all groups. For statistical evaluation, nonparametric comparisons between groups were used. Comparison of ileal conduit and control groups displayed higher alkaline phosphatase and parathormone levels in the patient group though the difference was not significant. The mean BMD values of ileal conduit group were osteopenic, revealing a significant difference with the control group. Statistically significant differences between alkaline phosphatase, parathormone levels of Stanford pouch and control groups were apparent whereas BMD values were not significantly different. When the two patient groups were compared with each other, no difference in BMD or bone metabolism parameter values could be observed. Patients with urinary diversions are under risk of bone demineralisation and must be followed by BMDs, arterial blood analysis and bone mineral metabolism parameters.

Does poor oxygenation during one-lung ventilation impair aerobic myocardial metabolism in patients with symptomatic coronary artery disease?

One-lung ventilation is used during a variety of surgical procedures, even in patients with pre-existing coronary artery disease. The study purpose was to elucidate if myocardial metabolism crosses the anaerobic threshold under hypoxemia during one-lung ventilation. Therefore, we determined myocardial metabolism as a marker for anaerobic myocardial metabolism in patients with significant multi-vessel coronary artery disease undergoing one-lung ventilation during minimally-invasive coronary artery bypass grafting. Twenty patients with multi-vessel coronary artery disease underwent minimally-invasive revascularisation on cardiopulmonary bypass. One-lung ventilation was used for at least 45 min prior to cardiopulmonary bypass. Blood samples were drawn from arterial and coronary sinus blood at various times throughout the procedure to determine myocardial metabolism. After institution of one-lung ventilation arterial partial pressure of oxygen decreased significantly, down to levels between 50 and 70 mmHg. During one-lung ventilation, pH and lactate levels in both arterial and coronary sinus blood remained constant. Significant changes of pH and lactate levels were observed only after cardiopulmonary bypass. No clinically significant signs of myocardial ischemia occurred in any patient. Aerobic myocardial metabolism was unaffected during one-lung ventilation in all patients. Therefore, one-lung ventilation can be applied to patients with multi-vessel coronary artery disease with an acceptable risk of turning myocardial metabolism to an anaerobic state.

Comparison of variability in cardiorespiratory measurements following desflurane anesthesia at a multiple of the minimum alveolar concentration for each dog versus a multiple of a single predetermined minimum alveolar concentration for all dogs in a group

To determine whether the variability of cardiorespiratory measurements is smaller when administering desflurane at a multiple of the individual's minimum alveolar concentration (MAC) or at a predetermined, identical concentration in all subjects. 10 dogs. Desflurane was administered at 1.5 times the individual's MAC (iMAC) and 1.5 times the group's MAC (gMAC). The order of concentrations was randomly selected. Heart rate, respiratory rate, arterial blood pressure, central venous pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, arterial and mixed-venous blood gas tensions and pH, and cardiac output were measured. The desflurane concentration required to achieve a mean arterial pressure (MAP) of 60 mm Hg was then determined. Finally, the desflurane concentration required to achieve an end-tidal PCO(2) of 55 mm Hg was measured. Variances when administering 1.5 iMAC or 1.5 gMAC were not significantly different for any variable studied. Differences between the MAC multiples needed to reach an MAP of 60 mm Hg and the mean of the sample were significantly larger when gMAC was used, compared with iMAC, indicating that a multiple of iMAC better predicted the concentration resulting in a MAP of 60 mm Hg. Results suggest that, in a small group of dogs, variability in cardiorespiratory measurements among dogs is unlikely to differ whether an inhalant anesthetic is administered at a multiple of the iMAC in each dog or at an identical gMAC in all dogs.

Intrapulmonary percussive ventilation in tracheostomized patients: a randomized controlled trial

To investigate whether the addition of intrapulmonary percussive ventilation to the usual chest physiotherapy improves gas exchange and lung mechanics in tracheostomized patients. Randomized multicenter trial in two weaning centers in northern Italy. 46 tracheostomized patients (age 70 +/- 7 years, 28 men, arterial blood pH 7.436 +/- 0.06, PaO(2)/FIO(2) 238 +/- 46) weaned from mechanical ventilation. Patients were assigned to two treatment groups performing chest physiotherapy (control), or percussive ventilation (IMP2 Breas, Sweden) 10 min twice/day in addition to chest physiotherapy (intervention). Arterial blood gases, PaO(2)/FIO(2) ratio, and maximal expiratory pressure were assessed every 5th day for 15 day. Treatment complications that showed up in 1 month of follow-up were recorded. At 15 days the intervention group had a significantly better PaO(2)/FIO(2) ratio and higher maximal expiratory pressure; after follow-up this group also had a lower incidence of pneumonia. The addition of percussive ventilation to the usual chest physiotherapy regimen in tracheostomized patients improves gas exchange and expiratory muscle performance and reduces the incidence of pneumonia.

From the editors

From the editors

Vitamin C and Vitamin E in Pregnant Women at Risk for Pre-eclampsia (VIP Trial): Randomized Placebo-Controlled Trial

Although at least one small-scale study has suggested that supplemental vitamins C and E may lower the risk of preeclampsia, others have yielded negative results. The present randomized, placebo-controlled trial evaluated these antioxidants in 2410 women, seen at 25 centers, who were viewed as being at increased risk of preeclampsia because of such factors as preeclampsia in the preceding pregnancy, HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), eclampsia in any past pregnancy at any gestational stage, essential hypertension requiring medication, and type 1 or type 2 diabetes. Participants were assigned to receive either 1000 mg vitamin C plus 400 IU vitamin E or a matched placebo each day from the second trimester of pregnancy to delivery. Preeclampsia developed in 15% of study participants. Vitamin supplementation did not lower the risk regardless of the level of risk at entry to the trial. Risk rates ranged from 11% in primiparous obese women and those with multiple pregnancies to 32% in women having chronic renal disease. The risk for women with multiple risk factors was 26%. There were no group differences in either severe preeclampsia (with marked hypertension) or early-onset preeclampsia (delivery for preeclampsia before 34 weeks gestation). More women in the supplemented group were treated for gestational hypertension. Infants whose mothers received vitamin supplements were significantly likelier to have low birth weight, but there was no difference in small-for-gestational-age infants. Preterm births were comparably frequent in the supplemented and control groups, but infants of supplemented mothers more often had a cord arterial blood pH less than 7. The risk of perinatal death was similar in the 2 groups. These findings fail to support routine supplementation with vitamins C and E for pregnant women at increased risk of developing preeclampsia. Supplementation may have adverse effects such as low birth weight and low arterial cord blood pH and, for this reason, cannot be recommended, at least in the doses used in this trial.

Blood-gas properties of plateau zokor (Myospalax baileyi)

Plateau zokor (Myospalax baileyi) is one of the blind subterranean mole rats that spend their life solely underground in sealed burrows. It is one of the special species of the Qinghai-Tibet plateau. In their burrows, oxygen is low and carbon dioxide is high and their contents fluctuate with the change of seasons, soil types, rain and depth of burrows. However, plateau zokors show successful adaptation to that extreme environment. In this study, their adapting mechanisms to the hypoxic hypercapnic environment were analyzed through the comparison of their blood-gas properties with that of pikas (Ochotona curzniae) and Sprague-Dawley rats. The results indicated that plateau zokors had higher red blood corpuscle counts (8.11+/-0.59 (10(12)/L)) and hemoglobin concentrations (147+/-9.85 g/L), but hematocrit (45.9+/-3.29%) and mean corpuscular volume (56.67+/-2.57 fL) were lower than the other rodents. Their arterial blood and venous blood pH were 7.46+/-0.07 and 7.27+/-0.07. Oxygen pressure in arterial blood of plateau zokors was about 1.5 times higher than that of pikas and rats, and it was 0.36 and 0.26 times in their venous blood. Partial pressure for carbon dioxide in arterial and venous blood of plateau zokors was 1.5-fold and 2.0-fold higher, respectively, than in rats and pikas. Oxygen saturation of plateau zokors was 5.7 and 9.3 times lower in venous blood than that of pikas and rats, respectively. As result, the difference of oxygen saturation in arterial blood to venous blood was 2- and 4.5-fold higher in plateau zokors as that of pikas and rats, respectively. In conclusion, plateau zokors had a high tolerance to pH changes in tissues, together with strong capabilities to obtain oxygen from their hypoxic-hypercapnic environment.

This issue of Acta

The rather striking cover photograph on this issue of the journal shows gonioscopy images before and after Avastin® injection in a patient with neovascular glaucoma (Paula et al. in this issue). The editorial in this issue discusses the use and abuse of numbers in data values, in particular the excessive use of decimals when mean values are calculated. Professor Sven Erik G. Nilsson, recipient of the 2006 Acta Ophthalmologica Honorary Award, reflects on the journey he and his fellow scientists have made through the wonderlands of eye research. Massin et al., from Paris, review the use of optical coherence tomography in the evaluation of diabetic macular oedema and propose the technique as a key tool in the management of the condition. Pedersen et al., of Copenhagen and Reykjavik, found that optic nerve pH is slightly lower than arterial blood pH and both change in tandem. Optic nerve oxygen tension is influenced by CO2 concentration, but not by pH alone. German authors Huber et al. found increased blood flow velocity in the ophthalmic and central retinal arteries in normal subjects under hypercapnia. Contrast sensitivity was also improved by hypercapnia. Hacioğu et al., Turkey, found that polyunsaturated fatty acids have a beneficial effect on the visual evoked potentials in hypertensive rats. Swedish researchers Lundström et al. have designed a new clinical tool for evaluating indications for cataract surgery. The tool takes into account the objective measurements of visual acuity and the patient's subjective evaluation of visual function. Oslo-based Liv Drolsum found deep sclerectomy to be a safe and effective procedure in pseudoexfoliative glaucoma; the beneficial effect of the surgery lasts several years. Rekonen et al., Kuopio, also studied deep sclerectomy, in both primary open-angle and pseudoexfoliative glaucoma. They found deep sclerectomy to be equally effective in both conditions. Oliveira et al., based in New York and Erlangen, found evidence of exfoliation material in the middle-aged offspring of patients with pseudoexfoliation syndrome, thus substantiating the hereditary character of the syndrome. Slettedal et al., Oslo, used scanning electron microscopy to study the epithelium in donor corneas and found progressive epithelial cell loss with time. However, a healthy rim of peripheral epithelial cells remained, even after a week. Antwerp-based Verhelst et al. reviewed 107 cases of contact lens-related corneal ulcers and found severe ulcers requiring hospitalization to be an increasing problem in Belgium. Puell et al., writing from Madrid, found that dry eyes significantly impair contrast sensitivity. Japanese researchers Uchino et al. report the first child case of pseudomembranous conjunctivitis in acute graft versus host disease after stem cell transplantation. Mehta et al., London, describe subconjunctival crystals in paediatric blepharokeratoconjunctivitis, a condition that has not previously been reported in children. Finnish authors Leinonen et al. examined the variability of refractive error measurements and found it to be greater in eyes with lower visual acuity. Sadeghi et al., based in Sweden and the USA, examined the progressive loss of visual acuity and visual fields that begins in the second and third decades of life in both types 1 and 2 Usher syndrome. Gränse, writing from Lund, suggests that multifocal visual evoked potentials may be useful in evaluating the acute phase of Leber's hereditary optic neuropathy. Mauget-Faÿsse et al., Lyon, present a case of photodynamic therapy for choroidal metastasis from lung adenocarcinoma in the diagnosis/therapy section. Two letters report the use of Avastin. Paula et al., from Brazil, used Avastin successfully in neovascular glaucoma; the cover figure on the journal comes from this study. German practitioners Spandau et al. present a case of macular oedema due to central retinal vein occlusion where Avastin was helpful. The abstracts for the International Perimetric Society's 17th Visual Field and Imaging Symposium are printed in this issue. I hope that this issue of Acta proves to be both pleasurable and educational.

Optic nerve pH and PO2: the effects of carbonic anhydrase inhibition, and metabolic and respiratory acidosis

Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of this effect was either a CO(2) increase or a pH decrease in tissue and blood. To test this hypothesis we investigated and compared how optic nerve pH (ONpH) and ONPO(2) are affected by: (1) carbonic anhydrase inhibition; (2) respiratory acidosis, and (3) metabolic acidosis. We measured ONpH with a glass pH electrode and ONPO(2) with a polarographic oxygen electrode. One of the electrodes was placed in the vitreous cavity 0.5 mm over the optic nerve in the eyes of domestic pigs. We measured ONpH during carbonic anhydrase inhibition and ONpH or ONPO(2) during NH(4)Cl-induced metabolic acidosis and during CO(2) breathing (respiratory acidosis). Baseline ONpH was 0.12 +/- 0.06 lower than arterial pH (mean +/- SD, n = 10, p < 0.001). Optic nerve pH decreased with arterial pH during carbonic anhydrase inhibition, metabolic and respiratory acidosis. Optic nerve oxygen tension was not affected by metabolic acidosis but increased during CO(2) breathing, as it has been shown to do during carbonic anhydrase inhibition. There is a close correlation between arterial blood pH and intraocular pH. Isolated ONpH changes do not affect ONPO(2), thus the ONPO(2) increase seen with carbonic anhydrase inhibition is probably not only due to pH changes in the blood and optic nerve. Accumulation of CO(2), either alone or in combination with a pH change, is likely to cause the ONPO(2) increase, but a direct vascular effect should also be considered.