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Continuous measurements of mean arterial pressure (MAP), ICP, and jugular venous oxygen saturation (SjO2) were performed in 11 patients with severe head injury (GCS 3-7) to assess the dependence of SjO2 from the cerebral perfusion pressure (CPP), trying to establish an indirect measure of cerebrovascular autoregulation. Changes in CPP resulting from spontaneous fluctuations in MAP or ICP induced highly significant alterations in SjO2 in the range of 0.14-0.56% SjO2 mmHg-1 CPP in all patients and all periods after trauma. The analysis of the distribution of the SjO2:CPP-ratios showed the highest frequency of values in the range of 0.0-0.25% SjO2 mmHg-1 CPP in 9 of the 11 patients. Within the first 2 days after trauma, a more pronounced dependency of SjO2 from changes in CPP was found, but this was not statistically significant. No predictable relationship of the SjO2:CPP-ratio to the level of ICP could be demonstrated in the patients. Because changes in SjO2 induced by alterations in CPP were found in all patients and throughout the acute phase of severe head injury, these changes more probably reflect physiological alterations in CBF with varying perfusion pressure rather than impaired autoregulation after head trauma. Although assessment of cerebral autoregulation by estimation of the SjO2:CPP-ratio offers new possibilities for monitoring of these patients, the high frequency of erroneous readings or irregular fluctuations of the SjO2-signal from the fibreoptic catheter limits the usefulness of the SjO2-dependency from CPP for practical use in the intensive care unit.
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PMID:Correlation of jugular venous oxygen saturation to spontaneous fluctuations of cerebral perfusion pressure in patients with severe head injury. 858 22

Jugular venous oxygen saturation (SjvO2) measures the balance between cerebral oxygen delivery and cerebral oxygen consumption. Abnormalities that increase oxygen consumption (e.g., fever or seizures) or that decrease oxygen delivery (e.g., increased ICP, hypotension, hypoxia, hypocapnia, or anemia) can decrease SjvO2. Measuring SjvO2 continuously in the ICU in 177 patients with severe head injury, jugular venous desaturation (SjvO2 < 50%) was identified at least once in 39% of the patients. Approximately half of the episodes of desaturation were due to intracranial hypertension and half were due to systemic causes. The occurrence of one or more episodes of desaturation was strongly associated with a poor outcome, suggesting that the reduction in oxygen delivery identified with the SjvO2 monitoring contributed to the neurological injury. In the operating room, jugular venous desaturation was identified in 6 of 8 patients who were monitored during emergency evacuation of a traumatic intracranial hematoma. The lowest SjvO2 observed was 28%. In all 8 cases, the SjvO2 increased, from 47 +/- 10% to 63 +/- 5% after evacuation of the hematoma. Additional data supporting the hypothesis that these secondary insults identified with the SjvO2 monitoring contribute to the patient's neurological injury come from measurement of the extracellular concentrations of lactate and excitatory amino acids in the brain using microdialysis. Lactate concentration increased from 0.9 +/- 0.3 to 2.4 +/- 0.5 mumol/L and glutamate increased from 11.5 +/- 8.5 to 55.0 +/- 10.4 mumol/L during 8 episodes of jugular venous desaturation in 7 of 22 patients monitored with microdialysis. SjvO2 identifies global reductions in cerebral oxygenation due to a variety of causes, and is useful as a monitor for secondary insults in patients with severe head injury.
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PMID:SjvO2 monitoring in head-injured patients. 859 16

The use of intraparenchymatous ICP sensor is becoming increasingly popular at the expense of the traditional intraventricular catheter method, in spite of the impossibility, with the former technic, to correct a possible zero drift. The decision to initiate or discontinue ICP monitoring is essentially based upon whether suggestive aspects of raised ICP are or not present on CT-scan. The degree of basal cisterns effacement is particularly informative. The same data from successive CT-scans are used to check the validity of the monitoring. Predefining critical levels of ICP and cerebral perfusion pressure (CPP) allows to establish practical guide-lines for treatment. Cerebral ischemia is considered very likely when ICP rises above 30 mmHg. Regarding CPP, the therapeutical goal is to avoid its reduction under the critical level of 60-80 mmHg. As these thresholds vary with the patients age and the type of lesion, a parallel evaluation of cerebral ischemia by other methods is mandatory. Transcranial doppler allows an easy detection of critical reduction of arterial flow. However, in case of flow hypervelocity, interpretation needs measurement of absolute cerebral blood flow values. Cerebral venous oxygen saturation monitoring, at the level of the jugular golf, shows desaturation episodes indicative of cerebral ischemia. Blood sampling for determination of arterial and jugular venous lactate concentrations allows calculation of the lactate oxygen index, a practical correlate of the degree of cerebral ischemia. ICP measurement alone is of limited value to understand the cerebral hemodynamical and metabolical situation in severe brain injury. Preceding the rise of ICP, there exists a compensation phase during which a progressive decrease of intracranial compliance is the important event. Even more earlier, posttraumatic cellular metabolic dysfunctions are to-day objectives for a neurochemical monitoring. Therefore a special technical and human environment has became mandatory to take a real benefit from ICP monitoring.
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PMID:[Monitoring of intracranial pressure]. 876 56

Dihydroergotamine (DHE) is used in our recently introduced therapy of post-traumatic brain oedema and is suggested to reduce ICP through reduction in both cerebral blood volume and brain water content. This study aims at increasing our knowledge of the mechanisms behind the ICP reducing effect of DHE by analysing cerebrovascular effects of a bolus dose of DHE in severely head injured patients (GCS < 8). Mean hemispheric cerebral blood flow (CBF) calculated from the clearance of i.v. 133Xenon, ICP, and cerebral arterio-venous difference in oxygen content (AVDO2), were measured before and after hyperventilation and after a bolus dose of DHE (4 micrograms/kg). The patients were divided into two groups, one with preserved and one with impaired cerebrovascular CO2-reactivity to hyperventilation, the latter being predictive of poor outcome. The haemodynamic effects of DHE were compared to those of hyperventilation. Regional CBF and brain volume SPECT measurements were performed in two patients. DHE increased cerebrovascular resistance (CVR) by about 20% and significantly reduced ICP in both groups of patients, resulting in unchanged AVDO2. Hyperventilation with preserved CO2-reactivity caused a similar decrease in ICP as by DHE but with a much larger increase in CVR (by 70%) and a substantial increase in AVDO2. Hyperventilation with impaired CO2-reactivity reduced ICP but otherwise had no significant cerebrovascular effects. The study supports the concept that the ICP reducing effect of DHE results more from constriction of the large veins than from arterial vasoconstriction, also implying a relatively smaller risk of ischaemia with DHE than with hyperventilation.
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PMID:Cerebral haemodynamic effects of dihydroergotamine in patients with severe traumatic brain lesions. 884 93

A method for determining iodine, bromine, chlorine and fluorine in geological and biological materials is described. In a quartz tube, solid material was heated to 1100 degrees C under a wet oxygen flow (pyrohydrolysis). By this process the halogens (I, Br, Cl, F) were separated from the matrix and then collected in a receiver solution. The chemical yield of iodine was determined by a radioactive tracer. ICP-MS and ion chromatographic measurements were used for the determination of the halogens. The method was optimized by investigating different experimental conditions. All four halogens can be trapped in the receiver solution from one combustion procedure. Precision and accuracy were evaluated by the analysis of environmental standard reference materials (rock, soil, milk, leaves, marine tissue). The concentrations in the materials analysed were in the ranges 0.006-50 mg kg-1 for I, 0.06-1300 mg kg-1 for Br, 50-1100 mg kg-1 for F and 400-11000 mg kg-1 for Cl. The lower values represent the practical detection limit of this method. The results obtained by the proposed method and the certified values are in good agreement.
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PMID:Determination of halogens, with special reference to iodine, in geological and biological samples using pyrohydrolysis for preparation and inductively coupled plasma mass spectrometry and ion chromatography for measurement. 895 50

The efficiency of ruthenium complexes for photosensitizing DNA damage depends on the oxidizing character of their ligands. Here we report on the difference in behavior of tris(2.2'-bipyrazyl)ruthenium(II) (Ru[bpz]3(2+)), tris(2,2'-bipyridyl)ruthenium(II) (Ru[bipy]3(2+)) and cis-dichlorobis (2,2'-bipyrazyl)ruthenium(II) (Ru[bpz]2Cl2). Upon irradiation at 436 nm, Ru(bpz)3 (2+) was far less stable than Ru(bipy)3(2+). Ru(bpz)3(2+) in phosphate buffer containing NaCl undergoes a photoanation reaction leading to the formation of Ru(bpz)2Cl2, as previously reported also in organic media. In the presence of phage phi X174 DNA, Ru(bpz)3(2+) photosensitized the formation of single strand breaks with an efficiency that was, at the beginning of irradiation, similar to that of Ru(bipy)3(2+). After 8 min of irradiation, the cleavage efficiency of Ru(bpz)3(2+) reached a plateau that may correspond to its photode composition. For the same conditions, Ru(bpz)2Cl2 did not induce DNA breakage. Scavenging experiments showed that, in the presence of oxygen, DNA cleavage induced by Ru(bpz)3(2+) partly resulted from the formation of singlet oxygen and hydroxyl radical while in the absence of oxygen an additional mechanism involving electron transfer between the excited state of the ruthenium complex and DNA is proposed. The ICP measurement showed that Ru(bpz)3(2+) and Ru(bpz)2Cl2 gave rise to covalent binding onto DNA in contrast with Ru(bipy)3(2+), which did not bind to DNA under the experimental conditions. The results are discussed with regard to the potential use of these photosensitizers in phototherapy.
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PMID:Comparative study of Ru(bpz)3(2+) Ru(bipy)3(2+) and Ru(bpz)2Cl2 as photosensitizers of DNA cleavage and adduct formation. 911 40

The authors report on the stability and complications of 73 LICOX brain ti-pO2-microcatheters in 70 patients. Mean monitoring time was 7.5 +/- 4.0 days. Patients prone to cerebral hypoxia (after severe head injury (GCS < 9) or a subarachnoid hemorrhage) had a ti-pO2-microcatheter inserted next to the ICP-probe in the typical frontal position. After the first 15 insertions, instead of the 3-way-screw (needing a 6 mm burrhole), a 1-way-screw (needing a 2.7 mm burrhole) was used for fixation in the bone; by doing so, the procedure can be performed in the ICU and takes only 15 min. Whenever possible a calibration at room air (to determine the sensitivity-drift) and in oxygen free solution (to determine the zero-drift) was performed after removal of the catheters. Ideally the expected pO2 at room air was around 154 mmHg (temperature dependent) and at zero calibration 0 mmHg. Mean sensitivity-drift for 54 catheters was -8.5 +/- 15.4%. Dividing the catheters into groups, depending on the duration of monitoring (1-4, 5-8 and 9-16 days), revealed that the greatest part of the (negative) sensitivity-drift occurred during day 1-4 after insertion. After 1 week of monitoring sometimes a positive drift occurred (being far less than the negative drift during the first 4 days). Compared to the old catheters (-10.3 +/- 17.3%) (on the first half of the patients) the new ones showed a lower sensitivity-drift (-6.8 +/- 13.4%). The zero-drift of 56 catheters was low with mean drift after 7.5 +/- 4.0 days of 1.5 +/- 1.5 mmHg. Here also the highest drift occurred on day 1-4 after insertion. No infection was seen and 2 times (2.7%) a small hematoma, not needing evacuation occurred. As the ti-pO2-catheter (having a smaller diameter) and the ICP-catheter were inserted at the same time, one cannot distinguish which catheter caused the hematoma. A possible explanation for the occurrence of the two hematomas is the insertion of the catheters too close to the midline. The authors conclude that LICOX ti-pO2-monitoring is a safe and reliable method. Further decrease of the complication rate and increase of the catheter-stability may be expected.
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PMID:Brain tissue pO2-monitoring: catheterstability and complications. 919 73

The concept of small-volume resuscitation, the rapid infusion of a small volume (4 ml/kg BW) of hyperosmolar 7.2-7.5% saline solution for the initial therapy of severe hypovolemia and shock was advocated more than a decade ago. Numerous publications have established that hyperosmolar saline solution can restore arterial blood pressure, cardiac index and oxygen delivery as well as organ perfusion to pre-shock values. Most prehospital studies failed to yield conclusive results with respect to a reduction in overall mortality. A meta-analysis of preclinical studies from North and South America, however, has indicated an increase in survival rate by 5.1% following small-volume resuscitation when compared to standard of care. Moreover, small-volume resuscitation appears to be of specific impact in patients suffering from head injuries with increased ICP and in severest trauma requiring immediate surgical intervention. Results from clinical trials in Austria, Germany and France have demonstrated positive effects of hyperosmolar saline solutions when used for fluid loading or fluid substitution in cardiac bypass and in aortic aneurysm surgery, respectively. A less positive perioperative fluid balance, a better hemodynamic stability and improved pulmonary function were reported. In septic patients oxygen consumption could significantly be augmented. The most important mechanism of action of small-volume resuscitation is the mobilisation of endogenous fluid primarily from oedematous endothelial cells, by which the rectification of shock-narrowed capillaries and the restoration of nutritional blood, flow is efficiently promoted. Moreover, after ischemia reperfusion a reduction in sticking and rolling leukocytes have been found following hyperosmolar saline infusion. Both may be of paramount importance in the long-term preservation of organ function following hypovolemic shock. An increased myocardial contractility in addition to the fluid loading effects of hyperosmolar saline solutions has been suggested as a mechanism of action. This, however, could not be confirmed by pre-load independent measures of myocardial contractility. Some concerns have been raised regarding the use of hyperosmolar saline solutions in patients with a reduced cardiac reserve. A slower speed of infusion and adequate monitoring is recommended for high risk patients. Recently, hyperosmolar saline solutions in combination with artificial oxygen carriers have been proposed to increase tissue oxygen delivery through enhanced O2 content. This interesting perspective, however, requires further studies to confirm the potential indications for such solutions. Many hyperosmolar saline colloid solutions have been investigated in the past years, from which 7.2-7.5% sodium chloride in combination with either 6-10% dextran 60/70 or 6-10% hydroxyethyl starch 200,000 appear to yield the best benefit-risk ratio. This has led to the registration of the solutions in South America, Austria, The Czech Republic, and is soon awaited for North America.
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PMID:[Small-volume resuscitation for hypovolemic shock. Concept, experimental and clinical results]. 922 85

Simultaneous oxygen measurements in brain tissue (p(ti)O2) and hemoglobin saturation measurement in cerebrovenous blood in patients after severe head injury have shown different results regarding the comparability of the findings in respect to CPP and ICP. This is contrast to theoretical expectations. The aim of this study was to compare continuous ptiO2 measurement with oxygen partial pressure measurement in sagittal sinus (pO2cv) during simultaneously performance in an animal intracranial pressure model. For continuous measurement we used a newly available multisensor probe. We placed a Paratrend 7 probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured ptiO2, pCO2 (ptiCO2) pH (pHti) and temperature (t(ti)) while simultaneously measuring these parameters (pcvO2, pcvCO2, pHcv, tcv) in the sagittal sinus in 9 pigs under general anaesthesia. A fogarty balloon catheter was placed supracerebellar infratentorial and inflated stepwise in order to increase ICP. The baseline levels of pO2ti, pCO2ti und pHti in the non-injured brain tissue showed a more extended heterogeneity compared to the findings in cerebrovenous blood. Both, pO2ti and pO2cv were significant correlated to the CPP decrease. In both measurement compartments pCO2 was inverse correlated to the course of CPP and seems the course of pH mainly to determine. p(ti)O2 as well as p(cv)O2 showed a close correlation to the CPP course and have proven to be qualified to indicate metabolic information about the relation of cerebral blood flow and metabolic cerebral demands. The measurement of CO2 tension in both measurement compartments shows a distinct heterogeneity of the absolute values and the results are only weak correlated to CPP. Metabolic influence on this parameter could not be revealed in the used experimental approach.
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PMID:Comparison between continuous brain tissue measurement and cerebrovenous measurement of pO2, pCO2 and pH in a porcine intracranial pressure model. 940 55

Local brain tissue oxygenation (p(ti)O2) and global cerebrovenous hemoglobin saturation (SjO2) are increasingly used to continuously monitor patients after severe head injury (SHI). In patients, simultaneous local and global oxygen measurements of these types have shown different results regarding the comparability of the findings during changes in CPP and ICP. This is in contrast to theoretical expectations. The aim of this study was to compare p(ti)O2 measurement with cerebrovenous oxygen partial pressure measurement (p(cv)O2) in an animal intracranial pressure model. To this end, a multisensor probe was placed in the left frontoparietal white matter to measure p(ti)O2, pCO2 (p(ti)CO2), pH (pH[ti]), and temperature (t[ti]) while simultaneously measuring these same parameters (p(cv)O2, p(cv)CO2 pH(cv), t[cv]) in the sagittal sinus of 9 pigs under general anesthesia. By stepwise inflating a balloon catheter, placed in supracerebellar infratentorial compartment, ICP was increased and CPP was decreased. The baseline levels of p(ti)O2, p(ti)CO2, and pH(ti) in the noninjured brain tissue showed more heterogeneity compared to the findings in cerebrovenous blood. Both, p(ti)O2 and p(cv)O2 were significantly correlated to the induced CPP decrease. PCO2 was inversely correlated to the course of CPP in both measurement compartments. Temperature measurement showed a positive correlation with CPP in both compartments. These findings demonstrate that brain tissue oximetry and cerebrovenous PO2 measurement are sensitive to CPP changes. The newly available continuous parameters in multisensor probes could be helpful in interpreting findings of cerebral oxygen measurement in man by analyzing the interrelationship of these parameters.
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PMID:Comparison between continuous brain tissue pO2, pCO2, pH, and temperature and simultaneous cerebrovenous measurement using a multisensor probe in a porcine intracranial pressure model. 955 72


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