Continuous 24-hour intragastric pH monitoring. A new model of interpretation]

Using the study as a basis for a novel interpretation of the pH-metric curve, the paper reports the results of a study carried out in a sample group of 11 normo-secretory subjects (students from the Faculty of Medicine and Surgery). The pH-metric curve was assessed over 24 hours using a portable pH measuring device.     

Continuous monitoring of muscle gas tensions and pH during tissue acid-base disturbances

To evaluate the applicability of continuous muscle P_O2 and P_CO2 monitoring as indicators of physiologic abnormalities, muscle (m) P_O2 and P_CO2 was measured by mass spectrometry and pH by muscle surface probe in the limb muscle of 16 dogs subjected to hemorrhage, acid infusion, hypoxia, or hypocarbia and hypercarbia. These values were compared to arterial (a) pH, P_O2, and P_CO2.During hemorrhage, mP_O2 fell sharply; mP_CO2 rose and mpH decreased linearly in proportion to the rate and the magnitude of the bleed. mP_O2 fell with the onset of blood loss, whereas significant mP_CO2 and mpH changes resulting from tissue acidosis were evident only after a large volume loss.Metabolic acidosis produced by acid infusion caused a parallel drop in arterial and mpH, a rise in mP_CO2, and no change in mP_O2.During progressive hypoxia, aP_O2 and mP_O2 reflected the changes in inspired O₂. MpH and apH fell only when mP_O2 fell to low levels. Hypercarbia and hypocarbia caused parallel changes in mP_CO2 which were also reflected in apH and mpH.Continuous muscle gas measurements appear feasible and combined with muscle pH monitoring should help the clinician pinpoint the cause of physiologic derangements in the critically ill.     

Continuous monitoring of gas exchange and oxygen use with dual oximetry

The utility of integrated pulse and pulmonary artery oximetry, known as dual oximetry, was evaluated by monitoring 10 critically ill surgical patients for a total of 208 patient hours. The ventilation-perfusion index (VQI), an estimate of venous admixture, and the oxygen extraction index (O2EI), an estimate of tissue oxygen utilization coefficient, previously described, were calculated on-line from arterial and mixed venous oxyhemoglobin saturations using a computer. Effective monitoring was accomplished 85% of the total time. The dual oximetry device was nonfunctional owing to equipment failure only 15% of the time, even though no undue attention was given to instructing the staff on operation of the oximeters. Accuracy of VQI and O2EI was reconfirmed by this study. Drift in the saturations, VQI, and O2EI during the 6-h period between calibrations was negligible. The 95% range of random variability was +/- 2% for SaO2, +/- 3% for SvO2, +/- 5% for VQI, and +/- 0.04 for O2EI. Thirty-six episodes of arterial blood desaturation below 90% were detected by continuous oximetry. In contrast, 74 routine arterial blood samples revealed only four such episodes. Dual oximetry appears to be a technically reliable and accurate method of monitoring pulmonary gas exchange and tissue oxygen utilization. The equipment provided stable readings for at least six hours without recalibration. Random variability is sufficiently small to allow early detection of alterations in pulmonary and circulatory function without blood sampling.     

Continuous monitoring of bladder and urethral pressures: new technique

A new technique for continuous monitoring of intravesical and intraurethral pressures was developed and utilized in a group of male patients to overcome the disadvantages associated with previously employed liquid and air-coupled systems. This technique permitted recording under physiologic conditions and provided information on a continuous basis concerning changes in the intravesical and intraurethral pressures in patients with multiple urologic symptoms. With further modifications this technique promises to further our understanding of the dynamics of the lower urinary tract under various conditions of stress.     

Continuous direct tissue oxygen tension measurement. A new application for an intravascular oxygen sensor

An oxygen tension measurement equipment, developed for continuous intravascular monitoring was tested as a direct tissue oxygen tension meter. The sterile disposable oxygen probe consists of a Clark type polaro-graphic bipolar electrode placed in a 5 cm long flexible polyethylene catheter (OD 0.55 mm). The probe is easily placed, e.g. in subcutaneous tissue or muscle, with the aid of an introduction needle. In vitro measurements as well as subcutaneous and intramuscular readings were performed. The animals were subjected to various experimental conditions such as different inspiratory oxygen fractions, hypovolemia, and circulatory impairment. Results were comparable to those obtained with previously used and well characterized tissue oxygen tension measurement equipment. The clinical applicability of the oxygen sensor for tissue oxygen measurement was assessed in one patient by 40 hours' surveillance in a free myocutaneous flap. The procedure was simple and implied minimal discomfort for the patient.     

Continuous monitoring of brain tissue oxygen pressure in patients with severe head injury during moderate hypothermia.

BACKGROUND: We studied the change of brain tissue oxygen pressure (PbrO2) value within 24 hours after trauma and during moderate hypothermia in patients with severe head injury. The PbrO2 value was used to differentiate patients at risk of brain ischemia and to predict outcome. METHODS: A flexible microcatheter to be used for continuous monitoring of brain tissue oxygen was inserted into the normal frontal white matter, along with a thermocouple, in 14 patients with severe head injury within 1.5-12 hours (mean 6.1 +/- 5.2 hours) after trauma. Moderate hypothermia was also used within 24 hours in these patients. RESULTS: (1) No complications related to the microcatheter were seen. (2) Low initial PbrO2 values (mean values <10 mmHg) were noted after severe head injury. (3) The occurrence of low initial PbrO2 values (< or = 5 mmHg) was significantly correlated with a poor outcome. (4) Moderate hypothermia can increase PbrO2, but hyperventilation reduced PbrO2. (5) The difference between RT and BT increased during moderate hypothermia. CONCLUSIONS: The PbrO2 values were low in severe head injury, but hypothermia may improve these values. The technique of continuously monitoring brain tissue oxygen pressure may give better insight into cerebral oxygenation and warn of impending ischemia of brain tissue, especially in patients treated with hyperventilation. It will help to improve the management and final outcome of patients with severe head injuries.     

Continuous compartment pressure monitoring vs. clinical monitoring in tibial diaphyseal fractures

A cohort of 109 consecutive patients with a tibial fracture who underwent continuous compartment pressure monitoring of the anterior compartment of the leg were reviewed and compared to a historical control group of the immediate previous 109 patients who were clinically monitored. Of these patients 33 underwent fasciotomies for acute compartment syndrome in association with tibial diaphyseal fractures. Seventeen patients had continuous compartment pressure monitoring and 16 clinical assessments alone. The fasciotomy rate of patients who underwent continuous compartment pressure monitoring was 15.6%. Patients who were not monitored had a fasciotomy rate of 14.7%. The mean time delay from injury to fasciotomy was 22h in the monitored group and 23h in the non-monitored group. Continuous compartment pressure monitoring did not increase the rate of unnecessary fasciotomies. We could not demonstrate a significant difference in terms of clinical outcome and time delay from injury to fasciotomy.     

The relationship between muscle surface pH and oxygen transport.

The relationship between muscle surface pH (pHM) and the arterial-venous oxygen content difference (AVO2D) was studied in 4 patients undergoing reconstructive arterial surgery and in 6 patients undergoing acute normovolemic hemodilution. There was a consistent inverse relation between pHM in the ischemic lower extremity and the femoral AVO2D before, during and after aortic clamping. There was also an inverse relation between AVO2D and pHM during hemodilution. These data confirm that pHM is a reliable indicator of tissue perfusion and correlates with the AVO2D.     

Continuous monitoring of jugular venous oxygen saturation in head-injured patients.

The continuous measurement of jugular venous oxygen saturation (SjvO2) with a fiberoptic catheter is evaluated as a method of detecting cerebral ischemia after head injury. Forty-five patients admitted to the hospital in coma after severe head injury had continuous and simultaneous monitoring of SjvO2, intracranial pressure, arterial oxygen saturation, and end-tidal CO2. Cerebral blood flow, cerebral metabolic rates of oxygen and lactate, arterial and jugular venous blood gas levels, and hemoglobin concentration were measured every 8 hours for 1 to 11 days. Whenever SjvO2 dropped to less than 50%, a standardized protocol was followed to confirm the validity of the desaturation and to establish its cause. Correlation of SjvO2 values obtained by catheter and with direct measurement of O2 saturation by a co-oximeter on venous blood withdrawn through the catheter was excellent after in vivo calibration when there was adequate light intensity at the catheter tip (176 measurements: r = 0.87, p less than 0.01). A total of 60 episodes of jugular venous oxygen desaturation occurred in 45 patients. In 20 patients the desaturation value was confirmed by the co-oximeter. There were 33 episodes of desaturation in these 20 patients, due to the following causes: intracranial hypertension in 12 episodes, hypocarbia in 10, arterial hypoxia in six, combinations of the above in three, systemic hypotension in one, and cerebral vasospasm in one. The incidence of jugular venous oxygen desaturations found in this study suggests that continuous monitoring of SjvO2 may be of clinical value in patients with head injury.     

A new technique for the in vitro measurement of nucleus pulposus swelling pressure.

Swelling of the intervertebral disc nucleus pulposus may be a contributing factor in lower back pain syndromes. We have designed and tested a new osmometer for in vitro determination of nucleus pulposus swelling pressure. The functional principle of the osmometer involves compressing a sample of nucleus pulposus with nitrogen gas until saline pressure gradients across a 0.45-micron Millipore filter are eliminated. Swelling pressures of both pooled dog and pooled pig lumbar disc nucleus pulposus were measured on the new osmometer and were compared with swelling pressure determined using the equilibrium dialysis technique. The osmometer measured swelling pressures comparable to those obtained by the dialysis technique. This osmometer provides a rapid, direct, and accurate measurement of swelling pressure of the nucleus pulposus.     

Continuous intraventricular pressure monitoring for diagnosis of normal-pressure hydrocephalus

Summary Objectives. Normal-pressure hydrocephalus (NPH) syndrome is treatable by implantation of a cerebrospinal fluid (CSF) shunt. However, diagnosis of NPH by clinical and radiological findings alone is unreliable, and co-existing structural dementia can contribute to low success rates after shunt implantation. The aim of our study was to investigate whether long-term results after shunt implantation in NPH improve when surgical candidates are selected by continuous intraventricular pressure monitoring (CIPM). Patients and methods. Ninety-two consecutive patients who were admitted with suspected NPH received CIPM for 48 h including an intraventricular steady-state infusion test to determine the resistance outflow. With positive CIPM, shunt implantation was performed and the patients were prospectively followed up for 1 to 10 years (median 6.5 years). Results. CIPM was negative in 37 patients. Fifty-five patients had a positive CIPM and received CSF shunt. 96.1% of them improved from gait disturbance, 77.1% from cognitive impairment and 75.7% from urinary dysfunction. Clinical improvement remained during long-term follow-up in all but 3 patients who showed a decline at 4, 5 and 7 years, respectively. CIPM-related complications (ventriculitis) occurred in only one patient. Conclusion. CIPM is a safe and valuable tool to establish a reliable diagnosis of NPH and to identify promising surgical candidates.     

A practical technique for continuous monitoring of cerebral tissue pressure in neurosurgical patients

Summary A new technique for continuous monitoring of cerebral tissue pressure is presented. It is based on a new type of piecoresistive microtransducer with low baseline and temperature drifts. In 7 patients cerebral tissue pressure and ventricular fluid pressure were recorded simultaneously.Comparison of these two different pressures showed extremely good correlation with coefficients always better than 0.95. Due to another type of pulsewave cerebral tissue pressure was constantly 4 to 12 mm Hg lower than ventricular fluid pressure. Routine use of cerebral tissue monitoring in 12 neurosurgical patients with brain tumours postoperatively showed good clinical correlation of cerebral tissue pressure without any additional complications.The authors recommend continuous monitoring of cerebral tissue pressure as a safe and simple method of intracranial pressure monitoring in neurosurgery.     

Dialysis-induced hypoxemia. Continuous monitoring of blood oxygen and carbon dioxide tension in children

We report our experience with continuous, transcutaneous monitoring of capillary oxygen and carbon dioxide tension (PtcO2, PTlcCO2 ) during the entire length of hemodialysis treatment in 8 pediatric patients. The relative changes in PtcO2 and PtcCO2 observed with this method were in accordance with those reported in the literature, obtained with frequent arterial blood sampling. There was a temporary fall of PtcO2, averaging 26.2% after 2h of dialysis, with a concomitant rise of PtcCO2 of 9.9%. The noninvasive, transcutaneous measurement of PtcO2 and PtcCO2 is a reliable and valuable adjunct for the monitoring of the dialysis patient who is prone to develop hypoxemia. It is particularly useful in the very young.     

A new technique for the transurethral or percutaneous removal of renal stones

This new technique uses a cystoscopically placed torque guide wire and catheters to deliver a stone basket to the renal calix containing the stone. Under fluoroscopic control the basket, placed through a 9F catheter, is used to dislodge and capture the stone. The stone-containing basket and catheter then are removed transurethrally or percutaneously. This procedure was used to remove small caliceal stones in 3 patients undergoing ureteral stone manipulation, and it facilitated the percutaneous removal of a larger stone in the upper pole infundibulum in 1 patient.