Harry Roth

Effects of hypervolemia and hypertension on regional cerebral blood flow, intracranial pressure, and brain tissue oxygenation after subarachnoid hemorrhage.

Objective:Hypertensive, hypervolemic, hemodilution therapy (triple-H therapy) is a generally accepted treatment for cerebral vasospasm after subarachnoid hemorrhage. However, the particular role of the three components of triple-H therapy remains controversial. The aim of the study was to investigate the influence of the three arms of triple-H therapy on regional cerebral blood flow and brain tissue oxygenation. Design:Animal research and clinical intervention study. Setting:Surgical intensive care unit of a university hospital. Subjects and Patients:Experiments were carried out in five healthy pigs, followed by a clinical investigation of ten patients with subarachnoid hemorrhage. Interventions:First, we investigated the effect of the three components of triple-H therapy under physiologic conditions in an experimental pig model. In the next step we applied the same study protocol to patients following aneurysmal subarachnoid hemorrhage. Mean arterial pressure, intracranial pressure, cerebral perfusion pressure, cardiac output, regional cerebral blood flow, and brain tissue oxygenation were continuously recorded. Intrathoracic blood volume and central venous pressure were measured intermittently. Vasopressors and/or colloids and crystalloids were administered to stepwise establish the three components of triple-H therapy. Measurements and Main Results:In the animals, neither induced hypertension nor hypervolemia had an effect on intracranial pressure, brain tissue oxygenation, or regional cerebral blood flow. In the patient population, induction of hypertension (mean arterial pressure 143 ± 10 mm Hg) resulted in a significant (p < .05) increase of regional cerebral blood flow and brain tissue oxygenation at all observation time points. In contrast, hypervolemia/hemodilution (intrathoracic blood volume index 1123 ± 152 mL/m2) induced only a slight increase of regional cerebral blood flow while brain tissue oxygenation did not improve. Finally, triple-H therapy failed to improve regional cerebral blood flow more than hypertension alone and was characterized by the drawback that the hypervolemia/hemodilution component reversed the effect of induced hypertension on brain tissue oxygenation. Conclusions:Vasopressor-induced elevation of mean arterial pressure caused a significant increase of regional cerebral blood flow and brain tissue oxygenation in all patients with subarachnoid hemorrhage. Volume expansion resulted in a slight effect on regional cerebral blood flow only but reversed the effect on brain tissue oxygenation. In view of the questionable benefit of hypervolemia on regional cerebral blood flow and the negative consequences on brain tissue oxygenation together with the increased risk of complications, hypervolemic therapy as a part of triple-H therapy should be applied with utmost caution.

Effect of Intra-Arterial Papaverine on Regional Cerebral Blood Flow in Hemodynamically Relevant Cerebral Vasospasm

Background and Purpose — It remains controversial whether the intra-arterial administration of papaverine (IAP) is effective in reversing vasospasm-associated cerebral hypoperfusion after aneurysmal subarachnoid hemorrhage. The aim of the present study was to continuously assess regional cerebral blood flow (rCBF) during and after IAP with the use of quantitative, bedside thermal diffusion flowmetry. Methods — Eight patients with cerebral vasospasm after subarachnoid hemorrhage (mean flow velocity >120 cm/s; angiographic vessel constriction >33%; hemispheric cerebral blood flow [CBF] <32 mL/100 g per minute) were prospectively entered into the study. Before IAP, thermal diffusion microprobes were implanted into the white matter of each affected vascular territory (n=10) for rCBF monitoring. During and after IAP (300 mg papaverine/50 mL saline over 1 hour), mean arterial blood pressure, intracranial pressure, cerebral perfusion pressure, thermal diffusion rCBF (TD-rCBF), and cerebrovascular resistance (CVR) were recorded continuously. Results — IAP significantly increased TD-rCBF from 7.3±1.6 to 37.9±6.6 mL/100 g per minute (mean±SEM), indicating reversal of cerebral hypoperfusion. This TD-rCBF response was dependent on the degree of cerebral vasospasm and reduced perfusion within the vascular territory. Long-term analysis of TD-rCBF, however, demonstrated that this beneficial effect of IAP on cerebral hypoperfusion was only transient: within 3 hours after treatment, TD-rCBF and CVR returned to baseline values. Furthermore, a lack of correlation between transcranial Doppler sonography and thermal diffusion flowmetry suggested that transcranial Doppler sonography is not suited for CBF-based neuromonitoring after IAP. Conclusions — IAP is not effective in permanently reversing cerebral hypoperfusion in patients with cerebral vasospasm. The need to validate alternative therapeutic strategies that seek to improve cerebral perfusion in vasospasm warrants continued development of CBF-based neuromonitoring strategies.

Rapid active internal core cooling for induction of moderate hypothermia in head injury by use of an extracorporeal heat exchanger.

OBJECTIVE Moderate hypothermia (32 degrees C) may limit postischemic neuronal damage and is increasingly used clinically in head injury and stroke. For the use of hypothermia as a neuroprotective agent in the prevention of ischemic damage, it is necessary to induce it as soon as possible after the insult and to keep it at the lowest safe level. Active core cooling using an extracorporeal heat exchanger may circumvent the rather slow induction speed and temperature drifts experienced with surface cooling techniques. METHODS In eight patients with severe head injuries (Glasgow Coma Scale score, 4-5), a venovenous extracorporeal circulation was established via a percutaneously introduced double-lumen cannula in the femoral vein. A heat exchanger was connected via a pressure-controlled roller pump. In addition to standard parameters, brain white matter temperature was continuously recorded as the target temperature. Cooling was initiated as early as possible with an extracorporeal temperature of 30 degrees C and maintained at a 32 degrees C brain temperature for 48 hours, and then gradual rewarming for 24 hours. RESULTS Cooling was able to be initiated within 6 hours and 48 minutes +/- 3 hours and 47 minutes (mean +/- standard deviation) after trauma. A brain temperature of 32 degrees C was reached within 1 hour and 53 minutes +/- 1 hour and 21 minutes after induction of cooling with a cooling speed of 3.5 degrees C per hour. Brain temperature was able to be controlled within 0.1 degrees C intervals, which was especially helpful in gradual rewarming. No cardiac abnormalities or statistically significant changes in coagulation parameters occurred. Mean platelet count decreased to 89,614+/-42,090 on Day 3 after treatment. No clinical bleeding complications or problems resulting from extracorporeal circulation occurred. Moderate hypothermia was a helpful tool for managing increased intracranial pressure; however, five patients of this series died either of their intracranial abnormalities (n = 4) or of a delayed septic shock after pneumonia (n = 1) at various points in time during therapy. The three survivors experienced either an excellent or a good recovery. CONCLUSION The results of this investigation suggest that the use of an extracorporeal heat exchanger to achieve active core cooling is suitable for fast and accurately controllable induction, maintenance, and reversal of moderate hypothermia in emergency situations with reliable control of temperature. In this small series of highly selected patients with severe head injuries, we did not note a beneficial effect of hypothermic therapy on outcome.

The ProSeal laryngeal mask airway and the laryngeal tube Suction for ventilation in gynaecological patients undergoing laparoscopic surgery.

Background and objective: ProSeal™ Laryngeal Mask Airway (PLMA) and Laryngeal Tube Suction™ (LTS), supraglottic airway devices allowing gastric drainage, were compared in this prospective, randomized study for airway management under conditions with elevated intra‐abdominal pressure induced by capnoperitoneum. Methods: Fifty patients undergoing elective gynaecological laparoscopic surgery were randomized to two groups of 25 each. After induction of general anaesthesia, devices were inserted, correct placement was verified, airway leak pressure was measured, and a gastric tube was inserted. Ease of insertion, quality of airway seal, risk of gastric insufflation and patient comfort were investigated. Results: There were no differences in patient characteristics data for both groups. First‐time insertion success rates were comparable for both groups: 92% ‐ first attempt, 8% ‐ second attempt for PLMA and LTS. Time until delivery of the first tidal volume for PLMA and LTS was 23.2 ± 6.1 and 23.5 ± 6.6 s, airway leak pressure was 45.4 ± 4.9 cmH2O and 45.6 ± 6.7 cmH2O with cuff pressures adjusted to 60 cmH2O. No gastric insufflation, gas loss or signs of regurgitation were detected. Placement of a gastric tube was successful in all patients. Patients were questioned for sore throat and dysphagia after removal of devices. Sore throat was stated in 1%/0% (PLMA) and 8%/4% (LTS) after 6/24 h, dysphagia in 4%/4% (PLMA) and 12%/4% (LTS). Conclusions: Both devices provide a secure airway even under conditions of elevated intra‐abdominal pressure. In this pilot study, no differences concerning handling or quality of airway seal were detected between PLMA and LTS.

Therapy of malignant intracranial hypertension by controlled lumbar cerebrospinal fluid drainage.

ObjectivesTo evaluate the effect of controlled lumbar cerebrospinal fluid drainage in adult patients with refractory intracranial hypertension. DesignProspective, pre- vs. postintervention study. SettingSurgical intensive care unit of a university hospital. PatientsTwenty-three patients with severe traumatic brain injury or delayed ischemia after subarachnoid hemorrhage with intracranial hypertension refractory to aggressive treatment, including repeated applications of tromethamine, hypertonic saline solution, barbiturate coma, and decompressive craniectomy. Patients were considered for controlled lumbar cerebrospinal fluid drainage if basal cisterns on computerized tomography scan were discernible. InterventionsAfter institution of a lumbar drain, cerebrospinal fluid was gradually aspirated, and then, continuous cerebrospinal fluid drainage was maintained under control of intracranial pressure (ICP) and pupillary status. Measurements and Main Results ICP and cerebral perfusion pressure before and after initiation of lumbar cerebrospinal fluid drainage and related complications were documented. The neurologic outcome of the patients was assessed according to the Glasgow Outcome Scale 6 months after injury. As a result of lumbar cerebrospinal fluid drainage, all patients demonstrated an immediate and lasting decrease of ICP and a concomitant increase of cerebral perfusion pressure. Two patients temporarily showed a unilateral fixed and dilated pupil 6 and 8 hrs after onset of lumbar cerebrospinal fluid drainage, respectively. Ten patients showed a favorable outcome, four patients survived with a severe permanent neurologic deficit, one patient remained in a persistent vegetative state, and eight patients died. ConclusionsControlled lumbar cerebrospinal fluid drainage significantly reduces refractory intracranial hypertension. The danger of transtentorial or tonsillar herniation is minimized by considering lumbar drainage in the presence of discernible basilar cisterns only.

predictors of mortality in Ards patients referred to a tertiary care centre : a pilot study

Background and objective: In order to identify parameters predicting intensive care unit mortality in patients transferred to a specialized tertiary centre because of progressive acute respiratory distress syndrome, an observational pilot study was carried out involving 94 patients. Methods and Results: Forty‐one patients (43.6%) died. Survival was defined as intensive care unit discharge. Survivors were younger (32.0 ± 11.8 vs. 39.1 ± 12.4 yr, P = 0.008), at admission they had a lower acute physiology and chronic health evaluation (APACHE) II score (21.7 ± 5.4 vs. 25.4 ± 5.2, P = 0.0009), higher PaO2/FiO2 (122 ± 79 vs. 79 ± 42 mmHg, P = 0.002), lower positive end‐expiratory pressure (10.6 ± 3.1 vs. 12.5 ± 3.7 cmH2O, P = 0.02) and a lower Murray score (2.8 ± 0.63 vs. 3.0 ± 0.62, P = 0.04). No differences were observed for tidal volumes and peak inspiratory pressures. Days of hospitalization and mechanical ventilation prior to transferral were not related to survival. Multivariate analysis of variables assessed on admission detected only differences for age (P = 0.014) and APACHE II (P = 0.005). Odds ratio was 1.06 (95% confidence interval (CI): 1.013–1.119) for age and 1.21 (CI: 1.059–1.381) for APACHE II. Multivariate analysis of changes in respiratory parameters, APACHE II and Murray score during the first 3 days after transferral revealed a significant difference only for positive end‐expiratory pressure (P < 0.008). Corresponding odds ratio was 2.40 (CI: 1.25–4.58) for an increase of 1 cmH2O/24 h. Conclusion: Age‐related mortality in this small, but highly selected group of patients with established ARDS increased early in life even in a population with an overall mean age of 35.1 yr. APACHE II was the only clinical predictor for mortality on admission. The need for a substantial increase in positive end‐expiratory pressure after transferral markedly reduced the chance to survive.

Effects of end-inspiratory and end-expiratory pressures on alveolar recruitment and derecruitment in saline-washout-induced lung injury – a computed tomography study

Background:  Lung protective ventilation using low end‐inspiratory pressures and tidal volumes (VT) has been shown to impair alveolar recruitment and to promote derecruitment in acute lung injury. The aim of the present study was to compare the effects of two different end‐inspiratory pressure levels on alveolar recruitment, alveolar derecruitment and potential overdistention at incremental levels of positive end‐expiratory pressure.

Pulmonary gas distribution during ventilation with different inspiratory flow patterns in experimental lung injury – a computed tomography study

Background:  There is still controversy about the optimal inspiratory flow pattern for ventilation of patients with acute lung injury. The aim of this study was to compare the effects of pressure‐controlled ventilation (PCV) with a decelerating inspiratory flow with volume‐controlled ventilation (VCV) with constant inspiratory flow on pulmonary gas distribution (PGD) in experimentally induced ARDS.

Tracheostomy for the critically ill: impact of new technologies

Tracheostomy in critically ill patients offers a number of practical and theoretical advantages compared with conventional translaryngeal orotracheal or nasotracheal intubation. Recent reports suggest that it might be possible to identify factors that allow physicians to determine which patients will be most likely to benefit from tracheostomy. However, the appropriate timing still remains controversial. A body of evidence exists that indicates that tracheostomy in intensive care patients, regardless of the method chosen, should be performed at the bedside. The technique of percutaneous dilatational tracheostomy has been studied in many patients, demonstrating an at least comparable rate of perioperative and a lower rate of postoperative complications compared with conventional open surgical tracheostomy. Based on these results, and taking into account the fact that the use of percutaneous dilatational tracheostomy in the intensive care setting offers some additional logistic advantages, it is the first line method for critically ill patients.

Bedside monitoring of cerebral blood flow by transcranial thermo-dye-dilution technique in patients suffering from severe traumatic brain injury or subarachnoid hemorrhage

Bedside measurement of cerebral blood flow (CBF) represents an important feature in monitoring of neurointensive care patients which is hard to establish. Therefore, we adopted a recently described thermo-dye-dilution-based approach for monitoring CBF in patients suffering from severe cerebral insults, that is, traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Combined fiberoptic-thermistor catheters were placed in one jugular venous bulb and in the abdominal aorta of 16 patients. Following central venous injection of a 50-mL bolus of precooled indocyanine green (ICG) solution, CBF was determined as a function of the mean transit times of coldness and dye. In addition, measurements of CBF using stable xenon-enhanced computerized tomography (sXe-CT) were simultaneously performed in 10 patients. A total of 272 thermo-dye-dilution measurements yielded 196 valid results, with CBF ranging from 26.2 to 144.8 mL 100 g(-1) min(-1). Reproducibility was fairly good, with the standard deviation within sets of repeated measurements being 6.3 mL 100 g(-1) min(-1) and 9.4 as the mean coefficient of variation. Simultaneously obtained values with sXe-CT displayed a good correlation (r = 0.843, p < 0.01); however, the thermo-dye-dilution method consistently overestimated CBF. Data analysis using the Bland and Altman methodology revealed a large bias of 45.7 mL 100 g(-1) min(-1) with a +/- 2 SD range of 37 mL 100 g(-1) min(-1), indicating a rather poor agreement. The thermo-dye-dilution method proved a reasonably reproducible technique, enabling repeated long-term bedside measurements of CBF in neurointensive care patients with a minimum of time effort. However, a high failure rate was also noted, and consistent overestimation of perfusion was observed in comparison to sXe-CT measurements. Although the thermo-dye-dilution technique has been successfully validated in patients with normal neurovascular function, its applicability for bedside monitoring of CBF appears uncertain in patients suffering from severe TBI or SAH.