Julio Cruz

The first decade of continuous monitoring of jugular bulb oxyhemoglobin saturation : Management strategies and clinical outcome

OBJECTIVE To comparatively assess outcome of patients undergoing monitoring and management of cerebral extraction of oxygen along with cerebral perfusion pressure vs. outcome of patients undergoing monitoring and management of cerebral perfusion pressure alone in severe acute brain trauma. DESIGN Prospective, interventional study. SETTING Intensive care unit of a university hospital. PATIENTS Adults (n = 353) with severe acute brain trauma. A group of 178 patients underwent continuous monitoring and management of cerebral extraction of oxygen and cerebral perfusion pressure, while a control group of 175 patients underwent monitoring and management of cerebral perfusion pressure only. INTERVENTIONS Routine neuroemergency procedures. MEASUREMENTS AND MAIN RESULTS The two groups of patients were matched with regard to age, postresuscitation Glasgow Coma Scale scores, rates of acute surgical intracranial hematomas and brain swelling, pupillary abnormalities, early hypotensive events (before intensive care monitoring), as well as initial levels of intracranial pressure and cerebral perfusion pressure. Outcome at 6 months post injury was significantly better (p < .00005) in the 178 patients undergoing monitoring and management of cerebral extraction of oxygen along with cerebral perfusion pressure, than in the control group of 175 patients undergoing monitoring and management of cerebral perfusion pressure alone. CONCLUSION In patients with severe acute brain trauma and intracranial hypertension associated with compromised cerebrospinal fluid spaces, monitoring and managing cerebral extraction of oxygen in conjunction with cerebral perfusion pressure result in better outcome than when cerebral perfusion pressure is managed alone.

Combined continuous monitoring of systemic and cerebral oxygenation in acute brain injury: Preliminary observations

ObjectiveTo continuously evaluate the relationship between global systemic and cerebral oxygenation during temporary profound hypocapnia, which was attempted for prompt management of posttraumatic intracranial hypertension. DesignProspective, intervention study. SettingNeuroscience intensive care unit of a university hospital. PatientsYoung adults (n = 21) with acute brain trauma, undergoing routine monitoring of jugular bulb and pulmonary artery oxyhemoglobin saturations, along with other monitoring. Measurements and Main ResultsIn 102multivariate observations carried out on days 2 and 3 posttrauma, two new physiologic variables were assessed. These variables, systemic-cerebral oxygenation index and the systemic-cerebral ventilatory index, were evaluated in terms of baseline and posthyperventilation changes. Overall, when intracranial pressure was largely increased, this increase was associated with decreased cerebral oxygen extraction (“luxury perfusion”), and high values of systemic-cerebral oxygenation index. In response to transient profound hypocapnia, the cerebral oxygen extraction normalized (increased), as did the systemic-cerebral oxygenation index (decreased), under most circumstances. The systemic-cerebral ventilatory index showed adequate systemic-cerebral response to hypocapnia in 92 (90.2%) observations. In the remaining ten (9.8%) observations, this response was considered inadequate, but it did not result in abnormal systemic or cerebral oxygenation parameters. ConclusionsIn young adults with severe acute brain trauma who require prompt management of intracranial hypertension, transient profound hypocapnia is effective in lowering the intracranial pressure, as well as in offsetting the cerebral luxury perfusion, while improving or maintaining adequate systemic oxygenation. The systemic-cerebral oxygenation index and the systemic-cerebral ventilatory index are potentially useful, physiologically monitorable variables for the combined assessment of global systemic and cerebral oxygenation in a variety of areas involving physiologic and/or therapeutic approaches. (Crit Care Med 1993; 21:1225–1232)

Cerebral blood flow, vascular resistance, and oxygen metabolism in acute brain trauma: Redefining the role of cerebral perfusion pressure?

OBJECTIVES To evaluate normal or high cerebral perfusion pressure in relation to cerebral blood flow and oxygen metabolism, as well as other multivariate cerebral hemodynamic and metabolic interrelationships, in acute brain trauma in humans. DESIGN Prospective, observational study. SETTING Neuroscience intensive care unit of a university hospital. PATIENTS Adults (n = 66) with severe acute brain trauma (Glasgow Coma Scale scores from 4 to 8), undergoing multivariate physiologic studies involving cerebral perfusion pressure, cerebral blood flow, cerebral metabolic rate of oxygen consumption, total hemoglobin content, arterio-jugular oxygen content difference, and cerebral vascular resistance, along with other routine procedures. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Statistical analysis did not demonstrate any correlation between cerebral perfusion pressure and cerebral blood flow, between cerebral perfusion pressure and arterio-jugular oxygen content difference, and between cerebral perfusion pressure and cerebral metabolic rate of oxygen consumption, over a broad spectrum of perfusion pressures ranging from 60 to 130 mm Hg. In contrast, a significant negative correlation was found between cerebral vascular resistance and cerebral blood flow, where higher values of cerebral vascular resistance were associated with lower blood flow levels, and vice versa. CONCLUSIONS In severe acute brain trauma, cerebral hemodynamic and oxygen metabolic variables are not necessarily correlated with normal or even high levels of cerebral perfusion pressure. Under these circumstances, cerebral vascular resistance (not perfusion pressure) is more closely correlated with different patterns of cerebral blood flow and metabolism.

Continuous monitoring of cerebral oxygenation in acute brain injury: assessment of cerebral hemodynamic reserve.

A new index of cerebral hemodynamics, cerebral hemodynamic reserve (CHR), was evaluated in 12 comatose adults with severe, acute, traumatic, diffuse swelling of the brain, who underwent continuous monitoring with a fiberoptic catheter of the saturation difference in arteriojugular oxyhemoglobin. CHR

Cerebral oxygenation monitoring

ObjectivesTo discuss theoretical and practical aspects of cerebral oxygenation, from isolated observational measurements to continuous interventional monitoring. Data SourcesRelevant articles from the pertinent literature, as well as a multivariate physiologic diagram developed in this article. Study SelectionTheoretical, experimental, and clinical information that further clarifies the physiologic relevance of cerebral oxygenation. Data ExtractionAll basic concepts of cerebral hemometabolism were used, up to cerebral hemodynamic reserve, and were interrelated accordingly. Data SynthesisCerebral perfusion pressure alone does not allow global cerebral hemometabolic optimization. The same situation is true for cerebral blood flow. The reason for this limitation is because these variables lack metabolic information. Cerebral arteriovenous differences do allow global cerebral hemometabolic optimization, because they reflect the exchange between the capillary and the tissue. In addition, cerebral hemodynamic reserve allows quantification of the cerebral microcirculatory tolerance to increases in intracranial “tightness” (decreases in intracranial compliance). ConclusionsMultivariate optimization of global cerebral oxygenation, primarily based on global cerebral oxygen delivery and extraction, may strongly affect outcome in a variety of predominantly diffuse, acute intracranial disorders. Cerebral hemodynamic reserve may be further explored in experimental and clinical areas, involving not just acute brain trauma. (Crit Care Med 1993; 21:1242–1246)

Cerebral blood flow and oxygen consumption in acute brain injury with acute anemia : an alternative for the cerebral metabolic rate of oxygen consumption ?

ObjectiveTo comparatively evaluate cerebral metabolic rate of oxygen consumption and a modification of it, cerebral consumption of oxygen, in patients with acute brain injury with acute anemia. DesignProspective, observational study. SettingNeuroscience intensive care unit (ICU) of a university hospital. PatientsAdults (n = 62) with acute brain trauma, undergoing serial 133xenon studies of regional cerebral blood flow and global cerebral oxygen metabolism, along with other routine monitoring techniques. Measurements and Main ResultsIn 173 combined studies of blood flow and oxygen metabolism, in the presence of spontaneous decreases in hemoglobin, cerebral metabolic rate of oxygen consumption and cerebral consumption of oxygen were comparatively evaluated in three groups with different hemoglobin levels. Cerebral metabolic rate of oxygen consumption was calculated as the product of averaged regional cerebral blood flow and arterio-jugular oxygen content difference, while cerebral consumption of oxygen was calculated as the product of averaged regional cerebral blood flow and the arterio-jugular oxyhemoglobin saturation difference, i.e., cerebral extraction of oxygen. Results indicated that a decrease of hemoglobin content is paralleled by a decrease in cerebral metabolic rate of oxygen consumption, even though the level of consciousness (coma score) is essentially unchanged across three hemoglobin groups. On the other hand, cerebral consumption of oxygen does not follow the decrease in hemoglobin and cerebral metabolic rate of oxygen consumption, thus demonstrating better stability to changing hemoglobin content. The low cerebral metabolic rate of oxygen consumption is due to a decrease in arterio-jugular oxygen content difference in anemia, while the cerebral extraction of oxygen does not follow the trend of the arterio-jugular oxygen content difference. ConclusionsIn acute brain trauma with acute anemia, calculated arterio-jugular oxygen content difference and cerebral metabolic rate of oxygen consumption tend to be progressively lower, depending on the extent of anemia, which is in disagreement with coma scores. These changes in hemoglobin tend to have an inverse influence on cerebral consumption of oxygen, which, therefore, constitutes an alternative and independent measure of cerebral oxygen consumption under these limiting circumstances. (Crit Care Med 1993; 21:1218–1224)

Cerebral lactate-oxygen index in acute brain injury with acute anemia: Assessment of false versus true ischemia

ObjectiveTo evaluate the occurrence of global cerebral ischemia in acute brain trauma with acute anemia by combined measurements of cerebral hemodynamics, oxygenation, and lactate production. DesignProspective, intervention study. SettingNeuroscience intensive care unit of a university hospital. PatientsAdults (n = 22) with severe acute brain trauma (Glasgow Coma Scores ranging from 4 to 8), undergoing frequent serial measurements of total hemoglobin content, jugular oxyhemoglobin saturation, arteriojugular oxygen content difference, arteriojugular lactate concentration difference, lactate-oxygen index, and cerebral blood flow, along with other routine procedures. Measurements and Main ResultsAcute anemia (disclosed by a total hemoglobin content of <11 g/dL in at least three measurements) was found in 19 (86%) of 22 patients. In 211 serial multivariate physiologic observations, only one (0.4%) disclosed abnormally negative arteriojugular lactate difference consistent with global cerebral ischemia. However, in 18 (8.5%) studies in seven (31.8%) patients, acute anemia resulted in markedly decreased values of arteriojugular oxygen content difference. The latter, in turn, yielded abnormally high values of lactate-oxygen index despite normal cerebral lactate production (arteriojugular lactate difference) and oxygenation (jugular oxyhemoglobin saturation). ConclusionsIn acute brain injury with acute anemia, global cerebral ischemia is a rare finding. However, false cerebral ischemia may be frequently found, if assessed by the lactate-oxygen index, because the denominator of the index (the arteriojugular oxygen content difference) frequently decreases as a function of decreasing hemoglobin, thus yielding false calculated ischemic high values for lactate-oxygen index despite normal cerebral oxygenation and lactate production. (Crit Care Med 1994; 22:1465–1470)

Relationship between early patterns of cerebral extraction of oxygen and outcome from severe acute traumatic brain swelling : Cerebral ischemia or cerebral viability ?

OBJECTIVE To evaluate outcome from severe acute traumatic diffuse brain swelling, in relation to early patterns of global cerebral extraction of oxygen. DESIGN Prospective, interventional study. SETTING Neuroscience intensive care unit of a university hospital. PATIENTS Adults (n = 205) with acute, essentially isolated brain trauma (predominantly diffuse brain swelling), undergoing routine early monitoring of cerebral extraction of oxygen and intracranial pressure, along with other monitoring modalities. INTERVENTIONS Routine neuroemergency procedures. MEASUREMENTS AND MAIN RESULTS Cerebral extraction of oxygen (arteriojugular oxyhemoglobin saturation difference) was measured in each patient, early in the acute phase (2 to 8 hrs postinjury). Outcome at 6 months postinjury was significantly better in patients with initially increased cerebral extraction of oxygen (>42%) than in those patients with normal (24% to 42%) or decreased (<24%) values. In contrast, no significant differences were found among these three groups with respect to age, initial Glasgow Coma Scale score, intracranial pressure, cerebral perfusion pressure, PaCO2, total hemoglobin content, and time from injury when the initial measurements were performed. CONCLUSIONS Initially increased cerebral extraction of oxygen appears to indicate global cerebral viability rather than cerebral ischemia in patients with acute traumatic diffuse brain swelling.

Lack of relevance of the Bohr effect in optimally ventilated patients with acute brain trauma.

The relationship between jugular bulb oxyhemoglobin saturation (SjO2) and oxygen tension (PjO2) during hyperventilation was prospectively evaluated in 37 adults with acute brain injuries. Hyperventilation was optimized in all patients, based on measured values of the arteriojugular oxyhemoglobin saturation difference, or cerebral extraction of oxygen (CEO2). Most patients initially had variable CEO2 values, in 578 observations carried out in the acute phase. Overall, there was a strong positive correlation between SjO2 and PjO2 at all levels of arterial pH. In 31 (5.3%) of the 578 observations, where the arterial pH was greater than 7.6, the SjO2 was disproportionally higher than the PjO2, despite a good SjO2-PjO2 correlation (moderate Bohr effect). In only 5 of these 31 observations (0.8%) did the SjO2 and PjO2 largely change in opposite directions (marked Bohr effect) during profound hypocapnia. The present findings support the current practice of continuous or intermittent SjO2 monitoring and management, and of optimized hyperventilation for control of intracranial hypertension, provided that hyperventilation is optimized according to the CEO2 values. Only on rare occasions (arterial pH greater than 7.6) is it advisable to replace SjO2 measurements by those of PjO2, because the latter is not affected by the Bohr effect.

Chapter 5 – Modulating Cerebral Oxygen Delivery and Extraction in Acute Traumatic Coma

Publisher Summary This chapter discusses monitoring techniques in an attempt to modulate cerebral oxygen delivery and extraction in acute traumatic coma. In some instances, cerebral hypervolemia also appears to be a significant treatable cause of increased intracranial pressure (ICP) in head-injured patients. Hyperventilation is a potent method of lowering ICP in the acutely head-injured patient. The data indicate that prompt reversibility of acute hypoxemia in the early phase, when pulmonary complications are generally absent or minor, is accomplished in a nearly automatic manner by standard inspired-oxygen concentration modulations, presumably avoiding prolonged hypoxemic episodes. In contrast, within a few days post injury, severe pulmonary complications are found to be more frequent, occasionally associated with systemic hemodynamic instability and frequently precluded a simple resolution of the hypoxic and ischemic insults.