The effect of fluid bolus administration on cerebral tissue oxygenation in post-cardiac arrest patients

PURPOSE

Fluid boluses (FB) are often used in post-cardiac arrest (CA) patients with haemodynamic instability. Although FB may improve cardiac output (CO) and mean arterial pressure (MAP), FB may also increase central venous pressure (CVP), reduce arterial PaO₂, dilute haemoglobin and cause interstitial oedema. The aim of the present study was to investigate the net effect of FB administration on cerebral tissue oxygenation saturation (SctO₂) in post-CA patients.

METHODS

Pre-planned sub-study of the Neuroprotect post-CA trial (NCT02541591). Patients with anticipated fluid responsiveness based on stroke volume variation (SVV) or passive leg raising test were administered a FB of 500 ml plasma-lyte A (Baxter Healthcare) and underwent pre- and post-FB assessments of stroke volume, CO, MAP, CVP, haemoglobin, PaO₂ and SctO₂.

RESULTS

52 patients (mean age 64 ± 12 years, 75% male) received a total of 115 FB. Although administration of a FB resulted in a significant increase of stroke volume (63 ± 22 vs 67 ± 23 mL, p = 0.001), CO (4,2 ± 1,6 vs 4,4 ± 1,7 L/min, p = 0.001) and MAP (74,8 ± 13,2 vs 79,2 ± 12,9 mmHg, p = 0.004), it did not improve SctO₂ (68.54 ± 6.99 vs 68.70 ± 6.80%, p = 0.49). Fluid bolus administration also resulted in a significant increase of CVP (10,0 ± 4,5 vs 10,7 ± 4,9 mmHg, p = 0.02), but did not affect PaO₂ (99 ± 31 vs 94 ± 31 mmHg, p = 0.15) or haemoglobin concentrations (12,9 ± 2,1 vs 12,8 ± 2,2 g/dL, p = 0.10). In a multivariate model, FB-induced changes in CO (beta 0,77; p = 0.004) and in CVP (beta -0,23; p = 0.02) but not in MAP (beta 0,02; p = 0.18) predicted post-FB ΔSctO₂.

CONCLUSIONS

Despite improvements in CO and MAP, FB administration did not improve SctO₂ in post-cardiac arrest patients.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Low hemoglobin levels are associated with lower cerebral saturations and poor outcome after cardiac arrest

PURPOSE

Post-cardiac arrest (CA) patients have a large cerebral penumbra at risk for secondary ischemic damage in case of suboptimal brain oxygenation during ICU stay. The aims of this study were to investigate the association between hemoglobin, cerebral oxygenation (SctO2) and outcome in post-CA patients.

METHODS

Prospective observational study in 82 post-CA patients. Hemoglobin, a corresponding SctO2 measured by NIRS and SVO2 in patients with a pulmonary artery catheter (n=62) were determined hourly during hypothermia in the first 24h of ICU stay.

RESULTS

We found a strong linear relationship between hemoglobin and mean SctO2 (SctO2=0.70×hemoglobin+56 (R(2) 0.84, p=10(-6))). Hemoglobin levels below 10g/dl generally resulted in lower brain oxygenation. There was a significant association between good neurological outcome (43/82 patients in CPC 1-2 at 180 days post-CA) and admission hemoglobin above 13g/dl (OR 2.76, 95% CI 1.09:7.00, p=0.03) or mean hemoglobin above 12.3g/dl (OR 2.88, 95%CI 1.02:8.16, p=0.04). This association was entirely driven by results obtained in patients with a mean SVO2 below 70% (OR 6.25, 95%CI 1.33:29.43, p=0.01) and a mean SctO2 below 62.5% (OR 5.87, 95%CI 1.08:32.00, p=0.03).

CONCLUSION

Hemoglobin levels below 10g/dl generally resulted in lower cerebral oxygenation. Average hemoglobin levels below 12.3g/dl were associated with worse outcome in patients with suboptimal SVO2 or SctO2. The safety of a universal restrictive transfusion threshold of 7g/dl can be questioned in post-CA patients.

Les nouveaux agents volatils halogénés en neuro-anesthésie : quelle place pour le sévoflurane ou le desflurane ?

The effects on cerebral circulation and metabolism of sevoflurane and desflurane are largely comparable to isoflurane. Both induce a direct vasodilation of the cerebral vessels, resulting in a less pronounced decrease in cerebral blood flow compared to the decrease in cerebral metabolism. This direct vasodilation seems to be dose-dependent and more pronounced for desflurane > isoflurane > sevoflurane. Many reports suggest luxury perfusion at high concentrations of desflurane. Sevoflurane maintains intact cerebral autoregulation up to 1.5 MAC. Desflurane induces a significant impairment in autoregulation, with a completely abolished autoregulation at 1.5 MAC. Both sevoflurane and desflurane (up to 1.5 MAC) maintain normal CO(2) regulation. As to their effect on final intracranial pressure (ICP), both sevoflurane and desflurane revealed no increases in ICP. However, compared to intravenous hypnotics, subdural ICP is higher with volatiles because of their tendency to increase cerebral swelling after dura opening (isoflurane > sevoflurane). Several case reports have noted seizure-like movements, as well as EEG recorded seizures during induction of sevoflurane anesthesia. Especially, in children during inhalational induction with hyperventilation at a high sevoflurane concentration, severe epileptiform EEG with a hyperdynamic response were observed, which urges for caution using inhalational sevoflurane induction in children for neurosurgical procedures. Neuroprotective properties (reduced neuronal death either by necrosis or apoptosis) have been attributed to all volatile agents. However, these neuroprotective effects have been described in experimental or animal models, so their possible effect on humans remains to be proven.

Influence of intravenous clonidine pretreatment on anesthetic requirements during bispectral EEG-guided sevoflurane anesthesia

STUDY OBJECTIVE

To assess the anesthetic effects of clonidine during sevoflurane anesthesia guided by the bispectral index (BIS), which is a processed EEG variable correlated with anesthetic-hypnotic depth.

DESIGN

Placebo-controlled, double-blind clinical trial.

SETTINGS

Elective laparoscopic surgery.

PATIENTS

60 ASA physical status I patients scheduled for laparoscopic surgery.

INTERVENTIONS

Patients received either clonidine (3 micrograms/kg, 15 min before induction) or placebo premedication for a sevoflurane-induced and sevoflurane-maintained anesthesia. Sevoflurane was titrated against a BIS held between 40 and 50. Analgesia was provided by local infiltration with bupivacaine. Need for postoperative analgesia was recorded.

RESULTS AND CONCLUSION

Mean sevoflurane requirements were not lower with clonidine pretreatment. There was statistically better perioperative hemodynamic stability (i.e., fewer episodes of hypertension and tachycardia) without clinical relevance. A decreased need for postoperative analgesia was observed.

Use of continuous bispectral EEG monitoring to assess depth of sedation in ICU patients

Monitoring the depth of sedation in patients under intensive care is difficult. Clinical assessment by the different scoring systems produces insufficient information, especially once deeply sedated patients become unresponsive to any external stimulation. Recently, the bispectral index (BIS), the result of computerized bispectral electroencephalographic monitoring, was found to be the best predictor of depth of anaesthesia during surgical intervention. This report concerns BIS monitoring in 18 randomly selected, deeply sedated, surgical patients in the intensive care unit, who were unresponsive to standard clinical stimulation (Ramsay sedation score). A wide range of BIS was observed, with 15 of the patients having a BIS below 60, indicating a state of deep sedation (or possibly over-sedation). Therefore, further studies using BIS monitoring in patients under intensive care are needed to determine if this method can guide sedation and prevent oversedation in this context and, most importantly, to analyse its final cost-benefit ratio.

[Early enteral feeding in cranial trauma]

Until some years ago, patients suffering from head injury were poorly fed and nutrition was not a primary concern in the medical treatment of these patients. To date, six studies on head-injury patients have examined the effect of nutritional support on their outcome. All showed that lack of adequate nutrition contributed to increased mortality and morbidity. Head-injured patients on conventional enteral nutrition receive significantly less calories and proteins, resulting in an increased morbidity and mortality rate. Most of the severely head injured patients receiving enteral nutrition do not tolerate enteral feedings because of abnormal gastric emptying. The mechanisms of altered gastric function remain obscure. Increased intracranial pressure, cytokines, corticotropin-releasing factor, opiates, and other agents may all play a role. Impaired gastric motility has led to increasing use of small bowel feeding in head-injured patients. Jejunal feeding enables a higher caloric input and a better nitrogen balance. Moreover, it enables early enteral administration of nutrients in a safe and efficient way. Early administration of nutrients may be extremely important as it seems to decrease the hypermetabolic response to traumatic injury. Therefore, early jejunal enteral feeding may become an important cornerstone in the medical management of head-injured patients.

Comparison of spontaneous frontal EMG, EEG power spectrum and bispectral index to monitor propofol drug effect and emergence

BACKGROUND

The aim of this study was to investigate the accuracy of frontal spontaneous electromyography (SEMG) and EEG spectral edge frequency (SEF 95%), median frequency (MF), relative delta power (RDELTA) and bispectral index (BIS) in monitoring loss of and return of consciousness and hypnotic drug effect during propofol administration at different calculated plasma target concentrations.

METHODS

Propofol was administered by using a target-controlled infusion at different propofol steady-state concentrations. All variables were measured simultaneously at specific calculated concentrations and endpoints.

RESULTS

Loss of consciousness was accurately monitored by BIS, SEMG and SEF 95%, and propofol drug effect by BIS only. Return of consciousness was predicted by BIS, MF and SEF 95%. Due to the biphasic EEG pattern of propofol and the lack of reproducible data at specific propofol concentrations, the clinical usefulness of SEF 95%, MF and RDELTA was very limited. SEMG was useful to detect loss and return of consciousness, but without predictive value.

CONCLUSIONS

The BIS might be an accurate measure to monitor depth of anaesthesia and hypnotic drug effect. Other neurophysiologic measures have limited value to monitor depth of anaesthesia and hypnotic drug effect.

Subjective complaints versus neuropsychological test performance after moderate to severe head injury

Neuropsychological test performance and subjective complaints of 85 patients with moderate to severe head injury were investigated at 6 months postinjury. The neuropsychological test battery included 10 measures of attention, memory, mental flexibility, reaction time, visuoconstruction and verbal fluency. Subjective complaints were assessed using a self-report questionnaire subdivided into four subscales (somatic, cognitive, emotional and behavioural). Ratings were obtained for the pre-injury and current status. Thirty-three trauma patients with injuries to other parts of the body than the head were used as controls. For the head injured, relatives also completed the questionnaire. Head injured patients performed significantly below trauma control patients on nearly all test measures. Head injured patients and their relatives reported a significant increase in subjective complaints since the injury on all four subscales, with no differences between patients' and relatives' reports. These changes were also reported by the trauma controls, but they report fewer changes in somatic and cognitive functioning. Exploratory canonical correlation analyses revealed no correlations between any of the four scales of the questionnaire and the test measures, nor for the head injured, the trauma controls, or the relatives, indicating no relevant relationship between subjective complaints and neuropsychological test performance.

Jugular bulb oximetry: review on a cerebral monitoring technique

Jugular bulb oximetry is the first available continuous monitoring method estimating the adequacy of cerebral perfusion. Despite its major technical as well as methodological shortcomings the information on the oxygen supply to demand balance of the brain seems most valuable. Especially the deleterious consequences of systemic variations (mainly concerning arterial blood pressure and CO2-tension) on the diseased brain are revealed by jugular bulb saturation values. The prevention and/or the early detection of these systemic secondary insults could have important implications as to final neurological outcome. Jugular bulb oximetry could also guide specific intracranial antihypertensive treatment, as it may reveal the pathophysiological mechanisms behind intracranial hypertension with regard to the status of cerebral perfusion (cerebral hyperemia or cerebral hypoperfusion). These insights might increase the efficacy of all treatments available for intracranial hypertension.

Cerebral perfusion pressure and intracranial pressure in relation to neuropsychological outcome

OBJECTIVE

The study attempted to examine the relationship between neuropsychological functioning and reduced cerebral perfusion pressure (CPP), raised intracranial pressure (ICP), and reduced mean arterial pressure (MAP), monitored during intensive care treatment.

DESIGN

This prospective follow-up study included consecutive patients and evaluated outcome at 6 months postinjury by the administration of a neuropsychological test battery.

SETTING

The study was conducted at the University Hospital of Gent, Belgium.

PATIENTS AND PARTICIPANTS

Over a 30-month period, 43 patients were included. Inclusion criteria were the following: hospital admission following closed head injury. ICP monitoring, no medical history of central nervous system disease or mental retardation, survival for at least 6 months, and informed consent for participation.

INTERVENTIONS

All patients received the hospital's standard treatment for head injury, which remained unchanged during the study period.

MEASUREMENTS AND RESULTS

Reduced CPP was analyzed using the number of observed values below 70 mmhg, raised ICP using the number of values above 20 mmHg, and MAP using the number of values below 80 mmHg. The neuropsychological test battery included 11 measures of attention, information processing, motor reaction time, memory, learning, visuoconstruction, verbal fluency, and mental flexibility. No linear relationships were found between overall neuropsychological impairment and episodes of reduced CPP, raised ICP, or reduced MAP.

CONCLUSIONS

Although reduced CPP and raised ICP are frequent, often fatal, complications of head injury, in survivors they do not seem to be related to later neuropsychological functioning.

Analysis of very early jugular bulb oximetry data after severe head injury: implications for the emergency management?

Jugular bulb oximetry provides the first bedside available information on cerebral oxygen utilization. An extensive analysis was made of all initial jugular bulb oximetry data obtained in 150 patients within the first 12 h after severe traumatic brain injury. These data revealed initial abnormal jugular bulb saturation values in 57 patients (= 38% of study population), with a predominance of jugular bulb desaturation (observed in 45 patients). This confirms earlier reports that revealed a high incidence of disturbed and inadequate cerebral perfusion in the first hours after brain injury. Jugular bulb desaturation was especially related to systemic causes (such as a lowered cerebral perfusion pressure observed in 29 patients, and a lowered arterial carbon dioxide tension in 24 patients). These findings could have important implications for the emergency management of severely head-injured patients, as outcome might possibly be improved by better attention to all systemic factors that might reduce cerebral perfusion in the early hours after traumatic insult.