Microcirculatory alterations induced by sedation in intensive care patients. Effects of midazolam alone and in association with sufentanil

Permissive Hypotension Has No Deleterious Impact on Fluid Balance or Kidney Function

OBJECTIVES

Mean arterial hypotension between 55 and 65 mm Hg could be tolerated safely in the absence of tissue hypoperfusion, but the consequences on fluid balance and kidney function remain unknown.

DESIGN

During a 1-year period, we retrospectively collected data of consecutive septic patients admitted for sepsis with a mean arterial pressure (MAP) less than 65 mm Hg despite fluid resuscitation.

SETTING

Medical 18-bed ICU in a tertiary teaching hospital.

PATIENTS

Septic patients with a MAP less than 65 mm Hg despite initial resuscitation.

INTERVENTIONS

In our ICU, MAP between 55 and 65 mm Hg was tolerated in the absence of peripheral hypoperfusion (permissive hypotension) or corrected using norepinephrine (septic shock group) when peripheral tissue hypoperfusion was present.

MEASUREMENTS AND MAIN RESULTS

Ninety-four consecutive septic patients were included, 15 in the permissive hypotension group and 79 in the septic shock group. Median age was 66 years (57-77 yr) and 42% were women. The main sources of infection were respiratory (45%) and abdominal (18%). Severity was more important in septic shock group with higher Sequential Organ Failure Assessment score (7 [5-10] vs. 4 [1-6]; p < 0.0001), more frequent organ support therapy and ultimately higher mortality (38 vs. 0%; p < 0.01). The total volume of crystalloids infused before ICU admission was not different between groups (1930 ± 250 vs. 1850 ± 150 mL; p = 0.40). Within the 6 first hours of ICU stay, patients in the permissive hypotension group received less fluids (530 ± 170 vs. 1100 ± 110 mL; p = 0.03) and had higher urinary output (1.4 mL [0.88-2.34 mL] vs. 0.47 mL/kg/hr [0.08-1.25 mL/kg/hr]; p < 0.001). In addition, kidney injury evaluated using KDIGO score was lower in the permissive hypotension group at 48 hours (0 hr [0-1 hr] vs. 1 hr [0-2 hr]; p < 0.05).

CONCLUSIONS

In septic patients without clinical peripheral hypoperfusion, mean arterial hypotension between 55 and 65 mm Hg could be tolerated safely without vasopressor infusion and was not associated with excessive fluid administration or kidney damage.

Incidence of Medical Adhesive-Related Skin Injuries and Associated Factors After Pediatric Congenital Heart Surgery: A Prospective Cohort Study

PURPOSE

The aim of this study was to identify the incidence, characteristics, and factors associated with medical adhesive-related skin injuries (MARSI).

DESIGN

Prospective cohort study.

SUBJECTS AND SETTINGS

The sample comprised 136 children in the postoperative period after congenital heart surgery. The study setting was in a 31-bed pediatric surgical intensive care unit (ICU) of a university hospital in Sao Paulo, Brazil.

METHODS

Patients were followed from admission, with daily skin assessments, until the onset of MARSI or ICU discharge. Outcomes were compared by Fisher's exact test, Pearson's χ2 test, Mann-Whitney test, Brunner-Munzel test, and Welch 2-sample t test.

RESULTS

The incidence of MARSI was 60.3%, with 85 injuries in 82 patients. The highest occurrence was on postoperative day 2 (27 wounds; 31.8%). The most frequent medical adhesive associated with MARSI was transparent film dressing (n = 74; 86.6%). Factors associated with MARSI were age (P = .000), number of devices inserted (P = .000), Braden Q Scale score (P = .005), duration of surgery (P = .021), cardiopulmonary bypass duration (P = .000), duration of mechanical ventilation (P = .000), and length of ICU stay (P = .000). Children who developed MARSI received more blood components (P = .039), vasopressors (P = .000), and corticosteroids (P = 0.000); required longer sedation (P = .000); and had more edema (P = .001).

CONCLUSION

This high incidence indicates the need for greater awareness and prompt action in response to MARSI. Polyurethane transparent film without concurrent use of a skin barrier product should be avoided.

Comparison of Microcirculatory Perfusion in Obese and Non-Obese Patients Undergoing Cardiac Surgery with Cardiopulmonary Bypass

Obesity is a frequent comorbidity among patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Cardiac surgery with CPB impairs microcirculatory perfusion, which is associated with multiple organ failure. As microvascular function is frequently compromised in obese patients, we studied whether cardiac surgery with CPB has a more detrimental effect on microcirculatory perfusion in obese patients. Sublingual microcirculatory perfusion was measured with sidestream dark field (SDF) imaging in obese patients (body mass index ≥32 kg/m²; n = 14) without type II diabetes mellitus and in lean patients (BMI 20–25 kg/m²; n = 22) undergoing cardiac surgery with CPB. CPB reduced systolic blood pressure and mean arterial pressure more profoundly in lean compared with obese patients (SBP: 38% vs. 18%; MAP: 11% vs. 8%, p < 0.05), and both restored after weaning from CPB. No differences were present in intraoperative glucose, hematocrit, hemoglobin, lactate, and blood gas values between obese and lean patients. Microcirculatory perfusion did not differ between obese and lean patients the day before surgery. CPB decreased microcirculatory perfusion with 9% in both groups, but this was only significant in lean patients (p < 0.05). Three days following surgery, microcirculatory perfusion was restored in both groups. In conclusion, microcirculatory perfusion was equally disturbed during cardiac surgery with CPB in metabolically healthy obese patients compared to lean patients.

The glymphatic system and its role in cerebral homeostasis

The brain's high bioenergetic state is paralleled by high metabolic waste production. Authentic lymphatic vasculature is lacking in brain parenchyma. Cerebrospinal fluid (CSF) flow has long been thought to facilitate central nervous system detoxification in place of lymphatics, but the exact processes involved in toxic waste clearance from the brain remain incompletely understood. Over the past 8 yr, novel data in animals and humans have begun to shed new light on these processes in the form of the "glymphatic system," a brain-wide perivascular transit passageway dedicated to CSF transport and interstitial fluid exchange that facilitates metabolic waste drainage from the brain. Here we will discuss glymphatic system anatomy and methods to visualize and quantify glymphatic system (GS) transport in the brain and also discuss physiological drivers of its function in normal brain and in neurodegeneration.

Protocol for a multicentre, prospective cohort study of practice patterns and clinical outcomes associated with emergency department sedation for mechanically ventilated patients: the ED-SED Study

INTRODUCTION

In mechanically ventilated patients, sedation strategies are a major determinant of outcome. The emergency department (ED) is the earliest exposure to mechanical ventilation for hundreds of thousands of patients annually in the USA. The one retrospective study that exists regarding ED sedation for mechanically ventilated patients showed a strong association between deep sedation in the ED and worse clinical outcomes. This finding suggests that the ED may be an optimal location to study the impact of early sedation on outcome, yet a lack of prospective studies represents a knowledge gap in this arena. This protocol describes a prospective observational study aimed at further characterising ED sedation practices and assessing the relationship between ED sedation and clinical outcomes. An association between ED sedation and clinical outcomes across multiple sites would suggest the need for changes in the current sedation strategies used in the ED, and provide evidence for future interventional studies in this field.

METHODS AND ANALYSIS

This is a multicentre, prospective cohort study testing the hypothesis that deep sedation in the ED is associated with worse clinical outcomes. A cohort of over 300 mechanically ventilated ED patients will be included. The primary outcome is ventilator-free days, and secondary outcomes include hospital mortality, incidence of acute brain dysfunction and lengths of stay. Multivariable linear regression will test the hypothesis that deep sedation in the ED is associated with a decrease in ventilator-free days.

ETHICS AND DISSEMINATION

Approval of the study by the Institutional Review Board (IRB) at each participating site has been obtained prior to data collection on the first patient. This work will be disseminated by publication of peer-reviewed manuscripts, presentation in abstract form at scientific meetings and data sharing with other investigators through academically established means.

In Vivo Imaging of Microvasculature during Anesthesia with High-Resolution Photoacoustic Microscopy

Anesthesia monitoring is extremely important in improving the quality of anesthesia and ensuring the safety of patients in operation. Photoacoustic microscopy (PAM) is proposed to in vivo image the skin microvasculature of 10 nude mice undergoing general anesthesia by using the isoflurane gas with a concentration of 3%. Benefiting from strong optical absorption of hemoglobin, PAM has good contrast and high resolution in mapping of microvasculature. A series of high quality images can clearly reveal the subtle changes of capillaries in morphology over time. Two indices, vessel intensity and vessel density, are extracted from these images to measure the microvasculature quantitatively. The imaging results show that the vessel intensity and density are increased over time. After 65 min, the vessel intensity increased 42.7 ± 8.6% and the density increased 28.6 ± 12.2%. These indices extracted from photoacoustic images accurately reflect the greater blood perfusion undergoing general anesthesia. Additionally, abnormal reductions of vessel intensity and density are also observed as overtime anesthesia. This preclinical study suggests that PAM holds potential to monitor anesthesia by imaging the skin microvasculature.

Vascular and Microvascular Endothelial Function in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Assessment of vascular endothelial function lacks consistency, and microvascular endothelial function has been only partly assessed in heart failure with preserved ejection fraction (HFpEF).

METHODS

The study population consisted of 90 patients: 45 had well documented HFpEF, and 45 had hypertension and no history or evidence of heart failure. Patients with hypertension but no heart failure were matched with HFpEF patients for age, sex, and diabetes. They served as control subjects. All patients underwent 2-dimensional Doppler echocardiography and vascular function measurements, including assessment of arterial wave reflections and arterial stiffness, brachial artery flow-mediated dilation (FMD), and forearm cutaneous blood flow with the use of a laser Doppler flow probe at rest and after release of arterial occlusion for 5 minutes.

RESULTS

Brachial artery FMD was lower in HFpEF than in control subjects (median (IQR) 3.6 (0.4-7.4) vs. 7.2 (3.2-17.2)%, P = .001). Forearm cutaneous blood flow at rest was similar in HFpEF and control subjects (P = .68). After release of arterial occlusion, forearm cutaneous peak blood flow was lower in HFpEF than in control subjects (P = .03). Estimated aortic systolic and mean blood pressures were similar in HFpEF and control subjects, whereas pulse pressure and pressure augmentation were greater in HFPEF than in control subjects (both P < .05).

CONCLUSION

Compared with hypertensive control subjects, patients with HFpEF had a depressed endothelial function in the forearm vasculature and microvasculature.

Effect of administration of water enriched in O2 by injection or electrolysis on transcutaneous oxygen pressure in anesthetized pigs

Background

Oral administration of oxygenated water has been shown to improve blood oxygenation and could be an alternate way for oxygen (O₂) supply. In this experiment, tissue oxygenation was compared in anesthetized pigs receiving a placebo or water enriched in O₂ by injection or a new electrolytic process.

Methods

Forty-two pigs randomized in three groups received either mineral water as placebo or water enriched in O₂ by injection or the electrolytic process (10 mL/kg in the stomach). Hemodynamic parameters, partial pressure of oxygen in the arterial blood (PaO₂), skin blood flow, and tissue oxygenation (transcutaneous oxygen pressure, or TcPO₂) were monitored during 90 minutes of general anesthesia. Absorption and tissue distribution of the three waters administered were assessed using dilution of deuterium oxide.

Results

Mean arterial pressure, heart rate, PaO₂, arteriovenous oxygen difference, and water absorption from the gut were not significantly different among the three groups. The deuterium to protium ratio was also similar in the plasma, skin, and muscle at the end of the protocol. Skin blood flow decreased in the three groups. TcPO₂ slowly decreased over the last 60 minutes of the experiment in the three groups, but when compared to the control group, the values remained significantly higher in animals that received the water enriched in O₂ by electrolysis.

Conclusions

In this protocol, water enriched in O₂ by electrolysis lessened the decline of peripheral tissue oxygenation. This observation is compatible with the claim that the electrolytic process generates water clathrates which trap O₂ and facilitate O₂ diffusion along pressure gradients. Potential applications of O₂-enriched water include an alternate method of oxygen supply.

Effects of some anesthetic agents on skin microcirculation evaluated by laser Doppler perfusion imaging in mice

Background

Anesthetic agents alter microcirculation, influencing tissue oxygenation and delivery of vital substrates. Laser Doppler perfusion imaging is a widespread technique in the field of microvascular research that can evaluate noninvasively and in real time the effects of environmental conditions, physical manipulations, diseases and treatments on peripheral perfusion. This study aims to evaluate laser Doppler perfusion imaging as a means to detect changes in skin microcirculation induced by some popular anesthetic agents in a murine model. Twenty-four age- and gender-matched healthy CD1 mice were examined by laser Doppler perfusion imaging. The skin microcirculatory response was measured at the level of plantar surfaces during isoflurane anesthesia with or without subsequent dexmedetomidine or acepromazine. At the end of the procedure, dexmedetomidine was reversed by atipamezole administration.

Results

In all mice, skin blood flow under isoflurane anesthesia did not show significant differences over time (P = 0.1). The serial perfusion pattern and values following acepromazine or dexmedetomidine administration differed significantly (P < 0.05).

Conclusions

We standardized a reliable laser Doppler perfusion imaging protocol to non-invasively assess changes in skin microcirculation induced by anesthesia in mice, considering the advantages and drawbacks of this technique and its translational value.

Pharmacokinetics Alterations of Midazolam Infusion versus Bolus Administration in Mechanically Ventilated Critically Ill Patients

There is no randomized study carried out in order to compare their pharmacokinetic parameters although midazolam, as a sedative, has been widely administered via continuous infusion as well as intermittent bolus doses in mechanically ventilated critically ill patients. We prospectively investigated the effect of these two principal methods on pharmacokinetic parameters in 23 of mentioned patients (16 males, 7 females) with the mean (± SD) age of 41.22 ± 17.5. All patients received total dose of 72 mg throughout the test days, 9 of whom received 1 mg/h (continuous infusion) and the rest obtained 4 mg / 4 h (intermittent bolus doses). Blood samples were collected at 8 and 4 h prior to the end time of drug administration (zero time), zero time and 4, 8, 12, 20 and 30 h after it. APACHE (Acute Physiology and Chronic Health Evaluation) II required data was recorded daily and the patients' mean score was 16.26 ± 4.38. The mean (± SD) value of pharmacokinetic parameters of Midazolam in continuous infusion and intermittent bolus doses methods were as follows: (t½ = 17.88 ± 14.65 h, Cl = 21.80 ± 14.95 L/h) vs. (t½ = 19.74 ± 12.45 h, Cl = 29.43 ± 19.45 L/h). Volume of distribution (Vd) was measured in continuous infusion group which was 612.58 ± 582.93 L. The calculated clearance and half-life were found not to be significantly different (p < 0.05). The patients might be exposed to similar undesired effects due to the large volumes of distribution following the administration methods studied.

Distinct alterations in sublingual microcirculatory blood flow and hemoglobin oxygenation in on-pump and off-pump coronary artery bypass graft surgery

OBJECTIVE

The authors hypothesized that cardiopulmonary bypass (CPB) (on-pump) is associated with more severe changes in the microcirculatory blood flow and tissue oxygenation as compared with off-pump coronary artery bypass surgery.

DESIGN

An observational study.

SETTING

A university hospital and teaching hospital.

PARTICIPANTS

Patients undergoing on-pump (n = 24) or off-pump (n = 24) cardiac surgery.

INTERVENTIONS

Microcirculatory measurements were performed before CPB and 10 minutes after the switch to CPB or before and during cardiac luxation in off-pump patients.

MEASUREMENTS AND MAIN RESULTS

Sublingual microcirculatory perfusion was investigated using side-stream dark field imaging, and sublingual microcirculatory oxygenation was measured using reflectance spectrophotometry. Conversion to CPB resulted in an increase in cardiac output from 4.0 ± 0.2 to 4.8 ± 0.3 L/min (p < 0.01) and a 40% reduction in arterial hemoglobin concentration. Cardiopulmonary bypass was associated with an increase in venular blood velocity from 349 ± 201 μm/s to 563 ± 227 μm/s (p < 0.05), a reduction in functional capillary density of 43%, and an increase in hemoglobin oxygenation of the red blood cells in the remaining filled capillaries from 47.2% ± 6.1% to 59.7% ± 5.2% (p < 0.001). The decrease in cardiac output during cardiac luxation from 4.5 ± 1.7 to 1.8 ± 0.8 L/min (p < 0.01) without hemoglobin changes was associated with a complete halt of capillary blood flow and a reduction in maximum capillary blood velocity from 895 ± 209 to 396 ± 178 μm/s (p < 0.01). The functional capillary density remained unchanged, whereas the hemoglobin oxygenation declined from 64.2% ± 9.1% to 48.6% ± 8.7% (p < 0.01).

CONCLUSIONS

On-pump and off-pump cardiac surgery are associated with distinct alterations in sublingual microcirculatory perfusion and hemoglobin oxygenation. Although on-pump surgery results in a fall out of capillaries resulting in decreased oxygen extraction, off-pump surgery results in a cessation of flow during luxation resulting in decreased convection of oxygen transport.

Mice treated with a benzodiazepine had an improved survival rate following Pseudomonas aeruginosa infection

Psychological stress has a high incidence after burn injury, therefore, anxiolytic drugs are often prescribed. Unfortunately, to date, no burn study has investigated the effects of anxiolytic drugs on the ability to fight infection. This study was undertaken to determine if psychological stress, anxiety-modulating drugs, or both, alter survival following an infection. On day 0, 7-week-old male C57Bl/6 mice either received a 15% full-thickness flame burn or were sham treated (anesthesia and shaved), whereas controls received no treatment. Mice received midazolam (1 mg/kg intraperitoneally) or saline daily and were stressed by exposure to rat in a guinea pig cage or placed in an empty cage for 1 hour a day, beginning on postburn day 1. For the survival experiments, mice either received bacteria after 2 or 8 consecutive days of predator exposure and drug treatment, which continued daily for 7 days after inoculation. In a separate set of experiments, after eight daily injections of midazolam, mice were given lipopolysaccharide, bacteria, or saline and were killed 12 hours later. Mice that received midazolam had improved survival rates when compared with their saline-treated counterparts, and the protective effect was more significant the more days they received the drug. For most of the cytokines, the bacteria-induced increase was significantly attenuated by midazolam as was the amount of bacteria in the liver. The protective effect seems to be independent of the drug's anxiolytic activity as there were no significant differences in survival between the predator-stressed and the nonstressed mice. The mechanisms responsible for the protective effect remain to be elucidated.

Intensive Care Unit-acquired infection as a side effect of sedation

Introduction

Sedative and analgesic medications are routinely used in mechanically ventilated patients. The aim of this review is to discus epidemiologic data that suggest a relationship between infection and sedation, to review available data for the potential causes and pathophysiology of this relationship, and to identify potential preventive measures.

Methods

Data for this review were identified through searches of PubMed, and from bibliographies of relevant articles.

Results

Several epidemiologic studies suggested a link between sedation and ICU-acquired infection. Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Furthermore, experimental evidence coming from studies both in humans and animals suggest that sedatives and analgesics present immunomodulatory properties that might alter the immunologic response to exogenous stimuli. Clinical studies comparing different sedative agents do not provide evidence to recommend the use of a particular agent to reduce ICU-acquired infection rate. However, sedation strategies aiming to reduce the duration of mechanical ventilation, such as daily interruption of sedatives or nursing-implementing sedation protocol, should be promoted. In addition, the use of short acting opioids, propofol, and dexmedetomidine is associated with shorter duration of mechanical ventilation and ICU stay, and might be helpful in reducing ICU-acquired infection rates.

Conclusions

Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects, and immunomodulatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Future studies should compare the effect of different sedative agents, and the impact of progressive opioid discontinuation compared with abrupt discontinuation on ICU-acquired infection rates.

Microcirculatory assessment in daily clinical practice - not yet ready but not too far!

ABSTRACT Shock is characterized by an alteration in tissue perfusion that may lead to tissue hypoxia. Recent guidelines recommend aggressive and early resuscitation therapy, but mortality rate is still unacceptably high. Unfortunately, traditional clinical surrogates used to guide resuscitation therapy poorly correlate with microcirculatory blood flow, a key determinant of tissue perfusion. New techniques that directly assess microcirculatory perfusion at the bedside have emerged as a complement to traditional macrohemodynamic parameters. These techniques have been supported by several studies showing microcirculatory alterations in different clinical settings. In addition, these microcirculatory alterations are related with outcome and persist regardless of arterial pressure normalization, being a better predictor of organ dysfunction and mortality than global hemodynamic and laboratory parameters. These findings allowed the concept of “microcirculatory-goal directed therapy”, which is now in its preliminary phase, as the impact of many interventions still needs to be assessed. Finally, microcirculation assessment has also been explored in other medical fields such as perioperative, systemic arterial hypertension, heart failure, and hyperviscosity syndromes. In this review, we shortly present the characteristics of microcirculation and the main determinants of capillary blood flow, and we discuss advantages and limitations of some recently available techniques to evaluate microcirculation at the bedside, and how they could be useful for the general clinician in daily practice.

[Microcirculatory alterations in critically ill patients: pathophysiology, monitoring and treatments]

Microcirculation represents a complex system devoted to provide optimal tissue substrates and oxygen. Therefore, pathophysiological and technological knowledge developments tailored for capillary circulation analysis should generate major advances for critically ill patients' management. In the future, microcirculatory monitoring in several critical care situations will allow recognition of macro-microcirculatory decoupling, and, hopefully, it will promote the use of treatments aimed at preserving tissue oxygenation and substrate delivery.

Severe cutaneous adverse reactions: emergency approach to non-burn epidermolytic syndromes

INTRODUCTION

Although severe cutaneous adverse reactions (SCARs), such as Stevens-Johnson syndrome and toxic epidermal necrolysis, are rare, they are associated with considerable morbidity and mortality.

METHODS

The current knowledge regarding background, differential diagnoses, critical care and implications for inter-hospital emergency medical service (EMS) transport of these patients is discussed.

CONCLUSION

SCAR patients will substantially benefit from early interdisciplinary care and thorough consideration of complications during EMS transport and intensive care treatment.