Anaesthetic management of patients with severe sepsis

Sedation with propofol and isoflurane differs in terms of microcirculatory parameters: A randomized animal study using dorsal skinfold chamber mouse model

OBJECTIVE

This study aimed to explore the effects of sedative doses of propofol and isoflurane on microcirculation in septic mice compared to controls. Isoflurane, known for its potential as a sedation drug in bedside applications, lacks clarity regarding its impact on the microcirculation system. The hypothesis was that propofol would exert a more pronounced influence on the microvascular flow index, particularly amplified in septic conditions.

MATERIAL AND METHODS

Randomized study was conducted from December 2020 to October 2021 involved 60 BALB/c mice, with 52 mice analyzed. Dorsal skinfold chambers were implanted, followed by intraperitoneal injections of either sterile 0.9 % saline or lipopolysaccharide for the control and sepsis groups, respectively. Both groups received propofol or isoflurane treatment for 120 min. Microcirculatory parameters were obtained via incident dark-field microscopy videos, along with the mean blood pressure and heart rate at three time points: before sedation (T0), 30 min after sedation (T30), and 120 min after sedation (T120). Endothelial glycocalyx thickness and syndecan-1 concentration were also analyzed.

RESULTS

In healthy controls, both anesthetics reduced blood pressure. However, propofol maintained microvascular flow, differing significantly from isoflurane at T120 (propofol, 2.8 ± 0.3 vs. isoflurane, 1.6 ± 0.9; P < 0.001). In the sepsis group, a similar pattern occurred at T120 without statistical significance (propofol, 1.8 ± 1.1 vs. isoflurane, 1.2 ± 0.7; P = 0.023). Syndecan-1 levels did not differ between agents, but glycocalyx thickness index was significantly lower in the isoflurane-sepsis group than propofol (P = 0.001).

CONCLUSIONS

Propofol potentially offers protective action against microvascular flow deterioration compared to isoflurane, observed in control mice. Furthermore, a lower degree of sepsis-induced glycocalyx degradation was evident with propofol compared to isoflurane.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study serves as a rich source of information about the phenotypic diversity and trajectory of circulating immune cells during pediatric sepsis.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Breakthrough of single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets (96,156 cells) were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with examining the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study provides a thorough and comprehensive understanding of immune dysregulation in pediatric sepsis.

Surgical Emergencies in Patients with Significant Comorbid Diseases

Emergency surgery in patients with significant comorbidities benefits from a structured approach to preoperative evaluation, intra-operative intervention, and postoperative management. Providing goal concordant care is ideal using shared decision-making. When operation cannot achieve the patient's goal, non-operative therapy including Comfort Care is appropriate. When surgical therapy is offered, preoperative physiology-improving interventions are far fewer than in other phases. Reevaluation of clinical care progress helps define trajectory and inform goals of care. Palliative Care Medicine may be critical in supporting loved ones during a patient's critical illness. Outcome evaluation defines successful strategies and outline opportunities for improvement.

Peripheral Nerve Block Practice in Portugal: A National Survey

Regional anesthesia (RA) has several benefits and its use has increased with the advent of ultrasound-guided techniques. Opioid-sparing anesthesia and reduced use of general anesthesia are some of the mainstay advantages of RA. Although anesthetic practices differ deeply between countries, RA has assumed a crucial role in the daily practice of anesthesiologists, particularly during the COVID-19 pandemic period. This cross-sectional study provides an overview of peripheral nerve block (PNB) techniques performed in Portuguese hospitals. An online survey was reviewed by members of Clube de Anestesia Regional (CAR/ESRA Portugal) and then sent to a national mailing list of anesthesiologists. The survey focused on specific topics related to RA techniques such as the importance of training and experience, and the relevance of logistical limitations during the execution of RA. All data were collected anonymously and included in a Microsoft Excel (Microsoft Corp., Redmond, WA, USA) database, for further analysis. A total of 335 valid answers were obtained. All participants considered RA as a key competence in their daily practice. Half of those inquired performed PNB techniques once to twice per week. The main limitations identified for performing RA in Portuguese hospitals were the absence of block rooms and insufficiently trained personnel for the appropriate and safe execution of these techniques. This survey provides a comprehensive overview of RA in the Portuguese setting and could serve as a baseline for further studies.

Anesthetic management of patients with sepsis/septic shock

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, while septic shock is a subset of sepsis with persistent hypotension requiring vasopressors to maintain a mean arterial pressure (MAP) of ≥65 mmHg and having a serum lactate level of >2 mmol/L, despite adequate volume resuscitation. Sepsis and septic shock are medical emergencies and time-dependent diseases with a high mortality rate for which early identification, early antibiotic therapy, and early source control are paramount for patient outcomes. The patient may require surgical intervention or an invasive procedure aiming to control the source of infection, and the anesthesiologist has a pivotal role in all phases of patient management. During the preoperative assessment, patients should be aware of all possible organ dysfunctions, and the severity of the disease combined with the patient's physiological reserve should be carefully assessed. All possible efforts should be made to optimize conditions before surgery, especially from a hemodynamic point of view. Anesthetic agents may worsen the hemodynamics of shock patients, and the anesthesiologist must know the properties of each anesthetic agent. All possible efforts should be made to maintain organ perfusion supporting hemodynamics with fluids, vasoactive agents, and inotropes if required.

Perioperative approach to precapillary pulmonary hypertension in non-cardiac non-obstetric surgery

Pulmonary hypertension (PH) confers a significant challenge in perioperative care. It is associated with substantial morbidity and mortality. A considerable amount of information about management of patients with PH has emerged over the past decade. However, there is still a paucity of information to guide perioperative evaluation and management of these patients. Yet, a satisfactory outcome is feasible by focusing on elaborate disease-adapted anaesthetic management of this complex disease with a multidisciplinary approach. The cornerstone of the peri-anaesthetic management of patients with PH is preservation of right ventricular (RV) function with attention on maintaining RV preload, contractility and limiting increase in RV afterload at each stage of the patient's perioperative care. Pre-anaesthetic evaluation, choice of anaesthetic agents, proper fluid management, appropriate ventilation, correction of hypoxia, hypercarbia, acid-base balance and pain control are paramount in this regard. Essentially, the perioperative management of PH patients is intricate and multifaceted. Unfortunately, a comprehensive evidence-based guideline is lacking to navigate us through this complex process. We conducted a literature review on patients with PH with a focus on the perioperative evaluation and suggest management algorithms for these patients during non-cardiac, non-obstetric surgery.

Knowledge of and Compliance with Surviving Sepsis Campaign Guidelines among Anesthesiologists: A Nationwide Survey in China

We aimed to describe anesthesiologists' knowledge of and compliance with the Surviving Sepsis Campaign (SSC) guidelines in the perioperative management of patients with sepsis in China. We designed a questionnaire-based, cross-sectional survey. We sent out online questionnaires during 2019 to evaluate whether anesthesiologists in China were familiar with and applied SSC guidelines in perioperative management. We also compared anesthesiologists' knowledge of and compliance with the guidelines among different levels of hospital. In this study, we obtained 971 responses from anesthesiology departments across China. The survey responses showed that 39.0% of anesthesiologists rated their knowledge of the SSC guidelines as being "very familiar" or at least "somewhat familiar." In total, 68.9% of respondents chose "Initial fluid resuscitation followed by frequent hemodynamic reassessment" as their therapy strategy for patients with septic shock; 62.0% of anesthesiologists chose lactate as a marker of initial resuscitation in clinical practice, and 39.1% thought bundle therapy needed to be started within 1 hour of sepsis diagnosis. A total of 37.1% and 27.1% of respondents chose hydroxyethyl starches and gelatins, respectively, as the preferred fluids for septic shock. As the first choice of vasopressors in patients with sepsis, 727 (74.9%) anesthesiologists chose the correct answer (norepinephrine). Anesthesiologists from tertiary hospitals (class A) had greater familiarity and compliance with the SSC guidelines than those from other hospitals (P < 0.001). In summary, anesthesiologists in China have some knowledge of the SSC guidelines and tend to practice in keeping with these guidelines. However, for some items, anesthesiologists are not up to date with the latest version of the SSC guidelines. The popularity of these guidelines is not homogenous among different levels of hospital. Anesthesiologists must strengthen their knowledge of the SSC guidelines and update their practice in a regular and timely manner, especially in other tertiary and primary hospitals.

The Pancreatitis Activity Scoring System Predicts Clinical Outcomes in Patients With Infected Pancreatic Necrosis

OBJECTIVES

The Pancreatitis Activity Scoring System (PASS) is an objective tool validated in acute pancreatitis but not in infected pancreatic necrosis (IPN). Our aim was to evaluate the role of PASS in IPN.

METHODS

We performed a retrospective cohort study of IPN patients admitted to the University of California, San Francisco from January 2011 to March 2019. Daily PASS scores were calculated for each patient. Receiver operator characteristic analysis was used to define the optimal cutoff PASS score to predict outcomes. The primary and secondary outcomes were 72 hours postintervention multiorgan failure (MOF) and early readmission (within 30 days), respectively.

RESULTS

One hundred and four patients underwent intervention (median age, 55 years). Thirty-five patients (33.6%) developed MOF postintervention. A 72-hour postintervention PASS greater than 250 was strongly associated with postintervention MOF (area under curve, 0.87; adjusted odds ratio, 26.83; 95% confidence interval, 6.37-112.86; P < 0.001). Discharge PASS greater than 150 was associated with 30-day readmission (area under curve, 0.82; adjusted odds ratio, 26.44; 95% confidence interval, 8.48-82.43; P < 0.001).

CONCLUSIONS

The PASS score was associated with postintervention clinical outcomes and early readmission, suggesting it is a valid measure of disease activity in patients with IPN. Further prospective validation of PASS in IPN is needed.

Pattern recognition receptors as therapeutic targets for bacterial, viral and fungal sepsis

Sepsis remains to be a significant health care problem associated with high morbidities and mortalities. Recognizing its heterogeneity, it is critical to understand our host immunological responses to develop appropriate therapeutic approaches according to the type of sepsis. Because pattern recognition receptors are largely responsible for the recognition of microbes, we reviewed their role in immunological responses in the setting of bacterial, fungal and viral sepsis. We also considered their therapeutic potentials in sepsis.

Role of β2 Integrins in Neutrophils and Sepsis

Sepsis remains medically challenging, with high morbidity and mortality. A novel intervention is urgently needed in the absence of specific, targeted therapy. Neutrophils act as double-edged swords in sepsis; they can help to eradicate microbes, but they also contribute to tissue injury. β2 integrins are critical adhesion molecules that regulate a number of neutrophil functions. β2 integrins consist of four members, namely, αLβ2, αMβ2, αXβ2, and αDβ2. Here, we review the role of each β2 integrin in neutrophils and sepsis and consider future direction for therapeutic intervention.

Determinants of 30-day Morbidity in Adult Cranioplasty: An ACS-NSQIP Analysis of 697 Cases

Supplemental Digital Content is available in the text.

Cranioplasty is performed to restore the function and anatomy of the skull. Many techniques are used, including replacement of the bone flap and reconstruction with autologous or synthetic materials. This study describes the complication profile of adult cranioplasty using a prospective national sample and identifies risk factors for 30-day morbidity.

Ultrasound-guided popliteal sciatic and adductor canal block for below-knee surgeries in high-risk patients

Background and Aims:

Central neuraxial block and general anaesthesia in patients with significant comorbidities are associated with considerable peri-operative morbidity and mortality. This study aims to delineate peripheral nerve block as a suitable alternative technique in high-risk patients posted for below-knee surgery.

Methods:

Twenty patients with the American Society of Anesthesiologist's (ASA) physical status grade III and IV, aged 30–80 years, scheduled for below-knee surgery from May 2018 to February 2019 were enrolled in this prospective study. All patients received ultrasound-guided popliteal sciatic block with 20 ml 0.5% ropivacaine and adductor canal block with 10 ml 0.375% ropivacaine. The peripheral nerve block success rate, sensory and motor block onset time, haemodynamic parameters, duration of post-operative analgesia and patient's satisfaction were recorded. Descriptive statistics of the study were calculated and the data was analysed using an SPSS statistics 21.0 program.

Result:

Surgery was performed successfully with no additional analgesic requirement in all patients. The mean duration for sensory and motor block onset time was 3.35 ± 0.49 (mean ± standard deviation) and 4.65 ± 0.48 (mean ± standard deviation) minutes respectively. Haemodynamic parameters were maintained stable throughout the procedure. The average duration of postoperative analgesia was 7.5 ± 0.8 (mean ± standard deviation) hours. Patient overall satisfaction as assessed, by three-point Lickert's scale, was satisfactory.

Conclusion:

Ultrasound-guided combined popliteal sciatic and adductor canal block is an effective alternative anaesthetic technique for below-knee surgeries with stability of haemodynamic parameters and pain management in high-risk patients.

Special Considerations for the Septic Patient Going to the Operating Room

Perioperative care of the septic patient presents unique challenges for the nurse. Understanding the physiology of sepsis is important for the nurse to anticipate the physiologic changes associated with the disorder and to prioritize the patient's needs. Ensuring adequate intravenous access by peripheral or central venous access as well as anticipating potential invasive monitoring lines allows the nurse to quickly administer antibiotic therapy, initiate fluid resuscitation, and prepare for potential vasopressor use.

From the Cover: Prolonged Exposure to Volatile Anesthetic Isoflurane Worsens the Outcome of Polymicrobial Abdominal Sepsis

Sepsis continues to result in high morbidity and mortality. General anesthesia is often administered to septic patients, but the impacts of general anesthesia on host defense are not well understood. General anesthesia can be given by volatile and intravenous anesthetics. Our previous in vitro study showed that volatile anesthetic isoflurane directly inhibits leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1), critical adhesion molecules on leukocytes. Thus, the role of isoflurane exposure on in vivo LFA-1 and Mac-1 function was examined using polymicrobial abdominal sepsis model in mice. As a comparison, intravenous anesthetic propofol was given to a group of mice. Wild type, LFA-1, Mac-1, and adhesion molecule-1 knockout mice were used. Following the induction of polymicrobial abdominal sepsis by cecal ligation and puncture, groups of mice were exposed to isoflurane for either 2 or 6 h, or to propofol for 6 h, and their outcomes were examined. Bacterial loads in tissues and blood, neutrophil recruitment to the peritoneal cavity and phagocytosis were studied. Six hours of isoflurane exposure worsened the outcome of abdominal sepsis (P < .0001) with higher bacterial loads in tissues, but 2 h of isoflurane or 6 h of propofol exposure did not. Isoflurane impaired neutrophil recruitment to the abdominal cavity by inhibiting LFA-1 function. Isoflurane also impaired bacterial phagocytosis via complement receptors including Mac-1. In conclusion, prolonged isoflurane exposure worsened the outcome of experimental polymicrobial abdominal sepsis and was associated with impaired neutrophil recruitment and bacterial phagocytosis via reduced LFA-1 and Mac-1 function.

Coexisting Systemic Infections in Patients Who Present With a Fall

BACKGROUND

Although the causes of falls are legion, infectious disease-related factors are not commonly reported in the published literature. We investigated the characteristics of patients presenting to the hospital because of a fall and who were subsequently found to have a coexisting systemic infection (CSI).

MATERIALS AND METHODS

This was a retrospective study performed at Massachusetts General Hospital, using the electronic database of adult patients receiving care during the period January 1, 2000 through December 31, 2014. Cases were initially screened by using billing codes for "fall," "sepsis," "bacteremia" and "systemic inflammatory response syndrome" (SIRS). Evaluable patients had documented CSI in the setting of a fall.

RESULTS

Of 161 evaluable patients, 84 (52.2%) were female. The mean age was 75. 2 years (range: 35-102 years, median = 78 years). Fall was considered "mechanical" (e.g., tripped by a rug) in 106 (65.8%) cases, with 126 (78.3%) patients living at home. SIRS criteria were met on initial healthcare encounters of 66 (40.1%) patients. Urinary and lower respiratory tract infections were the most common infectious disease conditions (71 [44.1%] and 37 [23.0%] cases, respectively). Bacteremia was seen in 64 (39.8%) cases. Staphylococcus aureus was the most common cause of bacteremia (21 cases, 31.3% of bloodstream isolates). CSI was not initially suspected by providing clinicians in 64 (39.8%) patients.

CONCLUSIONS

Falls associated with CSIs are often considered "mechanical" in nature, and they frequently fail to meet the SIRS criteria on initial presentation. Aside from its commonly recognized causes, falls may be an atypical manifestation of a systemic infection.

Refinement of animal models of sepsis and septic shock

This report aims to facilitate the implementation of the Three Rs (replacement, reduction, and refinement) in the use of animal models or procedures involving sepsis and septic shock, an area where there is the potential of high levels of suffering for animals. The emphasis is on refinement because this has the greatest potential for immediate implementation. Specific welfare issues are identified and discussed, and practical measures are proposed to reduce animal use and suffering as well as reducing experimental variability and increasing translatability. The report is based on discussions and submissions from a nonregulatory expert working group consisting of veterinarians, animal technologists, and scientists with expert knowledge relevant to the field.

Sepsis pathophysiology and anesthetic consideration

Sepsis remains to be a significant health care issue associated with high mortality and healthcare cost, despite the extensive effort to better understand the pathophysiology of the sepsis. Recently updated clinical guideline for severe sepsis and septic shock, "Surviving Sepsis Campaign 2012", emphasizes the importance of early goal-directed therapy, which can be implemented in intraoperative management of sepsis patients. Herein, we review the updates of current guideline and discuss its application to anesthesic management. Furthermore, we review the recent advance in knowledge of sepsis pathophysiology, focusing on immune modulation, which may lead to new clinical therapeutic approach to sepsis.

Optimal perioperative management of arterial blood pressure

Perioperative blood pressure management is a key factor of patient care for anesthetists, as perioperative hemodynamic instability is associated with cardiovascular complications. Hypertension is an independent predictive factor of cardiac adverse events in noncardiac surgery. Intraoperative hypotension is one of the most encountered factors associated with death related to anesthesia. In the preoperative setting, the majority of antihypertensive medications should be continued until surgery. Only renin-angiotensin system antagonists may be stopped. Hypertension, especially in the case of mild to moderate hypertension, is not a cause for delaying surgery. During the intraoperative period, anesthesia leads to hypotension. Hypotension episodes should be promptly treated by intravenous vasopressors, and according to their etiology. In the postoperative setting, hypertension predominates. Continuation of antihypertensive medications and postoperative care may be insufficient. In these cases, intravenous antihypertensive treatments are used to control blood pressure elevation.

Anesthetic management for patients with perforation peritonitis

Perforation peritonitis is a common surgical emergency. Anesthesia in patients with perforation peritonitis can be challenging. Delayed presentations, old age, hemodynamic instability, presence of sepsis and organ dysfunction are some of the predictors of poor outcome in such patients. Pre-operative optimization can reduce intraoperative and post-operative morbidity and mortality, but surgery should not be unnecessarily delayed. Intensive care in critical care settings may be essential.

Polymorphic mononuclear neutrophils CD64 index for diagnosis of sepsis in postoperative surgical patients and critically ill patients

BACKGROUND

Surface neutrophil CD64 expression is upregulated in patients with bacterial infection. As it was suggested that the CD64 index could be used to detect sepsis in hospitalized patients, we questioned whether the CD64 index could discriminate between septic patients and postoperative surgical patients, defined as systemic inflammatory response syndrome (SIRS), both admitted at the intensive care unit (ICU). Furthermore, we wondered whether the CD64 index was an improved diagnostic compared to standard assays used at the laboratory. For this, outclinic (OC) patients were included as controls.

METHODS

The Leuko64™ assay was used to determine the CD64 index in residual EDTA blood samples from selected septic patients (n=25), SIRS patients (n=19), and OC patients (n=24). Additionally, WBC count, neutrophilic and eosinophilic granulocyte count, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were measured simultaneously.

RESULTS

The CD64 index was higher in septic patients compared to both the SIRS and OC group (p<0.0001). In addition, the WBC count, neutrophil count, ESR and CRP were also higher in septic patients than the OC group (p<0.0001). However, only the WBC count, eosinopenia, and ESR were comparable between the SIRS and the sepsis group and proved to be discriminative to the OC group (p<0.05). The CD64 index demonstrated higher sensitivity and specificity than CRP, WBC count, neutrophilic and eosinophilic granulocyte count, and ESR.

CONCLUSIONS

A high CD64 index was found in septic intensive care patients, while a low CD64 index was observed in OC and SIRS patients, demonstrating that the CD64 index can be used for routine diagnostics in the ICU setting.

Sepsis otopathy: experimental sepsis leads to significant hearing impairment due to apoptosis and glutamate excitotoxicity in murine cochlea

Hearing loss is frequent in intensive care patients and can be due to several causes. However, sepsis has not been examined as a possible cause. The aim of this study is to assess the influence of experimental sepsis on hearing thresholds and to evaluate pathological changes in the cochlea. The cecal ligation puncture technique was used to induce sepsis in 18 mice. Results were compared with those from 13 sham-operated and 13 untreated control mice. The hearing thresholds of the animals were evaluated with auditory evoked brainstem responses prior to the induction of sepsis and again at the peak of the disease. Immediately after the second measurement, the mice were sacrificed and the inner ears harvested and prepared for further evaluation. The cochleae were examined with light microscopy, electron microscopy and immunohistochemistry for Bax, cleaved caspase-3 and Bcl-2. The mice with sepsis showed a significant hearing loss but not the control groups. Induction of apoptosis could be shown in the supporting cells of the organ of Corti. Furthermore, excitotoxicity could be shown at the basal pole of the inner hair cells. In this murine model, sepsis leads to significant hearing impairment. The physiological alteration could be linked to apoptosis in the supporting cells of the organ of Corti and to a disturbance of the synapses of the inner hair cells.

Organisation and planning of anaesthesia for emergency surgery

Patients presenting for emergency surgery represent a category at high risk of complications, with substantial morbidity and mortality, whose management may be extremely challenging. In this first of two articles we consider the identification and evaluation of high risk emergency patients, the provision of critical care support, the management of sepsis, common postoperative complications and in-theatre death.

Physical plugging does not account for attenuation of capillary leakage by hydroxyethyl starch 130/0.4: a synthetic gel layer model

Hydroxyethyl starch (HES) solutions, widely used plasma substitutes, reportedly attenuate capillary leakage via physical plugging of capillary defects. We investigated how 2% HES solutions of different molecular weights (HES(70): 70 kDa, HES(130): 130 kDa, HES(200): 200 kDa, and HES(670): 670 kDa) affect dye release from polyacrylamide gels (PAGs) as a model of endothelial glycocalyx. We assessed dye release from 4% PAG with varying concentrations of albumin [0, 1, 2, 4, and 8% (w/v)] by measuring the change in dye absorbance (ΔAbs) at 5 h for each HES solution. For PAG containing no albumin, ΔAbs for HES(130) was 30% lower than that for HES(70) and HES(200), and 50% lower than that for HES(670). At concentrations of 1-8% albumin, ΔAbs at 5 h with HES(70), HES(130), and HES(200) solutions were almost half that with the HES(670) solution, but no significant differences were noted in ΔAbs at 5 h among HES(70), HES(130), and HES(200) solutions. The inhibition of dye release by HES(670) is likely due to the hindering effect of HES molecules partitioned into gel pores. However, a unique property of HES(130) , including the heavy hydroxyethylation at the C(2) position, may promote specific interactions with PAG and thereby inhibit solute release.