Acute pancreatitis during sickle cell vaso-occlusive painful crisis

Sickle cell disease is characterized by chronic hemolytic anemia and vaso-occlusive painful crisis. The vascular occlusion in sickle cell disease is a complex process and accounts for the majority of the clinical manifestations of the disease. Abdominal pain is an important component of vaso-occlusive painful crisis and may mimic diseases such as acute appendicitis and cholecystitis. Acute pancreatitis is rarely included as a cause of abdominal pain in patients with sickle cell disease. When it occurs it may result form biliary obstruction, but in other instances it might be a consequence of microvessel occlusion causing ischemia. In this series we describe four cases of acute pancreatitis in patients with sickle cell disease apparently due to microvascular occlusion and ischemic injury to the pancreas. All patients responded to conservative management. Acute pancreatitis should be considered in the differential diagnosis of abdominal pain in patients with sickle cell disease.     

Urinary markers of bone resorption, pyridinoline and deoxypyridinoline, are increased in sickle cell patients with further increments during painful crisis

The painful crisis is the hallmark of sickle-cell disease (SCD). Bone resorption, as part of physiological bone turnover, results in release into the circulation with subsequent urinary excretion of the collagen cross-links pyridinoline (PYD) and deoxypyridinoline (DPD). Urinary PYD and DPD concentrations could reflect the extent of bone infarction during painful sickle-cell crisis. Urinary concentrations of PYD and DPD, adjusted for urine creatinine, were measured in sickle-cell patients (38 clinically asymptomatics and 27 during painful crisis) and healthy controls (n 5 25) using high-performance liquid chromatography(HPLC). PYD and DPD concentrations were higher in asymptomatic HbSS/HbSb0-thalassemia patients compared to controls (P <0.05) with further increments during painful crisis in both HbSS/HbSb0-thalassemia and HbSC/HbSb1-thalassemia patients (P < 0.05). In the asymptomatic HbSS/HbSb0-thalassemia patients, there was a statistically significant positive correlation between DPD and hemolytic rate.Based on urinary PYD and DPD concentrations, bone degradation is increased in asymptomatic sickle-cell patients, with further increments during painful crisis. Urinary PYD and DPD concentrations are potentially diagnostic and prognostic tools in SCD.     

Normal sublingual microcirculation during painful crisis in sickle cell disease

Obstruction of the microcirculation is the most important cause of painful crisis in sickle cell disease (SCD). Extensive microvascular obstruction has been observed in mouse models of SCD. A technique to determine the extent of the microcirculatory obstructions in humans may be helpful in the clinical setting and for research purposes. Therefore, we measured sublingual microcirculation longitudinally in patients with SCD admitted with painful crisis.Sublingual microcirculation was recorded with side-stream darkfield (SDF) imaging and semi-quantified with a microvascular flow index (MFI) on a range from 0 to 4 (arbitrary units; from 0 (no flow) to 4 (hyperdynamic flow)).Thirteen consecutive adult sickle cell patients admitted with painful crises were included and provided 47 measurements of MFI in 14 episodes of painful crisis. Seven patients provided baseline measurements and seven healthy controls were studied. The mean (± standard error of the mean) MFI during painful crisis was 2.6 ± 0.1 and did not change during the painful crisis. The mean MFI of patients with SCD during steady state (2.7 ± 0.1) and the mean MFI of the controls (2.7 ± 0.1) were not different from the mean MFI during painful crisis. During painful crisis irregular microvascular perfusion, expressed by the distribution width of the microvascular blood flow velocity, correlated negatively (r = − 0.484; P = 0.002) with hemoglobin concentration.We conclude that sublingual microcirculatory blood flow velocity is not disturbed in sickle cell patients during painful crisis.     

Plasma concentrations of asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, are elevated in sickle cell patients but do not increase further during painful crisis

Plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are elevated in the clinically asymptomatic state of sickle cell disease (SCD). However, the role of ADMA during vaso-occlusive complications has not been defined. ADMA concentrations were determined in HbSS (n = 43) and HbSC (n = 25) patients with healthy blood donors (HbAA) as controls. In the clinically asymptomatic state ADMA concentrations were elevated in sickle cell patients as compared to healthy controls (HbSS 0.70 micromol/L, HbSC 0.54 micromol/L, HbAA 0.39 micromol/L) (P < 0.001). Yet plasma ADMA concentrations did not increase further at presentation with a painful crisis implicating no role of primary importance during vaso-occlusive crises.     

Elevated IL-8 levels during sickle cell crisis

Abstract: The vaso-occlusive process (VOC) in sickle cell disease is of a complex nature. It involves intricate interactions between sickle red blood cells, endothelium and probably also leukocytes. As these interactions are regulated by cytokines, we analyzed the role of the potent neutrophil chemokine IL-8 by measuring serum levels in sickle cell patients during sickle cell crisis. These results were compared to nonsymptomatics and healthy controls. In patients having a vaso-occlusive crisis both HbSS and HbSC patients showed significantly enhanced serum IL-8 levels compared to healthy controls. Several of these patients showed extremely elevated serum IL-8 levels which were independent of the crisis inducing factor. Furthermore, a sickle cell patient with VOC as a complication of rhGM-CSF treatment similarly showed high IL-8 serum levels at crisis onset. Nonsymptomatic sickle cell patients serum IL-8 levels were comparable to healthy controls. These results implicate a role for IL-8 at or during (the initiation of) sickle cell crisis.     

Red blood cell changes during the evolution of the sickle cell painful crisis.

A longitudinal study of the red blood cell (RBC) deformability, percent of dense erythrocytes, and hematologic parameters has been conducted during 117 painful crises affecting 36 patients with sickle cell anemia between January, 1985 and December, 1990. RBC deformability was determined by osmotic gradient ektacytometry and the percentage of dense cells was quantitated by centrifugation on a discontinuous Stractan density gradient. The data indicate that the painful crisis is a process that follows a bimodal form of evolution. The first phase of the painful crisis is characterized by increase in the severity of pain, increase in the number of dense cells, and a decrease in RBC deformability. In some patients the changes in dense cells and RBC deformability are evident 1 to 3 days before the onset of pain. In addition, the hemoglobin level decreases and the reticulocyte count increases during this initial phase. The second phase of the crisis is characterized by reduction in pain intensity, decrease in the number of dense cells, and increase in RBC deformability to values higher than those seen in the steady state. Moreover, the improvement in RBC deformability and the decrease in the number of dense cells at the end of a crisis seem to constitute new risk factors that may incite a recurrence of the crisis within 1 month in about 50% of painful episodes. The pathophysiologic events responsible for this bimodal behavior of RBCs during painful episodes may represent the appearance of factors that induce (1) preferential trapping of deformable cells in the microcirculation during the first phase of the crisis, followed by a decrease of dense cells and the appearance of new deformable RBCs released from the bone marrow during the second phase of the crisis; or (2) variable sickling of all circulating RBCs during the first phase followed by disappearance of dense RBCs and their replenishment by deformable cells during the second phase.     

L-arginine levels are diminished in adult acute vaso-occlusive sickle cell crisis in the emergency department

Paediatric studies have demonstrated that l-arginine (l-arg), the precursor to nitric oxide, is diminished in vaso-occlusive crisis (VOC). This study aimed to determine whether l-arginine levels are altered in adult VOC in the emergency department. Plasma l-arg and nitric oxide metabolite (NOx) levels were obtained in adult VOC patients presenting to the emergency department. Fifty patients had significantly low plasma l-arg (29.78 micromol/l +/- 11.21, P < 0.05 vs steady-state control = 41.16 micromol/l +/- 5.04) and significantly low plasma NOx (12.33 micromol/l +/- 10.28, P < 0.05 vs steady-state control = 25.2 +/- 2.6 micro mol/l). Neither l-arg nor NOx levels could predict VOC clinical course.     

Erythrocyte sedimentation rate during steady state and painful crisis in sickle cell anemia

To define its diagnostic utility in sickle crisis, the erythrocyte sedimentation rates of oxygenated blood were studied in patients with sickle cell anemia and healthy normal subjects using the Guest-Westergren method. A normal range for sedimentation rate as a function of hematocrit was established in 22 normal subjects. Twenty-seven asymptomatic patients with sickle cell anemia had abnormally low sedimentation rates in relation to their hematocrits. Those low sedimentation rates were not increased by substituting plasma from healthy control subjects, which suggests that the low sedimentation rate was a cell-related phenomenon. Sedimentation rates measured in 28 patients with sickle cell anemia at the end of uncomplicated painful crisis increased to levels appropriate for their degree of anemia. In patients with sickle crisis and medical complications, the sedimentation rates were even higher. At the end of an uncomplicated painful crisis, the mean plasma fibrinogen level was significantly higher than at the onset (p less than 0.005). When red cells from patients with sickle cell anemia at the end of crisis were suspended in normal plasma from control subjects, the sedimentation rates remained high. It is concluded that the erythrocyte sedimentation rate of asymptomatic patients with sickle cell anemia is abnormally low due to cellular factors, and the increase during painful crisis is due primarily to red cell changes, modified by plasma factors.     

Plasma levels of agouti-related protein are increased in obese men

To investigate the relationship between peripheral blood levels of agouti-related protein (AGRP) and various parameters of obesity, we measured the plasma level of AGRP in 15 obese and 15 nonobese men and evaluated its relationship with body mass index (BMI), body fat weight, and visceral, sc, and total fat areas measured by computed tomography, fasting insulin levels, glucose infusion rate during an euglycemic hyperinsulinemic clamp study, serum leptin, and plasma alpha-MSH. Obese men had significantly higher plasma concentrations of AGRP than nonobese men (P < 0.01). Univariate analysis showed that the plasma levels of AGRP are proportionally correlated with BMI, body fat weight, and sc fat area in obese men (BMI: r = 0.732, P < 0.01; body fat weight: r = 0.603, P < 0.02; sc fat area: r = 0.668, P < 0.01) and in all men (BMI: r = 0.839, P < 0.0001; body fat weight: r = 0.818, P < 0.0001; sc fat area: r = 0.728, P < 0.0001). In all men, the plasma levels of AGRP were significantly correlated with the visceral fat area (r = 0.478, P < 0.01), total fat area (r = 0.655, P < 0.0001), fasting insulin level (r = 0.488, P < 0.01), glucose infusion rate (r = -0.564, P < 0.01), serum level of leptin (r = 0.661, P < 0.0001), and the plasma level of alpha-MSH (r = 0.556, P < 0.01). In all subjects, multiple regression analysis showed that the plasma levels of AGRP are significantly (F = 15.522, r = 0.801, P < 0.03) correlated with the plasma levels of alpha-MSH, independently from the total fat area. However, the correlation between plasma levels of AGRP and serum levels of leptin was found to be dependent on the total fat area. In brief, these findings showed that the circulating levels of AGRP are increased in obese men and that they are correlated with various parameters of obesity. Although correlation does not prove causation, the results of this study suggest that peripheral AGRP may play a role in the pathogenesis of obesity.     

Rheologic predictors of the severity of the painful sickle cell crisis

Deformable sickle erythrocytes have been reported by Mohandas and Evans to be more adherent to vascular endothelium than rigid irreversibly sickled cells (ISC). To define the clinical implications of this finding we have determined genetic, hematological, clinical, and rheological characteristics of sickle erythrocytes obtained from 65 patients with sickle cell anemia and fetal hemoglobin (Hb F) levels less than 15%. The alpha-globin gene number had a significant effect on the hematological parameters, the percentage of dense cells, ISC number, and HB A2 levels. The presence or absence of alpha thalassemia, however, had no effect on the frequency and severity of the sickle cell painful crisis (r = 0.06, P greater than .05). RBC deformability, determined by an ektacytometer, showed great heterogeneity among patients with three or four alpha-globin genes. Linear regression analyses of the data showed significant positive correlation of the frequency and severity of the painful crisis with RBC deformability (r = 0.49, P less than .001), and negative correlations with the percentage of dense cells (r = -0.37, P = .002), and the percentage of ISC (r = -0.46, P less than .001). We propose that the more deformable the sickle RBC are, the greater their adherence to vascular endothelium, and the more they cause vaso-occlusive crises, RBC deformability and the percentage of dense cells (or ISC) seem to have a predictive value of the frequency and severity of painful crises in sickle cell anemia.     

Non relationship of climatologic factors and painful sickle cell anemia crisis

Conflicting results have arisen from studies concerning the correlation (if any) between climatological changes and the frequency of painful episodes in the sickle cell population. During a 13 month period records of 71 patients with hemoglobin genotypes SS or SC were reviewed. Data analysis failed to reveal an association between the frequency of painful sickle cell crisis and a number of weather and environmental variables. We were unable to demonstrate relationships between the climatologic factors of temperature, humidity, carbon monoxide level and precipitation in the frequency of 362 pain crises in 71 sickle cell patients during a 13 month period.     

Oral analgesia for treatment of painful crisis in sickle cell anemia

A therapeutic plan that emphasized oral narcotic analgesia was instituted for the treatment of painful crisis of sickle cell anemia. Of the 100 adult sickle cell syndrome patients registered at North Central Bronx Hospital, 15 were identified as using the emergency department facilities three or more times per year. This "frequent user" patient population was tracked in their hospital and drug usage patterns during the first full year of the oral protocol and compared to their own patterns during the year prior to the protocol. The patients used the ED at the same rate but their frequency of admissions to the hospital dropped by 75%. The oral program produced a significant fall in the amount of narcotics dispensed in the ED (P less than .01).     

Kinetics of sickle cell biorheology and implications for painful vasoocclusive crisis

We developed a microfluidics-based model to quantify cell-level processes modulating the pathophysiology of sickle cell disease (SCD). This in vitro model enabled quantitative investigations of the kinetics of cell sickling, unsickling, and cell rheology. We created short-term and long-term hypoxic conditions to simulate normal and retarded transit scenarios in microvasculature. Using blood samples from 25 SCD patients with sickle hemoglobin (HbS) levels varying from 64 to 90.1%, we investigated how cell biophysical alterations during blood flow correlated with hematological parameters, HbS level, and hydroxyurea (HU) therapy. From these measurements, we identified two severe cases of SCD that were also independently validated as severe from a genotype-based disease severity classification. These results point to the potential of this method as a diagnostic indicator of disease severity. In addition, we investigated the role of cell density in the kinetics of cell sickling. We observed an effect of HU therapy mainly in relatively dense cell populations, and that the sickled fraction increased with cell density. These results lend support to the possibility that the microfluidic platform developed here offers a unique and quantitative approach to assess the kinetic, rheological, and hematological factors involved in vasoocclusive events associated with SCD and to develop alternative diagnostic tools for disease severity to supplement other methods. Such insights may also lead to a better understanding of the pathogenic basis and mechanism of drug response in SCD.Sickle cell disease (SCD) is characterized by acute and chronic vasoocclusion that can cause pain (1), acute chest syndrome (2), organ damage (3), stroke, and even death (4, 5). The pathogenic basis of “painful crisis” arising from vasoocclusion in SCD is extremely complex (6–8). It is triggered by many factors, including poor deformability of red blood cells (RBCs), adhesion among multiple cell types and blood components (e.g., sickle RBCs, endothelial cells, adherent leukocytes, and possibly platelets), as well as the local microenvironment (e.g., low oxygen concentration and acidosis). Under conditions of low oxygen partial pressure (pO₂), sickle RBCs experience intracellular sickle hemoglobin (HbS) polymerization, thereby reducing cell deformability (9). Such reductions in deformability can severely impact blood flow in narrow vessels, ultimately causing a transient or persistent blockage (10). Competition between the delay time for HbS polymerization and the RBC transit time in microcirculation is likely a key determinant of disease severity (11). Both in vitro (12) and ex vivo (13) models reveal that HbS polymerization and its effect on cellular rigidity play important roles in causing vascular obstruction. For example, HbS polymerization alone could be sufficient to cause complete RBC blockage in vasculature (12). Increases in microvascular transit time, arising from higher rigidity, of sickle RBCs cause peripheral vascular resistance to blood flow (13).The search for better means to predict painful vasoocclusion crises has focused on a range of hematological and rheological abnormalities. Significant correlations have been shown between pain rates and early death in patients with sickle cell anemia (14) and between early death and several risk factors such as fetal hemoglobin (HbF), hematocrit, and white cell count (15). However, factors such as patient age, sex, HbF (16), intracellular HbS polymerization (17), or fraction of dense RBCs (18) do not appear to show a sufficiently direct correlation with the frequency and/or severity of pain crises. Although HbF level is generally considered important, its direct connection to disease severity is not fully established (19, 20). Some possible links between the incidence of painful crises and steady-state cell hydration (21) and/or deformability at isotonic osmolarity have been identified (22). Such connections, however, do not account for the observation that cell deformability and the proportion of dense cells vary longitudinally in the same patient during crisis (23). Changes have also been reported in the biorheological characteristics of sickle RBC suspension following deoxygenation (DeOxy) in an in vitro vascular model (24).An in vitro model with a well-defined vascular structure and a well-controlled hypoxia condition would serve as an ideal tool to investigate many complex pathophysiological processes in vasoocclusion. Recent advances in microfluidics technology have enabled us to design unique in vitro capabilities with biophysically appropriate microenvironments that mimic the geometric features of vascular systems, thereby facilitating quantitative characterization of DeOxy blood flow (12, 24), detection of HbS polymerization in DeOxy liquid drops (25), and investigation of pathologic adhesion in blood rheology (26). Several methods have been developed to mimic oxygen depletion whereby HbS polymerization and subsequent cell sickling can be triggered; they include long-term gas perfusion at low pO₂ level (13, 27), DeOxy medium exchange (25, 28), reducing agents (29–31), and laser photodissociation of carbon monoxide (22, 32). Along with complex in vivo models that reflect the dynamic response of cells, an in vitro model would have the potential to predict the conditions that would lead to vasoocclusion and to improve the assessment of disease severity by quantifying the individual parameters that modulate vasoocclusion.We designed a microfluidic platform (Fig. 1) that mimics the rheology of microcirculation in vivo. It also characterizes the isolated effects of cell morphologic sickling, unsickling, and altered cell rheology. With this design, we explored in a systematic and controlled manner possible correlations of these effects with hematological parameters (e.g., %HbS), cell density, and hydroxyurea (HU) therapy.Open in a separate windowFig. 1.Microfluidic platform for investigation of biophysical alterations in sickle RBCs under transient hypoxia conditions. (A) Schematic of microfluidic device with O₂ control for studying kinetics of cell sickling and unsickling. (B) Identification of cell sickling events from a microscopic image (arrows indicate sickled RBCs). (C) Schematic of microfluidic device with capillary-inspired structures for single-cell rheology study. Note: Schematics are not drawn to scale, and the dimensions are in microns.Cell sickling was measured using a double-layer device with a cell channel (5 µm high), a gas channel (100 µm high), and an in-between polydimethylsiloxane (PDMS) film 150 µm in thickness (Fig. 1A). The O₂ concentration was controlled by exchanging gas flow in the channel through the PDMS membrane, which is gas-permeable (33). Although it is known (34) that the morphology of sickled cells depends on the DeOxy rate, we observed heterogeneity in cell morphology at the same DeOxy rate. Sickle RBCs typically form spiky edges and dark coarse texture due to intracellular HbS polymerization, the visual identification of which was enhanced by a band-pass filter (Fig. 1B and Movie S1). We thus define sickled cells as those obviously distorted from their original shape and/or texture under the Oxy state [O₂ concentration ∼20% (vol/vol)] to the DeOxy state (O₂ concentration <5%). This visual determination of cell sickling was further confirmed with an independent single-cell rheology test, where similar trends were observed in cell sickling and single-cell capillary obstruction (Results). The kinetics of cell sickling was quantified by two parameters: the sickled fraction (the fraction of all RBCs in the sample that are sickled) and the delay time of cell sickling (the time elapsed between the initiation of DeOxy and the point when a cell shows optically visible features of morphologic sickling). The delay time of cell unsickling was defined as the time elapsed between the initiation of reoxygenation (ReOxy) and the point when the RBC fully recovered its presickle morphology in a visibly identifiable manner.Individual-cell rheology was measured using a microfluidic channel that consisted of periodic obstacles forming microgates 4 µm wide, 5 µm deep, and 15 µm long (Fig. 1C). The channel dimensions were chosen to mimic the size of the smallest capillaries in the human body (4–10 µm in diameter) (35). Cell velocity was measured as the average velocity of individual RBCs flowing through periodic gates under a constant differential pressure. The obstruction fraction was determined as the ratio of obstructed RBCs to all RBCs entering into the microgate arrays during the DeOxy period.     

The painful crisis of homozygous sickle cell disease: clinical features

The details of onset, perceived precipitating factors, associated symptoms, and pain distribution in the painful crisis of homozygous sickle cell (SS) disease have been prospectively recorded in 183 painful crises in 118 patients admitted to a day-care centre in Kingston, Jamaica. Painful crises developed most frequently between 3 p.m. and midnight, most commonly affected patients aged 15-29 years, affected the sexes equally, and were not obviously influenced by menstrual cycle. Of the perceived precipitating factors, skin cooling occurred in 34%, emotional stress in 10%, physical exertion in 7%, and pregnancy in 5% of women of child-bearing age. Cold as a precipitant was not less common in patients with more subcutaneous fat. Pain affected the lumbar spine in 49%, abdomen in 32%, femoral shaft in 30%, and knees in 21%. There was a highly significant excess of bilateral involvement in limb and rib pain. Recurrent painful crises occurred in 40 patients but showed no evidence of involving similar sites on successive occasions. Abdominal painful crises were associated with abdominal distention in 18 (31%) and with referred rib pain in a further 15 (26%) of crises. Fever was common even in apparently uncomplicated painful crises, suggesting that fever is characteristic of the painful crisis itself and not necessarily indicative of infection. Following investigation and treatment in a day-care centre, over 90% of patients returned home.     

Erythropoiesis in sickle cell anaemia during acute infection and crisis.

Erythropoiesis was evaluated in 37 patients with sickle cell anaemia, 26 of them children under 12 years of age. Mean haemoglobin, haematocrit, reticulocyte, and erythropoietin levels were similar for 11 who were asymptomatic, 11 with infections, and 12 in vaso-occlusive crisis. Mean haemoglobin, haematocrit, and reticulocyte values were significantly lower and the mean erythropoietin level significantly higher for three patients in aplastic crisis. Reticulocyte counts reflected erythropoietic activity during the asymptomatic state but were variable during infection and crisis. No erythropoietic inhibitory activity was found in any of the four clinical states. It has been suggested that erythropoietin production decreases during infection. Patients in this study responded appropriately to stress, showing no decrease in erythropoietic activity during acute infection or crisis.     

Management of acute painful crises in sickle cell disease

Pain is a common mode of manifestation of sickle cell disease (SCD) but there is limited information on pain management in this disorder. This study examines the use of opioids and non-opioid analgesia in the management of painful crisis in adult SCD patients; the routine use of antimalarials and antibiotics as adjunct therapy was also examined. A total of 87% of the patients had had a form of analgesics before presentation, 20% of which had parenteral analgesia. Ten per cent had not used any form of medication while another 10% used non-steroidal anti-inflammatory drugs. When asked, 59% of the patients desired oral non-opioid analgesics while 31% were not concerned about the type of analgesic given. Only 8% requested opioids. Hospital admission was not necessary in 65% of the patients; they were observed in the day-care unit and allowed home within 24 h. Sixty per cent did not have a test for malaria; 66% of those who had the test performed were negative, 35% of those whose thick film for malaria was negative had antimalarials prescribed. Only five patients (7%) were febrile at presentation. Thirty-four per cent had antibiotics prescribed, a third of these parenterally. Thirty-nine per cent had no fever but received antibiotics.