Logo: to the web site of Uppsala University

Fluid resuscitation is essential to antagonize the deleterious effects of tissue hypo-perfusion in sepsis. If not thoroughly monitored and individually tailored, fluid therapy increases the risk of volume overload. Volume overload is associated with higher mortality in sepsis. Although considerable progress has been made to understand the complex nature of the cardiovascular derangements in sepsis and septic shock, the optimal fluid resuscitation strategy is yet to be defined. Current guidelines recommend balanced crystalloids and albumin for resuscitation; synthetic colloids are harmful and no longer in use. In search of adjuvant therapies to fluid resuscitation in sepsis and sepsis related complications with a volume sparing potential, this doctoral thesis aimed at exploring the effects of two endogenous molecules involved in fluid homeostasis.

In Study I, the peptide containing the active site of the endogenous protein antisecreterory factor (AF-16) reduced lung edema formation, as reflected in a reduction in extra vascular lung water (EVLW), in a model of ventilator induced lung injury (VILI). The aim of Study I was to test the intervention AF-16 in a well-established porcine model of lung edema and capillary leak.

In Study II, the intervention AF-16 was tested in a model of fecal peritonitis sepsis. The first aim of Study II was to elaborate a clinically relevant porcine model of fecal peritonitis-sepsis, including a standardized resuscitation protocol. Second aim was to test the effect of the intervention on volume status and inflammation. Wet-to-dry ratio was lower in liver samples of the intervention group, indicating less edema formation. No other differences were detected between intervention and control groups.

In Study III, the intervention high molecular weight hyaluronan (HMW-HA) was tested in our model of fecal peritonitis as adjuvant to standardized fluid resuscitation. Fluid balance and the inflammatory response were comparable throughout the experiment in the intervention and control groups. The intervention counteracted the increase in proportion of fragmented hyaluronan associated with peritonitis-sepsis and was associated with lower modified shock index (MSI) than placebo.

In Study IV, we administered an increased dose of HMW-HA directly after induction of peritonitis. The aim of Study IV was to study the effects of the intervention in a fluid restrictive model, to reduce a potentially negative effect of crystalloid infusion per se on the endothelial glycocalyx layer. In Study IV, hemodynamics and surrogate markers of endothelial damage were comparable in the intervention and control groups. The intervention was associated with an increase in cardiac output and diastolic blood pressure during the infusion, these effects disappeared as the experiment proceeded. Lactate was higher in the intervention group as a function of time.

Septic shock results from a dysregulated host response to infection, leading to life-threatening organ dysfunction. Limited treatment options and a heterogeneous, complex pathophysiology make septic shock a major challenge for clinicians and researchers. Hyaluronan is a versatile molecule that may influence several biological processes disrupted in septic shock, including macro- and microcirculation, endothelial and glycocalyx integrity, intravascular volume, and inflammation. This thesis aimed to deepen understanding of hyaluronan and its associated proteins in septic shock and to explore potential new treatments.

Study I analysed plasma hyaluronan, hyaluronidase activity, and endogenous hyaluronidase inhibition in experimental and clinical septic shock and in acute alcohol-related pancreatitis. Both the experimental control group and septic shock groups showed increased plasma hyaluronan and hyaluronidase inhibition with decreased hyaluronidase activity. This pattern was also observed in clinical septic shock, but in alcohol-related pancreatitis only plasma hyaluronidase activity was reduced.

Study II evaluated high-molecular-weight hyaluronan as an adjuvant to fluid resuscitation at the onset of septic shock in an experimental peritonitis model. A hyaluronan injection followed by infusion throughout the experiment did not reduce resuscitation requirements or alter the inflammatory response.

Study III investigated higher exposure to high-molecular-weight hyaluronan during the early phase of peritonitis-induced septic shock. Hyaluronan infusion, started immediately after induction of peritonitis, did not prevent vascular depletion after 6 hours, nor did it preserve glycocalyx integrity.

Study IV compared proteomic profiles of hyaluronan-related proteins between septic shock and acute alcohol-related pancreatitis. 663 proteins were identified of which 231 were up- or downregulated in septic shock and fifteen were identified as hyaluronan-related. Changes were more pronounced on day 1 than on day 4, and more marked in septic shock than in pancreatitis. Heavy chains of the inter-alpha-inhibitor family showed marked changes: ITIH1, ITIH2, and ITIH4 were decreased, whereas ITIH3 was increased.

In summary, plasma hyaluronan and endogenous hyaluronidase inhibition increased whereas hyaluronidase activity decreased in experimental and clinical septic shock. Supraphysiological hyaluronan concentrations did not prevent intravascular volume depletion, nor did they alter the inflammatory response or preserve glycocalyx integrity. Proteomic profiles of hyaluronan-related proteins differed markedly between septic shock and alcohol-induced pancreatitis.