Synthetic colloids represent a major type of intravenous fluid used in human and veterinary medicine. Hydroxyethyl Starch (HES) solutions represent the major class of colloid used for volume resuscitation in hypotensive patients. The advantage of HES solutions has been their ability to restore blood pressure and circulating volume in critical patients while avoid the large volumes, extravasation, and fluid overload associated with crystalloids and the transfusion reactions associated with plasma and albumin.
HES solutions were a mainstay of critical care for over 30 years, until several papers and consensus statements published recently indicated a high risk of acute kidney injury (AKI) in human patients. This data was convincing and concerning to the point that several agencies banned the use of HES in human patients, and it is now widely considered contraindicated in patients with critical illness, sepsis, burns, coagulopathies, or other conditions. It is largely restricted to patients with acute haemorrhage where blood transfusion is not an option.
In veterinary medicine there is significant debate as to the risks and benefits of colloid solutions. Several recent veterinary papers have been published with contradictory conclusions. While it may make intuitive sense that veterinary patients are equally susceptible, cats and dogs have a different physiology than humans and generally receive lower colloid doses over shorter hospital stays. Plasma and albumin are also much less available in veterinary than human medicine, especially in veterinary species. In the few veterinary studies that exist, feline patients have been ignored or under represented.
The authors of this paper attempted to establish if the use of HES solutions in cats is associated with the development of acute kidney injury. The study was a retrospective observational design. Cats admitted to the ICU from 2010 to 2015 with at least two creatinine measurements with the first within the reference range. They were excluded if they did not receive IV fluids between measurements or if they had a history of receiving HES. The HES variant used by this clinic was 6% tetrastarch 130/0.4 (Voluven).
All cats were evaluated for signalment, pre and post creatinine values, total HES dose, survival to discharge, and a wide array of other clinical and laboratory findings. The presence of SIRS (systemic inflammatory response syndrome) criteria and APPLEfull scores were also determined. The presence of AKI was determined by the IRIS scoring system and the VAKI system.
Cats who received only crystalloids were assigned to one group, and cats who received any amount of HES to the other. Groups were subdivided by SIRS and sepsis criteria. 93 cats were included in total, 62 receiving crystalloids and 31 HES. Most cats were domestic shorthairs with pancreatic or hepatobiliary disease, polytrauma, or pyothorax. Cats in the HES group received a median of 94mL/kg HES over 3.7 days.
Cats in the HES group had a longer hospitalization, lower hematocrit, higher APPLEfull score, and higher rate of SIRS or sepsis at admission. This is likely due to clinicians reserving the use of HES for the sickest animals.
No difference in mortality was seen between groups. Additionally, cumulative HES dose had no effect on mortality, nor did APPLE score or the presence of SIRS/Sepsis.
Most significantly, no difference was found in creatinine levels or in change in creatinine between the crystalloid and HES group. By IRIS criteria, 2 crystalloid and 4 colloid cats developed AKI; by the VAKI system 4 cats in each group developed AKI. These differences were not statistically significant.
This study concluded that there was no evidence for HES induced AKI In the cats in this study population. Further, HES was not associated with a higher risk of mortality in hospitalized cats. The authors proposed several mechanisms for this, including decreased sensitivity to colloids, lower doses, shorter hospital stays, and less severe disease compared to human patients.
There are several shortfalls to this study, including its retrospective nature, the presence of more severe disease in colloid treated cats, and the relatively small sample size. The exclusion of cats with pre-existing renal disease simplified data analysis however it is unclear what role this may play in the development of AKI. These facts aside, this paper provides much needed early information on the risk and utility of HES use in feline patients. (MRK)