Effects of 6% hetastarch (600/0.75) or lactated Ringer's solution on hemostatic variables and clinical bleeding in healthy dogs anesthetized for orthopedic surgery

Effects of Hyperbaric Oxygen Therapy on Hemogram, Serum Biochemistry and Coagulation Parameters of Dogs Undergoing Elective Laparoscopic-Assisted Ovariohysterectomy

BACKGROUND

This study explored the effects of hyperbaric oxygen therapy (HBOT) on hemogram, serum biochemistry and hemostatic variables in female dogs undergoing laparoscopic-assisted ovariohysterectomy (OVH).

MATERIALS

Thirty adult, mixed-breed, healthy female dogs were randomly divided into the following three groups: HBOT + SURG (exposed to two absolute atmospheres (ATAs) for 45 min followed by laparoscopic-assisted OVH), HBOT (exposed to two ATAs for 45 min) and SURG (laparoscopic-assisted OVH). Blood samples were collected at T0 (at the admission), at T1, 24 h after T0 (immediately after HBOT in the HBOT + SURG and HBOT groups, and immediately before anesthetic premedication in the SURG group), and at T2, 48 h after T0 (24 h after HBOT and anesthetic premedication).

METHODS

Assessments included erythrogram, leukogram, thrombogram, renal and hepatic serum biochemistry, prothrombin time (PT), activated partial thromboplastin time (APTT), buccal mucosal bleeding time (BMBT) and bloodstain area (BA) on hygroscopic paper collected at the BMBT.

RESULTS

Both the HBOT + SURG and SURG groups presented neutrophilia (p ≤ 0.0039) at T2 and an increase of ALP at T2 (p ≤ 0.0493), the SURG group presented an increase in leukocyte count at T2 (p = 0.0238) and the HBOT + SURG group presented a reduction in lymphocyte count at T2 (p = 0.0115). In the HBOT + SURG group, there was a reduction in PT and APTT in relation to the baseline value (p ≤ 0.0412).

CONCLUSIONS

A session of HBOT at two ATAs for 45 min did not cause changes in the BMBT or BA in healthy female dogs. Some blood parameters investigated (neutrophil and lymphocyte count, ALP, PT and APTT) were affected by the use of HBOT.

A Comparison of Dobutamine, Norepinephrine, Vasopressin, and Hetastarch for the Treatment of Isoflurane-Induced Hypotension in Healthy, Normovolemic Dogs

Isoflurane is a commonly used inhalation anesthetic in species undergoing veterinary care that induces hypotension, impacting organ perfusion, making it imperative to minimize its occurrence or identify effective strategies for treating it. This study evaluated and compared the hemodynamic effects of DOB, NEP, VAS, and HES in twelve isoflurane-anesthetized Beagle dogs. The order of the first three treatments was randomized. HES was administered last. Data were collected before treatments (baseline) and after 10 min of a sustained MAP of <45 mmHg induced by a high end-tidal isoflurane concentration (T0). Once treatment was initiated and the target MAP was achieved (65 to 80 mmHg) or the maximum dose reached, data were collected after 15 min of stabilization (T1) and 15 min after (T2). A 15 min washout period with a MAP of ≥65 mmHg was allowed between treatments. The intravenous dosage regimens started and were increased by 50% every five minutes until the target MAP or maximum dose was reached. The dosages were as follows: DOB, 5-15 μg/kg/min; NEP, 0.1-2 μg/kg/min; VAS, 0.5-5 mU/kg/min; and HET, 6% 1-20 mL/kg/min. DOB improved CO, DO2, and VO2, but reduced SVR. VAS elevated SVR, but decreased CO, DO2, and VO2. HES minimally changed BP and mildly augmented CO, DO2, and VO2. These treatments failed to reach the target MAP. NEP increased the arterial BP, CO, MPAP, and PAWP, but reduced HR. Norepinephrine infusion at 0.44 ± 0.19 μg/kg/min was the most efficient therapy for correcting isoflurane-induced hypotension.

Evaluation of Haemostasis in Dogs Affected by Resectable Malignancy

Dogs with neoplasm are at risk of thrombosis, yet there is no information on the haemostatic alterations that may result from the surgeries performed to remove neoplastic masses. The aim of this study was to observe the characteristics of haemostasis in dogs undergoing surgery to remove a malignancy by means of rotational thromboelastometry and thrombin generation. Haemostasis was assessed immediately before surgery (T0), 24 h after surgery (T1), and two weeks after surgery (T2). Statistically significant differences were found between the thromboelastometric parameters at T0 vs. T1, with increases observed in MCF, the α angle, and G parameters in the ex-TEM and in-TEM profiles. In the thromboelastometric analysis performed after surgery differences were identified between T1 and T2, with a decrease observed in parameters such as CFT, MCF, the α angle, and G. Between T0 and T2, only a significant decrease in CT was detected in the fib-TEM profile. No differences were found in the comparison among the results obtained via thrombin generation. In dogs with resectable malignancies, the surgeries performed to remove cancer affected coagulation, causing a tendency towards hypercoagulability. The interference with coagulation was transient, and 2 weeks after surgery, the thromboelatometric results returned to those obtained before surgery (T0).

Impact of general anesthesia on rotational thromboelastometry (ROTEM) parameters and standard plasmatic coagulation tests in healthy Beagle dogs

OBJECTIVE

To assess the influence of general anesthesia on rotational thromboelastometry (ROTEM) and standard coagulation testing in healthy dogs.

STUDY DESIGN

Prospective experimental study.

ANIMALS

10 healthy Beagle dogs.

METHODS

Dogs were administered methadone (0.2 mg/kg) intramuscularly. Anesthesia was co-induced intravenously 30 min later with midazolam (0.1 mg/kg) and propofol to effect, and maintained with sevoflurane. Crystalloids were administered at 5 ml/kg/h. Blood was sampled by direct venipuncture before induction (T0) and 3.5 h later (T3.5) and ROTEM parameters (ExTEM, InTEM, FibTEM, ApTEM), standard plasmatic coagulation tests (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration), hematology, ionized calcium, triglycerides, pH, lactate and body temperature were compared over time with Students t - test or Wilcoxon matched pairs signed-rank tests.

RESULTS

The following variables dropped significantly between T0 and T3.5: body temperature (p < 0.0001), hematocrit (p < 0.0001), platelet count (p < 0.01), pH (p < 0.01), triglycerides (p < 0.01), fibrinogen concentration (p < 0.01), ExTEM, FibTEM (p < 0.01) and ApTEM (p < 0.05) clotting times. Lactate concentration (p < 0.01), aPTT (p < 0.05) and FibTEM maximum clot firmness increased (p < 0.05). No changes were noted in ionized calcium, PT and InTEM values.

CONCLUSION AND CLINICAL RELEVANCE

General anesthesia with concurrent hemodilution and hypothermia induced significant but clinically irrelevant changes in coagulation variables measured at 37 °Celsius. Blood samples from anaesthetized animals can be used for determination of coagulation status in dogs.

Assessment of hemostasis in dogs with gastric-dilation-volvulus, during resuscitation with hydroxyethyl starch (130/0.4) or hypertonic saline (7.5%)

OBJECTIVE

To compare the impact of an IV bolus of hydroxyethyl starch 130/0.4 (HES) or hypertonic saline 7.5% (HS) on hemostasis in dogs resuscitated for gastric-dilation-volvulus (GDV).

DESIGN

Open-label, parallel-group randomized clinical trial.

ANIMALS

Twenty-three client-owned dogs.

INTERVENTIONS

Dogs affected by GDV and shock were randomly assigned to receive HES at 10 mL/kg or HS at 4 mL/kg every 15 minutes. Blood samples were collected for blood gas analysis, PCV, total plasma protein, albumin, standard coagulation profile, and thromboelastometry (ROTEM) at baseline (T0) and at the end of bolus (T1). To assess the differences between the 2 groups at T1, Student's t-test or Wilcoxon rank-sum test was used. To evaluate the differences between T0 and T1, ANOVA for paired data or Wilcoxon matched-pairs signed-ranks test was used. P < 0.05 was considered significant.

MEASUREMENT AND MAIN RESULTS

Hemostasis was evaluated by means of prothrombin time, activated partial thromboplastin time, fibrinogen, and ROTEM. The study included 13 dogs in the HES group and 10 dogs in the HS group. Differences were found between groups at T1: increase in clotting time (P = 0.018) and decrease in fibrinogen level (P = 0.021) in the HS-treated group. Between T0 and T1, there were differences for the HES group: increase in clot formation time (P = 0.046), decrease in maximum clot firmness (P = 0.002) in ex-TEM profile, and decrease in maximum clot firmness (P = 0.0117) in fib-TEM profile. Between T0 and T1, the following differences were noted for the HS group: increase in clotting time (P = 0.048) and clot formation time (P = 0.0019), decrease in maximum clot firmness (P = 0.031) and α angle (P = 0.036) in ex-TEM profile, decrease in α angle (P = 0.036) in in-TEM profile, and decrease in maximum clot firmness (P = 0.017) in fib-TEM profile.

CONCLUSION

In dogs affected by GDV, HES or HS infusion caused a similar tendency toward hypocoagulability, with few differences between the 2 groups.

Intravenous Fluid Administration and the Coagulation System

Intravenous fluid administration in veterinary patients can alter coagulation function by several mechanisms. Both crystalloid and colloid fluids cause hemodilution, reducing platelet count and plasma coagulation protein concentrations. Hemodilution is associated with a hypercoagulable effect at low dilutions and a hypocoagulable effect at higher dilutions. Composition of crystalloid fluids likely has a minor effect, primarily dependent on fluid ion composition. Hypertonic crystalloids may also cause hypocoagulability. Colloids, both synthetic and natural, can cause hypocoagulability by several mechanisms beyond the effects of hemodilution. These include impaired platelet function, decreased plasma coagulation factor activity, impaired fibrin formation and crosslinking, and accelerated fibrinolysis. The vast majority of the veterinary literature investigates the hypocoagulable effects of hydroxyethyl starch-containing fluids using in vitro, experimental, and clinical studies. However, results are inconsistent, likely due to the varying doses and physicochemical properties of the specific fluid products across studies. In addition, some evidence exists for hypocoagulable effects of gelatin and albumin solutions. There is also evidence that these colloids increase the risk of clinical bleeding in people. Limitations of the veterinary evidence for the hypocoagulable effects of colloid fluids include a predominance of in vitro studies and in vivo studies using healthy subjects, which exclude the interaction of the effects of illness. Therefore, clinical relevance of these effects, especially for low-molecular-weight hydroxyethyl starch, is unknown. Firm recommendations about the most appropriate fluid to use in clinical scenarios cannot be made, although it is prudent to limit the dose of synthetic colloid in at-risk patients. Clinicians should closely monitor relevant coagulation assays and for evidence of hemorrhage in at-risk patients receiving any type of fluid therapy, especially in large volumes.

Evaluation of the effects of hydroxyethyl starch (130/0.4) administration as a constant rate infusion on plasma colloid osmotic pressure in hypoabluminemic dogs

OBJECTIVE

To evaluate the effects of 2 constant rate infusions of hydroxyethyl starch (HES) 130/0.4 on plasma colloid osmotic pressure (COP) in hypoalbuminemic dogs.

DESIGN

Prospective, randomized clinical trial.

ANIMALS

A total of 24 client-owned dogs.

INTERVENTIONS

Hypoalbuminemic euvolemic dogs (albumin < 20 g/L [<2 g/dL]) with normal perfusion parameters requiring IV fluid therapy were enrolled. In addition to crystalloid, HES 130/0.4 was administered as a constant rate infusion over 24 hours at 1 mL/kg/h (group 1, n = 15) or at 2 mL/kg/h (group 2, n = 9), in order to support plasma COP. Before infusion, a blood sample was collected to perform CBC, serum electrophoresis, and serologic tests for some infective diseases. Plasma COP, albumin concentration, PCV, and total plasma protein concentration were evaluated serially at baseline (T0) and then at 6, 12, and 24 hours after the start of infusion, and a multilevel model was performed for these parameters to detect statistically significant differences between the 2 groups.

MEASUREMENT AND MAIN RESULTS

Twenty-four dogs were included. No statistically significant differences in COP were found between the 2 groups; however, a high level of variability has been identified within the single individual. Among the other laboratory analyses, PCV was significantly decreased in group 1 at T12 and T24 compared with T0 (P < 0.001) and total plasma protein concentration was significantly increased in group 2 at T12 and T24 compared with T0 (P < 0.008).

CONCLUSION

No significant effect on plasma COP was found following infusion with HES 130/0.4 at doses of 1 mL/kg/h and 2 mL/kg/h for 24 hours to hypoalbuminemic dogs. The administered concomitant dose of crystalloids, underlying disease, and small sample size were all potential confounding factors.

Spontaneous hemoperitoneum and anaphylactic shock associated with Hymenoptera envenomation in a dog

OBJECTIVE

To describe the clinical presentation of a dog with spontaneous hemoperitoneum associated with anaphylactic shock from Hymenoptera envenomation.

CASE SUMMARY

An 8-year-old female neutered Beagle presented as an emergency for acute onset of collapse, hematemesis, and hematochezia. The dog was tachycardic, tachypneic, and hypotensive. Initial assessment revealed a hemoperitoneum with documentation of a nonclotting sanguineous peritoneal effusion with PCV 81% and total protein concentration 65 g/L (6.5 g/dL). No obvious masses were appreciated ultrasonographically during original presentation and cytology of the peritoneal effusion was unremarkable. Peripheral PCV was 67% and total plasma protein concentration was 72 g/L (7.2 g/dL). A bee stinger was located in the right upper lip after presentation and was postulated to be the inciting trigger for the abdominal hemorrhage and shock. The patient was medically stabilized and ultimately made an uneventful recovery. Abdominal ultrasound performed 3 days after discharge revealed a single 0.85 cm hyperechoic liver nodule. Follow-up evaluation at 6 and 18 months after presentation documented a normal physical examination, unremarkable thoracic radiographs, and no change in the original hyperechoic liver nodule.

NEW OR UNIQUE INFORMATION PROVIDED

This report details an unusual clinical presentation of anaphylactic shock due to Hymenoptera envenomation in a dog. To the authors' knowledge, spontaneous hemoperitoneum associated with anaphylaxis and bee envenomation has not been documented in the veterinary literature.

Thromboelastometric assessment of hemostasis following hydroxyethyl starch (130/0.4) administration as a constant rate infusion in hypoalbuminemic dogs

BACKGROUND

The primary aim was to evaluate by means of thromboelastometry (ROTEM) the effects of hydroxyethyl starch (HES) 130/0.4 administered as a constant rate infusion (CRI) on hemostasis in hypoalbuminemic dogs. The second aim was to use ROTEM analysis to detect whether all hypoalbuminemic dogs of our population were hypercoagulable.

RESULTS

The study sample was 20 hypoalbuminemic dogs (albumin < 2 g/dl) with normal perfusion parameters and requiring intravenous fluid therapy. In order to support plasma colloid osmotic pressure, in addition to crystalloid, HES 130/0.4 was administered as a constant rate infusion at 1 ml/kg/h (group 1, n = 11) or 2 ml/kg/h for 24 h (group 2, n = 9). Blood samples were collected at baseline (T0) and 24 h postinfusion (T1); coagulation was assessed by standard coagulation profile (prothrombin time, activated partial thromboplastin time, and fibrinogen), and ROTEM analysis (in-TEM®, ex-TEM® and fib- TEM® profile). No statistically significant differences in ROTEM values in group 1 were observed (P > 0.05), whereas in group 2 statistically significant differences (P < 0.05) were found at T1 in the in-TEM® profile [decrease in clot formation time (P = 0.04) and increase in α angle (P = 0.02)] and in the ex-TEM® profile [increase in maximum clot firmness (P = 0.008) and α angle (P = 0.01)]; no changes were identified in the fib-TEM® profile. In both groups, a statistically significant decrease (P = 0.007) in hematocrit was noted, whereas no statistically significant differences in platelet count and standard coagulation profile were found. In group 2, a statistically significant increase in TS values (P = 0.03) was noted at T1. ROTEM tracings indicating a hypercoagulable state were observed in 7/20 dogs at T0 (5/11 in group 1 and 2/9 in the group 2).

CONCLUSION

Our findings suggest that HES 130/0.4 administered as CRI does not cause hypocoagulability in hypoalbuminemic dogs. A trend toward hypercoagulability, probably related to the underlying diseases, was observed in group 2 at T1. Although all dogs were hyoalbuminemic, only 7/20 were hypercoagulable at T0, confirming the lack of correlation between albumin level and prothrombotic state.

Rapid exacerbation of renal function after administration of hydroxyethyl starch in a dog

Hydroxyethyl starches (HES) are commonly used synthetic colloidal solution in veterinary medicine. Despite of possible adverse effect to kidney injury in human, there is no report about nephrotoxic effects of HES in dogs. HES was administered to a Golden retriever (4-year-old, intact male) with ascites in order to increase plasma osmolality. Initially, the dog was mild azotemic, however, kidney function was rapidly deteriorated after several days of HES administration. Finally, histopathological examination revealed remarkable osmotic nephrosis. In the case reported herein, acute kidney injury was remarkably developed after HES administration. Clinical and histopathologic findings of acute kidney injury support nephrotoxic effects of HES to a dog.

Comparison of the effects of a balanced crystalloid-based and a saline-based tetrastarch solution on canine whole blood coagulation and platelet function

OBJECTIVE

To evaluate the effects of a 6% hydroxyethyl starch (130/0.42) solution in either a buffered, electrolyte-balanced (HES-BAL), or a saline (HES-SAL) carrier solution on canine platelet function and whole blood coagulation.

DESIGN

Prospective, randomized study.

SETTING

University teaching hospital.

ANIMALS

Thirty-seven client-owned dogs undergoing general anesthesia for arthroscopy or imaging studies.

INTERVENTIONS

Dogs received a 15 mL/kg intravenous bolus of HES-SAL (n = 13), HES-BAL (n = 14), or a modified Ringer's solution (n = 10) over 30-40 minutes. Coagulation was analyzed using a Platelet Function Analyzer-100 (closure time [Ct_PFA ]), and whole blood thromboelastometry (ROTEM) with extrinsically (ex-tem and fib-tem) and intrinsically (in-tem) activated assays, which assessed clotting time (CT), clot formation time (CFT), maximal clot firmness (MCF), and lysis index (LI). Coagulation samples were assayed prior to fluid administration (T0), and 5 minutes (T1), and 3 hours (T2) following fluid bolus administration, respectively.

RESULTS

Both HES solutions resulted in impaired platelet function as indicated by a significant prolongation of Ct_PFA at T1 as compared to T0, but which resolved by T2. An IV bolus of Ringer's solution did not alter platelet function. In both HES groups, whole blood coagulation was significantly impaired at T1 as indicated by a significant increase in in-tem CFT, and a significant decrease in ex-tem, in-tem, and fib-tem MCF compared to T0. Furthermore, a significant increase in ex-tem CFT at T1 compared to T0 was found in the HES-SAL group. With the exception of in-tem MCF after HES-BAL, these effects were not present at T2. No significant differences were found in Ct_PFA or any ROTEM variable at any time point between HES-SAL and HES-BAL.

CONCLUSION

Administration of a single bolus of 15 mL/kg 6% HES 130/0.42 results in significant but short-lived impairment of canine platelet function and whole blood coagulation, regardless of carrier solution.

Natural and Synthetic Colloids in Veterinary Medicine

This review article covers basic physiology underlying the clinical use of natural and artificial colloids as well as provide practice recommendations. It also touches on the recent scrutiny of these products in human medicine and how this may have an effect on their use in veterinary medicine.

Retrospective evaluation of the effects of administration of tetrastarch (hydroxyethyl starch 130/0.4) on plasma creatinine concentration in dogs (2010-2013): 201 dogs

OBJECTIVE

To determine changes in creatinine concentrations following the administration of 6% tetrastarch (hydroxyethyl starch [HES] 130/0.4) compared to crystalloids (CRYSs) in critically ill dogs.

DESIGN

Retrospective case series (2010-2013).

SETTING

University teaching hospital.

ANIMALS

Two hundred and one dogs admitted to the intensive care unit with initial plasma creatinine concentrations not exceeding laboratory reference intervals (52-117 μmol/L [0.6-1.3 mg/dL]) and receiving either CRYSs alone (CRYS group, n = 115) or HES with or without CRYSs (HES group, n = 86) for at least 24 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Creatinine concentrations at admission to the intensive care unit (T0), and 2-13 days (T1) and 2-12 weeks (T2) after initiation of fluid therapy were analyzed. Creatinine concentrations were analyzed as absolute values and as the maximum percentage change from T0 to T1 (T1max%) and from T0 to T2 (T2max%), respectively. Creatinine concentrations were available for 192 dogs during T1 and 37 dogs during T2. The median cumulative dose of HES was 86 mL/kg (range, 12-336 mL/kg). No difference was detected between the groups for age, gender, body weight, and length of hospitalization. Outcome was significantly different between the HES (66% survived) and the CRYS (87% survived) groups (P = 0.014). No significant difference was detected between groups for creatinine concentrations at T0, T1, T2, T1max%, or T2max%. No significant difference was detected between the groups for T1max% creatinine in dogs subclassified as having systemic inflammatory response syndrome or sepsis.

CONCLUSIONS

HES administration in this canine population did not result in increased creatinine concentrations compared to administration of CRYSs. Further studies are needed to establish the safety of HES in critically ill dogs.

Controversies in the use of hydroxyethyl starch solutions in small animal emergency and critical care

OBJECTIVES

To (1) review the development and medical applications of hydroxyethyl starch (HES) solutions with particular emphasis on its physiochemical properties; (2) critically appraise the available evidence in human and veterinary medicine, and (3) evaluate the potential risks and benefits associated with their use in critically ill small animals.

DATA SOURCES

Human and veterinary original research articles, scientific reviews, and textbook sources from 1950 to the present.

HUMAN DATA SYNTHESIS

HES solutions have been used extensively in people for over 30 years and ever since its introduction there has been a great deal of debate over its safety and efficacy. Recently, results of seminal trials and meta-analyses showing increased risks related to kidney dysfunction and mortality in septic and critically ill patients, have led to the restriction of HES use in these patient populations by European regulatory authorities. Although the initial ban on the use of HES in Europe has been eased, proof regarding the benefits and safety profile of HES in trauma and surgical patient populations has been requested by these same European regulatory authorities.

VETERINARY DATA SYNTHESIS

The veterinary literature is limited mostly to experimental studies and clinical investigations with small populations of patients with short-term end points and there is insufficient evidence to generate recommendations.

CONCLUSIONS

Currently, there are no consensus recommendations regarding the use of HES in veterinary medicine. Veterinarians and institutions affected by the HES restrictions have had to critically reassess the risks and benefits related to HES usage based on the available information and sometimes adapt their procedures and policies based on their reassessment. Meanwhile, large, prospective, randomized veterinary studies evaluating HES use are needed to achieve relevant levels of evidence to enable formulation of specific veterinary guidelines.

Platelet closure time in anesthetized Greyhounds with hemorrhagic shock treated with hydroxyethyl starch 130/0.4 or 0.9% sodium chloride infusions

OBJECTIVE

To measure platelet closure time (PCT) in dogs during controlled hemorrhagic shock and after fluid resuscitation with hydroxyethyl starch (HES) 130/0.4 or 0.9% sodium chloride.

DESIGN

Experimental interventional study.

SETTING

University veterinary teaching hospital.

ANIMALS

Eleven healthy Greyhounds.

INTERVENTIONS

Dogs were anesthetized and had 48 mL/kg of blood removed to induce hemorrhagic shock. Dogs received 20 mL/kg of HES 130/0.4 (n = 6) or 80 mL/kg of 0.9% sodium chloride (NaCl; n = 5) intravenously over 20 minutes. PCT was measured using the Platelet Function Analyzer-100 with collagen and adenosine-diphosphate cartridges at: T0 = 60 minutes after induction of anesthesia prior to hemorrhage, T1 = during hemorrhagic shock, and T2 = 40 minutes after completion of fluid bolus. Packed cell volume and platelet count were concurrently measured.

MEASUREMENT AND MAIN RESULTS

Hemorrhagic shock did not significantly change PCT, with no difference between T0 and T1. Both the HES 130/0.4 and 0.9% NaCl group had a significantly increased mean PCT at T2 of 91.4 seconds (95% CI 69.3-113.4) and 95.5 seconds (95% CI 78.2-112.8), respectively, compared to T1. The magnitude of change was significantly greater for the 0.9% NaCl group than the HES 130/0.4 group. There was no difference in the magnitude of change in PCV and platelet count between the 2 groups. The PCV and platelet count were >25% and >100,000/μL, respectively, in all dogs, except for dogs in the HES 130/0.4 group at T2 where platelet counts were <100,000/μL.

CONCLUSION

Controlled hemorrhagic shock in Greyhounds under anesthesia did not cause a significant change in PCT. Both HES 130/0.4 and 0.9% NaCl administration after induction of shock increased PCT. These results do not support that HES 130/0.4 causes relevant platelet dysfunction beyond hemodilution.

Comparison of the in vitro effects of saline, hypertonic hydroxyethyl starch, hypertonic saline, and two forms of hydroxyethyl starch on whole blood coagulation and platelet function in dogs

OBJECTIVE

To compare the in vitro effects of hypertonic solutions and colloids to saline on coagulation in dogs.

DESIGN

In vitro experimental study.

SETTING

Veterinary teaching hospital.

ANIMALS

Twenty-one adult dogs.

INTERVENTIONS

Blood samples were diluted with saline, 7.2% hypertonic saline solution with 6% hydroxyethylstarch with an average molecular weight of 200 kDa and a molar substitution of 0.4 (HH), 7.2% hypertonic saline (HTS), hydroxyethyl starch (HES) 130/0.4 or hydroxyethyl starch 600/0.75 at ratios of 1:22 and 1:9, and with saline and HES at a ratio of 1:3.

MEASUREMENTS AND MAIN RESULTS

Whole blood coagulation was analyzed using rotational thromboelastometry (extrinsic thromboelastometry-cloting time (ExTEM-CT), maximal clot firmness (MCF) and clot formation time (CFT) and fibrinogen function TEM-CT (FibTEM-CT) and MCF) and platelet function was analyzed using a platelet function analyzer (closure time, CTPFA ). All parameters measured were impaired by saline dilution. The CTPFA was prolonged by 7.2% hypertonic saline solution with 6% hydroxyethylstarch with an average molecular weight of 200 kDa and a molar substitution of 0.4 (HH) and HTS but not by HES solutions. At clinical dilutions equivalent to those generally administered for shock (saline 1:3, HES 1:9, and hypertonic solutions 1:22), CTPFA was more prolonged by HH and HTS than other solutions but more by saline than HES. No difference was found between the HES solutions or the hypertonic solutions. ExTEM-CFT and MCF were impaired by HH and HTS but only mildly by HES solutions. At clinically relevant dilutions, no difference was found in ExTEM-CFT between HTS and saline or in ExTEM-MCF between HH and saline. No consistent difference was found between the 2 HES solutions but HH impaired ExTEM-CFT and MCF more than HTS. At high dilutions, FibTEM-CT and -MCF and ExTEM-CT were impaired by HES.

CONCLUSIONS

Hypertonic solutions affect platelet function and whole blood coagulation to a greater extent than saline and HES. At clinically relevant dilutions, only CTPFA was markedly more affected by hypertonic solutions than by saline. At high dilutions, HES significantly affects coagulation but to no greater extent than saline at clinically relevant dilutions.

Comparison of whole blood and plasma colloid osmotic pressure in healthy cats

OBJECTIVE

To establish reference intervals for whole blood and plasma colloid osmotic pressure (COP) in healthy cats between the ages of 1 and 10 years using a cage-side colloid osmometer.

DESIGN

Prospective, observational study.

SETTINGS

University veterinary teaching hospital.

ANIMALS

Sixty-three healthy cats.

INTERVENTIONS

Phlebotomy.

MEASUREMENTS AND MAIN RESULTS

Whole blood COP mean was 24.4 (±2.78) mmHg and plasma COP mean was 24.3 (±2.59) mmHg. Reference interval for our study population of feline whole blood COP was 18.9 to 30.4 mmHg, and for our study population of feline plasma COP was 18.3 to 30.8 mmHg. Difference of paired whole blood COP and plasma COP was +0.23 ± 1.68 mmHg (P = 0.32). There was no significant difference when comparing COP from neutered male and neutered female cats. Total protein and albumin were significantly correlated with whole blood COP (total protein to whole blood COP P < 0.0001, r = 0.53; albumin to whole blood COP P <0.0001, r = 0.68) and plasma COP (total protein to plasma COP P = 0.0025, r = 0.41; albumin to plasma COP P < 0.0001, r = 0.66).

CONCLUSIONS

No significant difference was found between mean whole blood and plasma COP in this study population of cats. Even though not statistically significant, evaluation of paired whole blood COP and plasma COP did reveal a slight difference; therefore, it seems prudent to maintain sample consistency for serial evaluations in cats.

Hydroxyethyl starch: a review of pharmacokinetics, pharmacodynamics, current products, and potential clinical risks, benefits, and use

OBJECTIVE

To review and summarize the pharmacokinetics and pharmacodynamics of hydroxyethyl starch (HES), as well as reported risks and benefits of HES infusion, and to provide administration and monitoring recommendations for HES use in dogs and cats.

DATA SOURCES

Veterinary and human peer-reviewed medical literature, including scientific reviews, clinical and laboratory research articles, and authors' clinical experience.

SUMMARY

HES solutions are the most frequently used synthetic colloid plasma volume expanders in human and veterinary medicine. The majority of research in human medicine has focused on the adverse effects of HES infusion, with emphasis on acute kidney injury and coagulation derangements. The studies often differ in or fail to report factors, such as the type, amount, interval, and concentration of HES administered; the patient population studied; or concurrent fluids administered. Currently, there is no definitive clinical evidence that the reported adverse effects of HES use in human medicine occur in veterinary species. There is little information available on HES administration techniques or simultaneous administration of additional fluids in human and veterinary medicine. The rationale for HES use in small animals has been largely extrapolated from human medical studies and guidelines. A controlled approach to intravenous fluid resuscitation using crystalloid and HES volumes titrated to reach desired resuscitation end point parameters is outlined for small animal practitioners.

CONCLUSION

The extrapolation of data from human studies directly to small animals should be done with the knowledge that there may be species variations and different pharmacokinetics with different HES solutions. Veterinary reports indicate that bolus and continuous rate infusions of 6% hetastarch solutions at moderate doses are well tolerated in feline and canine subjects. Further research in domesticated species is necessary to better define and expand the knowledge regarding use of HES solutions in small animal medicine.

The effect of hetastarch 670/0.75 administered in vivo as a constant rate infusion on platelet closure time in the dog

OBJECTIVE

To evaluate the effects of hetastarch 670/0.75 on canine platelet function and clinical bleeding following its administration as a constant rate infusion (CRI) at 1 mL/kg/h and 2 mL/kg/h for 24 hours.

DESIGN

In vivo, prospective, open-label, crossover study.

SETTING

Research laboratory at a university veterinary facility.

ANIMALS

Eight healthy, adult male research dogs.

INTERVENTIONS

Each dog received 1 mL/kg/h hetastarch for 24 hours then 2 mL/kg/h with a washout period of 10 weeks between each experiment. Platelet closure time (CT) was measured using a platelet function analyzer with collagen adenosine diphosphate (ADP) cartridges. CT measurements were performed at baseline and 6, 12, and 24 hours following initiation of hetastarch infusion.

MEASUREMENTS AND MAIN RESULTS

At 1 mL/kg/h, mean CT was significantly increased at the 12- and 24-hour time point relative to the baseline value, although mean CT never rose to a value above the reference interval during the 24-hour infusion. At 2 mL/kg/h, median CT was also significantly increased at the 12- and 24-hour time point relative to the baseline value. Administration of 2 mL/kg/h did progressively prolong the median CT value though only exceeded the reference interval at the 24-hour time point. Despite the prolongation of median CT, there was no clinical evidence of spontaneous bleeding in any dog during the 24-hour infusion at either CRI rate.

CONCLUSIONS

Hetastarch 670/0.75 when used as a 24-hour CRI at 1 and 2 mL/kg/h prolongs CT in healthy dogs at 6, 12, and 24 hours. Median CT only exceeded the reference interval at 24 hours at 2 mL/kg/h.

In vitro evaluation of canine hemostasis following dilution with hydroxyethyl starch (130/0.4) via thromboelastometry

OBJECTIVE

To assess the effects of in vitro hemodilution of canine blood with a low molecular weight hy-droxyethyl starch (HES 130/0.4) by means of thromboelastometry (TEM).

DESIGN

In vitro experimental study.

SETTING

University Teaching Hospital.

ANIMALS

Ten healthy adult staff-owned dogs were sampled for the purposes of the study. Samples were also collected from 45 clinically normal dogs to establish thromboelastometric reference intervals.

INTERVENTIONS

For each dog whole blood was collected by jugular venipuncture and placed into tubes containing 3.8% trisodium citrate and stored at 37°C. Two standard dilutions (1:4 and 1:10) from canine blood specimens were prepared with HES 130/0.4 and saline 0.9%.

MEASUREMENTS AND MAIN RESULTS

The effects of dilution were studied by TEM. No statistically significant differences were observed between the TEM values of the control samples and the samples diluted with saline solution (ratio 1:10 and 1:4). In contrast, hypocoagulability was observed in the samples treated with HES 130/0.4, with more severe effects at 1:4 dilution than at 1:10 dilution. The 1:4 dilution with HES 130/0.4 produced marked alterations: CT (P = 0.035) and CFT (P = 0.0007) on the ex-TEM profile, CT (P = 0.0005) and ML (P = 0.0017) on the fib-TEM profile and CFT (P = 0.0043) on the in-TEM, were all significantly increased (P < 0.05), whereas MCF (P = 0.0042) and alpha angle (P = 0.002) on the in-TEM and MCF (P = 0.011) and alpha angle (P = 0.001) ex-TEM profiles and MCF (P = 0.0001) on the fib-TEM profile were significantly decreased (P < 0.05).

CONCLUSIONS

Dilution of canine blood with HES 130/0.4 results in a thromboelastometric pattern consistent with hypocoagulation and this effect appears to result from a dose-dependent alteration in fibrinogen concentration and inhibition of platelet function. As this is an in vitro study, further in vivo investigations are necessary to confirm the results.

In vitro effect of hydroxyethyl starch 130/0.42 on canine platelet function

OBJECTIVE

To evaluate the effect of 6% hydroxyethyl starch (HES) solution, with a molecular weight of 130 kDa and a degree of substitution of 0.42, on canine platelet function in vitro.

SAMPLES

Blood samples from 31 healthy adult dogs.

PROCEDURES

Citrated blood was diluted with saline (0.9% NaCl) solution or HES 130/0.42 in ratios of 1:9 (ie, 1 part saline solution or HES 130/0.42 and 9 parts blood) and 1:3. Platelet plug formation time (closure time [Ct]) was measured with a platelet function analyzer and cartridges coated with collagen and ADP.

RESULTS

Median baseline Ct with citrated blood was 84.0 seconds (interquartile range, 74.5 to 99.5 seconds). Results obtained with 1:9 dilutions with saline solution and HES 130/0.42 were not significantly different from baseline results. The 1:3 dilutions with saline solution and HES 130/0.42 resulted in median Cts of 96.0 seconds (interquartile range, 85.5 to 110.8 seconds) and 112.0 seconds (92.0 to 126.0 seconds), respectively. Results obtained with both 1:3 dilutions were significantly different from baseline results. The Ct obtained with the HES dilution was also significantly different from that of the 1:3 dilution with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Saline solution and HES 130/0.42 in a 1:3 dilution affected canine platelet function by prolonging Cts. The HES 130/0.42 had a significantly greater effect on canine platelets than did saline solution.

Acid-base and electrolyte balance following administration of three crystalloid solutions in dogs undergoing elective orthopaedic surgery

OBJECTIVE

To compare acid-base balance and incidence of hyperchloraemic metabolic acidosis following administration of three crystalloid solutions to dogs undergoing anaesthesia for orthopaedic surgery.

STUDY DESIGN

Prospective, randomised, clinical study.

ANIMALS

Sixty dogs.

METHODS

During a non-standardised anaesthetic, 0.9% saline (S), Hartmann's solution (H) or a polyionic glucose-free maintenance solution (M) was administered IV at 10 mL kg(-1)  hour(-1) . Venous blood pH, PCO2 , PCV, total protein, urea, sodium, potassium and chloride concentrations were measured at induction of anaesthesia (T0) and after 2 hours of fluid therapy (T2). Base excess (BE), bicarbonate, corrected chloride concentration (corrCl), osmolality, change in plasma volume (PV) and strong ion gap (SIG) were calculated. Changes in variables within groups (1-sample Student's t-test/Wilcoxon signed rank test) and between groups (1-way anova/Kruskal-Wallis) were assessed. Data are presented as median (interquartile range). Significance was set at p < 0.05.

RESULTS

No significant differences existed between groups for pH, PCO2 , PCV, total protein, urea, potassium, corrCl, PV and SIG. Potassium significantly increased in all groups. Significant differences existed between groups S and M for BE, sodium, chloride, bicarbonate and osmolality, and between groups H and M for sodium and osmolality. Chloride concentration significantly changed from 116 (114-117) to 117 (116-119) mmol L(-1) in group S, 116 (115-118) to 115 (113-117) mmol L(-1) in group H and 116 (115-118) to 114 (113-118)  mmol L(-1) in group M. In groups H and M, sodium and osmolality decreased, and BE and bicarbonate concentration increased significantly. Plasma volume increased by 28 (14-44)%, 25 (5-40)% and 24 (13-33)% in groups S, H and M, respectively.

CONCLUSION AND CLINICAL RELEVANCE

Hyperchloraemic metabolic acidosis did not develop after intraoperative 0.9% saline, Hartmann's solution or maintenance solution at 10 mL kg(-1)  hour(-1) for 2 hours in dogs undergoing elective orthopaedic surgery. Bicarbonate and BE increased after Hartmann's and maintenance solutions. Increases in potassium concentration were unexplained.