Article of the Week


We will be posting commentaries on articles relating to internal medicine and endocrinology that we think are of interest.


Oct 26th, 2022

Comparison of biochemical and hematologic values obtained via jugular venipuncture and peripheral intravenous catheters in dogs


In humans, collection of blood samples from PIVC rather than direct venipuncture (DV) is recommended for patients who are pediatric, have difficult vascular access, have coagulopathies, or need repeat testing. Using PIVC sampling limits patient discomfort, decreases needle injuries, and decreases ecchymoses compared to DV.5,6 Human studies evaluating SB and CBC found no clinically important or statistically significant differences between collection methods for most or all analytes, though some studies found clinically important or statistically significant differences for bicarbonate (HCO3), potassium (K), or glucose (GLU).


Clinical confidence in PIVC blood sampling for SB and CBC might reduce the need for DV in dogs. DV commonly requires physical restraint of the dog and utilizes 2 or more people, whereas collecting blood from a PIVC may require minimal restraint and a single individual. In dogs with cardiovascular compromise, respiratory distress, coagulopathies, small size, or fractious behavior, DV could be difficult, time-consuming, or dangerous for the dog and staff. Obtaining blood from PIVC rather than DV could help improve staff efficiency as well as the dog's safety and comfort.5


The primary objectives of this study were to determine whether sampling from fPIVC (freshly placed) or hPIVC (hospitalized) approximately 1 day after placement can reliably be used for SB and CBC testing. The hypothesis was that SB and CBC results from fPIVC and hPIVC would be clinically equivalent to those from DV.


Background: Sampling from a peripheral intravenous catheter (PIVC) might be a more efficient and less traumatic collection of blood for serum biochemistry (SB) or CBC than direct venipuncture (DV). Agreement between results of samples obtained by these methods has not been evaluated in dogs.


Blood collection from hPIVC; All IV fluids and medications administered via the hPIVC were discontinued for 5 minutes before sampling. The t-set clamp was adjusted to be as close as possible to the t-set hub. After a 1 mL waste sample of blood was removed and discarded, blood for SB and CBC was collected as described above for fPIVC except that a 20-gauge needle was attached to the syringe(s) and inserted into the injection port. Waste sample volume was determined by using saline to measure dead space from a 20-gauge, 1.25 inch catheter and attached t-set hub. This volume (0.23 mL) was multiplied by 300% and rounded up to obtain a waste volume of 1 mL.


Objectives: The primary objectives were to determine whether sampling from PIVC could be used in place of DV for dogs. We hypothesized DV and PIVC samples would have clinically equivalent SB and CBC results.


Animals: Sixty-one client-owned dogs were included in each study arm.


Methods: This was a partially randomized method-comparison study. Paired DV and PIVC samples obtained within 1 to 2 minutes after, or approximately 24 hours after, placement of a PIVC in a cephalic vein were evaluated for agreement and bias using percentage difference plots (with a priori application of consensus total allowable error), Bland-Altman analysis, Passing-Bablok regression analysis, Wilcoxon signed rank test, and McNemar's test.


Results: There was statistically and clinically acceptable agreement and no bias between sampling methods for the majority of results. Analytes with the most frequent disagreement were aspartate aminotransferase, total bilirubin, potassium, bicarbonate, and leukocyte differential counts, as well as red blood cell count, hemoglobin, hematocrit, and packed cell volume in the hospitalized PIVC sampling group. Few observed differences would change clinical decision making.


Conclusions and Clinical Importance: PIVC sampling can provide generally acceptable SB and CBC results for most dogs, but clinicians should be aware of a few values for which disparate results might occasionally be obtained.