OBJECTIVE To evaluate the use of a modified passive leg-raising maneuver (PLRM) to predict fluid responsiveness during experimental induction and correction of hypovolemia in isoflurane-anesthetized pigs.
ANIMALS 6 healthy male Landrace pigs.
PROCEDURES Pigs were anesthetized with isoflurane, positioned in dorsal recumbency, and instrumented. Following induction of a neuromuscular blockade, pigs were mechanically ventilated throughout 5 sequential experimental stages during which the blood volume was manipulated so that subjects transitioned from normovolemia (baseline) to hypovolemia (blood volume depletion, 20% and 40%), back to normovolemia, and then to hypervolemia. During each stage, hemodynamic variables were measured before and 3 minutes after a PLRM and 1 minute after the pelvic limbs were returned to their original position. The PLRM consisted of raising the pelvic limbs and caudal portion of the abdomen to a 15° angle relative to the horizontal plane.
RESULTS Hemodynamic variables did not vary in response to the PLRM when pigs were normovolemic or hypervolemic. When pigs were hypovolemic, the PLRM resulted in a significant increase in cardiac output and decrease in plethysomographic variability index and pulse pressure variation. When the pelvic limbs were returned to their original position, cardiac output and pulse pressure variation rapidly returned to their pre-PLRM values, but the plethysomographic variability index did not.
CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a modified PLRM might be useful for identification of hemodynamically unstable animals that are likely to respond to fluid therapy. Further research is necessary to validate the described PLRM for prediction of fluid responsiveness in clinically ill animals.
To evaluate cardiac output (CO) measurements using transpulmonary ultrasound (TPUD) technology and compare results with those of the gold standard, pulmonary arterial catheter thermodilution (PACTD), in 6 healthy anesthetized pigs during acute hemodynamic changes caused by manipulation of the blood volume.
6 healthy male Landrace pigs.
Over a period of 1 week, pigs were anesthetized with isoflurane, mechanically ventilated, and underwent instrumentation in dorsal recumbency. They were subjected to sequential experimental states during which the blood volume was manipulated so that the animals transitioned from normovolemia to hypovolemia (20% and 40% of blood volume depletion), back to normovolemia (autologous blood transfusion), and then to hypervolemia (following colloid bolus). During each volume state, CO measurements were compared between TPUD and PACTD.
The mean ± SD relative bias between TPUD and PACTD was 7.71% ± 21.2% with limits of agreement –33.9% to 49.3%, indicating TPUD slightly underestimated CO values, compared with values obtained with PACTD. The mean ± SD of the bias between the 2 methods was 0.13 ± 0.5 L/min. Only 5 of 36 (13.9%) TPUD CO measurements had an absolute value of relative bias > 30%. The percentage error calculated for TPUD was 29.4%.
Results suggested that TPUD measurements have acceptable agreement with PACTD measurements. Moreover, TPUD exhibits promising potential in being used interchangeably with PACTD for future hemodynamic research involving swine as species of interest.
Evaluate agreement between 2 non-invasive blood pressure (NIBP) techniques and invasive arterial blood pressure (IBP) in anesthetized bats using various cuff sizes and cuff positioning while also evaluating its performance during hypertension and hypotension.
8 bats (1.1 ± 0.2 kg).
Bats were anesthetized with isoflurane in oxygen. NIBP was measured using oscillometric (NIBP-O) and Doppler (NIBP-D) techniques in the pectoral limb (PEC) and pelvic limbs (PEL) using 3 cuff sizes (1, 2, and 3). NIBP measurements were compared with IBP; systolic (SAPinvasive), mean (MAPinvasive), and diastolic arterial blood pressure (DAPinvasive) during normotension, hypertension, and hypotension. Hypotension was induced with isoflurane (3.8 ± 1.2%) and hypertension with norepinephrine (3 ± 0.5 µg/kg/min). Data analysis included Bland-Altman analyses and 3-way ANOVA. Results were reported as mean bias (95% CI).
NIBP-O monitor reported 29% errors, and experienced more failures with hypertension, cuff placement on PEC, and using a size 1 cuff. Across states, an agreement between NIBP-D and MAPinvasive with cuff 2 on PEL (−3 mmHg [−8, 1]), and NIBP-D and SAPinvasive with cuff 3 on PEC (2 mmHg [−5, 9 mmHg]) was achieved. NIBP-D over-estimated SAPinvasive and MAPinvasive during hypertension in both limbs with cuffs 1 and 2. Except during hypotension, NIBP-O underestimated MAPinvasive and DAPinvasive using a size 2 cuff on PEL.
In anesthetized bats, NIBP-O is unreliable for estimating IBP. NIBP-D shows acceptable agreement with MAPinvasive with cuff size 2 on PEL, and with SAPinvasive with cuff size 3 on PEC across a wide range of IBP values.
To investigate the relationship between invasively measured stroke volume (SV) and (1) esophageal Doppler-derived indices such as stroke distance (StrokeD), flow time corrected (FTc), stroke distance variation (SDV), and peak velocity variation (PVV); and (2) arterial load (AL) variables during evaluation of fluid responsiveness (FR) in anesthetized dogs undergoing sudden hemodynamic shifts in blood volume.
6 healthy male dogs.
Dogs were anesthetized with isoflurane, ventilated mechanically, and instrumented to undergo sequential, nonrandomized experimental stages. The dogs transitioned from normovolemia (NORMO-BL) to hypovolemia (30% blood loss; HYPO-30), followed by autologous blood transfusion, and then to hypervolemia (colloid bolus). During each stage, SV was quantified using pulmonary artery thermodilution and its relationship with StrokeD, FTc, SDV, and PVV; and AL variables such as effective arterial elastance (Ea), dynamic arterial elastance (Eadyn), and total arterial compliance (Ca) were established.
As SV decreased significantly during HYPO-30 compared to NORMO-BL, there was a significant (P < .001) decrease in StrokeD, FTc, and Ca, with simultaneous increases in SDV, PVV, Ea, and Eadyn. Upon restoration of blood volume, these values stabilized closer to NORMO-BL. A significant (P < .001) correlation was observed between SV and StrokeD, FTc, Ea, Eadyn, and Ca.
Minimally invasive StrokeD, FTc, SDV, and PVV act as SV surrogates and help assess FR during different blood volume stages in healthy dogs. During hypovolemia-induced hypotension, Ea, Eadyn, and Ca may be able to guide therapeutic decisions favoring improvement in blood pressure and SV.
To compare cardiac output (CO) measurements by transesophageal echocardiography (TEECO) and esophageal Doppler monitor (EDMCO) with pulmonary artery thermodilution (PATDCO) in anesthetized dogs subjected to pharmacological interventions. The effect of treatments on EDM-derived indexes was also investigated.
6 healthy male dogs (10.8 ± 0.7 kg).
Dogs were anesthetized with propofol and isoflurane, mechanically ventilated, and monitored with invasive mean arterial pressure (MAP), end-tidal isoflurane concentration (ETISO), PATDCO, TEECO, EDMCO, and EDM-derived indexes. Four treatments were administered to all dogs by randomization. Baseline data were collected before each treatment: (1) dobutamine infusion; (2) esmolol infusion; (3) phenylephrine infusion; and (4) ETISO > 3%. Data were collected after 10-minute stabilization and after 30 minutes of washout between treatments. Statistical tests were pairwise t test, Bland-Altman analysis, Lin's concordance correlation (ρc), and polar plot analysis with P < .05 set as significance.
The mean ± SD relative bias (limits of agreement) for TEECO was 0.35 ± 25.2% (−49.1% to 49.8%) and for EDMCO was −27.2 ± 22.5% (−71.4% to 17%) versus PATDCO. The percent error for TEECO and EDMCO was 27.6% and 44.1%, respectively. The ρc value was 0.82 for TEECO and 0.66 for EDMCO. TEECO and EDMCO showed good trending ability. EDM-derived indexes displayed significant changes specific to the drug administered (P < .001).
For minimally invasive CO monitoring, TEE may provide more favorable performance than EDM in clinical settings; however, EDM-derived indexes yield valuable hemodynamic information that reliably follows trends in CO, thus supporting critical decision-making in canine patients.