Arteriovenous differences in PCO2 and cardiac output during CPR in the dog

Serial paired arterial and jugular venous point-of-care values in dogs undergoing manual basic life support

OBJECTIVE

To evaluate differences in point-of-care (POC) variables obtained from arterial and jugular venous blood in dogs undergoing manual basic life support (BLS) and report changes over time.

DESIGN

Experimental study.

SETTING

Small animal research facility.

ANIMALS

Twenty-four purpose-bred research dogs.

INTERVENTIONS

Dogs were anesthetized, and arterial catheters were placed before euthanasia. One minute after cardiopulmonary arrest, BLS consisting of manual chest compressions and ventilation delivered via endotracheal intubation, face mask, mouth-to-nose, or no ventilation was initiated. Paired arterial and jugular venous blood samples were obtained for POC testing before euthanasia (T0), at 3 minutes (T3), and at 6 minutes (T6) into BLS.

MEASUREMENTS AND MAIN RESULTS

The association of POC variables with arterial or venous sample type while controlling for type of ventilation and sampling timepoint was determined using a generalized linear mixed model. Variables obtained from arterial and venous blood samples were compared over time using repeated measures ANOVA or Friedman test. Pao2, anion gap, potassium, chloride, glucose concentration, and PCV were significantly higher in arterial blood samples compared with venous samples (P < 0.03). By T6, arterial glucose concentration, arterial and venous base excess, venous pH, and plasma lactate, potassium, creatinine, bicarbonate, and sodium concentrations were significantly increased, and arterial and venous Po2, ionized calcium concentration, PCV, and total plasma protein concentration were significantly decreased from T0 (P < 0.05).

CONCLUSIONS

Although statistically significant, arteriovenous differences and changes in POC blood variables during BLS were small and not clinically relevant over time. Given the challenges of arterial blood sampling, it may be reasonable to pursue venous blood sampling during CPR. Further studies in dogs undergoing BLS and advanced life support are needed to better understand the potential clinical role of POC testing during CPR.

The association of intraosseous vascular access and survival among pediatric patients with out-of-hospital cardiac arrest

INTRODUCTION

In pediatric out-of-hospital cardiac arrest (OHCA) the effect of intraosseous (IO) or intravenous (IV) access on outcomes is unclear.

METHODS

We analyzed prospectively collected data of non-traumatic OHCA in the Resuscitation Outcomes Consortium registry from 2011 to 2015. We included EMS-treated patients ≤17 years of age, classified patients based on vascular access routes, and calculated success rates of IO and IV attempts. After excluding patients with obvious non-cardiac etiologies and those with unsuccessful vascular access or multiple routes, we fit a logistic regression model to evaluate the association of IO vascular access (reference IV access) with the primary outcome of survival, using multiple imputation to address missing data. We analyzed a subgroup of patients at least 2 years of age.

RESULTS

There were 1549 non-traumatic OHCA: 895 (57.8%) patients had an IO line attempted with 822 (91.8%) successful; 488 (31.5%) had an IV line attempted with 345 (70.7%) successful (difference 21%, 95% CI 17 to 26%). Of the 761 patients included in our logistic regression, 601 received IO (30 [5.2%] survived) and 160 received IV (40 [25%] survived) vascular access. Intraosseous access was associated with a decreased probability of survival (adjusted OR 0.46; 95% CI 0.21-0.98). Patients at least 2 years of age showed a similar association (adjusted OR 0.36; CI 0.15-0.86).

CONCLUSIONS

Intraosseous access was associated with decreased survival among pediatric non-traumatic OHCA. These results are exploratory and support the need for further study to evaluate the effect of intravascular access method on outcomes.

Effects of humeral intraosseous epinephrine in a pediatric hypovolemic cardiac arrest porcine model

Background

Aims of the study were to determine the effects of humerus intraosseous (HIO) versus intravenous (IV) administration of epinephrine in a hypovolemic, pediatric pig model. We compared concentration maximum (Cmax), time to maximum concentration (Tmax), mean concentration (MC) over time and return of spontaneous circulation (ROSC).

Methods

Pediatric pig were randomly assigned to each group (HIO (n=7); IV (n=7); cardiopulmonary resuscitation (CPR)+defibrillation (defib) (n=7) and CPR-only group (n=5)). The pig were anesthetized; 35% of the blood volume was exsanguinated. pigs were in arrest for 2 min, and then CPR was performed for 2 min. Epinephrine 0.01 mg/kg was administered 4 min postarrest by either route. Samples were collected over 5 min. After sample collection, epinephrine was administered every 4 min or until ROSC. The Cmax and MC were analyzed using high-performance liquid chromatography. Defibrillation began at 3 min postarrest and administered every 2 min or until ROSC or endpoint at 20 min after initiation of CPR.

Results

Analysis indicated that the Cmax was significantly higher in the IV versus HIO group (p=0.001). Tmax was shorter in the IV group but was not significantly different (p=0.789). The MC was significantly greater in the IV versus HIO groups at 90 and 120 s (p<0.05). The IV versus HIO had a significantly higher MC (p=0.001). χ² indicated the IV group (5 out of 7) had significantly higher rate of ROSC than the HIO group (1 out of 7) (p=0.031). One subject in the CPR+defib and no subjects in the CPR-only groups achieved ROSC.

Discussion

Based on the results of our study, the IV route is more effective than the HIO route.

Assessing Acid–Base Status in Circulatory Failure: Relationship Between Arterial and Peripheral Venous Blood Gas Measurements in Hypovolemic Shock

Background and Objectives:

In severe circulatory failure agreement between arterial and mixed venous or central venous values is poor; venous values are more reflective of tissue acid–base imbalance. No prior study has examined the relationship between peripheral venous blood gas (VBG) values and arterial blood gas (ABG) values in hemodynamic compromise. The objective of this study was to examine the correlation between hemodynamic parameters, specifically systolic blood pressure (SBP) and the arterial–peripheral venous (A-PV) difference for all commonly used acid–base parameters (pH, Pco 2, and bicarbonate).

Design, Setting, Participants, and Measurements:

Data were obtained prospectively from adult patients with trauma. When an ABG was obtained for clinical purposes, a VBG was drawn as soon as possible. Patients were excluded if the ABG and VBG were drawn >10 minutes apart.

Results:

The correlations between A-PV pH, A-PV Pco 2, and A-PV bicarbonate and SBP were not statistically significant ( P = .55, .17, and .09, respectively). Although patients with hypotension had a lower mean arterial and peripheral venous pH and bicarbonate compared to hemodynamically stable patients, mean A-PV differences for pH and Pco 2 were not statistically different ( P = .24 and .16, respectively) between hypotensive and normotensive groups.

Conclusions:

In hypovolemic shock, the peripheral VBG does not demonstrate a higher CO2 concentration and lower pH compared to arterial blood. Therefore, the peripheral VBG is not a surrogate for the tissue acid–base status in hypovolemic shock, likely due to peripheral vasoconstriction and central shunting of blood to essential organs. This contrasts with the selective venous respiratory acidosis previously demonstrated in central venous and mixed venous measurements in circulatory failure, which is more reflective of acid–base imbalance at the tissue level than arterial blood. Further work needs to be done to better define the relationship between ABG and both central and peripheral VBG values in various types of shock.

Correlation of Venous and Arterial Blood Gas Values Following Cardiothoracic Surgery in Infants and Children

The authors retrospectively compared the correlation of pH and pCO2 from venous and arterial blood gases following cardiothoracic surgery in neonates, infants, and children. The cohort for the study included 14 infants and children undergoing cardiovascular surgery procedures for correction of congenital heart disease. The patients ranged in age from neonates to 48 months (6.2 ± 12.3 months) and in weight from 2.9 to 16.1 kg (5.0 ± 3.2 kg). A total of 95 simultaneous samples of arterial and venous blood were obtained for blood gas analysis. The mean venous pCO2 value was 45 ± 9 mmHg, with a mean arterial pCO2 value of 37 ± 7.4 mmHg. The overall difference between the venous and arterial CO2 values was 8 ± 4 mmHg. The venous to arterial CO2 gradient was greater than 5 mmHg in 78 of 95 samples. There was a significantly greater discrepancy between the arterial and venous pCO2 values when the central venous oxygen saturation was less than 70% compared to when the central venous saturation was ≥70% (p < 0.01). Linear regression analysis of venous versus arterial pCO2 revealed a slope of 0.62, r = 0.76, and r2 = 0.58. The mean venous pH value was 7.42 ± 0.07 and the mean arterial pH value was 7.46 ± 0.07. The overall difference between the venous and arterial pH values was 0.04 ± 0.02. Chi-squared analysis showed that with a central venous oxygen saturation of ≥70%, there were a significantly greater number of values with a venous to arterial pH difference of 0.05 or less compared to samples with a central venous oxygen saturation of less than 70% (p = 0.002). Linear regression analysis of venous versus arterial pH revealed a slope of 0.84, r = 0.88, and r2 = 0.77. Venous blood gas values do not provide a clinically useful estimate of arterial blood gas values following cardiothoracic surgery in children.

Central venous-arterial carbon dioxide difference as an indicator of cardiac index

OBJECTIVE

The mixed venous-arterial (v-a) pCO(2) difference has been shown to be inversely correlated with the cardiac index (CI). A central venous pCO(2), which is easier to obtain, may provide similar information. The purpose of this study was to examine the correlation between the central venous-arterial pCO(2) difference and CI.

DESIGN

Prospective, cohort study.

SETTING

Intensive care unit of an urban tertiary care hospital.

PATIENTS AND PARTICIPANTS

Eighty-three consecutive intensive care unit patients.

MEASUREMENTS

Simultaneous blood gases from the arterial, pulmonary artery (PA), and central venous (CV) catheters were obtained. At the same time point, cardiac indices were measured by the thermodilution technique (an average of three measurements). The cardiac indices obtained by the venous-arterial differences were compared with those determined by thermodilution.

RESULTS

The correlation (R(2)) between the mixed venous-arterial pCO(2) difference and cardiac index was 0.903 (p <0.0001), and the correlation between the central venous-arterial pCO(2) difference and cardiac index was 0.892 (p <0.0001). The regression equations for these relationships were natural log (CI)=1.837-0.159 (v-a) CO(2) for the PA and natural log (CI)=1.787-0.151 (v-a) CO(2) for the CV (p <0.0001 for both). The root-mean-squared error for the PA and CV regression equations were 0.095 and 0.101, respectively.

CONCLUSION

Venous-arterial pCO(2) differences obtained from both the PA and CV circulations inversely correlate with the cardiac index. Substitution of a central for a mixed venous-arterial pCO(2) difference provides an accurate alternative method for calculation of cardiac output.

Effect of intra-aortic occlusion balloon in external thoracic compressions during CPR in pigs

This study was performed to compare the effectiveness of external thoracic compressions with and without intra-aortic occlusion balloon with capnography and coronary and cerebral perfusion pressure (CPP) in the normothermic and traumatic-less cardiopulmonary arrest provoked by a ventricular fibrillation in pigs. This was an experimental study (cross-over study) in 14 pigs with similar characteristics (23 +/- 2 kg, 10-12 weeks of age). After an 8-minute nonintervention period, the cardiopulmonary resuscitation (CPR) consists of 4 periods of 5 minutes alternating CPR with and without intra-aortic occlusion balloon. Main outcomes measured are end-tidal CO(2) (ETCO(2)); intra-aortic, coronary, and cerebral perfusion pressures; blood gas analysis; and blood lactate concentration. At the end of each period, levels are obtained. Postmortem study was made. Inflation of the occlusion balloon provokes an expansion in the ETCO(2) of about 38%. The coronary perfusion pressure initially goes from 10.21 to 29.0 mm Hg after the occlusion of the aorta, which means an increase of 150%. The CPP goes from 12.54 to 39.71 mm Hg after the balloon was inflated, which means an increase of 200%. In all cases the differences are statistically significant (P <.0001). These increases are less important in the final periods. Intra-aortic balloon occlusion increased ETCO(2), coronary, and cerebral perfusion pressures. An early application of this technique was important.