Role of arginine vasopressin in the setting of cardiopulmonary resuscitation

Second systolic peak in fetal middle cerebral artery Doppler after intrauterine transfusion

OBJECTIVE

To evaluate functional relationship between fetal circulatory response to intrauterine transfusion (IUT) as a circulatory challenge and appearance of second systolic peak (P2) in middle cerebral artery (MCA) based on hemodynamic principles.

METHODS

According to the concept of pulse wave (PW) propagation and reflection in adults, PWs arrive twice at cerebral circulation, as primary wave caused by left ventricle ejection and secondary after reflection in peripheral arteries. Thus adults show a biphasic contour of systolic blood flow in cerebral arteries. Similar waveforms may appear in fetal MCA-Doppler, as a response to IUT as a circulatory challenge. This is a proof-of-principle study, applying classical hemodynamic principles to fetal circulation. Accordingly, appearance of MCA-P2 may indicate vasoconstriction with increased PW reflection and timing of P2(Δt) should agree with the additional PW travel time down to reflection and return (Tr). To test this agreement, we searched our database for IUTs performed for severe fetal anemia, and compared Δt, obtained by Doppler, with Tr, obtained by hemodynamic calculation using human fetal data. Level of agreement was assessed using Bland-Altman-Plots.

RESULTS

We identified 21 fetuses with adequate Doppler quality for Δt evaluation. In four cases (19%) MCA-P2 was observed before the intervention, and in 17 interventions (81%) thereafter; a highly significant association between IUT and P2 appearance (p < 0.001). In these 17 interventions good agreement of P2 timing was found between Doppler assessment: Δt = 80 ± 8 ms, and hemodynamic calculation: Tr = 76 ± 4 ms.

CONCLUSION

P2 appearance in fetal MCA-Doppler seems to indicate PW reflection due to increased vasoconstriction after IUT. Thus hemodynamic considerations might enable Doppler monitoring of fetal vasoconstriction.

Comparison of Two Protocols for Pulseless Cardiopulmonary Arrest: Vasopressin Combined with Epinephrine Versus Epinephrine Alone

Introduction:

Survival from pulseless cardiac arrest typically is dismal. Some suggest that adding vasopressin to epinephrine as a cardiovascular stimulant can improve outcomes.

Problem:

This study compares survival outcomes using epinephrine verses vasopressin and epinephrine in persons with pulseless cardiac arrest.

Methods:

This is a retrospective, cohort evaluation of two resuscitative protocols (P1-epinephrine or P2-vasopressin with epinephrine) in a tiered response, community emergency medical service (EMS) with an approximately 100,000 catchment area. Cases are defined as 18 years or older determined to be in pulseless cardiac arrest. Outcomes were survival to emergency department arrival, to 24 hours, and to hospital discharge. Data were entered into Microsoft Office Excel® and processed using Analyze-it® for continuous and categorical data and Epi-Info® for odds ratios with confidence intervals.

Results:

There were 204 cases (60.3% males and 39.7% females) who met the inclusion criteria. Thirteen cases received electrical therapy only, and were dropped from analysis, leaving 191 (93.6%) who were included in the study; P1 to 85 (44.5%) and P2 to 106 (55.5%). Younger age was associated with improved survival to discharge home in both protocols, p = 0.003 (95% CI = 0.004–0.010). No difference in survival was noted at the levels of emergency department arrival OR 1.42 (95% CI = 0.73, 2.76) p = 0.26; 24 hour survival OR 0.54 (95% CI = 0.22–1.30) p = 0.133, or discharge home OR = 1.81 (95% CI = 0.49–6.88) p = 0.319.

Conclusions:

This study in a community EMS did not demonstrate improved survival with the addition of vasopressin to epinephrine for pulseless cardiac arrest.

Anesthesia advanced circulatory life support

PURPOSE

The constellation of advanced cardiac life support (ACLS) events, such as gas embolism, local anesthetic overdose, and spinal bradycardia, in the perioperative setting differs from events in the pre-hospital arena. As a result, modification of traditional ACLS protocols allows for more specific etiology-based resuscitation.

PRINCIPAL FINDINGS

Perioperative arrests are both uncommon and heterogeneous and have not been described or studied to the same extent as cardiac arrest in the community. These crises are usually witnessed, frequently anticipated, and involve a rescuer physician with knowledge of the patient's comorbidities and coexisting anesthetic or surgically related pathophysiology. When the health care provider identifies the probable cause of arrest, the practitioner has the ability to initiate medical management rapidly.

CONCLUSIONS

Recommendations for management must be predicated on expert opinion and physiological understanding rather than on the standards currently being used in the generation of ACLS protocols in the community. Adapting ACLS algorithms and considering the differential diagnoses of these perioperative events may prevent cardiac arrest.