Vasopressin for cardiac arrest: meta-analysis of randomized controlled trials

BACKGROUND

Prior meta-analyses-reported results of randomised controlled trials (RCTs) published between 1997 and 2004 failed to show any vasopressin-related benefit in cardiac arrest. Based on new RCT-data and a hypothesis of a potentially increased vasoconstricting efficacy of vasopressin, we sought to determine whether the cumulative, current evidence supports or refutes an overall and/or selective benefit for vasopressin regarding sustained restoration of spontaneous circulation (ROSC), long-term survival, and neurological outcome.

METHODS

Two reviewers independently searched PubMed, EMBASE, and Cochrane Database for RCTs assigning adults with cardiac arrest to treatment with a vasopressin-containing regimen (vasopressin-group) vs adrenaline (epinephrine) alone (control-group) and reporting on long-term outcomes. Data from 4475 patients in 6 high-methodological quality RCTs were analyzed. Subgroup analyses were conducted according to initial cardiac rhythm and time from collapse to drug administration (T(DRUG))<20 min.

RESULTS

Vasopressin vs. control did not improve overall rates of sustained ROSC, long-term survival, or favourable neurological outcome. However, in asystole, vasopressin vs. control was associated with higher long-term survival {odds ratio (OR)=1.80, 95% confidence interval (CI)=1.04-3.12, P=0.04}. In asystolic patients of RCTs with average T(DRUG)<20 min, vasopressin vs. control increased the rates of sustained ROSC (data available from 2 RCTs; OR=1.70, 95% CI=1.17-2.47, P=0.005) and long-term survival (data available from 3 RCTs; OR=2.84, 95% CI=1.19-6.79, P=0.02).

CONCLUSIONS

Vasopressin use in the resuscitation of cardiac arrest patients is not associated with any overall benefit or harm. However, vasopressin may improve the long-term survival of asystolic patients, especially when average T(DRUG) is <20 min.

Comparison of high-frequency oscillation and tracheal gas insufflation versus standard high-frequency oscillation at two levels of tracheal pressure

PURPOSE

In acute respiratory distress syndrome (ARDS), combined high-frequency oscillation (HFO) and tracheal gas insufflation (TGI) may improve oxygenation through a TGI-induced increase in mean tracheal pressure (P(tr)). We compared standard HFO and HFO-TGI matched for P(tr), in order to determine whether TGI affects gas exchange independently from P (tr).

METHODS

We conducted a prospective, randomized, crossover, physiological study in a 37-bed intensive care unit. Twenty-two patients with early acute lung injury (ALI) or ARDS were enrolled. On day 1, patients were ventilated with HFO, without (60 min) and combined with TGI (60 min) in random order. HFO/HFO-TGI sessions were repeated in inverse order within 7 h. HFO/HFO-TGI mean airway pressure (P(aw)) was titrated to a P(tr) that was either equal to (low P(aw)) or 3 cmH(2)O higher than (high P(aw)) the P(tr) of the preceding conventional mechanical ventilation. On day 2, the protocol was repeated at the alternative P(tr) level relative to day 1.

RESULTS

Gas exchange and hemodynamics were determined before, during, and after HFO/HFO-TGI sessions. HFO-TGI-high P(aw) versus HFO-high P(aw) resulted in significantly higher PaO(2)/inspired O(2) fraction (FiO(2)) [mean +/- standard error of the mean (SEM): 281.6 +/- 15.1 versus 199.0 +/- 15.0 mmHg; mean increase: 42%; P < 0.001]. HFO-TGI-low P(aw), versus HFO-low P(aw), resulted in significantly higher PaO(2)/FiO(2) (222.8 +/- 14.6 versus 141.3 +/- 8.7 mmHg; mean increase: 58%; P < 0.001). PaCO(2) was significantly lower during HFO-TGI-high P(aw) versus HFO-high P(aw) (45.3 +/- 1.6 versus 53.7 +/- 1.9 mmHg; mean decrease: 16%; P = 0.037).

CONCLUSIONS

At the same P(tr) level, HFO-TGI results in superior gas exchange compared with HFO.

Acute effects of combined high-frequency oscillation and tracheal gas insufflation in severe acute respiratory distress syndrome

OBJECTIVE

In acute respiratory distress syndrome (ARDS), high-frequency oscillation (HFO) improves oxygenation relative to conventional mechanical ventilation (CMV). Alveolar ventilation is improved by adding tracheal gas insufflation (TGI) to CMV. We hypothesized that combined HFO and TGI (HFO-TGI) might result in improved gas exchange relative to both standard HFO and CMV according to the ARDS Network protocol.

DESIGN

Prospective, randomized, crossover study.

SETTING

A 30-bed university intensive care unit.

PATIENTS

A total of 14 patients with early (<72 hrs in duration), severe (PaO2/FiO2 of <150 mm Hg and prerecruitment oxygenation index of 22.8 +/- 1.9 [mean +/- SEM]), primary ARDS.

INTERVENTIONS

Patients were ventilated with HFO without (60 mins) and combined with TGI (6.1 +/- 0.1 L/min, 60 mins) in random order. HFO sessions were repeated in inverse order within 24 hrs. HFO sessions were preceded and followed by ARDS Network CMV. Four recruitment maneuvers were performed during the study period. During HFO sessions, mean airway pressure was set at 1 cm H2O above the point of maximal curvature of the respiratory system expiratory pressure-volume curve.

MEASUREMENTS AND MAIN RESULTS

Gas exchange and hemodynamics were determined before, during, and after HFO sessions. HFO-TGI improved PaO2/FiO2 relative to HFO and CMV (174.5 +/- 10.4 vs. 136.0 +/- 10.0 and 105.0 +/- 3.7 mm Hg, respectively, p < .05 for both) and oxygenation index relative to HFO (17.1 +/- 1.3 vs. 22.3 +/- 1.7, respectively p < .05). PaO2/FiO2 returned to baseline within 3 hrs after HFO. During HFO-TGI, shunt fraction and mixed venous oxygen saturation improved relative to CMV (0.36 +/- 0.01 vs. 0.45 +/- 0.01 and 77.8% +/- 1.2% vs. 71.8% +/- 1.3%, respectively, p < .05 for both). PaCO2 and hemodynamics were unaffected by HFO sessions. Respiratory mechanics remained unchanged throughout the study period.

CONCLUSIONS

In early onset, primary, severe ARDS, short-term HFO-TGI improves oxygenation relative to standard HFO and ARDS Network CMV.

End-inspiratory occlusion maneuver during transesophageal echocardiography for patent foramen ovale detection in intensive care unit patients

OBJECTIVE

Mechanically ventilated patients in the intensive care unit cannot cooperate to perform the Valsalva maneuver during echocardiography for detection of patent foramen ovale. We evaluated the effectiveness of the end-inspiratory occlusion maneuver to enhance detection of patent foramen ovale in this patient population.

DESIGN

Prospective interventional study.

SETTING

The 40-bed intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

Twenty five sedated and mechanically ventilated intensive care unit patients referred by their attending physician for bedside transesophageal echocardiography and agitated saline contrast study for detection of patent foramen ovale.

INTERVENTION

Agitated saline contrast study with end-inspiratory occlusion maneuver.

MEASUREMENTS AND RESULTS

All patients underwent a complete transesophageal echocardiographic study without any complications. Reduction in right atrial cross-sectional area (from 15.80 +/- 6.08 cm2 to 12.40 +/- 4.63 cm2; p < 0.001) and interatrial septum deviation during the maneuver were recorded in all patients. Microbubbles imaged in the left atrium within three cardiac cycles after injection of agitated saline diagnosed patent foramen ovale in three patients. When end-inspiratory occlusion maneuver was added, patent foramen ovale was diagnosed in seven patients (McNemar chi2 = 9.33, p = 0.0023).

CONCLUSIONS

The end-inspiratory occlusion maneuver enhances the sensitivity of transesophageal echocardiography with agitated saline contrast study for diagnosing intermittent patent foramen ovale in critically ill mechanically ventilated patients.