Health & Medical intensive care

Severe Cardiovascular Collapse After ET Intubation in the ICU

Severe Cardiovascular Collapse After ET Intubation in the ICU

Discussion


This large cohort analysis showed that CVC was a frequent complication of intubation in the ICU. Patient age, SAPS II score regardless of age, intubation for acute respiratory failure, initial intubation in the ICU and FiO 2 >70 % after intubation, but not COPD, were found to be independent risk factors for CVC. Moreover, CVC was associated with a significantly higher 28-day mortality rate.

The CVC rate observed in our study cohort was similar to those reported previously, especially in patients without preexisting hypotension before intubation (29 % of 84 patients), or if 15 % were receiving vasopressor before intubation (33 % of 794 patients). The CVC rate may be dependent on the definition of CVC, particularly the level and duration of hypotension. Based on previous studies, we arbitrarily defined CVC as an arterial systolic blood pressure ≤65 mmHg recorded at least once and/or ≤90 mmHg lasting ≥30 minutes despite vascular loading with 500–1000 mL of crystalloid and/or colloid solutions and/or necessitating introduction of vasoactive drugs. Mortality in the ICU was not related to hypotension after intubation, regardless of its definition and severity.

The three models used in our multivariate analyses were built to propose an approach to risk factors for CVC. The first model included patient characteristics, the second model included details of intubation procedures, and the third model included both sets of factors.

Elevated SAPS II score, a good surrogate for illness severity and well correlated with patient mortality, was found to be a risk factor for CVC. Early intubation within the first 24 hours of ICU admission was associated with a high SAPS II score. We did not include age as a component of the SAPS II score to avoid colinearity in the multivariate analyses. A first intubation in ICU was another risk factor. It could follow an uncontrolled evolution of the reason of ICU admission (acute respiratory failure, for example), possibly after NIV failure. In contrast, subsequent intubations may follow extubation failure following the correct treatment of initial shock and multiorgan failure.

Acute respiratory failure has been identified as a risk factor for CVC and for complications related to intubation. Desaturation time during apnea associated with intubation may be reduced in ICU patients, especially in hypoxemic patients. Patients with acute respiratory failure have limitations in oxygen transport, alveolar volume and enhanced shunt fraction. Hemoglobin desaturation has been found to increase mortality rates in this population. Preoxygenation with NIV and elevated postintubation FiO 2 (>70 %) reflect the severity of respiratory failure.

Although fluid challenge before intubation was not significantly associated with CVC in univariate analysis, it was included in multivariate analysis. Its inclusion was justified by the results of a before/after study comparing the implementation of different treatments and procedures during the intubation procedure. Fluid challenge may be a marker of preload dependence or hemodynamic status and may correspond to a prior severe hemodynamic condition characterized by a potential hypovolemic status before induction. These results are complicated by differences in fluid challenge among the ICUs surveyed. Fluid challenge before intubation is systematic in some ICUs, according to the aforementioned bundle, but is administered only to patients with hypovolemia in other ICUs.

Etomidate and ketamine are anesthetic drugs that have a rapid onset and short half-life, are well tolerated hemodynamically and improve intubation conditions. Increased induction with etomidate or ketamine in the ICU from 35 % to 76 % was associated with a significant reduction in the incidence of severe hypotension. In this observational study, etomidate and ketamine were associated with CVC in univariate analysis but not in multivariate analysis. The lack of correlation between the incidence of CVC and administration of these drugs suggests that etomidate and ketamine were chosen for the most severely ill patients because of their hemodynamic safety profiles.

A previous study showed that implementation of an intubation management protocol reduced the incidence of intubation-related ICU complications, in particular CVC (15 % versus 27 %). This protocol included fluid challenge before intubation, preoxygenation with NIV, rapid sequence induction (with ketamine or etomidate, and suxamethonium) and early administration of sedation and vasopressors if needed. Our univariate analysis showed that early administration of sedation was significantly associated with CVC. Its nonsignificance on multivariate analysis suggests that it was probably a confounding factor due to patient severity.

Comatose patients who required ETI were less likely to develop CVC during intubation. Indeed, most comatose patients experience failure of only one organ. Furthermore, laryngoscopy and intubation after rapid sequence induction in these patients often results in hypertension, as most patients intubated after rapid sequence induction show a sympathetic response to laryngeal stimulation, characterized by tachycardia and increases in mean arterial pressure and intracranial pressure.

The study had several limitations. First, it was not designed to identify factors protective against CVC. Indeed, patients with hemodynamic instability before ETI were not included in this analysis. The addition of such patients may modify the interpretation of these analyses; however, the rate of life-threatening complications after ETI in patients with septic shock before ETI (about 36 %) was similar to the rate reported in nonselected critically ill patients. These patients must be evaluated in future studies. Several of the factors found to be significant in univariate analysis were not included in the multivariate models, for statistical or clinical reasons. For example, PEEP level was not clinically relevant (5.7 versus 6.0 cmH 2 O). Another limitation was our inability to evaluate the correlation between the doses of drugs used for ETI (ketamine, etomidate, thiopental and/or propofol) with the degree of hypotension. The specific association between drugs used to facilitate intubation and severe CVC requires further study. COPD and hypercarbic status have been regarded as independently associated with life-threatening hypotension after intubation, with elevated CO 2 levels causing generalized vasodilatation. Another limitation is that the presence of an arterial catheter for invasive blood pressure measurement was not fulfilled. It could be a prerequisite and a very important safety measure. Hypercarbia causes sympathetic stimulation, increasing cardiac output secondary to tachycardia. Unfortunately, this study was not designed to record levels of CO 2 before and after intubation; only the presence of end-tidal CO 2 curve was noted. Thus, we could not determine the role of CO 2 variations on CVC occurrence.

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