Pathophysiology and clinical consequences of arterial blood gases and pH after cardiac arrest

Abstract

Post cardiac arrest syndrome is associated with high morbidity and mortality, which is related not only to a poor neurological outcome but also to respiratory and cardiovascular dysfunctions. The control of gas exchange, and in particular oxygenation and carbon dioxide levels, is fundamental in mechanically ventilated patients after resuscitation, as arterial blood gases derangement might have important effects on the cerebral blood flow and systemic physiology.In particular, the pathophysiological role of carbon dioxide (CO2) levels is strongly underestimated, as its alterations quickly affect also the changes of intracellular pH, and consequently influence metabolic energy and oxygen demand. Hypo/hypercapnia, as well as mechanical ventilation during and after resuscitation, can affect CO2 levels and trigger a dangerous pathophysiological vicious circle related to the relationship between pH, cellular demand, and catecholamine levels. The developing hypocapnia can nullify the beneficial effects of the hypothermia. The aim of this review was to describe the pathophysiology and clinical consequences of arterial blood gases and pH after cardiac arrest.According to our findings, the optimal ventilator strategies in post cardiac arrest patients are not fully understood, and oxygen and carbon dioxide targets should take in consideration a complex pattern of pathophysiological factors. Further studies are warranted to define the optimal settings of mechanical ventilation in patients after cardiac arrest.

Ventilatory settings in the initial 72 h and their association with outcome in out-of-hospital cardiac arrest patients: a preplanned secondary analysis of the targeted hypothermia versus targeted normothermia after out-of-hospital cardiac arrest (TTM2) trial

“…The characterization of ventilator settings is fundamental in this group of patients, as mortality and poor outcome are still very high despite several medical interventions have been applied and implemented [2,[17][18][19][20][21][22][23][24]. The recent guidelines of the European Resuscitation Council and European Society of Intensive Care Medicine on post-resuscitation care do not provide specific recommendations on the optimal ventilator settings to be applied after cardiac arrest.…”

“…Post cardiac arrest syndrome is characterized by high mortality and morbidity rates, and several strategies have been implemented with the aim to improve survival and neurological outcome [1]. Among these, research has focused on the optimization of respiratory function and the prevention of pulmonary complications, which are common in this population [1,2].…”

“…Mechanical ventilation has the aim to provide appropriate gas exchange (arterial partial pressure of oxygen, PaO 2 and arterial partial pressure of carbon dioxide, PaCO 2 ), which can have important effects on the development of secondary brain damage, cerebral blood flow, and cerebrovascular dynamics, and patient's survival rate [2]. The pathophysiology of cardiac arrest and its systemic effects, as well as the relationship between ventilatory settings and cerebral hemodynamics after resuscitation is complex and not completely elucidated [2]. The literature on the acute respiratory distress syndrome (ARDS) [3] and non-ARDS [4] population has highlighted the importance of the use of lung protective strategies (i.e.…”

Dynamic changes in arterial blood gas during cardiopulmonary resuscitation in out-of-hospital cardiac arrest

“…Otherwise, by minimizing confounders and following the guideline, all patients in the current study were intubated and ventilated with 100% oxygen, and were provided high-quality CPR as was possible after arrival at the ED. It seems appropriate to maintain 100% oxygen supply during CPR, despite the fact that high fraction of inspired oxygen (FiO 2 ) may increase oxidative stress and release of reactive oxygen species, which result in molecular damages and a higher risk of mortality, especially post-ROSC 1 , 20 – 22 . Results are conflicting in terms of specific oxygen regimens that can increase the chance of survival.…”

“…Cardiac arrest results in various complications in the human body, including changes in acid–base status and blood gas, such as metabolic acidosis, hypoxia, and hypercarbia 1 . Arterial blood gas analysis (ABGA), as one of the intra-cardiopulmonary resuscitation (CPR) parameters, may provide useful diagnostic and prognostic clues in patients with out-of-hospital cardiac arrest (OHCA) 2 .…”