Mechanical Ventilation in Neurocritical Patients

Patients under neurocritical care may require mechanical ventilation for airway protection; respiratory failure can occur simultaneously or be acquired during the ICU stay. In this chapter, we will address the ventilatory strategies, in particular the role of protective lung ventilation, and the potential increase in intracranial pressure as a result of permissive hypercapnia, high airway pressures during recruitment maneuvers, and/or prone position. We will also describe some strategies to achieve mechanical ventilation liberation, including evaluation for tracheostomy, timing of tracheostomy, mechanical ventilation modalities for weaning and extubation, or tracheostomy weaning for mechanical ventilation.

Carbon dioxide levels in neonates: what are safe parameters?

There is no consensus on the optimal pCO2 levels in the newborn. We reviewed the effects of hypercapnia and hypocapnia and existing carbon dioxide thresholds in neonates. A systematic review was conducted in accordance with the PRISMA statement and MOOSE guidelines. Two hundred and ninety-nine studies were screened and 37 studies included. Covidence online software was employed to streamline relevant articles. Hypocapnia was associated with predominantly neurological side effects while hypercapnia was linked with neurological, respiratory and gastrointestinal outcomes and Retinpathy of prematurity (ROP). Permissive hypercapnia did not decrease periventricular leukomalacia (PVL), ROP, hydrocephalus or air leaks. As safe pCO2 ranges were not explicitly concluded in the studies chosen, it was indirectly extrapolated with reference to pCO2 levels that were found to increase the risk of neonatal disease. Although PaCO2 ranges were reported from 2.6 to 8.7 kPa (19.5–64.3 mmHg) in both term and preterm infants, there are little data on the safety of these ranges. For permissive hypercapnia, parameters described for bronchopulmonary dysplasia (BPD; PaCO2 6.0–7.3 kPa: 45.0–54.8 mmHg) and congenital diaphragmatic hernia (CDH; PaCO2 ≤ 8.7 kPa: ≤65.3 mmHg) were identified. Contradictory findings on the effectiveness of permissive hypercapnia highlight the need for further data on appropriate CO2 parameters and correlation with outcomes. Impact There is no consensus on the optimal pCO2 levels in the newborn. There is no consensus on the effectiveness of permissive hypercapnia in neonates. A safe range of pCO2 of 5–7 kPa was inferred following systematic review.

Severe hypocalcemia and seizures after normalization of pCO2 in a patient with severe bronchopulmonary dysplasia and permissive hypercapnia

Objectives To describe the association between the rapid normalization of pCO2 after intubation in a patient with severe bronchopulmonary dysplasia managed with permissive hypercapnia, with the risk of developing hypocalcemia and seizures, and to make health care providers aware of this risk in similar cases. Case presentation An extreme premature infant, born at 25 weeks of gestational age (GA), developed a severe bronchopulmonary dysplasia (BPD) and, after several extubation failures could be managed with non-invasive ventilation and permissive hypercapnia, with capillary pCO2 of up to 80 mmHg and pH >7.20. At 46 postmenstrual age (PMA) he was intubated because of severe hypercapnia and compensating metabolic alkalosis. About 20 h after intubation, after normalization of pH and pCO2, he developed hypocalcemia and seizures, that remitted after iCa normalization. A comparison between arterial and capillary blood gases showed a significantly greater correlation between pH and iCa in arterial than in capillary samples. Conclusions Our findings emphasize the importance of avoiding the abrupt reduction of pCO2 and the close monitoring of acute metabolic changes after its correction in chronic patients with permissive hypercapnia, as well as the potential superiority of arterial samples over capillaries to improve the precision of this control.

Effects of Permissive Hypercapnia on Laparoscopic Surgery for Rectal Carcinoma

Background. Permissive hypercapnia has been recommended during the treatment of chronic diseases; however, there are insufficient clinical data to investigate the feasibility of permissive hypercapnia in relatively long-term surgeries such as laparoscopic surgery for rectal carcinoma. This prospective study is aimed at investigating the efficacy and safety of permissive hypercapnia under different CO2 pneumoperitoneum pressures during the laparoscopic surgery for rectal carcinoma. Methods. A total of 90 patients undergoing laparoscopic surgery for rectal carcinoma were recruited from July 2016 to March 2017. They were randomly assigned to high hypercapnia group (n=30), low hypercapnia group (n=30), or control group (n=30), whose PaCO2 levels were maintained at 56-65 mmHg, 46-55 mmHg, or 35-45 mmHg, respectively. The primary endpoint was peak pressure. Plateau pressure, dynamic compliance, arterial blood analysis, and hemodynamic measures were collected as secondary outcomes. Adverse events were monitored. Results. High hypercapnia group were reported to be associated with significantly lower peak pressure and plateau pressure, but higher dynamic compliance compared to low hypercapnia and control group (all P<0.01). Moreover, patients in the high hypercapnia group had higher postoperation oxygenation index values compared to those in the low hypercapnia and control group (all P<0.01). There is no significant difference in the pH, Spo2, MAP, heart rate, and adverse events among the three groups. Conclusion. Permissive hypercapnia with a PaCO2 level of 56-65 mmHg was able to improve respiratory function after laparoscopic surgery in rectal cancer patients.

Hypercapnic-hypoxic respiratory training as a method of post-conditioning in stroke suvivors

The paper summarizes data on the use of respiratory training under hypoxia, features of permissive hypercapnia, and the potential mechanisms of neuroprotective effect in the combined use of hypoxia and hypercapnia. The paper provides information about the practical application of this training in various diseases. The technical aspects, the possibility of using individual respiratory simulators, the optimal parameters of exposure and the composition of the gas are discussed. Considering the expected effectiveness we assume that this type of respiratory training can be used in the routine medical rehabilitation practice post-stroke survivors.