Remember, our patients in critical condition may often deteriorate following intubation. Ever wondered why? It’s usually because they’re not adequately resuscitated before the procedure. This tends to happen predominantly with patients needing emergency intubations, as these individuals are often in precarious hemodynamic states and might be volume depleted.
Let’s dive a little deeper into the physiology. Ordinarily, our respiratory process operates under negative pressure – when the diaphragm descends, it lessens intrathoracic pressure and draws air into the lungs. Intubation switches this to a positive pressure system where air is forcibly delivered into the lungs by a ventilator. In patients with low intravascular volume, this increase in intrathoracic pressure may precipitate hemodynamic instability. This situation is further exacerbated by sedatives and paralysis, which hinder the body’s ability to adapt to these sudden changes.
It’s essential to note, though, that this deterioration is seldom abrupt and can often be anticipated.
Whenever possible, which is the majority of cases, always aim to resuscitate before intubation. But be aware, indiscriminate fluid administration is not the answer. A timely bedside echo can ascertain their volume status and assess their right ventricular condition – key information before intubation. Also, remember to use the Shock Index, calculated as heart rate/SBP. A value ≥ 0.9 may indicate the need for further resuscitation.
Emergency intubation, a common Pre-Hospital, ER and ICU procedure, although aimed at supporting the patient, brings about substantial changes to normal cardiopulmonary physiology. This could be detrimental for critically ill patients, unless the necessary precautions are taken during the peri-intubation period.
During positive pressure ventilation, normal cardiopulmonary interactions are disturbed due to the increase in intrathoracic pressure, leading to decreased preload and increased RV afterload.
Patients in need of emergent intubation often come with compromised hemodynamics, maintained mainly by increased sympathetic activity and elevated endogenous catecholamine levels. In addition, their illness often leads to hypovolemia due to decreased intake and increased losses. Sedatives used during rapid sequence intubation can further compromise the sympathetic response.
Failure to address hypovolemia and reduced sympathetic activity can lead to post-intubation hypotension and, in severe cases, cardiac arrest. Hence, thorough planning and preparation are more crucial than the intubation itself. Secure resuscitative access before intubation, preferably using two US-guided 18G IVs. Then, consider using point-of-care echo, especially in patients with SBP < 90 or a Shock Index > 0.9.
These patients may benefit from volume resuscitation using pressure-bagged fluids and low-dose vasopressors to raise BP. Push-dose epinephrine can be useful in situations where adequate pre-intubation resuscitation is not possible, or the sympathetic drive is so high that removing it may cause severe decompensation.
The mantra remains – “Resuscitate before you intubate.”