The key functions in emergency and critical care management of the shock patient are appropriate airway management and hemodynamic support.
[6-24-2017 Rapid sequence intubation can precipitate hypotension. Be sure to have your pulse dose pressor prepared and ready to go for any intubation as you never know. To view Dr. Weingart’s pdf click on mixing instructions for epinephrine and phenylephrine. To find more resources on push dose/pulse dose pressors type in “pulse dose pressors” into the search box.]
However, these procedures are often associated with pre- or postintubation hypotension which is a serious problem. “Post-intubation hypotension (PIH) occurs in one quarter of normotensive patients undergoing emergency intubation and is severe (SBP < 70 mm Hg) in up to 10% of cases.” (1)
“Preintubation shock increases the likelihood of severe complications, including cardiac arrest, during or following intubation. Intubation and mechanical ventilation can have substantial negative impact on fragile cardiovascular status. Medications and positive pressure ventilation may reduce cardiovascular performance and precipitate irreversible decompensation. Cardiac arrest rates as high as 15% are described during airway management of patients in hypotensive shock. If the patient is adequately oxygenated [meaning you aren’t “forced to act”] fluid and catecholamine support is advised before initiating the intubation sequence.” (2).
For patients in shock, bag mask ventilation may be needed between induction and intubation if the oxygen saturation falls below 90% or if there is severe acidemia (pH < 7.1).
In critically ill patients monitoring oxygen saturation with the forehead reflectance probe is preferred over the finger probe because it is more reliable during hypotension. “Limited detection of cutaneous arterial pulsatility generally reduces accuracy of pulse oximetry with SBP < 80 mm Hg.”
Rapid Sequence Induction (RSI) (4)
“Pretreatment opioids are contraindicated in patients with comrpomised cardiovascular status including compensated shock.”
The agents indicated for RSI in uncompensated shock (hypotension) and in compensated shock are etomide and ketamine. “. . . both etomidate and ketamine require dose adjustments for adminstration to shocked patients (e.g., etomidate 0.1 to 0.15 mg per kg or ketamine 0.5 to 0.75 mg per kg). It is better to err on the side of too little rather than too much. Airway managers should anticipate delay in drug onset resulting from dose adjustment and the prolonged circulation time. Neuromuscular blocking agents pose little hemodynamic risk and should be dosed normally.”
“In patients with identified difficult airway attributes, awake intubation using a flexible endoscope, facilitated by topical anesthesia and limited (or no) sedation addresses the difficult airway and also avoids the potential hypotension of induction agents.”
Remember, that at the first thought that you might need to do an awake intubation, you need to give glycopyrrolate 0.01 mg IV (usual adult dose, 0.4 to 0.8 mg IV) for mucosal drying. It takes ten minutes to work and twenty minutes is better according to the Airway Manual.
“Progressive bradycardia not associated with hypoxia or laryngoscopy is a frequent sign of terminal shock and impending cardiac arrest.”
Postintubation Management (5)
Positive pressure ventilation (PPV) limits venous return in hypovolemic patients. And auto-PEEP from retained intra-thoracic volume can develop from positive pressure ventilation and, if not recognized, can lead to irreversible hypotension and cardiac arrest.
The key to limiting the negative effects of PPV is to use a slow respiratory rate and low tidal volume (10 to 12 breaths per minute and a tidal volume of 7 ml per kg).
“Vasopressor support should be immediately available to reverse life-threatening hypotension. Preintubation hypotension is more easily managed with catecholamine infusion initiated before intubation.”
The Intubation Bundle for Patients With Shock (6)
A multi-center study of an “intubation bundle”, a set of procedures, in patient being intubated in the ICU showed a reduction in severe hypoxia and hypotension.
It is very important to recognize that this protocol is not completely appropriate for ED shock patients.
The etomidate or ketamine dose used for induction in this protocol are inappropriate and are much higher than the doses recommended in the Airway Manual cited above. Also the Airway Manual as noted above recommends catecholamine infusion be begun before intubation in hypotensive patients. “Preintubation hypotension is more easily managed with with catecholamine infusion initiated before intubation.” (5)
Intubation care bundle management
1. Presence of two operators
2. Fluid loading (isotonic saline 500 ml or starch 250 ml) in absence of cardiogenic pulmonary edema
3. Preparation of long-term sedation
4. Preoxygenation for 3 min with NIPPV in case of acute respiratory failure (FiO2 100%, pressure support ventilation level between 5 and 15 cm H2O to obtain an expiratory tidal volume between 6 and 8 ml/kg and PEEP of 5 cm H2O)
5. Rapid sequence induction: etomidate 0.2–0.3 mg/kg or ketamine 1.5–3 mg/kg [Note: these doses of etomidate and ketamine are much higher than those recommend in the Airway Manual for patients with compensated or uncompensated shock—see above] combined with succinylcholine 1–1.5 mg/kg in absence of allergy, hyperkalemia, severe acidosis, acute or chronic neuromuscular disease, burn patient
for more than 48 h and medullar trauma
6. Sellick maneuver
7. Immediate conﬁrmation of tube placement by capnography
8. Norepinephrine if diastolic blood pressure remains < 35 mmHg
9. Initiate long-term sedation
10. Initial ‘‘protective ventilation’’: tidal volume 6–8 ml/kg of ideal body weight, PEEP < 5 cmH2O and respiratory rate between 10 and 20 cycles/min, FiO2 100% for a plateau pressure < 30 cmH2O
NIPPV non-invasive positive pressure ventilation, PEEP positive end expiratory pressure, FiO2 inspired oxygen fraction
(1) Manual of Emergency Airway Management 4th ed, 2012. RM Walls and MF Murphy, p. 388.
(2) Ibid., p. 385.
(3) Ibid., p. 386.
(4) Ibid., pp. 386 + 387.
(5) Ibid., pp. 387 + 389.
(6) An Intervention to Decrease Complications Related to Endotracheal Intubation in the Intesive Care Unit: A Prospective, Multiple-center Study. S Jaber et al. Intensive Care Med. 2010;36(2):248-255.
Available at http://crashingpatient.com/wp-content/pdf/et%20interventions.pdf.