Page 100 - JSOM Fall 2020

• The resuscitation of casualties suffering hemorrhagic group that RSI and PPV fall into the latter category; there is
shock should begin as soon as blood products and limited benefit from the PPV of hypoperfused lungs, even if
appropriately trained personnel are available. Ideally, this procedure delivers a greater percentage of oxygen. The
resuscitation should not be delayed for more than 30 PPV is likely to further decrease lung perfusion and increase
minutes from the time of injury. 8,9 V/Q mismatch. When considering the risk, the effect of PPV
• It should be noted that spontaneous respiration, induc- on CO may be disastrous for the patient in the low-flow state,
ing negative ITP, is beneficial to the shocked patient. often precipitating cardiac arrest.
Every effort should be made to retain this driver of
venous return and hence CO by using postural air- A global picture of the patient’s pathophysiology is needed.
way positioning, intubation without ventilation using The compensatory reserve and the proximity to physiological
short-acting neuromuscular blocking agents (NMBAs) exhaustion should be noted. The impact of any intervention
or surgical cricothyroidotomy. must also be carefully considered along with the potential for
iatrogenic harm. The failure to consider iatrogenesis can be
Keywords: rapid sequence induction (RSI); intermittent pos- termed “iatrogenic blindness” contributing to poor outcomes.
itive-pressure ventilation; positive-pressure respiration; If the practitioner is not blind to the potential harm then steps
hemorrhagic shock; iatrogenic disease can be taken to offset the impact of the intervention; for ex-
ample, in severe hemorrhagic shock, the patient may be resus-
citated with blood products to the point where RSI and PPV
may be tolerated.
Introduction
In the treatment of a patient with critical hemorrhagic shock, The rise of evidence-based medicine (EBM) has placed ever
a systematic approach is widely recommended. During the greater emphasis on the grade of evidence that exists for any
primary survey, an Airway - Breathing - Circulation - Disabil- treatment or procedure. Unfortunately, many a literature re-
ity - Environment (A-B-C-D-E)–based system or adaptions of view concludes with a lamentation of the paucity of available
this are most common. The airway is considered first, with the evidence or the poor quality of the studies with high risk of
gold standard of airway management being the placement of bias. Where evidence exists, it must be carefully appraised and
a cuffed tube in the trachea. This protects the airway from ob- considered. In the absence of high-quality evidence, we must
struction and aspiration. In the emergent setting the procedure use our current understanding of physiology and pathophys-
is RSI. To facilitate the passing of the tube through the glottis iology to further guide our understanding. The power of em-
the responsive patient needs to be both sedated and paralyzed pirical observation and clinical experience is well understood
with NMBAs. The drugs used to accomplish this vary between and one of the cornerstones of clinical judgment. The experi-
systems and practitioners. enced clinician’s dynamic assessment of patient care and the
effects of interventions, although not evidence based, are key
The second consideration is Breathing; as the patient is par- requirements of clinical practice. One approach is to produce
alyzed, they are required to be ventilated. This may be ac- a synthesis of physiology, evidence, experience, and knowl-
complished using a bag-valve mask (BVM) or a mechanical edge (PEEK) as a tool to aid clinical judgment (Figure 1).
ventilator. Both methods ventilate by positive pressure. The
decision to RSI and PPV carries benefits: the airway is pro- FIGURE 1 The PEEK clinical judgment tool.
tected and secured if a patient deteriorates, surgical grade
anesthesia is produced, ventilation can be controlled, and sup-
plemental oxygen can be delivered. For these reasons, RSI and
PPV have become a standard of care with critical patients in
many emergency medical systems. Unfortunately, RSI and PPV
also carry risk, of which the reduction in CO is the most harm-
ful in the shocked patient.

The decision to perform an intervention when indicated is
the process of critical clinical decision making and is a bal- (Original diagram by P. Thompson, 2019.)
ance between risk and benefit. An example of the challenge
in this case is reflected in the European guideline on manage-
ment of major bleeding and coagulopathy following trauma,
which states that RSI is “mandatory” in hemorrhagic shock;
however, the next sentence states “the introduction of positive Physiology
pressure (ventilation) can induce potentially life-threatening
hypotension in hypovolemic patients.” 10, 11 Central hypovolemia is a primary feature of hemorrhagic shock
and some other shocked states and is a feature of many disease
In situations where the procedure is highly likely to be helpful processes. In hemorrhagic shock, the loss of circulating blood
and has a low risk associated with the implementation, there volume reduces venous return with a subsequent reduction in
is good reason to be aggressive in the delivery of that proce- cardiac filling and thus end-diastolic volume (EDV). In accor-
dure. When the procedure is likely to be helpful, but the risk dance with Starling’s law of the heart, lower EDV translates
of clinical complications is higher, a more cautious approach is into a decrease in stroke volume and CO. Any further reduc-
required. Last, when the procedure is not sure to help and the tion in CO will correspond to a reduction in DO . If this re-
2
risk is high, a conservative approach is recommended. In the duction is beyond the capacity of the combined compensatory
patient with hemorrhagic shock, it is the position of the author reserve mechanisms then the oxygen consumption will become

98 | JSOM Volume 20, Edition 3 / Fall 2020