Can the use of different types of mechanical ventilatory modes cause peripheral vasoconstriction?
During the cares of a patient on BIPAP ASB it was noted that the patients fingers were both cold on both hands, and mottled on the left hand. After changing the ventilatory mode to CPAP ASB, both hands and fingers warmed up, and return of normal colour appeared.
But on returning the patient back to BIPAP ASB, after an hour the patients fingers became cold again!
Has anyone got any specific reasoning as to why, if any, the reason for the peripheral vasoconstriction due to different modes of mechanical ventilation, be it increased Peak Pressures etc?
One must refer to "cardiopulmonary" interactions....Peripheral vasoconstriction with mechanical ventilation is a sympathetic response to "LCOS" state with increasing Transthoracic pressure without actual "hypotension"
Adding a low dose alpha blocker may help the patient if lactate levels are also high
Without knowing more about the patient history, or assessment, I am going to a take a tentative stab at it.
With normal ventilation the intra-thoracic pressure (inhalation/exhalation close to 0 i.e. ranges about -5 to +2 cmH20) therefore there is no resistance for blood return to the heart. Whenever you expose a person to positive pressure ventilation, be it intubated and mechanically ventilated or even the positive pressure of BIPAP, it creates a positive pressure in the thoracic cavity (roughly whatever the BIPAP is set at so if its 10 and 5, the intra-thoracic pressure ranges from +5 to +15), which impacts the preload of the heart. Now there is resistance for blood return. A strong heart, with a good hemodynamic status easily compensates for this change in preload by increasing the rate. BUT on the edge of hemodynamic stability, if increasing the heart rate is not enough, the body tries to increase preload by vasoconstriction. which is why you might see the physical evidence of vasoconstriction. This would have been nice to have tested by a small fluid bolus, if that was something appropriate for that patient.
The other possible cause or co-cause would be something like Raynaud's disease, which is a disorder affecting the blood vessels. When the patient is either exposed to cold or stress (like the stress of needed BIPAP or the hemodynamic stress of BIPAP - who knows) this results acute vasoconstriction especially in the hands and feet. Again, worth reviewing the patient history to see if there is evidence of, or a family history of Raynaud's.
Could it be as simple as carpal pedal spasms from excessive ventilation? Too low Co2 will cause a similar symptom.
Check Co2 levels.
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