Introduction
Recently an excellent post on the Trauma Professional's Blog pointed out that nocturnal vital signs disrupt sleep and may be unnecessary in stable patients (e.g. patients recovering from minor orthopedic surgery). I couldn't agree more. Allowing restorative sleep is one of the best approaches to prevention of delirium.
What about patients in the ICU? Critically ill patients certainly require monitoring, but are also at increased risk of delirium. How can we monitor patients safely without (literally) driving them crazy?
Sleep-protective vs. sleep-disruptive vital signs
In the ICU, we have the luxury of having patients attached to a variety of continuous monitors which can unobtrusively obtain information. Provided that the alarms are set appropriately, this allows for nondisruptive patient monitoring. For example, pulse oximetry and respiratory rate can easily be obtained in a sleeping patient, providing useful information about oxygenation and respiratory efforts.
The only two vital signs which often interfere with sleep are temperature and blood pressure monitoring. Avoiding temperature measurement when the patient is asleep is probably fine for most ICU patients (with the exception of patients with neurologic injury, in whom fever may be more problematic). What about blood pressure?
Nondisruptive hemodynamic monitoring
Blood pressure is certainly an important vital sign. However, it's not the only approach to hemodynamic monitoring. In particular, the presence of good urine output is reassuring evidence of adequate end-organ perfusion.
Above is one possible approach to sleep-protective hemodynamic monitoring. This may be considered in patients who are not at high risk for development of shock and don't have active cardiac problems (e.g., a patient admitted for COPD exacerbation). If efforts are made to obtain blood pressure and temperature measurements when the patient is awakened for other reasons (e.g. phlebotomy, repositioning), then this would probably result in a fair amount of blood pressure and temperature monitoring as well.
Patients in whom nocturnal stimulation is especially problematic
The risk of occult hemodynamic deterioration must be weighed against the risk of stimulating patients with vital sign monitoring. For example, patients who have already developed delirium are at greater risk of persistent or worsening delirium due to sleep deprivation. Patients with asthma or COPD exacerbation and a significant component of anxiety should be allowed uninterrupted sleep if at all possible, because arousal and anxiety may fuel their dyspnea in a vicious cycle (described previously here).
Greater focus on continuous monitoring may be useful
Current technologies allow for continuous monitoring of heart rate and respiratory rate using a single set of three EKG leads. Close attention to trends in continuously acquired information may detect instability earlier than intermittent vital sign monitoring. In particular, worsening tachypnea and tachycardia often precede overt clinical deterioration, so focusing on trends in these parameters may be especially useful (Cretikos 2008).
- Providing adequate sleep and maintaining normal circadian cycles are important to prevent and manage delirium in the ICU.
- The hemodynamic and respiratory status of ICU patients can often be assessed without interrupting sleep using respiratory rate, pulse oximetry, heart rate, urine output (if catheterized), and ventilator parameters (if intubated).
- In patients at low risk of hemodynamic decompensation, blood pressure monitoring may be suspended during sleep if there are other signs available for hemodynamic monitoring (e.g. heart rate and urine output). The ideal monitoring strategy may be determined on a patient-by-patient basis, weighing the risk of hemodynamic deterioration vs. the harm of sleep deprivation.
Image Credits: Monitor image from http://www.mc.vanderbilt.edu/documents/7north/files/MP5%20Rev_%20G%20Training%20Guide.pdf