Electronic Medical Record Validation: Exploring the Reliability of Intracranial Pressure Data Abstracted From the Electronic Medical Record–Pilot

The Presence of Blood in a Strain Gauge Pressure Transducer Has a Clinical Effect on the Accuracy of Intracranial Pressure Readings

IMPORTANCE

Patients admitted with cerebral hemorrhage or cerebral edema often undergo external ventricular drain (EVD) placement to monitor and manage intracranial pressure (ICP). A strain gauge transducer accompanies the EVD to convert a pressure signal to an electrical waveform and assign a numeric value to the ICP.

OBJECTIVES

This study explored ICP accuracy in the presence of blood and other viscous fluid contaminates in the transducer.

DESIGN

Preclinical comparative design study.

SETTING

Laboratory setting using two Natus EVDs, two strain gauge transducers, and a sealed pressure chamber.

PARTICIPANTS

No human subjects or animal models were used.

INTERVENTIONS

A control transducer primed with saline was compared with an investigational transducer primed with blood or with saline/glycerol mixtures in mass:mass ratios of 25%, 50%, 75%, and 100% glycerol. Volume in a sealed chamber was manipulated to reflect changes in ICP to explore the impact of contaminates on pressure measurement.

MEASUREMENTS AND MAIN RESULTS

From 90 paired observations, ICP readings were statistically significantly different between the control (saline) and experimental (glycerol or blood) transducers. The time to a stable pressure reading was significantly different for saline vs. 25% glycerol (< 0.0005), 50% glycerol (< 0.005), 75% glycerol (< 0.0001), 100% glycerol (< 0.0005), and blood (< 0.0005). A difference in resting stable pressure was observed for saline vs. blood primed transducers (0.041).

CONCLUSIONS AND RELEVANCE

There are statistically significant and clinically relevant differences in time to a stable pressure reading when contaminates are introduced into a closed drainage system. Changing a transducer based on the presence of blood contaminate should be considered to improve accuracy but must be weighed against the risk of introducing infection.

Predictive Values for Time from Transducer Stopcock Closure to Accurate Intracranial Pressure Reading

BACKGROUND

When using an external ventricular drain (EVD) to monitor intracranial pressure (ICP), nurses need to know how long to wait after each manipulation of the transducer before the displayed ICP value represents an accurate signal. This study explores ICP signal equilibration time (EqT) under clinical conditions.

METHODS

This was a prospective ex vivo study using a simulated skull, standard EVD tubing, and a strain gauge transducer. All 270 trials simulating 90 combinations of different pressures and common clinical conditions were completed in August 2021. Each trial was recorded on video. Videos were scored using video editing software to obtain the exact start and stop time for each trial.

RESULTS

The mean EqT was 44.90 (18.77) seconds. One hundred fifty (55.56%) observations did not reach their expected value within 60 s. The longest mean EqTs were noted when blood was present in the EVD tubing (57.67 [8.91] seconds), when air bubbles were in the tubing (57.41 [8.73] seconds), and when EVD tubing was not flat (level) (50.77 [15.43] seconds). An omnibus test comparing mean EqT for conditions with no variables manipulated (30.08 [16.07] seconds) against mean EqT for all others (47.18 [18.13] seconds) found that mean EqTs were significantly different (P < 0.001).

CONCLUSIONS

Even when no additional variables were introduced, the mean EqTs were ~ 30 s. Common clinical variables increase the length of time before a transducer connected to an EVD will provide an accurate reading. Nurses should wait at least 30 s after turning the EVD stopcock before assuming ICP value reflects accurate ICP.

Intracranial Pressure Monitoring via External Ventricular Drain: Are We Waiting Long Enough Before Recording the Real Value?

BACKGROUND

External ventricular drain (EVD) is a standard approach for both monitoring intracranial pressure (ICP) and draining cerebrospinal fluid (CSF) for patients with subarachnoid hemorrhage. Documenting an accurate ICP value is important to assess the status of the brain, which would require the EVD system to be leveled properly and closed to CSF drainage for an adequate period. It is suggested that a minimum period of 5-minute EVD closure is needed before documenting a true ICP; however, there is no commonly agreed upon standard for documenting ICP. To obtain an insight into how well the intermittent EVD clamping procedure is performed for ICP documentation, we conducted a retrospective analysis of ICP recordings obtained through EVD from 107 patients with subarachnoid hemorrhage.

METHODS

The EVD was kept open for continuous CSF drainage and then intermittently closed for ICP documentation. For each EVD closure, mean ICP, standard deviation of ICP, duration of EVD closure, and time interval between 2 adjacent EVD closures were studied. The total number of EVD closures was calculated for each patient. We developed an algorithm to evaluate whether ICP reached a new equilibrium before the EVD was reopened to drainage. The percentage of EVD closures that reach the equilibrium was calculated.

RESULTS

The 107 patients had 32 755 EVD closures in total, among which 65.9% instances lasted less than 1 minute and only 16.3% of all the EVD closure episodes lasted longer than 5 minutes. The median duration of each EVD closure was 25 seconds (interquartile range, 10.2 seconds to 2.33 minutes). Only 22.9% of the EVD closures reached ICP equilibrium before EVD reopening.

CONCLUSION

A standard guideline and proper training are needed for bedside nurses, and a potential tool that can render ICP trend at a proper scale at bedside would help clinicians correctly document ICP.

Evidence-Based Management of External Ventricular Drains

PURPOSE OF REVIEW

The optimal management of external ventricular drains (EVD) in the setting of acute brain injury remains controversial. Therefore, we sought to determine whether there are optimal management approaches based on the current evidence.

RECENT FINDINGS

We identified 2 recent retrospective studies on the management of EVDs after subarachnoid hemorrhage (SAH) which showed conflicting results. A multicenter survey revealed discordance between existing evidence from randomized trials and actual practice. A prospective study in a post-traumatic brain injury (TBI) population demonstrated the benefit of EVDs but did not determine the optimal management of the EVD itself. The recent CLEAR trials have suggested that specific positioning of the EVD in the setting of intracerebral hemorrhage with intraventricular hemorrhage may be a promising approach to improve blood clearance. Evidence on the optimal management of EVDs remains limited. Additional multicenter prospective studies are critically needed to guide approaches to the management of the EVD.

A Novel Approach to Explore How Nursing Care Affects Intracranial Pressure

BACKGROUND

Intracranial pressure is measured continuously, and nursing behaviors have been associated with variations in the measurements.

METHODS

A prospective pilot observational study was done to develop a comprehensive list of nursing behaviors that affect patients' intracranial pressure. Data on nurses were obtained by self-reports and video recording. Patient-level data were collected via chart abstraction, video recording, and patients' monitors.

RESULTS

Data on 9 patients and 32 nurses were analyzed. A total of 6244 minutes of data were video recorded. Intracranial pressure was changed because of a nursing intervention during 3394 observations. Compared with baseline levels, intracranial pressure was significantly higher if a nursing intervention was performed (odds ratio, 1.96; 95% CI, 1.71-2.24; P < .001).

CONCLUSION

Studying nursing behaviors is feasible. Synchronizing and analyzing mutually exclusive and exhaustive behaviors indicated that nursing behaviors have an effect on patients' intracranial pressure.