Implementation and evaluation of a nurse-centered computerized potassium regulation protocol in the intensive care unit - a before and after analysis
- Miriam Hoekstra†1, 2Email author,
- Mathijs Vogelzang†2,
- José T Drost3,
- Marcel Janse3,
- Bert G Loef3,
- Iwan CC van der Horst2,
- Felix Zijlstra2 and
- Maarten WN Nijsten3
© Hoekstra et al; licensee BioMed Central Ltd. 2010
Received: 8 June 2009
Accepted: 25 January 2010
Published: 25 January 2010
Potassium disorders can cause major complications and must be avoided in critically ill patients. Regulation of potassium in the intensive care unit (ICU) requires potassium administration with frequent blood potassium measurements and subsequent adjustments of the amount of potassium administrated. The use of a potassium replacement protocol can improve potassium regulation. For safety and efficiency, computerized protocols appear to be superior over paper protocols. The aim of this study was to evaluate if a computerized potassium regulation protocol in the ICU improved potassium regulation.
In our surgical ICU (12 beds) and cardiothoracic ICU (14 beds) at a tertiary academic center, we implemented a nurse-centered computerized potassium protocol integrated with the pre-existent glucose control program called GRIP (Glucose Regulation in Intensive Care patients). Before implementation of the computerized protocol, potassium replacement was physician-driven. Potassium was delivered continuously either by central venous catheter or by gastric, duodenal or jejunal tube. After every potassium measurement, nurses received a recommendation for the potassium administration rate and the time to the next measurement. In this before-after study we evaluated potassium regulation with GRIP. The attitude of the nursing staff towards potassium regulation with computer support was measured with questionnaires.
The patient cohort consisted of 775 patients before and 1435 after the implementation of computerized potassium control. The number of patients with hypokalemia (<3.5 mmol/L) and hyperkalemia (>5.0 mmol/L) were recorded, as well as the time course of potassium levels after ICU admission. The incidence of hypokalemia and hyperkalemia was calculated. Median potassium-levels were similar in both study periods, but the level of potassium control improved: the incidence of hypokalemia decreased from 2.4% to 1.7% (P < 0.001) and hyperkalemia from 7.4% to 4.8% (P < 0.001). Nurses indicated that they considered computerized potassium control an improvement over previous practice.
Computerized potassium control, integrated with the nurse-centered GRIP program for glucose regulation, is effective and reduces the prevalence of hypo- and hyperkalemia in the ICU compared with physician-driven potassium regulation.
Hypokalemia and hyperkalemia are both associated with an increased risk of complications that can be potentially fatal [1, 2]. Therefore, derangements of blood potassium levels should be avoided in critically ill patients or, when present, rapidly corrected [3–5]. In the intensive care unit (ICU) potassium is administrated continuously by syringe pump, either enterally or parenterally [6–9]. Keeping potassium levels within the normal range (3.5-5.0 mmol/L) requires frequent blood potassium measurements and subsequent adjustments of potassium intake. Although potassium disorders occur frequently in the critical care setting and regulation is considered important, there are only a few studies addressing this subject. Some ICU's use an (nurse-driven) electrolyte replacement protocol [10–12]. However even with this form of standardization, such errors still occur which are an important issue in healthcare systems. For both safety and efficiency, computerized protocols are assumed to be superior over paper protocols [13–19]. In our ICU a nurse-centered computer-assisted glucose regulation program called GRIP (Glucose Regulation in Intensive care Patients) was already fully operational for several years [20, 21]. We hypothesized that integration of advice on potassium replacement into this system (GRIP-II) would improve potassium control with no extra or reduced effort of the nurses and physicians. Potassium and glucose regulation share the properties that they both can be measured in a single blood sample on one machine, that both can be delivered by syringe pump, and that both need multiple adjustments per day. Before the implementation of GRIP-II, potassium replacement in our ICU was physician-driven. In this before-after study we describe the extension of GRIP with a potassium intake recommendation algorithm.
The before and after study was performed from May 2005 through December 2006 at 2 closed-format, adult ICUs in a 1300 bed tertiary university teaching hospital: a 12-bed surgical ICU and a 14-bed thoracic-surgical ICU. We evaluated potassium regulation with a computerized potassium regulation algorithm that was added to the GRIP program for glucose regulation [20, 21]. The primary endpoint was potassium regulation in terms of out of range measurements and speed of correction. The secondary endpoint was endorsement and ease of use by the nurses. At our institution, before implementation of nurse-based computerized potassium regulation, potassium replacement was physician-driven. The physician protocol called for extra potassium infusion when hypokalemia was present. When hyperkalemia developed the potassium administration was stopped. For all patients the physicians explicitly decided each day in the morning what amount of potassium had to be given and entered this amount in the prescription record. Moreover, physicians were frequently consulted by nurses during evening and nights about potassium changes for 30% of the patients. The precise way of executing these guidelines was left to the discretion of the attending physician. This study was approved by the institutional medical ethics review board (METc 2006.185) and informed consent was waived.
Implementation of a computerized potassium regulation protocol (GRIP-II)
Parameters in GRIP and GRIP-II
From the hospital information system
From the nurse
Parameters requested for glucose control.
- Last glucose measurement
- Nurse identification
- Enteral feeding
- Stomach retention
- Intravenous glucose dose
- Current insulin pump rate
- Mean arterial pressure > 70 mmHg (yes/no)
- Noradrenaline dose
- Dopamin dose
- Steroid administration (yes/no)
Added parameters for potassium control.
- Last potassium measurement
- Diuresis over the last 6 hours
- Last creatinine measurement
- Presence of renal replacement therapy
Architecture of the potassium algorithm
Potassium (and glucose) levels were determined in lithium-heparin anticoagulated blood in 1.5 ml syringes (Pico, Radiometer Copenhagen) taken from an arterial line . Potassium level was determined with an ion-selective method by a point of care (POC) blood gas analyzer (ABL-Radiometer 700 or 800 series) present at the ICU. The minimal sample size needed was 0.1 ml. The POC-analyzer submitted measurements to the central hospital information system, from which measurements were queried by GRIP-II. Serum potassium measurements were only rarely used, as measurements in anticoagulated blood should not be directly compared to serum measurements, since serum potassium is sensitive to the phenomenon of pseudohyperkalemia . Hypokalemia was defined as a potassium level <3.5 mmol/L and hyperkalemia as a potassium level >5.0 mmol/L.
Patients received potassium either enterally or by a central venous catheter. Before implementation of GRIP-II the potassium intake was reviewed daily by the attending physician or more frequently in case of marked hypo- or hyperkalemia. To minimize errors in (the interpretation of) dosing potassium was administered in a "one-to-one" solution (50 mmol of potassium chloride in 50 mL) by a syringe pump either to a central venous catheter or to a gastric, duodenal or jejunal tube. As with insulin, only continuous delivery without boluses was used for potassium administration. In all cardiac surgery patients, magnesium suppletion of 30 mmol/day was given and in other patients in case of hypomagnesemia (i.e. < 0.80 mmol/L) .
Data collection and analysis
At the moment of data collection, the GRIP program had been running for 16 months at the surgical ICU and for 11 months at the cardiothoracic ICU. We included patients who were admitted between 6 months before and 12.5 months after implementation of GRIP-II at the surgical ICU and between 6 months before and 10.5 months after implementation of GRIP-II at the thoracic ICU. All patients admitted during those study periods were included. Information was collected both from the GRIP-II system itself and from the central hospital information system. Actual compliance of the nurses with the recommendations given by the program was recorded. Any change from the advice of GRIP-II was counted as non-compliance. With written inquiries we measured the impact of the computer program as perceived by the nurses and their opinion about (computerized) potassium control six months after the program had become part of routine care.
Before further analysis we calculated each patient's potassium curve using linear interpolation. With these individual curves, the prevalence of hypokalemia (or hyperkalemia) was calculated as the duration in the hypokalemic range (or hyperkalemic range) divided by the total duration of ICU-stay . Means were expressed with a standard deviation (SD) and compared with the Students t-test. In the case of skewed data (as assessed with kurtosis) medians with interquartile ranges (IQR) were used, and compared with the Mann-Whitney U test. Categorical variables were compared with the Chi-square test. A double-sided P value < 0.05 was considered significant. All statistical analysis was performed using SPSS (Statistical Package for the Social Sciences) version 15.0.
Comparison of patient groups before and after the implementation of computerized potassium regulation with GRIP-II.
Age (mean ± SD)
62 ± 16
61 ± 15
Male sex (%)
Reason of admission (%)
APACHE II (mean ± SD) *
15 ± 7
14 ± 7
Admission creatinine level, μmol/L (mean ± SD)
91 ± 56
98 ± 78
Acute kidney injury during ICU admission (%)†
Renal replacement therapy (%)+
Point of Care potassium/glucose measurements (patient-day)-1
Length of stay (days) at the ICU
Length of hospital stay (days)
Hospital mortality (%)
Nurses' opinion on computerized potassium control (GRIP-II).
Potassium control is important.
Working with GRIP-II is simple.
GRIP-II is a good tool to regulate potassium with.
GRIP-II is an improvement over the previous potassium control.
GRIP-II is reliable.
You feel more secure about preventing hyperkalemia with GRIP-II.
The labelling system is effective
Less frequent consultation of the attending physician about potassium after the introduction of GRIP-II is an advantage.
Incorporation of a potassium replacement algorithm into an already existing computerized clinical decision support system for glucose regulation led to a reduced prevalence of abnormal potassium levels compared with physician-driven potassium regulation in the ICU.
The relevance of avoiding severe potassium abnormalities cannot be overstated. In the ICU both hypokalemia and hyperkalemia frequently occur. Disorders in the potassium homeostasis are associated with serious complications like cardiac arrhythmias and sudden death . Many cases of abnormal potassium values are iatrogenic and probably sometimes even the result of frank errors [10–12]. We developed and implemented a nurse-driven computerized potassium regulation protocol to improve efficiency of potassium regulation and patient safety. The GRIP-II program was specifically designed to reduce the potential errors. Example of a safety feature, the labelling system, which was considered by the nurses to be effective, was introduced to eliminate written copied instructions. Also in case of a markedly abnormal potassium level (<2.8 mmol/L or >6.0 mmol/L) the attending physician must be notified, so that GRIP-II in fact is also a computerized alert system. Likewise, GRIP-II requests physician notification in case of potassium infusion rates over 12 mmol/h. It should be noted that the improved potassium regulation in both directions (i.e. in preventing both hypokalemia and hyperkalemia) was achieved only with regulating potassium infusion. GRIP-II does not provide other advices on hyperkalemia apart from stopping potassium infusion.
We believe that the care taken to integrate GRIP-II into the nurses' workflow has contributed to its success, since this is known to be essential to make a clinical decision support system a success . As described, the entire routine (from taking a blood sample to changing the potassium and insulin infusion rates) is one coherent action that takes about 4 minutes. The addition of potassium regulation to the GRIP program did not add any significant nursing time or costs, because computerized glucose control was already routine practice and potassium and glucose are measured from the same blood sample, and only two additional parameters had to be entered into the GRIP-II computer. Our data show, that after only 5 weeks more than 95% of the time all potassium levels were completely regulated by GRIP-II. Our nurses were already used to working with the GRIP program for glucose control, so when implemented in other institutions compliances rates will probably increase more gradually.
Remarkably, very few papers have explicitly described strategies how to regulate potassium in ICU patients [8–12, 17, 18, 29]. Analogous to glucose control, potassium control may even be perceived as tedious. When physicians must be involved in all minor derangements of an ICU patient, the necessary (telephonic) consultations with the attending physician may be viewed as neither particularly efficient nor optimal as physicians caring for ICU patients have more than sufficient inherently complex problems to handle, many of which cannot be handled by algorithms such as GRIP. As with glucose-control, it has been demonstrated that protocol-driven electrolyte replacement is superior to physician-driven electrolyte replacement in the intensive care setting [10–12]. A prospective study by Hijazi et al comparing protocol-driven and physician-driven potassium, magnesium and phosphate replacement concluded that protocol-driven replacement was associated with more efficient regulation (timely replacement and fewer missed low levels) . In a small retrospective study the implementation of an electrolyte dosing order form resulted in greater efficiency for potassium replacement without an increase in the number of adverse events . However, the study group was too small to draw conclusions about safety. Kanji et al evaluated the implementation of a paper electrolyte replacement protocol in 63 ICU patients and also this protocol resulted in more efficient electrolyte replacement . To our knowledge, there are no reports of a computerized potassium recommendation protocol in the ICU. Computer software is recognized as a tool to reduce serious medication errors and improve adherence to recommended care [13, 14, 17, 30].
Our study has a number of limitations. Although the importance of avoiding frank hypokalemia or hyperkalemia is obvious, especially in critically ill patients, it is not known if 'strict' potassium control, like glucose control, would be of clinical benefit . Also it is not known if computerized decision support systems improve patient outcomes . Our study was not designed or powered to detect differences in the outcome of ICU patients who received the computerized potassium control achieved by GRIP-II. Response of the nurses to the questionnaire was not complete but only 61%.
Because of the before-after study design, potential bias could have been introduced in to our study. Patients were not randomly assigned to physician-driven or computer-driven potassium control. Between the two study groups, there were a significantly higher number of potassium measurements per patient per day. We believe that the rise in the average number of requested blood samples from 5.3 to 5.9 per day was not caused by the addition of the potassium algorithm but by the sharpened glucose control during the study period as most samples were combined potassium and glucose measurements. Another limitation is that before the implementation of a computerized protocol, potassium control was physician-driven. Conceivably the introduction of a nurse-based paper-protocol would also have improved potassium control. However, computerized protocols are known to have several advantages over paper-protocols, such as better compliance and more efficient control .
Analogous to studies on intensive insulin therapy, relations between potassium and outcome can only be investigated when an adequate protocol and infrastructure for realizing potassium control are in place . We believe this can be achieved with systems such as the GRIP-II program. Likewise interactions between glucose, insulin and potassium as they are presumed to occur with the administration of GIK (glucose-insulin-potassium) in acute myocardial infarction, can better be studied with a system such as GRIP-II .
Several variables that influence the potassium regulation are not considered in our potassium regulation protocol. For example, the effect of acid-base disorders, insulin infusion and potassium administration route are possible extensions of the GRIP-II potassium algorithm. We aim to combine the potassium and the glucose algorithm in the future, so that for example GRIP-II can anticipate that a high insulin infusion can decrease potassium levels and thus increase the potassium infusion at the same time. The advantage of a computerized clinical decision support system over a paper-protocol is that it can employ a complex algorithm, while maintaining a simple interface.
Our study concerned the extensions of a computer decision support system specific to our ICU. Although the code of the system is freely available on the internet, to our knowledge no other ICUs have implemented it thus far. Successful introduction will also depend on a structured educational effort. Unlike most computerized decision support systems, GRIP-II is independent of a patient data management system (PDMS) which makes it widely applicable. Likewise, if an institution prefers diluted potassium chloride over a concentrated solution, the recommendation concerning the infusion rate of GRIP can be easily converted. We think the usefulness of the integration of potassium with insulin recommendation is not limited to our system. The algorithm behind potassium control is relatively simple, as outlined in the methods section. This could easily be added to a paper insulin protocol or different computer system than ours.
In conclusion, computerized potassium control, integrated with a nurse-centered program for glucose regulation (GRIP) is safe, effective and reduces the prevalence of hypo- and hyperkalemia in the ICU.
The program code for the GRIP-II program is freely available as open source from http://grip-glucose.sf.net/.
intensive care unit
glucose regulation in intensive care patients
glucose and potassium regulation in intensive care patients
glomerular filtration rate
statistical package for the social sciences
patient data management system
- APACHE II:
acute physiology and chronic health evaluation II score.
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