Intermittent Automatic Veno-Venous Hemofiltration (IVVHF) and Potassium Removal: Possible Role in Hyperkalemia

Introduction

Removal of potassium ion is frequently one of the main indications for hemodialysis in acute renal failure (ARF). Traditionally, this procedure has been performed in ICU setting in patients who require substitution therapy. Nevertheless, sometimes this procedure cannot be done due to the clinical status of ICU patients, in which poor hemodynamic condition does not make dialysis a safe procedure. In last years, some experience with potassium removal has been achieved with slow continuous hemofiltration procedures[[1]], [[2]], [[3]] but little work has been done with intermittent hemofiltration (IVVHF) procedures though. Our group has some preliminary experience with IVVHF techniques and potassium removal, so we decided to assess potassium mass transference using this technique. Our aim was to establish weather IVVHF is an effective technique in potassium removal in an emergency-based indication procedure.

Patients and Methods

Eleven patients admitted to the Catholic University of Chile Hospital from 1997 to 1999 were studied, all of them in ICU setting. Ten of them were male, and mean age was 59 ± 20.6 years. Table 1 shows clinical data of these patients. All of them required renal replacement therapy on a clinical-based indication, 10 of them because of ARF in Shock and 1 with chronic renal failure and recent stroke. We used a Gambro AK10 Machine, with a Gambro FH66D Polyamide Hemofilter with a 0.6 square meter area. Serum pre IVVHF and post IVVHF was measured, using selective-ion method. Ultrafiltrate (UF) K⁺ concentration mas measured as well. Reposition fluid volume and K⁺ concentration and UF volume were registered.

Table 1. Clinical data of patients in study

Male	Shock	65
Male	Shock	56
Male	CHF	90
Male	Sepsis	72
Female	Sepsis	38
Male	AMI	41
Male	AMI	42
Male	Sepsis	77
Male	CHF	17
Male	CHF	66
Male	Sepsis	71
Mean ± SE		57 ± 6.3

CHF: congestive heart failure, AMI: acute myocardial infarction.

Statistical analysis was done using simple regression analysis, with p<0.01.

Results

Table 2 shows serum pre and post and UF K⁺ concentrations among patients. Mean pre IVVHF serum K⁺ was 5.03 ± 1.90 mmol/L (range from 3.27 to 6.8 mmol/L), and mean post IVVHF K⁺ was 4.28 ± 0.73 mmol/L (range from 3.4 to 5.48 mmol/L). HF time in our patients was 246 ± 78 min with total filtered volume of 12.8 ± 3.1 L (range from 9 to 17 L).

Table 2. K⁺ concentrations and volumes during hemofiltration procedures

Patient	Pre HF K^+	Post HF K^+	Delta K^+	HF sol K^+	Vol HF L	NHF sol K^+	UF K^+	TKT	NKT	HF t
1	6.8	5.1	1.7	0	9	0	5.1	45.9	45.9	3
2	6.17	4.97	1.2	2	9.9	19.8	5.7	57	37.2	4.25
3	4.7	4.08	0.62	3	12.2	36.6	3.87	47.2	10.6	3.25
4	3.27	4.02	−0.75	3.5	17	59.5	3.48	59.16	−0.34	6.25
5	5.4	3.4	2	2.5	16.6	41.5	3.3	54.78	13.28	5.25
6	3.49	3.49	0	3.5	10.3	36.05	3.5	36.05	0	3.16
7	4.03	3.53	0.5	3.5	16.4	57.4	3.13	51.3	−6.1	5.25
8	5.2	3.85	1.35	3	12	36	3.78	45.36	9.36	3
9	5.33	4.96	0.37	2	10.1	20.2	4.6	46.6	26.4	2.67
10	5.8	5.48	0.32	2	16.3	32.6	5.4	88.02	55.42	5.8
11	5.14	4.21	0.93	2.5	10.9	27.25	4.6	50.14	22.89	3.25
Mean ± SE	4.8 ± 0.9	4.2 ± 0.6	0.6 ± 0.7	2.7 ± 0.6	13.1 ± 2.8	36.3 ± 12.8	4.1 ± 0.8	53.4 ± 13	17.1 ± 18	4.2 ± 1.2

Pre HF K⁺ serum potassium concentration pre IVVH (mmol/LT), post HF K⁺ post IVVH, delta: difference between pre and post K⁺, HF sol K⁺: concentration in Hemofiltration reposition solution; Vol HF: volume (L) of reposition solution; NHF sol K⁺: total amount of K in reposition solution; UF K⁺: K⁺ concentration in ultrafiltered solution; TKT: total K⁺ transferred; NKT: net K⁺ transferred; HF t: procedure time (h).

We found positive correlation between UFK and post IVVH K⁺ (r = 0.914 and p<0.0001) and between net K⁺ transfer and post IVVH K⁺ (r = 0.895, p = 0.0002) but there was no correlation between Total K⁺ transfer and post IVVH K⁺ (r = 0.644, p = 0.032). In addition, UF K⁺ was positively correlated with NKT (r = 0.916, p<0.0001).

Discussion

Traditionally, conventional hemodialysis has been used as a classical indication for treatment of hyperkalemia,[[4]], [[5]], [[6]], [[7]] as an effective treatment for this complication. In recent years, some experience has been reported with usage of continuous hemofiltration, as an effective therapy for this complication, usually in the ICU environment.[[1]], [[2]], [[3]] This procedure mainly uses convective extracellular fluid exchange, rather than diffusion exchange (as hemodialysis), but it has shown quite effective in treatment of hyperkalemia.

As could be expected, positive correlations were found between net K⁺ transfer (NKT) and ultrafiltered solution K⁺ (UFK) content. Both, UFK and NKT were correlated with post IVVH K⁺ content, but not with pre IVVH K content. Lack of correlation amongst post IVVH K and total K⁺ transfer (TKT) can be explained because TKT includes potassium that was administered with HF solution.

This article assesses the use of an intermittent hemofiltration procedure as an alternative treatment for hyperkalemia. This procedure can be used in an ICU and non-ICU setting as well. In our patients, this procedure was used during 4.2 ± 0.377 h, and we obtained a post IVVH potassium (delta) of 0.663 ± 0.204 mmol/L. This change in serum K⁺ may be clinically relevant and suggests that IVVH could be considered as a possible alternative procedure in managing acute severe hyperkalemia.