replacement therapy
Renal replacement therapy includes the modalities of hemodialysis, peritoneal dialysis, continuous renal replacement therapy, and renal transplant. While typically employed for treatment of ESRD, these therapies are also used for management of severe cases of acute kidney injury including poisonings, symptomatic uremia, and severe fluid overload.
Hemodialysis
Hemodialysis filters the patient’s blood to rapidly remove fluid and solutes. Home hemodialysis is possible for select patients. Specialized vascular devices enable rapid infusion and removal of blood. These devices must be able to support over 350 mL/min of blood flow, with some patients achieving rates of 600‐1200 mL/min [3].
A dialysis patient’s access site should not be used except in critical emergencies (e.g., cardiac arrest resuscitation). Patients are advised to avoid use of blood pressure cuffs, tourniquets, and venipuncture on the extremity that has their access, and they will typically convey this concern to EMS personnel [4]. There are several dialysis access options:
AV fistula – a surgically created connection between an artery and a vein, usually from the brachial or radial artery to the cephalic vein. It takes longer than 4 weeks, and often more than 8 weeks, to “mature” and be ready to use. A patient may have a fistula created and be in the process of maturation while using a different access device for dialysis [5].
AV graft – similar to a fistula, the artery and the vein are connected by way of a synthetic device. It is more prone to complications than a fistula [5].
Tunneled catheter – a large IV catheter that accesses a central vein, usually the internal jugular [6]. Prior to entering the vein, the catheter is run through the skin and soft tissue from a different site (i.e., tunneled). Doing so reduces risks of infection and need for frequent dressing changes [7]. The catheters are often held in place by balloons and other securing devices. This method has the advantage in that it is immediately available for use once inserted. Compared to other long‐term methods of venous access, the catheter has the highest rates of complication and mortality [4,7].
Nontunneled catheter – a large‐bore IV in a central vein with two ports. It is typically used as a temporary bridge to a different device [8].
Peritoneal dialysis
For peritoneal dialysis, the patient’s own abdominal contents, rather than an external machine, serve as the dialysis membrane. The patient has a permanent catheter through the abdominal wall, which itself can be a source of complications. Typically, the patient will require several exchanges of fluid to reach his or her goal. The exchanges may be automated to occur during sleep or may be performed with several extraction/replacements of fluid spaced throughout the day [4, 9].
Renal transplant
An alternative to dialysis for ESRD patients is renal transplantation. A successful transplant can allow a dialysis‐dependent patient to live a nearly normal.
Typically, the patient’s new kidney is implanted in the abdominal cavity or pelvis. This has implications for any patient complaining of abdominal pain. A renal cause (e.g., transplant rejection) must be considered. Furthermore, the kidney is not protected in its native location in the retroperitoneum. The physical exam and focused history after trauma should be mindful of this anatomical difference, although outcomes and injury patterns may not be significantly different from those of nontransplant patients [10].
Kidney transplant patients continue to receive immunosuppressive medication to avoid rejection. They may not mount fevers with infection and are at risk for atypical and opportunistic infections. Vague and mild symptoms may actually be concerning signs and should warrant careful evaluation. A thorough medication history can alert the EMS clinician to the presence of immunosuppression.
Complications of renal disease
Many of the complications of renal failure are more likely to be found in those with no remaining renal function. While possible in the acute renal failure patient, those known to be dialysis dependent more often present to EMS with one or more of the following acute complications of chronic disease.
Fluid overload
Fluid overload in renal disease is similar to congestive heart failure. Given the prevalence of comorbidities such as hypertension and cardiac disease in this population, dyspnea and pulmonary edema may result from either pump failure from a primary cardiac etiology, or excretion failure from the poor renal function. Additionally, the ESRD patient may enter a state of high‐output heart failure due to the presence of an AV fistula. The inability to clear waste products can also result in uremic cardiomyopathy [4].
Diagnosis and treatment of fluid overload in this patient population overlap with the heart failure cohort. In the acutely ill patient, management is similar, including oxygen and nitrates. High‐flow nasal or face mask oxygen, noninvasive positive‐pressure ventilation, or intubation and ventilation may be required for worsening respiratory distress. Focused point of care ultrasound can provide information regarding the nature of cardiac contractility or pericardial effusion from uremia. Ultimately, dialysis may be required to offload fluid and facilitate return to baseline hemodynamic and pulmonary function [4, 11]. The availability of emergent dialysis must be considered by the EMS clinician when deciding on the most appropriate destination for the patient.
Potassium
Perhaps the most well‐known and feared complication of renal failure is that of hyperkalemia. The healthy kidney excretes 95% of the daily potassium intake [12]. Fatal arrhythmias are most likely to occur with serum levels over 9 mEq/L [13]. Hyperkalemia is associated with poor outcomes in both the general population and in patients with renal disease. It has been found to be an independent predictor of inpatient mortality [14]. Nonetheless, a patient with CKD can often tolerate higher levels of potassium than a healthy individual can and generally has a lower risk of mortality for any given serum potassium level as compared with the general population [15]. In contrast to other electrolyte abnormalities, the patient with hyperkalemia may not voice any specific complaints. The ECG is often used as a screening test for electrolyte disturbance, but it has overall poor sensitivity and specificity (Figures 22.1 and 22.2). ECG tracing changes that may be seen in hyperkalemia are listed in Table 22.1. While it is an easy and noninvasive test, the EMS clinician must not exclusively rely on an ECG for patient evaluation [13]. Specific management of hyperkalemia will be addressed later in the chapter.
Figure 22.1 ECG of a patient with hyperkalemia. Note wide complex tachycardia and development of sine wave.
Figure 22.2 ECG of patient with hyperkalemia with junctional bradycardia.
Magnesium
Like potassium, the kidney functions to excrete magnesium from the body. A kidney that is impaired by acute or chronic disease may lose its ability to conserve magnesium, while ESRD implies loss of ability to excrete magnesium. Thus, hypomagnesemia