Hemodynamic instability in septic shock

A bedside clinical and ultrasound-based approach to hemodynamic instability - Part II: bedside ultrasound in hemodynamic shock: continuing professional development

Shock is defined as a situation where oxygen transport and delivery is inadequate to meet oxygen demand. The patient in shock is evaluated through medical history, physical examination, and careful observation of the hemodynamic and respiratory monitors. The patient is initially managed with basic resuscitation measures, however bedside ultrasound should be performed if hemodynamic instability persists. We propose to use ultrasound of the inferior vena cava (IVC), and the concept of venous return, as the initial step in order to identify the mechanism of shock. Doppler examination of the hepatic venous flow can also be added. Further ultrasound examination of the patient's heart, thorax, and abdomen can then be performed in order to determine the etiology of shock. In patients with reduced mean systemic venous pressure, an examination of the patient's thoracic and abdominal cavities to detect free fluid, pneumonia, or empyema can be considered. In patients with increased right atrial pressure, transthoracic echocardiography will allow identification of left or right ventricular dysfunction. Finally, in the presence of increased resistance to venous return, thoracic examination for pneumothorax or cardiac tamponade and abdominal examination for signs of abdominal compartment syndrome or IVC occlusion can be considered. Subsequent treatment can then be tailored to the etiology of shock. Elements of bedside ultrasound examination are currently taught in many anesthesia training programs.

PURPOSE

To develop an approach to the patient in shock that incorporates bedside ultrasound examination.

Serum cystatin C as a marker of renal function in critically ill patients with normal serum creatinine

Background:

Serum creatinine as a classic marker of renal function has several limitations in the detection of renal dysfunction.

Objectives:

This study assessed the validity of serum cystatin C as a marker of renal function in critically ill patients with normal serum creatinine.

Patients and Methods:

Eighty adult patients referred to intensive care units with serum creatinine levels < 1.5 mg/dL and without hemodynamic instability were chosen and their serum creatinine and cystatin C levels were measured. A 24-hour urine sample was collected to calculate creatinine clearance (Ccr). Renal dysfunction was defined as Ccr < 80 mL/min/1.73 m².

Results:

There were significant correlations between measured Ccr and 1/serum creatinine (R = 0.51, P < 0.001) and 1/serum cystatin C (R = 0.25, P = 0.028). The difference between false negative rates of serum creatinine (93.33%) and cystatin C (80%) in the detection of renal dysfunction was significant (P = 0.032). Receiver operating characteristic curve analysis illustrated that area under the curve of serum creatinine and cystatin C for detecting renal dysfunction were 0.711 and 0.607, respectively; however, this difference was not significant (P = 0.222).

Conclusions:

Our data demonstrated that serum cystatin C is not superior to serum creatinine in the early detection of renal dysfunction in critically ill patients.