Postrenal acute kidney injury may be caused by:

Choice A reason: Normal Saline is an isotonic crystalloid solution that is commonly used to treat hypovolemic shock. Hypovolemic shock occurs when there is a significant loss of blood or fluids, leading to decreased circulating blood volume and impaired tissue perfusion. The administration of Normal Saline helps to restore the intravascular volume, improve blood pressure, and enhance tissue perfusion. It is considered the first-line treatment for fluid resuscitation in hypovolemic shock because it quickly replaces lost volume without causing significant shifts in fluid balance.

Choice B reason: Vasoconstrictor agents are medications that constrict blood vessels, which can help to increase blood pressure. However, in the context of hypovolemic shock, they are not the first line of treatment. The primary issue in hypovolemic shock is the loss of blood or fluid volume, and the initial focus should be on volume replacement. Vasoconstrictor agents may be used later if there is persistent hypotension despite adequate fluid resuscitation, but they are not appropriate as the initial therapy.

Choice C reason: Steroids are anti-inflammatory agents that can be used in various medical conditions, but they are not indicated for the immediate treatment of hypovolemic shock. The primary concern in hypovolemic shock is rapid volume replacement to restore perfusion. Steroids do not address the underlying issue of fluid loss and are not appropriate in this acute setting.

Choice D reason: 5% Dextrose in water is a hypotonic solution that is primarily used for providing free water and sometimes for delivering glucose. It is not suitable for treating hypovolemic shock because it does not effectively expand the intravascular volume. In fact, it can exacerbate fluid shifts and may lead to worsening hypotension. The appropriate initial therapy for hypovolemic shock is an isotonic solution like Normal Saline, which effectively increases the circulating blood volume.

Choice A reason: Hypercalcemia refers to high levels of calcium in the blood, but a positive Chvostek sign is not indicative of hypercalcemia. In fact, hypercalcemia generally results in symptoms such as muscle weakness, fatigue, and nausea rather than the specific neuromuscular irritability seen with a positive Chvostek sign.

Choice B reason: Hypocalcemia refers to low levels of calcium in the blood and is associated with a positive Chvostek sign. The Chvostek sign is a clinical test where tapping on the facial nerve triggers twitching of the facial muscles. This occurs due to increased neuromuscular excitability caused by low calcium levels.

Choice C reason: Hypophosphatemia refers to low levels of phosphate in the blood. It is not directly associated with a positive Chvostek sign. While electrolyte imbalances can affect neuromuscular function, hypocalcemia is specifically linked to the Chvostek sign.

Choice D reason: Hypermagnesemia refers to high levels of magnesium in the blood and is not related to a positive Chvostek sign. Hypermagnesemia often causes symptoms such as muscle weakness, nausea, and hypotension rather than the neuromuscular irritability seen with a positive Chvostek sign.