Nursing care of seriously ill cats and dogs (Proceedings)
Nursing care of critically ill patients can be the determining factor in whether a patient lives or dies. Even if the correct diagnosis has been made and appropriate therapy initiated, critical patients will die without effective nursing care. Seriously ill patients have dynamic disease processes, which can rapidly change from stable to critical in a relatively short period of time. The important keys in preventing patient demise are to monitor critical patients effectively, look for trends, assess patient status, and revise the therapy accordingly. Life threatening complications should be anticipated and corrected before they occur. The primary systems to monitor in critical patients include the cardiovascular, respiratory, neurologic, and urinary, since a dysfunction in any of these 4 systems can lead to the death of the patient.
A. Mucous membrane color, capillary refill time, heartrate, pulse quality: These parameters are important in assessing whether the animal is maintaining adequate perfusion. In shock states, peripheral vasoconstriction occurs and blood is shunted from the extremities, skin, and muscle to the heart and brain. In addition, the heart rate increases in states of poor perfusion. Early signs of shock reflect hypermetabolism, and include bounding pulses, elevated heart rate, and injected or brick-red mucous membranes with a rapid capillary refill time (< 1 sec). These signs are particularly noticeable in early septic shock because of the peripheral vasodilation which accompanies this syndrome. If untreated, hypermetabolic shock will progress to a hypometabolic state in which poor perfusion is evidence by pale or blanched mucous membranes, slow capillary refill time (> 2.5 sec), tachycardia, and weak, thready pulses. Signs of shock warrant aggressive diagnostics to determine the underlying cause of poor perfusion (hypovolemia, cardiac dysfunction, or sepsis). Signs of shock in a previously stable patient may indicate internal hemorrhage, fluid loss in excess of fluid input, development of sepsis, or decompensation of cardiac function. Cardiogenic shock is usually accompanied by signs of respiratory distress associated with pulmonary edema, and should be treated with diuretics, oxygen, vasodilators, and drugs to improve cardiac function. Hypovolemic shock must be treated aggressively with volume replacement using crystalloid or colloid solutions. Septic shock is treated with fluids and antibiotics while a search for the septic focus is pursued.B. Cardiac auscultation - It is important to assess the patient's cardiovascular status by ausculting the heart for murmurs or rhythm disturbances. Previously undetected murmurs may indicate bacterial endocarditis in patients showing signs of shock. Irregular cardiac rhythms should be assessed with simultaneous palpation of peripheral pulses. If pulse deficits are detected (more beats auscultated than palpated), arrhythmias are present. Causes of arrhythmias in critical patients include hypoxia, myocardial contusion or ischemia, acid/base or electrolyte abnormalities, and underlying heart disease.
C. Electrocardiographic (ECG) monitoring allows for more accurate assessment of cardiac rhythm and conduction disturbances by reflecting the electrical activity of the heart. Ventricular arrhythmias are common in dogs presented for traumatic injuries, shock, or gastric-dilatation-volvulus, but usually do not appear until 12-24 h after initial presentation to the hospital. Animals at risk for arrhythmias can be monitored with a continuous ECG. Treatment should include oxygen supplementation, correction of acid-base disturbances, pain management, volume replacement, and anti-arrhythmic agents.
D. Blood Pressure can be measured directly or indirectly. Indirect measurement requires a cuff with a diameter approximately 40% of the limb circumference which is inflated to occlude blood flow. Doppler instrumentation (Parks Electronics, Aloha, OR) detects blood flow through a piezoelectric crystal placed over the artery and converts it into an audible sound. As the cuff is deflated, the first audible sound indicates the systolic blood pressure. Oscillometric instruments (Dinamap, Critikon, Inc., Tampa, FL) display systolic, diastolic, mean blood pressure, and heartrate. Indirect blood pressure monitoring is less accurate in conditions of vasoconstriction, hypovolemia, and hypotension.
Direct blood pressure monitoring is more accurate and provides continuous monitoring, but requires an arterial catheter, oscilloscope, and transducer. Normal systolic, diastolic, and mean blood pressures are 100-160, 60-100, and 80-120, respectively. Systolic pressures < 80 mm Hg or mean BP < 60 mm Hg are indicative of inadequate perfusion and warrant therapy.