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.

Cardiovascular System

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.

E. Central venous pressure is an effective way to monitor fluid therapy in patients with congestive heart failure, oliguric renal failure, and septic shock. CVP monitoring requires a jugular catheter, water manometer, 3 way stopcock, and extension tubing. The catheter should rest in the anterior vena cava. When properly placed, the fluid meniscus in the manometer will show small fluctuations with the heartbeat and larger movements with respiration. To measure CVP, fluids are turned off to the patient, allowing the manometer to fill. Then the stopcock is turned to stop flow from the fluid bag, allowing the fluid in the manometer to flow into the patient until it equilibrates with the patient's CVP. The zero point is determined by drawing a horizontal line between the manubrium and the manometer, and the CVP is the patient reading minus the zero point. The patient should always be in the same position when CVP is measured. By monitoring the trend in CVP, problems of overhydration or underhydration can be detected early and reversed. Normal CVP ranges from -1 to +5 cm H2O. If the CVP increases by more than 3 cm H2O or if the total value exceeds 8-10 H2O, intravenous fluids should be discontinued. High CVP values (> 10 cm H2O) are associated with fluid overload, cardiac failure, pericardial effusion, pneumothorax and positive pressure ventilation. Low values indicate hypovolemia or vasodilation. False readings will be obtained if there is a kink or clot in the catheter.

F. Packed cell volume, total solids (PCV, TS) - In order to appropriately manage fluid therapy and detect problems of anemia, dehydration, or hypoproteinemia, trends in PCV and TS should be monitored at least twice daily in critical patients and more frequently in unstable patients.

G. Serum electrolytes (Na+, K+, Ca+) - Because of potential systemic effects, particularly on the heart, these values should be monitored in critical patients so that imbalance can be corrected through supplementation of intravenous fluids.

Pulmonary System

A. Respiratory rate and effort - Animals with labored respiration should receive supplemental oxygen (either by mask, oxygen cage, or nasal catheter) and should not be stressed. Tachypnea (↑ respiratory rate) may indicate hypoxia, hyperthermia, pain, hypercapnea, early sepsis, or metabolic acidosis. Bradypnea (↓ respiratory rate) may be seen with lesions of the central nervous system or drug overdose.

B. Auscultation, characterization of breathing pattern - Five breathing patterns may be seen in critical patients. Upper airway obstruction is characterized by noisy breathing and inspiratory dyspnea. Pleural space disease (pneumothorax, pleural effusion) is characterized by rapid, shallow respirations and muffled heart and lung sounds ventrally. Diseases of the small airways, such as feline bronchial asthma, are characterized by expiratory dyspnea (forced expiration with abdominal press), increased bronchial sounds, and coughing. Lung parenchymal disease, such as pulmonary edema or pulmonary contusions is characterized by labored inspiration and expiration and crackles and wheezes on auscultation. Tachypnea may be secondary to pain, anxiety, trauma, excitement, fever, anemia, or acidosis.

C. Blood gas analysis is helpful in the assessment of pulmonary problems. An arterial sample is necessary to evaluate pulmonary function. The syringe must be coated with heparin and all air bubbles expressed from the sample. The needle is occluded with a stopper and the sample placed in an ice bath until it can be evaluated. Increased levels of carbon dioxide (paCO2 > 60 mm Hg) indicate hypoventilation. Intubation and assisted ventilations may be required. Decreased arterial oxygen (PaO2 < 60 mm Hg) indicates clinically significant hypoxia, and oxygen supplementation should be provided.

D. Pulse oximetry is a quick method of screening for clinically significant hypoxia. It measures oxygen saturation of hemoglobin, which normally ranges from 95 - 100%. Pulse oximetry readings less than 90% can be associated with significant hypoxemia (PaO2 < 60 mm Hg) and should cause the clinician to critically evaluate the patient. Unfortunately, pulse oximetry is less accurate in patients with poor perfusion, anemia, or arrhythmias and is not a substitute for blood gas analysis. Movement or shivering can create motion antifacts which are also a source of error. Pulse oximetry has been a very effective monitor when used on the tongue of anesthetized patients.

Central Nervous System

A. Level of consciousness (LOC) - It is important to establish a baseline and monitor trends. The 4 LOC's described in animals include: (1) Normal - alert, awake, responsive to surroundings; (2) Obtunded - depressed and drowsy but easily arrousable; (3) Stuporous - in a deep sleep but arrousable with pain stimulus; (4) Comatose - no response to external stimuli, including pain.

B. Pupillary response - Pupil size and response to light should be evaluated and trends recorded.

Urinary System

A. Urine output is an excellent reflection of overall tissue perfusion. Normal urine output should be 1-2 ml/kg/hr. Lower amounts may indicate poor perfusion, hypotension, or impending renal failure. Urine output can be quantitated through sterile catheterization of the bladder and collection through a closed system, but indwelling catheters predispose to infection. Other methods of urine collection include walking and collecting urine in a bowl, metabolic cage, or weighing disposable diapers before and after urination. It is important to monitor urine output in animals with polyuria so that ongoing fluid needs can be met.

General Concerns

A Patient rounds - should always be held at shift changes. This allows the nurse and the veterinarian to discuss cases, review and revise patient orders, and monitor response to treatment.

B.Basic physical examinations - At the beginning of each shift, a basic physical examination should be performed to establish a baseline for each patient. This should include TPR, auscultation, mentation check, palpation of bladder, checking fluid lines and catheter sites.

C.Fluid Therapy - Fluid input should be recorded hourly for each patient, and the bag or bottle marked with a strip of tape indicating expected fluid levels according to time of day.

D.Catheter Care - Nurses should be in the habit of checking catheter sites for wetness, pain, erythema, heat, or swelling. Catheters should not be left in place for more than 72 hours

E.Recumbent patients - should be turned every 2-4 hours unless sternal to prevent decubital ulcers on pressure points and atelectasis of the dependent lung. Passive exercise (manipulation of extremities) should be done to improve muscle tone unless contraindicated.

F.Cleanliness - Nosocomial infections are infections acquired in-hospital. To prevent occurrence, hands should be washed frequently and between each patient. Injection ports should be disinfected before administering IV medications to immunocompromised patients.

G.Records - Accurate record keeping is vital to critical care patient management. Patient records should be arranged in chart form so that trends can be easily recognized. All observations should be recorded legibly.

Key words: Nursing, monitoring, critical care, nosocomial infections, pulse oximetry, cardiac arrhythmias, canine, feline.