Surgical Patient Monitoring - Parameters to Be Followed

Introduction:

Monitoring the patient during the surgical procedure performed under anesthesia is important. The anesthesia alters the body's normal physiological status, which must be monitored for any abnormal changes in vital signs. Some of the most commonly measured parameters are blood pressure, heart rate, respiratory rate, electrical activity of the heart, and intracranial pressure. Such monitoring of the vital parameters is essential to prevent any unfavorable consequences that may occur during the surgery.

What Is Surgical Patient Monitoring?

The surgical procedure usually involves administering anesthesia, sedation, and intravenous fluids, while operating near vital organs like the heart, brain, liver, etc. These fluids and drugs within the anesthesia may cause certain changes to the patient’s body. Sometimes, an injury to the blood vessel near one of the vital organs may affect the blood pressure or increase the heart rate, which is monitored with the use of a patient monitoring system. Every operation theater has a monitor that displays all the parameters and is checked by the surgeon or nurse to see if the normal levels are being maintained. When vital levels become abnormal and necessitate immediate attention, the patient monitoring system issues an alert. In addition to monitoring during the procedure, post-operative monitoring is required if the patient is kept under observation after the procedure.

What Are the Parameters to Be Monitored During a Surgical Operation?

The following are the most important parameters that are measured during the surgical procedure:

• The electrical activity of the heart is measured using an electrocardiogram.

• The blood pressure is monitored for its values to be within the normal range of around 120/80 mm Hg.

• The respiratory rate, whose normal levels are 12 to 16 breaths per minute.

• When the general anesthesia lasts more than thirty minutes, the body temperature is checked using a temperature probe or thermometer. The average temperature usually ranges from 97.5 degrees Fahrenheit (36.1 degrees Celsius) to 99 degrees Fahrenheit (37.2 degrees Celsius).

• Cardiac output refers to the amount of blood the heart pumps in a minute. The normal range is between four to seven liters per minute. The range can vary depending on each individual’s metabolic needs.

• The arterial blood oxygen level is measured using a pulse oximeter with the help of a photoelectric sensor that holds the finger.

• Pulmonary functions include monitoring the end-tidal carbon dioxide (the amount of carbon dioxide released on exhalation).

• Patients undergoing surgery within the skull for trauma, tumor, or bleeding in the brain need to be monitored for their intracranial pressure.

The above-mentioned parameters are some of the most routinely recorded. Other parameters may also be included under the supervision of the surgeon, depending on the surgery performed.

How Are the Patients Under Anesthesia Monitored?

Whenever surgery is done under general anesthesia, the presence of the anesthesiologist is necessary at all times. The anesthesiologist checks the following factors after administering anesthesia to the patient:

• Oxygen Supply: The delivery of the gas mixtures is continuously monitored with the help of an oxygen analyzer along with an audible alarm. The alarm starts to beep when the levels become abnormal.

• Breathing Systems: In patients who are unconscious, deeply sedated, under airway devices, and with a tracheal tube (a tube inserted into the trachea to maintain the airway) have to be checked for carbon dioxide concentration levels. This helps in detecting airway disorders that require immediate management.

• Vapor Analyzers: When sedation or anesthesia is administered using volatile anesthetic agents, such as nitrous oxide, the end-tidal concentration of carbon dioxide is measured.

• Depth of Anesthesia: When neuromuscular blocking agents are used for anesthesia, the depth of anesthesia is monitored from the start till the end of the surgery.

The anesthesia not only produces an effect on consciousness and pain relief, but also a decrease in blood pressure. It also produces other effects, such as muscle tone reduction, reduced respiratory function, and decreased cardiac output. Since the patient's physiological condition changes, it is critical to carefully monitor the basic parameters.

Why Is the Body Temperature Monitored During Surgery?

Because of the surrounding temperature and fluid infusion, the body is exposed to a colder environment when a patient is undergoing surgery. The incisions or cuts that the surgeon places on the body lead to heat loss due to the evaporation of body fluids through the cut. General anesthesia reduces various functions within the brain, including the thermoregulatory center. The thermoregulatory center is a portion of the brain that helps keep the core body temperature within normal limits. This leads to hypothermia (reduction in body temperature). The body shows signs of shivering, which acts as a compensatory mechanism. Shivering causes rapid skeletal muscle contraction, which consumes energy and generates heat within the body. Another compensatory mechanism is the contraction of blood vessels at the extremities of the body to distribute blood to vital inner organs. The following complications occur due to hypothermia:

• Wound infections.

• Delayed wound healing.

• Shivering and discomfort.

• Stress within the heart due to the drop in the core body temperature.

• A prolonged hospital stay due to slow recovery.

Hence, recording the body temperature using infrared thermometers and thermistors (thermal resistors wherein the resistance changes when there is a temperature change) is necessary to prevent any complications of hypothermia.

How Are the Circulatory Functions Monitored During Surgery?

During an operation, a circulatory impairment may occur due to a change in the heart's contraction, decreased blood pressure, and oxygenation. The impairment leads to the release of inflammatory cells into the circulation, which, in turn, causes damage to multiple organs. Hence, intensive monitoring of the blood pressure, urine output, arterial pH, and blood lactate levels. The circulatory functions are recorded using a continuous ECG (electrocardiogram), a pulse oximeter, and a sphygmomanometer (to record the blood pressure using a cuff placed near the elbow).

• The ECG records the electrical activity of the heart by placing electrodes that receive a signal from the heart and are displayed on the monitor. This helps in detecting the abnormalities and functioning of the heart.

• A pulse oximeter is a non-invasive measurement of the amount of oxygen within the blood. It is helpful in inpatient as well as outpatient settings. The device is clipped to the forefinger and displays a reading. A normal reading of 95% is present in a healthy patient. A reading below 92% indicates a decrease in oxygen saturation.

• A sphygmomanometer consists of a measuring inflatable cuff and a monitor to display the reading. Manual and digital types are available. It measures the pressure within the blood vessels, and if the values go beyond or drop below the normal levels, it indicates an emergency and is managed immediately.

These are the basic parameters to be recorded to check the circulatory functions. Other advanced parameters that are recorded include vena cava assessment, central venous pressure, central venous oxygenation, thoracic bioimpedance, etc.

Conclusion:

The surgical monitoring of the patient allows for early detection of the abnormality and helps to manage it immediately. It is critical in all the surgical procedures performed under general anesthesia, which affect the body's normal functioning. It is up to the anesthesiologist, nurse, surgeon, and other doctors to frequently have a record of the vital readings to provide a successful outcome without the development of complications.