In 1625, an Italian physician measured body temperature by applying a numerical scale to his thermoscope. From that primitive thermometer to today's highly sophisticated surgical, portable and wireless telemetry monitors, patient surveillance has grown into a multi-billion-dollar industry. But the technology is only as good as the professionals who respond to them.
What's new in the OR?
When cardiac anesthesiologist Benjamin A. Kohl, MD, steps into the operating room (OR) at the Hospital of the University of Pennsylvania in Philadelphia, he is greeted by a phalanx of patient monitoring devices. Along with the perfusionist, surgeons, nurses, techs and other staff, Kohl keeps his eyes and ears attuned to the visual and audible cues of the patient's physiologic and hemodynamic status delivered by the various monitors.
Heart rate, ECG, oxygen saturation, blood pressure, central venous pressure, cardiac output and more—all these parameters must be carefully monitored while surgeons treat the heart, the perfusionist oxygenates the blood and the anesthesiologist medicates the patient. While these metrics are fairly standard in the OR, newer monitoring devices are emerging as important ways to increase patient safety and improve outcomes.
Kohl and his colleagues now utilize cerebral oxygen saturation monitors. Two stickers affixed to each of the patient's temporal regions of the head give the OR team a measure of the balance in oxygen saturation between the left and right hemispheres. "One of the morbidities that can occur with cardiac surgery is stroke," says Kohl, who is the director of the division of critical care. "We want to identify patients who are at risk or who suffer a stroke as soon as possible, so we can change therapy to minimize the injury." Regional differences in oxygen saturation would imply a lack of oxygen going to one side of the brain, potentially caused by an embolus impeding blood flow.
For some surgeries, the OR team will monitor the electroencephalogram (EEG), looking for electrical activity that signals a stroke. They also will enlist the EEG, somatosensory evoked potentials or motor evoked potentials to monitor the spinal cord. "One of the complicating factors during surgery on the descending thoracic aorta is paraplegia from the lack of blood flow to the spinal cord," Kohl says.
To remedy this complication, the team can improve blood flow to the spinal cord by increasing blood pressure, which is continually monitored via an intra-arterial catheter. A second option involves the use of a lumbar drain that surrounds the spinal cord. "If we see a decrease in blood flow to the spinal cord, we can decrease the pressure around the cord by allowing the fluid to drain, which increases perfusion pressure," Kohl says.
Sounding the alarms
Most monitors have the ability to be programmed with audible alarms that sound when a particular value is breached. For example, the ECG monitor can be programmed to go off if the heart rate is too slow or too fast; the peripheral and cerebral saturation monitors can be programmed to elicit alarms for drops in oxygen levels; and the spinal cord pressure monitor has an alarm. The EEG has no alarm but it is continuously monitored by a neurologist, Kohl says.
"We customize the alarms for each patient," he says. "Some patients might have a higher resting heart rate, such as 115 bpm, and we may not want the alarm to go off at 110 bpm, so we'll set it to 130, for example."
Kohl emphasizes that the technology is only one part of patient care in the surgical OR. Teamwork, constant communication and standardized protocols and processes also are integral. "All of this technology would mean little without the dedicated teams of people who care for patients," he says.
He also stressed the importance of standardizing monitors as much as possible so that each room has the same type of monitor. "The key aspect with monitors is trust," he says. "You have to know what it is telling you and how to respond. We find that by having as few vendors as possible, it makes it easier to gain comfort and trust with the devices."
Moving to the ICU
When patients leave the surgical table, they need to remain under constant surveillance. Today's monitors allow for