Dr. Heena D. PahujaAssociate Professor,
Department of anaesthesiology
N.K.P. Salve Institute of Medical sciences and Research Centre and LMH
“The Oxford English Dictionary defines Monitor as something that reminds or gives warning.”
Another definition is “an instrument used to measure continuously or at intervals, a condition that must be kept within prescribed limits.” Monitors are “unsleeping eyes” that allow us to ‘see the invisible’ so that the user can recognise the event early and act appropriately on what is seen.
Patient monitoring has been a key aspect of anaesthesiology since its beginning as a medical speciality. As the speciality has grown more sophisticated and complex, so have the monitors and the data they present.
On January 28, 1848, less than 2 years after the first public demonstration of anaesthesia, 15-year-old Hannah Greener while undergoing excision of ingrown toenail, died as a result of chloroform administration. The account of this first known anaesthesia related mortality is found in Robinson’s Victory Over Pain. This first documented death led the early practitioners to highlight the importance of monitoring simple vital signs-respiration, pulse, and skin colour. Since that time,patient’s safety concerns led to the development of monitoring modalities and standards in perioperative monitoring practice.
Classically, simple clinical observations like hand on pulse, an ear to listen to breath and heart sounds (stethoscope) and an eye to see chest movements and the patient’s colour were used to get the information about patient’s status during anaesthesia.
Arthur Guedel published his eye signs of ether anaesthesia in American Journal of Surgery in 1937. John Snow mentioned the customary monitoring under anaesthesia to include respiration- depth and frequency, muscle movements, skin colour, and stages of excitation or sedation. Dr Joseph Thomas Clover, the leading clinical anesthetist in England strongly advised that the pulse be continuously observed during anaesthesia and that irregularities should alert the anesthetist to discontinue the anesthetic.
Medical students E.Amory Codman(1869-1940) and Harvey Cushing ( 1869-1939) developed the first anaesthesia record using observed respiratory rate and palpated pulse rate. By 1901, Cushing added blood pressure measurement by Riva-Rocci’s sphygmomanometry. By 1903, respiratory rate and heart rate was auscultated by precordial stethoscope. In1950, concept of Post-Anesthesia Care Unit (PACU) & Intensive Care Unit (ICU) was introduced. The first landmark advancement in monitoring technology occurred in 1980’s with the advent of pulse oximetry in clinical practice by Dr William New, a Stanford anaesthesiologist.Capnography (1991) proved a rapid and reliable method to detect life-threatening conditions e.g., malposition of tracheal tubes, unsuspected ventilatory failure.
Newer advanced monitoring techniques include depth of anaesthesia monitoring (Auditory evoked potential AEP monitor, Patient state analyzer PSA-4000 monitors, cerebral state monitor CSM and entropy), advanced hemodynamic monitoring (goal-directed fluid therapy, transesophageal echocardiography TOE), neuromuscular monitoring (NMM), Neurological monitoring, coagulation monitoring (TEG, ROTEM), improved alarm systems and closed loop drug delivery system (McSleepy). Newer monitors also incorporate software like anaesthesia information systems which has completely replaced the paper recording system. Computer assisted monitoring has resulted in automation of clinical monitoring and the collection of a lot of data which can be used as a permanent record and for the purpose of audit and research.
The monitoring devices of the future will have an additional advantage that it would enable automated correction of physiological abnormalities simultaneously eg Target controlled infusion devices (TCI) or Computer -controlled drug delivery system for various anaesthetic agents or newer ventilators that can automatically adjust the ventilator settings by monitoring lung mechanics. Artificial intelligence, Augmented Reality and Robotic anaesthesia are the topic of future research. The new monitoring techniques can potentially reduce the element of human error.
The minimum mandatory monitoring by American Society of Anaesthesiologist (ASA) includes ECG, NIBP, pulse oximetry, and capnography while a nerve stimulator and temperature monitor should be immediately available.Additional monitoring like continuous invasive arterial blood pressure, central venous pressure(CVP)monitoring, TOE, NMM etc., may be required as per the indication.
Monitoring is important to prevent anaesthesia complications. Monitoring instruments are not a substitute for careful clinical observation. We, being anesthesiologists, must be aware of the recent developments in monitoring.
Monitoring systems can never reduce the importance of training and clinical skill. Infact, intense training is required in correct use and interpretation of monitors. Sophisticated monitors available only to aid, not to be fully dependent on them. To conclude, new and improved monitoring techniques have undoubtedly led to dramatic changes in anaesthesia practice but always remember that we must monitor the monitors. Anaesthetist’s vigilance is the best monitor in providing safe anaesthesia and high-quality care.
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- Recommendations for standards of monitoring during anaesthesia and recovery Anaesthesia 2021,76,1212-1223.