ANAESTHESIA AND PATIENT MONITORING


However, the AAGBI adds that some patients will require additional monitoring, for example: intravascular pressures, cardiac output, biochemical or haematological variables – depending on patient and surgical factors. The use of additional monitoring is at the discretion of the anaesthetist, however.


Pulse oximetry and capnography


Capnography (the monitoring of carbon dioxide in the breath) is used to monitor patients’ breathing while they are asleep or sedated. Both the American Society of Anesthesiologists (ASA) and Association of Anaesthetists of Great Britain and Ireland (AAGBI) require capnography to be used to monitor ventilation during moderate to heavy sedation. Following new research, the AAGBI’s 2016 guidance called for “all hospitals to work towards using capnography for all anaesthetist-led sedation to improve patient safety.”1


Death and anoxic brain injury from unrecognised postoperative respiratory depression is a serious concern for patient safety and has been the subject of a number of studies. In 2017, a systematic review and meta-analysis by Lam et al3


looked at the


evidence for continuous pulse oximetry and capnography monitoring for post-operative respiratory depression and adverse events. The objective of this study was to review the current state of knowledge on the effectiveness of continuous pulse oximetry versus routine nursing care and the effectiveness of continuous capnography monitoring – with or without pulse oximetry – for detecting post-operative respiratory depression and preventing postoperative adverse events in the surgical ward. In total, nine studies (four examining continuous pulse oximetry and five examining continuous capnography) were included in the systematic review. In the literature on continuous pulse oximetry, one randomised controlled trial showed no difference in ICU transfers (6.7% vs 8.5%; P = .33) or mortality (2.3% vs 2.2%). A prospective historical controlled trial demonstrated a significant reduction in ICU transfers (5.6-1.2 per 1000 patient days; P = .01) and rescue team activation (3.4-1.2 per 1000 patient days; P = .02) when continuous pulse oximetry was used. Overall, comparing the continuous pulse oximetry group versus the standard monitoring group, there was 34% risk reduction in ICU transfer (P = .06) and odds of recognising desaturation (oxygen saturation [SpO2


] <90% >1 hour) was


15 times higher (P < .00001). Pooled data from three capnography studies showed that continuous capnography group identified 8.6% more post-operative respiratory depression events versus pulse oximetry monitoring group (CO2 group versus SpO2


group: 11.5% vs 2.8%; P < .00001).


The odds of recognising post-operative respiratory depression was almost six times


higher in the capnography versus the pulse oximetry group (odds ratio: 5.83, 95% confidence interval, 3.54-9.63; P < .00001). No studies examined the impact of continuous capnography on reducing rescue team activation, ICU transfers, or mortality. The authors concluded that the use of continuous pulse oximetry on the surgical ward is associated with significant improvement in the detection of oxygen desaturation versus intermittent nursing spot- checks. There is a trend toward less ICU transfers with continuous pulse oximetry versus standard monitoring. They added that the evidence on whether the detection of oxygen desaturation leads to less rescue team activation and mortality is inconclusive. Calling for improved education regarding monitoring, the authors further stated that capnography provides an early warning of post-operative respiratory depression before oxygen desaturation, especially when supplemental oxygen is administered.


High risk patients and high risk surgery


Blood pressure is a basic vital sign and is often used to guide therapeutic interventions, as part of the standard of care for anaesthesia and perioperative management. Accurate blood pressure readings are critical for monitoring the depth of anaesthesia and for ensuring the safety of the patient while they are undergoing surgery. Blood pressure measurements are usually obtained intermittently and non-invasively using oscillometry (upper arm cuff method) or continuously and invasively with an arterial catheter.4


However, for higher risk patients, or high-risk surgery, even a short period of hypotension (ie: low blood pressure) can have catastrophic effects on outcomes and mortality.


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“A number of studies have shown that haemodynamic monitoring is associated with improved outcomes, particularly in high-risk procedures such as colorectal, vascular, transplant and cardiac surgery – and even caesarean section,” commented Matthew Sassone, CEO at LiDCO. With high-risk surgery or high-risk patients, there is a need for advanced monitoring. So, what exactly does haemodynamic monitoring offer in addition to standard vital signs monitoring? “Haemodynamic monitoring ‘lifts the veil’ on blood pressure. There may be a variety of reasons for a patient to have low blood pressure and haemodynamic monitoring takes away the guesswork, for example, whether the patient is fluid responsive,” said Sassone. “Haemodynamic monitoring can be used as part of an Enhanced Recovery After Surgery (ERAS) protocol. Theatre teams evaluate the patient’s pre-load, after-load and contractility. Based on these factors, they are able to determine whether the patient needs fluids or vasoactive drugs,” he continued.


Enhanced recovery after surgery


LiDCO explains that the concept of ERAS was first established by Henrik Kehlet and his team in Denmark – who, through a multidisciplinary approach across the perioperative pathway, was able to have a dramatic effect on reducing patients’ length of stay in open colectomies. This included the removal of bowel prep, the avoidance of fasting, carbohydrate loading pre-operatively and early mobilisation, which are still key elements of the ERAS pathway that can be seen today.


The scope of the ERAS programme has since expanded to include a wide range of other pre-operative, anaesthetic, surgical and post-operative practices with a goal of reducing complications and length of stay.


SEPTEMBER 2018


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