Monitoring the patient under anaesthesia in practice

No single number describes an anaesthetised patient: safety comes from cross checking several parameters, some instrumental and some clinical. The monitor helps, but it does not replace a hand on the pulse and an eye on the mucous membranes. The person monitoring holds both readings together and knows that, when they diverge, the clinical picture is checked before the number is trusted.

• Depth of anaesthesia: judged by reflexes, jaw tone, eye position and response to stimulus, not only by the gas percentage.
• Heart rate and rhythm: from auscultation, peripheral pulse and the electrocardiogram, which shows arrhythmias the ear misses.
• Blood pressure: the parameter that falls first in many cases of hypotension, often before other signs appear.
• Oxygenation and ventilation: pulse oximetry and, where available, capnography, which flags airway or breathing problems early.
• Temperature: hypothermia is the most frequent and most underrated complication, above all in small patients and long procedures.

The commonest organisational mistake is to give monitoring to the same person performing the procedure and ask them to glance over now and then. It does not work: the operator is focused on the surgical field and the trends slip past. Monitoring is a task in its own right, with one person responsible from induction to recovery.

• One person follows the patient and the sheet continuously, with no other task pulling attention away from monitoring.
• The operator flags critical moments in advance, for example a traction or a manoeuvre that may stimulate or drop pressure.
• Roles and threshold values are agreed before induction, not improvised when something changes.
• The person monitoring has the authority to call out when a parameter leaves its limits, and is listened to.

The anaesthetic sheet is not paperwork: it is the tool that makes trends visible. A single value says little, three values in a row show a direction. The cadence depends on the phase and the patient's stability, but the principle is that the more critical the moment, the denser the recording.

Record the events too, not only the numbers: the time of every drug given, the start and end of the procedure, every change of plane and every corrective intervention with its time. A sheet made only of values with no context does not let you understand, later, why the pressure fell in that particular minute.

The strength of continuous monitoring is catching the drift before the emergency. Here is a check sequence for when a parameter starts moving the wrong way, to be adapted to the anaesthetist's guidance.

1. 1

   Verify the reading against the patient

   Before reacting, confirm the abnormal value is real: probe well placed, pressure cuff of the right size, patient not lying on the sensor. Telling artefact from problem avoids needless interventions.

2. 2

   Look at the trend, not the single number

   Compare with the previous readings on the sheet. Pressure falling steadily over three readings is a different signal from one isolated low value.

3. 3

   Reassess the depth of the plane

   Many changes come from a plane that is too deep. Check reflexes and tone, and tell the anaesthetist if the patient is deeper than the phase requires.

4. 4

   Call out and propose

   State the parameter, the value, the trend and your hypothesis. Structured communication speeds the decision more than a generic alarm.

5. 5

   Record the intervention and the response

   Write what was done, at what time, and how the patient responded over the following minutes. It is the only way to know whether the correction worked and to learn from the case.

6. 6

   Do not drop your guard at recovery

   Many complications arrive after the procedure ends, when attention wanes. Keep monitoring until the patient has recovered reflexes, spontaneous breathing and temperature.