An unusual cause of patient pain during regional anaesthesia.
A 60-year-old ASA II female had elective left total knee replacement under combined spinal epidural anaesthesia (CSE). An 18 gauge intravenous (IV) cannula was placed in her left (non-dominant) arm, over the dorsum aspect of hand, at first attempt and 500 ml of Ringer's lactate solution given. Using aseptic precautions a CSE was performed with the patient in the sitting position.
Once supine after CSE, she was sedated with IV midazolam 0.5 mg + 0.5 mg. The Ringer's lactate infusion rate was increased to compensate for a fall in blood pressure and the vital signs, including blood pressure, were monitored every minute for the next 15 minutes. During this period the patient started complaining of pain in the left arm at the site of cannulation despite there being no obvious swelling or redness at the site. The patient was reassured but she became increasingly restless. Mini Bier's block was given by injecting IV lignocaine 60 mg (3 ml of 2% Xylocard) IV but that too achieved only transient pain relief.
The decision to establish a fresh IV cannulation was taken, so the Ringer's lactate infusion was stopped. Unexpectedly, the patient no longer complained of pain. Meanwhile we noted that the skin over the IV site was unduly warm, so the IV fluid bag was disconnected from its IV tubing and the temperature of the fluid was checked. The temperature probe showed a fluid temperature of 45[degrees]C. Fresh Ringer's lactate that had been stored at ambient temperature was then started without patient discomfort and a diagnosis of 'thermal pain' was made.
This case highlights the fact that most hospitals in developing countries use pre-warmed IV fluids because of a lack of availability of other more expensive methods of fluid warming. Warming of IV fluids is important because if one litre of crystalloid at ambient temperature or one unit of refrigerated blood is administered at a peripheral site the mean body temperature decreases by 0.25[degrees]C in adults (1-3) and patients under regional anaesthesia are particularly prone to hypothermia.
The temperature at which this pre-warmed IV fluid is transfused cannot be determined because of lack of objective measurement, with the potential for accidental transfusion of hot fluid as in this case. Given that the temperature inside the operating theatre is 18 to 20[degrees]C, warm IV fluid is often used to prevent patient hypothermia, which justifies use of some objective method to quantify the fluid temperature.
In the literature, the maximum recommended temperature of IV fluid is 43[degrees]C (4,5).
This case highlights that over warmed IV fluid can be an unusual cause of pain and possible thermal injury. This event was detected in this case only because the patient was able to voice her symptoms. It is possible there may be a large number of patients who experience discomfort under general anaesthesia and that this is only reflected by autonomic nervous system or Bispectral index changes. We feel that:
1. An objective method should be used to quantify the temperature of all IV infusates.
2. Although the maximum recommended temperature of IV infusate is 43[degrees]C, it is probably an arbitrary figure and it needs to be ascertained whether a difference of greater than 6[degrees]C from normal body temperature is perceived as too warm/cold and thus painful.
3. As with other forms of pain, thermal pain threshold will also vary from person to person, and thus in any individual receiving pre-warmed fluids and complaining of pain around the IV site (or showing unusual responses during general anaesthesia), a suspicion of thermal pain should also be entertained.
4. Importance should be placed on other methods to prevent hypothermia, for example covering of exposed skin and use of forced warm air blankets.
New Delhi, India
(1.) Werlhof V. Hotline fluid warming fails to maintain normothermia. Anesthesiology 1996; 84:1520-1521.
(2.) Iseron KV, Huestis DW. Blood warming; current application and techniques. Transfusion 1991; 31:558-571.
(3.) Marks R, Minty B, White D. Warming blood before transfusion. Anaesthesia 1985; 40:541-544.
(4.) Anonymous. Limiting temperature settings on blanket and solution warming cabinets can prevent patient burns. Health Devices Alerts 2005; 29:1-3.
(5.) Dorsch and Dorsch. Temperature control equipment. In: Understanding Anesthesia Equipment, 5th ed. Philadelphia: Lippincott William & Wilkins 2008, p.884-904.
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|Author:||Kumar, R.; Kumar, S.; Bharti, M.; Luckwal, M.|
|Publication:||Anaesthesia and Intensive Care|
|Article Type:||Clinical report|
|Date:||Jan 1, 2009|
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