The patient presented to the hospital collapsed and unresponsive. He was a known diabetic patient, and was already undergoing treatment for his diabetes.
Signalment:
Species: Feline
Breed: Domestic Long Haired
Age: 14 years 3 months
Gender: Male (neutered)
Weight: 4.8 kg
History
The patient had previously been diagnosed with insulin dependent diabetes mellitus (IDDM). He had been confirmed as acromegalic (with a high insulin-like growth factor 1 concentration), and had also been noted to have a heart murmur, and International Renal Interest Society stage 2 chronic kidney disease (IRIS, 2013). He was found collapsed in the morning by his owner who, suspecting hyperglycaemia, administered a subcutaneous insulin glargine (Lantus, Sanofi Aventis) injection and presented him to the practice.
Presentation
The cat presented collapsed, comatose and hypothermic with a temperature of 32.2°C (reference range: 37.8–39.0°C), and constricted pupils. He had a gallop rhythm with a grade 1/6 systolic murmur and pulse deficits, although he had good pulse quality with a heart rate of 180 beats per minute (reference range: 140–220 bpm). He had no other abnormalities detected on physical examination with the veterinary surgeon (VS). Thoracic auscultation was clear with a respiratory rate of 28 breaths per minute (brpm) (reference range: 20–30 brpm), pink and tacky mucous membranes with a capillary refill time of 1–2 seconds (reference range: 1–2 seconds).
Initial plan and treatment
Blood glucose (BG) measurement from an ear prick sample with a patient-side glucometer (AlphaTRAK, Zoetis), gave a reading of ‘LO’. Zoetis Alpha trak manual defines ‘LO’ as a reading of <1.1 mmol/litre (Zoetis, 2008). The immediate concern was to address the cat's hypoglycaemia, considered to be the cause of his collapse and comatose state. An intravenous (IV) catheter was placed and he was administered 5 ml of 50% glucose (Hameln) IV diluted 1:1 with Hartmanns (Aquapharm 11) solution immediately. Thereafter he was placed onto a 2.5% glucose IV constant rate infusion (CRI) at 2 ml/kg/hour (glucose diluted in Hartmanns). IV glucose can cause phlebitis due to hypertonicity (Gamble, 2015), so care was taken to dilute it appropriately. Use of a central jugular catheter would have decreased the risk of phlebitis (Orpet and Welsh, 2011), however, this was not available at the time, therefore a peripheral cephalic catheter was used. A central line would have also taken time to place, increasing time to intervention, which was crucial. The patient was also warmed gradually in an incubator to reduce the risk of vasodilation caused by direct heat, such as a heat pad (Gamble, 2015), and subsequent hypoperfusion due to hypotension. Active warming was ceased at 37°C, and the patient stabilised himself to 38.2°C.
Progress
The patient became more responsive to noise and touch after dextrose administration; however, he then had a tonic clonic seizure. He was hyperglycaemic at the time of seizure; with a BG of 23.2 mmol/litre (reference range: 4.4-6.6 mmol/litre). He was administered 0.5 mg/kg diazepam (Hameln) IV to end the seizure activity, which was successful (Figure 1). Vite and Long (2007) recommend treatment of seizure activity lasting 2 minutes or more. A seizure pack had not been prepared for the patient initially, as seizure activity had not been anticipated. Once the patient had seizured once however, a pack was prepared with a vial of diazepam, syringes, saline flush and the exact dose requirement written on the pack. Primary assessment of the seizure patient should include respiratory, cardiovascular and central nervous system (CNS), with a focus on cessation of active convulsions (Powell, 2012).
Nursing considerations
There are many nursing considerations when caring for a patient in a hypoglycaemic crisis, beyond the scope of this paper, therefore three main considerations highlighted by his nursing care plan have been discussed: blood glucose; neurological observation; and physiotherapy.
Blood glucose
Monitoring this patient's BG levels was a primary concern (Figure 2). This was done using a species specific AlphaTRAK (Zoetis) handheld device (validated in a study by Zini et al, 2009) with a drop of blood achieved from ear prick testing. Ford and Lynch (2013) recommend the routine use of the lateral ear margin for BG testing in cats, specifying the use of the capillary and not the vein. A capillary sample is deemed sufficient, as the AlphaTRAK only requires a 0.3 µl sample, and an ear or paw pad sample is generally well tolerated (Ford and Lynch, 2013). Techniques have been recommended to maximise efficacy, such as warming the ear prior to sampling to dilate the vessel and applying a petroleum jelly. It is best to avoid the vein as a venous ear prick will traumatise the ear with haemorrhage and bruising more likely (Ford and Lynch, 2013). The validity of peripheral capillary BG testing however is questionable with a critically ill patient, as glucose extraction may be increased and tissue perfusion decreased (Rebel et al, 2012). A calibration sample was taken early on in the patient's care, by testing an ear prick sample and a cephalic sample and comparing the BG results; the results matched, therefore sampling was continued with the ear. Alternative methods are available for less invasive BG monitoring called flash glucose monitoring systems, with products such as the Freestyle Libre (Abbott Animal Health, UK). This technology uses interstitial glucose concentrations from a device placed on the neck, and has been validated in a study by Corradini et al (2016). This could be a consideration for future practice.
Schoeman (2012) defines hypoglycaemia as a reading below 3.5 mmol/litre and suggests this is a common complication of IDDM. It is a life-threatening condition which requires rapid treatment to prevent lasting neuronal damage. Electroencephalograph would be required to fully assess neuronal function and assess the hypoglycaemic effect on the brain (Jensen et al, 2014), however this was not available. Physical neurological observations were used to establish whether neuronal damage had occurred. This included mentation, motor activity, respiratory pattern, pupil size and reactivity and oculocephalic movement, as per Knipe's basic assessment (2015).
Regular BG readings on the patient revealed an asymptomatic hypoglycaemic episode after he had been stabilised for 48 hours, taken off his dextrose CRI and before restarting his insulin. With a reading of ‘LO’, and a second confirmation reading of 1.9 mmol/litre, the patient was offered food which he ate readily. Retrospectively, the patient may have benefitted from a further bolus of IV dextrose to treat the severe hypoglycaemia. Although this was not a decision to be made by the nursing team, the VS was made aware of the hypoglycaemia and the nursing intervention, to thereafter advise on an appropriate treatment plan. An alternative to IV administration would have been glucose administered directly onto the mucous membranes, such as Glucogel (BBI Healthcare), however, as the patient was asymptomatic the decision to feed was successful and the BG increased to 3.8 mmol/litre within the hour and 4.8 mmol/litre within 2 hours post prandially. Feeding the conscious hypoglycaemic patient is an approach recommended by Taylor (2013), although no parameters are specified to differentiate if a more direct glucose administration route would be indicated. Having a high/low glucose range on the patient's hospital chart and specific instructions from the VS as to what action to take in each circumstance, would have eradicated the risk of prolonged hypoglycaemia. This is a technique recommended by Humm and Kellett-Gregory (2016). With clear instructions the patient could have had a more prompt, direct administration of glucose with readings below 3.5 mmol/litre (a parameter established from retrospective conversation with the VS).
Neurological observations
As the patient presented comatose, monitoring for improvements in mentation were vital in assessing the adequacy of the treatments being administered. Mentation observations can be subjective and can vary in judgement from person to person. The recorded observations for this patient were that he was improving in responsiveness; however these were subjective judgements which were not standardised. A version of the modified Glasgow Coma Scale (MGCS) (Lorenz et al, 2011) may have been more appropriate to establish universal standardisation of observations. The scale was originally adapted for use with dogs (Platt et al, 2001), but has also been used with cats (Grohmann et al, 2012). This would have allowed for more objective, rather than subjective, analysis of response to treatment. Niessen and colleagues (2012) recognise that acromegalic cats may have CNS signs, such as plantigrade stance, as a symptom of the acromegalic condition, which may hinder monitoring neurological response to therapy, but should not affect using the MGCS.
A study into hypoglycaemia in rats describes cerebral adaptive mechanisms to acute hypoglycaemia such as significant reductions in cerebral glucose utilisation, less so to chronic exposure (Jensen et al, 2014). From the glucose curves demonstrated during the patient's hospitalisation period, he appeared to be suffering with frequent exposure to hypoglycaemic episodes with little or no clinical signs. The results of the Jensen et al (2014) study could explain that chronic hypoglycaemia causes a hypoglycaemic insensitivity. This is further explained by Schoeman (2012) as a tolerance of low plasma glucose levels without stimulation of normal compensatory mechanisms. A study by Whitley et al (1997) into insulin overdose also revealed 10% of cats were asymptomatic during a hypoglycaemic episode. Orpet and Welsh (2011) describe hypoglycaemic symptoms as lethargy, apparent blindness, ataxia, collapse, convulsions, coma and death. As the patient recovered from his coma and seizures, monitoring neurological signs gave an indirect indication of BG levels between BG readings, as a deterioration in mentation would suggest hypoglycaemia, and this lead to blood sampling. Observations were performed with consideration of the likelihood of his hypoglycaemic insensitivity, and asymptomatic hypoglycaemic episodes. This made close objective monitoring all the more important, as symptoms may only have been expressed at a crisis level, a valid indication for thorough behavioural assessment on his hospital charts (Haskey, 2015). The seizure patient also has specific parameters at risk of elevation: temperature, heart rate, respiratory rate, hyperaemic mucous membranes and a rapid capillary refill time (Powell, 2012). Powell (2012) also advises observation of cranial nerve function, which was monitored by his ability to recognise food smells, monitoring his sight function within the kennel, and his responses to vocal stimulus.
Physiotherapy
Physiotherapy was started once the seizure activity was controlled and the BG level stabilised. Savino and colleagues (2007) note the indication of physiotherapy in the recumbent patient to maintain joint mobility, although mention that care should be taken in an unstable critical patient. For this reason, physiotherapy should always be carried out in consultation with the VS (Howarth et al, 2007). The patient had only been non-ambulatory for less than 24 hours, but he had some muscular atrophy from reduced activity levels prior to the hypoglycaemic episode, and it was considered that he would benefit from encouraged venous and lymph return in the periphery. Haskey (2015) discusses the indications for physiotherapy in critical care nursing to reduce muscular atrophy, promote blood and lymph flow and keep the patient supple.
His sessions were started with effleurage; a massage technique involving firm, even pressure moving proximally towards the heart or lymph node thus reducing oedema (Cartlidge, 2014). With the muscles warmed and prepared with effleurage, his physiotherapy progressed to passive range of motion (PROM). Passive joint movements through the natural range of motion (ROM) help to maintain the ROM, which can reduce with a lack of movement (Cartlidge, 2014). PROM also maintains joint health by distributing synovial fluid. Cartlidge (2014) recommends physiotherapy two to three times daily in the recumbent patient. As the patient began to recover and regain mobility, active movement was facilitated. The patient had plantigrade stance, which can be symptomatic of acromegaly (Greco, 2012; Niessen et al, 2012). His physiotherapy sessions were continued until he could stand and maintain mobility unaided for longer periods.
The nursing process
The nursing process is a constant cycle of assessment, planning, intervention and evaluation (Orpet and Welsh, 2011; Haskey, 2015). It is a process appropriately suited to a patient recovering from a condition like hypoglycaemic collapse, with clinical parameters being constantly assessed and the effects of nursing interventions and drug interventions being evaluated with the view to planning a continuation or change in approach as necessary. Jordan and Brainard (2011/12) recommend continual reassessment in the emergency setting, specifically for patients demonstrating neurological concerns as any rapid changes in mentation may indicate a deterioration requiring immediate attention. The nursing process also allows for a nursing care plan, like the Orpet and Jeffrey ability model (Orpet and Welsh, 2011), to identify areas requiring intervention, and can be used to tailor the nursing care appropriately. Using a framework like this, the nursing care for this patient was targeted not only to correcting his hypoglycaemia safely, but also reducing the risks associated with immobility, for example lung atelectasis. This was achieved by turning him every 4 hours while immobile (Haskey, 2015), carrying out physiotherapy and providing padded bedding as he was recumbent and at high risk of decubitus ulcers (Savino et al, 2007). The care plan also ensured the patient was kept clean by establishing that he was at an increased risk of urine scalding, and prompted close observation of nutritional requirement by monitoring the time span of anorexia. As the patient was also acromegalic, he was at an increased risk of pulmonary oedema and pleural effusion with growth hormone induced heart failure (Niessen et al, 2012), which could be exacerbated by his collapsed condition. This prompted close observations on cardiovascular and respiratory function, including frequent thoracic auscultation, which revealed no changes to his heart murmer. Altered mentation also increased the patient's risk of aspiration due to a potentially suppressed gag reflex. To reduce this risk the patient was positioned with his head and chest elevated above his hind-quarters, with oral care administered keeping the mouth clear of oral secretions which could be aspirated.
Frequent blood sampling is a difficult task to manage in critical care nursing, with regard to balancing patient comfort and health. Frequent ear or foot pricking is uncomfortable for the patient. The benefit of this technique, however, ensures minimal blood loss for the patient. The alternative for this patient would have been to sample from his peripheral intravenous catheter, however this would have involved losing at least 1 ml of blood for each sample, as the crystalloid with dextrose infusion would contaminate the sample. With frequent sampling, this would have caused unethical and unnecessarily compromising blood loss. A study performed by Lynch et al (2015) investigated hospital acquired anaemia, and discovered associations between frequent blood sampling and anaemia in both dogs and cats, with a higher prevalence in cats. A sensible alternative to either of these options would have been placement of a central venous catheter, allowing the sampling process to include removal of saline contaminated blood after flushing, then replacement after a small sample had been taken (Savino et al, 2007). This technique would also reduce the risk of catheter contamination associated with frequently disconnecting the line, with the use of a multi-lumen catheter. Central venous access was unavailable at the time due to constraints including patient stability, therefore the patient had a topical local anaesthetic cream (EMLA, Astra Zeneca) placed on his ears to minimise the trauma, a technique supported by Gamble (2015). The nursing care plan and nursing process enabled the nursing team to intervene promptly with the topical anaesthetic when the patient began showing signs of discomfort, as his levels of consciousness improved.
Conclusion
The patient was treated appropriately and successfully, however there are recommendations for future practice. Considering other available techniques, such as the use of central venous catheters, could improve patient welfare and the accuracy of BG results. Better preparation with the patient's hospital charts, for example high and low notification values, could have improved the response time in the crisis situation and eased communication issues.
Hypoglycaemia in diabetic cats due to insulin overdose is recognised as generally being due to poor owner education and understanding (Gamble, 2015). Therefore once the patient was stable enough for discharge from hospital, with a revised dose of glargine, emphasis was made on owner understanding of diabetic crisis monitoring.
KEY POINTS
- Consider patient welfare when undertaking frequent blood glucose testing.
- Asymptomatic hypoglycaemia may be a complication in cats, and acromegaly can further confuse neurological assessment.
- Use monitoring sheets with clear guidelines for accurate assessment and prompt intervention.
- Use the nursing process to constantly evaluate your patient care, taking into consideration condition, species and individual patient traits to tailor nursing care to the requirements of each patient.