The Unmeasured Discomfort: Shivering in PACU and The Use of a Bedside Shivering Assessment Scale
Submitted by Cheyenne D. Bonja BSN, ADN, RN, CPAN
Tags: anesthesia Hypothermia nurse training Post-Anesthesia Care Surgical Recovery
Postoperative shivering (PS) is commonly seen in the Post-Anesthesia Care Unit (PACU) and can be quite distressing not only for the patients but also for the nurses trying to manage these symptoms. Patients are often uncomfortable, frightened, disoriented, and experiencing pain. A Bedside Shivering Assessment Scale can be incorporated into the documentation alongside the standard vital signs, Aldrete score, and RASS score. Shivering can cause an increase in oxygen consumption which can lead to hypoxia, catecholamine release that increases stress response. This can be observed in the vital signs, showing an elevated heart rate and blood pressure. Lastly, shivering is attributed to increased pain and discomfort. PS has been reported in PACU from 20%-70% of the time in general anesthesia. “Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different.” The hypothalamus is located in your brain and is responsible for regulating the body’s temperature. The cool conditions in the OR suites and post-op units, as well as anesthetics used during surgery, often induce hypothermia. Anesthesia affects thermoregulation in many ways, from disruption in the body’s hypothalamic set point that causes larger deviation in the “normal” temperature range, a decrease in cold-defense mechanisms, and muscle relaxants prevent involuntary muscle contractions, resulting in heat loss.
Shivering is an involuntary contraction of skeletal muscles to generate heat to increase body temperature. This is usually triggered by hypothermia but can be seen in normothermic patients in the perioperative area. Shivering is defined as “the fasciculation of the face, jaw, or head or muscle hyperactivity lasting longer than 15 seconds.” Shivering and hypothermia are common side effects of anesthesia. Some anesthesia medications, such as propofol, inhalants like Sevoflurane, Isoflurane, Halothane, and dexmedetomidine and opioids impair the hypothalamus thermoregulation function. This disruption causes the temperature to range wider than normal, resulting in a shivering response or skeletal muscles trying to generate heat. When assessing postoperative shivering, it is essential for nurses to assess all factors. The nurse must assess the patient’s temperature, pain assessment level, length of surgery, and knowledge of medications given by the anesthesiologist. Postoperative hypothermia is defined as a core temperature of 33°C (91.4°F) to 35°C (95.9°F). Pain and temperature signals are transmitted in a similar way, which is why perianesthesia nurses must be diligent in their patient assessment.
These nurses are trained in Phase I recovery and must be able to quickly identify the cause of why the patient is shivering and treat accordingly. This will help to promote comfort and pain control early in the immediate post-op period. In Phase I, the patients are transitioning from anesthesia commonly in Stage II or the emergence phase back to Stage I and recovery. These stages are when PS occurs, and patients may experience significant discomfort. Shivering can also cause stress on surgical incisions, increasing post-op pain especially in patients who underwent abdominal or OBGYN surgery. Patients experience an increase in oxygen consumption of anywhere from 300-400% and can lead to hypoxia. This may lead to patients needing supplemental oxygen via nasal or simple mask and can cause an increase in heart rate and blood pressure. With an elevation in blood pressure and possible need for supplemental oxygen, it can result in a decreased Aldrete score delaying the patient from moving to Phase II recovery. Perianesthesia nurses need to quickly assess the causes of shivering followed by the severity and ways to treat PS. The nurse can use a Bedside Shivering Assessment Scale (BSAS) to assess shivering by observation. 0: no shivering; 1: mild fasciculations of face and neck and artifact on ECG; 2: visible tremors in muscle groups; 3: gross activity involving the entire body. Along with this assessment the nurse will take the patients temperature and pain assessment. Nurses can employ various interventions to minimize discomfort, utilizing both pharmacological and non-pharmacological methods. “The ASA guidelines recommend force-air warming and meperidine as the treatment of choice for PS.” Nurses can use various methods of increasing body temperature by active and passive warming to bring patients back to normothermia if temperature is the cause of shivering. Active warming can be done by a bear hugger blanket or a warming gown that uses forced warm air to warm the patient.
Alternatively, the nurses can use passive warming by using warm blankets. Some studies suggest having force-air on the upper and lower extremities, however, what is best is still undetermined. In addition to warm air, the use of warmed IV fluids can be used to help minimize heat loss. If these interventions do not help shivering, nurses may have to use pharmacological treatment such as meperidine. Meperidine (Demerol) is the most common medication used to decrease and treat PS. Demerol acts on the central nervous system to suppress the body’s thermoregulation response and reduces the threshold that lowers the core body temperature, which triggers the brain to induce shivering. The common dose for intravenous administration is 12.5mg or 25mg.
A few other drugs have been shown to decrease PS, such as tramadol, fentanyl, clonidine, ketamine, and ondansetron; however, the effects are less than that of Demerol. There are a few considerations when administrating Demerol, such as it can cause increased risk of nausea and vomiting, respiratory depression, and should not be given to patients with a history of seizures. Perianesthesia nurses should implement the BSAS document section to evaluate the patients shivering level and can intervene quickly in the event of complications that can arise. Nurses need to be able to identify when to initiate active warming and when it is appropriate to consider giving medications for shivering. Shivering can cause increased oxygen consumption and pain, potentially delaying the administration of pain medications and overall comfort in the recovery room. Efforts to prevent and treat shivering will improve comfort, patient satisfaction, and decrease the risk of complications such as hypoxemia, pain, and distress.