CHAPTER 14 POSTOPERATIVE AND OBSTETRIC PATIENTS
PERI-OPERATIVE OPTIMIZATION
There is ongoing interest in so-called ‘peri-operative optimization’ of cardiovascular variables in order to minimize the physiological disturbances and stress responses caused by surgery. In some centres, patients may be admitted to ICU or HDU preoperatively, invasive haemodynamic monitoring instituted, and fluids and inotropes used judiciously to optimize stroke volume. The process is similar to that described previously in Chapter 4. (See Optimization of cardiovascular system, p. 78.) There is some evidence that peri-operative optimization reduces peri-operative complications and reduces the need for unplanned ICU admission (or length of ICU stay) after major surgery.
This is a complex area. Some patients with ischaemic heart disease, for example, may benefit from β-blockade to protect the myocardium, rather than being driven with inotropes. Seek advice and follow local protocols.STRESS RESPONSE TO SURGERY AND CRITICAL ILLNESS
Hormonal responses
There is a generalized increase in sympathetic activity and the adrenal secretion of catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine) is increased. These have predictable cardiovascular effects. Adrenaline also has metabolic effects, most notably hyperglycaemia. Increased production of renin from the kidney leads to activation of the renin–angiotensin–aldosterone pathway. Angiotensin II is a potent vasoconstrictor that increases blood pressure, while aldosterone increases renal salt and water retention.
POSTOPERATIVE ANALGESIA
Patient-controlled analgesia (PCAS)
These techniques are extensively used to provide analgesia particularly in postoperative patients. Typically the patient will be established on such a device prior to transfer to a general ward. Although not intended for operation by nurses, they have been used safely and conveniently in this way in an ICU setting.
Care should be taken in setting devices up; a dedicated intravenous catheter or non-return valve should be used. There have been a number of problems due to excessive background dosing, surges of morphine on unblocking i.v. lines, and siphoning of contents under gravity from syringes. Avoid background infusions if possible. Position syringe drivers below the level of the patient to avoid siphoning, and use antireflux valves on giving sets. A typical PCAS regimen is shown in Box 14.1.
Regional blockade
Detailed description of epidural techniques is beyond the scope of this book. When a patient is admitted with an epidural catheter in situ, you should make sure that you confirm the analgesic regimen with the responsible anaesthetist. Local anaesthetic and opioid drugs may be used alone or in combination. If opioid drugs are administered, additional systemic opioids should be administered with care because of the risk of respiratory depression. Typical regimens are shown in Table 14.1.
TABLE 14.1 Typical postoperative epidural infusion regimens
| Agent | Rate | Comment |
|---|---|---|
| Bupivicaine 0.1–0.15% | 8–15 mL / h | |
| Bupivicaine 0.1–0.15%plus fentanyl 2 μg / mL | 8–15 mL / h | No concomitant systemicopioids to be given |
Do not prescribe or administer epidural drugs if you are not familiar with epidural techniques. Seek help.Complications of epidural blockade
The potential complications of epidural blockade are shown in Box 14.2.
Hypotension usually responds to fluid loading (500 mL colloid) and reducing the rate of epidural infusion. If significant hypotension develops, reduce or stop infusion and consider the use of a vasopressor infusion.
At the doses used, the addition of opioids to epidural infusion may significantly improve analgesia without significant increase in the side-effect profile. Nausea and itching may be helped by low-dose naloxone without loss of analgesia. CNS depression may require ventilation.
Box 14.2 Complications of epidural blockade
| Local anaesthetics | Opioids |
|---|---|
| Potential local anaesthetic toxicity | Itching |
| Hypotension (sympathetic blockade) | CNS depression including apnoea |
| Muscle weakness (including respiration) | Urinary retention |
| Bradycardia (block > T4 level) | Nausea and vomiting |
| Urine retention | |
| Complete or high spinal block (cardiovascular collapse, respiratory paralysis, loss of consciousness) |
The use low concentration local anaesthetic agents in epidurals is intended to provide adequate analgesia whilst minimizing the risk of significant motor blockade. If profound motor block develops in a patient with a postoperative epidural, suspect possible spinal cord compression. Seek urgent advice.
Do not give drugs by the intrathecal route unless you have been specifically trained to do so. There have been a number of cases where incorrect drugs administered by this route have caused catastrophic and permanent neurological damage and death.Common postoperative problems
Problems in the immediate postoperative period may include the effects of prolonged surgery, massive fluid / blood loss, sepsis, tissue ischaemia / reperfusion, delayed recovery from anaesthesia and the effects of the stress response to surgery and trauma.
Delayed recovery of consciousness
The causes of delayed recovery of consciousness following anaesthesia are often multifactorial. It may be impossible to determine initially which is the predominant problem. Factors that may contribute are shown in Box 14.3.
Box 14.3 Factors that may contribute to delayed recovery from anaesthesia
Residual effects of anaesthetic drugs
Prolonged neuromuscular block
Muscle relaxants are used extensively in anaesthesia to facilitate tracheal intubation, provide relaxation for surgical procedures, and allow lighter planes of general anaesthesia. In the ICU, patients are usually left to clear muscle relaxants without use of reversal agents. Following anaesthesia, the recovery of neuromuscular function is often hastened by the use of anticholinesterase drugs (e.g. neostigmine). These increase the concentration of acetylcholine at the neuromuscular junction and reverse the effects of non-depolarizing neuromuscular blocking drugs (competitive antagonists at the acetylcholine receptor). They are used in combination with glycopyrrolate, which reduces the undesirable (muscarinic) effects of acetylcholine. Typical doses are:
Problems relating to residual neuromuscular blockade have become less common since the introduction of newer shorter-acting drugs such as atracurium. Occasionally, however, there may be delayed recovery of neuromuscular function. Factors that may contribute to this are shown in Box 14.4.
